The portion of a food’s nutrients that the body can actually digest and absorb, as distinct from the total amount the laboratory analysis reports. Availability varies enormously: the iron in meat is absorbed several times more efficiently than the iron in spinach, phytates in whole grains bind zinc and calcium, and cooking frees lycopene from tomato cell walls while destroying some vitamin C. Food scientists distinguish bioavailability, what the body captures, from the chemical content on the label, and diet planning that ignores the difference can look adequate on paper while failing in practice. Processing, food combinations, and individual gut health all shift availability, which is why dietary wisdom emphasizes varied diets and smart pairings, like vitamin C with plant iron, over nutrient tables alone.