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Dietary antioxidants: Part I

Rohini Diniz

Stress is part and parcel of modern life and is a leading cause of many illnesses. Any kind of stress triggers a series of hormonal changes in the body which in turn produce certain pro-inflammatory substances including free radicals that lead to cellular damage through the process of oxidation, leading to degenerative diseases.

An antioxidant is a functional property of specific vitamins, minerals, enzymes and plant chemicals (phytochemicals) that protect the body’s cells and tissues from harmful effects of oxidation caused by free radicals. Free radicals are derivatives of oxygen and other compounds that lose electrons in the course of circulation through the blood stream and become highly reactive as they try to regain chemical stability by snatching electrons from other molecules.

The human body exists in an oxidative environment and produces free radicals during normal metabolism. As the body uses glucose and oxygen to generate energy, free radicals and reactive oxygen species (ROS) get formed. Environmental factors such as pollution, heavy metals (mercury, lead, etc.), food additives, pesticides, cigarette smoke, alcohol, exposure to radiation and sunlight produce free radicals in our bodies. Free radicals are also obtained from consumption of high fat fried foods and char – grilled foods.

There are various types of free radicals that cause tissue damage. Some examples of free radical damage include damage to cell membrane lipids, cellular proteins and DNA and damage to lens proteins in the eye. These changes are an important contributing factor to the onset of several degenerative diseases like cancer, cataract, coronary heart disease, chronic vascular disease, impaired brain function and ageing itself.

Antioxidants sacrifice themselves to free radicals by donating electrons to stabilise and neutralise their harmful effects thereby preventing their reaction with other compounds. The reaction defers depending on different antioxidants. The human body contains certain enzymes that constitute the body’s ‘natural antioxidant system’ that minimises the formation and reaction of free radicals. By themselves these systems are not fully effective and need the support of dietary antioxidants in order to minimise oxidative damage and strengthen molecular repair systems.

Nutrition has great influence on the production of free radicals. Food contains a large number of nutrient and non-nutrient antioxidants. Vitamin E, vitamin C, minerals such as selenium, manganese, zinc, copper, iron carotenoids and flavonoids all function as antioxidants. Studies have shown that consuming foods rich in these nutrients decreases the risk of some, but not all cancers and cardiovascular disease.

The best sources of dietary antioxidants are fruits and vegetables, spices and whole grains. A balanced diet containing abundant fruits and vegetables can be the most effective way to protect the body against various oxidative stresses.

Among the antioxidant compounds found in fruits and vegetables are carotenoids present in deep orange, bright yellow and red vegetables and fruits such as carrots, pumpkins, sweet potatoes, mangoes, peaches, apricots, muskmelon (chibud, cantaloupe and honeydew), tomatoes, watermelon, grapefruit, strawberries, raspberries, cherries, etc.

There are around six hundred different carotenoids present in plant foods. Among them b-carotene, lycopene and lutein are well-known fighters in the war against free radicals. Studies have shown that b-carotene found in green leafy vegetables and yellow-orange vegetables and fruits is a powerful antioxidant and cancer preventer in the body. Lycopene, another carotenoid is also a powerful antioxidant and appears to protect the body against cancer and cardiovascular disorders. Lycopene is most concentrated in cooked tomato products such as soups, sauces, ketchups and chutneys as the heating process makes it easier for the body to absorb lycopene.

Lycopene is fat soluble, so it must be eaten with small amounts of fat. Lutein, another carotenoid found in green leafy vegetables has been found to decrease the risk of developing age related macular degeneration (AMD), an eye disorder that affects one in three people over the age of 75 years. It may also help prevent formation of cataracts, reduce the risk of heart disease and protect against breast cancer.

Jambuls, mulberries, plums, black grapes, brinjals, kokum, mangosteen, blackberries and blue berries, tea, cocoa and red wine contain flavonoids and polyphhenols which are powerful antioxidants and have an anticancer and cardioprotective role. Citrus fruits such as oranges, sweet limes, pummelos, grapefruit, lime, lemon and kiwi contain vitamin C which is a powerful antioxidant. The peel, membranous parts and pulp of citrus fruits contain bioflavonoids that have been shown to enhance the action of vitamin C in providing a powerful defence against oxidative stress.

Cruciferous vegetables like cabbage, cauliflower, broccoli, brussel sprouts, etc, contain isothiocyanates and indoles that have been shown to have anticancer properties.

 

 

To be continued. . .

 

(The writer is a consultant nutritionist with 17 years of experience, practising at Panaji and Margao)

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