Fruits and Vegetables are the cheapest antioxidants available. They combat the free radicals that form in the body so that the incidence of cells becoming cancerous is lower. They are also high in fiber, which is important in preventing constipation, diverticulosis and colon cancer.

Protein from plant sources alone can provide adequate amounts of essential amino acids if a variety of plant foods are consumed and energy needs are met. Complementary proteins can be eaten at different times throughout the day. The general rule is a legume with grain. Below are some examples of plant protein combinations that are used by different ethnic groups.

• Beans or lentils with rice

• Beans with flour or corn tortilla

• Pea soup with bread or crackers

• Garbanzos with corn bread

• Peanut butter with bread or crackers

• Beans and pasta

• Tofu and rice

The vegetarian diets provide plenty of the following nutrients: vitamin C, vitamin E, selenium, carotenoids, other antioxidants, phytochemicals, dietary fiber and trace minerals. But they could be deficient in the following nutrients if a varied diet is not consumed: vitamin B12, vitamin D, calcium, possibly protein, energy, and possibly zinc, and perhaps iron.

Foods of plant origin contain many bioactive compunds which are not normally considered as nutrients but which have benefits to human health. They may be grouped as follows:

• Organosulfur compounds, found commonly in Allium (onions, leeks etc.) and Brassica (cruciferous) species, such as isothiocyanates and indoles.

• Products of the isoprenoid pathway, found universally in vascular plants, and including the carotenoids and terpenes

• Products of the phenylpropanoid pathway such as cinnamic and coumeric acid, gingerols, xanthones and flavonoids.

This grouping is based on chemistry but recognizes some relationship to metabolic functions. Many of these compounds are universal in plant foods, and their digestibility, absorption, utilization and interaction with other nutritional factors in humans is largely unknown. Specific mechanisms for an observed metabolic effect may not be fully understood and much of the work is confined to in vitro or animal experiments.

Here is a list of phytochemicals found in different plant foods: