Most mushrooms contain good amounts of copper, a deficiency of which is associated with low levels of white blood cells, potentially increasing susceptibility to infection. Mushrooms are also a prebiotic and so provide food for probiotic gut bacteria, keeping the digestive tract healthy and immunity strong.
Squashes are rich in vitamin C and beta-carotene (a precursor of vitamin A). Vitamin A promotes the health of the body’s main barriers to the world—skin, eyes, lungs, and urinary and digestive tracts.
Eating fermented foods such as yogurt helps to boost “friendly” probiotic bacteria in the gut. About 70 percent of our immunity resides in the digestive system, and the microflora living in the intestines play an important part in keeping it healthy.
Omega-3 fats are increasingly thought to benefit the immune system, and oily fish has these in abundance. Low levels of vitamin D (oily fish are rich in this vitamin) have also been linked to autoimmune conditions, such as lupus and rheumatoid arthritis.
These fruits are rich in vitamin C, a vital nutrient for keeping the immune system in tip-top shape. Several immune cells need vitamin C to perform their tasks, including T-cells and phagocytes. Vitamin C also aids the absorption of iron, a nutrient needed for immunity and wound healing.