Fish oil pills are a popular dietary supplement, with people in the U.S. spending about $1.2 billion on them annually. This money is probably better spent elsewhere, according to a new study. A large clinical trial found that the key ingredient in fish oil pills – omega-3 fatty acids – didn’t slow mental decline in older people.
For the study, nearly 4,000 participants were followed over a five-year period. According to researchers, the study is the largest and longest of its kind. The findings, published in the Journal of the American Medical Association, didn’t support claims that omega-3 supplements can protect the brain from cognitive decline.
“Contrary to popular belief, we didn’t see any benefit of omega-3 supplements for stopping cognitive decline,” said Emily Chew, deputy clinical director at the National Eye Institute, part of the National Institutes of Health, in a statement.
She told the Washington Post that: “The supplements just don't cut it.” Adding that “If people are thinking [taking them] is going to help cognitive function, it's not going to do so among the older age group.”
Researchers randomly assigned participants into four groups: one was given a placebo, another was given omega-3, the other was given lutein and zeaxanthin – nutrients found in green leafy vegetables – and the final group with given omega-3, lutein and zeaxanthin. The participants' cognitive function was then investigated using a suite of tests, looking at things like immediate and delayed recall, attention and memory. The tests were given at the beginning of the study and then again two to four years later to see if there were any changes.
Researchers found that the cognitive function of each group decreased at a similar rate. In other words, omega-3 didn’t appear to have much of an impact. Researchers were, however, clear that the study focused on omega-3 in supplements and not foods high in omega-3 fatty acids, which could yield different results.
“We’ve seen data that eating foods with omega-3 may have a benefit for eye, brain, and heart health,” Chew said.
There are some limitations to the study, which researchers detail in the paper. In particular, researchers followed participants for five years, while the process of cognitive decline may occur over decades.
For now, it’s important to remember that a balanced diet is what really matters. Frank Hu, professor of nutrition and epidemiology at Harvard T.H. Chan School of Public Health, told TIME: “If you eat a healthy diet with high amounts of fruits, vegetables and marine fish, you probably don’t need to take fish oil supplements. The overall dietary pattern is more important than a single nutrient.”
