In recent years, though, plenty of legit studies have confirmed that our diets really can affect our ability to fight off invaders—down to the fine-scale functioning of individual immune cells. Those studies belong to a new subfield of immunology sometimes referred to as immunometabolism. Researchers are still a long way off from being able to confidently recommend specific foods or dietary supplements for colds, flus, STIs, and other infectious illnesses. But someday, knowledge of how nutrients fuel the fight against disease could influence the way that infections are treated in hospitals, in clinics, and maybe at home—not just with antimicrobials and steroids but with dietary supplements, metabolic drugs, or whole foods.