Immune System Defense provides powerful immune system boosters. It increases overall health, helps the body adapt to stress and fights infections. Immune System Defense combines some of the most popular immune system boosters into one formula. Vitamin C is popularly known to help the body heal from colds. Too much stress can deplete your body of Vitamin C, resulting in a weak immune system. Ester-C®, a special form of Vitamin C, is easily absorbed by the body and more easily digestible. If you are experiencing longer lasting and more frequent infections, you may be deficient in zinc. Zinc is necessary to support the immune system, and acts as an immune system booster through its stimulation of the thymus gland. This gland begins to shrink as we age and it produces fewer hormones that help fight off infections. Astragalus root is popularly known as an adaptogen. This means that it can reduce mental and physical stress. It can also boost the immune system response. Elderberry has been used for many years to help maintain and boost the immune system. There are many natural doctors who hold that it can prevent the flu and colds. Elderberry has been known to reduce the duration of a cold to one or two days, if taken at the first sign.