In a large epidemiological study, researchers found that people who drank three or more servings of fruit and vegetable juices per week had a 76 percent lower risk of developing Alzheimer’s disease than those who drank juice less than once per week.
The study by Qi Dai, M.D., Ph.D., assistant professor of Medicine, and colleagues appears in the September issue of The American Journal of Medicine.
The researchers followed a subset of subjects from a large cross-cultural study of dementia, called the Ni-Hon-Sea Project, which investigated Alzheimer’s disease and vascular dementia in older Japanese populations living in Japan, Hawaii and Seattle, Wash.
For the current study, called the Kame Project, the researchers identified 1,836 dementia-free subjects in the Seattle population and collected information on their dietary consumption of fruit and vegetable juices. They then assessed cognitive function every two years for up to 10 years.
After controlling for possible confounding factors like smoking, education, physical activity and fat intake, the researchers found that those who reported drinking juices three or more times per week were 76 percent less likely to develop signs of Alzheimer’s disease than those who drank less than one serving per week.
The benefit appeared particularly enhanced in subjects who carry the apolipoprotein E ˙-4 allele, a genetic marker linked to late-onset Alzheimer’s disease – the most common form of the disease, which typically occurs after the age of 65.
A diet that cuts Alzheimer's risk probably cuts stroke and heart disease risk as well.
Researchers have found that vitamins C, E, and beta carotene do not provide a neuroprotective effect against Alzheimer's. Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) also have been found to provide little or no benefit. The researchers behind this study suspected that perhaps polyphenols in foods provide benefit.
Dai began to suspect that another class of antioxidant chemicals, known as polyphenols, could play a role. Polyphenols are non-vitamin antioxidants common in the diet and particularly abundant in teas, juices and wines. Most polyphenols exist primarily in the skins and peels of fruits and vegetables. Recent studies have shown that polyphenols (like resveratrol in wine) extend maximum lifespan by 59 percent and delay age-dependent decay of cognitive performance in animal models.
"Also, animal studies and cell culture studies confirmed that some polyphenols from juices showed a stronger neuroprotective effect than antioxidant vitamins. So we are now looking at polyphenols," Dai said.
The researchers intend to check blood polyphenol levels to see if high polyphenols correlate with low Alzheimer's risk.
The nomenclature here may seem confusing. Catechins in tea are both polyphenols and flavonoids. Polyphenols are a larger set of chemical compounds which includes flavonoids as a subset. Then within the subset called flavonoids exists the smaller subset catechins. Fruits have flavonoids called anthocyanins. Tea and wine (and presumably dark grape juice) contain flavonoids called catechins.
Obvious question: Was the protective effect against Alzheimer's seen in this study due to catechins from tea and grape juice or from anthocyanins found in fruits? Or perhaps from other flavonoids called flavones and flavonols? Or other polyphenols? Or some combination of the above? I'm sorry I do not have an answer for you.
One obvious question: Drink the juice or eat whole fruits and vegetables? Well, juices appear to work (see above) and are quicker to consume. But perhaps the people who consume more fruit and vegetable juices also eat more fruits and vegetables. It is not clear what confounding factors these researchers controlled for.
Writing in the article, Qi Dai, MD, PhD, states, “We found that frequent drinking of fruit and vegetable juices was associated with a substantially decreased risk of Alzheimer’s disease. This inverse association was stronger after adjustments for potential confounding factors, and the association was evident in all strata of selected variables. These findings are new and suggest that fruit and vegetable juices may play an important role in delaying the onset of Alzheimer’s disease”.
I find it really surprising that these researchers could find an influence from juices above the background of all the other factors that will influence polyphenol content of diet.
Enormous amounts of other research has been done on the health benefits of polyphenols including flavonoids. Green tea catechins might reduce the risk of prostate cancer.
Anaheim, Calif. – After a year's oral administration of green tea catechins (GTCs), only one man in a group of 32 at high risk for prostate cancer developed the disease, compared to nine out of 30 in a control, according to a team of Italian researchers from the University of Parma and University of Modena and Reggio Emilia led by Saverio Bettuzzi, Ph.D.
The 600 mg-per-day dosage of caffeine-free, total catechins (50 percent of which is EGCG) given to participants in the Italian study is one or two times the amount of green tea consumed daily in China, where ten to 20 cups a day is normal.
I do not want to drink 10, let alone 20, cups of green tea a day. I'd rather take some caffeine-free catechin capsules. Better yet, I'd rather figure out which fruits and vegetables would deliver the same benefits and eat them instead.
Green tea is very popular in Japan and its consumption there might be the cause of lower Alzheimer's in Japanese in Japan as compared to Japanese in America.
Another paper which reported a reduction in blood plasma peroxide free radicals with green tea extract found a higher concentration of catechin polyphenols per cup of green tea.
"We believe we have shown for the first time the course change of both green tea catechin levels in human plasma as well as human plasma lipid peroxide levels after oral green tea catechin supplementation, " said Teruo Miyazawa, Ph.D., biodynamic chemistry professor at the Tohoku University Graduate School of Life Science and Agriculture and the study's principal investigator.
In the study, 18 healthy male subjects between the ages of 23 and 41 ingested green tea extracts in tablet form (including 254 milligrams of catechins per subject - one cup of green tea contains about 100 to 150 milligrams of catechin). All of the subjects avoided tea and tea-related beverages for 12 hours prior to the testing. Blood samples were taken one hour before and after the catechin ingestion.
I'd love to see a massive comparison study of a wide range of fruits and vegetables, juices, teas, and cocoa (which also contains catechins) where the effects of each food on blood plasma peroxides, blood pressure, and other indicators were compared. What are the most potent foods to eat?
The 806 male participants, averaging age 71 in 1985, were followed until 1995, with complete dietary and medical examinations in 1985 and 1990. Epidemiological evaluation of the health effects of catechins has previously been difficult due to the lack of information on the exact catechin composition of foods. For this study, the authors measured the catechin content of 120 frequently consumed plant foods, using the data to divide the subjects into low, medium and high quintiles of catechin consumption.Among the men in the highest quintile, 87% of catechins in the diet came from black tea; whereas those in lower quintiles ate more foods in which catechins were less concentrated. High catechin intake was associated with other practices characteristic of a healthy lifestyle, such as refraining from smoking, eating more fruits and vegetables, and increased activity levels.
For examples of more on the health benefits of tea see these research reports: Tea Intake Is Inversely Related to Blood Pressure in Older Women and Black and Green Tea Polyphenols Attenuate Blood Pressure Increases in Stroke-Prone Spontaneously Hypertensive Rats.
Green tea is hardly the only food that can improve blood flow and reduce blood free radicals. For example, see the research paper: Wine Polyphenols Decrease Blood Pressure, Improve NO Vasodilatation, and Induce Gene Expression. The "NO" in the title refers to Nitric Oxide which is a naturally occurring vasodilator (i.e. it makes blood vessels widen which lowers blood pressure). Nitric oxide deficiency is, in all likelihood, a cause of high blood pressure. Some drugs release NO as their mechanism of action. Viagra and Cialis work by releasing NO to cause blood to flow in the right places for male sexual function. Minoxidil, the anti-hair loss drug, has the "nox" in its name because it too is an NO releaser. But better to raise your vascular NO by diet before resorting to drug use. The foods that'll improve NO will also deliver other benefits.
|Share |||Randall Parker, 2006 September 02 10:13 AM Aging Diet Brain Studies|