Foods rich in vitamin E lower risk of dementia
Posted by medconsumers on June 27, 2010
A high intake of foods rich in vitamin E may lower the chance of dementia; high blood levels of vitamin D are associated with a lower risk of Parkinson’s disease and cognitive decline. These are the new, preliminary findings from three studies published recently in Archives of Neurology and Archives of Internal Medicine.
The first study, which concentrated on blood levels of vitamin D, included 638 Italians over the age of 65 living in Tuscany. Their cognitive function was assessed at the start of the project and twice thereafter over the next six years. Here’s the bottom line: Those whose blood tests showed a severe deficiency of vitamin D were the most likely to show declines in thinking, learning, and memory.This is the first study to look at the association between dementia and vitamin D, which has long been known to be important to bone health. (Earlier research showed the lower the blood levels of vitamin D, the higher the incidence of a wide range of disorders including cancer, vascular disease, infectious conditions, autoimmune diseases, osteoporosis, type 2 diabetes and obesity. click here)
The second study found a relationship between higher vitamin D levels and a reduced risk of developing Parkinson’s disease. More than 3,000 Finnish men and women, age 50 to 79, participated in this study, which was conducted in a region of Finland with limited sunlight exposure. After 29 years of follow-up, 50 people developed Parkinson’s disease. “Our results are in line with the hypothesis that low vitamin D status predicts the development of Parkinson’s disease.” Put another way: The study showed the higher the blood levels of vitamin D, the less likely the participants would have symptoms of Parkinson’s disease.
The last study found that high consumption of foods rich in antioxidants is associated with lower risk of dementia. The authors of this study explain why they chose not to study antioxidant supplements: “Although clinical trials have shown no benefit of antioxidant supplements for Alzheimer’s disease, the wider variety of antioxidants in food sources is not well studied relative to dementia risk; a few studies, with varying lengths of follow-up, have yielded inconsistent results.”
The study included 5,300 Dutch people, age 55 years and older, who did not have dementia. All were given mental tests and if necessary, were evaluated by a neurologist and neuropsychologist. The meal-based checklist and food questionnaire they were expected to fill out regularly concentrated on four antioxidants: vitamin E, vitamin C, beta carotene and flavonoids. Here are the foods typically consumed by the study participants: The sources of vitamin E were primarily margarine, sunflower oil, butter, cooking fat, soybean oil and mayonnaise; vitamin C, mainly from oranges, kiwi, grapefruit juice, grapefruit, cauliflower, red bell peppers and red cabbage; beta carotene, from carrots, spinach, vegetable soup, endive, and tomatoes; and flavonoids from tea, onions, apples, and carrots. After 9½ years of follow-up, 465 of the study participants developed dementia, of whom 365 were diagnosed with Alzheimer’s disease. The study’s conclusion: “Higher intake of foods rich in vitamin E may modestly reduce long-term risk of dementia and Alzheimer’s disease.” The researchers said that they did not find an association between vitamin C, beta carotene, or flavonoides and a lower risk of dementia.
No firm conclusions, at this point:
Now for the caveats re all three studies. Whether a study is asking its participants about food intake or lifestyle habits like exercise, the resulting self-reporting is not always reliable. Questionnaires were central to all three studies. Also, none were randomized clinical trials. There’s a consensus among researchers that the best type of study is the clinical trial that randomly assigns participants to follow a special diet, or not, and follow them for years to see what happens. (It’s important to note here that dozens of such high-quality, vitamin vs placebo trials have failed to find a health benefit to taking supplements; in the case of antioxidant supplements, 90% of the trials with negative findings were funded by vitamin companies. click here)
The authors of each of the three studies offered plausible reasons for focusing on certain vitamins. For example, oxidative stress is thought to play an important role in the development of Alzheimer’s disease and antioxidants might offer protection. But researchers could be zeroing in on the wrong factor. Here’s an example relevant to the Finnish study: “Vitamin D levels are directly related to sunlight exposure and physical activity, and inversely related to adiposity [obesity],” wrote the editorialists for vitamin D studies. Drs. Andrew Grey and Mark Bolland, the editorialists, go on to suggest that the researchers could be barking up the wrong tree, so to speak. For example, less healthy people will be heavier and, less active, and more sunlight-deprived than healthier people and therefore show low blood levels of vitamin D. The implication: perhaps it’s the lack of exercise that accounts for the dementia rather than low levels of vitamin D or the obesity. Regular aerobic exercise is about the only research-supported preventive measure for Alzheimer’s disease. (So put down those crossword puzzles and move.)
Drs. Grey and Bolland also provided this caution about the current fad of taking large daily doses of vitamin D to prevent a wide range of ailments from obesity to diabetes 2. “Vitamin D supplementation does not reduce overall fracture risk and may increase the risk of the most serious fragility fracture, that of the proximal femur [thigh bone]. When co-administered with calcium supplements, vitamin D produces a marginal reduction in fracture risk that is comparable to that produced by calcium alone. Similarly, recent randomized controlled trials of vitamin D supplementation have failed to demonstrate positive effects on body weight, glycemic control in type 2 diabetes mellitus, incidence of type 2 diabetes, and incidence of respiratory infections.”
Bottom line: Until further notice, it seems like the best thing to do is eat real food rather than waste money on supplements. (click here for Michael Pollen’s book “Food Rules” that helps identify real food.)