Study findings: A diet high in protein silently caused dehydration in endurance athletes, individuals whose training gave them a greater capacity to adapt to dehydration than the average person.
Speaking at the Experimental Biology 2002 meeting in New Orleans on Monday, April 22, William Forrest Martin, a graduate student in the laboratory of Dr. Nancy Rodriguez, University of Connecticut, reported an unique study comparing the hydration status of five endurance athletes as they consumed low, moderate, and high amounts of protein for four weeks at each level. Adjusted for weight, based on a 150 pound individual, the daily protein intake was 68 grams daily for the low protein diet, 123 grams for the moderate protein diet, and 246 for the high protein diet. Although these athletes were not trying to lose weight, the high protein diet they consumed was roughly 30 percent of total caloric intake, proportionally comparable to many popular high protein diets.
As the amount of protein consumed went up, the degree of hydration progressively went down. During the period in which athletes were consuming the highest amounts of protein, their blood urea nitrogen (BUN) - a clinical test for proper kidney function - reached abnormal ranges. Other tests indicated that the high protein diet caused the kidney to produce a more concentrated urine. The researchers believe the bottom line is clear for athletes and non-athletes alike: when consuming high protein diets, increase your fluid intake, whether you feel as if you need to or not. The athletes in this study reported no difference in how thirsty they felt and consequently they did not drink more liquid from the low to high protein diets. Athletes or extremely active people may also want to monitor hydration status.
In fact, say the researchers, you might want to drink more water regardless of your diet. It has been estimated that three of every four Americans are chronically dehydrated, placing themselves at increased risk for heat illness and other health problems. As little as a two to three percent decrease in body water has been found to negatively affect performance and cardiovascular function.