Many vitamins, minerals, or supplements—and dietary changes—are of little benefit in improving heart health, according to a systematic review by investigators from Johns Hopkins University. Published in Annals of Internal Medicine, the report did identify two supplements and one dietary measure that may help.
For the study, the researchers analyzed data from a total of 277 trials represented in nine systematic reviews and four randomized controlled trials. Twenty-four different interventions were assessed in that literature in nearly 1 million people. The vitamins and supplements included antioxidants; beta-carotene; vitamin B complex; multivitamins; selenium; vitamin A; vitamin B3/niacin; vitamins C, E, and D alone; calcium alone and with vitamin D; and folic acid, iron and omega-3 fatty acid. Diets included a Mediterranean diet, reduced saturated fat, modified dietary fat intake, reduced fat reduced salt in healthy people and those with hypertension, increased alpha linolenic acid, and increased omega-6 fatty acid. Each intervention was also ranked based on strength of the evidence.
The authors found that a low-salt diet decreased risk of death by 10% in people without hypertension and by 33% in those with hypertension. Use of omega-3 fatty acid supplements was associated with an 8% reduction in heart attack risk and 7% reduction in coronary heart disease risk compared with that seen in individuals not taking the supplements. Folic acid was associated with a 20% reduction in risk of stroke in healthy individuals. In contrast, calcium with vitamin D was associated with a 17% increase in risk of stroke, but taking either calcium or vitamin D alone was not associated with any health risks.
The researchers acknowledged that the level of evidence for benefits of a low-salt diet and detriment of calcium plus vitamin D was moderate, whereas the level of evidence for benefits of omega-3 fatty acid supplements was low. The data on folic acid were from studies done in China, where cereals and grains are not fortified with the vitamin.