Dietary supplements could be the cause of a rise in deaths from heatstroke, according to reports in the American press.
A study published last week examined an increase in the rare deaths over recent years among American football players at all levels. The increase was linked to the growing availability of supplements such as ephedra, sold for weight loss and "speeding" the metabolism, and creatine, sold supposedly to build muscle.
Both are legal supplements and doctors simply advise athletes to stop taking such supplements, because they can interfere with the body's ability to regulate temperature, at least a day before starting hot-weather training.
"We were interested in the perception that there were more deaths related to heatstroke in football in recent years," Dr. Julian Bailes, a neurosurgeon and team doctor at West Virginia University who led the study, said in a telephone interview with Reuters.
"So we studied the last three decades and we found out that in fact there has been a substantial increase - there were 11 (health-related) deaths last year, four of them from heatstroke."
The report pointed to the high-profile death of Minnesota Vikings player Korey Stringer in July 2001. Ephedra supplements were later found in his locker.
A separate annual survey by a team at the University of North Carolina at Chapel Hill published last week found three college and high school football players died of heatstroke during the 2001 season.
"In the 10 years from 1985 through 1994, only six deaths secondary to dehydration and heatstroke were recorded among football players - a rate of 0.6 per year," said Bailes, who is a consultant to the National Football League Players Association on health issues. "But there were four deaths each in 1995, 1998, 2000 and 2001."
The report attributed the explosion in the dietary supplement industry tothe 1994 federal Dietary Supplement Health and Education Act, which exempted diet supplements from Food and Drug Administration regulation.
Writing in the journal Neurosurgery, Bailes and colleagues said deaths from heatstroke were nearly eliminated from US football by 1985 because coaches and managers came to realise that players had to be kept supplied with water.
But the recent trend of taking supplements may be counteracting the healthy habit of drinking plenty of water, suggest scientists.
Bailes cited studies that show up to 70 per cent of college athletes and between 30 and 50 per cent of high school athletes take performance-enhancing or body-building supplements.
He said that creatine, ephedra and amphetamines can affect the brain's ability to regulate body temperature."It causes constriction of the peripheral blood vessels that diminish the ability to sweat," said Bailes. "Creatine works by driving water out of the vascular system into muscle. It has been associated with a high number of complaints about dehydration, gastrointestinal complaints such as diarrhoea and vomiting."
Bailes added that it is hard to track the trends because no government agency keeps statistics on the use of supplements. "Our advice is simply to discontinue dietary supplements prior to beginning training in a hot environment," he said.