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.
Were there any surprises? "Yes," says Tarnopolsky, "the fact that the females didn't increase as much as the males in lean mass." Tarnopolsky is an associate professor of medicine in neurology/rehabilitation and kinesiology at McMaster University in Hamilton, Ontario.
He says that the food supplement's effect on kidney function was also an important part of the study. "There's a lot of misinformation out there," he says. "Many people feel that somehow creatine will damage their kidneys."
Tarnopolsky says that he knows of two cases of potential renal problems, both of which could not be blamed directly on creatine. "Of course there is always a risk of [unexpected] reactions with any compound," he says. "So, yes, caution should be used. But 5 g per day seems very safe, and even larger doses by some athletes show no deleterious effects upon renal function." Urinalysis was not performed in the study. Instead, kidney function was evaluated by blood analysis and blood pressure.
Tarnopolsky believes that creatine may benefit people who suffer from muscle atrophy due to disease, in addition to beefing up athletes. In a study reported last year in the journal Neurology, he found that patients with muscular dystrophy and amyotrophic lateral sclerosis -- commonly known as Lou Gehrig's disease -- had a 10-15% improvement in their ability to perform high-intensity exercises. In fact, the Muscular Dystrophy Association's medical committee is planning new studies to evaluate whether creatine may help maintain energy and strength in aging people.
But while creatine is gaining more mainstream acceptance -- the Olympics allow athletes to use it -- the supplement still has its share of critics. "There are too many unanswered questions for us to even begin getting behind the product," said David Lightsey of the National Council Against Health Fraud, a consumer advocacy group, in a prepared statement. "We're concerned what's going to happen a year and two years from now to these kids who are taking this product, especially to the ones who are going through their major growth changes."
Also, the FDA urges caution, since long-term effects of creatine supplements are still unknown. "The FDA recommends that consumers consult their physicians before taking this or any product like this," says FDA spokesman Lawrence Bachorik. Creatine has not been evaluated by the FDA for safety, effectiveness, or purity.
Study funding was provided by the Natural Science and Engineering Research Council of Canada.
- New research on the supplement creatine shows that taking it for one week does not raise blood pressure or cause kidney problems.
- The supplement did increase fat-free mass in study subjects, and it worked much better in men than in women.
- Creatine still has its share of critics, who argue that the long-term effects of the supplement are unknown and that it could be dangerous for children who are undergoing major growth changes.