Total normal brain and hippocampus volumes were directly associated with levels of omega-3 fatty acids in a study of more than 1000 postmenopausal women.
The study, published online in Neurology on January 22, was conducted by a team led by James Pottala, PhD, University of South Dakota, Sioux Falls.
“These results are consistent with the idea that higher omega-3 levels may slow the loss of brain volume that occurs as we age,” senior author, William Harris, PhD, also from the University of South Dakota, told Medscape Medical News.
Women’s Health Initiative Memory Study
To examine the association between the amount of omega-3 fatty acids in the body and brain volume, Dr. Pottala, Dr. Harris, and colleagues used data from the Women’s Health Initiative Memory Study Magnetic Resonance Imaging (WHIMS-MRI) that evaluated the effects of hormone therapy in postmenopausal women in which blood samples had been frozen and brain MRI scans recorded.
“The blood samples were taken at the start of the study and the MRI scans were performed 8 years later. While this is not necessarily the perfect design, that’s what was available,” Dr. Harris noted.
They used the red blood cell omega-3 index as a measure of omega-3 status. This index is the percentage of omega-3 fatty acids — eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) — of the total fatty acids in red blood cell membranes.
Results showed that overall brain size was slightly but significantly smaller in the women in the lowest quartile of omega-3 index compared with those in the highest quartile. And specifically, the hippocampus, which is the area of the brain related to cognitive function, was also significantly smaller in the lowest vs the highest quartile of omega-3 index. This was after controlling for age, lipid levels, glucose, blood pressure, education, and hormone therapy.
The hippocampal volume difference between the highest and lowest quartiles of omega-3 levels was about 2.5%. For comparison, other studies have shown that patients with fairly severe Alzheimer’s disease have hippocampus volumes about 40% smaller than people without dementia, Dr. Harris said. “So it is a small effect but it is interesting that there was any detectable effect at all.”
The women in the lowest omega-3 quartile had an omega-3 index of 3.4% compared with 7% for those in the highest quartile. “For reference, Japanese people, who generally eat a lot of fish, have an omega-3 index of around 10%,” Dr. Harris noted. “It would be possible to move from an index of 3% to one of 7% by taking about 1000 mg of EPA + DHA every day or by eating a small portion of salmon or sardines every day. So it’s not difficult to do.”
In the paper the researchers write, “Changes in the omega-3 index that can be achieved through diet modification and/or supplementation are similar to those associated with 1 to 2 years of normal, age-related brain atrophy.”