DMAA acts as a vasoconstrictor, narrowing blood vessels and causing a significant spike in blood pressure and heart rate. Experts from the FDA and WebMD highlight the following risks: DMAA in Products Marketed as Dietary Supplements - FDA

DMAA (1,3-dimethylamylamine) is an amphetamine derivative and a potent central nervous system stimulant formerly found in popular pre-workout and weight loss supplements. . Summary of Health Risks