You’ve probably heard at some point that it’s a good idea to try to get a decent amount of omega-3 fatty acids in your diet. Omega-3s are essential fats, meaning your body needs to get them from food, and they’re found in things like fish, walnuts, and leafy vegetables. They’re also thought to help prevent heart disease and stroke, as well as depression.
With that in mind, one man decided to eat fish every day for a year to see what kind of impact it would have on his body. Paul Greenberg captured the experience in a new Frontline documentary called The Fish on My Plate. Greenberg met with a doctor before and after his year of fish eating to track his progress. “I’ve got slightly elevated blood pressure. I’ve got cholesterol issues. I have depression issues. I have sleep issues, and I don’t like it,” he says in the documentary. “So I started to listen to the soft purr of the omega-3 industry: This is everything they’re supposed to fix.”
So, he embarked on his experiment. But, at the end, his doctor says it really didn’t change anything. Greenberg revealed that his cholesterol ratio was the same and his triglyceride level—the amount of a fat in the blood—was the same. However, his blood pressure went up a little, and he had elevated mercury levels which a biologist told Greenberg was “slowing your thinking and hurting your memory.” (All fish contain at least traces of mercury, which is why the FDA recommends people only eat 2 to 3 servings a week. The United States Department of Agriculture (USDA) recommends that people eat fish twice a week.) The debate is still on as to whether omega-3s are the wonder nutrients people say they are.
First, here’s an omega-3 fatty acids refresher:
Omega-3 fatty acids are a group of polyunsaturated fats. The Nutrition Source from the Harvard T.H. Chan School of Public Health breaks them down: Eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) mainly come from fish, while Alpha-linolenic acid (ALA) is found in vegetable oils and nuts, flax seeds, leafy vegetables, and some animal fat.
Omega-3s provide the starting point for making hormones that regulate blood clotting, contraction and relaxation of artery walls, and inflammation, and also bind to receptors in cells that regulate genetic function. Omega-3 fats have been shown to help prevent heart disease and stroke, may help control lupus, eczema, and rheumatoid arthritis, and may play protective roles in cancer and other conditions, according to The Nutrition Source.
However, while the USDA recommends that people eat fish twice a week, it doesn’t recommend that people try to get a certain level of omega-3 fatty acids in their daily diet. It also prohibits companies from boasting on their food labels that certain products are “high in,” “rich in,” or an “excellent source of” DHA or EPA.
Many people try to get omega-3s through fish oil supplements. However, the American Heart Association announced in March that they “may be reasonable” for people who have had a heart attack or heart failure, but “there is a lack of evidence that omega-3 fish oil supplements prevent cardiovascular diseases in the general population.”
Experts aren’t surprised that Greenberg didn’t see a big health change with his experiment.
Kathleen Fairfield, M.D., Dr.P.H., a physician-scientist at Maine Medical Center with a background in nutritional epidemiology, tells SELF that she’s not surprised that the health metrics Greenberg measured didn’t change. “Many of the benefits of eating fish that is high in omega-3s are not expected to be apparent in cholesterol or blood pressure measurements,” she says. “We think that reducing the risk of sudden death from abnormal heart rhythms in people with known heart disease (recent heart attack, for example) is one of the major benefits.” Fairfield says she would have thought that Greenberg’s triglycerides would be lower, but his levels depend on his genetics and what else he was eating.
Deena Adimoolam, M.D., an endocrinologist specializing in diabetes and metabolism at Mount Sinai Medical Center, tells SELF she’s also not shocked by the findings. “There have already been large research studies performed over the years to evaluate the health benefits of omega-3-fatty acids which have provided non-conclusive results,” she says. This research data looked at many people who were followed for years in some cases and were carefully designed to study whether omega-3-fatty acids lead to a specific health change. “I trust this data, more than I trust the story of one individual who is studied over one year, though the end results were similar,” she says.
Ruth Kava, Ph.D., senior nutrition fellow at the American Council on Science and Health, tells SELF that it also matters what Greenberg was eating beforehand. If he already ate fish once or twice a week before his experiment, it’s unlikely he would see a change in his overall health, she says. While she says that eating fish every day for a year isn’t necessarily a bad thing, she also points out that omega-3s aren’t an end-all be-all when it comes to good health—and neither is any other one food or nutrient. “People tend to think of things as this is or isn’t a superfood, but I don’t think that we have any superfoods, really,” she says.
The research on the benefits of omega-3s is inconclusive, but eating fatty fish can still be beneficial.
Fairfield says the belief that omega-3s are wonder-fats started with the observation that there was less heart disease in populations who ate a lot of fatty fish. Then, observational studies (i.e. studies in which researchers draw conclusions from looking at a population, but not changing anything) that asked people to report how much fish they ate also showed that people who ate more fatty fish had less heart disease. However, that research shows correlation, not causation—meaning, scientists can’t prove that eating fish causes a decrease in heart disease, there is simply an association. “It’s difficult to conduct a randomized controlled trial of fish consumption and measure results over many years in people with different genetic makeups, which is what we really would need to do to understand how eating fish benefits certain types of people over time,” Fairfield says.
That doesn’t mean omega-3s won’t do anything for you. Adimoolam notes that research has found that those who have established coronary artery disease may have a reduced risk of death due to heart disease or sudden cardiac death by having 250 milligrams a day of EPA and DHA. DHA supplementation during pregnancy is also important for fetal brain health and maturation, she says.
As for claims that omega-3 fatty acids can help reduce depression, Adimoolam says there are no good longitudinal studies to back this up. “The studies that are out there are quite small and not long,” she says. While there are more studies to suggest that omega-3-fatty acids can help decrease a person’s risk of dementia, she says that data is not conclusive. “The larger randomized trials did not show that omega-3 supplementation improved cognitive performance,” she says.
Fairfield says “it’s possible” that regularly having omega-3s reduces the risk of developing heart disease and other vascular disease, although it hasn’t really been proven yet. And, she points out, there’s a potential indirect effect: “If it keeps people from eating red meat, then that is even better.” (Studies have linked red meat consumption to colorectal cancer, digestive tract inflammation, and an increased risk of stroke.)
For the average person, Kava recommends trying to eat fatty fish like salmon, trout, and mackerel once or twice a week. If fish isn’t your thing, she says putting ground flax seed on your cereal in the morning can also give you a boost. She also recommends taking a pass on fish oil supplements unless your doctor specifically recommends them: “I’d rather see people get their nutrition from food.”
This article originally appeared on self.com