For years, a troubling question lingered at the edge of nutritional science: if folic acid's active form releases formaldehyde in a test tube, what might it be doing inside the human body? Cornell University researchers, working alongside oncologists and cancer patients, have now followed that question from the laboratory into living organisms — and found that the body, with its layered defenses and repair systems, does not behave like a petri dish. The gap between in vitro alarm and in vivo reality, it turns out, is a protective one, offering quiet reassurance to the millions who depend on fo