Dementia: healthy eating and active lifestyle reduces risk

13 March 2015 - The Australian

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What actually works? A conga line of books on the subject makes the correlation between dementia and nutrition difficult to navigate.

Coconut oil is the latest wonder cure-all ­touted online, but Britain’s Alzheimer’s Society has no evidence that it works. More apple juice is another ­theory. Flossing your teeth also. (If you have periodontal disease before age 35 your odds of dementia years later are quadrupled.)

Healthy Eating to Reduce the Risk of Dementia is the latest book published on the subject.

Unusually, it is put together by an actual expert, Margaret Rayman, professor of nutritional medicine at the University of Surrey. Her specialism is iodine and selenium. Selenium is the stuff you get in brazil nuts and, she tells me, ­research holds that it may help brain cells from dying by pre­venting Alzheimer’s plaques and tangles from forming.

Selenium levels in the blood of people with mild Alzheimer’s disease is lower than in a brain-healthy person, but it’s not yet known whether the link is causative. Those with lower levels of selenium in their blood (according to a French study of 1166 ­people) were likelier to display levels of cognitive decline four years later. Other studies dispute this. The most recent ­science, says Rayman, is inconclusive but positive: a study of 100 people indicated that taking selenium supplements slowed the rate of decline.

There is a long-held mistaken assumption that cognitive decline is a natural part of ageing. It is true that if you reach your 90s your chances of developing dementia is one in three, but the rates in your 60s are far lower.

Researchers have found that even if you are older, you can have thousands of brain cells born daily. How do you stimulate this growth? Aerobic exercise, strenuous mental activity and avoiding obesity, chronic stress and sleep deprivation.

The most fascinating concrete fact in Rayman’s book is the still inexplicable — to scientists — difference between the benefits of fish and fish oil supplements on brain function. ­“Dementia rates in Japan,” Rayman points out, “are lower than in western Europe. Provided they still eat a ­traditionally fish-heavy Japanese diet, the Japanese have healthier brains in later life.”

Studies show that consumption of oily fish — high in omega-3 — at least twice a week benefits the brain. Rayman suggests eating mackerel, sardines (preferably in olive oil if they’re tinned), sprats, eel, salmon (preferably wild, not farmed), herring and trout. Those with the inherited ApoE-4 gene (50 per cent of people with Alzheimer’s have the gene) have a 40 per cent lower risk of dementia if their omega-3 intake is high. “Ideally, you’d eat fish four times a week,” counsels Rayman. If you hate fish, omega-3-enriched eggs are another (fairly rich) source.

There has been a lot of excitement about antioxidants but, again, the correlation between the low levels of antioxidants — vitamins A, C, E and beta carotene — in the blood of people with Alzheimer’s is not clear. Lower levels of vitamin B have been linked to damage in nerve cells and blood vessels, both of which are involved in the development of dementia.

B12 you can find in seafood and milk; B6 in poultry, wholegrains, potatoes and vegetables; folate in liver, yeast extract and more green vegetables, although in its synthetic form, folic acid, it is more easily absorbed.

If you’re worried about dementia, you have to do your ­research, question your assumptions and step back before you recalibrate your diet — take in other health considerations (such as lactose intolerance or high blood pressure).

Too much red wine is a bad idea — then again, so is too little — one to two small glasses a day is ideal. (If you don’t drink, eat a lot of grapes.) Coffee, tea and wine are rich in polyphenols — they’re naturally occurring and prevent against disease and UV damage. Drinking up to six cups of black or green tea, or three to four cups of coffee, could have benefits, studies have shown. If you love chocolate, keep on eating it. Caveat: as long as its cocoa content is over 70 per cent.

Carol Brayne, head of the Cambridge Institute of Public Health, is considered to be one of the world’s authorities on dementia. She has come to think of dementia as a lifelong process that — it has been proven — can even start in the womb because of nutritional factors: a mother who drinks or smokes or eats ­unhealthily or is not in mentally good health can give birth to a child who by the age of nine has a comparatively low IQ.