Your immune system is a two-layer defense: a fast innate response (barrier cells, NK cells, complement) and a slower, learned adaptive response (T- and B-cells, antibodies). Both run on micronutrients — vitamin D tunes the response so it fights pathogens without over-firing, vitamin C and zinc are consumed rapidly by activated immune cells, and selenium + copper + the antioxidant vitamins shield those cells from the oxidative burst they use to kill microbes. A shortfall in any of the load-bearing three (D, C, zinc) measurably raises both how often you get sick and how long it lasts. These 48 whole foods are ranked by how many of the key immune nutrients a typical serving delivers (≥10% DV each).