The term “phyto” originates from a Greek word meaning plant.
Phytonutrients (or phytochemicals) are organic components found in plants and some phytonutrients can promote human health.
Common classes of phytonutrients include: carotenoids, flavonoids (polyphenols) including isoflavones (phytoestrogens), inositol phosphates (phytates), lignans (phytoestrogens), isothiocyanates and indoles, phenols and cyclic compounds, phyto-sterols and stanols, saponins, sulfides, thiols, terpenes, and some vitamins (carotenoids such as lycopene, beta-carotene, etc.).
Of all the phytonutrients, the carotenoids have been studied extensively. Carotenoids consist of alpha-carotene, beta-carotene, beta-cryptoxanthin, lutein, lycopene, zeaxanthin, astaxanthin, and many others. Carotenoids are commonly found in red, orange and yellow pigments in fruits and vegetables.
Polyphenols are natural components of a wide variety of plants and can be classified as non-flavonoids (i.e. ellagic acid) and flavonoids (i.e. anthocyanins, catechins, flavonones, flavones, flavonols and isoflavones). Dietary sources rich in polyphenols are onion, apple, tea, red wine, grapes/grape juice, strawberries, blueberries, raspberries, cranberries and certain nuts.
Phytonutrients are not “essential” like traditional nutrients (protein, fat, vitamins, minerals).
Although many phytonutrients have been identified, there are likely thousands more that remain to be discovered.
Phytonutrients can protect humans against certain diseases, such as cancer, heart disease and age-related macular degeneration. There are some proposed mechanisms by which phytonutrients may protect human health. Phytonutrients may:
serve as antioxidants
enhance immune response
alter estrogen metabolism
convert to vitamin A (beta-carotene)
cause cancer cells to die (via apoptosis)
repair DNA damage caused by toxins or pollutants (e.g. smoking).
detoxify carcinogens through activation of the cytochrome P450 and Phase II enzyme systems.
Rich sources of phytonutrients are fruits, vegetables, grains, legumes, nuts and teas. Yellow, orange and red pigmented fruits and vegetables contain carotenoids. Dark, leafy green vegetables contain carotenoids as well. Reddish pigments in grape skins and citrus fruits contain flavonoids. Peanuts, lentils, soy and other legumes contain isoflavones. Foods high in phytonutrients include:
Many interactions are possible with phytonutrients and only a few are listed here.
Citrus bioflavonoid preparations, such as grapefruit juice, may interact with drugs containing naringin. Naringin increases the oral bioavailability of calcium channel blocker medications such as: nifedipine, verapramil and felodipine. Naringin may enhance the effect of these drugs and result in a serious drop in blood pressure. Naringin also inhibits the breakdown of various drugs such as caffeine, coumarin, and estrogens.4 Avoid grapefruit juice and flavonoid preparations containing naringin (e.g. citrangedin, grapefruit, kumquat, and pummelo or bioflavonoid supplements containing naringin) when taking any of these drugs.
Evidence from epidemiological studies has demonstrated that fruit and vegetable consumption is protective of human health and is linked to a lower risk for chronic diseases, including certain cancers and heart disease. General Health: It has been notes that Americans are not consuming the recommended amount of fruits and vegetables daily. Research suggests consuming an array of colorful fruits and vegetables, rich in phytonutrients on a daily basis. Among some of the phytonutrient-rich fruits and vegetables are: red foods (tomatoes, strawberries, apples, cranberries, red grapes), green foods or cruciferous vegetables (broccoli, brussel sprouts, kale), white-green foods (garlic, onions), and other food/substances such as soybeans and green tea.5678
A key consideration is whether a purified phytonutrient has the same health benefit as the whole food or mixture of foods where the phytonutrient is present. One study found that the vitamin C in apples with skin accounted for only 0.4% of the total antioxidant activity of the fruit. This suggests that most of the antioxidant activity of fruits and vegetables may come from phenolics and flavonoids. It is possible that an additive or synergistic effect from whole fruits and vegetables is the best way to provide potent antioxidant activity.9 Cancer: There is an abundance of epidemiological evidence linking a diet high in certain phytochemicals and a reduced risk for developing cancer. Phytopolyphenols such as apigenin, curcumin, genistein, catechins and theaflavins have shown to be effective with inhibiting carcinogenesis in animals.10 Phytochemicals in foods may affect production and early growth of tumors in humans by altering how cells respond to genetic damage or a carcinogenic agent.11
Cruciferous vegetables have shown to blunt tumor growth in animal models; phytoestrogens from soybeans may help reduce risk for breast cancer; and plant anthocyanins can reduce the rate of oxidative damage within the human body.1213 Epidemiological data suggests that consumption of cruciferous vegetables may reduce cancer risk. Cruciferous plants are rich in glucosinolates and converted to isothiocyanates by plant enzymes and gastrointestinal microflora. Certain isothiocyanates and glucosinolates have shown to effectively block chemical carcinogenesis in animal models. A number of isothiocyanates are also potent inducers of phase 2 proteins. A significant amount of experimental evidence supports the view that phase 2 enzyme induction is a highly effective strategy for reducing susceptibility to carcinogens.14
The anti-cancer properties in berry extracts have been documented. One paper describes the protective effect of strawberries, blueberries and raspberries against cervical and breast cancer. Freeze-dried fruits of blueberry and strawberry cultivars were extracted with solvents and tested against cultures of two aggressive cancer lines: 9MCF-7 and T47-D with different requirements for estrogen. Researchers found extracts from blueberry and strawberry significantly decreased the growth of cervical and breast cancer cells. One strawberry extract decreased the growth of breast cancer cells by 77%; a blueberry extract decreased growth of cervical cancer cells by 81%.11 In another study, the Ames assay was used to determine that ethanol extracts from raspberry extract strongly inhibited two aggressive cervical and breast cancer cell lines.15
Cranberries contain flavonol glycosides, anthocyanins, proanthocyanins (condensed tannins), and organic and phenolic acids. The antiproliferative effects of total cranberry extract (TCE) (200 microg/mL) versus all fractions were evaluated against human oral (KB, CAL27), colon (HT-29, HCT116, SW480, SW620), and prostate (RWPE-1, RWPE-2, 22Rv1) cancer cell lines. Antiproliferative activity of total polyphenols in TCE suggests synergistic or additive antiproliferative interactions of the anthocyanins, proanthocyanidins, and flavonol glycosides within the cranberry extract as compared to the individual phytochemicals in TCE.16
One study examined the combined effects of dietary soy phytochemicals and tea components on breast tumor progression in a clinically relevant in vivo model of MCF-7 androgen-dependent human breast tumor in female SCID mice. Mice were treated with genistein-rich soy isoflavones (GSI), soy phytochemical concentrate (SPC), black tea (BT), green tea (GT), SPC/BT combination and SPC/GT combination. Analysis of serum and tumor biomarkers showed that the combined effects of SPC and GT inhibited tumor angiogenesis, and reduced estrogen receptor (ER)-alpha and serum levels of insulin-like growth factor (IGF)-I. Results of this study suggest that dietary SPC plus GT may be used as part of a dietary regimen to effectively inhibit progression of estrogen-dependent breast cancer.17 Epigallocatechin gallate (EGCG), a powerful antioxidant derived from green tea extract, and genistein, a pharmacologically active isoflavone present in soy, are referred to as chemoprotective agents, due to their antioxidative and anti-inflammatory properties.18
Anthocyanins in tart cherries have been examined for their potential to inhibit intestinal tumor development in Apc(Min) mice and growth of human colon cancer cell lines. Results from mice consuming the cherry diet, anthocyanins or cyanidins show smaller and fewer cecal adenomas and reduce cell growth of cancer lines, as compared to the mice consuming the control diet. These results suggest that anthocyanins and cyanidins from tart cherry may reduce the risk of colon cancer.19Cardiovascular disease: Cardiovascular disease (CVD) remains the leading cause of morbidity and mortality in the U.S.
One hundred forty-seven original investigations and reviews of metabolic and epidemiologic studies, as well as dietary intervention trials regarding diet and coronary heart disease (CHD) prevention were reviewed. It was determined that consuming a diet high in fruits and vegetables, nuts, and whole grains, and low in refined grain products, is one of the successful dietary strategies to prevent CHD. It is well known that consuming a diet high in fruits and vegetables can help reduce risk for CHD, and phytonutrient content of fruits and vegetables are thought to play a role in this process.20
A high flavonoid intake may be beneficial for lowering risk for heart disease women. A cross sectional analysis of the SU.VI.MAX Study (an 8-year trial evaluating the effect of antioxidant supplementation on the incidence of major chronic diseases), involving 1286 women and 1005 men was performed. The relationship between flavonoid intake and cardiovascular risk factors was evaluated with covariance analyses with logistic regression analyses. Results showed flavonoid-rich food consumption was inversely related to systolic blood pressure in women (p= 0.005), but not in men. Women in the highest tertile of flavonoid-rich food consumption were at lower risk for cardiovascular disease [odds ratio (OR): 0.31; 95%CI: 0.14, 0.68]. These results suggest that a high consumption of flavonoids may help prevent cardiovascular disease in women.21 Aging/Cognitive Effects: Some research suggests that antioxidant-rich foods may be beneficial in delaying or reversing neuronal and behavioral aging.22
One study determined that a blueberry-supplemented diet may retard aging of the brain, and prevent elevated levels of the oxidative stress-responsive protein, nuclear factor-kappa B (NF-kappaB), in aged Fischer-344 rats. A blueberry-supplemented diet was given to 12 aged rats 4 months prior to testing, while 11 aged and 12 young rats were fed a control diet. The rats were tested for object recognition memory on the visual paired comparison task. Young rats and aged rats fed the blueberry diet, performed similarly and significantly better than the aged control diet group. In four brain regions, aged control diet rats had significantly higher average NF-kappaB levels than young animals on the control diet. Conversely, in four regions, aged blueberry diet rats had significantly lower levels of NF-kappaB than aged control diet rats. [ Note: Higher NF-kappa B levels are associated with poorer memory scores.] Results suggest that a blueberry-enriched antioxidant diet can prevent an age-related increase in NF-kappaB, a protein that responds to oxidative stress and is related to aging of the brain.23
A few studies examined whether long-term feeding of fruit and vegetable extracts (blueberry, strawberry or spinach extracts) could retard neuronal and cognitive function in Fischer 344 rats. One study found that antioxidant-rich supplements of fruit and vegetable extracts given to rats for 8 months beginning at 6 months of age decreased age-related declines in neuronal and cognitive function.24 Another follow-up study using strawberry, spinach or blueberry supplements reversed age-related deficits in 19-month old Fischer 344 rats fed for 8 weeks. These findings suggest that phytonutrients in antioxidant rich foods may be beneficial in slowing and/or reversing some neuronal and behavioral effects of aging.2224
Much is known about a high fruit and vegetable intake and a reduced risk of chronic diseases. One aspect of future research should focus on specific biomarkers or early predictors of these diseases to test the ability of foods and their components to prevent them.12
The dietary supplement information contained on this site has been compiled from published sources thought to be reliable, but it cannot be guaranteed. Efforts have been made to assure this information is accurate and current. However, some of this information may be purported or outdated due to ongoing research or discoveries. The authors, editors and publishers cannot accept responsibility for errors or omissions or for any consequences from applications of the information in this site and make no warranty, expressed or implied, with respect to the contents herein.
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