“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 Cancer
DISAPPOINTMENT 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.
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.
For 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 least 75 nmol/L (30 ng/mL).
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.
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.
