Nutritional supplements and dietary interventions provide little to no protection against cardiovascular disease or death, according to a new review of research published Monday in the Annals of Internal Medicine. One even showed negative effects.
Lead author Safi Khan told Bloomberg News that supplement manufacturers have long persuaded consumers to purchase their products with marketing tactics and biased data. "Do not waste your money on these over-the-counter multivitamins and nutritional supplements, because if you are using them with the belief that they are going to reduce your mortality or improve your cardiovascular health, they don't."
The evidence review analyzed 16 supplements and eight dietary interventions (such as reduced-saturated-fat diets) from 277 trials of nearly 1 million people but called for further research on the issue. Some results contradicted previous studies, and the confidence level about the conclusions drawn about certain supplement effects is not high.
Not all supplements and diets are worthless, the review found. Folic acid supplements reduce the risk of a stroke, and omega-3 fatty acids were linked to reducing myocardial infraction (MI) and coronary heart disease. A reduction in salt intake, which reduces blood pressure, was found to reduce mortality rates in all patients. Mediterranean and vegetarian diets are listed under U.S. dietary guidelines for healthy eating, but did not have a significant effect on mortality or cardiovascular outcomes in the review of research.
The only supplement to show signs of a negative impact with any sort of confidence was calcium plus vitamin D, which is linked to a greater chance of stroke, according to the study. Other research has associated calcium supplements with an increased risk of MI and death from cancer. The remaining 13 supplements studied showed no benefit or harm.
Supplement use is on the rise in the U.S., where nearly 3 in 4 people take at least one such product, according to the report. The industry is expected to grow to $300 billion in the next five years. U.S. Food and Drug Administration guidelines do not recommend the routine use of any dietary supplements to reduce the risk of chronic disease. The agency does not approve such products before they are sold to the public; it merely reacts to reports of adverse events stemming from their use.