Antioxidants have been the hallmark of health and nutrition since the early 1970’s. Consumers, physicians and the media have been bombarded with the health benefits of antioxidants ever since. However, antioxidants came to prominence in the late 1800’s when first, the rubber and, later food companies found various antioxidants could prolong the life of their products. In the mid 1950’s Denham Harman, the father of antioxidant theory of ageing proposed that aging was a result of free radicals that were continually being generated in all the tissues! These free radicals originating from oxygen and nitrogen, like superoxide, singlet oxygen, hydroxyl, peroxynitrite etc. could react with the proteins, lipids, DNA and other cellular components causing destruction and ageing. One manifestation of ageing is the skin damage caused by UV light leading to skin or age spots.
Antioxidants come in all forms and guises like vitamins E and C as well as other non-vitamin compounds like Co enzyme Q10, to a host of polyphenols like quercetin found in apples and onions or resveratrol found in grapes, as well as some other compounds made within the cells of the body like glutathione and uric acid which is usually found circulating in the blood.
Classically, antioxidants are thought of as compounds that scavenge, quench or mop up the nasty free radicals, thus preventing their destructive nature. This however, is only one of the roles of antioxidant action.
Numerous researchers have studied the effects of consuming antioxidant-rich fruits, vegetables and nuts on the health of the population and have found a positive correlation. These epidemiological or population studies consistently confirm that the fruits and vegetables loaded with antioxidants reduce a host of diseases such as heart, circulatory, kidney, cataracts, arthritis and cancer to name a few.
These positive studies have resulted in the huge popularity of antioxidants as dietary supplements from capsules and tablets to creams and liquid beverages.
However, more recent research seems to challenge the view that free radicals are necessarily bad all the time. While the evidence supports the destructive nature of these free radicals, there is new and convincing evidence that these same radicals may actually be beneficial under certain conditions! How so you may ask?
The first point is that all antioxidants are a part of redox chemistry and as we all know, chemistry must be respected and all equations must be balanced. That is, antioxidants undergo simultaneous oxidation and reduction reactions. So for example, in order to perform their function, antioxidants will readily gain an oxygen atom or lose an electron and thus becoming oxidised in the process. The oxygen atom came from some place and likewise the electron has to go somewhere! The compound that supplied the oxygen atom and gained the electron originating from the antioxidant is reduced in the process. Of course the oxidized form can recycle back to its reduced and thus its original antioxidant form by losing an oxygen atom and/or gaining an electron. Thus antioxidants occur as both oxidised and reduced pair depending upon the environment they are in. These reactions are occurring continually.
The second point is that some antioxidants e.g. the flavonoids which are abundantly found in bright coloured fruits and vegetables and responsible in large part to their health benefits, once in the human digestive system quickly undergo the redox reaction and become oxidised or become pro-oxidant. This may even apply to certain vitamins like vitamin C and other endogenous antioxidants like glutathione. In other words, some antioxidants, once in the body, are in their oxidised form and perhaps that is how they are beneficial and not necessarily acting as antioxidants in the classical sense. Even pro-oxidants can have beneficial effects!
The third point is that free radicals themselves may not be bad as they have been portrayed. Free radical research has made rapid strides and researchers have made the startling discovery that neutralizing too many free radicals isn’t beneficial for the host. In fact it is a distinct disadvantage. It is a question of balance- not too high and not too low. Normally, free radicals may not be deleterious to our health and are readily dealt with or “mopped up” by our bodies, but under certain circumstances e.g. when there is excess production like cigarette smoke or ionizing radiation then damage may occur.
Vigorous exercise generates free radicals. If heavy doses of antioxidants (e.g. 1 gram of vitamin C and 400 iu of vitamin E) are taken immediately before or after, then the positive benefits of exercise are blocked! For example glucose isn’t taken up by muscle cells effectively. These results suggest that exercise generated free radicals have their own health benefits.
Here are some positive roles that free radicals may play:
- Free radicals act as signalling molecules whereby they can communicate with other players (e.g. white blood cells and messenger molecules like cytokines and chemokines etc.) and relay messages to and fro. This is important as the body relies on extensive channels of communication to deal with constant danger it faces.
- In lower concentrations free radicals are required for good “housekeeping” and ensuring that the body functions properly.
- Free radicals may actually come to our rescue especially during an attack by hostile invaders with which we are constantly exposed to. In fact, when our immune cells confront these bacteria, fungi and viruses they deliberately unleash free radicals of their own by a process called “oxidative burst” thereby overwhelming the invaders and destroying them in the process. That is why we use peroxide at the site of injury. Remember, if free radicals in excess can damage various parts of our cells, they can also destroy invaders by the same mechanism! In fact this is how free radicals help protect our bodies, by “neutralizing or scavenging” the microbes. One big advantage in using free radicals as a defense system is that the invaders are unlikely to develop any resistance to free radicals. In the 1980’s it was demonstrated by researchers that one of the mechanisms of action of antibiotics was through generation of free radicals. It seems that certain antibiotics actually mimic our immune cells by fighting-off infections by generating free radicals. More recently, pharmaceuticals have been developed that deliver free radicals under controlled conditions to the site of action in conditions like rheumatoid arthritis, ageing and other diseases with some success. This field is in its infancy but offers exciting possibilities. Think about it, free radicals used as a therapeutic option for disease treatment!
- Free radicals stimulate various genes e.g. Antioxidant Response Elements (ARE) to help switch off the production of important inflammatory players like NF-kappa B, TNF-alpha and switch on various helpful messenger molecules like chemokines and cytokines.
- Ironically, free radicals help switch on the production of antioxidants themselves like super oxide dismutase (SOD), catalase and glutathione peroxidase, enzymes that our cells use to maintain their healthy status.
When excess antioxidants are taken, free radical concentrations become dangerously low and this can cause detrimental health issues. Recent examples include selenium and diabetes and high concentrations of various antioxidants like green tea, curcumin and resveratrol having toxic effects in both test tube and in animals. Again more is not necessarily good for us.
What are the repercussions of this discovery? Many questions remain e.g. what is the ideal antioxidant dose to take? how do different antioxidants interact with one another when taken together? When to take the antioxidants? Should one take antioxidants at the beginning of an infection or later? Likewise when to take during a bout of inflammation? Remember, free radicals are being generated continually and, is taking one a day or twice a day antioxidant regimen effective? Should antioxidants be taken during radiation and/or chemotherapy? More research is needed.
It is likely that high doses of antioxidants may not be a good idea as we are likely to unbalance the fine-tuning of the redox chemistry and thus fail to take full advantage of antioxidants and free radicals themselves. Sorry Linus, we have to disagree with you on the mega supplementation. Balance is the name of the game!
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