Your immune system consists of a complex collection of cells, processes, and chemicals that constantly defends your body against invading pathogens, including viruses, toxins, and bacteria. Keeping your immune system healthy year-round is key to preventing infection and disease. Making healthy lifestyle choices by consuming nutritious foods and getting enough sleep and exercise are the most important ways to bolster your immune system. In addition, research has shown that supplementing with certain vitamins, such as Vitamin D3, Vitamiin C, and Zinc can improve immune response and potentially protect against illness.