A few years ago, for reasons I can’t quite explain, I got into the habit of popping an omega-3 capsule every morning. I had never read a scientific article about the medical benefits of the supplement—I had never even looked for one. I just had an amorphous notion that this translucent orb of amber oil squeezed from the gland of a happy salmon was good for me. To be honest, I don’t think I could have even told you what they were supposed to do.

Which also seems to be the growing consensus among experts. A recent meta-analysis of 79 randomized controlled trials following more than 100,000 participants added to the growing corpus of non-findings. The study catalogued a litany of heart conditions for which omega-3s appear to have “little or no effect,” challenging the oldest and most important claimed benefit of the supplement—that taking it promotes heart health.

It’s conceivable that the immense amount of research invested in omega-3s (much of which is funded by the multibillion-dollar omega-3 industry itself) will one day make a compelling case for the supplement. But as it stands, the industry is in an awkward position. It’s not just that the pill may do nothing positive; it’s also possible that hauling millions of tons of fish from the ocean may have serious environmental consequences. In his newest book, The Omega Principle: Seafood and the Quest for a Long Life and a Healthier Planet, author and journalist Paul Greenberg describes an industry that sprung into existence based on a number of faulty assumptions about human health—and is now soul-searching within an ever-shrinking territory of scientific credibility. Left stranded with a half-swallowed carton of omega-3 capsules on my fridge, I found myself soul-searching too.

The rise of omega-3 supplements began when a team of Danish scientists, intrigued by reports of low rates of cardiac death among Inuit populations, embarked on an expedition to Greenland. They drew blood samples from local Inuit people and found far more omega-3s in their blood than in the blood of those in the Danish control group. The obvious hypothesis: Omega-3s are good for your heart.

It’s not just that the pill may do nothing positive; it’s also possible that hauling millions of tons of fish from the ocean may have serious environmental consequences.

This humble hypothesis should have been studied extensively before being elevated to the basis for an entire new health product, to assess if it was merely a correlation or if there really was some causative relationship. It was always possible that some other compound in the fish-heavy Inuit diet was responsible for their healthy hearts and that omega-3s had just came along for the ride. Or perhaps it wasn’t diet at all: Maybe the cold temperatures conferred the real cardiac benefits, in which case the high levels of omega-3s in Inuit blood would just be an unrelated coincidence. An even more serious oversight was brought to light in a 2014 Slate article by Elizabeth Preston. The Greenland Inuit may not have even had healthier hearts to begin with: Lower rates of cardiac disease might have just been an artifact of poor medical records. And yet, catapulted from this rickety foundation, omega-3 supplements are currently a $15 billion industry, still growing 7 percent annually.

Scientific research slowly caught up and started raining on the parade. The original claimed benefits for cardiac health were the first to fall. Large randomized controlled trials showed lackluster results. A 2012 meta-analysis came to a damning conclusion: “Overall, omega-3 … supplementation was not associated with a lower risk of all-cause mortality, cardiac death, sudden death, myocardial infarction, or stroke based on relative and absolute measures of association.”

There was also hope that omega-3 supplements would be beneficial for the human brain, based on the fact that the oil makes up 5–10 percent of the mass of the organ. But research on the effects of omega-3 supplementation on brain disease was similarly lackluster. For starters, studies reported that omega-3 supplements don’t help depression, don’t help young children at risk for psychotic disorders, and don’t improve the memories of the elderly. And what about cancer, the holy grail for pharmaceuticals? Nope. While it certainly seems there are many health benefits to eating fish, it’s becoming clearer and clearer that the benefit disappears somewhere during the transformation from fish to pill.

Despite the diminishing scientific support, omega-3 supplements weren’t legally required to change anything about the way they were marketed. Legislation pushed through in 1994, while the omega-3 industry was gaining a footing, ensured that these and all other supplements weren’t subject to oversight from the Food and Drug Administration. “Now supplement makers could put whatever they wanted in a capsule and sell it as a supplement,” writes Greenberg. “No science or evidence of any kind was necessary.” Most omega-3 products (like LiveWell Labs’ Ultimate Omega-3 Fish Oil) still maintain, with immense chutzpah, that omega-3s have “clinically proven” heart health benefits.

What to do with that half-empty carton? Swallowing them seems undesirable: months of foul, fishy burps for no obvious reason.

Another tactic the industry deployed to save face was to independently fund its own research. In 2017, the Global Organization for EPA and DHA Omega-3s, a trade association, published a press release of its own study that doubled down on the original claim that consuming omega-3s would lower the risk of coronary heart disease. That claim—contrary to findings of larger studies published both before and after—was a stretch. Despite the confident language of the press release, the study itself was actually much more muted: “Among randomized controlled trials, there was a nonstatistically significant reduction in coronary heart disease risk with EPA+DHA provision.” While industry funding doesn’t necessarily imply biased research, it is certainly murky territory. As Greenberg remarks, “once medical trials start to take their principle cues from industry (a phenomenon that has grown markedly in the last fifty years), research becomes marketing.”

The idea that omega-3 supplements would do something for human health isn’t unreasonable: The compound plays a role in basic human biochemistry and yet cannot be directly synthesized by the human body. One day, research may support real medical applications for omega-3s. And while home run clinical research supporting omega-3s is currently scant, so is anything suggesting that they are dangerous to the people who take them. If the omega-3 industry was just trying to squeeze a buck out of gullible health nuts with sugar pills, the scam might be unsavory but largely inconsequential. But these pills aren’t made from sugar. They are made from animals.

Omega oil isn’t a byproduct of fish that are already being processed for human consumption, like the happy salmon from my imagination. The oil filling my daily capsule was siphoned off from boiled-down schools of forage fish dragged out of the ocean for no other purpose. “It is hard, I know, to drum up sympathy for all those little, oily fish,” admitted Greenberg. But even if sympathy is a high bar, Greenberg certainly conveys the importance of these humble fish. Forage fish are the unsung heroes of the aquatic food web: Lying at a “critical juncture,” they are responsible for passing solar energy stored in photosynthetic plankton to all the predators. “Remove forage fish … and you get a much simpler, more primitive system,” says Greenberg.

Of course, the ocean is huge, and the tiny fish reproduce rapidly. But while the fisheries claim the practice is sustainable, Greenberg has his doubts. He thinks that the removal of these smaller fish could have ripple effects across the food chains. Altogether, Greenberg estimates that the human weight of the United States is removed from the ocean every year in the form of menhaden, anchovies, and krill—much of which is destined for omega-3 supplements. Even in the unlikely scenario that this has no impact on ocean ecosystems, the repercussions of this massive extraction may still reach us on land: After fish oil is squeezed into capsules, their carcasses are ground into fertilizer and animal feed, which is then deployed in our industrialized farming system. Ground fishmeal is sprinkled onto mineral-stripped soil to raise destructive commercial crops like corn. That corn then gets turned into high-fructose corn syrup to sweeten the soda of an increasingly diabetic world. Or it’s fed to beef cattle that accelerate global warming with their farts and whose meat ultimately kills us in a host of ways.

Barring future revelations of the medical marvels of omega-3s, I’ll probably never buy another carton of the fishy supplements again. I’m sufficiently convinced that the environmental costs far outweigh any marginal health benefits. But what to do with that half-empty carton? Swallowing them seems undesirable: months of foul, fishy burps for no obvious reason.

Maybe they’ll be most useful staying right there on top of my fridge, serving as a reminder that many of the seemingly small, mostly thoughtless choices I make can have far-reaching consequences.