Plant-based sports supplements sometimes make estradiol levels soar

Athletes that make use of supplements containing plant-based extracts often have frighteningly high estradiol levels. Researchers at the University of Rome ‘Foro Italico’ found that male athletes who take herbal supplements sometimes have more estradiol in their bodies than doctors deem good for women.

According to some studies, almost ninety percent of athletes use supplements, write the Italians in the Journal of the International Society of Sports Nutrition. Among the hottest supplements are those that manufacturers claim have a hormonal effect, such as plant-based hormones and products such as Tribulus terrestris.

But are these products safe when taken on a long-term basis? This is the question the Italians set out to answer. They questioned 420 bodybuilders, 250 fitness fanatics and 70 cyclists about their supplements’ use. All athletes trained 3-6 times a week, 1-2 hours a day.

The Italians found 23 athletes who took hormonal plant-based extracts and who were also prepared to undergo a blood test. The researchers found a dramatically raised estradiol level in these athletes [Figure below].

The lowest horizontal line = upper limit in men. Highest horizontal line = upper limit in women. Every figure on the horizontal axis represents a user. Circle = female user.

Among the men, athletes 2,3 and 5 have a ludicrously high estradiol level. All three had been taking a supplement already for six months containing caffeine, Citrus aurantium, guggul, cacao, naringenin and bioperine, the researchers write. It looks like a stacker; none of the other users has come up with this idea.

The Italians measured the athletes’ progesterone level, and the figure below represents the results. The horizontal line indicates that the amount of progesterone that is considered acceptable.

Users 4 and 9 [not the users 4 and 9 in the figure with the estradiol levels] are noticeable. Both had been taking the supplement named above containing caffeine, Citrus aurantium, ginger, guggul, cacao, naringenin and bioperine. It would seem that this product contains substances that have a strong disruptive effect on the hormones.

Actually, it’s not the only stacker that disrupts the hormone balance in athletes. The researchers discovered hormonal defects in 65 percent of the athletes using plant-based extracts. In a control group of athletes that were given no supplements at all, these abnormalities were conspicuous by their absence. So the Italians reach the sweeping conclusion that all plant-based supplements are suspicious. [Figure below].

If you read the research publication as a whole, however, you might wonder whether the conclusion is justified. The supplements users with a high estradiol level also used an extremely high amount of soya proteins: at least 2 g per kg/day. “Hyperestrogenism was observed in athletes who consumed high dosage of soy protein, the main food source of phytoestrogens”, the Italians write.

Perhaps it’s the interaction between herbal supplements and a high soya intake that disrupts the hormone balance?