Low Carb Diet Hunger Pangs

Low Carb Diet Hunger Pangs

For millions of people, it's the elusive Holy Grail: what IS the best way to shed the pounds – and, crucially, keep them off?

After all, it doesn't seem to make sense: there's really only one way to gain weight – by eating and drinking too much – yet, when it comes to losing a pound or two, the options seem endless.

New weight loss plans pop up every year, each one promising a magic bullet for our bodies and health.

Yet too many of us are familiar with the experience of initially losing weight on a diet , only to pile the pounds back on afterwards.

Now, after lockdown – when 40 per cent of the country gained at least half a stone thanks to disrupted routines and comfort eating – clear, easy-to-understand diet advice has never been more in demand.

Here registered nutritionist and personal trainer SARAH O'NEILL (sarahoneill.co.uk ) shares her no-nonsense guide to the most well-known diets around to help you decide which one is best for you.

HIGH PROTEIN/LOW CARB

Many fitness professionals advocate a high protein, low carbohydrate diet to help their clients lose weight and build muscle.

The theory is that carbs (fibre, starches and sugar) provide our quickest source of energy so reducing them forces the body to tap into stored fat for fuel instead.

The NHS Eatwell Guide recommends that we eat around 55 per cent carbohydrate, 35 per cent fat and 10 per cent protein per day. But a high protein diet is approximately 30 per cent carbohydrate, 40 per cent protein and 30 per cent fat.

'These diets typically work well for weight loss in the short term but tend to plateau after a while,' says registered associate nutritionist Rosie Long, who says the initial changes in the body can be from losing 'water weight'.

BEST FOR:A lower carb diet can help manage type 2 diabetes, and any diet that encourages the reduction in high GI (glycaemic index) carbs such as cakes, biscuits, white pasta and white bread – these can cause a sugar spike and crash – is beneficial for all.

NOT FOR YOU IF: Excess protein can put strain on the kidneys, so this should be avoided by anyone with any risk factors for kidney disease. Vegetarians and vegans may struggle as veggie sources of protein such as grains, beans and pulses contain carbs.

Miss Long says: 'Our bodies need carbohydrates to function properly. Diets that are low in carbs are typically low in fibre, have limits on fruit and vegetable consumption and can be high in saturated fat and include more red and processed meat.'

INTERMITTENT FASTING

Intermittent fasting became a buzz phrase in 2013 with Dr Michael Mosley's book, The Fast Diet, which promoted the 5:2 diet. In essence, it involves eating normally for five days of the week and 'fasting' – keeping to 800 calories – on the other two.

It remains popular and participants can expect to lose around 1lb a week. Studies also show that, as well as weight loss, it can stabilise blood sugar levels, suppress inflammation, decrease blood pressure and cholesterol levels and improve cognitive function.

Potential side-effects include the detrimental effects of fasting including constipation, headaches and hunger pangs.

There is also a daily version, the 16:8, with calory intake confined to an eight-hour period, such as 10am to 6pm or noon to 8pm, and the 'fast' takes place over the remaining 16 hours. This can be easier to sustain long-term and can be a helpful way of eliminating bad habits such as post-dinner sofa grazing.

BEST FOR:The 5:2 offers very clear 'on' and 'off' periods. Many people find intermittent fasting easy to follow long term or to use as a 'reset' tool when positive dietary habits slip. It can also teach the body 'real hunger' rather than eating out of habit.

NOT FOR YOU IF:It helps to have a consistent routine and may be hard if you have to get up very early or work long hours or shifts because this could leave you running on empty. It's also not recommended for people with diabetes.

'The diet won't work for weight loss if there isn't a calorie deficit overall,' notes Miss Long. 'If someone makes up for the fasting day by eating double as much on the non-fasting day then there would be no effect.'

THE KETOGENIC DIET

The ketogenic diet, a controversial high fat, low carb plan, has social media to thank for its recent popularity. Posts tagged with '#keto' have been seen an unimaginable six billion times on TikTok.

The aim is to force the body into 'ketosis', when it is fuelled by fat instead of carbohydrates. Replacing carbs with fat causes molecules called ketones to build up. The body then burns them for fuel instead of glucose from carbohydrates.

Fat makes up a hefty 70 to 75 per cent of daily intake with just five to 10 per cent of carbs. Recommended foods include bacon, cheese, eggs, butter and avocado. Fruit, grains, root vegetables and legumes are off the menu, but low carb vegetables such as greens are allowed.

The side-effects can be unpleasant and include dehydration, headaches, bad breath (ketones have an almondy odour), fatigue, nausea and constipation.

BEST FOR:The ketogenic diet was originally developed as a therapeutic diet to treat severe epilepsy in children. However, studies show it can lead to weight loss, reduced blood sugar levels and insulin resistance in adults. If you enjoy fatty foods this diet will appeal and, unlike other diets, it feels 'naughty'.

NOT FOR YOU IF:Steer clear ifyou have type 1 diabetics, pancreatic disease, liver conditions, thyroid problems, eating disorders (or a history of them), gallbladder disease, or your gallbladder has been removed, or a family history of kidney issues or disease.

The high fat nature of this diet is debatable, and because it doesn't follow the fundamentals of healthy eating (consuming fruit, vegetables and wholegrains), it potentially increases the risk of heart disease and is unsustainable in the long-term.

WW

WW – formerly known as Weight Watchers – was established 57 years ago, when it pioneered group meetings to support people trying to lose weight. Today, it has moved online with a website and app offering 3,000 recipes, workouts and an online community to make you feel part of a 'movement'.

The old meetings are now called 'Express Workshops' and weigh-ins are part of individual 'Wellness Check-Ins', meanwhile the new myWW+ programme creates personalised plans for each member.

Members use SmartPoints, a daily budget tailored to their needs to spend as they choose or to be saved up for celebrations. Zero point foods can be eaten freely and include most fruit, non-starchy vegetables, eggs, chicken, turkey, fish, shellfish, beans, legumes, tofu, tempeh and non-fat plain yogurt, while High SmartPoint foods – which use up more of your daily budget – are high in saturated fat and sugar.

BEST FOR: Itteaches the most nutritionally valuable choices to fill you up, without demonising 'unhealthy' food or treats, which makes it a long-term option.

Being part of a well-established weight loss community is important for many people, and meetings – physical or online – are shown to improve success on a diet.

NOT FOR YOU IF: While many people find the group support invaluable, nutrition consultant Jenna Hope warns they have a downside. 'Weight loss is at risk of being viewed as a competition… rather than focusing on weight loss for oneself.'

SLIMMING WORLD

Slimming World is an established low fat, low sugar diet that, like WW, relies on group meetings for accountability and encourages a points-based eating system.

Participants are allowed 'free foods' including dried pasta, potatoes and lean meats, and 'speed foods' which include almost all vegetables and many fruits, making up a third of a plate at every meal.

Cooking from scratch is strongly encouraged, and dieters are encouraged to trim off visible fat, choose meat products containing no more than five per cent fat, and use Fry Light instead of cooking oil.

In addition, there's a 'syn' allowance of between 10 to 15 syns a day, which can be 'spent' on foods such as chocolate. Processed foods use up 'syns' quickly, which can be educational.

BEST FOR:Weight loss is at a gradual, sensible rate (usually up to 2lb a week) and participants have access to meetings and weigh-ins, adding face-to-face accountability and group motivation, which also suits the less tech-savvy. At £4.99 a week, the price is accessible and you can be a lifelong member for free if you remain within 3lb of your target weight.

NOT FOR YOU IF:The terminology of 'syns', with its shame-based connotations, can be unhelpful – dieters shouldn't see food as 'sinful' or otherwise. It also eliminates healthy fats in your diet by avoiding foods such as nuts, seeds, flax, avocado and olive oil. Syns don't help with this. For instance, where an avocado is classed as 14 syns but a can of Coke is seven syns it's unlikely that participants will 'waste' syns on healthier choices. This feels like rocky science.

NOOM

Noom has earned the distinction of being the 'most searched' diet on the internet thanks to its focus on behavioural science and psychology to help shift dieters' mindsets about food and self-image.

There is no diet plan to follow but users decide the time-frame to reach their weight loss goal and are given daily calorie goals. However, by my assessment these are incredibly low (for example, 1,200 calories for a 5ft 5in woman), so instead, focus on the tool that helps improve your eating with an easy-to-use colour coding system.

You're encouraged to eat plenty of green foods (fruit, vegetables, fat-free dairy, tofu and grains), a moderate amount of amber foods (lean meat, fish, beans, avocado) and a small amount of red foods (fried food, processed drinks, fast food and sugary snacks).

Support is key to its success, with groups and coaches available to keep you on track. Meanwhile, regular logging is all part of the process: everything you eat and drink each day, any exercise you've done and your daily weigh-ins all must be entered into the app. Daily lessons help educate you on food and eating, while frequent quizzes test your new knowledge.

BEST FOR:By teaching the psychology and science behind eating, Noom encourages moderation and is removing the shame around weight. 'It also appears to promote a more holistic attitude to health and wellbeing than just body weight,' adds Miss Long. 'For example, the app encourages mindfulness when eating, getting plenty of sleep and staying hydrated.'

NOT FOR YOU IF: The app can be fairly 'naggy', with daily prompts and reminders if you've failed to log a meal or not done your lessons.

The focus on daily weigh-ins could also do more harm than good. 'This is a really unhealthy behaviour as it can leave you hyper-fixated on weight and can make you feel awful if the number isn't going down,' says Miss Long.

But most crucially, is it a case of the emperor's new clothes? 'Noom is advertised everywhere and gives off the illusion that it is "not a diet" but when you really look at it, it is just that,' says Miss Long. 'Just because a diet is "tailored to you" based on an online questionnaire, that doesn't make it not a diet.

'At the end of the day, Noom is still focused on "good" and "bad" foods and limiting intake in the same way as other diet plans – but this time with an £88 price-tag for four months.'

SECOND NATURE

Set up by former NHS advisers to tackle Britain's obesity and type 2 diabetes epidemic, Second Nature is a strongly science-backed plan designed by dietitians promising to help people change their bad habits into healthy ones.

It encompasses the best of many programmes, combining behavioural and nutritional science with support and encouragement to change your lifestyle longer-term.

Part of the NHS's Healthier You programme, it provides a meal planner, weight and step trackers, an exercise toolbox and hundreds of healthy recipes, as well as access to a support group and a registered nutritionist or dietitian.

Articles cover advice on choosing healthy foods, setting good habits, the power of positive thinking, exercise options and the importance of sleep.

The 'tech' package is £13.75 a week and includes a tailored 12-week plan, a digital support group, full access to the app and platform and a Second Nature recipe book. It also adds in smart weighing scales which autosync to the app. (For the less tech-minded, a £10-a-month package comes without the scales).

BEST FOR:The NHS endorsement should give those with clinical or pre-clinical conditions the confidence to give it a go. It has successfully helped those with pre-diabetes, type 1 and 2 diabetes, coeliac disease, IBS and gastrointestinal disorders, hypothyroidism, PCOS, rheumatoid arthritis and fibromyalgia. And some 95 per cent of participants lose weight on the programme, so this seems to be one that 'sticks'.

NOT FOR YOU IF:The method would be less effective for those who prefer to go it alone, while the tracking and recording can put people off. The financial commitment could also be a deterrent.

MEDITERRANEAN DIET

There is no one definition of this but it generally focuses on fruit, vegetables, beans and pulses, nuts, cereals, grains, fish and unsaturated fats such as olive oil. It's lower in meat and dairy, water is the main drink but a moderate amount of wine is fine with meals.

'Unlike other complex and restrictive diets, the Mediterranean diet is packed with nutritious and delicious foods,' says Miss Long. 'It has been hailed as the gold-standard for years among health professionals and scientists and is well-known for its health-promoting properties.'

Research shows that benefits include improved heart health, circulation, brain function, reduction in inflammation and increased gut biodiversity. It encourages the consumption of 'real' foods, as opposed to processed, and is a diet that can be adopted for life.

BEST FOR:Most of us! It's a great wellness diet to follow long term: the principles are simple and you shouldn't feel hungry as it includes all food groups. There is a huge amount of choice in terms of the meals and snacks you can eat and enjoy. You don't need to pay to join a diet – in fact, it's more of a lifestyle than a weight loss plan, as many other diet brands, such as WW, incorporate the key principles of the Mediterranean diet.

NOT FOR YOU IF:Some people will find this quite 'carb-heavy'. Since there are no limits or portion sizes, it is possible to gain weight by overeating healthy fats, which are calorific.

D.A.S.H DIET (DIETARY APPROACHES TO STOP HYPERTENSION)

This diet was designed in the 1990s by the National Heart, Lung and Blood Institute (NHLBI) in the US as a way to reduce high blood pressure (hypertension) which is a risk factor for heart disease.

The backbone of the diet is fruit, vegetables and wholegrains, fat-free or low fat dairy plus fish, poultry, nuts, beans and vegetable oils. These are all high in nutrients including potassium, calcium, magnesium, protein and dietary fibre which have all been shown to reduce blood pressure.

Food that's high in saturated fat such as meat, full-fat dairy, coconut and palm oil and added salt and sugar are discouraged. It also urges exercise, giving up smoking and cutting back on alcohol.

'It's similar to the Mediterranean diet,' says Miss Long. 'But the DASH diet takes it one step further, giving more specific guidance on portions which can be helpful for people looking for something a little more structured.'

BEST FOR:'There is a wealth of evidence showing that this particular way of eating can not only lower blood pressure but also cholesterol and heart disease risk,' says Miss Long.

But it's not just for people with hypertension – a heart-healthy diet is appropriate for most people and represents a healthy, balanced and nutrient-rich style of eating.

NOT FOR YOU IF:Some health professionals disagree with eating only low-fat dairy, particularly in processed food. When stripping out fat, manufacturers often add sugar for flavour, so read the labels carefully, especially with yoghurt.

PALEO

The Paleo diet aims to mirror the food eaten by paleolithic man more than 10,000 years ago – a time before farming and long before the pitfalls of our modern-day diet which is rich in processed food, salt, sugar and trans fats.

There is much debate about how 'true' our modern take on the Paleo diet really is, without knowing what foods actually existed at the time or how our current produce compares to prehistoric, wild versions. However, it generally includes lean meat, fish, shellfish, eggs, seeds, nuts, vegetables, olive and coconut oils and sometimes small amounts of honey.

Root vegetables may be allowed in moderation, such as sweet potato and cassava. But dairy products, wholegrains, cereals, refined grains and sugars, white potatoes, legumes (beans, lentils, peanuts), alcohol, coffee, salt, refined vegetable oils and processed foods are all out.

BEST FOR: Meat-lovers and/or people who are dairy and gluten-free. The high protein angle also appeals to gym-goers. The regime is a way to reduce processed foods and will suit anyone who enjoys – and has the time – to prepare fresh food every day.

NOT FOR YOU IF:It's hard if you're on a budget. The sheer volume of meat can be expensive. It could affect your health too: exclusion of dairy requires caution, especially if you are at risk of osteoporosis; a Paleo diet could also contain lower levels of B vitamins, calcium and vitamin D. The exclusion of wholegrains could lead to lower fibre intake, increasing risk of constipation. This, coupled with higher meat intake (which could also increase saturated fat), could potentially increase risk factors for diabetes and heart disease.

The best of the rest...

1:1 DIET BY CAMBRIDGE WEIGHT PLAN

Created in the 1960s, the diet, previously known as the Cambridge Weight Plan, is a very low calorie diet, in which dieters can start off eating as little as 500 calories a day for a week, primarily in the form of meal replacement shakes, snack bars and packaged soups.

Meal replacement products are an unhealthy, unhelpful part of the dieting industry and are a cause of 'yo-yo dieting' as the moment 'normal' eating is resumed the weight is regained, and typically some more.

THE VOLUMETRICS DIET

Also called 'volume eating', this is a 'free foods' diet, encouraging dieters to eat their fill of vegetables, fruit, wholegrains and low fat dairy – low energy, high density foods that are packed with vitamins and minerals – to feel full and satisfied. This style of eating can be helpful for those who find restrictions unhelpful or who complain they always feel hungry on a diet.

THE MIND DIET

Combining the health benefits of both the Mediterranean and DASH diets, this plan claims to be 'brain-friendly' and even help to prevent dementia. Key foods to include are leafy greens, other vegetables, nuts, berries, beans, fish, wholegrains, poultry, olive oil and wine. But red meat, butter or margarine, cheese, pastries and sweets, fried or fast foods should be limited. It is fairly simple to follow, with a little time and effort needed for meal planning.

THE WINNER IS… THE MEDITERRANEAN DIET

Sarah O'Neill says: My diet is most reflective of the Mediterranean diet, with an emphasis on plant-based eating.

I believe five a day should be a baseline and we should strive to eat 10 low sugar pieces of fruit and veg a day. I aim to eat two portions of fish a week (one oily), moderate amounts of other meat (lean chicken and beef no more than once a week), and aim to ensure we have at least two meat-free dinners on the menu per week.

Eating the rainbow (making sure your fruit and vegetables are a variety of colours) is a good principle to follow to ensure you're receiving a plethora of vitamins and minerals, and diversity in eating is key, especially considering gut health.

Rosie Long agrees: 'If you are looking to improve your health and lose weight, you're better off sticking to general healthy eating principles which are found in the Mediterranean and DASH diets. They're a way of eating for overall good health and don't come with any scary (or nonsensical) rules. Plus, they are backed by a heap of good quality evidence.'

The experts share their top tips for making YOUR diet stick

Get ready:'Readiness to change is the pivotal factor,' says Sarah O'Neill. 'Have a goal or motivator beyond weight loss, for instance, to be fitter to run around with the kids or to have more energy and focus at work.'

Change your mindset: 'Shift the emphasis from "this is a punishment because I'm overweight so I have to do this" to "I really care about my body, fitness and health and I value and love myself, therefore I'm going to eat food that sustains and nurtures me as opposed to food that increases my disease risk",' says Mrs O'Neill.

Talk to experts:'Seek help from a registered professional,' advises Rosie Long. 'A registered nutritionist or dietitian will be able to guide you through a healthy weight management programme that doesn't have to result in deprivation. You'll learn more about nutrient-dense foods and how to incorporate healthy habits into your life over time.'

Use social media:'Following registered nutritionists or dietitians on social media ensures information you're getting about nutrition is evidence-based and supports a healthy relationship with food,' says Miss Long. 'It's also a good place to start for recipe ideas.'

Start meal planning: 'It's a helpful way to meet seemingly difficult goals such as eating at least 30 different plants a week, including vegetables, grains and nuts,' says Mrs O'Neill.

Low Carb Diet Hunger Pangs

Source: https://www.mailplus.co.uk/edition/health/medical-matters/117822/which-diet-is-best-for-you-from-keto-to-low-carb-and-caveman

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Is Vitamin D Present In Milk

Is Vitamin D Present In Milk

Adv Nutr. 2013 Jul; 4(4): 453–462.

Natural Vitamin D Content in Animal Products¹

This article has been cited by other articles in PMC.

Abstract

Humans derive most vitamin D from the action of sunlight in their skin. However, in view of the current Western lifestyle with most daily activities taking place indoors, sun exposure is often not sufficient for adequate vitamin D production. For this reason, dietary intake is also of great importance. Animal foodstuffs (e.g., fish, meat, offal, egg, dairy) are the main sources for naturally occurring cholecalciferol (vitamin D-3). This paper therefore aims to provide an up-to-date overview of vitamin D-3 content in various animal foods. The focus lies on the natural vitamin D-3 content because there are many countries in which foods are not regularly fortified with vitamin D. The published data show that the highest values of vitamin D are found in fish and especially in fish liver, but offal also provides considerable amounts of vitamin D. The content in muscle meat is generally much lower. Vitamin D concentrations in egg yolks range between the values for meat and offal. If milk and dairy products are not fortified, they are normally low in vitamin D, with the exception of butter because of its high fat content. However, as recommendations for vitamin D intake have recently been increased considerably, it is difficult to cover the requirements solely by foodstuffs.

Introduction

The term vitamin D, as used here, refers to the secosteroids ergocalciferol (vitamin D-2)² and cholecalciferol (vitamin D-3). Their structural difference lies only in the C-17 side chain, the former having an additional C-22 to C-23 double bond and a C-24 methyl group ( Fig. 1 ). Vitamin D-2 is formed by UV radiation (in particular UVB radiation) of ergosterol, which is found in plants, fungi, and invertebrates. For vitamin D-3, the genesis is the same, but the provitamin is 7-dehydrocholesterol, which is found in vertebrates. In humans as well, vitamin D-3 is synthesized in the skin with the help of sunlight (1).

Structure of ergocalciferol (top) and cholecalciferol (bottom).

After the production of vitamin D-3 in the skin or after its absorption from the gut, the vitamin is transported to the liver, bound in blood to vitamin D–binding protein. In the liver, it is hydroxylated to 25-hydroxycholecalciferol [25(OH)-D-3] (calcidiol), the rate being related to substrate supply (2). 25(OH)D₃ is the major circulating metabolite of vitamin D, and its concentration in blood is used as a measure of vitamin D status (1, 3, 4). In the kidney, 25(OH)D is activated with a second hydroxylation to 1,25-dihydroxycholecalciferol [1,25(OH)₂-D-3] (calcitriol), the production being tightly regulated by calcium (via parathyroid hormone), by phosphate (via fibroblast growth factor 23), and during growth and pregnancy (1, 5, 6). The main target tissues of 1,25(OH)₂-D-3 are intestine, bone, and kidney where it carries out hormonal functions. 25(OH)-D-3 as well as 1,25(OH)₂-D-3 are catabolized and the final products are excreted in the bile (2).

Humans derive most vitamin D from the action of sunlight in their skin. However, the current Western lifestyle with most activities taking place indoors often prevents sufficient sun expose. In addition, season and latitude may diminish the intensity of the sun, and also clothing, sunscreen, and skin pigmentation interfere with vitamin D synthesis (6). In this case, dietary intake becomes increasingly important. However, only a few foodstuffs, mainly of animal origin (e.g., fish, meat, offal, egg, dairy), are recommended in literature to be a valuable source of naturally occurring vitamin D-3 (2). This report compiles the available information on vitamin D content in various animal foods in relation to the prevention of vitamin D deficiency. The focus is on the natural vitamin D-3 content because there are many countries (e.g., most of the European countries) in which foods are not regularly fortified with vitamin D. 25-Hydroxycholecalciferol is included because this metabolite contributes to the total biological activity (7).

Functions of vitamin D

The vitamin D metabolite 1,25(OH)₂-D-3 acts as a hormone in the regulation of calcium and phosphorus metabolism with the aim of maintaining normal calcium and phosphorus concentrations in serum ensuring a normal mineralization of bone (1, 2). Vitamin D may also play a role in muscle development because vitamin D receptor is located in muscle tissue and vitamin D deficiency leads to muscle weakness. Several further tissues exhibit a vitamin D receptor, among other brain, prostate, breast, and colon tissues as well as immune cells. Epidemiologic findings suggest benefits of vitamin D on cardiovascular mortality, hypertension, colorectal cancer, multiple sclerosis, type 1 diabetes, immune function, and inflammation (1, 8). However, apart from the positive influence of vitamin D on fracture risk and falls, data are not yet compelling but need further evaluation in clinical studies.

Requirements of vitamin D and vitamin D deficiency

25(OH)-D-3 concentrations in blood are used to determine the vitamin D status (9). Serum levels of <25 nmol/L come along with the risk of rickets (deformation of bones due to inadequate development) in children and of osteomalacia (brittle bones) in adults. Levels of 25 to 49 nmol/L are seen as insufficient (10). The question about the optimal serum concentration cannot yet be answered clearly. In adults, data suggest that serum levels of >75 nmol/L are optimal for bone health as well as for nonskeletal health benefits of vitamin D. However, concentrations between 50 and 60 nmol/L are often seen as (more conservative) target because above that there is no further increase in bone density, muscle function, and parathyroid hormone suppression (6, 11).

With sufficient UVB exposure, dietary intake of vitamin D is not necessary. However, due to environmental influences (see above) synthesis of vitamin D is not always adequate; therefore, dietary intake is advisable. The RDA of vitamin D for females and males between 9 and 70 y of age in the United States is set at 15 μg/d (600 iu/d) and also the Endocrine Society suggests this amount for adults aged 19–50 y but indicates that to increase the blood level of 25(OH)-D-3 consistently above 30 μg/L, at least 37.5–50.0 μg/d (1500–2000 iu/d) of vitamin D may be required. The German-speaking nutrition societies (D-A-CH recommendations) recently increased their recommendation for children and adults from 5 μg/d (200 iu/d) to 20 μg/d (800 iu/d), whereas the European RDA for adults remains at a daily intake of 5 μg/d (200 iu/d), but the upper limit from 50 μg/d (2000 iu/d) was increased to 100 μg/d (4000 iu/d) (11–15).

Vitamin D in animal food

Only a few foodstuffs naturally contain vitamin D, and these foodstuffs are mainly of animal origin. Above all, vitamin D-3 is found in these products together with its metabolite 25(OH)-D-3. As the latter is also biologically active and such contributes to dietary intake, it is included in the following compilation (7). There is still no consensus, if compared with vitamin D-3, that the bioactivity of 25(OH)-D-3 is higher. A bioactivity up to 5 times higher is proposed, but could not be demonstrated in all investigations (16). However, the outcome of a recent study supports a factor of 4–5 (17). Other metabolites are only contained in trace amounts and do not contribute much to biological vitamin D activity (7). In dairy, varying amounts of vitamin D-2 and 25-hydroxyergocalciferol [25(OH)-D-2] are documented and therefore are also mentioned in the overview. However, supplementation studies suggest that vitamin D-2 is not as potent as vitamin D-3 in increasing serum 25-hydroxyvitamin D [25(OH)-D] concentrations (18). Described below are results of studies determining the vitamin D content by HPLC or liquid chromatography-linear mass spectrometry (LC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Investigations based on classic bioassays measuring antirachitic activity are not included in this overview.

Meat, offal, and meat products

A search of the national food composition databases of Denmark, France, Germany, Switzerland, Canada, and the United States for vitamin D content in various raw meat cuts yielded the following values: 0.0–9.0 μg/kg for beef, 1.0–23.0 μg/kg for pork, 1.0–61.0 μg/kg for lamb, 0.0–50.0 μg/kg for veal, 0.0–14.0 μg/kg for poultry, and 0.0–23.0 μg/kg for various meat products (19–24). However, the vitamin D content is not available for all meat cuts, and the databases do not give any information about how the data were obtained. A few values are inexplicably high and may be based on a single analysis and/or that the analyzed meat originated from animals supplemented with vitamin D.

Table 1 presents vitamin D-3 and 25(OH)-D-3 content of meat and offal found in literature. Data on animals whose diets were supplemented beyond the normal with vitamin D-3 or 25(OH)-D-3 were excluded. Koshy and VanDerSlik (25) examined 25(OH)-D-3 contents in raw liver, muscle, and kidney from cows in Michigan. The highest concentrations were found in kidney and the lowest in muscle meat. Mattila et al. (26) investigated raw beef meat and liver samples that were purchased in retail stores in the Helsinki area in autumn and spring. Vitamin D-3 concentrations were <0.5 μg/kg in all beef samples; 25(OH)-D-3 concentrations ranged from <0.5 to 3.5 μg/kg, with the highest values in liver. The results did not vary substantially between the 2 seasons. Kobayashi et al. (27) did not find any vitamin D (sum of vitamins D-3 and D-2) in bovine meat and offal when analyzing 69 different Japanese foods purchased from markets. Between 2000 and 2004, several experiments of the Department of Animal Science at the Iowa State University regarding the effect of vitamin D-3 supplementation on beef tenderness were published (28–33). The vitamin D-3 concentrations in the control groups of the steers (receiving 90% concentrate diet with a commercial nutrient supplement) ranged between 0.8 and 10.0 μg/kg in raw meat, between 1.9 and 140.8 μg/kg in raw liver, and between 1.3 and 27.1 μg/kg in raw kidney. For 25(OH)-D-3, the concentrations in meat were 0.2–4.1 μg/kg, in liver 0.7–7.7 μg/kg, and in kidney 0.9–23.3 μg/kg. Muscle concentrations of vitamin D-3 and 25(OH)-D-3 vary significantly according to biological type of cattle, liver concentrations, however, do not (31). Additional vitamin D-3 supplementations up to 7.5 million IU/steer for 8 or 9 days before slaughter increased vitamin D-3 and 25(OH)-D-3 values in meat and offal (29, 30, 32, 33). Purchas et al. (34) found vitamin D-3 concentrations between 0.9 and 1.3 μg/kg and 25(OH)-D-3 concentrations between 2.7 and 5.8 μg/kg in raw beef meat (various cuts) of animals raised on pasture without any supplements.

Table 1.

Published natural vitamin D-3 and 25(OH)-D-3 content in raw meat and offal¹

Reference	Foodstuff	D-3	25(OH)-D-3
		μg/kg	μg/kg
Koshy and VanDerSlik (25)	Cow, liver		2.7–5.3
	Cow, muscle		1.5–3.4
	Cow, kidney		5.1–9.8
Mattila et al. (26)	Beef, steak	<0.5	0.8
	Beef, chuck	<0.5	0.5
	Beef, liver	<0.5	3.4
Kobayashi et al. (27)	Beef (separable lean)	02
	Beef, liver	02
Montgomery et al. (30)	Beef, top round steak	2.8	1.3
	Beef, strip loin steak	4.1	1.4
	Beef, liver	8.6	7.7
	Beef, kidney	7.4	23.3
Montgomery et al. (29)	Beef, strip loin steaks	9.5	4.1
	Beef, liver	140.8	1.9
Wertz et al. (28)	Beef, longissimus muscle		0.9
Foote et al. (33)	Beef, longissimus dorsi muscle	1.1	1.7
	Beef, semimembranosus muscle	0.8	1.4
	Beef, infraspinatus muscle	1.1	0.9
	Beef, liver	1.9	2.6
	Beef, kidney	1.3	3.0
Montgomery et al. (32)	Beef, longissimus muscle	5.3	0.3
	Beef, liver	13.3	0.8
	Beef, kidney	12.2	1.6
Montgomery et al. (31)	Beef, strip loin	2.6–10.0	0.2–0.4
	Beef, liver	12.3–14.2	0.7–0.9
	Beef, kidney	4.2–27.1	0.9–2.0
Purchas et al. (34)	Beef, shoulder roast	1.0	4.8
	Beef, rump mince	1.3	5.8
	Beef, strip loin	1.1	2.7
	Beer, topside roast	0.9	4.8
Mattila et al. (26)	Pork, fillet	1.1	<0.6
	Pork, Boston butt	3.4	0.7
	Pork, liver	4.0	4.4
Kobayashi et al. (27)	Pork (separable lean)	7.02
	Pork (total edible)	13.82
	Pork, liver	12.52
Clausen et al. (35)	Pork, loin	1.5	0.9
	Pork, leg inside	0.5	0.7
	Pork, thin belly	2.1	1.4
	Pork, neck	1.6	1.3
Wilborn et al. (36)	Pork, longissimus muscle	13.9	69.3
Bilodeau et al. (37)	Pork, lean ground	2.1	0.9
	Pork, medium ground	2.4	0.9
	Pork, center chops boneless (whole)	1.7	0.8
	Pork, tenderloin (whole)	1.8	1.4
	Pork, back ribs (whole)	3.9	1.3
	Pork, shoulder blade roast boneless (whole)	3.7	1.2
	Pork, loin rib roast (whole)	3.1	1.0
Kobayashi et al. (27)	Sheep (mutton and lamb)	02
Purchas et al. (34)	Lamb, leg roast	0.6	12
	Lamb, leg steak	0.4	10.4
	Lamb, rack roast	0.3	5.7
	Lamb, shoulder chop	0.9	8.4
Kobayashi et al. (27)	Chicken, breast	02
	Chicken, liver	2.02
	Turkey	1.02
	Domestic duck	23.02
Mattila et al. (26)	Chicken	2.9	2.5
Mattila et al. (38)	Chicken, leg and thigh	3.0	≤2.0
	Chicken, fillet	2.0	≤2.0

Analyses by Mattila et al. (26) in raw pork meat purchased in several retail stores and pork liver bought from 1 meat wholesaler in the Helsinki area in spring and autumn showed only minor variations in the results of the 2 seasons. In the case of the muscle samples, a positive correlation between the fat and vitamin D-3 content was found. Compared with Mattila et al. (26), Kobayashi et al. (27) found rather high vitamin D (sum of vitamins D-3 and D-2) amounts in meat and liver of pork, respectively. In raw pork cuts of varying fat content, Clausen et al. (35) measured vitamin D-3 concentrations from 0.5 to 2.1 μg/kg and 25(OH)-D-3 concentrations from 0.7 to 1.4 μg/kg. Vitamin D-3 and 25(OH)-D-3 were significantly associated with the fat content of whole cuts, and in the cuts 8 to 10 times more vitamin D-3 and 2 to 3 times more 25(OH)-D-3 was found in lard and intramuscular fat than in the lean parts. Wilborn et al. (36) investigated the effect of supplemental vitamin D on pork quality. In the control group, vitamin D-3 and 25(OH)-D-3 concentrations in longissimus muscle were 13.9 and 69.3 μg/kg, respectively, which is substantially higher than the values given in the other publications. Last, but not least, Bilodeau et al. (37) determined vitamin D-3 and 25(OH)-D-3 concentrations in various raw pork cuts collected from major retail centers in Canada. Vitamin D-3 concentrations ranged from 0.8 to 4.2 μg/kg and 25(OH)-D-3 concentrations from 0.8 to 1.4 μg/kg.

In raw samples from 4 lamb cuts (lambs raised on pasture), Purchas et al. (34) determined vitamin D-3 concentrations of 0.3–0.9 μg/kg and 25(OH)-D-3 concentrations of 5.7–12.0 μg/kg. By contrast, Kobayashi et al. (27) found no vitamin D in lamb and mutton.

Chicken samples purchased in spring and autumn from retail stores in Finland were analyzed for their vitamin D-3 and 25(OH)-D-3 content by Mattila et al. (26). Mean vitamin D-3 content was 2.9 μg/kg and 25(OH)-D-3 2.5 μg/kg with no significant seasonal difference. In a more recent repetition of this investigation similar vitamin D-3 concentrations were detected, but 25(OH)-D-3 concentration was below detection limit (38). Kobayashi et al. (27) found no vitamin D in chicken breast but slight amounts in chicken liver and turkey and a high amount (325 μg/kg) in domestic duck. The latter might be due to supplements in feedstuff.

In meat products, the vitamin D content is dependent on the vitamin D concentration of the processed fresh meat and the fat content. In various Swiss meat products, vitamin D-3 content from below detection limit (<2.5 μg/kg) to 23 μg/kg was found (39–42). Values below detection limit were, for instance, found in different types of cooked ham and in dried beef with little fat. The largest amounts provided salami type meat products, Vienna sausages, and lard.

Dairy

A search in different national food composition databases of Denmark, France, Germany, Switzerland, Canada, and the United States for vitamin D content in dairy products yielded the following values: whole milk, 0.3–1.0 μg/kg (US and Canada present only values for fortified whole milk: 7.05 μg/kg and 9.9 μg/kg, respectively); cream, 3.7–10.8 μg/kg; butter, 5.9–14.1 μg/kg; yogurt, 0.4–6.0 μg/kg; curd cheese, 2.0–7.05 μg/kg; soft cheese, 2.8–5.8 μg/kg; semihard and hard cheese, 2.0–18.1 μg/kg. Only few data are available in these databases for dairy products from noncow origin: goat's milk, 0.6–2.8 μg/kg; ewe's milk, 1.8 μg/kg; feta, 3.0–4.0 μg/kg. The databases do not differentiate between vitamins D-2 and D-3, nor give any information about inclusion or exclusion of the vitamin D metabolites and how the data were obtained (19–24).

The influence of different factors like fodder, supplementation, sunlight, seasons, and races on the vitamin D content in (cow's) milk and dairy products has been a topic for >80 y (43). Modern analytical methods like HPLC, LC-MS, and LC-MS/MS confirmed the results from earlier studies obtained by indirect detection by biological assays (44). On the other hand, they also opened the possibility to differentiate between the several metabolites and to give more quantified results (37). In both periods, the findings agree that vitamin D content in milk and dairy products is originally rather low. Table 2 presents vitamin D-3 and 25(OH)-D-3 content of milk and dairy products found in literature. However, the detected values partly vary considerably among the different studies (7, 44). Animal supplementation influences significantly the concentration of vitamin D in milk, which explains the relatively high values found in the milk of these animals. Data of animals whose diets were supplemented with vitamin D-3 or 25(OH)-D-3 were therefore excluded. On the other hand, in milk and dairy products vitamin D-2 and 25(OH)-D₂ are partially found in relevant concentrations, so we decided to include these values in Table 2 where available. Mouillet et al. (45) collected raw milk samples from different regions in France. The concentration of vitamin D-3 varied between and within the regions. Kunz et al. (46) distinguish between the various metabolites and found 10 times more 25(OH)-D than vitamin D, but they give no information on whether the values are the sum of vitamins D-2 and D-3 or only 1 of them. In commercially available milk samples in Japan, 0.42 μg/L vitamin D-3 and 0.27 μg/L 25(OH)D₃, but neither vitamin D-2 nor its metabolites were detected (47). In his review, Kneifel (48) listed a range of 0.1–2.0 μg/L for raw milk and 0.8 μg/L for pasteurized whole milk and ultra heat-treated (UHT) milk, respectively, but it is not clear which method was used to analyze these samples. In all samples of the study carried out by Mattila et al., the values for vitamins D-2 and D-3 as well as for the metabolites were below the detection limit of 0.2 μg/L (26). Analysis with the LC-MS and LC-MS/MS method of whole milk (3.8% fat) and fresh cow's milk (∼4.5% fat) detected 0.2 μg/L and 0.5–0.6 μg/L of vitamin D-3, respectively. The vitamin D-3 content in fat-reduced milk (0.1% and 1.0%) was below the detection limits (49). The apparent correlation of the fat-soluble vitamin with the fat content of the milk was later clearly demonstrated in a Danish study (50).

Table 2

Published natural vitamin D-3, vitamin D-2, 25(OH)-D3, and 25(OH)-D2 content in milk and dairy products¹

Reference	Foodstuff	D-3	25(OH)-D3	D-2	25(OH)-D2
Mouillet et al. (45)	Raw milk	0.60–1.38
Kunz et al. (46)	Cow's milk	0.052	0.50
Takeuchi et al. (47)	Cow's milk	0.42	0.27
Kneifel (48)	Raw milk	0.1–2.02
	Whole milk PAST	0.8
	UHT milk	0.8
Mattila et al. (26)	Milk	<0.2	< 0.2
Trenerry et al. (49)	Milk (0.1% fat)	<0.02
	Milk (1.0% fat)	<0.02
	Whole milk (3.8% fat)	0.02
	Raw milk (4.5% fat)	0.06
Hollis et al. (57)	Raw milk	0.043	0.373
McDermot et al. (58)	Raw milk	0.075	0.250
Jakobsen and Saxholt (50)	Whole milk	0.092	0.075	0.034	0.031
	Milk semiskimmed	0.046	0.042
	Whole milk (organic)	0.076	0.057
Takeuchi et al. (63)	Butter4	7.25
Kneifel (48)	Butter4	10
Mattila et al. (26)	Butter4	2.0	0.5	0.5
Jakobsen and Saxholt (50)	Butter4	1.96	0.96	0.61	0.58
Kneifel (48)	Cheese (curd, Camembert, Edam, Gouda, Emmental)4	0–10
Mattila et al. (26)	Edam cheese4	1.1	0.5
Mattila et al. (26)	Cream	0.7	0.9	0.1
Jakobsen and Saxholt (50)	Cream	0.94	0.59
Jakobsen and Saxholt (50)	Coffee cream	0.44	0.27

In some countries like the United States, Canada, and the United Emirates, milk and dairy products for sale are fortified with vitamin D either by law (Canada) or by choice (United States and United Emirates) (51, 52). Another possibility to improve the vitamin D content in milk and dairy products is to supplement the cows. But neither the supplementation over the fodder nor the intravenous or intramuscular application of vitamin D significantly improves the vitamin D content in the milk (53–56). However, a direct oral supplementation of cows with doses from 4000 iu/d to 40,000 iu/d of vitamin D resulted in an increase of vitamin D (57), and another experiment also showed a positive correlation between increasing oral supplementation and the concentration of vitamin D in milk (58). In several countries, the oral supplementation of dairy cows is recommended with varying doses (50, 59). Although this is done to secure the health of the cows and not with the aim to increase the vitamin D content in milk, it could nevertheless have an impact on it.

For some time, a water-soluble vitamin D metabolite found in whey was held responsible for an additional vitamin D activity in milk (60). But this hypothesis was not confirmed, and all vitamin D activity was explained by the sum of vitamin D-3, 24,25(OH)₂-D₃, 1,25(OH)₂-D3, and 25(OH)-D-3 (61, 62). Hollis et al. (57) realized that vitamin D and its metabolites initially present in whey fraction migrate with time into the fat fraction of the milk.

Few data are available for the vitamin D content in dairy products. Because of the high fat content, the values are significantly higher in butter than in milk; they vary from 1.96 μg/kg to 10 μg/kg (26, 48, 50, 63). Some but not all of the authors also reported mentionable concentrations for 25(OH)-D-3, vitamin D-2, and 25(OH)-D₂ (26, 50). Insufficient data are available for cheese. In the list of Kneifel (48), a range of 0–10 μg/kg is given for a summary of different cheese types (curd, Camembert, Edam, Gouda, and Emmental). More detailed are the results of the analysis of an Edam type cheese in which vitamin D-3 and 25(OH)-D-3 but not vitamin D-2 and 25(OH)-D₂ were detected (26).

Cream samples collected in Finland and Denmark contained 0.7 μg/kg and 0.94 μg/kg vitamin D-3, respectively, and 0.9 μg/kg and 0.59 μg/kg 25(OH)-D-3, respectively. The Finnish research group additionally reports vitamin D-2. The amounts of vitamin D-3 and 25(OH)-D-3 in coffee cream are only half of the values for whipping cream because of the reduced fat content (26, 50).

The Danish study shows significant seasonal variation of the vitamin D content in milk and dairy products, which confirms earlier observations (26, 50, 64).

Eggs

In the above-mentioned national food composition databases, vitamin D values for the whole egg and the egg yolk in particular can be found. The vitamin D content in eggs is practically all in the yolk. Based on the whole egg, the content varies between 14.4 and 29.3 μg/kg and between 32.5 and 55.8 μg/kg for egg yolks (19–24). Table 3 shows the values found in literature. Mattila et al. (38) analyzed pools of egg yolk from commercial chicken eggs collected in the spring and autumn. Vitamin D-3 and 25(OH)-D-3 content in the egg yolk was slightly higher in spring. The values correspond to previous analyses in 1992 and 1993 (65, 66); slightly lower content of vitamin D-3 and 25(OH)-D-3 was found in egg yolks by the same authors in 1999,however (67). Overall, the vitamin D-3 values found in literature vary between 8.0 and 30.0 μg/kg for whole chicken egg and between 34.0 and 58.0 μg/kg for egg yolks (27, 38, 66–69). The 25(OH)-D-3 is documented to range from 5.0 to 13.0 μg/kg in egg yolks (38, 65, 67, 70). The concentrations of vitamin D in eggs can be increased in a linear dose-dependent manner by supplementing chicken feed with vitamin D-3 (67, 71).

Table 3

Published natural vitamin D-3 and 25(OH)-D-3 content in chicken eggs¹

Reference	Foodstuff	D-3	25(OH)-D-3
		μg/kg	μg/kg
Koshy and VanDerSlik (70)	Egg, yolk		5.0–8.0
Jackson et al. (68)	Egg, whole	16
Sivell et al. (69)	Egg, whole	8–14
Takeuchi et al. (63)	Egg, yolk	39
Mattila et al. (66)	Egg, yolk (autumn)	40
	Egg, yolk (spring)	56
Mattila et al. (65)	Egg, yolk		9.8
Kobayashi et al. (27)	Egg, whole	302
	Egg, yolk	582
Mattila et al. (67)	Egg, yolk	34	9.3
Mattila et al. (38)	Egg, whole	14	3.8
	Egg, yolk (autumn)	40	10.0
	Egg, yolk (spring)	49	13.0

Fish

Fish and fish products are regarded as the major dietary source of vitamin D. National food composition databases show values in the range of 0 to 300 μg/kg (19–24). Amounts found in literature are presented in Table 4 . In 1984, Takeuchi et al. (63) reported the vitamin D-3 content of 8 different fish products. The values ranged between 5 and 356 μg/kg. The highest amounts were found in fresh eel and shiokara, a Japanese fish product. Kobayashi et al. (27) analyzed 18 different kinds of fish and reported vitamin D (total of vitamins D-2 and D-3) concentrations from 18 to 350 μg/kg. Fish liver was as high as 1200 μg/kg of vitamin D. Various fresh fish from the Baltic sea and 2 lakes in Finland as well as frozen fish and fish products were analyzed by Mattila et al. (72). Large variations were not only found between different fish species but also in the same species caught in different locations. The observed variations in vitamin D content between fish of the same species seem not to be related to the weight, sex, or age of the fish but may depend on the diet (i.e., the vitamin D-3 content of zooplankton). Contrary to general belief, no significant correlation between fat and vitamin D content was detected (72, 73). The vitamin D-3 content of the frozen fish and fish products ranged between <2 (shrimp) and 196 μg/kg (roe of vendace) (72). Lu et al. (74) and Bilodeau et al. (37) found vitamin D-3 concentrations between 6 and 453 μg/kg in various fish. Where 25(OH)-D-3 was analyzed in fish and fish products, the results were consistently very low and often there was no detectable content (37, 72).

Table 4

Published natural vitamin D-3 and 25(OH)-D-3 content in fish¹

Reference	Foodstuff	D-3	25(OH)-D-3
		μg/kg	μg/kg
Egaas and Lambertsen (89)	Tuna, liver	32,500
	Mackerel, liver	2400
	Mackerel, fillet	155
	Mackerel, red muscle	155
	Coalfish, liver	165
Takeuchi et al. (63)	Japanese pilchard	1361
	Skipjack	187
	Tuna, fatty meat	37
	Eel	268
Kobayashi et al. (27)	Anglerfish, liver	11002
	Indo-Pacific blue marlin	3502
	Chum salmon	3252
	Herring	2752
	Flat fish	2302
	Bastard halibut (cultured)	1802
	Bluefin tuna, fatty meat	1802
	Sand eel	1502
	Grunt	1502
	Rainbow trout	1502
	Eel	1402
	Red sea bream (cultured)	1302
	Mackerel	1102
	Pacific saury	1102
	Skipjack	1002
	Japanese pilchard	982
	Yellowtail	852
	Cod	182
Mattila et al. (72)	Baltic herring	171.0	ND
	Bream	138.0	ND
	Cod	69.0	ND
	Perch	2.9–244.0	ND
	Pike	12.0–47.0	ND
	Pikeperch	245.0	ND
	Rainbow trout (cultured)	76.0	1.4
	Vendace	23.3–245.0	<1.0
	Whitefish	122.0–444.0	<1.0–2.5
Lu et al. (74)	Wild salmon	249.0
	Farmed salmon	60.5
	Blue fish	70.6
	Farmed trout	97.8
	Tuna ahi	101.8
	Mackerel	6.0
Bilodeau et al. (37)	Mahi mahi	11.1	<0.2
	Canned pink salmon	223.0	1.1
	Tilapia	453.0	0.6

Bioavailability

Like other fat-soluble vitamins, vitamin D is absorbed incorporated in mixed micelles from the intestine into the enterocytes by nonsaturable passive diffusion. From there, vitamin D is transported along with chylomicrons via lymph to the circulation (2, 75). The more polar metabolite 25(OH)D is absorbed better and faster than vitamin D because it is also taken up directly from the proximal jejunum into the portal vein (7, 75).

Almost all studies on vitamin D bioavailability were done with different kinds of vitamin supplements. Vitamin D absorption from supplements varies depending on the used vehicle substance (oils, powders, and ethanol) (76). There are not a lot of data on its availability from natural sources. Based on an investigation with special pig meat (pigs receiving only vitamin D-2 as the sole vitamin D source), van den Berg (75) estimated the average relative bioavailability of vitamin D-2 from meat sources to be ∼60% compared with a vitamin D-2 supplement. It has also been shown that the bioavailability of vitamin D from fortified hard cheese (cheddar and low-fat cheese) is equivalent to supplements (77) and that vitamin D bioavailability is not influenced by the fat content of the fortified milk (78). Apparently vitamin D-3 strongly binds to β-lactoglobulin A as well as β-casein, protecting it from a polar environment in fat-free dairy products. This stabilization of vitamin D-3 may ensure the availability for absorption within the human body (79). These strong binding affinities may not have a negative impact on the bioavailability because vitamin D-2 was more efficiently absorbed from fortified cheese than from water (80). Vitamin D-3 encapsulated in reformed casein micelles was highly bioavailable in a clinical study, comparable to a commercial aqueous supplement (81). Other investigations report no influence of the vehicle on the bioavailability of vitamin D supplements but a higher response of vitamin D-3 compared with vitamin D-2 (16). An influence of calcium, phosphorus, vitamin A, and cholesterol on vitamin D bioavailability is assumed, but further investigation is needed to determine the mechanism (82). Additionally, growing evidence suggests an interaction of a genetic polymorphism in key genes with bioavailability, transport, distribution in body pools, metabolism, and action of vitamin D (82, 83).

Influence of processing and cooking

Cooking does not much influence the vitamin D content of animal foods. Mattila et al. (84) found that, in eggs boiled for 10 min, the vitamin D-3 concentration was 1–6% lower and 25(OH)-D-3 content was 6–11% lower compared with raw eggs. Also in fish, the cooking effect was moderate: baking various kinds of fish (e.g., perch, rainbow trout, Baltic herring) in the oven at 172°C or 200°C for 20 min induced a vitamin D-3 loss of <10%, calculated on a dry matter basis. Only 1 lot of Baltic herring showed an exceptionally large decrease of 23%, which was attributed to the loss of fat during baking (84). Another investigation reported a loss of ∼50% when salmon was fried in vegetable oil but not when it was baked (74). Cooking pork loin in the oven at 250°C for 20 min followed by 150°C until meat core temperature reached 80°C significantly increased vitamin D-3 and 25(OH)-D-3 content in all parts, presumably due to water loss and hence increased dry matter content (35). However, calculating the true retention for vitamin D-3 and 25(OH)-D-3 in the whole cut shows losses of 23% and 5%, respectively. Bennink and Ono (85) reported that for beef, 35–42% of vitamin D was lost with cooking. Purchas et al. (34) investigated the impact of several cooking procedures on vitamin D-3 and 25(OH)-D-3 content in various beef and lamb cuts. Vitamin D-3 retention in beef ranged from 79% to 101% and in lamb from 75% to 126%; retention of 25(OH)-D-3 in beef was 77%–130% and in lamb 55%–79%. In beef cuts, longer, slower cooking induced higher losses than rapid cooking. Again, water loss caused higher vitamin D-3 and 25(OH)-D-3 levels in cooked beef samples, and also in lamb, the concentrations tended to increase with cooking (34). Montgomery et al. (31, 32) as well found increased vitamin D-3 and 25(OH)-D-3 concentrations in cooked (71°C internal temperature) longissimus steak, which was attributed to moisture losses.

Storing eggs at room temperature for 2 and 3 wk only leads to slight vitamin D-3 and 25(OH)-D-3 decreases (<6% on a dry matter basis) (84). Renken and Warthesen (86) investigated vitamin D stability in fortified skim milk and found some losses through exposure to light but not to air. Thermal stress like pasteurization, ultra heat treatment, sterilization, or even spray drying does not provoke a significant loss of added vitamin D in milk (87, 88).

Conclusion

Studies focusing on the determination of the natural vitamin D content in different animal foods are limited. Most of the data derive from the development of new methods of analysis or from experiments studying the influence of feed supplementation. Although we tried to concentrate on products from animals without excessive vitamin D supplementation, often the information about the upbringing of the animals is not available (especially in retail products). This makes it difficult to compare and judge the given results, and it may also be an explanation for the variations found. Besides this, varying fat content of the products as well as other season of production may also result in different concentrations of vitamin D. The highest values of vitamin D are found in fish and especially in fish liver, ranging from <2 μg/kg to 477 μg/kg and up to 1200 μg/kg, respectively, depending on fish species and locations. Also offal provides considerable amounts of vitamin D up to 140 μg/kg, whereas the content in muscle meat is generally much lower (up to 10 μg/kg). Variations between species and meat cuts are seen. With vitamin D concentrations of up to 57 μg/kg egg yolk features values between the vitamin D values of meat and offal. Milk and dairy products are normally low in vitamin D if they are not fortified with it. The highest natural values are reported in butter and cheese (up to 10 μg/kg) due to its high fat content.

Processing does not influence the concentration of vitamin D in meat and dairy products very much because the vitamin is rather heat and oxygen tolerant. However, exposure to light can significantly reduce vitamin D content.

Because recommendations for vitamin D intake have recently been increased considerably, the possibility to cover the requirements with foodstuff is even more difficult. Nutrition societies often recommend an intake of 3 portions of dairy and 1 portion of meat, fish, or eggs per day. We estimate that by complying with these recommendations, the maximal intake of vitamin D through animal food would be 3 μg (dairy plus meat), 7 μg (dairy plus eggs), and 49 μg (dairy plus fish) per day.

Further research is needed to improve and optimize the natural vitamin D content in dairy products and meat because fortification of food is not well accepted in several countries.

Acknowledgments

Both authors read and approved the final version of the paper.

Footnotes

²Abbreviations used: 25(OH)-D, 25-hydroxyvitamin D [25(OH)-D-2 and 25(OH)-D-3]; 25(OH)-D2, 25-hydroxyergocalciferol; 1,25(OH)₂-D-3, 1,25-dihydroxycholecalciferol; 25(OH)-D-3, 25-hydroxycholecalciferol; UHT, ultra heat treated; vitamin D-2, ergocalciferol; vitamin D-3, cholecalciferol.

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Is Vitamin D Present In Milk

Source: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3941824/

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