Antioxidants in your diet may not reduce risk of stroke or dementia

Contrary to other research, a new study found that the total level of antioxidants in people's diets is not related to their risk of developing stroke or dementia. The study is published in the February 20, 2013, online issue of Neurology, the medical journal of the American Academy of Neurology. Antioxidants such as lycopene, beta-carotene and vitamins C and E are found in many foods.

21 feb 2013--"These results are interesting because other studies have suggested that antioxidants may help protect against stroke and dementia," said study author Elizabeth E. Devore, ScD, of Harvard Medical School in Boston and Erasmus Medical Center in Rotterdam, Netherlands. "It's possible that individual antioxidants, or the main foods that contribute those antioxidants—rather than the total antioxidant level in the diet—contribute to the lower risk of dementia and stroke found in earlier studies."

The study involved 5,395 people age 55 and older who had no signs of dementia at the start of the study. Participants completed questionnaires about how often they ate 170 foods over the past year at the start of the study. Then the participants were followed for an average of nearly 14 years.

Participants were divided into three groups: low, moderate and high levels of antioxidants in the diet. About 600 people developed dementia during the study and about 600 people had a stroke. But researchers found that people with high levels of antioxidants were no more or less likely to develop brain disease than people with low levels of antioxidants.

Devore noted that about 90 percent of the difference in antioxidant levels in the study was due to the amount of coffee and tea people drank. Coffee and tea contain high levels of nontraditional antioxidants such as flavonoids.

"This differed from an Italian study that found the higher total antioxidant levels were associated with a lower risk of stroke, where the variation from coffee and tea was lower, and the contribution from alcoholic beverages, fruits and vegetables was higher," Devore said.

Provided by American Academy of Neurology

Antioxidants may raise diabetes risk: study

CHICAGO, 07 oct 2009– Instead of protecting against diabetes, antioxidants -- compounds in foods and supplements that prevent cell damage -- may actually increase the chances of getting diabetes, at least in the early stages, Australian researchers reported on Tuesday.

"In the case of early type 2 diabetes ... our studies suggest that antioxidants would be bad for you," Tony Tiganis of Monash University in Australia, whose study appears in the journal Cell Metabolism, said in a statement.

Antioxidants are protective proteins that can prevent cell damage caused by charged particles known as reactive oxygen species. This oxidative stress is thought to add to the progression of several diseases, including type 2 diabetes.

Because antioxidants fight oxidative stress, they have become a popular food supplement. But Tiganis said the picture appears to be a bit more complicated.

"We think there is a delicate balance, and that too much of a good thing -- surprise, surprise -- might be bad," he said.

Tiganis' team studied the effects of oxidative stress in mice fed a high-fat diet for 12 weeks. One group of mice lacked an enzyme known as Gpxl, which helps counter oxidative stress.

They found mice that lacked the enzyme were less likely to develop insulin resistance -- an early sign of diabetes -- than normal mice. But when they treated the enzyme-deficient mice with an antioxidant, "they lost this advantage and become more 'diabetic," Tiganis said in an e-mail.

He said oxidative stress may be working not to damage the body but to inhibit enzymes that hurt the body's ability to use insulin early on in the development of diabetes, and that antioxidants remove this protective mechanism.

"Our work suggests that antioxidants may contribute to early development of insulin resistance, a key pathological hallmark of type 2 diabetes," Tiganis said.

He cautioned that the study was in mice and more study in people is needed.

But he said other studies have suggested that antioxidants can shorten lifespan in both worms and humans. And clinical trials in people have shown that taking antioxidants does not protect healthy people from developing diabetes.

"My belief is that individuals who are otherwise healthy should not take antioxidants, but rather eat healthy and exercise," he said.

An estimated 23.6 million people in the United States and 246 million people globally have diabetes. Most have type 2, the kind linked with a poor diet and lack of exercise.

Antioxidant Vitamins May Increase Mortality

The largest analysis of data on antioxidant vitamins ever conducted has shown that beta-carotene, vitamin A, and vitamin E probably increase mortality. Two other antioxidant substances — vitamin C and selenium — had no effect on mortality.
The meta-analysis of 68 randomized trials with a total of 232,606 participants, published in the February 28 issue of JAMA, was conducted by a group led by Goran Bjelakovic, MD, of the Copenhagen University Hospital in Denmark.
Coauthor, Christian Gluud, MD, of the Copenhagen University Hospital in Denmark, commented to heartwire: "This is the most comprehensive collection of data on anti-oxidant vitamins ever conducted, and we have shown that on the whole that these agents have no benefit. Indeed, vitamin A, vitamin E and beta-carotene are associated with an increase in mortality at the doses studied. Vitamin A and beta-carotene seem to have a dose-related effect, with mortality increasing as doses increase, whereas vitamin E does not appear to have a dose-related effect, with all doses associated with increased mortality."
Jury Still Out on Vitamin C and Selenium
Dr. Gluud added that the jury is still out on vitamin C and selenium. "Vitamin C does not appear to be detrimental but it is not beneficial either, and all the trials of selenium together suggest a small benefit, but when only the well conducted trials are included, there appears to be neither benefit nor harm." "Our data show that anti-oxidant vitamins should not be taken in an effort to prevent illness. People should instead eat a balanced diet and take regular exercise," he said.
In the JAMA article, the authors note that many people are taking antioxidant supplements in the belief that they improve health and prevent diseases. Many primary or secondary prevention trials of antioxidant supplements have been conducted to prevent several diseases — mainly cardiovascular disease and cancer — but results have generally not been positive, with some trials showing increases in mortality.

http://www.medscape.com/viewarticle/552910?sssdmh=dm1.261632&src=top10#

Another Supplement, Under the Microscope

Not so long ago, antioxidant vitamins were hailed as nature’s own weapons against chronic illness, powerful antidotes to horrid diets and failed exercise plans.
A parade of observational studies showed that people who consumed large amounts of vitamins C and E and beta carotene were usually healthier than those who ingested comparatively little. Almost overnight, it seemed, millions of consumers morphed into fervid pill poppers, and antioxidants were dolloped into an ever expanding variety of foods.
But recent and more rigorous research suggests that this silver bullet missed its mark. Most long-term prospective trials have shown that using antioxidant vitamin supplements does not prevent heart disease or cancer, with the possible exception of prostate cancer.
In a study published last month in The Journal of the American Medical Association, researchers in Europe analyzed data from 68 large trials in which more than 232,000 adults were given antioxidant supplements.

http://www.nytimes.com/2007/03/13/health/13cons.html?ex=1331438400&en=4e5836186289a10d&ei=5088&partner=rssnyt&emc=rss