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Frank Hu

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

How Sweet is Too Sweet? Health Effects of Sugars and Artificial Sweetners

What does the word “health” mean to you–and what roles does food play in our health? We know that food can heal and food can hurt. An absence of certain foods can cause harm and disease, but too much of certain foods can have the same effect. According to the Pew Research Center, about 40% of people report restricting their consumption of sugar. Is the case against sugar really that simple? Where do we start as we stand in the grocery store aisle and make the choice to put something into the cart or leave it on the shelf?

Dietary guidelines, such as those developed federally by the Departments of Agriculture and of Health and Human Services, and by nonprofit organizations such as the American Heart Association and the American Diabetes Association, help us understand how to choose foods to aid in the prevention of nutrient deficiencies and chronic diseases such as cardiovascular disease and Type II diabetes. But researchers are discovering that there is much more to the relationship between nutrition and health. It is, for instance, a much more individualized matter than those dietary guidelines might suggest. 

Frank Hu is helping to uncover the vast differences in the ways in which individual bodies metabolize particular nutrients. Thanks to his research, we better understand how certain physiological variables such as lipid profile and physical activity combine with the gut microbial environment to shape how a body responds to sugar, and, further, how these variables can explain why different bodies respond so differently. Hu’s research is contributing to the development of new strategies for creating personalized nutrition recommendations that can improve our health by taking into account these additional factors. 

Sugar is everywhere and we humans are hardwired to desire it–but our bodies don’t all respond to it in the same way. Furthermore, our bodies respond differently to the forms in which we consume that sugar. A solid body of research suggests that individuals who consume sugar sweetened beverages (SSBs) are more likely to develop obesity and Type II diabetes than those who do not. Frank Hu’s research shows that our bodies’ mechanisms for telling us when to stop are at a disadvantage when we consume calories in liquid form. When carbohydrates like sugar are consumed in a liquid form, research indicates that people fail to reduce their total calorie intake in future meals which is referred to as incomplete compensation. Fructose in particular is thought to decrease insulin and leptin release when consumed which may lead to a decrease in the stop signals that are sent to the brain.

Frank Hu takes inspiration from the view that “food is love, food is joy and food is culture.” It seems, however, that at times, love, joy and cultural norms can also be at odds with health. What humans love to eat may also harm. The line between pleasure and pain can become fuzzy. 

An elected member of the National Academy of Medicine, Frank Hu is the chair of the Department of Nutrition and Professor of Nutrition and Epidemiology at the Harvard T.H. Chan School of Public Health. He received his MD from Tongji Medical College, Huazhong University of Science & Technology, in Wuhan, China, and his PhD in epidemiology from the University of Illinois at Chicago. 

His talk: We rely on sugar for flavor and energy, but too much affects our health negatively on multiple fronts. In this talk, we'll unpack how added sugars—especially those found in sodas, sweetened beverages, and processed foods—affect our bodies and hearts, and explore just how much might be "too much." A growing body of evidence shows that high intake of added sugars is linked to serious health problems, including obesity, type 2 diabetes, cardiovascular disease, fatty liver, and hypertension. These effects aren’t just about extra calories—sugar, particularly in liquid form, can directly promote fat storage in the liver, raise blood pressure and blood fats, and worsen insulin resistance. More recently, research has revealed new pathways through which sugar may harm health. A large study of Latino adults found that people who consumed more sugary drinks had changes in their gut bacteria and blood metabolites that predicted a higher risk of type 2 diabetes over time. These findings suggest that added sugars can disrupt metabolism in ways that go beyond what we’ve traditionally measured. Artificial sweeteners are often used as substitutes, but they are not a free pass. Emerging studies suggest that some non-nutritive sweeteners may also disrupt the gut microbiome and negatively affect metabolic responses in certain individuals.