Among the myriad changes that accompany aging, shrinking brain volume can be a worrying one. A normal part of growing older, it can also be a sign of Alzheimer's disease. But the good news is that a recent study suggests people with higher levels of omega-3 fatty acids have larger brain volumes in old age.

The research, published in Neurology, the medical journal of the American Academy of Neurology, suggests that the larger brain volumes associated with higher omega-3 levels are the equivalent to preserving up to 2 years of brain health.

James V. Pottala, PhD, from the University of South Dakota, and colleagues first assessed red blood cell (RBC) levels of omega-3 eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in 1,111 postmenopausal women from the Women's Health Initiative Memory Study.

Additionally, the team measured brain volumes via MRI scans.

After 8 years, the team followed-up with further brain scans on the women - who then had an average age of 78.

The researchers found that the women who had higher levels of omega-3s also had larger total brain volumes.

In detail, women with levels of fatty acids that were twice as high - at 7.5%, compared with 3.4% - had a brain volume that was 0.7% larger.

Additionally, women with higher omega-3 levels had a 2.7% larger volume in the hippocampus, an area of the brain that begins to atrophy in Alzheimer's patients before symptoms even appear.

Higher omega-3 levels 'can be achieved through diet'

Omega-3 fatty acids are fats found in plant and marine life oils. Some sources include oily fish, such as anchovies, salmon and mackerel, as well as flax, walnuts, basil, eggs and spinach.

James Pottala explains how individuals can increase levels of omega-3s:

"These higher levels of fatty acids can be achieved through diet and the use of supplements, and the results suggest that the effect on brain volume is the equivalent of delaying the normal loss of brain cells that comes with aging by 1 to 2 years."

A study published in December 2013 suggested that omega-3 supplements are able to cross the blood-brain barrier in Alzheimer's patients, affecting markers of inflammation for the disease.

The study showed that participants had higher levels of both DHA and EPA in their cerebrospinal fluid and blood after taking an omega-3 supplement every day for 6 months.

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Increasing omega-3 levels in the body, through supplements or diet, may delay normal loss of brain cells associated with aging by up to 2 years, the researchers say.

However, other studies have refuted the health claims surrounding omega-3s.

One study from 2013 showed that participants who took omega-3s did not perform better on memory tests, compared with those who had low levels of the fatty acids in their blood, suggesting omega-3 does not fight cognitive decline.

Still, the authors of this latest study show convincing evidence to the contrary, writing that their study "adds to the growing literature suggesting that higher omega-3 FA tissue levels, which can be achieved by dietary changes, may hold promise for delaying cognitive aging and/or dementia."

They add that future studies "should examine whether maintaining higher RBC EPA and DHA levels slows the rate of hippocampal or overall brain atrophy."