Evidence suggests that insulin has "become a significant threat to the level playing field in sport," says Dr. Peter Sonksen, a professor of endocrinology at St. Thomas Hospital in London.
Besides giving some athletes an advantage, insulin could cause a variety of health problems in non-diabetics, ranging from blood sugar complications to death.
Sonksen analyzed existing research about the use of insulin in sport and summarized his findings in the July issue of the Journal of Endocrinology.
Sonksen says the first reports of possible use of insulin as a "doping agent" to improve the performance of competitive athletes came at the 1998 Winter Olympic Games in Nagano, Japan, when a Russian medical officer asked officials if non-diabetics could legally use insulin.
While the Olympics promptly banned insulin for non-diabetics, its use has spread among athletes in numerous sports, according to reports that Sonksen reviewed. While its use among athletes is fairly new, bodybuilders may have used insulin for several years, Sonksen writes.
Insulin helps regulate blood sugar, also known as glucose. Normally, the body detects too much sugar in the blood, such as right after a meal, and the pancreas secretes insulin to drive the glucose out of blood and into cells.
In diabetics, however, the body loses its ability to finely tune blood sugar levels and insulin production goes out of control. The amount of sugar in the blood can rise or fall to dangerous levels; insulin injections can help in many cases.
Just as insulin helps diabetics, it may strengthen the bodies of athletes, says Dr. Doug McKeag, director of the Indiana University Center for Sports Medicine. "Basically, you're opening up the cells to use glucose more, to promote the transmission of glucose. You're augmenting the metabolism [process] that ends in the creation of energy."
Sonksen says insulin-pumping devices could both boost stamina and help the body recover more quickly after exercise. Bodybuilders appear to think insulin could help them increase the bulk of their muscles, he says.
No one seems to know how many athletes and bodybuilders are taking insulin, and the substance is hard to detect. "When injected into a vein, it disappears very quickly. It has a so-called half life of four minutes," Sonksen says.
Taken other ways, however, insulin stays in the body much longer.
Healthy people who take insulin could bring on diabetes by overloading the body so that it becomes less sensitive to the effects of the hormone, McKeag says. With all the insulin coming in from outside, cells in the body may even stop creating it. He says the cells have been "taken out of the loop" and may not know how to get back into it.
Taking insulin while healthy "would be a very ridiculous thing to do for a very doubtful benefit," McKeag says. "It's amazing what people rationalize. This doesn't really surprise me, but it is amazing."
To make things worse for healthy insulin users, figuring out how much of the drug is needed is not easy. "Administering it safely is very difficult, as any insulin-treated diabetic will tell you," Sonksen says.
What To Do
Learn about how performance-enhancing drugs work by visiting HowStuffworks.com.