Omega-3 supplements are once again stirring up controversy. The latest recommendation, highlighted in guidelines released on July 20 by six organizations including the American Heart Association and the American College of Cardiology, suggests that omega-3 supplements hold no benefit for patients with chronic coronary artery disease. While many omega-3 supplements incorporate a blend of DHA and EPA, only a single drug derived specifically from EPA has demonstrated the capability to mitigate the risk of cardiovascular disease or mortality. This is a prescription drug in the U.S. but is not yet available in Korea.

However, even these encouraging outcomes related to omega-3s are not exempt from criticism due to potential flaws in the experimental setup. Rather than witnessing a risk reduction in cardiovascular incidents within the omega-3 group, it is plausible that the group receiving the placebo mineral oil inadvertently experienced an escalation in cardiovascular event occurrences. This phenomenon could have given a misleading impression of the drug's efficacy. The scientists hypothesize that the placebo mineral oil might have hindered the absorption of statin drugs used to treat hyperlipidemia, thus diminishing their effectiveness and subsequently heightening the risk of cardiovascular events beyond the anticipated norm for the placebo group.

Omega-3 supplements aren't alone in their lack of efficacy. Vitamin C, vitamin D, vitamin E, beta-carotene, and calcium have similarly fallen short in demonstrating notable benefits. There exists no substantive evidence to support the notion that these supplements can effectively reduce the risk of cardiovascular disease. There's an important thing to remember here. Food is usually the starting point for these studies. And most of these studies are limited by the fact that they are observational. The idea that omega-3 supplements lower cardiovascular risk comes from the fact that people who eat a lot of fatty fish seem to have a lower risk of cardiovascular disease.

But the challenge is that these observations alone do not provide a clear picture of cause and effect. Is the difference between people who eat a lot of fish and those who eat very little fish solely attributed to the amount of fish consumed, or are there other factors involved? While scientists try to account for these variables, known as confounders, completely eliminating them is nearly impossible. To establish cause and effect, the first step is to identify the differing nutrients in the diets of fish enthusiasts and non-consumers. If it comes down to omega-3 fatty acids, a clinical trial is necessary. In such a trial, one group would receive an omega-3 supplement, while the other would get a placebo, allowing us to determine if a causal relationship exists.

The results of extracting specific ingredients from foods and studying them in humans are often disappointing, and even when they do work, they're not very powerful, so they're always controversial. Heed the advice that your whole diet is more important than a specific food or single nutrient.

Jeong Jae-hoon is a food writer and pharmacist. He covers a variety of subjects, including trends in food, wellness and medications. This column was originally published in Korean in Joongang Ilbo on Aug. 17, 2023. – Ed.