William J. Bulsiewicz

William John Bulsiewicz, better known as Dr. B., is an American triple board-certified gastroenterologist, author, entrepreneur, and advocate for the exploration of the relationship between the gut microbiome, dietary fiber, and plant-based nutrition. He is also an Adjunct Assistant Professor of Medicine at the Emory University School of Medicine.

Early life and education Bulsiewicz was raised in "a Jesuit-educated family." He studied chemistry at Vanderbilt University and graduated in 2002.

Although originally planning to study pediatrics, Bulsiewicz decided in 2005 to switch fields, and graduated from Georgetown University School of Medicine in 2006 with a specialization in gastroenterology.

Career From 2006 to 2009, Bulsiewicz completed his internship and residency at McGaw Medical Center of Northwestern University. Next, he served as chief medical resident in internal medicine from 2009-2010, and from 2010 to 2014 he was a Gastroenterology Fellow at UNC Medical Center

Bulsiewicz is board-certified in gastroenterology and internal medicine,

38TERA In 2024, Bulsiewicz founded 38TERA, a gut health supplement company focused on microbiome science. The company's flagship product, DMN (Daily Microbiome Nutrition), is a prebiotic supplement combining three classes of prebiotics derived from seven plants, and is certified Low FODMAP. Simon Hill, host of The Proof podcast, serves as on its Scientific Advisory Board.

Research Bulsiewicz's research and advocacy centers on the relationship between dietary fiber, the gut microbiome, and plant-based nutrition. He references Dan Buettner's work on the Blue Zones, communities around the world who consume predominantly fiber-rich plant-based diets. Bulsiewicz argues that "if you look at the healthiest populations on the planet in modern times, they're in the five blue zones, and all five blue zones are 90 percent plant based. So, they are not necessarily vegan, but they are plant-predominant in a way where the meat is not the centerpiece. The plant is the centerpiece. The meat is the side show." He also advocates for the consumption of plant-based fermented foods for better health.

Publications

In addition to academic scholarship, he is the author of three books: Fiber Fueled (2020), The Fiber Fueled Cookbook Inspiring Plant-Based Recipes to Turbocharge Your Health (2022), and Plant Powered Plus: Activate the Power of Your Gut to Tame Inflammation and Reclaim Your Health (2026).

Books Plant Powered Plus: Activate the Power of Your Gut to Tame Inflammation and Reclaim Your Health. Avery, 2026. . The Fiber Fueled Cookbook: Inspiring Plant-Based Recipes to Turbocharge Your Health. Avery, 2022. . Fiber Fueled: The Plant-Based Gut Health Program for Losing Weight, Restoring Your Health, and Optimizing Your Microbiome. Avery, 2020. .

Introductions

Articles

Personal life Bulsiewicz grew up eating the Standard American Diet, which led to poor health during his medical studies (as nutrition was not part of his medical training). and live with their children in Charleston, South Carolina.