Plant –based foods contain thousands of natural chemicals called phytochemicals or phytonutrients. More
than 1000 phytonutrients are found in plant foods. The word phyto
in Greek means plants. Phytochemicals generally
protect the plants against bacteria, viruses, fungi and other pest organisms.
These phytochemicals are found in plant – based foods such as fruits,
vegetables, beans and grains. The
phytochemicals serve as antioxidants (cancer fighting chemicals), increase
immunity, stimulate enzymes, and mimic hormone action and binds to cell walls. Nutritional
scientists suggest that the foods containing phytochemicals, antioxidants and
omega – 3- fatty acids reduce the risk of cancer development in human beings.
Mechanism of action of phytochemicals
1. Antioxidant effects – prevent free radical damage e.g., flavonoids
phytochemicals
2. Effects on xenobiotic metabolism – detoxify and eliminate
dietary carcinogens e.g., glucosinolates of cruciferous vegetables.
3. Hormonal effects (estrogenic/anti-estrogenic) –
estrogenic activity of phytoestrogens e.g., isoflavones of soybeans.
4. Effects on signal transduction (cell regulation) –regulate
cascades of enzyme action.
5. Anti-inflammatory and immune stimulatory effects –
immunostimulatory effects e.g., flavonoids, phytoestrogens.General category of phytochemicals
They include
carotenoids, ellagic acid, flavonoids, resveratrol, glucosinolates and
phytoestrogens.
Carotenoids
More than 600 carotenoids present in fruits and vegetables
give yellow, orange and red colours. Carotenoids include alpha –carotene,
beta-carotene and beta – cryptoxanthin. Human body can convert all of these
phytochemicals into vitamin A. Carotenoids act as antioxidants, help to improve
immunity. Yellow and orange foods like pumpkin and carrots are good source of
alpha and beta –carotene whereas sweet red peppers contain beta-cryptoxanthin.
Lycophene gives red or pink colour to tomatoes, water melon and pink grapes.
Lutein and Zeaxanthin are present in
greens such as spinach, kale, and collards. These chemical prevent cataract,
age-related macular degeneration and eye problems.
Ellagic acid is found in straw berries, rasp berries and pomegranates.
They help to protect from cancers.
Flavonoids are pigments that are responsible yellow, orange
and red colour in foods. They include catechins (green tea), hesperidin (citrus
fruits) and flavonols (apples, berries, grapes and onions. They all help to
prevent cancers.
Resveratrol is found
in grapes and red wine. It acts both as antioxidants and anti-inflammatory
agents.
Phytosterols are found in almonds, cashews, pea nuts,
soyabeans, maize, and whole wheat.
Tocopherol is vitamin E present in dark green leafy
vegetables, legumes and nuts.
Antioxidants
They are substances that inhibit the oxidation process and
act as protective agents of human body. They protect the body from dangerous
free radicals, which normally form during chemical processes. Free radicals are incomplete, highly unstable, reactive compounds or molecules.Free radicals are continuously produced in our cells. Free radicals
attack healthy cells and damage our genetic material DNA and allowing cancers
to develop. Antioxidants protect the body from such free radicals e.g., vitamin
C, beta carotene and vitamin E. Polyphenols scavenge carcinogens and mutagens. Carotenoids and ascorbates quench free radicals. Sulfur- containing compounds can stimulate DNA repair.Certain phytochemicals can alter hormone metabolism.
Health benefits of antioxidants
- Antioxidants prevent or neutralize or delay the oxidation reactions caused by free radicals.
- Antioxidants play a beneficial role in the prevention of disease e.g, heart disease, stroke. They slow the aging process.
- Antioxidants prevent free radical damage to the delicate lining of blood vessels, brain and nervous system.
- Antioxidants prevent or interfere with the development of cancer. They protect human body cells from the ravages of inflammation. Inflammation is known to be associated with increased levels of lipid peroxides and free radicals.
- Antioxidants are critical enzyme helpers.
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