A healthy, balanced diet is important for a healthy immune system. Nutrients that are known to be directly linked to proper immune function include zinc; selenium; iron; copper; vitamins A, C, E, B6 and folic acid. Because 70% of the immune system is present in the digestive tract, fiber (pre and probiotics) can also play a role in immunity by helping to maintain a healthy gut biome. Vitamin D is also necessary for the immune system and deficiencies may increase susceptibility to infections. Herbal remedies have also been linked to immune health, including Echinacea.