Novel study links fishy diets to preservation of gray matter in areas shrunken by the Alzheimer's/dementia process
by Craig Weatherby
“Beware the shrinking brain!”
That may sound like a line from a bad horror movie, but brain shrinkage is a very real part of the aging process.
Fortunately, the results of an unprecedented study suggest that fatty fish may help people maintain healthy, “full-figured” brains.
Losses of brain volume reveal that brain cells themselves are shrinking … a proven sign of current or impending dementia.
Novel study helps explain why fish seems to reduce dementia risk
People who eat fish weekly may be reducing their risk of developing Alzheimer's disease or milder forms of memory loss.
At least, that's the implication of a novel study that compared people's fish intake with their MRI brain scans and tested mental performance (RSNA 2011).
Encouragingly, the study's results linked eating baked or broiled fish weekly to maintenance of gray matter in key, dementia-related brain areas over a 10-year period.
In contrast, eating fried fish was not linked to protection of gray matter or cognitive capacities. To learn more, see our sidebar, “Fried fish flunks the test”.
This is the first study to detect a link between fish consumption and the health of brain areas shrunken by the Alzheimer's disease process.
As lead author Cyrus Raji, M.D., Ph.D., put it, “… people who consumed baked or broiled fish at least one time per week had better preservation of gray matter volume in brain areas at risk for Alzheimer's disease.” (UPMC 2011)
Fishy diets may delay dementia and protect thinking, memory
Dr. Raji's team estimated that their bigger brains make it five times less likely that the fish lovers in the study would develop Alzheimer's or mild cognitive impairment (MCI) over the next five years.
Fried fish flunks the test:
Blame the omega-6s in frying oil
In contrast to the benefits of baked or broiled fish, no brain-volume benefits were seen in the men and women who reported eating mostly fried fish.
This finding fits with epidemiological evidence linking fried fish to higher stroke and dementia risks. (See “Fish Cut Female Heart Failure; Fried Fish Raised Risk” and other articles in the “Omega-3 / Omega-6 Balance” section of our news archive.
The varying effects of fish cooked different ways comes down to the high loads of omega-6 fatty acids found in the oily breading on most fried fish.
Omega-6s predominate in the most commonly used frying oils: soy, corn, cottonseed, safflower, and sunflower.
Healthier, lower-omega-6 home-kitchen oils include olive, macadamia nut, canola, and “hi-oleic” sunflower.
But eating fish breaded and fried in any vegetable oil should be a limited treat.
Why? Because frying leaches and damages some of the fishes' omega-3s, while the oils' omega-6s can be damaged by high frying temperatures.
MCI is a mild, early form of dementia, in which memory loss is much less than in full-blown senile dementia or Alzheimer's. “Consuming baked or broiled fish promotes stronger neurons in the brain's gray matter by making them larger and healthier,” noted Dr. Raji (UPMC 2011)
As he said, “This simple lifestyle choice increases the brain's resistance to Alzheimer's disease and lowers risk for the disorder.” (UPMC 2011)
The UPMC-led team also tested the volunteers' cognitive and memory capacities, and those who ate baked or broiled fish weekly scored better versus those who ate fish infrequently.
As Dr. Raji explained, “Working memory is destroyed by Alzheimer's disease. We found higher levels of working memory in people who ate baked or broiled fish on a weekly basis, even when accounting for other factors, such as education, age, gender and physical activity.” (UPMC 2011)
First-ever MRI study detected desirable brain differences in fish lovers
The authors selected 260 cognitively normal people, whose fish consumption was determined by administering the National Cancer Institute's Food Frequency Questionnaire.
Out of all the participants, 163 ate fish on a weekly basis, and the majority of those enjoyed fish one to four times a week. Every volunteer underwent two MRI scans of their brain, 10 years apart.
The researchers then compared the brain scans to the volunteers' reported fish intake – including their favored cooking methods.
They looked for significant links between diet and brain volume in key areas, adjusting the results to account for the differences in brain health status associated with variations in age, gender, education, race, obesity, and physical activity … as well as the presence of the apolipoprotein E4 (ApoE4) gene, which raises the risk of Alzheimer's.
Specifically, eating baked or broiled fish weekly was linked to having greater gray matter volume in the areas of the brain typically shrunken as part of the Alzheimer's disease process: namely, the hippocampus, precuneus, posterior cingulate, and orbital frontal cortex.
Funding for the study was provided by the National Institute on Aging.
University of Pittsburgh School of Medicine (UPMC). Eating Fish Reduces Risk of Alzheimer's Disease, Pitt Study Finds. Nov. 30, 2011. Accessed at http://www.upmc.com/MediaRelations/NewsReleases/2011/Pages/Eating-Fish-Reduces-Risk-Alzheimers.aspx
Radiological Society of North America annual meeting (RSNA 2011).
Raji C et al. Regular Fish Consumption Is Associated with Larger Gray Matter Volumes and Reduced Risk for Cognitive Decline in the Cardiovascular Health Study Neuroradiology (Cognition II); Friday, December 02 2011 Accessed at http://rsna2011.rsna.org/search/event_display.cfm?em_id=11008757 Radiological Society of North America (RSNA).
Eating Fish Reduces Risk of Alzheimer's Disease. December 1, 2011. Accessed at http://www.rsna.org/Media/rsna/RSNA11_newsrelease_target.cfm?id=571