Dietary supplements of minerals, vitamins and antioxidants are commonly taken by adults to maintain or improve various aspects of health. Previous research has found that 49 of adults in the U.S. report using dietary supplements, with less than a quarter of these being prescribed by a physician. Many adults take supplements that purportedly improve cardiovascular health, as heart disease remains the leading cause of mortality across both sexes and all races and ethnicities in the United States. However, the value of these supplements is debated by the scientific community.
We need to ingest vitamins and minerals in our diets, since we cannot make most of them ourselves. And it is well known that deficiencies in micronutrients lead to clinical diseases, so it is natural to assume that supplementing these substances will be beneficial to health. However, the question of whether individuals without deficiencies would benefit from supplementation has been the subject of innumerable investigations that have produced inconclusive results. The U.S. Preventive Services Task Force (USPSTF) states that the current evidence for use of multivitamins or other nutrient supplements to prevent cardiovascular diseases is insufficient.
In a new study published in the Journal of the American College of Cardiology, researchers have now reviewed 884 scientific investigations on the efficacy of micronutrient supplementation to reduce cardiovascular risk. In total, more than 883,000 patients were involved in the combined studies, which provide some clarity on the micronutrients that may be of benefit in preventing heart failure.
“For the first time, we developed a comprehensive, evidence-based integrative map to characterize and quantify micronutrient supplements’ potential effects on cardiometabolic outcomes,” said Dr. Simin Liu, 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.”
The development of heart disease has previously been associated with oxidative stress in heart tissue. This implies that the production of reactive oxygen species (free radicals) during metabolic processes is not balanced by the body’s natural antioxidant enzymes that “mop up” the free radicals. This has led to the idea that antioxidant supplementation may assist in maintaining heart health.
Heart-healthy diets, like the Mediterranean diet and the Dietary Approach to Stop Hypertension (DASH), feature foods that are naturally rich in antioxidants, such as amino acids, omega-3 fatty acids and vitamin C, but the results of investigate studies on their effects have been inconsistent.
“Research on micronutrient supplementation has mainly focused on the health effects of a single or a few vitamins and minerals,” said Dr. Liu. “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.”
In their meta-analysis, the researchers looked at the results of randomized, controlled intervention trials evaluating 27 different types of antioxidant supplements. They identified several micronutrients that do reduce cardiovascular risk, as well as others that offer no benefit at all, or even have a negative effect.
For example, there was strong evidence that omega-3 fatty acid supplementation decreased mortality from cardiovascular disease, while taking folic acid lowered stroke risk and coenzyme Q10, an antioxidant sometimes marketed as CoQ10, decreased all-cause mortality. Supplementation with omega-6 fatty acid, L-arginine, L-citrulline, Vitamin D, magnesium, zinc, alpha-lipoic acid, melatonin, catechin, curcumin, flavanol, genistein and quercetin also showed evidence of reducing cardiovascular risk.
However, supplements of Vitamin C, Vitamin D, Vitamin E and selenium showed no effect on long-term cardiovascular disease outcomes or on type-2 diabetes risk. And beta carotene supplements were actually associated with increases in all-cause mortality.
According to the researchers, the findings point to the need for more personalized, precision-based dietary interventions that involve specific combinations of beneficial supplements to suit each individual’s specific requirements. Further study is needed, including large, high-quality interventional trials to investigate the long-term effects of certain micronutrients on health.
“Identifying the optimal mixture of micronutrients is important, as not all are beneficial, and some may even have harmful effects,” said Dr. Liu.
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