are plant-derived chemical compounds under scientific research for their potential health-promoting properties, but with unproved benefits. "Phytonutrients" refers to plant-derived essential nutrients
scientifically confirmed as important to human health.
Phytochemicals as therapeutics
There is evidence from laboratory studies that phytochemicals in fruits and vegetables may reduce the risk of cancer
, possibly due to dietary fibers
, polyphenol antioxidants
effects. Specific phytochemicals, such as fermentable dietary fibers
, meet significant scientific agreement to be allowed limited health claims by the US Food and Drug Administration (FDA).
Phytochemicals have been used as drugs for millennia. For example, Hippocrates may have prescribed willow tree leaves to abate fever. Salicin, having anti-inflammatory and pain-relieving properties, was originally extracted from the white willow tree and later synthetically produced to become the staple over-the-counter drug called Aspirin.
An important cancer drug, Taxol (paclitaxel), is a phytochemical initially extracted and purified from the Pacific yew tree.
Among edible plants with health promoting phytochemicals, diindolylmethane, from Brassica vegetables (broccoli, cauliflower, cabbage, kale, Brussels sprouts) may be useful for recurring respiratory papillomatosis tumors (caused by the human papilloma virus), is in Phase III clinical trials for cervical dysplasia (a precancerous condition caused by the human papilloma virus) and is in clinical trials sponsored by the National Cancer Institute of the United States for a variety of cancers (breast, prostate, lung, colon, and cervical). The compound is being studied for anti-viral, anti-bacterial and anti-cancer properties through a variety of pathways and has been shown to synergize with Taxol in its anti-cancer properties, making it a possible anti-cancer phytochemical as taxol resistance is a major problem for cancer patients.
Some phytochemicals with physiological properties may be elements rather than complex organic molecules. Abundant in many fruits and vegetables, selenium, for example, is involved major metabolic pathways, including thyroid hormone metabolism and immune function. Particularly, it is an essential nutrient and cofactor for the enzymatic synthesis of glutathione, an endogenous antioxidant.
Clinical trials and health claim status
There are currently many phytochemicals possibly having medicinal properties in clinical trials for a variety of diseases. Lycopene, for example, from tomatoes has been tested in clinical trials for cardiovascular diseases and prostate cancer. These studies, however, did not attain sufficient scientific agreement to conclude an effect on any disease. The FDA position reads:
"Very limited and preliminary scientific research suggests that eating one-half to one cup of tomatoes and/or tomato sauce a week may reduce the risk of prostate cancer. The FDA concludes that there is little scientific evidence supporting this claim."
Likewise, although lutein and zeaxanthin may affect visual performance and inhibit macular degeneration and cataracts, there was insufficient scientific evidence from clinical trials for such a specific effect or health claim.
Many phytochemicals have anti-inflammatory properties in vitro, including turmeric and chia. Inflammation is a factor in many diseases of aging including Alzheimer's and arthritis. Turmeric is also reported to be active against skin cancer (melanoma).
Clinical investigations continue to assess phytochemicals with medicinal properties.
Food processing and phytochemicals
Phytochemicals in freshly harvested plant foods may be destroyed or removed by modern processing techniques, possibly including cooking. For this reason, industrially processed foods likely contain fewer phytochemicals and may thus be less beneficial than unprocessed foods. Absence or deficiency of phytochemicals in processed foods may contribute to increased risk of preventable diseases.
Interestingly, a converse example may exist in which lycopene, a phytochemical present in tomatoes, is either unchanged in content or made more concentrated by processing to juice or paste, maintaining good levels for bioavailability.
List of foods high in phytonutrients
Foods high in phytonutrients
, or superfoods
- soy – protease inhibitors, beta sitosterol, saponins, phytic acid, isoflavones
- tomato – lycopene, beta carotene, vitamin C
- broccoli – vitamin C, 3,3'-Diindolylmethane, sulphoraphane, lignans, selenium
- garlic – thiosulphonates, limonene, quercitin
- flax seeds and oil seeds – lignans
- citrus fruits – monoterpenes, coumarin, cryptoxanthin, vitamin C, ferulic acid, oxalic acid
- blueberries – tannic acid, lignans, anthocyanins
- sweet potatoes – beta carotene
- chilli peppers – capsaicin
- legumes: beans, peas, lentils – omega fatty acids, saponins, catechins, quercetin, lutein, lignans
Other foods rich in phytonutrients or superfoods
Some animal derived foods are also considered superfoods.
Beginning in 2005, there has been a rapidly growing recognition of several common and exotic fruits recognized for their nutrient richness
qualities, with over 900 new product introductions worldwide. More than a dozen industry publications on functional foods
and beverages have referred to various exotic or antioxidant species as superfruits
, some of which are included in the list below.
- Apples – quercetin, catechins, tartaric acid
- Açaí berries – dietary fiber, anthocyanins, omega-3, omega-6, omega-9, protein, beta-sitosterol, polyphenols. Açaí is the highest scoring plant food (spices excepted) for antioxidant ORAC value
- Dried apricots
- Artichoke – silymarin, caffeic acid, ferulic acid
- Brassicates: kale, cabbage, brussels sprouts, cauliflower – lutein
- Carrots – beta-carotene
- Cocoa – flavonoids, epicatechin
- Purple corn – anthocyanins
- Cranberries – ellagic acid, anthocyanins
- Gac – beta-carotene, lycopene
- Goji (wolfberry) - ellagic acid, β-carotene, β-cryptoxanthin, zeaxanthin, lutein, lycopene, riboflavin, vitamin C, copper, selenium, zinc, protein
- Pink grapefruit – lycopene
- Red grapes and wine – quercitin, resveratrol, catechins, ellagic acid
- Green tea – quercetin, catechins, oxalic acid
- Mangos – cryptoxanthin
- Mangosteen - xanthones
- Nuts and seeds – resveratrol, phytic acid, phytosterols, protease inhibitors
- Porridge oats soluble fibre magnesium, zinc
- Okra -- beta carotene, lutein, zeaxanthin
- Olive oil – monounsaturated fat, hydroxytyrosol, oleuropein, oleocanthal
- Onions – quercetin, thiosulphonates
- Papaya – cryptoxanthin
- Bell peppers – beta-carotene, vitamin C
- Pomegranate - vitamin C, tannins, especially punicalagins
- Pumpkin – lignans, carotene
- Quinoa dietary fiber, protein without gluten with balanced essential amino acids
- Sea buckthorn - vitamin C, tocopherols, carotenoids, polyphenols, polyunsaturated fatty acids
- Sesame - lignans
- Shiitake mushrooms
- Spinach – oxalic acid, lutein, zeaxanthin
- Watermelon – lycopene zeaxanthin, sulphoraphane, indole-3-carbinol
- Spirulina - beta-carotene
- Page 213 of, "Nutrition for Life" by Hark & Deen published 2006 by Dorling Kindersley
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