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Phytochemicals and their Potential Health Benefits

The term phytochemicals (phyto = plant) refers to a specific category of non-nutrient substances in plant foods that are associated with positive health effects. Phytochemicals are produced by plants for their own protection and are not necessary for the human body to function. Thus, no recommended daily allowances exist for these substances. Despite that phytochemicals are often associated with a wide variety of health benefits.

Phytochemicals are present in almost all fruits and vegetables as well as in legumes, grains, seeds, nuts and tea. Plants produce phytochemicals for their own survival. Certain phytochemicals provide color, flavor and aroma to plants and their flowers and fruits to help attract pollinators and seed disseminators or they perform actions that protect a plant from damage due to bacteria, viruses, fungi or insects and the ultraviolet radiation. Therefore, many plants produce antioxidants to protect themselves against radiation damage caused by the sun’s ultraviolet light. When plants and their fruits are consumed by humans, these phytochemicals appear to provide protection to the human body too.

Although there are thousands of different phytochemicals, new molecules are still being discovered. Most people obtain phytochemicals from consuming plant foods, though many phytochemicals are also available in supplement form. However, most experts recommend people receive phytochemicals naturally from foods rather than supplements because phytochemicals work in conjunction with other healthful substances contained in food like vitamins and minerals to produce their beneficial effects.

Types of Phytochemicals

There are many different ways of organizing thousands of existing phytochemicals. From a nutritionist point of view they are referred to by their potential activity in the body (e.g., as antioxidants or antibacterial). Researchers usually categorize phytochemicals into classes based on similar chemical structures (see also “Types of Phytochemicals and their Effects on the Human Body”). Frequently, phytochemicals in the same class also have a similar effect on the body. These classes include:

  • Phenols include flavonoids such as anthocyanins, catechins, isoflavones and resveratrol as well as phenolic acids and lignans.
  • Terpenes include carotenoids such as beta-carotene, lycopene, lutein and zeaxanthin as well as monoterpenes and saponins.
  • Thiols are also known as organosulfur compounds and include indoles and isothiocyanates.

Potential Health Effects of Phytochemicals

It is difficult to substantiate potential health benefits of any single phytochemical because it is unclear whether such effects are the result of an individual phytochemical, group of phytochemicals working together or phytochemicals working with other substances present in food. However, despite a lack of conclusive scientific evidence, different phytochemicals have been credited with helping to prevent or treat conditions such as cardiovascular disease, hypertension, diabetes or even cancer. The assumed beneficial effects of phytochemicals in the human body include:

Effect on hormone metabolism. Certain phytochemicals, often referred to as phytoestrogens, have been found to mimic or alter the female hormone estrogen in the body. These actions may provide estrogen-related benefits such as lowered cholesterol levels, healthy heart, strong bones and relief from hot flashes associated with menopause. Phytochemicals with these possible effects include certain isoflavones such as daidzein or genistein, indoles and lignans.

Antioxidant activity. Some phytochemicals are thought to prevent the cellular damage of free radicals. This effect may decrease the risk of heart disease and inhibit growth of cancer cells. Many different phytochemicals act as antioxidants, including flavonoids, carotenoids as well as phenolic acids such as tannins.

Prevention of potentially harmful DNA replication. Certain phytochemicals may interfere with the replication of DNA, which may in turn inhibit growth of cancer cells. Phytochemicals that are supposed to act in this way include monoterpenes, resveratrol and saponins.

Stimulation of enzymes. Some phytochemicals are thought to trigger enzymes to act in such a way that reduces the risk of disease because stimulated enzymes neutralize and/or eliminate carcinogens from the body. Phytochemicals that may possess this type of effects include organosulfur compounds like isothiocyanates, phenolic acids like curcumin or ellagic acid and protease inhibitors.

Antibacterial effects. A good example is the phytochemical allicin found in garlic, which is believed to inhibit the growth of certain types of harmful bacteria in the body.

Moreover, some other phytochemicals have been associated with promoting immune-system function, fighting inflammation, inhibiting blood clots, counteracting the harmful effects of carcinogens in the body and even repairing cellular damage to DNA.

Potential Risks of Phytochemicals

Phytochemicals obtained naturally from the diet are generally thought to be safe. However, there is no reliable scientific evidence that taking phytochemical supplements is also beneficial. Although it is unclear whether any potential risks may be associated with phytochemicals, it is possible that some phytochemicals, especially when taken in large doses as supplements, may have possible side effects or may interact with other substances in the body, e.g., medications. There are only few documented cases suggesting that certain phytochemicals may also be harmful. For instance, some studies have shown that overdosing on beta-carotene may increase the risk of lung cancer in smokers. Therefore, you should always speak to your doctor before taking phytochemical supplements.