A large-scale meta-analysis of 884 studies, published in the Journal of the American College of Cardiology, broke down evidence supporting 27 different micronutrients for their roles in promoting cardiovascular health.
 
They also identified several micronutrients which don’t appear to offer any benefit or might even have a negative effect. In the combined studies, the review involved data from over 883,000 participants, with a combined 4,895,544 person-years.
 
“For the first time, we developed a comprehensive, evidence-based integrative map to characterize and quantify micronutrient supplements’ potential effects on cardiometabolic outcomes,” said Simin Liu, MD, MS, MPH, ScD, professor of epidemiology and medicine at Brown University and a principal investigator for the study. “Our study highlights the importance of micronutrient diversity and the balance of health benefits and risks.”
 
These findings could be used as the basis for future clinical trials to study specific combinations of micronutrients and the impact on cardiovascular health, said Liu.
 
According to the authors, antioxidant supplements have long been thought to play a role in heart health because they reduce oxidative stress, and heart-healthy diets such as the DASH and Mediterranean diet are antioxidant-rich. However, the results included in this review suggest inconsistent performances from different kinds of antioxidant supplements, which is why antioxidant supplementation isn’t widely recommended in mainstream cardiology.  
 
The researchers looked at randomized, controlled interventions evaluating 27 types of nutraceuticals in diverse populations. They evaluated primary outcomes including cardiovascular mortality, myocardial infarction, systolic and diastolic blood pressure, stroke, and more.
 
 They found strong evidence that omega-3 fatty acids decreased mortality from cardiovascular disease, while folic acid supplementation appeared to lower stroke risk, and CoQ10 was linked to decreases all-cause mortality.
 
Omega-6 fatty acid, L-arginine, L-citrulline, magnesium, zinc, alpha-lipoic acid, melatonin, catechin, curcumin, flavanol, genistein, and quercetin also showed moderate- to high-quality evidence of reducing cardiovascular disease risk factors across the range of studies.
 
However, vitamin C, vitamin D, vitamin E, and selenium showed no effect on long-term cardiovascular disease outcomes or type-2 diabetes risk. Beta carotene supplements increased all-cause mortality in the review, the authors concluded.
 
“Research on micronutrient supplementation has mainly focused on the health effects of a single or a few vitamins and minerals,” Liu said. “We decided to take a comprehensive and systematic approach to evaluate all the publicly available and accessible studies reporting all micronutrients, including phytochemicals and antioxidant supplements and their effects on cardiovascular risk factors as well as multiple cardiovascular diseases. Identifying the optimal mixture of micronutrients is important, as not all are beneficial, and some may even have harmful effects.”