The supplement, now widely available, has already resulted in at least two deaths, according to a Food and Drug Administration consumer advisory warning on powdered pure caffeine products sold in bulk over the Internet.

In response the Marine Corps released its own warning via Marine administrative message 047/15, signed Feb. 2.

"Pure caffeine is a potent stimulant and very small amounts could lead to accidental overdose and toxicity," according to the message. "Symptoms of caffeine overdose may include rapid or dangerously erratic heartbeat, seizures, and death. Symptoms of caffeine toxicity include vomiting, diarrhea, stupor (impaired consciousness), and disorientation."

Officials with Marine and Family Programs Division said the products should be avoided all together, citing the FDA's guidance.

While caffeine in moderate doses is not dangerous and can indeed have enhancing cognitive and physical effects, one of the primary dangers of pure caffeine powder is that is it so concentrated it is difficult and dangerous to measure with standard kitchen implements, said Catherine Ficadenti, the branch head for Semper Fit and Recreation. One of her branche's primary tasks is helping to educate Marines on healthy lifestyle choices and warn them away from potential dangers.

"If the dose is 1/16th of a teaspoon, I don't even have an instrument in my kitchen to measure that," she said. "I think pure caffeine has no place in a typical Marine's day. They can get caffeine other ways from tea, soda — there are potentially plenty of places to get their dose of caffeine and most of those foods are regulated."

One of the dangers is that supplements, because they are not medicine or food, are not scrutinized by the FDA.

"FDA regulates caffeine in Folgers, but supplements on the market are without any regulation," she said. "They have to step in after the fact if something is proven to be dangerous. It has to first demonstrate it has caused harm to people who used the product in accordance with the manufacturer's directions."

Whether any Marines or sailors have suffered negative effects related to caffeine powder consumption is unknown, according to Ilka Regino a spokeswoman for the Navy Bureau of Medicine and Surgery.

"We have confirmed with our subject matter experts at the Navy and Marine Corps Public Health Center we have not conducted studies/surveillance on adverse effects associated with Caffeine overdose... so are unable to tell if any Sailors or Marines have been admitted for this condition," she wrote.

That doesn't mean caffeine powder isn't dangerous, however, as evidenced by civilian physician reports of multiple negative reactions including death among civilians.

The potential draw for many is that caffeine powders are marketed as performance enhancing.

"These products appeal to children, teenagers, and young adults who are drawn to the perceived benefits such as the ability to study longer, improve performance, and weight loss," the MARADMIN reads.

Those are all things that would be beneficial at face value to Marines who work in a hyper-competitive organization where a premium is places on doing things better, faster and longer.

"If I see caffeine on a label and words about energy performance, I might be prompted to take it," Ficadenti said. "When I used to run I used to always have a cup of coffee first."

But the risks outweigh the benefits she repeatedly stressed.

One of the reasons caffeine powder is a particularly vexing danger is that it is a familiar word unlike some exotic supplement that might make a Marine skeptical. That, she fears, might make some more likely to try pure caffeine powders.

While her job is to steer Marines clear of harmful substances, she did say that there was nothing they could do to stop or punish Marines using the powders because caffeine is a legal supplement. It is no different from a legal standpoint than cold medicine. But if Marines engage in behavior that negatively effects them in their official duties, that can result in significant disciplinary and career problems.

Ficadenti said her branch does not try to steer Marines away from all supplements because there are many out there that can be beneficial or at least safe. Those might include vitamins or protein powders. Her philosophy is that diet is always the best source of nutrition, but by no means the only.

All that said, even the most benign supplements can be dangerous to a Marine with a preexisting medical condition or one who is currently taking other medications. She advised that any Marine thinking about taking a supplement to first consult a healthcare professional.