Walter C. Willett, MD, DrPH

Titles and Affiliations

Professor of Epidemiology and Nutrition
Department of Nutrition
Harvard T.H. Chan School of Public Health
Boston, Massachusetts

Research area

Understanding the effects of diet and gut microbial health on breast cancer risk.

Impact

Lifestyle choices, including diet, can play a pivotal role in breast cancer prevention. Diets rich in vegetables, fruits, whole grains, fish, and olive oil have consistently been associated with a decreased risk of breast cancer. Recent studies have suggested that the gut microbiome—the collection of millions of intestinal bacteria—plays an important role in modulating risk of several chronic diseases, including breast cancer, by altering estrogen metabolism. At the same time, it is now understood that diet plays a significant role in shaping the microbiome and its overall health. Dr. Willett is examining relationships between diet and breast cancer risk to identify ways to reduce risk and mortality from this disease.

Progress thus far

Dr. Willet and his team are conducting their research in cohorts of women whose lifestyle and dietary choices have been followed for decades using methods such as questionnaires and collection of blood and fecal (stool) samples from participants. Ongoing studies include: 1) analyzing patients with invasive breast cancers’ diets during adolescence by indices that capture a diet’s potential to affect inflammation, increase insulin in the blood, and how plant-forward it is, (planetary health diet), and whether it is associated with breast cancer risk; 2) using the same indices to examine the association between diet and breast cancer survival; 3) calibrating dietary questionnaires used across studies to standardize cohort data. The team found that diets that cause high levels of insulin in the blood were associated with overall increased mortality.

What’s next

In the coming year, Dr. Willett will continue his analyses of diets on breast cancer risk and survival. This will be the first time that insulinemic potential and a planetary diet will be assessed through dietary patterns in relation to breast cancer survival in a U.S. population. Such analyses are crucial for understanding how specific lifestyle interventions relate to health after cancer for the large and growing population of breast cancer survivors.

Biography

Dr. Walter Willett is Professor of Epidemiology and Nutrition at the Harvard T.H. Chan School of Public Health and Professor of Medicine at Harvard Medical School. Dr. Willett 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 40 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 2,000 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 four 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, The Fertility Diet, co-authored with Jorge Chavarro and Pat Skerrett, and most recently, Thinfluence, co-authored with Malissa Wood, emphasizing the powerful and surprising effect friends, family, work, and environment have on weight. 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 National Academy of Sciences and the recipient of many national and international awards for his research.