Fruits and Nuts
Beans and seeds
List of antioxidants in food
- 1 Food sources
- 2 Vitamins
- 3 Vitamin cofactors and minerals
- 4 Hormones
- 5 Carotenoid terpenoids
- 6 Natural phenols
- 7 Other potential organic antioxidants
- 8 See also
- 9 References
- 10 External links
Main article: oxygen radical absorbance capacity
In the following discussion, the term “antioxidant” refers mainly to non-nutrient compounds in foods, such as polyphenols, which haveantioxidant capacity in vitro and so provide an artificial index of antioxidant strength – the ORAC measurement. Other than for dietary antioxidant vitamins – vitamin A, vitamin C and vitamin E – no food compounds have been proved with antioxidant efficacy in vivo. Accordingly, regulatory agencies like the Food and Drug Administration of the United States and the European Food Safety Authority(EFSA) have published guidance disallowing food product labels to claim an inferred antioxidant benefit when no such physiological evidence exists.
Polyphenols in foods
Many common foods contain rich sources of polyphenols which have antioxidant properties only in test tube studies. As interpreted by theLinus Pauling Institute, dietary polyphenols have little or no direct antioxidant food value following digestion. Not like controlled test tube conditions, the fate of flavones or polyphenols in vivo shows they are poorly conserved (less than 5%), with most of what is absorbed existing as metabolites modified during digestion and destined for rapid excretion.
Spices, herbs, and essential oils are rich in polyphenols in the plant itself and shown with antioxidant potential in vitro. Typical spices high in polyphenols (confirmed in vitro) are clove, cinnamon, oregano, turmeric, cumin, parsley, basil, curry powder, mustard seed, ginger,pepper, chili powder, paprika, garlic, coriander, onion and cardamom. Typical herbs are sage, thyme, marjoram, tarragon, peppermint,oregano, savory, basil and dill weed.
Dried fruits are a good source of polyphenols by weight/serving size as the water has been removed making the ratio of polyphenols higher. Typical dried fruits are pears, apples, plums, peaches, raisins, figs and dates. Dried raisins are high in polyphenol count. Red wine is high in total polyphenol count which supplies antioxidant quality which is unlikely to be conserved following digestion (see section below).
Deeply pigmented fruits like cranberries, blueberries, plums, blackberries, raspberries, strawberries, blackcurrants, figs, cherries, guava, oranges, mango, grape juice and pomegranate juice also have significant polyphenol content.
Sorghum bran, cocoa powder, and cinnamon are rich sources of procyanidins, which are large molecular weight compounds found in many fruits and some vegetables. Partly due to the large molecular weight (size) of these compounds, their amount actually absorbed in the body is low, an effect also resulting from the action of stomach acids, enzymes and bacteria in the gastrointestinal tract where smaller derivatives are metabolized and prepared for rapid excretion.
Despite the above discussion implying that ORAC-rich foods with polyphenols may provide antioxidant benefits when in the diet, there remains no physiological evidence that any polyphenols have such actions or that ORAC has any relevance in the human body.
On the contrary, research indicates that although polyphenols are good antioxidants in vitro, antioxidant effects in vivo are probably negligible or absent. By non-antioxidant mechanisms still undefined, polyphenols may affect mechanisms of cardiovascular disease or cancer.
The increase in antioxidant capacity of blood seen after the consumption of polyphenol-rich (ORAC-rich) foods is not caused directly by the polyphenols, but most likely results from increased uric acid levels derived from metabolism of flavonoids. According to Frei, “we can now follow the activity of flavonoids in the body, and one thing that is clear is that the body sees them as foreign compounds and is trying to get rid of them.” Another mechanism may be the increase in activities of paraoxonases by dietary antioxidants which can reduce oxidative stress.
- Vitamin A (retinol), also synthesized by the body from beta-carotene, protects dark green, yellow and orange vegetables and fruits from solar radiation damage, and is thought to play a similar role in the human body. Carrots, squash, broccoli, sweet potatoes,tomatoes (which gain their color from the compound lycopene), kale, mangoes, oranges, seabuckthorn berries, wolfberries (goji),collards, cantaloupe, peaches and apricots are particularly rich sources of beta-carotene, the major provitamin A carotenoid.
- Vitamin C (ascorbic acid) is a water-soluble compound that fulfills several roles in living systems. Important sources include citrus fruits (such as oranges, sweet lime, etc.), green peppers, broccoli, green leafy vegetables, black currants, strawberries, blueberries,seabuckthorn, raw cabbage and tomatoes. Linus Pauling was a major advocate for its use.
- Vitamin E, including tocotrienol and tocopherol, is fat soluble and protects lipids. Sources include wheat germ, seabuckthorn, nuts,seeds, whole grains, green leafy vegetables, kiwifruit, vegetable oil, and fish-liver oil. Alpha-tocopherol is the main form in which vitamin E is consumed. Recent studies showed that some tocotrienol isomers have significant anti-oxidant properties.
Vitamin cofactors and minerals
- Coenzyme Q10
- Manganese, particularly when in its +2 valence state as part of the enzyme called superoxide dismutase (SOD).
Main article: carotenoid
- Alpha-carotene – found in carrots, winter squash, tomatoes, green beans, cilantro, Swiss chard
- Astaxanthin – found naturally in red algae and animals higher in the marine food chain. It is a red pigment familiarly recognized in crustacean shells and salmon flesh/roe.
- Beta-carotene – found in high concentrations in butternut squash, carrots, orange bell peppers, pumpkins, kale, peaches, apricots, mango, turnip greens, broccoli, spinach, and sweet potatoes.
- Lutein – found in high concentration in spinach, kale, Swiss chard, collard greens, beet and mustard greens, endive, red pepper and okra
- Lycopene – found in high concentration in cooked red tomato products like canned tomatoes, tomato sauce, tomato juice and garden cocktails, gauva and watermelons.
- Zeaxanthin – best sources are kale, collard greens, spinach, turnip greens, Swiss chard, mustard and beet greens, corn, and broccoli
Natural phenols are a class of molecules found in abundance in plants.
- Flavanols and their polymers:
- Isoflavone phytoestrogens – found primarily in soy, peanuts, and other members of the Fabaceae family
Phenolic acids and their esters
Main article: polyphenol antioxidant
- Chicoric acid – another caffeic acid derivative, is found only in the popular medicinal herb Echinacea purpurea.
- Chlorogenic acid – found in high concentration in coffee (more concentrated in robusta than arabica beans), blueberries and tomatoes. Produced from esterification of caffeic acid.
- Cinnamic acid and its derivatives, such as ferulic acid – found in seeds of plants such as in brown rice, whole wheat and oats, as well as in coffee, apple, artichoke, peanut, orange and pineapple.
- Ellagic acid – found in high concentration in raspberry and strawberry, and in ester form in red wine tannins.
- Ellagitannins – hydrolyzable tannin polymer formed when ellagic acid, a polyphenol monomer, esterifies and binds with the hydroxyl group of a polyol carbohydrate such as glucose.
- Gallic acid – found in gallnuts, sumac, witch hazel, tea leaves, oak bark, and many other plants.
- Gallotannins – hydrolyzable tannin polymer formed when gallic acid, a polyphenol monomer, esterifies and binds with the hydroxyl group of a polyol carbohydrate such as glucose.
- Rosmarinic acid – found in high concentration in rosemary, oregano, lemon balm, sage, and marjoram.
- Salicylic acid – found in most vegetables, fruits, and herbs; but most abundantly in the bark of willow trees, from where it was extracted for use in the early manufacture of aspirin.
Other nonflavonoid phenolics
- Curcumin – Curcumin has low bioavailability, because, much of it is excreted through glucuronidation. However, bioavailability is substantially enhanced by solubilization in a lipid (oil or lecithin), heat, addition of piperine, or through nanoparticularization.
- Flavonolignans – e.g. silymarin – a mixture of flavonolignans extracted from milk thistle.
- Xanthones – mangosteen is purported to contain a large variety of xanthones, but some of the xanthones like mangostin might be present only in the inedible shell.
Other potential organic antioxidants
- Capsaicin, the active component of chili peppers
- Bilirubin, a breakdown product of blood, has been identified as a possible antioxidant.
- Citric acid, oxalic acid, and phytic acid
- N-Acetylcysteine, water soluble
- R-α-Lipoic acid, fat and water soluble
- Uric acid, in humans, accounts for roughly half the antioxidant capacity of plasma. Fructose, which is found abundantly in fruits, significantly elevates uric acid levels in humans, and thus indirectly increases antioxidant capacity. High levels of uric acid may be a protective factor against Parkinson’s disease and possibly other diseases related to oxidative stress.
- Guidance for Industry, Food Labeling; Nutrient Content Claims; Definition for “High Potency” and Definition for “Antioxidant” for Use in Nutrient Content Claims for Dietary Supplements and Conventional Foods U.S. Department of Health and Human Services, Food and Drug Administration, Center for Food Safety and Applied Nutrition, June 2008
- EFSA Panel on Dietetic Products, Nutrition and Allergies (2010). “Scientific Opinion on the substantiation of health claims related to various food(s)/food constituent(s) and protection of cells from premature aging, antioxidant activity, antioxidant content and antioxidant properties, and protection of DNA, proteins and lipids from oxidative damage pursuant to Article 13(1) of Regulation (EC) No 1924/2006”. EFSA Journal 8 (2): 1489.doi:10.2903/j.efsa.2010.1489.
- Lotito, S; Frei, B (2006). “Consumption of flavonoid-rich foods and increased plasma antioxidant capacity in humans: Cause, consequence, or epiphenomenon?”. Free Radical Biology and Medicine 41 (12): 1727–46.doi:10.1016/j.freeradbiomed.2006.04.033. PMID 17157175.
- David Stauth (5 March 2007). “Studies force new view on biology of flavonoids”. EurekAlert!; Adapted from a news release issued by Oregon State University.
- Williams, Robert J; Spencer, Jeremy P.E; Rice-Evans, Catherine (2004). “Flavonoids: antioxidants or signalling molecules?☆”. Free Radical Biology and Medicine 36 (7): 838–49.doi:10.1016/j.freeradbiomed.2004.01.001. PMID 15019969.
- Gross, P (2009). “New Roles for Polyphenols. A 3-Part report on Current Regulations & the State of Science”. Nutraceuticals World. Rodman Media. Retrieved April 11, 2013.
- Jonny Bowden, PhD, C.N.S. (16 Dec 2012). “ORAC no more!”. Huffington Post. Retrieved 12 Dec 2012.
- Arts, IC; Hollman, PC (2005). “Polyphenols and disease risk in epidemiologic studies”. The American journal of clinical nutrition 81(1 Suppl): 317S–325S. PMID 15640497.
- Aviram, M; Rosenblat, M (2005). “Paraoxonases and cardiovascular diseases: pharmacological and nutritional influences”. Current Opinion in Lipidology 16 (4): 393–9.doi:10.1097/01.mol.0000174398.84185.0f. PMID 15990587.
- Anand, Preetha; Kunnumakkara, Ajaikumar B.; Newman, Robert A.; Aggarwal, Bharat B. (2007). “Bioavailability of Curcumin: Problems and Promises”. Molecular Pharmaceutics 4 (6): 807–18.doi:10.1021/mp700113r. PMID 17999464.
- Kurien, Biji T.; Singh, Anil; Matsumoto, Hiroyuki; Scofield, R. Hal (2007). “Improving the Solubility and Pharmacological Efficacy of Curcumin by Heat Treatment”. ASSAY and Drug Development Technologies 5 (4): 567–76. doi:10.1089/adt.2007.064.PMID 17767425.
- Nair, Hareesh B.; Sung, Bokyung; Yadav, Vivek R.; Kannappan, Ramaswamy; Chaturvedi, Madan M.; Aggarwal, Bharat B. (2010).“Delivery of antiinflammatory nutraceuticals by nanoparticles for the prevention and treatment of cancer”. Biochemical Pharmacology80 (12): 1833–1843. doi:10.1016/j.bcp.2010.07.021.PMC 2974020. PMID 20654584.
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- Stocker, R; Yamamoto, Y; McDonagh, A.; Glazer, A.; Ames, B. (1987). “Bilirubin is an antioxidant of possible physiological importance”. Science 235 (4792): 1043–6.Bibcode:1987Sci…235.1043S. doi:10.1126/science.3029864.PMID 3029864.
- Zawiasa, A.; Szklarek-Kubicka, M.; Fijałkowska-Morawska, J.; Nowak, D.; Rysz, J.; Mamełka, B.; Nowicki, M. (2009). “Effect of Oral Fructose Load on Serum Uric Acid and Lipids in Kidney Transplant Recipients Treated with Cyclosporine or Tacrolimus”.Transplantation Proceedings 41 (1): 188–91.doi:10.1016/j.transproceed.2008.10.038. PMID 19249511.
- De Vera, Mary; Rahman, M. Mushfiqur; Rankin, James; Kopec, Jacek; Gao, Xiang; Choi, Hyon (2008). “Gout and the risk of parkinson’s disease: A cohort study”. Arthritis & Rheumatism 59(11): 1549–54. doi:10.1002/art.24193. PMID 18975349.
List of phytochemicals in food
While there is ample evidence to indicate the health benefits of diets rich in fruits, vegetables, legumes, whole grains and nuts, no specific food has been acknowledged by scientists and government regulatory authorities as providing a health benefit. Current medical research is focused on whether health effects could be due to specific essential nutrients or phytochemicals.
- 1 Terpenoids (isoprenoids)
- 2 Phenolic compounds
- 3 Glucosinolates
- 4 Betalains
- 5 Chlorophylls
- 6 Other organic acids
- 7 Protease inhibitors
- 8 See also
- 9 References
- α-Carotene – to vitamin A, in carrots, pumpkins, maize, tangerine, orange.
- β-Carotene – to vitamin A, in dark, leafy greens and red, orange and yellow fruits and vegetables.
- γ-Carotene – to vitamin A,
- Lycopene – Vietnam Gac, tomatoes, grapefruit, watermelon, guava, apricots, carrots, autumn olive.
- Phytofluene – star fruit, sweet potato, orange.
- Phytoene – sweet potato, orange.
- Canthaxanthin – paprika.
- Cryptoxanthin to vitamin A, in – mango, tangerine, orange, papaya, peaches, avocado, pea, grapefruit, kiwi.
- Zeaxanthin – wolfberry, spinach, kale, turnip greens, maize, eggs, red pepper, pumpkin, oranges.
- Astaxanthin – microalge, yeast, krill, shrimp, salmon, lobsters, and some crabs
- Lutein – spinach, turnip greens, romaine lettuce, eggs, red pepper, pumpkin, mango, papaya, oranges, kiwi, peaches, squash, brassicates, prunes, sweet potatoes, honeydew melon, rhubarb, plum, avocado, pear, cilantro.
- Rubixanthin – rose hips.
- Saponins – soybeans, beans, other legumes, maize, alfalfa.
- Oleanolic acid – American pokeweed, honey mesquite, garlic, java apple, cloves, and many other Syzygium species.
- Ursolic acid – apples, basil, bilberries, cranberries, elder flower, peppermint, lavender, oregano, thyme, hawthorn, prunes.
- Betulinic acid – Ber tree, white birch, tropical carnivorous plants Triphyophyllum peltatum and Ancistrocladus heyneanus, Diospyros leucomelas a member of the persimmon family, Tetracera boiviniana, the jambul (Syzygium formosanum), chaga, and many otherSyzygium species.
- Moronic acid – Rhus javanica (a sumac), mistletoe
- Limonene – oils of citrus, cherries, spearmint, dill, garlic, celery, maize, rosemary, ginger, basil.
- Perillyl alcohol – citrus oils, caraway, mints.
- Phytosterols – almonds, cashews, peanuts, sesame seeds, sunflower seeds, whole wheat, maize, soybeans, many vegetable oils.
- Tocopherols (vitamin E)
- Apiole – parsley, celery leaf.
- Carnosol – rosemary, sage
- Carvacrol – oregano, thyme, pepperwort, wild bergamot.
- Dillapiole – dill, fennel root.
- Rosemarinol – rosemary.
- Quercetin – red and yellow onions, tea, wine, apples, cranberries, buckwheat, beans.
- Gingerol – ginger.
- Kaempferol – tea, strawberries, gooseberries, cranberries, grapefruit, apples, peas, brassicates (broccoli, kale, brussels sprouts,cabbage), chives, spinach, endive, leek, tomatoes.
- Myricetin – grapes, red wine, berries, walnuts.
- Fisetin – strawberries, cucumbers – prevent Alzheimer
- Rutin – citrus fruits, oranges, lemons, limes, grapefruit, berries, peaches, apples, pagoda tree fruits, asparagus, buckwheat,parsley, tomatoes, apricots, rhubarb, tea.
- Isorhamnetin – red turnip, goldenrod, mustard leaf, ginkgo biloba.
- Acacetin – Robinia pseudoacacia, Turnera diffusa.
- Apigenin – chamomile, celery, parsley.
- Chrysin – Passiflora caerulea, Pleurotus ostreatus, Oroxylum indicum.
- Diosmetin – Vicia.
- Tangeritin – tangerine and other citrus peels.
- Luteolin – beets, artichokes, celery, carrots, celeriac, rutabaga, parsley, mint, chamomile, lemongrass, chrysanthemum
- Flavan-3-ols (flavanols)
- Catechins – white tea, green tea, black tea, grapes, wine, apple juice, cocoa, lentils, black-eyed peas.
- Theaflavin – black tea;
- Anthocyanidins (flavonals) or Anthocyanins – red wine, many red, purple or blue fruits and vegetables.
- Pelargonidin – bilberry, raspberry, strawberry.
- Peonidin – bilberry, blueberry, cherry, cranberry, peach.
- Cyanidin – red apple & pear, bilberry, blackberry, blueberry, cherry, cranberry, peach, plum, hawthorn, loganberry, cocoa.
- Delphinidin – bilberry, blueberry, eggplant.
- Malvidin – malve, bilberry, blueberry.
- Isoflavones (phytoestrogens) use the 3-phenylchromen-4-one skeleton (with no hydroxyl group substitution on carbon at position 2).
- Pterocarpans or Coumestans (phytoestrogens)
- Coumestrol – red clover, alfalfa sprouts, soy, peas, brussels sprouts.
- Matairesinol – flax seed, sesame seed, rye bran and meal, oat bran, poppy seed, strawberries, blackcurrants, broccoli.
- Secoisolariciresinol – flax seeds, sunflower seeds, sesame seeds, pumpkin, strawberries, blueberries, cranberries, zucchini, blackcurrant, carrots.
- Pinoresinol and lariciresinol – sesame seed, Brassica vegetables
- Resveratrol – grape skins and seeds, wine, nuts, peanuts, Japanese Knotweed root
- Pterostilbene – grapes, blueberries
- Piceatannol – grapes
- Salicylic acid – peppermint, licorice, peanut, wheat.
- Vanillin – vanilla beans, cloves.
- Gallic acid – tea, mango, strawberries, rhubarb, soy.
- Ellagic acid – walnuts, strawberries, cranberries, blackberries, guava, grapes.
- Tannic acid – nettles, tea, berries.
- Caffeic acid – burdock, hawthorn, artichoke, pear, basil, thyme, oregano, apple, olive oil.
- Chlorogenic acid – echinacea, strawberries, pineapple, coffee, sunflower, blueberries.
- Cinnamic acid – cinnamon, aloe.
- Ferulic acid – oats, rice, artichoke, orange, pineapple, apple, peanut.
- Coumarin – citrus fruits, maize.
The precursor to isothiocyanates
- Sinigrin (the precursor to allyl isothiocyanate)- broccoli family, brussels sprouts, black mustard
- Glucotropaeolin (the precursor to benzyl isothiocyanate)
- Gluconasturtiin (the precursor to phenethyl isothiocyanate)
- Glucoraphanin (the precursor to sulforaphane) – Brassicates: broccoli, cauliflower, brussels sprouts, cabbages
- Dithiolthiones (isothiocyanates)
Organosulfides/ Organosulfur compounds
- Polysulfides (allium compounds)
- Diallyl disulfide – garlic, onions, leeks, chives, shallots.
- Indole-3-carbinol – cabbage, kale, brussels sprouts, rutabaga, mustard greens, broccoli.
- 3,3′-Diindolylmethane or DIM – broccoli family, brussels sprouts, cabbage, kale
- Allicin – garlic
- Alliin – garlic
- Allyl isothiocyanate – horseradish, mustard, wasabi
- Piperine – black pepper
- Syn-propanethial-S-oxide – cut onions.
- Betaxanthins (non glycosidic versions)
Other organic acids
- Saturated cyclic acids
- Oxalic acid – orange, spinach, rhubarb, tea and coffee, banana, ginger, almond, sweet potato, bell pepper.
- Tartaric acid – apricots, apples, sunflower, avocado, grapes, tamarind.
- Anacardic acid – cashews, mangoes.
- Malic acid – apples
- Caftaric acid
- Coutaric acid
- Fertaric acid
- Linus Pauling Institute at Oregon State University
- Linus Pauling Institute at Oregon State University
- Lignan contents of Dutch plant foods: a database i…[Br J Nutr. 2005] – PubMed Result
Other common name(s): certain phytochemicals may be called antioxidants, flavonoids, flavanols, flavanones, isoflavones, catechins, epicatechins, anthocyanins, anthocyanidins, proanthocyanidins, isothiocyanates, carotenoids, allyl sulfides, polyphenols, phenolic acids, and many other names
Scientific/medical name(s): various names
The term “phytochemicals” refers to a wide variety of compounds made by plants, but is mainly used to describe those compounds that may affect human health. Phytochemicals are found in plant-based foods such as fruits, vegetables, beans, and grains. Scientists have identified thousands of phytochemicals, although only a small fraction have been studied closely. Some of the better-known phytochemicals include beta carotene and other carotenoids, ascorbic acid (vitamin C), folic acid, and vitamin E.
Some phytochemicals have either antioxidant or hormone-like actions. There is some evidence that a diet rich in fruits, vegetables, and whole grains reduces the risk of certain types of cancer and other diseases. Researchers are looking for specific compounds in these foods that may account for these healthful effects in humans. Available scientific evidence does not support claims that taking phytochemical supplements is as good for long-term health as consuming the fruits, vegetables, beans, and grains from which they are taken.
How are they promoted for use?
Phytochemicals are promoted for the prevention and treatment of many health conditions, including cancer, heart disease, diabetes, and high blood pressure. There is some evidence that certain phytochemicals may help prevent the formation of potential carcinogens (substances that cause cancer), block the action of carcinogens on their target organs or tissue, or act on cells to suppress cancer development. Many experts suggest that people can reduce their risk of cancer significantly by eating more fruits, vegetables, and other foods from plants that contain phytochemicals.
There are several major groups of phytochemicals.
The polyphenols include a large subgroup of chemicals called flavonoids. Flavonoids are plant chemicals found in a broad range of fruits, grains, and vegetables. They are being studied to find out whether they can prevent chronic diseases such as cancer and heart disease. The isoflavones found in foods and supplements such as soy products, red clover, garbanzo beans, and licorice and the lignans found in flaxseed and whole grains might mimic the actions of the female hormone estrogen (see Licorice and Soybean). These seemingly estrogen-like substances from these plant sources are called phytoestrogens. They may play a role in the development of and protection against some hormone-dependent cancers such as some types of breast and prostate cancer.
Other polyphenols (including some flavonoids) act as antioxidants. These are thought to rid the body of harmful molecules known as free radicals, which can damage a cell’s DNA and may trigger some forms of cancer and other diseases. These compounds are commonly found in teas and in vegetables such as broccoli, Brussels sprouts, cabbage, and cauliflower. Grapes, eggplant, red cabbage, and radishes all contain anthocyanidins — flavonoids that are thought to act as antioxidants and may protect against some cancers and heart disease. Quercetin, another flavonoid that appears to have antioxidant properties, is found in apples, onions, teas, and red wine. Ellagic acid, found in raspberries, blackberries, cranberries, strawberries, and walnuts, is being studied to see if it has anti-cancer effects (see Ellagic Acid).
Carotenoids, which give carrots, yams, cantaloupe, butternut squash, and apricots their orange color, are promoted as anti-cancer agents (see Vitamin A, Retinoids, and Provitamin A Carotenoids). Tomatoes, red peppers, and pink grapefruit contain lycopene, which proponents claim is a powerful antioxidant (see Lycopene). The phytochemicals lutein and zeaxanthin are carotenoids found in spinach, kale, and turnip greens that may reduce the risk of some cancers.
Another group of phytochemicals, called allyl sulfides, are found in garlic and onions (see Garlic). These compounds may stimulate enzymes that help the body get rid of harmful chemicals. They may also help strengthen the immune system.
What does it involve?
Phytochemicals are present in virtually all of the fruits, vegetables, legumes (beans and peas), and grains we eat, so it is quite easy for most people to include them in their diet. For instance, a carrot contains more than a hundred phytochemicals. There are thousands of known phytochemicals, but only a few have been studied in detail.
Many of the better-known phytochemicals can be purchased as dietary supplements. However, most available evidence suggests that these single supplements are not as good for you as the foods from which they are derived.
What is the history behind it?
Only a few years ago, the term “phytochemical” was barely known. But doctors, nutritionists, and other health care practitioners have long advocated a low-fat diet that includes a variety of fruits, vegetables, legumes, and whole grains. Historically, cultures that consume such a diet have lower rates of certain cancers and heart disease.
Since the passage of the Dietary Supplement Health and Education Act (DSHEA) in the United States in 1994, a growing number of phytochemicals are being sold as dietary supplements.
What is the evidence?
The idea that a diet rich in fruits, vegetables, legumes, and grains reduces the risk of cancer, heart disease, and other illnesses is widely accepted. But only recently have researchers begun to try to learn the effects of specific phytochemicals contained in those foods.
Because of the number of phytochemicals and the complexity of the chemical processes in which they are involved, it is difficult for researchers to find out which phytochemicals in foods may fight cancer and other diseases, which may have no effect, and which may even be harmful.
Much of the evidence so far has come from observations of cultures in which the diet comes mainly from plant sources, and which seem to have lower rates of certain types of cancer and heart disease. For instance, the relatively low rates of breast and endometrial cancers in some Asian cultures are credited at least in part to dietary habits. These cancers are much more common in the United States, possibly because the typical American diet is higher in fat and lower in fruits, vegetables, legumes, and grains. Part of the lower risk in Asian cultures is likely due to other factors such as lower obesity rates and more exercise.
Many studies have looked at the relationship between cancer risk and eating fruits and vegetables, legumes, and whole grains. Most of the evidence indicates that eating a diet high in these foods seems to lower the risk of some cancers and other illnesses.
Some of the links between individual phytochemicals and cancer risk found in laboratory studies are compelling and make a strong case for further research. So far, however, none of the findings are conclusive. It is still uncertain which of the many phytochemicals in fruits and vegetables actively helps the body fight disease.
Researchers have also shown much interest in phytochemical supplements. Some laboratory studies in cell cultures and animals have shown that certain phytochemicals have some activity against cancer cells or tumors. But at this time there have been no strong studies in humans showing that any phytochemical supplement can prevent or treat cancer.
Until conclusive research findings emerge, the American Cancer Society’s 2012 nutrition guidelines recommend choosing what you eat and drink in amounts that help you get to and stay at a healthy weight. Eating a balanced diet that includes 2½ cups of vegetables and fruits each day and choosing whole grains over refined grains and sugar-sweetened products should be part of this plan. Limiting intake of red meats and processed meats such as bacon, sausage, lunch meats, and hot dogs is also recommended in order to help reduce cancer risk. A good way to do this is to choose fish, poultry, or beans for some meals rather than beef, pork, lamb, or processed meats. The guidelines note that although eating fish is linked to a lower risk of heart disease, the evidence regarding cancer in humans is limited. A balanced diet with foods from a variety of plant sources is likely to be more effective in reducing cancer risk than consuming large amounts of a few phytochemicals.
Are there any possible problems or complications?
Phytochemicals, in the amounts consumed in a healthy diet, are likely to be helpful and are unlikely to cause any major problems. Some people assume that because phytochemical supplements come from “natural” sources, they must be safe and free from side effects, but this is not always true. Many phytochemical supplements, especially when taken in large amounts, have side effects and may interact with some drugs. Some of these interactions may be dangerous. Before taking a phytochemical in supplement form, consider talking to your doctor and pharmacist to be sure it will not interact with other medicines or herbs you may be taking. Relying on the use of phytochemicals alone and avoiding or delaying conventional medical care for cancer may have serious health consequences