“It is likely that vitamin D supplementation does not provide major health benefits, especially in populations where the vitamin D situation is already good at the start of the trial.”
This statement is the provocative observation of Dr. Jyrki Virtanen, a co-principal investigator of a recent study examining the effects of vitamin D supplementation in Finland.
Do you supplement with vitamin D? Today, we examine the evidence, focusing on a new randomized trial examining the effects of two doses of supplementation with the sun vitamin.
“Keep your face to the sun, and you will never see the shadows.”
― Helen Keller
Why do we need vitamin D?
We need vitamin D to absorb calcium and promote bone growth. Deficient levels can lead to soft bones in children, a condition known as rickets. In adults, insufficient amounts of vitamin D can cause fragile and misshapen bones or osteomalacia.
Did you know that vitamin D deficiency has been associated with depression, cardiovascular problems, and weight gain? Or that vitamin D deficiency has been associated with several cancers, including of the breast, colon, and prostate?What You Need to Know About Vitamin D and CancerDISAPPOINTMENT IS USUALLY associated with studies examining the use of supplemental vitamins or minerals to decrease…medium.com
To be clear, while people with higher vitamin D levels have a lower probability of these conditions, we have no proof that lack of vitamin D causes disease.
Moreover, we have no high-level evidence that vitamin D supplementation helps with most health-related problems I have cited, provided one does not have exceedingly low levels.
Vitamin D, heart disease, and cancer
There is abundant evidence (such as observational studies) that vitamin D deficiency is associated with nearly all major chronic diseases and mortality. But what about causality? We have little evidence from randomized clinical trials that improving vitamin D levels with supplementation reduces disease risk.
In this context, let’s turn to the Finnish Vitamin D Trial, a clinical study that explored the relationship between vitamin D, cancer, and cardiovascular disease. This randomized clinical trial ran from 2012 through 2018.
Here are the findings, published online January 4 in the American Journal of Clinical Nutrition. Note that most subjects had sufficient vitamin D levels at baseline and thus received higher than recommended doses of vitamin D during the study.
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The researchers analyzed data from 2,495 individuals. They included males 60 years or older and postmenopausal females, ages 65 or older. None had a history of cancer or cardiovascular disease.
The subjects took a placebo, vitamin D 1,600 international units (IU) daily, or 3,200 IU daily.
The subjects completed annual study questionnaires, and the researchers also had access to national registry data. A representative subgroup of 551 participants did in-depth, in-person interviews.
Fot this subgroup, the average vitamin D concentration was 75 nmol/L (30 ng/mL) at baseline; 91 percent had levels under 50 nmol/L (20 ng/mL) and 50 percent had concentrations of at lease 75 nmol/L (30 ng/mL).
Vitamin D — No cancer or cardiovascular upside
The results?
Compared with the placebo, neither dose of vitamin D reduced the incidence of cancer or cardiovascular disease.
Study co-lead investigator Dr. Virtanen adds color to the results, exclaiming that “It is likely that vitamin D supplementation does not provide major health benefits, especially in populations where the vitamin D situation is already good at the start of the trial.”
These high initial levels are likely the product of implementing policies to fortify foods with vitamin D in Finland, which began in 2003–2011.
Those who might benefit from vitamin D Supplementation — that is, those with low vitamin D levels — were a small proportion of the study population.
Is there no good news from the study? The study did offer this: The study group had lower cancer, and cardiovascular disease incidences than the national statistics gathered before national vitamin D fortification began.
Vitamin D, heart disease, and cancer — My take
The researchers used two vitamin D doses to find a dose-response effect over five years. Despite relatively large doses, vitamin D supplementation did not lower the incidence of cancer or cardiovascular disease.
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Supplementation may benefit those who live at northern latitudes (or spend little time outdoors), where we cannot make much vitamin D from sunlight. I would love to see a randomized trial including only those with low levels of vitamin D. I would like to see a much more extended follow-up period in an ethnically diverse population.
In the future, the researchers look forward to publishing other results from the Finnish Vitamin D Trial, for example, effects on heart arrhythmias, type 2 diabetes, falls and fractures, infections, pain, and mood changes.
Thank you for joining me today.