Getty: Michael Piazza

We’re debunking a classic dietary fable.

Zee Krstic
November 13, 2017

As a child, I often remember scarfing down salty snacks and conveniently ready-to-eat foods when my parents were too busy to cook dinner.

Given that they were both self-employed and worked late, they often ordered takeout. While our nutritional habits weren’t great, my father still felt the need to pass along his dietary knowledge.

We had one rule, however, that I found hard to follow. If I would take more than a few sips of water, he’d bark at me to put the glass down and wait until I had finished eating.

He told us that we’d get “fat” from drinking and eating at the same time. I found it hard to believe even then, but my sister still follows this practice.

It turns out my father wasn’t alone in this belief. Some members of the health industry even today advocate for avoiding water during meals. But what is the reasoning, and is there any truth to the claim, or is it just an old superstition?

Related: Water Doesn't Necessarily Reduce the Urge to Overeat

Dr. Octavia Pickett-Blakely, MD, MHS is the director of gastrointestinal nutrition at the Hospital of the University of Pennsylvania. She says she’s never come across studies or data to suggest that a few glasses of water at mealtime can negatively impact how your body processes food.

Pickett-Blakely explains that the digestion process occurs in two different ways: Solid foods are broken up and digested, whereas liquids are absorbed. There are also chemicals like bile and hydrochloric acids (stomach acid) that work to ensure smooth digestion.

Your stomach continually creates acid—especially when you begin to eat, and a glass or two of water won’t make a difference. “The amount of water needed to dilute these gastric acids would be astounding for an average person to consume during a meal,” Pickett-Blakely says. “Physiologically, I could understand why this could be of concern. But you’d need a whole lot of water to even begin to worry about negatively affecting digestion.”

Actually Pickett-Blakely explains, water aids digestion. “Liquid is so much easier for the body to digest than, say, a big piece of steak,” she says. The role that liquids play in turning food into smaller particles is substantial, with components like saliva and enzymes from pancreatic juices. “Water helps dilute larger particles of food.”

There are a few exceptions: People who have undergone weight loss surgery such as a gastric bypass or a gastric sleeve may find that drinking a lot of water can impact their sensations of fullness. And there are some cases—such as swallowing disorders—where it might be good for a person to keep the activities separate. “Whenever I advise someone to avoid drinking and eating at the same time, it’s in response to something they are specifically dealing with,” says Pickett-Blakely.