Research has shown that vitamin D deficiency makes it harder for the body’s immune system to fend off infections of all kinds, including ebola, one of the deadliest infections on the planet. Unfortunately, vitamin D is not available in a wide variety of foods, and the primary source for human beings comes from exposure to sunlight. However, in an effort to increase the strength of your immune system, adding vitamin D-rich foods is a wise choice, so cheese, egg yolks, tuna, mackerel, orange juice and cereal grains should be added to your diet, if they’re available.