The word phyto means plant in Greek. The term phytochemicals means “plant chemicals” and these include compounds such as flavonoids, beta-carotene, chlorophyll and anthocyanins that occur naturally in plants. Sometimes they are also called “phytonutrients”, especially where a health role for a phytochemical has been established. Vegetarian diets are rich in phytochemicals and antioxidants. These chemical substances obtained from plants are biologically active but not nutritive; however they protect humans against diseases. These are health-protecting compounds exclusively found in fruits, vegetables and other plants. They exhibit a potential for reducing the risk of cancer, other diseases, and have antioxidant properties. Generation of reactive oxygen species (ROS), caused due to oxidative stress, is induced by a wide range of environmental factors including ultraviolet stress, pathogen invasion, herbicide action and oxygen shortage, such as carbon monoxide levels from pollution. The formation of ROS is reduced by phytochemicals and antioxidants. Free radicals cause rancidity in fats and damage to DNA. Delaying the aging process can be achieved by increasing the phytochemicals and anti-oxidant intake, through eating fruits and vegetables, decreased meat intake and taking anti-oxidant vitamin and mineral supplements. Consumption of a vegetarian diet with reduced meat consumption also minimizes the potential for risk of multiple diseases. Eating foods containing insufficient quantities of phytochemicals and antioxidants is one of the important factors resulting in old age disease. Sufficient evidence exists for public health policy to promote plant-rich diet for health promotion.