The zinc in these fajitas will beef up your immune system.

RODALE NEWS, EMMAUS, PA—With cold and flu season upon us, now’s the time to make sure your immune system is in fighting form. Along with sleep and exercise, a healthy diet is key…and the mineral zinc is a key ingredient for an immune-boosting diet. Zinc deficiency is common among American adults, and vegetarians and those who are limiting red meat need to be especially vigilant about getting enough of the recommended 15 milligrams a day. Studies show that even mild zinc deficiency can increase your risk of infection; zinc is crucial for the development of white blood cells, which seek and destroy invaders like bacteria and viruses. Zinc helps speed the healing of wounds, maintains fertility, preserves vision and normal taste and smell, and helps maintain strong bones. And it’s important for maintaining energy levels; even slightly reduced zinc levels can leave you feeling depleted. A zinc-containing enzyme in red blood cells (carbonic anhydrase) helps cells pick up carbon dioxide in the body and deposit it in the lungs for exhaling. Muscles couldn't contract and produce energy without it.

High-zinc foods include oysters, lean red meat such as sirloin steak or lean ground beef, and dark-meat turkey like thighs and drumsticks. But vegetarians can get enough zinc, too, by eating lentils, black-eyed peas, tofu, wheat germ, whole grains, leafy green vegetables, and breakfast cereals. Eggs, yogurt, and milk contain zinc, as well. Zinc absorption can be increased by having a source of vitamin C with your meals, such as a glass of orange juice, some vegetables, or fruit.

Meat-eaters should look to lean cuts of, preferably, grass-fed, organic beef, lamb, or pork. And portion size is important so you don’t consume too much saturated fat. A three-ounce serving of lean beef—about the size of a bar of bath soap or a computer mouse—is all you need to eat to get about 30 percent of the daily recommended intake of zinc. Read on for a sampling of zinc-filled dishes for carnivores and vegetarians alike that come from the