1. Vitamin C In addition to its role in various metabolic and physiological functions, your body uses vitamin C to protect your immune system, and researchers have studied the efficacy of vitamin C as a therapeutic treatment in the prevention of cancer, diabetes, atherosclerosis, the common cold, stroke and heart disease. Vitamin C improves neutrophil chemotaxis, a process that betters the ability of neutrophils (a type of white blood cell) to move toward sites of inflammation or infection and increases the body's ability to fight disease. Finally, vitamin C also protects against reactive oxidant species, reducing the risk and severity of a variety of illnesses. 2. Korean Ginseng Korean ginseng also known as Panax ginseng, possesses strong antioxidant and immune-stimulating properties. Korean ginseng helps regulate immune cell function, including macrophages, T cells, B cells and natural killer cells, and improves inflammation through its high content of a variety of pharmacological compounds, like ginsenosides and acidic polysaccharides. In most cases, it is ginseng root extract that is used to maintain immune homeostasis, although the other parts of the plant can be used as well. Ginseng root is often consumed raw or as a juice, tea or powder, and some studies have suggested that daily consumption of Korean ginseng may decrease oxidative damage and improve immunomodulatory activity while presenting no adverse side effects. 3. Astaxanthin Astaxanthin is a carotenoid antioxidant that possesses potent immuno-modulation properties, including the ability to increase interleukin production, a type of cytokine expressed by white blood cells. Additional studies have found that dietary intake of astaxanthin may heighten immune response while also reducing DNA damage and inflammation, and astaxanthin may play a protective role in immune function by limiting free radical damage to immune cells. 4. Shiitake Mushrooms Medicinal mushrooms and their benefits have been studied extensively for many years, however, recent research has revealed that this traditional oriental therapy may also modulate the immune response by activating lymphocytes and dendritic cells, thereby up-regulating the production of cytokines.