Phytonutrients Potentially Protective Compounds in Plant Foods

7 PHYTONUTRIENTS POTENTIALLY PROTECTIVE COMPOUNDS IN PLANT FOODS 

There is overwhelming epidemiological evidence that diets rich in fruit and vegetables are associated with a lower incidence of cancer, cardiovascular, and other degenerative diseases. To some extent, this may he because such diets provide less fat, and especially saturated fat, than diets that are richer in meat. The relatively high content of vitamins C and E and carotenoids in plant foods may also be important. In addition, fruits and vegetables contain a wide variety of compounds that have (potential) protective actions. These compounds are not strictly nutrients, in that they are not dietary essentials and have no physiological function. 

Many fruits contain salicylates, which inhihit the synthesis of thromboxane A2, and have an anticoagulant action, in amounts that provide the same intake as the low dose of aspirin used as prophylaxis against thrombosis. 

Plant sterols inhibit the intestinal absorption of cholesterol and so have a useful hypocholesterolemic action. They also inhibit endogenous synthesis of cholesterol, by inhibiting and repressing the regulatory enzyme of cholesterol synthesis, hydroxymethylglutaryl (HMG)-CoA reductase. Other compounds synthesized from mevalonate also inhibit and repress HMG-CoA reductase and have a hypocholesterolemic action, including squalene (found in relatively large amounts in olive oil), ubiquinone (Section 14.6), and the tocotrienols (Section 4.1). 

A number of the terpenes in aromatic oils of citms peel, herbs, and spices inhibit the isoprenylation of the P21-ras oncogene product Isoprenylation is essential for the biological action of the ras protein, which is associated with pancreatic cancer. 

The allyl sulfur compounds have two actions that may protect against the development of cancer 

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