Introduction
Phytochemicals have been recognized as non nutritive plant chemicals that hold within them certain disease-preventing compounds. Although these phytochemicals are not yet classified as nutrients, their substances aid animals and people by creating a preventive barrier against diseases and sickness. Over 900 different phytochemicals have been identified as components of food and are today still being discovered in the different foods which are consumed on a day to day basis. It is estimated by many tests that there may exist more than 100 different phytochemicals in just one serving of a vegetable dish. (Rossi & Dresbach)
From as early as 1980, the National Cancer Institute Chemoprevention Program of the Division of Cancer Prevention and Control began to study and evaluate the different types of phytochemicals for safety, efficacy, and applicability for prevention and treatment of diseases. Researchers have for a long time being conducting tests and have come to recognize that there are phytochemicals are present not only in plants for their protection, but instead it has recently been discovered that these chemicals can also aid the human life.

Types and Presence of Phytochemicals
Allyl Sulfides
These phytochemicals are present in the allium vegetables such as garlic, onions, chives and leeks.
Lycopene
These chemicals occur normally in the Solanaceous vegetables such as tomatoes and peppers. Deposited in a number of body tissues, lycopene protects against heart disease, certain cancers, and a multitude of other disorders.
Gingerols & Flavonoids
These two phytochemicals are present in the herbs and spices like ginger, mint, rosemary, thyme etc.
Monoterpenes (limonene) & Carotenoids
Citrus fruits like oranges, grapes and grapefruits consist of these Phytochemicals.
Silymarin
This phytochemical is found in the Compositae plants (artichoke).

Role of Phytochemicals in Disease Prevention
“Phyto” means plant and ‘chemical’ refers to the substance in the plant that provides the color and flavor. These chemicals are the natural defense system of the plants as they shield the plants from disease, oxidants in the air and pollutants. It is of great fortune for humans that it also plays the role of a defense system in a human body so that the body is not vulnerable to incurable and dangerous diseases. Phythochemicals play a major role in the prevention of heart diseases, cancer and menopausal health symptoms while providing many other benefits. We benefit a lot when we ingest them and because of their ability to boost are immune systems; they increase our resistance to certain diseases.
Health benefits are best obtained through the consumption of a varied diet choosing fruits and vegetables, grains, legumes and seeds which contain the phytochemicals. Some common foods that contain high amounts of phytochemicals include garlic, onion, broccoli, cabbage, carrots, tomatoes, vegetable oil, strawberries, lemons and hot peppers. New research has revealed that eating a combination of broccoli and tomatoes which possess lycopene, offers a powerful and protective effort against cancer which cannot be possible by eating either one of the vegetable alone. It was also found that when a person eats one tomato, he/she does not only consume lycopene, but instead the person is consuming hundreds of other protective phytochemicals which helps prevent the chronic disease like prostrate cancer.