Fish oil supplements may shield against Alzheimer's, study finds

Consuming fish oil may have a protective effect on the brain’s cells – potentially shielding people from Alzheimer’s disease.

New research from the University of South Dakota has revealed that individuals with higher blood levels of omega-3 fatty acids – found in fish and fish oil – may have larger brain volumes in old age.  This could have significant implications for the elderly population, since a shrinking brain volume is often associated with dementia and Alzheimer’s.

Omega-3s consist of three types of fats – ALA, found in plant oils, and EPA and DHA, found in marine oils.  According to the study’s author, health experts have long suspected omega-3s may slow brain cell death, as the human brain is rich in DHA and other omega-3 fatty acids.

“It’s there for one reason or another,” lead author Dr. Bill Harris, professor of medicine at Sanford School of Medicine at the University of South Dakota, told “And then other studies have led people to think that…fish is brain food.  People have seen that populations that eat more fish have less dementia …so it seemed like a natural thing to look at.”

To better study the association between omega-3s and brain volume, Harris and fellow researcher James Pottala, of the University of South Dakota, analyzed red blood cell samples taken from 1,111 post-menopausal women as part of the Women’s Health Initiative Memory Study.  Eight years after the blood samples were taken, the women – who were then an average of 78 years old –  underwent MRI scans in order to measure their brain volumes.

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The researchers specifically measured the levels of omega-3 fatty acids EPA+DHA in the red blood cell samples, which had been frozen and preserved for many years.

“The red blood cell is a good representative of the other tissues in the body,” Harris noted. “Its levels of omega-3s are more reflective of the whole body.”

Harris and Pottala found that the women with higher levels of omega-3s had larger total brain volumes eight years later.  Furthermore, the MRIs also indicated that higher levels of omega-3s were associated with increased volume in a specific brain region – the hippocampus.

“The hippocampus is known to be related to the progression of dementia,” Harris said. “As it shrinks, dementia becomes more of a problem.  So we did find that people with higher omega-3s had higher volumes in the hippocampus – located right in the middle of the head, right at the top of the brain stem.”

While health experts still don’t fully understand how omega-3s interact inside the body, Harris said it’s possible that EPA and DHA act as anti-inflammatory agents.

“A lot is known and a lot remains to be known,” Harris said. “We think probably what they do is they help [with] generalized reduction in inflammation. That has benefits all over the body – with the brain, blood vessels, joints, everywhere…They also may change cell membrane structure and kind of give them a tune up.”

Harris said that people can eat more fish or take fish oil supplements in order to reap the potential health benefits of omega-3s.  But he added that the best benefits will come only from EPA and DHA – not ALA, which is found in flaxseeds, black walnuts and canola oil.

“[With ALA], in order for it to become effective, it has to be converted in the body after you eat it to these fish oil omega-3s,” Harris said. “That conversion process is very inefficient in most people, so you don’t really raise your omega-3 index by eating plant-based omega-3s.”

While Harris and other health experts are fairly certain omega-3s hold brain-preserving benefits, he noted that his study only shows an association between the fatty acids and larger brain volume – not a causal relationship. Despite a highly controversial study linking omega-3s to increased prostate cancer risk, the fatty acids have mostly been shown to produce no adverse health effects -- which is why Harris gives them a strong recommendation.

“They’re completely safe to eat; they’re in fish and supplements,” Harris said.  “So even having a possibility of being a benefit for slowing the rate of dementia gives them a good edge.”

The research was published in the online issue of Neurology, the medical journal of the American Academy of Neurology.