People’s vitamin D requirement is individual, and guidelines should be revised accordingly

Vitamin D protects against infections, cancer, and many different diseases, but there is a widespread deficiency problem. Also, the official recommendations for vitamin D intake are very low and are no guarantee of having optimal blood levels of the nutrient. A new British study that is published in Clinical Nutrition sheds light on the problems involved with helping an entire population to reach optimal vitamin D status. Apparently, there is no one-size-fits-all because age, gender, skin color, BMI, diabetes, and other factors can affect our ability to synthesize vitamin D and utilize the nutrient.

The study was conducted at Trinity College Dublin in Ireland, and the scientists looked closer at vitamin D synthesis and utilization among white people, black people, and Asian people. The researchers used data from half a million people living in England, Scotland, and Wales (the UK Biobank) and calculated how the participants responded to UVB rays from the sun, which are needed in order to synthesize vitamin D from a cholesterol precursor that we have in our skin. At our latitudes, we can only make vitamin D during the summer period, when the sun sits sufficiently high in the sky. The type of vitamin D that we make from sunlight and get certain supplements is a precursor that is converted and stored in the liver as 25(OH)D, the type of vitamin D that is measured in blood samples. When different cells and tissues need vitamin D, 25(OH)D is converted again in the kidneys, in immune cells, and in other tissues into the active steroid form called calcitriol. Our vitamin D synthesis and utilization is therefore rather complex.
Vitamin D occurs naturally in oily fish, egg yolks, and high-fat dairy products. Although the amount of vitamin D we get from our diets is negligible, these food sources were also included in the study. The same was the case with multivitamins and vitamin D supplements.

The need for vitamin D varies from person to person – and some groups are vulnerable

The scientists observed that there were widespread problems with vitamin D deficiency, especially among people of color, which is because dark skin does not produce vitamin D as effectively as white skin does. The researchers say that their thorough analysis has given them a completely new understanding of vitamin D. First of all, it is a known problem that we only have a limited amount of strong sunlight in places like Great Britain and other countries at northern latitudes. In addition, we spend too much time indoors, sun awareness campaigns have made people afraid of the sun, and we tend to go overboard on our use of sun factor cream. Also, overweight individuals and old people do not synthesize vitamin D all that well. There are even studies suggesting that diabetics have difficulty with converting and activating vitamin D because of dysfunctions in their liver and kidneys. The team of researchers from Trinity College Dublin call for tailored recommendations for vitamin D that take things into account such as sun exposure, age, skin color, BMI, and other limiting factors. The study points to the fact that a one-size-fits-all approach will not guarantee that people have optimal levels of vitamin D in their blood.

• Vitamin D requirements vary from person to person
• Blood levels of vitamin D should ideally be higher than 75 nmol/L
• During the summer period when the sun sits high in the sky, a person with white skin can synthesize around 50-75 micrograms of vitamin D in 15-30 minutes
• In people with dark skin, the vitamin D synthesis is 6-10 times slower
• Ageing, being overweight, and having diabetes can impair your vitamin D synthesis
• People who are not out in the sun during the summer, and certain vulnerable population groups should take extra vitamin D all year round
• Vitamin D supplements with 20-100 micrograms of vitamin D are available
• References:

Margaret M. Brennan et al. Ambient ultraviolet-B radiation, supplements and other factors interact to impact vitamin D status differently depending on ethnicity: A cross-sectional study. Clinical Nutrition, 2024

Trinity College Dublin. New Study challenges one-size-fits-all approach to vitamin D supplementation guidelines.