Long touted as a key to improved cardiovascular health, increased cognition, and other benefits, omega-3 supplements are facing increasing scrutiny over whether they work as advertised. If recent critical investigation is correct, you might be enduring fish burps for little to no benefit.

Reviewing the new book The Omega Principle by Paul Greenberg in Slate, Irineo Cabreros breaks down the dilemma facing the $15 billion omega-3 supplement industry. A recent meta-analysis that looked at 79 studies involving more than 100,000 subjects found that omega-3 consumption had virtually no effect on common heart conditions. An earlier examination of studies compiled in 2012 also found that supplementing with omega-3s had no impact on whether a person died as a result of a cardiac event. Consumption also had no impact on overall mortality. Studies that have looked at fish oil’s benefits when it comes to psychiatric conditions like depression have been similarly inconclusive.

So why do we believe omega-3s are synonymous with better health? The notion originally stemmed from research into an Inuit population in Greenland in the 1970s. The Inuit had low incidences of heart problems and ate a lot of fatty fish. The conclusion was that their oily fish-based diets had protective effects on the heart. Ever since, supplement companies and consumers have associated fish oil, in liquid or capsule form, as having a host of cardiovascular benefits. But more contemporary research illustrates that the Inuit might simply metabolize their fish-heavy diet differently, leading to effects that can’t necessarily be replicated in a general population.

While fish oil may not improve heart health, it’s not likely to do you any harm. Unfortunately, the same may not hold true for the environment. According to Greenberg’s book, supplement companies typically draw the raw material for their products from large quantities of forage fish that are captured for their oil and agricultural value as fertilizer and animal feed—up to 27 tons annually. Forage species like anchovies and krill play a key role in the aquatic ecosystem: As prey species, they transmit solar energy from plankton to larger carnivorous fish. If companies continue to winnow their population, it’s possible their absence could have unintended and unpredictable effects on food chains. Greenberg argues that continuing to weaken fish populations for supplements of dubious value may be something we’ll come to regret.

In the meantime, one thing experts can agree on is that eating actual fish is good for your body. The American Heart Association recommends eating two 3.5-ounce servings of fish like salmon, mackerel, herring, and albacore tuna weekly.

[h/t Slate]