Longevity Briefs: Do Vitamin D Supplements Work In Practice?

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: Vitamin D is an important micronutrient when it comes to bone health, the immune system, and various other functions. The body can make vitamin D when the skin is exposed to sunlight, but it can also come from food sources like fish and eggs. Research suggests that many of us don’t get as much of it as we should, and that vitamin D supplements can help make up what’s missing, especially in the winter months. However, whether supplements actually have a meaningful impact outside of clinical trials has been a matter of debate.

What did the researchers do: In this study, researchers looked at data from 445,601 participants of the UK Biobank, with ages ranging from 40 to 73. They looked at whether participants took vitamin D supplements or not, whether they had vitamin D deficiency or insufficiency (insufficiency refers to low levels of vitamin D that do not necessarily cause bone disease, but may increase the risk of other diseases). They investigated whether there was a relationship between vitamin D supplementation and reduced mortality.

Key takeaway(s) from this research: About 21.0% of participants had vitamin D deficiency, while 34.3% had insufficiency. About a quarter of participants reported regularly taking vitamin D, either by itself or as part of a multivitamin supplement. These individuals had statistically significantly higher median (a type of average) vitamin D levels than those not taking supplements. Taking vitamin D reduced risk of deficiency by around 80% and insufficiency by around 50%, with vitamin D alone proving slightly more effective than multivitamins.

During a period of around 12 years, use of vitamin D and multivitamins were associated with a 10% and 5% reduction in mortality, respectively, after researchers controlled for confounding variables such as age, skin tone and socio-economic status. It was also associated with an 11% reduction in cancers and a 29% reduction in respiratory diseases. Cardiovascular diseases were also 11% lower, but this wasn’t enough to be statistically significant.

This is the largest study of its kind to date, and suggests that vitamin D is at least as effective at reducing mortality in the general population as it is has been in clinical trials. The researchers’ measures to control for confounding variables were thorough, though no observational study is immune to confounders. The UK biobank is voluntary and therefore isn’t a random sample of the UK population, with participants likely to be slightly healthier than average. Participants weren’t required to report the dose of vitamin D they were taking, which would have been useful information. Nevertheless, these are encouraging results for the effectiveness of vitamin D supplementation outside of clinical trials.