This article written by Sheela Krishnaswamy was first published in The Times of India dated July 23, 1998.
What do cancer, cardiovascular diseases, cataract, age-related disorders, inflammatory disorders and several other ailments have in common? Free radicals.
What do several foods contain that can fight the free radicals and reduce or prevent damage to the body? Antioxidants.
Free radicals are unstable oxygen molecules that are either produced in the body or found in the environment. In the body they are produced in the cells when oxygen, which is necessary for our existence, is utilised. Cigarette smoke, environmental pollution, severe exercise in untrained individuals, inflammation, radiation, some drugs, ozone, are some of the sources of free radicals. If they are not inactivated, they can damage a lot of things in the body including the DNA, proteins and lipids. When they play havoc inside, heart disease, cancer and cataract show up. Some studies suggest that free radicals may play a role in the causation of some of the disorders of the brain and nervous system, inflammatory diseases like rheumatoid arthritis, and decrease in immune function.
DNA damage is thought to be one of the most important contributors to cancer. Much of this damage is oxidative in nature. If a cell containing damaged DNA divides before its DNA can be repaired, the result is a permanent genetic alteration. This is the first step in the development of cancer. Free radicals may contribute to heart disease by oxidising LDL. Cataract occurs when transparent material in the lens of the eye becomes opaque. Oxidation is believed to be a major cause of damage to the proteins of the lens and this causes the lens to become cloudy.
Fortunately our bodies have protective mechanisms to detoxify these dangerous molecules. But these mechanisms may not be able to neutralise all the free radicals produced in the body as well as those that are obtained from the environment. The result is a condition called idants. An increase in the production of free radicals or a deficiency in the deficiency mechanism in the body could cause this imbalance. This is where our foods help. Many plant foods have been described to have curative value in the ancient Indian medical system and in the recent years, science is rediscovering these beneficial qualities of foods. Several naturally-occurring chemicals in foods can help to counteract the damaging effects of free radicals. Scientists believe that each of these compounds has a special role but many of them work together. Taking nutrients, as medicines do not have the same effect as taking in through food in their natural form because, there are several possible interactions between the nutrients. This is why we find that newer nutrients and non-nutrients are being added to the endless list of food benefits.
Vitamin C, beta-carotene, vitamin E and selenium are probably the most researched antioxidants. The September-October 97 issue of Lifeline Health Letter published in California says that researchers at the US Department of Agriculture analysed in a test tube, the ability of various common fruits and vegetables to mop up free radicals, compared with the antioxidant ability of vitamins C and E. They found, for instance, that 3/4 cup of cooked kale neutralised as many free radicals, as did 599 mgs of vitamin C, or 837 IU of vitamin E, even though kale contains only 40 mgs of vitamin C and 10 IU of vitamin E. Some of the other antioxidants that you might read about more often in the future are sulphur amino acids, carotenoids, flavonoids, anthocyanins, phenolic compounds and indoles.
In a seminar on "Current perspectives on food antioxidants in health" organised by Hindustan Lever Research Centre and held in Bangalore last month, Dr Kamala Krishnaswamy, director, National Institute of Nutrition, Hyderabad, said that both nutrients and non-nutrients form a part of the antioxidant defence system. Several phytochemicals (phyto means plant in Greek) like phenolic compounds, flavonoids, lignins, etc fall under the non-nutrient category. The activity of these substances present in foods can fight cancer, infection, allergy, cholesterol and so on.
The dietary sources of antioxidants are vegetables, fruits, grains, spices, herbs and beverages. Here are some examples:
• Green leafy vegetables - rich in carotenoids, fruits, yellow vegetables flavonoids and vitamin C
• Wheat, corn, rice, soybean - contain phenolic acids
• Germ portion of cereals - rich in vitamin E
• Turmeric - contains curcumin, a powerful antioxidant
• Garlic - contains sulphur compounds
• Mustard - contains isothiocyanates
• Green tea and black tea - contain polyphenols and catechins
However, the polyphenols in tea interfere with iron absorption when tea is taken with a meal. It is safer to drink it between meals than with a meal. There is no single mechanism by which oxidative stress kills or injures cells. A number of studies have proved that a high intake of fruits and vegetables are associated with a protective effect against cancer, cardiovascular disease and cataract.
It is important to remember that no single antioxidant will protect against every type of damage and no supplement is a cure-all for damage from free radicals. The best way to protect ourselves would be to include lots of fruits, vegetables and whole grains in our daily food and to exercise daily under proper guidance in order to increase antioxidant defences and decrease tissue injury.
