Popular muscle-boosting supplement does not increase blood flow, study suggests

In recent years, various nutritional supplements have been developed containing arginine-alpha-ketoglutarate (AAKG), which is alleged to increase nitric oxide production thereby resulting in "vasodilation," the widening of blood vessels and increased blood flow to the muscles. The AAKG supplement-enhanced blood flow to working muscles during resistance exercise is alleged to provide increased muscle strength than just exercise alone.

The Baylor researchers studied the effects in 24 men of seven days of AAKG supplementation using the nutritional supplement on arterial blood flow in the arms after a single bout of resistance exercise. The results showed that seven days of AAKG supplementation had no significant impact on blood movement or increased brachial artery blood flow in response to a single bout of resistance exercise.

"We did see a slight increase in blood flow but those effects can only be attributed to the resistance exercise and not to the supplement," said study author Dr. Darryn Willoughby, associate professor of exercise, nutritional biochemistry and molecular physiology at Baylor. "The data appear to refute the alleged supposition and manufacturer's claims that 'vasodilating supplements' are effective at causing vasodilation, thereby resulting in increased blood flow to active skeletal muscle during resistance exercise. Furthermore, we specifically demonstrated that a single bout of resistance exercise increases vasodilation, arterial blood flow and circulating nitric oxide levels, but that the AAKG supplement provided no additive, preferential response compared to a placebo."