Dietary supplements can be important and potentially life-saving products for individuals who cannot get enough nutrients through foods—for instance, vegans, whose only source of vitamin B12 is fortified foods, may not get enough through their diet alone. But because supplements are not as tightly regulated as drugs, and because in some cases scientists do not fully understand their potential effects, supplements do not come without risks. “The great majority of the time people are taking supplements and it’s just a waste of money,” Cohen says. “And a small percentage of the time, they’re taking something that’s actually dangerous.”