Vitamin D supplements do not protect against heart attack or stroke, according to researchers, although they may protect against heart failure in older individuals.
The research team, led by Dr. John Ford of the Norwich Medical School at the University of East Anglia, recently published their findings in The American Journal of Clinical Nutrition.
Numerous studies have suggested that vitamin D deficiency may increase the risk of an array of health problems, such as asthma, diabetes and cardiovascular disease, and many studies claim vitamin D supplements can reduce these risks.
But such findings have been met with some criticism. In January this year, research published in The Lancet Diabetes & Endocrinology questioned the benefits of vitamin D supplementation, claiming it does not reduce the risk of heart attack, heart disease, stroke, cancer or bone fractures.
"The main message is that if you are otherwise healthy and active, you are likely to receive enough sunshine to have adequate vitamin D levels and don't need to take vitamin D supplements," study leader Dr. Mark Bolland, of the University of Auckland in New Zealand, told Medical News Today.
Dr. Bolland collaborated with Dr. Ford for this latest study, which specifically investigated the effects of vitamin D supplementation on the occurrence of cardiovascular events and outcomes.
Relationship between vitamin D deficiency and cardiovascular disease 'not causal'
To reach their findings, the team analyzed the data of a clinical trial involving 5,292 individuals aged 60 and over. In this trial, participants were given a daily vitamin D supplement or placebo every day for 5 years. They assessed the occurrence of cardiovascular events and mortality among participants.
In addition, they assessed 21 randomized controlled trials involving 13,033 people. These trials looked at subjects' vitamin D intake and cardiovascular outcomes.
From their analysis, the team found that taking vitamin D supplements does not appear to protect against heart attack or stroke.
Dr. Ford says these findings suggest that the link between vitamin D deficiency and increased risk of cardiovascular disease is not causal:
"Several observational studies have provided evidence that cardiovascular patients tend to have lower circulating concentrations of vitamin D but we have shown that this is not a causal relationship. Instead, vitamin D levels may be a marker for other risk factors, such as a sedentary lifestyle."
The team notes that there was some evidence, however, that vitamin D supplementation protects against heart failure in older individuals; they found a lower risk of dying from cardiac failure among seniors who took a daily supplement. But Dr. Ford says "there needs to be further research into whether a supplement could be beneficial" among this population.
Earlier this year, a study led by the Columbia University Medical Center in New York, NY, claimed that vitamin D supplements do not reduce depression, while other research published in JAMA suggested that the supplements do not improve asthma symptoms or treatment.