Sports drinks, sneakers and protein shakes that claim to increase energy levels and help enhance physical performance have a "striking lack of evidence" to back up their claims, a study suggests.
Researchers, publishing in the online journal BMJ Open, found that not only are these so-called sports drinks a waste of money, these products can also be hazardous to health.
Researcher Dr. Carl Heneghan, from Oxford University, and his research team found that more than half of the sports-related products claiming to have performance-enhancing qualities make no references to studies supporting those marketed claims.
The researchers warned that rather than being advantageous to health, popular brands of sport-drinks like Lucozade and Powerade are loaded with large quantities of sugar and calories, which can promote weight gain.
American and UK Scientists from Oxford University and Harvard University also say that the manufacturers mislead gym goers by convincing them that they are on the cusp of dehydration, and pointed out that it is probably more dangerous to drink too much liquid because it can lead to hypernatremia, a deadly condition where brain cells swell up.
About 84 percent of the studies mentioned by sports products had a high risk of bias, 42 percent had no randomization, 93 percent had no allocation concealment, a process which keeps researchers and participants unaware of future experiment assignments and only 27 percent of the research blinded the participants, investigators, or outcome assessors.
The study also found that out of the 431 claims made about the 104 sport-related products evaluated in the study, which included sports drinks, supplements, footwear, clothing, and devices with performance- or recovery-enhancing qualities attributed to them, only 74 of the studies were scientifically valid, only three of the studies were considered "high quality and at low risk of bias," and none of the studies included systematic review, researchers wrote.
"Half of all websites for these products provided no evidence for their claims, and of those that do, half of the evidence is not suitable for critical appraisal," they added.
Deborah Cohen, investigations editor at the BMJ said that the latest findings are examples of the "triumph of marketing over science."
"These misleading messages filter down to everyday health advice by company-sponsored scientists who advise high-profile sports bodies," she said in a statement. "For instance, fear about dehydration has become gospel and influences what we drink when we exercise. It's a triumph of marketing over science."
"There is a striking lack of evidence to support the vast majority of sports-related products that make claims related to enhanced performance or recovery, including drinks, supplements and footwear," researchers concluded. "The absence of high-quality evidence is worrying."