Professor of Epidemiology and Nutrition
Harvard School of Public Health
Professor of Medicine
Harvard Medical School
Body weight, growth velocity, and BMI at different stages of life strongly influence risk of breast cancer, and the prevalence of obesity in the US continues to rise. Developing a deep understanding of the health effects of being normal, under, or overweight at different life stages becomes increasingly critical for breast cancer prevention over a lifetime. With their 2013-2014 grant, Dr. Willett’s team will conduct initial data retrieval and setup to study weight loss during adulthood in several cohort studies from around the world. With weight measures over time from many individual studies this new database will include longitudinal weight measures for many more women.
Dr. Willett’s own work and that of others has shown the taller height and thinner body size at ages 5 and 10 are related to greater risk of breast cancer. The Growing up Today study (GUTS) has followed the height and weight trajectory of several thousand girls and young women from the ages of 9 through 18. With help from BCRF, Dr. Willett’s team has sent annual postcards to the parent nurse of the participant, asking the parent to measure and record weight and height, and they have received these measures from the majority of the cohort members. They now plan to begin the analyses of these data to categorize participants into quantiles of weight and weight change over time. The extensive GUTS data on diet, activity and other behavioral variables during adolescence will allow Dr. Willett’s team to examine these in relation to weight and height trajectories, and in turn examine weight and height trajectories in relation to risk of benign breast disease in future years.
Finally, growth promotion in many animals raised for meat production is enhanced by synthetic hormones approved by the US Food and Drug Administration. These drugs are banned in the European Union due to safety concerns. Because of their estrogenic activity, some are considered growth promoters in humans. It is prudent to conduct a pilot study to evaluate the feasibility of detecting these hormones in the plasma and urine of premenopausal women in the Nurses’ Health Study cohort. If this pilot study is successful, Dr. Willett plans to use their archived samples for approximately 30,000 women to examine the relation of these synthetic hormones to risk of breast cancer.
Weight gain and growth trajectory in adolescence and early adulthood as well as weight change during adulthood may have considerable impact on breast cancer risk. In the initial setup to study weight loss, the researchers have chosen exposure variables, potential confounding factors and anthropometric variables to examine in 11 Pooling Project cohort studies for this weight change project. The researchers are currently analyzing choices in follow-up data to add from the Nurses’ and Nurses’ II Health studies as well as the Women’s Health Study to allow for the creation of a harmonized data set in anticipation of future analyses examining the association between adult weight change/loss and breast cancer risk.
Dr. Willett’s team is collecting saliva samples for DNA and hormone levels from GUTS cohort participants to establish a bio-repository. To date, almost 1800 participants have provided DNA samples. This will allow the researchers to pursue expanded future aims relating to genetics and breast cancer risk. Further, they are updating and piloting new food items/drinks for the next questionnaire, which will contain new questions on diet and activity providing valuable information about diet and lifestyle factors that may be related to breast cancer. Updating yearly height and weight data is also in progress.
Pilot study of synthetic hormones: The researchers have received results back from the laboratory on the variability of urinary mycoestrogens and trenbolone in high meat intake samples. All samples had detectable zearalenone, 90% had detectable levels of the other mycoestrogens. They are now assaying urine samples from those with low red meat intake to assess micoestrogen detectability. Once this has been completed, they plan to move on to the next pilot studies, assessing stability due to delays in processing and within-person variability of these hormones.
Dr. Walter Willett is Professor of Epidemiology and Nutrition and Chairman of the Department of Nutrition at Harvard School of Public Health and Professor of Medicine at Harvard Medical School. Dr. Willett, an American, was born in Hart, Michigan and grew up in Madison, Wisconsin, studied food science at Michigan State University, and graduated from the University of Michigan Medical School before obtaining a Doctorate in Public Health from Harvard School of Public Health. Dr. Willett has focused much of his work over the last 30 years on the development of methods, using both questionnaire and biochemical approaches, to study the effects of diet on the occurrence of major diseases. He has applied these methods starting in 1980 in the Nurses' Health Studies I and II and the Health Professionals Follow-up Study. Together, these cohorts that include nearly 300,000 men and women with repeated dietary assessments are providing the most detailed information on the long-term health consequences of food choices.
Dr. Willett has published over 1,500 articles, primarily on lifestyle risk factors for heart disease and cancer, and has written the textbook, Nutritional Epidemiology, published by Oxford University Press. He also has three books book for the general public, Eat, Drink and Be Healthy: The Harvard Medical School Guide to Healthy Eating, which has appeared on most major bestseller lists, Eat, Drink, and Weigh Less, co-authored with Mollie Katzen, and most recently, The Fertility Diet, co-authored with Jorge Chavarro and Pat Skerrett. Dr. Willett is the most cited nutritionist internationally and is among the five most cited persons in all fields of clinical science. He is a member of the Institute of Medicine of the National Academy of Sciences and the recipient of many national and international awards for his research.