First Monster Energy, and now 5-Hour Energy? The energy drink is now being investigated for a possible link between its stimulant level and multiple deaths. Before you believe in caffeine as the cause, Forbes questions if there is something in the other ingredients that might be the real culprit.

5-Hour Energy Drink doesn’t indicate how much caffeine is in each bottle, but Consumer Reports and Center of Science in the Public Interest have the figure locked around 207 to  215 milligrams, respectively, per bottle. In comparison, Monster Energy is at 160 milligrams per can, and a 12-ounce serving of coffee weights in at about 230 milligrams.

Noting other ingredients like amino acids,Forbescontributor Melanie Haiken turns a critical eye toward “the health effects of these ingredients, especially when combined with caffeine and sugar as they are in energy drinks, simply aren’t known.” After all, she goes on to say, “energy drinks aren’t studied in clinical trials before coming to market because they are regulated as supplements, not as medications.”

It’s looking more and more like we should stick with coffee (or tea) for our pick-me-ups—at least for now. The caffeine level in coffee may actually be higher than energy drinks, but at least we know there are little to no other ingredients to create a potentially lethal combo.

[via Forbes]