A Lifetime Diet Emphasizing Vegetables & Fish Slows Cognitive Decline

Eat Your Vegetables and Fish for a Healthy Mind into Old Age

Evelyn Smith, M. S. in Library Science, University of North Texas (2012)

While the news this week focused on how moderate (once a week) fish consumption might possibly slow the onset of Alzheimer's among individuals possessing the APOE gene variant, and last year's headlines emphasized the importance of including dark green leafy vegetables like spinach and kale in a diet as a way to delay cognitive decline, one truth lies behind these studies: A life-long diet that stresses the intake of  dark-green vegetables and fish while limiting the consumption of red meat, poultry, refined sugar, and processed foods can delay and perhaps even prevent cognitive decline. In other words, now more than ever, to use a cliche, "You are what you eat!"

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Weekly Fish Consumption May Delay Alzheimer's Disease for 30% of the Population with the APOE Gene

Clare, Martha Clare, Brockman, John, and Schneider, Julie A., et al. (2016, February 2). Association of seafood consumption, brain mercury level, and APOE ε4 status with brain neuropathy in older adults. JAMA, 315(5), pp. 489-497. doi:10.1001/jama.2015.19451. [Open Access]. Retrieved from http://jama.jamanetwork.com/article.aspx?articleid=2484683#References

Moderate seafood consumption correlates with a lower risk for Alzheimer's. Researchers arrived at this conclusion after an analysis of deceased participants in the Memory and Aging Project neuro-pathological cohort study that took place between 2004 and 2014. After performing autopsies on 286 brains of 554 deceased, predominantly women residents of Chicago, whose mean age at death was 89.9 years, and comparing their answers on a food frequency questionnaire filled out on average 4.5 years earlier, researchers discovered that those participants who ate seafood at least once per week were much less likely to develop Alzheimer's disease. The more seafood the participants consumed, the much less likely they were to develop Alzheimer's. Although the autopsies showed that higher levels of fish consumption correlated with higher levels of mercury in the brain, they didn't correlated with  the type of brain damage associated with Alzheimer's disease. Moreover, taking fish oil instead of actually eating the fish didn't confer the same benefits as actually eating the fish did (Clare, 2016, February 2, Abstract, p. 489).

See also:

Chew, Emily Y., Clemons, Traci E., Agrón, Elvira, et al. (2015, August 25). Effect of Omega-3 fatty acids, lutein/zeaxanthin, or other nutrient supplementation of cognitive function. JAMA, 314 (8), 791-801). doi: 10.1001/jama.2015.9677. [Full text]. Retrieved from http://jama.jamanetwork.com/article.aspx?articleid=2429713

In a double-masked, randomized trial, retina specialists in 82 United States academic and community medical centers over a five-year period not only observd 4,000 older patients at risk for macular degeneration, but they also administered cognitive tests via the telephone whereupon they discovered that oral Omega-3 fatty acid supplements had no effect on cognitive function (Chew, 2015, August 25, Abstract, p. 791). 

In other words,  eating fish regularly may delay or prevent cognitive decline, but taking fish oil supplements doesn't do so.

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Kroger, Edeltraut, and Laforce, Robert. (2016, February 2). Fish consumption, brain mercury, and neuropathology in patients with Alzheimer disease and dementia. JAMA, 315(5), pp. 465-466. doi:10.1001/JAA.2016.0005. [Editorial extract only]. Retrieved from http://jama.jamanetwork.com/article.aspx?articleid=2484661

Alzheimer's is fast becoming an increasing concern as an aging population worldwide is living longer, which means there is a need for proactive preventive strategies to combat Alzheimer's; for example, adhering to a Mediterranean-style [or MIND or DASH] diet with regular fish intake and limiting red meat intake can benefit older adults seeking to maintain brain health.  Research studies have consistently associated a regular intake of n-3 fatty acid fish with a slowing of cognitive decline and a decreased risk for Alzheimer's (Kroger, 2016, February 2, Extract, p.489).

Go Fish: Popular Takes On the Importance of the MAP Study:

Gregory, Andrew. (2016, February 2). Seafood really is brain food say scientists who food it could reduce Alzheimer's risk . Mirror. Retrieved from http://www.mirror.co.uk/news/technology-science/science/seafood-really-brainfood-say-scientists-7295129

Although researchers are careful not to extend their findings on the benefits of regularly consuming seafood to a general population, a study published February 2, 2016, in the Journal for the American Medical Association reveals that for older adults with the APOE gene, eating at least one serving of seafood weekly greatly reduced their risk for developing Alzheimer's (Gregory, 2016, February 2, para. 1-6). However, investigators also stressed that the consumption of omega-3 fatty acid fish should be part of a balanced diet and that taking fish-oil supplements alone (rather than eating fish) does not confer the same brain-healthy benefits (Gregory, 2016, February 2, para. 7 & 9). They also admitted that the brains of those individuals who ate the most fish had the higher levels of mercury; but at the same time, they stressed that this didn't correlate with the changes that Alzheimer's makes in the brain (Gregory, 2016, February 2, para. 10). While a mix of factors, including age, lifestyle, and genetic risk, seems to determine Alzheimer's risk, evidence suggests that maintaining cardiovascular health by adhering to a balanced diet and regular exercise is also good for the brain (Gregory, 2016 February 2, para. 11-12).

Park, Alice. (2016 February 2). Fish, mercury and Alzheimer's risk. Time. Retrieved from http://time.com/4201808/fish-mercury-and-alzheimers-risk/

While regular consumption of seafood protects the heart and brain, an analysis of the autopsies on the brains of the participants in a Rush University study also shows that eating fish at least once weekly accumulates mercury in the brain. However, for the 30 percent of the population who have at least one copy of the APOE gene variant, eating seafood regularly just might outweigh the risk of brain toxicity since doing so lowers the amount of Alzheimer's-related proteins in the brain (Park, 2016, February 2, para. 1-5). Moreover, even individuals without this gene might also benefit from eating seafood regularly (Park, 2016, February 2, para. 6). Thus, the study eases fears that mercury in seafood causes dementia (Park, 2016, February 2, para. 8).

Pollario, Karen. (2016, February 2). Seafood may help those at risk of Alzheimer's: Study also finds mercury in fish isn't linked to dementia symptoms. WebMD. Retrieved from http://www.webmd.com/alzheimers/news/20160202/seafood-might-protect-brain-in-people-at-genetic-risk-for-alzheimers

Data released from the Memory and Aging Project published in the JAMA February 2, 2016, issue posits that mercury in fish does not lead to cognitive decline while a healthy diet featuring regular seafood consumption might stave off Alzheimer's disease in adults who have the APOE gene (Pollario, 2016, February 2, para. 1, 11, & 14).

Even though the autopsied brains of older study participants who regularly consumed more seafood had greater levels of mercury in their brains, researchers did not find a link between these higher levels of that heavy metal and the brain damage that is typical in Alzheimer's patients (Pollario, 2016, February 2, para. 2). Thus, older adults with the APOE gene who regularly eat fish while also adhering to a healthy diet do not need to be overly concerned about mercury contamination while they are reaping the protective effects of a diet with moderate levels of seafood.   For these individuals, regularly eating fish correlates with a decreased risk for Alzheimer's and a slower rate of Alzheimer's disease progression (Pollario, 2016, February 2, para. 5-6 & 9).

In the case of the MAP participants, the questionnaire they filled out to measure seafood consumption provided them with four choices: 1) Tuna sandwich, 2) fish sticks, cake, or sandwich, 3) fish served as a main dish, 4) or shrimp, lobster, or crab. Researchers also not only analyzed tissue samples from their autopsied brains for metal concentrations, but  they also looked for evidence of strokes and micro-strokes, and the plaque and tangles associated with Alzheimer's as well as the Lewy bodies found in the brains of individuals diagnosed with Parkinson's (Pollario, 2016, February 2, para. 12-13).

By comparing the regular diets of older adults with their subsequent brain autopsies, researchers determined that eating one or more servings of seafood a week meant that older adults with the APOE gene were less likely to develop Alzheimer's. They didn't associate the same protective link that lowers the odds of developing Alzheimer's for individuals without the APOE alle. However, they did find that those brains with higher levels of the fatty-acids found in plants had fewer strokes (Pollario, 2016, February 2, para. 15-16). Thus, since few middle-aged and older adults have been tested for the APOE gene, adopting a diet that features fresh vegetables and fruit as well as one or two serving of fish weekly is a prudent step to take if one wants to prevent or delay dementia.

Eating Fish Is Only Part of Adhering to a Mostly Vegetarian MIND or Mediterranean-style Diet

Feart, C. Samieri, C., and Alles, B., et al. (2013, February). Potential benefits of adherence to the Mediterranean diet on cognitive health. The Proceedings of the Nutrition Society, 72 (1), pp. 140-52. [Abstract Only]. doi: 10.1017/S0029665112002959. Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/23228285

A Mediterranean diet characterized primarily by the consumption of plant foods, olive oil, and a low to moderate intake of fish, and low-levels of consumption for both meat and poultry as well as a low to moderate consumption of wine during meals correlates with a decline in the risk for dementia (Feart, 2013, February, Abstract, p. 140).

The MIND Diet recommends, '"Eat this, not that!"

Hosking, D. E. Nettlebeck, T., and Wilson, C., et al. (2014, July 28). Retrospective lifetime dietary patterns predict cognitive performance in community-dwelling older Australians.  British Journal of Nutrition, pp. 112(2), 228-37. doi: 10.1017/0007114514000646.  [Abstract only].  Retrieved from http://www.ncbi.nlm.nih.gov/pubmed/24709049

In a cognitively-healthy sample of 352 Australians aged 65 and older, after controlling for such factors as current diet, age, gender, years of education, smoking, income level, physical activity, and the inheritance of the APOE gene, the survey documented that those Australians who spent a life time taking their coffee with sugar and eating a high-fat diet exhibited slower reaction times, poorer working and short-term memories, retrieval fluency, and reasoning skills than those who ate more vegetables and non-processed foods. These dietary choices had a positive effect on their perceptual speed and retrieval frequency (Hosking, 2014, July 28, Abstract, p. 228).

Morris, M. C., Tangney, C. C., and Wang, Y., et al. (2015, September). Alzheimer's & Dementia: The Journal of the Alzheimer's Association, 11 (9), pp. 1015-22.  doi: 10.1016/j.jalz.2015.04.011. [Abstract only]. Retrieved from 
http://www.ncbi.nlm.nih.gov/pubmed/26086182

The older adults participating in the Memory and Aging Project study who followed the MIND diet—a combination of the Mediterranean Diet and DASH, a dietary plan used to control hypertension, on average slowed their cognitive decline by 4.7 years (Morris, 2015, September, Abstract, p. 1015).

Unfortunately, this measured approach to diet as a means to slow cognitive decline turned into hyperbole in the following news article. Even so, Hyslop's claims underline the idea that a diet that consists primarily of plant-based foods does slow cognitive decline:  

Hyslop, Leah. (2015, March 31).  Eating spinach every day could*make your brain 11 years younger.  Telegraph.  Retrieved from 

http://www.telegraph.co.uk/foodanddrink/foodanddrinknews/11505924/Eating-spinach-every-day-could-make-your-brain-11-years-younger.html

When researchers at Chicago's Rush University evaluated the diet and health of 950 older adults every day for from two to ten years, they found that eating spinach and or kale once or twice a day experiences “significantly less” cognitive decline even when researchers made allowances for their educational levels, frequency of exercise, and family history of dementia. On average, a diet that emphasized eating dark green leafy vegetables delayed mental decline by 11 years (Hyslop, 2015, March 31, para. 2-5). Lead researcher, Martha Clara Morris, attributed this benefit to the high levels of vitamin K, lutein, folate and beta carotene found in dark green leafy vegetables (Hyslop, 2015, March 31, para. 7).

*Emphasis added.