Some conflicting news this week about the health benefits of grapes and wine, and whether compounds in the fruit can help reduce pain, inflammation and cardiovascular disease.
A small study conducted at Texas Woman’s University found that regular grape consumption may help alleviate pain associated with osteoarthritis of the knee, as well as improve joint flexibility and overall mobility. Researchers who presented the study at the Experimental Biology conference in San Diego attribute the health benefits to high levels of polyphenols found in grapes.
“These findings provide promising data that links grape consumption to two very important outcomes for those living with knee osteoarthritis: reduced pain and improvements in joint flexibility,” said lead investigator Shanil Juma, PhD, an assistant professor in the Department of Nutrition and Food Sciences at Texas Woman’s University.
Juma and her colleagues enrolled 72 men and women with knee osteoarthritis (OA) in a 16-week clinical study. They were assigned to either consume a freeze-dried powder made from whole grapes, or a placebo powder.
Both men and women who consumed the grape powder had a significant decrease in self-reported pain and a decrease in OA knee symptoms. The beneficial effect was more pronounced in females.
Participants under the age of 64 who consumed the grape powder also had a 70% increase in their hard physical activity, while those receiving the placebo reported a significant decrease in hard activity. Participants 65 and older reported a decline in both moderate and hard activity, whether they consumed grapes or the placebo.
Evidence of increased cartilage metabolism was observed in men on the grape-enriched diet. They had higher levels of a cartilage growth factor (IGF-1) than those on placebo. But the protective effect was not observed in the females.
A serum marker for inflammation increased in both the placebo and grape groups, although much less of an increase was observed in the grape group.
“More research is needed to better understand the results of the serum biomarkers, as well as the age and gender differences observed,” said Juma.
Nearly 27 million Americans suffer from OA, a common degenerative joint disease that causes pain and swelling of joints in the hand, hips, or knee. OA of the knee is more prevalent and severe in women.
Polyphenols are naturally occurring antioxidant compounds found in fruits, vegetables, dry legumes, cereals, nuts and chocolate. Wine, tea and other beverages made from these products also contain polyphenols in significant amounts. Clinical studies suggest that long term consumption of plant polyphenols offer protection against cancer, cardiovascular disease, diabetes, osteoporosis and neurodegenerative diseases.
Resveratrol – another antioxidant compound found in grapes and wine – has also been associated with health benefits. But according to a new study of Italians who consume a diet rich in resveratrol, people live no longer and are just as likely to develop cardiovascular disease or cancer than those who consumer smaller amounts of the antioxidant.
“The story of resveratrol turns out to be another case where you get a lot of hype about health benefits that doesn’t stand the test of time,” says Richard Semba, MD, a professor of ophthalmology at the Johns Hopkins University School of Medicine. “The thinking was that certain foods are good for you because they contain resveratrol. We didn’t find that at all.”
Semba is part of an international team of researchers that for 15 years studied the effects of aging on people who live in two Italian villages. Researchers analyzed 24 hours of urine samples from 783 people over the age of 65 for metabolites of resveratrol.
Those with the highest concentrations of resveratrol metabolites were no less likely to have died of any cause than those with no resveratrol in their urine. The concentration of resveratrol was also not associated with inflammatory markers, cardiovascular disease or cancer.
The study participants live in the Chianti region of Tuscany where consumption of red wine — a specialty of the region — is the norm.
“This prospective study of nearly 800 older community-dwelling adults shows no association between urinary resveratrol metabolites and longevity. This study suggests that dietary resveratrol from Western diets in community-dwelling older adults does not have a substantial influence on inflammation, cardiovascular disease, cancer, or longevity,” the authors reported in the journal JAMA Internal Medicine.
In addition to grapes and wine, resveratrol is also found in relatively large amounts in peanuts and some Asiatic plant roots. Excitement over resveratrol’s health benefits followed studies that documented its anti-inflammatory effect in lower organisms and increased lifespan in mice fed a diet rich in the compound. Some preliminary evidence also suggests that resveratrol may prevent cancer and decrease the stiffness of blood vessel.
The so-called “French paradox,” in which a low rate of coronary heart disease occurs in people with a high dietary intake of cholesterol and saturated fat in France, has been attributed to the regular consumption of resveratrol and other polyphenols found in red wine.