My Head Is Going To Explode From Too Much Vitamin D Data

This yo-yo story is an embarrassment to medicine and science.

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The author owns the copyright to this photograph.

I am suffering from a case of Vitamin D supplement heart benefit whiplash. For years, we were told that having a normal to high-normal blood level of Vitamin would help prevent cardiovascular disease (CVD). There were no randomized controlled trials (RCTs) to answer whether this was true or not. RCTs were finally conducted, and the consensus was that they probably offered no benefit.

Now we are told with yet another study, “Not so fast, they are beneficial, and the prior studies were lousy.” Who and what to believe? And why can’t these people get this right? It’s not like we are asking them to solve the Russia-Ukraine war.

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Despite spending many hours in the sun fishing and gardening, my Vitamin D levels were low. All of my cover-up clothes and sunscreen may have contributed to this, as most of our Vitamin D is converted through the skin after exposure to sunlight. I had skin cancer once, and my mother had a history of melanoma. Thus, I was concerned with skin protection.

While sunlight is a primary source of vitamin D, dietary sources are also important, especially during periods of limited sun exposure. I have Crohn’s Disease, and it causes me not to absorb many vitamins, including D. Therefore, I have been on Vitamin D3 supplements for years. (Vitamin D comes in two forms: D2 and D3—D3 is thought to be more important in keeping blood levels normal.)

My physicians told me to take it. However, I was never convinced that my doing so would do much to prevent heart disease, especially after all of the negative RCTs showing no benefit. I have read and reviewed this latest study to save you the trouble of having to plow through and understand it. But don’t get too excited, as (spoiler alert) the answers remain elusive.

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The authors of the new study claimed that the RCTs were poorly designed. A few of their criticisms are well-founded. For example, some control groups (those without Vitamin D supplements) were allowed to take their own Vitamin D. Additionally, some RCTs treated people with normal levels, and therefore, benefits could not be observed, since the question of treating people with low levels to help prevent heart disease was not asked and therefore not answered. And finally, some trials used too low dosages of Vitamin D.

However, from these criticisms, the authors lost me. They claim that heart disease rates increase during the winter, when there is less sun exposure. It is essential to note that 80% of our vitamin D comes from skin conversion, while the remaining 20% comes from the food we consume.

If skin conversion due to sunlight is so important, then how do we explain that the rates of CVD are higher in the sunbelt than in the north? Perhaps many more heart attacks occur during the winter because unhealthy people are shoveling tons of snow, and living in the cold stresses the heart more than the heat.

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My Conclusion

I was always skeptical about taking Vitamin D supplements, even if my blood levels were low, and expecting it would prevent CVD because low levels were associated with more CVD. Remember, one of the axioms of epidemiology is “association does not equal causation.”

Thus, I was even less convinced of the data after the RCTs were published. (That’s called pre-results bias.) But I did not read all the RCTs in detail, and this latest study raises several good points. I remain skeptical and wish that better and newer RCTs had been conducted.

This may not be easy now, as the government's funding cuts to the NIH are now in place, and drug companies won’t sponsor these. Vitamin manufacturers have the funds, but why would they sponsor a study that might result in fewer sales of their product?

Although the exact benefit of treating “low Vitamin D blood levels” has yet to be determined, it is appropriate to ask, what is the risk? The answer is that it is very low. You can’t get toxicity from too much sunlight, and it is unlikely from eating too many Vitamin D-rich foods, like fatty fish, eggs, and fortified dairy. The only real cause is ingesting too high a dose of it as a supplement.

Most sources quote an upper dose of 800 units daily. Yet another study, showed safety with up to 5,000 units taken daily. I have had to take 2,000 units to get my blood level to be normal.

The bottom line is we still don’t know. We know that Vitamin D is necessary for our metabolism and to keep our bones strong and healthy. Vitamin D has also been shown to have anti-inflammatory properties, improve immunity, enhance muscle mass, and maybe stabilize mood.

It is unfortunate that the RCTs were not better designed. For now, if you want to take Vitamin D3 supplements, there is little risk of harm. However, it is recommended that you consult your doctor first, as it may interact with other medications.

I apologize for not making this clearer. The scientists have mucked this up. You may, or may not, prevent a heart attack by taking Vitamin D3 supplements if your blood level is low. The risk of taking it is low.

Finally, I would focus on more well-established and proven risk factor modifications, such as controlling diabetes, exercising regularly, maintaining ideal lipid levels, smoking cessation, and minimizing consumption of ultra-processed foods.