The Nuance

This Is Your Gut on Sugar

Researchers are finally uncovering the exact ways that sugar disrupts the GI tract

Markham Heid
Published in
4 min readAug 18, 2021
Photo: Sharon McCutcheon / Unsplash

In 1776, at the start of the Revolutionary War, the average person consumed about four pounds of sugar each year. Today, per capita sugar intake in the U.S. exceeds 120 pounds.

Roughly 75% of all foods and beverages in this country contain added sugar. According to the American Heart Association, the average adult swallows the equivalent of six bowling balls of the stuff each year. Meanwhile, the average child downs enough added sugar to fill a bathtub.

Researchers have long suspected that sugar — in particular the added sugar that doesn’t occur naturally in whole fruits or vegetables — is a major contributor to this country’s exceedingly high rates of obesity, type 2 diabetes, and other metabolic conditions.

More recently, they’ve speculated that sugar may also contribute to the development of inflammatory bowel disease, gut-related autoimmune disorders, and food allergies or sensitivities — all of which are on the rise. But experts have struggled to determine just how sugar causes or contributes to these health problems.

That’s changing. Recent work has revealed some of the ways that sugar disrupts, imbalances, and harms the gut.

From the microbiome to the lining of the small intestine, sugar seems to imperil the healthy workings of the human gastrointestinal tract in multiple ways.

Robert Lustig, MD, is an endocrinologist and professor emeritus of pediatrics at the University of California, San Francisco. He’s also the author of Metabolical, a book that examines the ways processed foods and sugar make people sick.

“There are at least three processes that are going on that sugar seems to have a role in,” he says.

The first has to do with the way the gut and liver handle the sugar you eat. “Up to a point, the intestine has the ability to turn fructose into downstream byproducts that you don’t absorb,” he explains. In other words, if your sugar intake is low, your gut will pass most of that sweet stuff along so that it ends up in your feces. The little bit of sugar you do absorb will end up in your…



Markham Heid

I’m a long-time contributor at TIME and other media orgs. I write mostly about health. I grew up in Michigan, but these days I live in southwest Germany.