New study is first to show that risk of childhood obesity may be reduced by treating pregnant woman for gestational diabetes

New study confirms link between breast cancer and hormone therapy

New Study Finds Breast Cancer Survivors Don’t Need to Increase Fruits and Vegetables beyond National Guidelines

Kaiser Permanente’s Center for Health Research 2007 Saward Lecture

Kaiser Permanente’s Center for Health Research Wins $2.76 Million Award to Study Long-Term Oxygen Treatment for Patients with COPD

National Study Shows Patients with Chronic Obstructive Pulmonary Disease and Asthma Receive Only Half of Recommended Care

Kaiser Permanente Study Shows Flu Vaccine Safe for Young Children

Kaiser Permanente’s Center for Health Research Launches Two New Smoking Cessation Studies

OHSU, Kaiser Permanente Northwest Partner to Win $55 Million Grant to Transform Medical Research

Using Safety Alerts in Electronic Medical Records Reduces Rates of Potentially Dangerous Medication Interactions

Kaiser Permanente of Georgia to merge research program

Making longer-term lifestyle changes lowers rates of high blood pressure and risk of heart disease

What's New - Vitamin Supplements

Oregon researchers reviewed studies used to make recommendations

Little Evidence Found That Vitamin Supplements Prevent Cancer or Heart Disease

(PORTLAND, Ore.) - The U.S. Preventive Services Task Force today concluded there was insufficient scientific evidence to recommend vitamin supplements as a way to prevent cancer or heart disease and recommended against the use of beta carotene supplements in smokers because of a possible increased risk of lung cancer and death.

The Task Force based its conclusion on a report created for the Agency for Healthcare Research and Quality (AHRQ) by a team of researchers at the Oregon Evidence-based Practice Center (EPC). The Oregon EPC is a collaboration among Oregon Health & Science University, Kaiser Permanente's Center for Health Research and the Portland Veterans Administration Medical Center and is directed by Mark Helfand, M.D., M.P.H., an associate professor of medicine in the OHSU School of Medicine.

Researchers analyzed the use of vitamins A, C, or E, multivitamins with folic acid, or antioxidant combinations to reduce the risk for cancer or cardiovascular disease in adults. This marks the first time the Task Force has reviewed studies on the effect of vitamins to reduce cancer and cardiovascular disease.

The report on nutrition's role in the development of cardiovascular disease was published in the July 1 issue of the Annals of Internal Medicine and authored by Cynthia Morris, Ph.D., M.P.H., professor and vice chairman of the department of medical informatics and clinical epidemiology in the OHSU School of Medicine. Cheryl Ritenbaugh, Ph.D., M.P.H., senior investigator at Kaiser Permanente's Center for Health Research, authored the analysis of the role of vitamins in prevention of cancer, which was published on the AHRQ Web site.

Based on the Oregon EPC's analysis of four clinical trials, the Task Force found that taking beta carotene did not decrease the risk for lung, prostate, colon, breast, or non-melanoma skin cancer in middle-aged and older adults. Two of these clinical trials found that individuals who take beta carotene and smoke have an increased risk of lung cancer and death.

"Despite immense popular interest in vitamin supplements to prevent cancer, surprisingly few - more - observational studies or clinical trials focus directly on the topic," said Ritenbaugh. "There were only 10 published placebo-controlled trials - the strongest possible evidence - available for analysis, and these covered only a handful of vitamins and beta carotene. They provide little convincing evidence that vitamin supplements can prevent cancer. However, several studies now underway in Portland and elsewhere will give us more information and a clearer picture in the coming years about the role of nutritional supplements in preventing cancer."

The Oregon EPC analyzed both randomized trials and observational studies, to help the Task Force determine whether taking vitamins A, C, or E, multivitamins with folic acid, or antioxidant combinations reduced risk of heart disease, stroke or various cancers. The best studies suggested no clear benefit of taking vitamins, but the number and length of the studies was insufficient to rule out possible benefits of long-term vitamin use. Although some of the observational studies suggested possible benefits for some cancers, the Task Force could not determine whether these benefits were due to vitamins or to healthier lifestyles in people who take vitamins. They also did not review evidence on the use of vitamins for patients with known nutritional deficiencies, pregnant and lactating women, children, the elderly, and people with chronic illness. Vitamins may be more appropriate for people in these groups, and the Task Force urges those patients to talk with their clinicians about the potential benefits and harms of using vitamins.

"In long term observational studies that looked at supplements people took as well as lifestyle factors such as smoking habits and education, antioxidant supplements appeared to protect against a major cardiovascular event," Morris said. "However, in studies where those at risk for cardiovascular disease received either a supplement or a placebo, antioxidants did not prevent the first occurrence or a recurrence of a cardiovascular event, such as a heart attack. We think that this difference is because people who choose to take vitamins more often have positive health practices and higher socioeconomic levels than those who do not take vitamins."

Moderate doses of vitamin A may reduce bone mineral density, and high doses may cause liver damage or in pregnant women, harm to a fetus. The Task Force recommends that patients who take vitamins not take more than the Recommended Daily Allowance and talk to their clinician about the effects vitamins may have on their health. The Task Force grades the strength of the evidence from "A" (strongly recommends), "B" (recommends), "C" (no recommendation for or against), "D" (recommends against) or "I" (insufficient evidence to recommend for or against screening). The Task Force recommends against the use of beta carotene supplements, either alone or in combination, for the prevention of cancer or cardiovascular disease (a "D" recommendation).

The Task Force found insufficient evidence to recommend for or against the use of supplements of vitamins A, C, or E, multivitamins with folic acid, or antioxidant combinations for the prevention of cancer or cardiovascular disease (an "I" recommendation).

The Task Force, the leading independent panel of private-sector experts in prevention and primary care, conducts rigorous, impartial assessments of all the scientific evidence for a broad range of preventive services. To access the Task Force recommendation, visit: www.ahrq.gov/clinic/3rduspstf/vitamins/vitaminsrr.htm.

For more infomation contact:
Terry Fitzpatrick, CHR, 503.335.6602 or
Rachel MacKnight, OHSU, 503.494.8231 or macknigh@ohsu.edu

Released: June 30, 2003