Zinc is vital for several things - reproduction, growth and natural resistance to infection. A lack of zinc has been linked to weight loss, brittle nails, ulcers and acne, PMS and hyperactivity in children. You are more likely to be deficient if you are a vegetarian or are constantly on diets. The best natural sources are lamb, liver, steak, garlic, ginger root, Brazil nuts, pumpkin seeds, oysters, eggs, sardines, oats, crab, almonds and chicken.