Over the past decade or so, more and more attention has focused upon free radicals or oxidants and their counterparts, antioxidants. Once we understand free radicals, it is easy to appreciate the importance of nutrients associated with antioxidant activities of vitamins and minerals such as vitamins C and E and selenium, copper, iron, manganese, and zinc as well as other nutrients such as lycopene, lutein, and zeaxanthin.
A free radical is a substance that interacts with other molecules by taking an electron from them or by forcing an electron upon them. In most cases it is the former event. You will remember that earlier we called the process of losing an electron oxidation and the process of gaining an electron reduction. The major difference between proper oxidation and reduction and the damaging activity of free radicals is a matter of acceptability and stability of the molecules that free radicals interact with. Since free radicals often interact with molecules that do not want to give up an electron, free radicals can be viewed as biological bullies. They will interact with other molecules without regard for the stability of these molecules.
Typically, free-radical substances include oxygen, for example:
- superoxide (O2−)
- hydrogen peroxide (H2O2)
- hydroxyl radicals (OH−)
One obvious feature of the free radicals just listed is that they closely resemble the oxygen (O2) we breathe—so how abnormal could they be?
The presence of free radicals in our body is not necessarily a disease and seems to be unavoidable. That’s because free radicals are normally produced when we breakdown carbohydrates, protein, and fat for energy. Furthermore, certain immune processes purposely generate free-radical substances to attack foreign entities or debris in our body. However, free radicals can certainly lead to disease if their presence becomes too great and they are left to their own devices. This tends to happen when we allow free radicals access to our body via the foods we eat and the substances we breathe. Cigarette smoke is loaded with free-radical substances, probably more than one hundred different kinds.
Free radicals are molecules that can take electrons from other molecules thereby causing damage.
Free radicals can cause damage within the human body by attacking extremely important molecules such as DNA, proteins, and special fatty acids. If these or other molecules are attacked by free radicals and have an electron removed from their structure (oxidation) it is like pulling a bottom card from a house of cards. The victimized molecule is rendered weak and unstable and subject to breakdown. An example of this oxidative damage can be demonstrated by leaving vegetable oil out in an open container exposed to sunlight. The presence of oxygen and energy from sunlight leads to the formation of oxygen-based free radicals, which attack the fat causing them to break down in smaller molecules. Some of these molecules can produce an offensive odor and taste.
Throughout time we have accepted the presence of free radicals, and our body has evolved to meet the challenge. We are armed with a battery of antioxidants to keep the free radicals in check. The term antioxidant implies that these molecules will prevent free radicals from pulling electrons (oxidation) from other molecules. They may do so by donating their own electrons to a free radical. This pacifies a free radical and spares other molecules. Antioxidants are unique because they remain relatively stable after giving up an electron. They are designed to handle this process.
Congratulations for making it through Chapter 1. For many people these concepts may seem easy; however, for others, they may present more of a challenge. One thing is certain: if you have at least a general comprehension of these concepts, nutrition becomes a lot easier to understand. In Chapter 2 we discuss some of the finer aspects of the structure and function of our body.
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