Eat your broccoli! Might be the best advice Mom gave you.
Green veggies are the source of a chemical signal that is important to a fully functioning immune system. Broccoli to spinach, cruciferous vegetables are good for us in a number of ways, but it has been found that they may also help us at a cellular level. Immune cells in the gut and skin are known as intra-epithelial lymphocytes (IELs) and eating your vegetables can help these protective cells to function properly.
