Understanding and boosting the immune system .

So, what can you do to help maintain health as your immune system naturally declines? “The strength of the immune system is tied to a healthy lifestyle, exercise, good nutrition, and sufficient rest,” Nikolich-Zugich says. Some surprising mood-­improving strategies may also make a difference. We reviewed recent research and asked leading experts to help us separate fact from fiction.

Eat Smart

Try for variety in your diet. 
Consume alcohol only in moderation.
Consider a D supplement = vitamin D
Don’t megadose on supplements. = Large doses of supplements such as vitamin A, iron, and others can actually hamper the immune system. For example, for most adults, more than 400 micrograms per day of folate, a B vitamin, may impair our natural killer cells. And though we may have some difficulty getting enough zinc in our diets—and trouble absorbing it properly as we age­—100 milligrams or more per day can weaken the immune system.

Adopt Good Habits

Get your zzz’s.
Exercise … but don’t overdo it. 
No smoking. 

Relax and Enjoy

Cultivate life’s ‘wow’ moments.
Indulge in a massage.
Nurture friendships. 
Ease stress.
Visit a park. “Nature doesn’t just have one or two active ingredients—it’s more like a multivitamin that provides us with the nutrients we need to protect us from different diseases,” says Ming Kuo, Ph.D., director of the Landscape and Human Health Laboratory at the University of Illinois at Urbana-Champaign. In fact, in a recent review in the journal Frontiers in Psychology, Kuo identified more than 20 ways in which experiencing the great outdoors can improve health. For example, being surrounded by nature reduces the body’s fight-or-flight response to stress, allowing the immune system to rest and recharge.