Diet & Health Study News - Fall 2007
Published for Study Participants by the National Cancer Institute (PDF version 477 kb)
A Heartfelt Thanks
The NIH-AARP Diet and Health Study is still going strong thanks to your help! The study is now in its 13th year. Thanks to your participation, researchers have a better understanding of how health behaviors are related to cancer and other diseases. In the past year, we’ve published two dozen articles in scientific journals on topics such as body weight and mortality, dietary fat and breast cancer, artificial sweeteners and lymphoma, multivitamins and prostate cancer, and menopausal hormone therapy and ovarian cancer. (Some of these reports will be discussed below.) Many of these scientific articles have received extensive publicity in the media. More importantly, the study results represent an enormous contribution to public health!
As time goes by, we want to continue to be in contact with you every year. More and more people are communicating using e-mail and the internet on the computer and we invite you to stay up-to-date with the study at our website: http://dietandhealth.cancer.gov/. The website also has a link to summaries of the latest scientific articles from the study.
In order to share some of what we have learned, we present results from two research studies below. Once again, thank you for your continued time and participation in this research.
Arthur Schatzkin, M.D., Dr.P.H.
NIH-AARP Diet & Health Study
Weight Change and Prostate Cancer
By Wright, Chang, Schatzkin et al., Cancer, February 15, 2007
Obese men have a higher risk of dying from prostate cancer than men of normal weight, according to new findings from the NIH-AARP Diet and Health Study. Men who reported weight gain after age 18 were also found to be at increased risk of dying from prostate cancer. These findings did not change when age, family history of prostate cancer, race, or past screening history were accounted for. The most likely explanation underlying the observed association is that heavier men have hormonal alterations that adversely affect prostate cancer progression leading to death.
A total of 287,760 male study participants were included in this analysis. Men were between 50 and 71 years of age at the start of the study in 1995-1996, at which time they filled out questionnaires that asked about height, weight, and other factors, as well as cancer screening practices. The authors of this study looked at body mass index (BMI), which was calculated from height and weight. They also examined weight change from age 18 years to baseline (1995-1996). Approximately 29 percent of men were classified as normal weight (BMI<25 kg/m2), 50 percent as overweight (BMI 25-29.9 kg/m2), and 21 percent as obese (BMI>30 kg/m2). During five years of follow-up, 9,986 cases of prostate cancer were identified. During six years of follow-up, 173 prostate cancer deaths occurred.
This study had several strengths, including the large number of men with prostate cancer, a wide range of reported weights, and the ability to determine if any other factors affected the association between BMI and prostate cancer risk. These study results add to the growing evidence that obesity increases the risk of fatal prostate cancer. Also, this is the first prospective study to identify increasing weight after age 18 as a risk factor for prostate cancer death. The authors conclude that maintaining a healthy weight through diet and exercise is not only pertinent to reducing the risk of prostate cancer death, but is also beneficial for many other health conditions.
These study results supplement other studies showing similar results about the relationship of obesity to prostate cancer occurrence and death, suggesting another reason for public concern about obesity found in the U.S. and around the world.
High Fat Diets and Breast Cancer after Menopause
By Thiébaut, Kipnis et al., Journal of the National Cancer Institute, March 21, 2007
Fat consumption was shown to be directly related to invasive breast cancer in women who have gone through menopause in the NIH-AARP Diet and Health Study.
In total, 188,736 women in the NIH-AARP Diet and Health Study who had gone through menopause were included in this analysis. These women completed the 1995-1996 baseline questionnaire that included 124 questions about foods eaten over the previous year. Women reported diets ranging from very low fat (below 20% of calories from fat) to very high fat (above 40% of calories from fat). During the five-year follow-up period, 3,501 women were diagnosed with invasive breast cancer.
The study showed a significant link between high fat diets and breast cancer. As fat intake in the diet increased, so did the rate of breast cancer. Doubling one’s total fat consumption from 20 percent of calories to 40 percent of calories was associated with a 15 percent greater risk of breast cancer, no matter what the source (butter and margarine, vegetable oil, meat, or dairy products) or type of fat (saturated, monounsaturated, or polyunsaturated).
Although further work is needed to fully understand the link between high fat diets and breast cancer, the study findings are in line with general guidelines to adopt a diet moderate in fat for the maintenance of good health and the prevention of chronic disease.