If you are popping fish oil supplements in the hope that the omega-3s found within will help protect your brain from cognitive decline, you may want to recap that bottle. A new study — the longest and largest of its kind — has found that omega-3 supplements do not improve brain health and memory in older people.

The study, which was published in the Journal of the American Medical Association, evaluated the cognitive health of 4,000 participants over a five-year period. The participants, who were an average age of 72 years old, were divided into three groups and given either a placebo pill, omega-3 supplements or a supplement containing lutein and zeaxanthin — nutrients found in green leafy vegetables.

Omega-3s have long been associated with better eye health, lower risk of cardiovascular disease, and reduced incidences of dementia. But according to the study, after five years, omega-3 supplements had "no statistically significant effect on cognitive function."

Participants in the study were evaluated for cognitive decline at the beginning of the study and again after two years and four years. Researchers found that the rate of cognitive decline dropped at a similar rate for all three groups, indicating that no combination of supplements helped to protect brain health.

So omega-3 supplements won't help protect your brain. But researchers were quick to point out that the study's results could be very different if the participants consumed foods high in omega-3s, such as fish, dairy products, peanut butter and some fruits and veggies, rather than omega-3 supplements.

In other words, skip the supplements and serve up some salmon. It may or may not protect your brain from cognitive decline. But it will certainly taste better.