CHAPEL HILL - Vitamin E and other naturally occurring antioxidants in the diet appear to protect against knee arthritis, a degenerative condition that will become an increasing national health problem as baby boomers age, a new University of North Carolina at Chapel Hill School of Medicine study shows.
The study, presented Monday (Nov. 9) at the American College of Rheumatology annual meeting in San Diego, suggests that middle-aged and older people might reduce the almost inevitable pain and restricted movement osteoarthritis causes by altering their diets.
"We analyzed blood serum from 200 people with knee osteoarthritis and compared their levels of various anti-oxidants with 200 control subjects who did not have the problem," said Dr. Joanne Jordan, research assistant research professor of medicine at UNC-CH's Thurston Arthritis Research Center. "We found vitamin E, also called alpha tocopherol, to be associated with about 30 percent lower risk of knee osteoarthritis in whites. We did not see a protective effect in blacks, but don't know why."
Beta cryptoxanthine, lutein and lycopene -- common in orange and green vegetables and tomatoes -- all appeared to reduce the odds of knee osteoarthritis by 30 percent to 40 percent, Jordan said. On the other hand, delta and gamma tocopherols - found in soybean, palm and other oils -- as much as doubled the risk of knee problems, particularly in blacks.
Subjects in the study were subgroups of 3,200 people participating in the university's continuing Johnston County (N.C.) Osteoarthritis Project, the first racially balanced, population-based study of the condition in whites and blacks. The UNC-CH researchers reported two years ago that excess weight created more functional problems for blacks than for whites.
Anti-oxidants, including carotenoids and tocopherols, are compounds many scientists believe have some natural ability to minimize tissue damage resulting from aging, smoking and other stresses on the body, Jordan said. Researchers think the compounds can neutralize and therefore counteract some harmful effects of charged particles known as oxygen free radicals.
Besides Jordan, other involved in the dietary research included Drs. Lenore Kohlmeier, professor of nutrition and epidemiology, and Jordan B. Renner, associate professor of radiology, and doctoral students Anneclaire DeRoos and Gheorghe Luta, all at UNC-CH. The only earlier comparable study did not include blacks and did not show an effect for vitamin E on arthritis.
"These new findings are exciting because they indicate some of these compounds may be very important, but obviously the work still is preliminary," Jordan said. "We and others need to do a lot more research with larger groups before we can say anything definitive about the relationship between diet and knee, hip and hand osteoarthritis."
Proving that diet can make a significant difference in arthritis would be important since most risk factors for the condition either cannot be modified, such as aging and heredity, or are changed only with difficulty, such as losing weight.
Future plans involve re-examining study participants, doing more extensive dietary assessments and studying both arthritis severity and progression. Jordan and her colleagues also will study such nutrients as Omega 3 fatty acids, vitamin D, vitamin K and others.
"Among strengths of the current study are that we looked at not just osteoarthritis patients, but a random sample of people over age 45 living in six communities and that a third of our study participants were African-American," Jordan said. "Half the participants in the diet substudy were black."
The Centers for Disease Control and Prevention and the National Institute of Arthritis, Musculoskeletal and Skin Diseases supported the continuing research in Johnston County.
Forty million Americans now suffer from arthritis, and that number is expected to jump to 60 million by the year 2020, she said.
Note: Jordan can be reached at 919-966-0559 (w) or at 383-0861 (h) until Saturday morning, Nov. 7. Beginning Saturday evening, she can be reached at the American College of Rheumatology meeting at the San Diego Marriott, 333 West Harbor Drive in San Diego, 619-234-1500. Her talk is in Room 3 of the Marriott at 4:30 p.m. Pacific Time. She will be back at her office Friday morning, Nov.13. Luta, who also worked in the study, can be reached at 919-966-9912.
Contact: David Williamson, 919-962-8596.