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March 9, 2000 (Atlanta) -- Canadian researchers say that the popular -- and controversial -- muscle-building food supplement creatine does not raise blood pressure or cause kidney problems over the short term. But they also discovered that when bulk is the goal, it works better for men than for women.

The study, reported in the February issue of Medicine and Science in Sports and Exercise, set out to measure the effect of creatine on body mass and to measure side effects in both men and women. Author Mark A. Tarnopolsky, MD, tells WebMD that while most other studies have focused on strength, endurance, and body mass issues, this was the first study on creatine to look at blood pressure and to evaluate gender differences in lean mass.

Sold over the counter in health food stores as a powder, in capsules, and in other forms, it's thought by many that creatine supplements may cause dehydration, heat-related illnesses, muscle cramps, minor gastrointestinal distress, nausea, reduced blood volume, and electrolyte imbalances. Other than weight gain, negative side effects have not been well documented by researchers.

Before the study began, researchers compiled detailed records of the participants' diet and exercise over the previous four days. They then measured the body composition of 15 men and 15 women, with an average age of 22, for body mass and fat using whole body scans called DEXA scans. Next, their blood pressure was measured and a blood sample was taken. Each subject then performed six, nine-second-long handgrip exercises for one minute to measure forearm strength.

The creatine was administered in 5 g dosages four times a day for five days to seven men and eight women; the balance of the subjects were given a placebo. The creatine was dissolved in juice, milk, or warm tea and taken after meals. On the sixth day, the creatine and placebos were not given, and all the subjects again underwent body scans, blood pressure tests, and forearm strength tests and had blood samples drawn to measure for the presence of creatine.

According to Tarnopolsky, creatine had no effect on blood pressure, kidney function, or handgrip strength. It did, however, significantly increase the fat-free mass and total body mass with no changes in body fat for all subjects -- with much greater changes found in the men than the women.

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