What is it? Holland & Barrett Vitamin C & Zinc tablets contribute to the normal function of the immune system. Supports The Immune System Suitable For Vegetarians and Vegans What Are the Benefits of This Supplement? Vitamin C is strongly linked to immunity, sometimes called ascorbic acid, it helps our immune system to function normally as well as protecting our cells from oxidative damage caused by free radicals. Zinc is an essential micronutrient strongly linked with immunity, which is why you will find it in almost every immunity supplement.