There's still no magic cure for the common cold. But these immune-boosting supplements (along with plenty of sleep and a healthy diet, of course) could help arm you against colds, flu, and other nasty bugs.

Immunity Booster: Resveratrol
In a lab study, resveratrol boosted immune response. Researchers suspect it promotes the production of Th1 cytokines—immune system chemicals that activate macrophages (white blood cells that gobble up invading bacteria) and also help with wound healing. Talk with your doctor about the right dose for you.

Immunity Booster: Vitamin B12
Studies suggest that being low in B12 mutes the body's protective immune responses to bacteria and viruses. In one study, people who received supplemental B12 to correct serious deficiencies saw levels of leukocytes (white blood cells, produced in bone marrow, that snuff out bacteria and other undesirables) rise and levels of natural killer cell activity double. The recommended daily allowance is 2.4 micrograms. B12 is considered so safe that no safe upper limit has been set.

Immunity Booster: Zinc
In a new review of 15 zinc studies, researchers concluded that zinc syrup or lozenges—when taken within a day of your first cold symptoms—can make a cold shorter and milder. The same review found that taking zinc supplements for at least five months cuts risk for developing a cold, missing school with cold symptoms, and taking antibiotics for cold-related infections by 36%. Zinc plays an important role in the development and functioning of many players in your immune system. The recommended daily allowance is 8 to 11 milligrams; the safe upper limit is 40 milligrams per day.

Immunity Booster: Vitamin D
Researchers have found that vitamin D is essential for activating T cells, the immune system warriors that battle and kill bacteria and viruses. Vitamin D prompts T cells to act and kick-starts the process that transforms inactive, harmless immune cells into T cell superstars. The recommended daily allowance for D was recently increased to 600 International Units for adults up to age 70, 800 IU thereafter; the safe upper limit is 4,000 IU per day.

Immunity Booster: Selenium
In your body, the mineral selenium is incorporated into compounds called selenoproteins, which are vital for the healthy functioning of a variety of immune system defenders. If levels are low, your body may not be able to fight off infection, research shows. The recommended daily allowance is 55 micrograms; the safe upper limit is 400 micrograms per day.

It's good to know there are helpers beyond hand sanitizer. But it's still smart to avoid those coughing friends and coworkers.