News Review From Harvard Medical School -- Complex Links between Antioxidants and Brain
A study has found no link between stroke and dementia rates and the amount of antioxidants people get from their diets. That's a different conclusion from some other studies. Researchers suggest that the new results show the source of antioxidants is important. The study included about 5,400 people, age 55 or older. They didn't have dementia when the study began. Only about 100 had ever had a stroke. People filled out questionnaires about what they usually ate and drank. In the next 14 years, 599 developed dementia and 601 had a stroke. There was no difference in stroke or dementia rates between people who consumed more or fewer antioxidants. Coffee and tea drinking was the main difference in diet for people who consumed the most antioxidants. These drinks contain antioxidants known as flavonoids. Other research has found lower stroke and dementia rates for people who consumed more antioxidants from fruits and vegetables. The journal Neurology published the new study online. HealthDay News wrote about it February 20.
By Robert H. Shmerling, M.D.
Harvard Medical School
What Is the Doctor's Reaction?
It's hard to escape the news stories and advertisements about the health benefits of antioxidants. And the message is clear: You'd better be getting plenty of them!
But have you ever wondered why antioxidants are supposed to be good for you? Antioxidants help protect cells from free radicals. Free radicals are chemicals that can damage cells and genetic material.
There are several sources of free radicals. They are byproducts of chemical reactions that turn food into energy. They are found in certain foods and in the air. The body also creates them in response to sun exposure. So you are bound to be exposed to free radicals. But antioxidants are thought to provide some measure of protection.
Examples of antioxidants include:
- Vitamin C
- Vitamin E
- Beta carotene
What are the supposed health benefits of a diet high in antioxidants? The list is impressive, including reduced risks of:
- Heart disease
- Cataracts and macular degeneration
- Memory loss
Most of the studies that suggest these health benefits of antioxidants were done in the same way. They compared the diets of people with and without a disease (such as dementia) and found lower rates of disease among those who consumed more of at least one antioxidant. These findings have led to much promotion of antioxidants as a way to prevent disease.
But each antioxidant is unique. So it's not clear whether one antioxidant or all of them are responsible for the health benefits shown in some past studies.
Researchers studying brain disease attempted to sort this out. The study included nearly 5,400 people ages 55 or older. They did not have signs of dementia. Nearly all were free of stroke. Everyone answered detailed surveys about what they ate during the prior year.
Researchers kept track of people for about 14 years. They found that people who did or did not develop dementia consumed about the same amount of foods containing antioxidants. There was also no difference in these foods between people who had strokes and people who didn't.
An earlier study found a link between antioxidant intake and a lower stroke risk. That study attributed the benefit to consuming more alcohol, fruits and vegetables. In this new study, people consumed more antioxidants mainly because of the coffee and tea they drank. Coffee and tea contain high levels of flavonoids.
Together, these studies suggest the type of antioxidant may matter more than the total amount.
This study is a good example of how simple notions about health may be incorrect. The relationship between antioxidant intake and disease is complex. It takes high-quality research to sort out the important details.
What Changes Can I Make Now?
Despite all the hype, the best studies of antioxidants have not found the reductions in disease that doctors had hoped to see. In fact, one study found a higher rate of lung cancer among heavy smokers who took beta-carotene. Another trial found a higher rate of skin cancer for women taking antioxidant pills.
None of this has stopped advertisers from using antioxidants as a selling point for supplements, energy drinks and even breakfast. So the first change you can make is to think twice before getting on the antioxidant bandwagon. Clearly, we don't have a complete understanding of their health effects.
Fortunately, you can take other measures that might reduce your risk of stroke and dementia.
- Get more exercise. Being inactive is linked with higher risks of stroke and Alzheimer's disease.
- Eat healthier foods. A diet that is rich in fiber, fruits, vegetables and omega-3 fatty acids has been linked to a lower risk of Alzheimer's disease. Cutting back on salt may reduce the risk of stroke related to high blood pressure.
- Try to maintain a healthy weight. Obesity increases the risk of high blood pressure, diabetes and other factors that raise the risk of stroke.
- Don't smoke. If you have trouble quitting on your own, a smoking cessation program, medicines or both can help.
- Get your blood pressure and cholesterol checked. If either remains high, talk to your doctor about treatment options.
- If you have diabetes, get it treated. Tight control of your blood sugar and other routine treatments can lower your risk of related problems, including stroke.
- If you have atrial fibrillation, see your doctor regularly for monitoring and treatment. A blood thinner may lower your risk of stroke.
- Keep your mind busy. Dementia seems to be less common among those with a busy social life and hobbies.
If you take antioxidants now, talk to your doctor about this study and whether you should keep taking them.
What Can I Expect Looking to the Future?
You can expect continued debate about which antioxidants are best, how you should get them (food or pills) and how much you should take. Future research should clear up the role of antioxidants in health and disease. But, regardless of the results, you can expect to see advertisers continue to promote antioxidants as long as it increases sales.