Digging into vitamin D


By Leanne McCrate



Dear Dietitian,

I recently read an article that said vitamin D protects against heart attacks. However, I have read several other articles that said the opposite. It’s frustrating, and I don’t know what to believe!

Sam

Dear Sam,

Let me begin by saying I understand your frustration when it comes to contradictory nutrition studies. It can be confusing for consumers as well as health care professionals. The science of nutrition is still in its infancy, and especially with nutrition and disease prevention, we are still finding our way. Discoveries are being made, but remember, one study is not definitive.

Vitamin D is found in two forms: vitamin D2 (ergocalciferol) and D3 (cholecalciferol). Vitamin D2 is found in mushrooms and fortifies foods like milk, yogurt, and cereals. Vitamin D3 is found in fatty fish, such as salmon and rainbow trout, egg yolks, and fish oils. Getting too much vitamin D is possible since it is stored in body fat, but this is rare unless taking supplements. The Recommended Daily Allowance (RDA) for vitamin D is 600 IU (international units) if you are seventy years or younger, and 800 IU daily for people over seventy. Talk to your doctor before taking any dietary supplement.

The primary function of vitamin D is to lay calcium to the bones, thereby strengthening them. Our bodies can manufacture this vitamin through sunlight exposure, but the amount produced varies. Those with darker skin do not absorb as much sunlight as people with lighter skin, and sun exposure is vital for vitamin D production.

Several observational studies have linked vitamin D deficiency to an increased risk of heart disease. Therefore, it is logical to think that increasing vitamin D levels through supplementation would correct the problem. However, studies failed to prove this link. Vitamin D supplementation has shown only a modest or neutral effect on the risk of heart disease.

A recent study published in the Journal of Human Nutrition and Dietetics found a positive link between vitamin D-containing foods and reduced risk of heart disease. They discovered that men with the highest vitamin D intake from food had a reduced risk of heart disease. Interestingly, the same results were not found in women (1). This study was observational, which does not show cause and effect. However, it may point researchers in the right direction as to what to study further. More research is needed to better understand the impact of vitamin D on the risk of heart disease.

Until next time, be healthy!

Dear Dietitian

Reference

1. Kouvari, M, Panagiotakos, B, et al. Dietary vitamin D intake, cardiovascular disease and cardiometabolic risk factors: a sex-based analysis from the ATTICA cohort study. Journal of Human Nutrition and Dietetics, April 2020, Retrieved from https://doi.org/10.1111/jhn.12748

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By Leanne McCrate

Leanne McCrate is an award-winning dietitian based in Missouri. Her mission is to educate the public on sound, evidence-based nutrition. Do you have a nutrition question? Email her at deardietitian411@gmail.com.

Leanne McCrate is an award-winning dietitian based in Missouri. Her mission is to educate the public on sound, evidence-based nutrition. Do you have a nutrition question? Email her at deardietitian411@gmail.com.