Data published in the British Journal of Nutrition indicated that supplementation with the sunshine vitamin was associated with reductions in heart attacks, stroke and cardiovascular death in overweight and obese people.
However, no significant effects were observed for non-overweight or obese individuals, reported scientists from the Hospital of Zhejiang People’s Armed Police and the Zhejiang Chinese Medical University in Hangzhou in China.
“Vitamin D should be recommended for overweight/obese people,” they wrote. “Vitamin D supplementation was also found to be potentially helpful in reducing the incidence of [myocardial infarction] in the general population.”
Vitamin D forms
Vitamin D refers to two biologically inactive precursors: cholecalciferol (D3) and ergocalciferol (D2). Both D3 and D2 precursors are transformed in the liver and kidneys into 25(OH)D, the non-active ‘storage’ form, and 1,25-dihydroxyvitamin D (1,25(OH)2D), the biologically active form that is tightly controlled by the body.
While our bodies naturally produce vitamin D when exposed to sunlight (UV-B radiation with a wavelength between 290 and 315 nm), the levels in some northern countries are too weak during the winter to trigger this process. Consequently, many people turn to dietary supplements and fortified foods as the most reliable sources of vitamin D during these months.
In addition, individuals with darker skin produce less vitamin D from sunlight due to higher levels of melanin, which reduces the skin’s ability to absorb UV-B rays. Various surveys have reported that up to 90% of African Americans may be vitamin D deficient, defined as having blood levels of 25(OH)D below 30 ng/mL.
Meta-analysis details
The Hangzhou-based scientists pooled data from five “high-quality” randomized controlled trials, which provided data on 57,201 subjects (29,019 receiving vitamin D supplements and 28,182 receiving placebo). Vitamin D doses ranged from 1,600 IU per day to 200,000 IU per month.
The results showed that, while there were no significant reductions in the incidence of stroke or cardiovascular death in the overall population, there was a trend towards a lower incidence of heart attack (myocardial infarction).
Focusing on overweight and obese individuals, the researchers found that vitamin D supplementation reduced the incidence of major adverse cardiovascular events (MACE) by 9%, compared to placebo.
The researchers noted that, to the best of their knowledge, this is the first meta-analysis to explore the relationship between major adverse cardiovascular events (MACE) and vitamin D supplementation and was based on studies published recently (between 2017–2023).
“Unfortunately, vitamin D supplementation did not have a significant protective effect for the entire population, but it is still worth continuing to study the effects for different populations,” they wrote, calling for more large, multi-center randomized clinical trials.
Source: British Journal of Nutrition, doi: 10.1017/S0007114525103954, “Effect of vitamin D supplementation for major adverse cardiovascular events: a meta-analysis based on randomised controlled trials”, Authors: X. Cheng, et al.
