Antioxidants – Do they matter? - NZ Nutrition Foundation

Article by Dr. Laurence Eyres, 2010

Antioxidants can be compared to vitamins. They are micronutrients required in addition to the basic macronutrients – fats, proteins and carbohydrates.

These days there is a great deal of talk about the necessity of having sufficient antioxidants in our diet to combat free radicals occurring in the atmosphere around us. This is the so-called free radical theory of disease, which is a plausible hypothesis but has no real scientific evidence to back it up. According to this theory, active free radicals which can come from a variety of sources such as pollution, smoking and alcohol, lead to lipid free radicals in the body which cause the breakdown of essential fatty acids and DNA. Numerous researchers have found no evidence to support this theory. And no disease has ever been linked directly to this free radical theory of disease. But it would not be totally fair to debunk this simplistic hypothesis; perhaps it just needs putting in perspective. There is no doubt free radicals play both a beneficial and possibly harmful role in our health but the exact mechanisms have yet to be fully determined.

There are certain antioxidants that have been studied extensively and do seem to have some therapeutic powers. The majority of studies, based on epidemiological evidence, support the theory that the Mediterranean diet leads to good health and prevents a number of the Western ailments.

The basis of the Mediterranean diet not only includes minimising meat and dairy products but also promotes the inclusion of many vegetables and fruits, with fish and olive oil being key essential ingredients. There is growing evidence extra virgin olive oil relies on its high concentration of natural antioxidants such as the polyphenols for its health-giving properties rather than its fatty acid composition. That is why one should use extra virgin olive oil rather than the “pure” or “light” oil which is fully refined, bleached, deodorised and contains virtually none of the natural antioxidants.

Classical antioxidants include phenolic compounds such as naturally-occurring tocopherols (vitamin E) and vitamin C, but also include the commonly-used synthetic antioxidants, BHT BHA and TBHQ. The latter three have, in recent years, come under a cloud for no other reason than the fact they are synthetic.

There is a problem when doing clinical trials based on antioxidants that are pure compounds acting on their own. When people carry out work on tocopherols, they generally focus on synthetic DL-alpha tocopherol, whereas in its natural form, vitamin E exists as a mixture of eight isomers. Clinical trials have also been carried out on beta-carotene with negative results. Again, the substance used was synthetic, all trans, 100% pure beta-carotene. Whereas. in nature, carotenoids occur as mixtures of isomers. Until recently scientists believed each antioxidant acted separately in the body independently of the others; we now know this is untrue. There is a dynamic interplay among certain key antioxidants sometimes referred to as the ‘antioxidant network’. There are literally hundreds of antioxidants in our food and dietary supplements yet only five appear to be ‘network antioxidants’. These include vitamins C and E, glutathione, lipoic acid and coenzyme Q10.

A deficiency of antioxidants has been blamed for such diseases as macular degeneration, Alzheimer’s disease, coronary heart disease, arthritis and many other inflammatory diseases. However, statins, drugs used in the treatment of coronary heart disease, are actually powerful antioxidants. Also, new Australian results from the Centre for Eye Research have shown people who consume at least 100ml extra virgin olive oil per week are almost 50% less likely to develop macular degeneration than those who consume less than 1ml per week.

Examples of foods containing key antioxidants:

Extra virgin olive oil, green tea, coffee, red wine, cocoa, krill, blueberries, brassica and many others.

NB selenium a trace mineral, it is a key co-factor for glutathione peroxidase enzyme so is an essential antioxidant synergist.

Some conclusions and thoughts

The classical lipid free radical antioxidant theory does not really apply to the micro levels of so-called antioxidants we eat in our food.
The term ‘antioxidants’ has become so loosely defined as to be almost unusable. By the traditional chemical definition, an antioxidant is a molecule that slows the free radical chain reaction propagating the oxidation of lipids. In a biological context, the critical use of the term ‘antioxidant’ should include molecules that protect cells from damage. Biological antioxidants may well be termed self-defence agents, and include repair systems such as IM transport proteins, antioxidant enzymes and factors affecting vascular homoeostasis. Some of the biological antioxidant activity attributed to various plant extracts and flavonoids has little to do with antioxidant activity.
More research will be needed in the future to determine the precise mode of action of so-called antioxidants.
It may be that the whole spectrum of antioxidants needs to be consumed in a food matrix rather than a pure synthetic or extracted component. Exceptions to this approach may be where it is shown people are deficient in certain so-called antioxidants, such as coenzyme Q10 or vitamin E, or in the case of New Zealanders, selenium. A sensible approach is to balance our basic diet with essential dietary supplements and the occasional pharmacological agent.

Overall, I believe there is good agreement that antioxidants play a major role in health and well-being.