Ecdysterone is a naturally occurring steroid hormone that can be found in spinach, among other plants. Since the 1980s, it has been used in supplements for muscle growth. For years, the effect of the supplements wasn't much more than anecdotal, but recent studies conducted in rats suggest it does indeed boost muscle growth – and everyone is making the same joke: Popeye was right. Well, sort of.
In a study published in the Archives of Toxicology, researchers tested the effects of ecdysteroids on humans. The study involved 46 young men (six of whom later dropped out) on the same strength training program but separated into groups that either received ecdysterone-containing supplements, a placebo, or neither. They all had at least one year of barbell training and could perform three basic strength exercises: back squats, deadlifts, and bench presses. The program ran for 10 weeks.
"Our hypothesis was that we would see an increase in performance, but we didn't expect it to be that big," Maria Parr, from Berlin University's Institute of Pharmacy, said in an interview with broadcasters ARD and ARTE, as reported by DW.
The group who took the supplement received either 200 milligrams or 800 milligrams per day. Participants in these groups increased their muscle mass by 1.5 and 2 kilograms (3.3 and 4.4 pounds) respectively, and both improved their performance of one-repetition bench presses.
"We recommended to WADA [the World Anti-Doping Agency] in our report that the substance be added to the doping list. We think that if it increases performance, then that unfair advantage should be eliminated," Parr said.
The team made sure the supplements had no other anabolic substance and that the effect was exclusively due to the ecdysterone. They also report that the supplement showed no signs of increased toxicity in the liver or kidney. Given the positive effects with little harm, there is plenty of interest in using this substance to boost performance.
So can you get more muscles just by eating lots of spinach? Not really, though keep eating your vegetables. The daily dose of ecdysterone in the Western diet is roughly 1 milligram, while bodybuilders take doses up to 1,000 times higher than that. It's also important to note that the sample size in this study was small and focused exclusively on men.