As we age, our immune response capability becomes reduced, which in turn contributes to more infections.

Respiratory infections, influenza, and particularly pneumonia are a leading cause of death in people over 65 worldwide. No one knows for sure why this happens, but some scientists observe that this increased risk correlates with a decrease in T cells, possibly from the thymus atrophying with age and producing fewer T cells to fight off infection.

Others are interested in whether the bone marrow becomes less efficient at producing the stem cells that give rise to the cells of the immune system.

There is a strong connection between nutrition and immunity. A form of malnutrition that is surprisingly common even in affluent countries is known as "micronutrient malnutrition." Micronutrient malnutrition, in which a person is deficient in some essential vitamins and trace minerals that are obtained from or supplemented by diet. This is also true of elderly. Older people tend to eat less and often have less variety in their diets.

So what can you do? If you suspect your diet is not providing you with all your micronutrient needs — maybe, for instance, you don't like vegetables — taking a daily multivitamin and mineral supplements may bring health benefits beneficial on the immune system.

To support your immune system, you can eat immunity supporting foods like citrus fruits, garlic, broccoli, and spinach. If your immune system is already weak, it can also be helpful to supplement with key vitamins and minerals that may have become depleted like Vitamin C, Vitamin B, Vitamin D, and Zinc.