If you've been taking a vitamin E supplement in the hopes of defending your brain from Alzheimer's disease, consider eating more spinach and sunflower seeds instead.
According to a new study published this week in the Archives of Neurology, getting more vitamin E from your diet - not supplements - offers significant protection from the disease.
Alzheimer's disease is a progressive and degenerative brain disease that likely begins years, even decades, before the signs of impaired memory and thinking show up.
It's long been thought that oxidative stress - the damage to cells caused by free radicals - plays a key role in the development of Alzheimer's. Free radicals are highly reactive oxygen molecules routinely produced as a by-product of oxygen metabolism, but they can be created from cigarette smoke, sun exposure and air pollution.
The brain is especially susceptible to free radical damage because of its high demand for oxygen, abundance of easily oxidized fatty membranes, and its weak antioxidant defences.
In the lab, antioxidant nutrients, such as vitamins C and E, counteract harmful free radicals and therefore they may shield brain cells from degenerative damage. Evidence indicates that antioxidants may offer their protective effects in the early stages of dementia development.
Vitamin E has also been shown to lessen the toxic effects of beta-amyloid, a hallmark protein of Alzheimer's that accumulates and clumps in the brain.
In the current study - called the Rotterdam Study - researchers from the Netherlands followed 5,395 healthy men and women, aged 55 and older, for 10 years to evaluate the link between vitamin E, vitamin C, beta carotene and flavonoids with the long-term risk of dementia. (Flavonoids are natural compounds found in fruit, vegetables, tea and red wine that act as antioxidants.)
At the end of the study period, 465 participants had developed dementia, of which 78 per cent were Alzheimer's dementia. (Dementia can also be caused by atherosclerosis, stroke, head injuries, nutritional deficiencies and other health disorders.)
When it comes to fighting disease with antioxidants - be it Alzheimer's, heart disease or cancer - the evidence is stacked in favour of a diet providing a variety of nutrient - and antioxidant - packed foods, not supplements.
Participants whose diets provided the most vitamin E were 26 per cent less likely to develop Alzheimer's compared to those who consumed the least. Vitamin C, beta-carotene and flavonoids were unrelated to Alzheimer's risk.
Folks at the high end of the vitamin E intake range got, on average, 18.5 milligrams a day versus 9 mg for those at the low end. (Health Canada's recommended daily vitamin E intake for adults is currently 15 mg.)
Vitamin E is found in vegetable oils, margarine, nuts, seeds, wheat germ and leafy green vegetables. The major sources of the nutrient in this study were margarine, sunflower oil, butter, cooking fat, soybean oil and mayonnaise.
This isn't the first time vitamin E-rich foods have been shown to keep your mind sharp as you age.
Earlier this year, a large U.S. study of older adults revealed that eating a combination of foods - including salad dressing, nuts and leafy greens - reduced the risk of Alzheimer's by 38 per cent.
In 2009, a Mediterranean-style diet, rich in olive oil, nuts, beans and vegetables, was associated with up to a 40-per-cent reduced risk of Alzheimer's.
A 2006 report from the Chicago Health and Aging Study found that older women who ate the most vegetables, especially leafy greens, experienced a slower cognitive decline than those who consumed the least.
These results are promising, but don't be too quick to turn to vitamin E pills. Clinical trials have turned up disappointing results, showing that vitamin E supplements have no benefit for preventing Alzheimer's disease.
The conflicting findings of clinical trials using supplements and observational studies that measure people's dietary intake very likely have to do with the type of vitamin E studied.
Vitamin E is a family of eight natural compounds, all of which are found in food: four tocopherols (alpha-, beta-, gamma- and delta-) and four tocotrienols (alpha-, beta-, gamma- and delta-). All act as antioxidants and all have unique functions in the body.
Clinical trials, on the other hand, have evaluated only alpha-tocopherol, the form of vitamin E added to supplements.
It's possible, then, that you need all forms of vitamin E to protect from Alzheimer's, a balance you can only get from your diet.
A report published last week in the Journal of Alzheimer's Disease supports this theory. The study investigated whether higher blood levels of vitamin E could be protective against Alzheimer's and whether this protection was due to more than just the alpha-tocopherol form.
The researchers followed 232 healthy adults over the age of 75 for six years. Blood tests taken at the beginning of the study measured all eight vitamin E components.
People with higher blood levels of all members of the vitamin E family had a lower risk of developing Alzheimer's compared to people with lower levels. Those with the highest blood levels of total vitamin E had a 45-per-cent lower risk.
A higher blood level of alpha-tocopherol was linked with a protective effect, but this finding wasn't what researchers call statistically significant (it could have been a chance finding).
With respect to brain health, it would appear you need a combination of different forms rather than alpha-tocopherol alone.
So stick to food. When it comes to fighting disease with antioxidants - be it Alzheimer's, heart disease or cancer - the evidence is stacked in favour of a diet providing a variety of nutrient- and antioxidant-packed foods, not supplements.