The U.S. Army is investigating a possible link between the death of two soldiers and popular dietary supplements containing dimethylamylamine, or DMAA. The New York Times reports that the supplements were available on U.S. military bases until recently.

Both soldiers died last year after they suffered heart attacks during fitness exercises.

The supplements, which are sold under brands including Jack3d and OxyElite Pro, contain DMAA, which is advertised to increase concentration, energy and metabolism. They are sold at stores including GNC and the Vitamin Shoppe, as well as online, the article notes.

The Army has removed all products with DMAA from military base stores, pending the completion of an Army safety review.
“We are concerned about reports of heat illness, kidney (and) liver damage, and sudden death in service members who reportedly used products containing DMAA,” Dr. Michael Kilpatrick, the Deputy Director of Force Health Protection and Readiness Programs with the Office of the Deputy Assistant Secretary of Defense for Force Health Protection and Readiness, said in an Army statement.

The statement notes DMAA is often combined with caffeine, which may accelerate metabolism, heart rate and blood pressure. These in turn may increase the body’s production of heat, especially in hot and humid conditions.

The World Anti-Doping Authority, which regulates drug use by Olympic athletes, has listed DMAA as a banned stimulant, as have several professional sports leagues.