Pharmacists want to do right by their customers. In the field of supplements, a plethora of claims, reviews, and studies with conflicting recommendations make it increasingly challenging to know what to advise.

At the same time, consumers want and need better information. Nearly three-quarters of U.S. adults report taking some kind of supplement, a rate that has driven the supplement industry to an estimated $32 billion this year.

A recent article in the Annals of Internal Medicine provides some much-needed guidance. The study focused on the effect of various supplements on overall mortality and heart health, an area of keen interest to many middle-aged consumers, particularly those with hypertension, high cholesterol, and other chronic cardiovascular issues.

The study included nine recent systematic reviews and four new randomized, clinical trials, for a total of 277 trials of 24 supplements and diets in 999,129 individuals. The researchers generated 105 meta-analyses from the data to better understand the impact of supplements and dietary interventions on cardiovascular outcomes.

The study produced some surprising results. Most supplements did nothing to protect against heart attacks or stroke or reduce the risk of death from cardiovascular disease. Those shown to have no significant effect included vitamins A, B, C, and E, beta-carotene, calcium, multivitamins, antioxidants, and iron.

Some supplements actually increased the risk. Combining calcium and vitamin D, for instance, increased the risk of stroke 17%.

On its own, vitamin D appeared to have no effect, but a previous study from Johns Hopkins School of Medicine found that calcium supplements increased the risk of developing arterial plaque by 22%. Calcium from dietary sources, however, reduced the risk of arterial deposits by 27%.

Only two supplements were found to actually improve heart health—omega-3 fatty acids and folic acid. The researchers determined that omega-3 long-chain polyunsaturated fatty acids, such as those found in fish oil and supplement capsules, reduce the risk of heart attack by 8% and the risk of coronary heart disease by 7%.

Folic acid cut the risk of stroke by 20%, but the authors noted that the results appeared to be driven by positive outcomes in China, which has high levels of folic acid deficiency. In the U.S., many foods already have folic acid added.

The two supplements outperformed common dietary interventions aimed to improve cardiovascular health. The study found that neither a low-fat diet nor the Mediterranean diet provided heart benefits. 

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