Despite the fact that your world teams with infectious microorganisms, most of the time, you’re reasonable healthy, right? Thank your immune system, which defends you from disease-causing microbes. Now, step beyond gratitude to optimize the function of that system.

1. Get enough sleep and manage stress.Sleep deprivation and stress overload increase the hormone cortisol, prolonged elevation of which suppresses immune function.
   
   
2. Avoid tobacco smoke. It undermines basic immune defenses and raises the risk of bronchitis and pneumonia in everyone, and middle ear infections in kids.
   
3. Drink less alcohol. Excessive consumption impairs the immune systemand increases vulnerability to lung infections.
4. Eat plenty of vegetables, fruits, nuts, and seeds, which will provide your body with the nutrients your immune system needs. A study in older adults showed that boosting fruit and vegetable intake improved antibody response to thePneumovax vaccine, which protects against Streptococcus.
5. Consider probiotics. Studies indicate supplements reduce the incidence of respiratory and gastrointestinal infections.  Fermented milk products have also been shown to reduce respiratory infections in adults and kids.
6. Catch some rays. Sunlight triggers the skin’s production of vitamin D. In the summer, a 10-15 minute exposure (minus sunscreen) is enough. However, above 42 degrees latitude (Boston) from November through February, sunlight is too feeble and few foods contain this vitamin. Low vitamin D levels correlate with a greater risk of respiratory infection. A 2010 studyin kids showed that 1200 IU a day of supplemental vitamin D reduced the risk of influenza A. However, a 2012 studythat involved supplementing adults with colon cancer with 1000 IU a day failed to demonstrate protection against upper respiratory infections.
7. Go for the garlic. Garlic is a broad-spectrum antimicrobial agent and immune booster. Because heat deactivates a key active ingredient, add it to foods just before serving.
8. Eat medicinal mushrooms, such as shiitake and maitake (sometimes sold as “hen of the woods”). A recent studyshowed that a concentrated extract of shiitake enhanced immune function in women with breast cancer.
9. Try immune-supportive herbs. If you get recurrent infections, consider taking immune-supportive herbs such as eleuthero (Eleutherococcus senticocus), Asian ginseng (Panax ginseng), American ginseng (Panax quinquefolius), or astragalus (A. membranaceus).
10. Make an echinacea tincture. This is good to have on hand when respiratory viruses overwhelm your defenses.