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To keep your brain healthy as you age, consider eating more salad dressing, nuts, fish, chicken and leafy greens - and laying off high-fat animal foods.

According to a new study, published this week in the online edition of Archives of Neurology, it's a dietary pattern associated with a significantly lower risk of developing Alzheimer's disease.

It's estimated that half a million Canadians have Alzheimer's, a progressive and degenerative brain disease that causes thinking and memory to become seriously impaired.

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While research on diet and risk of Alzheimer's is rapidly growing, studies that have investigated individual foods and nutrients have turned up mixed results. This is partly due to the fact that we eat meals that combine many foods and nutrients which likely work in tandem to offer protection.

In the study, researchers from Columbia University Medical Center in New York followed 2,148 adults without dementia, aged 65 and older, and determined their adherence to dietary patterns thought to be related to Alzheimer's risk.

The researchers identified several dietary patterns, or food combinations, that varied in amounts of seven nutrients previously shown to be associated with either lowering or raising the risk of Alzheimer's disease: saturated fat, monounsaturated fat, omega-3 fats, omega-6 fats, vitamin E, vitamin B12 and folate.

Study participants provided information about their typical diets and were assessed for the development of dementia every 1.5 years. Dementia, the most common cause being Alzheimer's disease, describes progressive symptoms such as memory loss, mood changes and a decline in the ability to talk, read and write caused by damage or changes to the brain.

After four years, 253 individuals were diagnosed with Alzheimer's disease. One dietary pattern was shown to offer significant protection against developing it.

Individuals who had higher intakes of salad dressing, nuts, fish, chicken, tomatoes, fruit, cruciferous vegetables, leafy greens and lower intakes of high-fat dairy, red meat, organ meats and butter were 38-per-cent less likely to develop Alzheimer's, compared to those who adhered the least to this dietary pattern.

There are a number of ways this combination of foods may reduce Alzheimer's risk. Vitamin E, found in vegetable oils, almonds, peanuts, soybeans, wheat germ, avocado and green leafy vegetables, is a powerful antioxidant that helps shield brain cells from free radical damage.

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Free radical damage, also called oxidative damage, is believed to contribute to the progressive decline in brain function seen in Alzheimer's. Free radicals are routinely produced within cells as a by-product of oxygen metabolism, but they can also be created from cigarette smoke and air pollution. The brain is especially vulnerable to free radical damage because of its high demand for oxygen, its abundance of easily oxidized cell membranes, and its weak antioxidant defences.

Foods plentiful in folate, such as green vegetables, citrus fruit and nuts help keep blood levels of an amino acid, called homocysteine, in check. Having a high homocysteine level is thought to damage artery walls and increase the risk of Alzheimer's and other forms of dementia.

Healthy fats found in oily fish, salad dressing and nuts may protect from dementia by reducing inflammation, blood clot formation, and hardening of the arteries in the brain. These fats may also prevent the build-up of a protein called beta amyloid, which can interfere with communication between brain cells.

A diet low in high-fat dairy products, butter, red meat and organ meats is lower in saturated fat, the type of fat that raises LDL (bad) cholesterol and, in turn, can damage arteries. Previous research has, in fact, linked a higher intake of saturated (animal) fat with a two- to threefold greater risk of Alzheimer's disease.

In my opinion, these findings highlight two salient points. For starters, they refute the notion that popping a vitamin E supplement - or simply cutting saturated fat - will protect you from Alzheimer's disease.

Rather, it's the big picture that counts. Eating a variety of healthy, nutrient-rich foods and, at the same time, minimizing your intake of foods that may harm the brain is what seems to matter most when it comes to reducing the risk of Alzheimer's disease. In other words, the whole - or combined effect - is greater than the sum of its separate effects.

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A large study published last year also linked a pattern of eating to protection from Alzheimer's disease. In the study, people who adhered most closely to a Mediterranean-style diet - rich in fruit, vegetables, nuts, beans and olive oil - had up to a 40-per-cent reduced Alzheimer's risk.

Secondly, these findings add to a growing body of evidence that suggests what you eat to protect yourself from heart disease are the same foods that can keep your brain healthy. A healthy diet can prevent Type 2 diabetes, high cholesterol and hypertension, risk factors that damage blood vessels that have also been linked to a greater risk of Alzheimer's disease.

Based on these new findings, the following foods, when eaten together as part of a low-saturated fat diet, may lower the odds of developing Alzheimer's disease:

Salad dressing - monounsaturated fats include olive, canola, peanut, avocado and almond oils. Sunflower, safflower, soybean, corn, grapeseed, hemp, flaxseed, and walnut oils are rich in omega-6 fats.

Nuts - almonds, Brazil nuts, cashews, hazelnuts, peanuts, pecans, pistachios, walnuts.

Oily fish - anchovies, herring, mackerel, salmon, sardines, trout.

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Cruciferous vegetables - broccoli, bok choy, Brussels sprouts, cabbage, cauliflower, turnip.

Dark green leafy vegetables - arugula, beet greens, collard greens, dandelion, kale, rapini, spinach, Swiss chard.

Tomatoes - fresh tomatoes, tomato juice, stewed tomatoes, tomato sauce; choose reduced sodium when possible.

Fruit - apples, berries, citrus fruit, grapes, kiwi fruit, melon, pears.

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is lesliebeck.com.

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