Support for the immune system Doppelherzs Defense Active dietary supplement supports the normal function of the immune system and cell protection. In addition to zinc and selenium, the effervescent tablets contain vitamins C, B12 and D3. Zinc, selenium and vitamin C make an important contribution to the immune system and protect cells from oxidative stress. Selenium also contributes to normal thyroid function. In sufficient quantities, vitamin D can support the bodys defenses and is generally known for its benefits to bone health. Vitamin B12 is considered a true all-rounder. It supports the nerves, energy metabolism, and can reduce tiredness and fatigue.