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Supply with vitamin D

The vitamin D you have got in your body can come from food or from the sun. Vitamin D is also known as “sunshine vitamin”, because it is mainly produced in the skin of your own body. In contrast to all other vitamins, dietary vitamin D intake plays a minor role for a sufficient vitamin D supply, because vitamin D is found only in very few foods and not in sufficient quantities.

You cannot cover your daily requirement of vitamin D solely via food: In order to cover the daily requirement of vitamin D you would need to eat about 150g herring, 200g salmon, or 750g tuna. Every day!

Only 10-20% of the required vitamin D comes from diet and the rest is synthesised in your skin. A sufficient amount of vitamin D is only produced if a large part of your body surface is exposed to the sun, mainly whilst sunbathing. In order to produce enough vitamin D for the whole year, you need about 30 sunbathing sessions, which lead to a slight redness of the skin the day after.

A strict food exclusion diet can be challenging. As long as you are cooking for yourself you can succeed in entirely avoiding the foods you do not tolerate. But there are some food intolerances that involve substances which are found in many different foods, for example histamines. Another issue is processed foods. I am not talking only about ready-made meals and fast-foods, but also processed foods like mayonnaise or mustard.

By the way, you hardly produce any vitamin D in the solarium. In order to produce vitamin D, the UVB rays of the natural sun are needed.

Lack of vitamin D

Worldwide, people lack sufficient vitamin D in their blood. Due to the changing lifestyle, the computer age and the sometimes high levels of air pollution in large cities, many people are no longer staying outdoors long enough to be able to produce sufficient vitamin D via the skin. Based on the criteria of the US Endocrine Society, 88% of people worldwide have an insufficient vitamin D status.

There are various reasons why people lack vitamin D. People at risk of vitamin D deficiency spend few time outside, often use sunscreens with a high sun protection factor, or have naturally dark skin. There is often a lack of vitamin D in the elderly and overweight people. One reason for the dramatic increase in osteoporosis – especially in older women – might well be the fact that so many people lack sufficient vitamin D in their blood.

What is vitamin D deficiency?

Unfortunately, there is no internationally agreed definition of vitamin D deficiency. In 2013, the scientist around Paul Lips classified vitamin D deficiency in 2013 as follows:

• severe deficiency (<12.5 nmol/L)
• deficiency (12.5-25 nmol/L)
• insufficient (25-50 nmol/L)
• sufficient (> 50 nmol/L)

The US Endocrine Society (ES) defines vitamin D deficiency as having blood levels below <50 nmol/L, values below <75 nmol/L are not sufficient, and values between 75-250 nmol/L are sufficient.

Vitamin D blood levels and sufficient supply

Official recommendations

According to the recommendation of the German Nutrition Society (DGE), the vitamin D blood level should be at least >50 nmol/L (equals >20 ng/ml). International experts in the field believe that an optimal vitamin D blood level should be way higher than that, between 100-150 nmol/L (equals 40-60 ng/ml). The US Endocrine Society even recommends even higher vitamin D blood levels in the range of 75-250 nmol/L.

Taking into account the results of numerous studies on the beneficial effects of vitamin D, it becomes clear that one should have at least a blood level of >75 nmol/L (equals >30 ng/ml) to be optimally supplied with vitamin D. Considering the recent data from McDonnell et al., one should reach a blood level of> 100 nmol/L (equals 30 ng/ml), because this can further lower the risk of developing cancer by more than> 65%, compared to values below <50 nmol/L.

What is the optimal vitamin D blood level?

In order to ensure an optimal supply of vitamin D, a blood serum concentration of >75 nmol/L (>30 ng/ml), preferably between 75-150 nmol/L (30-60 ng/ml), should be achieved as a target range.

It is important to know that vitamin D has a large therapeutic range and toxic effects of vitamin D are only to be expected at values above >450 nmol/L (>180 ng/ml). That means overdosing can be avoided easily.

Vitamin D supplementation

From the above stated, it is very clear that in order to achieve an optimal vitamin D supply you either need to sunbath regularly (at least 30 times per year in the summer month) or take vitamin D supplements.

Because people are no longer staying outdoors long enough to be able to produce sufficient vitamin D via the skin, international experts recommend an additional supplementation of vitamin D.

Official recommendations on vitamin D supplementation

Since 2012, the German Nutrition Society (DGE) has recommended a daily oral intake of 800 IU (International Units, 800 IU = 20 μg) of vitamin D for people who are not exposed to the sun and need to meet their total vitamin D needs through diet.

Especially people who are rarely outdoors, people with dark skin and older people could be dependent on a vitamin D supplementation according to the DGE. According to the DGE, newborns should receive vitamin D supplementation for first-year rickets prevention. For infants, the DGE recommends the administration of a vitamin D tablet from the first week of life until the end of the first year of life and in the second year of life during the winter months.

However, experts claim that supplementing only 800 IU is hardly sufficient to maintain an optimal vitamin D blood level. Importantly, 800 IU are nowhere near what´s needed to compensate a vitamin D deficiency.

The US Endocrine Society (ES) considers general vitamin D supplementation to be useful and necessary. The ES makes clear and diversified recommendations for vitamin D supplementation in their guidelines.

The ES recommends 400-1,000 IU (International Units, 1,000 IU = 25 μg) of vitamin D daily in children up to 18 years of age, and 1,500-2,000 IU of vitamin D daily in adults. In certain cases (obesity, certain medications) 2-3 times the amount of vitamin D is necessary.

If there is a marked vitamin D deficiency (<75 nmol/L), up to 4,000 IU per day may be required in children and up to 10,000 IU per day in adults, to achieve a sufficient vitamin blood level in the range of 75-250 nmol/L.

In case of severe vitamin D deficiency the ES even recommends taking up to 50,000 IU of vitamin D per day, in order to quickly compensate this severe lack of vitamin D.

Vitamin D fortified food

In Canada, Finland, Sweden and the USA dairy products and other foods are fortified with vitamin D. In the US and Canada this has led to a significant increase in vitamin D blood levels in the population, but still 40-60% of the population are having an insufficient vitamin D blood level below <50 nmol/L (< 20ng/ml).

Whether an enrichment of foods is also be advisable for countries such as Germany remains a matter of debate. I think it is a necessity in all industrialised countries and in countries that are in the upper northern hemisphere.

Read more about vitamin D blood tests here