Why Higher Consumption of Protein Requires More Water

High protein, low carbohydrate diets are popular for weight loss. Bodybuilders and others who want a lean, muscular physique often use a high protein, low carbohydrate diet as well.

Does this put them at risk of dehydration? In 2002, researchers put that question to the test by designing a small study to see how a high protein diet affected trained endurance athletes.

"We found that certain hydration indices tended to be influenced as the amount of protein in their diets increased," said Nancy Rodriguez, an associate professor in nutritional sciences who oversaw the study, in a press release.

High Protein Diet Study

The study was conducted at the University of Connecticut by graduate student William Martin. He presented his research to the Experimental Biology 2002 meeting. The test subjects were five student athletes from the university who were well-trained runners.

These endurance athletes were put on a series of diets that varied in the amount of protein. Their diet was closely monitored to ensure they were adhering to the study protocol.

For four weeks, each first had a low protein diet (e.g. a 150-pound person would have 68 grams of protein daily). For another period of four weeks, they had a moderate protein diet (e.g. 123 grams daily).

In the last four weeks, they had a high protein diet (e.g. 246 grams daily). This last diet matched what many popular high protein diet programs recommend, with 30% of the calories coming from protein. These regimens span the range of what is recommended.

That matches the low protein diet given to the test subjects. The moderate and high protein diets given had twice and four times the RDA respectively.

Protein, Hydration, and Thirst

The study subjects were tested for their blood urea nitrogen (BUN), urine concentration, and other lab values every two weeks during the study. The BUN test is one performed routinely as an indicator of kidney function. It measures the breakdown products of protein that are cleared by the kidneys.

Their values returned to normal when they went back to their usual diet. They didn't feel thirstier when on the high protein diet, and so they might not have been drinking enough water to meet the needs of their kidneys to dispose of the waste products of digesting protein.

Why Drink More Water

"Based on our findings, we believe that it is important for athletes and non-athletes alike to increase fluid intake when consuming a high protein diet, whether they feel thirsty or not because our study subjects said they did not feel a difference in thirst from one diet to the next," said Rodriguez in a press release.

As little as a 2% to 3% decrease in body water has been found to negatively affect athletic performance and cardiovascular function. Whether you are exercising or not, it is important to make sure you are drinking enough to prevent dehydration.