Vitamins C and D, Zinc, and Selenium contribute to the normal functioning of the immune system.

In addition, Vitamin C:
Contributes to the normal formation of collagen (a protein constituent of tissues)
Contributes to the normal function of bones, teeth, cartilage, gums, skin, and blood vessels
May contribute to the reduction of tiredness and fatigue

Vitamin D:
Contributes to normal levels of calcium in the blood
Contributes to the maintenance of normal bones
Contributes to the normal functioning of muscles
Contributes to the maintenance of normal teeth

Zinc:
Contributes to the maintenance of healthy skin (the skin is the body's first line of defense)
Contributes to the normal function of cognitive function
Contributes to the maintenance of healthy hair and nails
Contributes to normal muscle function

And Selenium:
Contributes to the maintenance of normal hair
Contributes to the maintenance of normal nails
Contributes to the normal functioning of the thyroid