Do vitamin D supplements work, or are they just another way for businesses to make an easy buck?

This video was originally published on NutritionFacts.org and republished with permission. Original post here. 

Correlation is not causation. It is a mantra that is repeated over and over in the scientific community and it is an important one. Coincidences are everywhere in life, and sometimes we mistake these coincidences for links between things that aren’t really there. This may very well be the case for vitamin D supplements. Let’s be clear, vitamin D is hugely important. Receptors for this substance can be found in almost all parts of the body and exposure to it can alter the expression of certain genes.

It is also a bit of an inaccuracy to label it a vitamin, as by definition a vitamin is something that we need to ingest because our bodies cannot produce it. But our bodies do produce vitamin D in the presence of sunlight. Supplements in general are big business, but when scientists make observational studies (that is to say studies where subjects are simply measured and not actually tested) they are simply relying on correlation to support their claims. We know that correlation is a scientifically shaky foundation to build a case upon, yet it happens all the time.

Studies like these fail to consider important factors. For example, we know that our bodies are capable of producing vitamin D in the presence of sunlight, and when studies examine the health of those with high levels of vitamin D in the bloodstream, they often fail to address the fact that those people are likely already following a more health conscious lifestyle. People who have plenty of vitamin D are more likely spending more time in the sun, meaning they’re outside and more likely to be moving or exercising rather than sitting at a desk under a fluorescent lamp. When vitamin D supplements are tested in those with low levels of the substance, beneficial results come up short. Time and time again they have no effect on weight loss, artery function or prevention of any disease. The only real way to get vitamin D is to produce it yourself, so get out there this summer and enjoy some sun!