LE Magazine September 2002
Two JAMA Studies Reveal That Antioxidants
Reduce Alzheimer's Risk
In the June 26, 2002 issue of the Journal of The American Medical Association (JAMA), two studies show that antioxidants can dramatically lower the risk of Alzheimers disease. The first study involved 5,385 participants who at baseline were at least 55 years old and were free of dementia. The investigators looked at the dietary intake of beta-carotene, flavonoids, vitamins C and E. After adjustments for other risk factors, the researchers found that the higher the intake of vitamins C and E, the lower the incidence of Alzheimers disease. For each single-digit increase in vitamin C and E consumption, there was a corresponding 18% decrease in Alzheimers disease incidence. When antioxidant intake of cigarette smokers was evaluated, Alzheimers risk was reduced by 35% with vitamin C, 42% with vitamin E, 46% with flavonoids and 51% with beta-carotene. The conclusion of the researchers was that high dietary intake of vitamin C and vitamin E may lower the risk of Alzheimer disease.
In the second JAMA study, researchers sought to ascertain if the intake of antioxidant nutrients, vitamin E, vitamin C and beta-carotene is associated with incident Alzheimers disease. The investigators examined 815 people 65 years of age and older who were free of dementia. The results showed a consistent reduction in Alzheimers risk with increasing intake of dietary vitamin E. Those with the highest intake of dietary vitamin E showed a remarkable 70% reduction in Alzheimers disease incidence. Interestingly, intake of vitamin E, C and beta-carotene supplements was not significantly associated with Alzheimers disease risk in this study. Dietary vitamin E is rich in the gamma tocopherol fraction of vitamin E, whereas vitamin E supplements consist primarily of alpha tocopherol. It is the gamma tocopherol fraction of vitamin E that has been shown to be the critical factor in suppressing free radicals. The brain is especially vulnerable to the toxic effects of free radicals because of its high-energy output. Notably, in this study, only those with a genetic predisposition for contracting Alzheimers disease (those whose genetic structure was without the APOE epsilon 4 allele) showed the remarkable protective benefit from dietary vitamin E.
In response to these studies, a leading nutritionist stated that Americans dont meet their requirements for vitamin E. Jeffrey Blumberg, professor of nutrition at Tufts University, was quoted in The Washington Post as saying, antioxidant nutrients provide a defense network against disease and it makes sense that antioxidants like vitamin E and C over the long term help to reduce the risk.
In the previous weeks issue of JAMA (June 19, 2002), two studies were published that endorsed the use of dietary supplements by healthy people as a way of reducing the risk of cancer, cardiovascular disease and osteoporosis. This was the first time that the American Medical Association officially recognized the benefits of dietary supplements in preventing disease.
Long-term consumption of folate prevents
Colorectal cancer is the third-leading cause of cancer death in adults in the U.S. In 2002, approximately 150,000 Americans will be diagnosed with colorectal cancer, over 56,000 will die from it. Despite medical advances, improvements in survival rates for patients with advanced stages of colorectal cancer have been minimal. Hence, researchers are focusing their attention on prevention. One promising preventive is the long-term consumption of folate.
A new study, led by Paul Terry, Ph.D. of Albert Einstein College of Medicine in New York and reported in the International Journal of Cancer [2002;Vol. 97;864-867], showed that women with diets high in folate reduced their risk of developing colorectal cancer. The long-term study evaluated the dietary habits of 57,000 women. After an average of 10 years, 389 of the participants developed colorectal cancer. Those subjects whose diets were higher in folate developed colorectal cancer at a lower rate.
In Terrys study, most participants consumed large amounts of folate through their diet. But another long-term study found an even greater reduction in colorectal cancer risk in women taking folic acid supplements.
In the famous Nurses Health Study, reported in the April 2001 issue of Harvard Womens Health Watch, women who took folic acid-containing multivitamins for at least 15 years were 75% less likely to develop colon cancer than those who did not. Key to the findings was the length during which participants took the supplements: only those who took folic acid-containing supplements for a minimum of 15 years lowered their risk of colorectal cancer.
Although the exact mechanisms by which folate helps protect against colorectal cancer are not clear, research points to its vital role in normal cell division and the repair of DNA damage.
Researchers Eichholzer and associates at the University of Zurich, evaluating studies on folates effects on the risk of colon cancer, report that folate appears most effective when taken through long-term supplementation. Research reviews by Molloy and associates at Trinity College in Dublin, Ireland concur with these findings.
Antioxidants: a possible preventative against
age-related macular degeneration
Age-related macular degeneration (AMD), which affects central vision and the ability to see detail, is a common condition among people over the age of 60. As life expectancies continue to rise, so too will the risk for developing macular degeneration. In the advanced stage of macular degeneration, cells within the macula begin to deteriorate, resulting in lost vision that cannot be regained. To date, therefore, the best hope for avoiding declining vision that accompanies macular degeneration lies in prevention. Breakthrough research points to the power of antioxidants as a possible preventative.
In a multi-center study sponsored by the National Eye Institute, researchers sought to determine if a long-term regimen of antioxidants would reduce the risk of advanced macular degeneration. Researchers followed subjects for an average of 6.3 years and found that those at high risk of developing advanced macular degeneration reduced their risk by approximately 25% when treated with a combination of antioxidants [Sackett CS et al, Insight 2002; Jan-Mar;27(1):5-7]. The following daily therapeutic dosages of nutrients were used in the study: vitamin C, 500 mg; vitamin E, 400 IU; beta carotene, 15 mg; and zinc, 80 mg.
In another study, researchers measured the level of serum and/or plasma antioxidants (vitamins C, E and A, total and individual carotenoids, and zinc) in subjects with advanced and early age-related maculopathy (ARM). They found that levels of vitamins C and E, and total carotenoids were lower in subjects with advanced age-related maculopathy than in those with early age-related maculopathy. Findings suggest that a deficit of antioxidants is associated with age-related maculopathy [Sionelli F et al, Clin Chim Acta 2002 Ju;320(1-2):111-115].
Now that we know antioxidants and zinc are helpful in reducing the risk of severe disease, it is even more important for older-age Americans to have regular eye exams. Intervening in at-risk individuals could help reduce severe disease and vision loss in millions of Americans, states Dr. Paul Sieving, Director of the National Eye Institute.
Tea protects against stomach and
Logic would suggest a protective role for tea against various gastrointestinal cancers. For example, UCLA scientists found that tea decreases stomach inflammation, thus reducing the risk of developing chronic gastritis, a condition that causes pre-cancerous lesions and can lead to stomach cancer over time [International Journal of Cancer 2001 May;92:600-604]. Their study of over 600 Chinese men and women showed that green tea drinkers had a 48% lower risk of stomach cancer than non-drinkers. An earlier epidemiological study of 902 cancer patients and 1,552 healthy controls showed that green tea reduced the risk of esophageal cancer in women by 50%, and in non-smoking men and women by 60% [J Natl Cancer Inst 1994 Jun 1; 86(11):855-8]. Both studies found that risk decreased as tea consumption increased.
However, some scientists suspect that tea drinkers may also have other healthier lifestyle factors that may help reduce their disease risk and confound any tea benefit. A team of U.S. and Chinese researchers, who presented new findings at the 93rd annual meeting of the American Association for Cancer Research (AACR), says it now has direct evidence of teas cancer-fighting abilities. They compared levels of tea polyphenols and several by-products (measured in urine) among 190 cases of gastric cancer, 42 cases of esophageal cancer and 772 healthy controls. The investigators found that tea drinkers had half the risk of cancer as light- to non-drinkers, even after factoring in other health behaviors, such as smoking, drinking, dietary carotene intake and the presence of H. pylori (the bacteria that causes stomach ulcers).
High C-reactive protein points to Alzheimer's risk
There may be more to a key protein found in the body than first meets the eye, when it comes to predicting disease. C-reactive protein, whose presence has long been known as an inflammatory marker and predictor of cardiovascular disease, may also serve as a warning sign for the onset of certain dementias like Alzheimers [Ital Heart J 2001 Nov;2(11):804-6; Circulation 1998 Feb 10;97(5):425-8; Am J Clin Pathol 2001 Dec;116 Suppl:S108-15].
A prospective study found that high levels of C-reactive protein may warn of an increased risk of dementia years ahead of time because it indicates the presence of vascular inflammation [Annals of Neurology 2002 Aug].
The inflammation related to disease risk may simply be the bodys way of responding to the disease itself, says Lon White, M.D., senior neuroepidemiologist at Pacific Health Research Institute in Honolulu, and a study co-author. As tissue in the brain is lost with dementia, the body could respond to those losses with inflammatory processes.
Researchers compared serum levels of C-reactive protein to risk of developing dementia in 1,050 men over a 25-year period. Compared to men with the lowest levels of the protein, those with the highest level had triple the risk of developing dementias, even long before clinical symptoms appear, the authors note.
Other studies have hinted at C-reactive proteins possible link to the risk of ischemic stroke and the more subtle stroke-like disorder known as transient ischemic attack [Stroke 2001 Nov;32(1):2575-9].
White says its another piece in a complex puzzle. Were trying to. . . put together what the sequence of events is that leads to heart disease, stroke, neurodegenerative diseasesespecially in late lifeso that we can begin to put together the most intelligent approach to modify those pathogenic processes early on. . . he says.
This study corroborates the need to protect against chronic inflammation.
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