Immunity is growing in consumer attention. An increasing number of products are hitting market shelves that claim to reduce the risk of colds and infections, enhance the body’s immune defenses, or support a healthy immune system. General Mills Inc., Minneapolis, Minn. (phone 800-446-1898, www.bettycrocker.com), recently introduced Green Giant Immunity Boost Frozen Vegetables, which are naturally rich in antioxidant vitamins A and C to help support a healthy immune system. Kraft Foods, Northfield…