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The health benefits of phytochemicals have not been conclusively proven. Scientific research in the area is ongoing. Potential health benefits are difficult to substantiate because it is unclear whether desired effects are the result of a single phytochemical, group of phytochemicals, or phytochemicals working with other nutrients or non-nutrient substances present in food.  

Despite a lack of conclusive scientific evidence, different phytochemicals have been associated with helping to prevent or treat diseases such as cancer, cardiovascular disease, diabetes and hypertension. Phytochemicals appear to have various beneficial effects in the human body, including:

• Antioxidant activity. Certain phytochemicals may stop the cellular damage of free radicals, the toxic chemical compound produced when oxygen is metabolized by the body. This slows the wear of body cells and may lower the risk of heart disease and inhibit growth of cancer cells. Many different phytochemicals act as antioxidants, including carotenoids, flavonoids and phenolic acids (e.g., ellagic acid, tannins). Recent research has linked consumption of the phytochemicals in some fruits and vegetables to reduced risk of certain types of cancer.
  
  
• Effect on hormone metabolism. Some phytochemicals can mimic or alter the hormone estrogen in the body. Phytochemicals that act in this way are also referred to as phytoestrogens. These actions may provide estrogen-related benefits (e.g., lowered cholesterol levels, strong bones, healthy heart, relief from hot flashes associated with menopause). It may also provide anti-estrogen benefits, such as a reduced risk of reproductive cancers (e.g., breast cancer, ovarian cancer). Phytoestrogens may also enhance communication among body cells. Phytochemicals with these possible actions include certain isoflavones (e.g., daidzein, genistein) lignans and indoles.
  

  

• Stimulation of enzymes. Certain phytochemicals can trigger enzymes to act in such a way that reduces the risk of disease (e.g., cancer). Stimulated enzymes may neutralize and/or remove carcinogens from the body. Phytochemicals that may perform this type of activity include phenolic acids (e.g., curcumin, ellagic acid), organosulfur compounds (e.g., isothiocyanates) and protease inhibitors.
  
  
• Prevention of potentially harmful DNA replication. Some phytochemicals can interfere with the replication of cells, which may inhibit growth of cancer cells. Phytochemicals such as monoterpenes, resveratrol and saponins may act in this way.
  
  
• Antibacterial effects. The phytochemical allicin (found in garlic) may inhibit the growth of particular types of bacteria in the body.