Supplementation with soy products has received negative attention in males due to soy’s structural and biological similarities to estrogens. However, soy components may actually interact with estrogen receptors to modify cardiovascular adjustments (in particular, increased blood flow) during endurance exercise. Researchers asked 25 male cyclists and triathletes to perform two 20-kilometer cycling time trials as fast as possible.
Fermented soy extract consisting of 30 grams powdered supplement in 16 fluid ounces of water was ingested before one time trial while the other was preceded by a placebo containing the same quantities of organic cocoa powder and water. Soy supplementation was associated with a faster time to completion achieved at a lower heart rate with greater power and speed, specifically during the last five kilometers of the time trial.
Those with a greater preexisting fitness level appeared to reap the largest performance benefit. Overall, one-time ingestion of a fermented soy extract supplement may improve sprint-distance cycling performance and reduce cardiac demand in recreational male cyclists and triathletes. View the abstract