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  • Writer's pictureNick Allen

Is vitamin D supplementation necessary?

I’m generally a supplement minimizer — someone of the opinion that a balanced diet focused on whole foods can provide for most of your nutritional needs. That being said, I’m willing to acknowledge the few exceptions. For example, I supplement EPA and DHA (Omega-3 fatty acids) daily, convinced of the role they play in preventing cardiovascular disease, Alzheimer’s, and more. Does vitamin D deserve a place on this list?


Let’s start by looking at our physiological need for vitamin D. It has long been known that vitamin D helps the body hold onto calcium and phosphorus, and thus it is essential for bone health. Rickets, a disease of skeletal deformities, used to be fairly common in children. It is now rare in the United States, almost certainly due to the fortification of milk, cereals, and more with vitamin D.


Beyond bone health, vitamin D has been credited with a role in cancer prevention, immune function, cognitive health, and more. There is conflicting data on these potential benefits, especially when it comes to benefits from supplementation specifically. A randomized control trial published in the New England Journal of Medicine (NEJM) in 2019 found that 2000 IU of supplemental vitamin D3 was not associated with a lower risk of either cancer or cardiovascular disease. Even with regards to bone health, a follow-up to the aforementioned NEJM study released this month found that the 2000 IU vitamin D3 supplement did not reduce the incidence of fractures in adults over age 50.


As always, there are two sides to this story. While the incidence of cancer may be unchanged by vitamin D supplementation, a 2019 review article published in the Annals of Oncology described a significant decrease in mortality from cancer in those taking moderate-dose vitamin D supplements. There also appears to be a link between low levels of vitamin D in the blood and multiple sclerosis, a rare neurological disease.


My interpretation of the evidence thus far is that vitamin D supplementation may not have a substantial impact on your lifespan or healthspan, but if taken in moderate doses (about 2000 IU daily) it is unlikely to cause harm. Only supplements in excess of 4000 IU are considered potentially dangerous. If you can afford it and don’t mind adding a pill to your daily regimen, I think that there is likely some, albeit modest, benefit. If you’re going to go this route, there are a couple of things to consider. First, vitamin D3 supplements seem to be superior to vitamin D2 in terms of bioavailability. Additionally, don’t be fooled into buying supplements with added sugar. Unfortunately, vitamins in their pure form shouldn’t taste great. The sugar from gummies will probably do enough harm to offset any good that comes from enhanced vitamin D levels, and thus it’s essential to stick with unflavored pills/capsules.


Figure 1: Dietary sources of vitamin D (NIH).


If you’re leaning against supplementation, you still want to make sure your lifestyle and dietary habits are keeping you out of vitamin D deficiency. Fatty fish and fortified milk are the greatest sources of dietary vitamin D (Figure 1), so if you’re vegan or your diet otherwise doesn’t include these items, you may want to consider supplementation. If you are eating these things, is it possible to get enough vitamin D through diet and sunlight to avoid rickets and other severe diseases? Certainly. Will it be enough to pursue some of the other benefits cited at higher doses? Probably not. But again, we’re still not certain that these benefits even exist, and if they do the magnitude of their impact is likely modest.


The most important thing by far is to stay out of vitamin D deficiency, which can be done through diet and adequate sun exposure. However, this may be difficult for some, in which case vitamin D3 supplementation is undoubtedly warranted. Not sure where you stand? A simple blood test can reveal your levels and help inform your supplementation decision.


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