Understanding antioxidants and substantiating claims

However, in the 18th Century no one knew what caused scurvy, a disease which had so many symptoms that it was frequently mistaken for asthma, leprosy, syphilis, dysentery and madness. And while physicians speculated as to its cause, people became aware that once victims of scurvy were on shore, they could be cured by eating scurvy grass, wild celery, wood sorrel, nasturtiums, brooklime, Kerguelen cabbage, cabbage trees and fruit and palm wine. In 1753, with the publication of James Lind’s Treatise of the Scurvy (recording, perhaps, the first controlled trial ever), there was experimental evidence that citrus had a beneficial effect on prevention of diseases such as scurvy.1 While these claims to cure, and later prevent scurvy, could not then be substantiated by knowledge of underlying biochemical mechanisms, the value of these anecdotal observations were certainly worthy of consideration. What is now essential in making claims is that they should be based on acceptable and reproducible experimental evidence and not on suppositions, hopes or expectations. Among the few words that have migrated from the laboratory to the high street is “antioxidant”. Just about everyone seems to be familiar with the word. Nutraceuticals, functional foods, cosmetics, cosmeceuticals and a whole range of personal care products may include the antioxidant word in their promotion and antioxidant materials in their substance. Manufacturers of these products, aware of the current and growing interest in antioxidants, should now be prepared to substantiate, whenever possible, any claims they make for their product from the results of rigorous analysis. And when ethical considerations and practical constraints make it impossible to carry out the otherwise desirable clinical trials, advertisers should not imply they have done so. If you say something is “clinically proven”, you will be expected to have carried out clinical trials, designed rigorously to knock down your hypothesis, not designed to prove it. If a complaint should be made to the Advertising Standards Authority, you will be required to provide results of any testing carried out before you made the claim. The message is “be clear and honest, and your customers will have confidence in your products”. Whether or not a product can transfer antioxidant activity to the user is, of course, a very important consideration. However, before a product can be tested for efficacy, it must itself have first been tested for antioxidant content. And if the product is irradiated or treated in any other way to conform to safety requirements, the antioxidant testing must be carried out on the treated product. Irradiation can lead to generation of free radicals, and these are likely to attack the antioxidants in the product.2 Knowing that a product contains ingredients with recognised antioxidant activity is not good enough. It is at least prudent, if not essential, to measure the antioxidant activity of individual ingredients in a formulation in order to assess whether there is any positive or negative synergy between ingredients. This information is extremely useful in optimising the formulation and it could save considerable expense. More is not necessarily better!3 It is also essential to know the stability of the antioxidants during storage and use in order to recommend dosage and frequency of application.

What are antioxidants?

The term antioxidant comprises a variety of substances and includes enzymes that neutralise potentially damaging reactive species. Most of these reactive species contain oxygen.4 Some, but not all of these “reactive oxygen species” (ROS) are free radicals: that is molecules with an excess of negative charge.3 While free radicals and other non-radical ROS are produced by the body and play an essential part in the body’s biochemistry, an excess of them can have dire effects. Antioxidants can neutralise this excess if active and in sufficient amounts at the site of ROS production. However, when ROS production gets out of control, oxidative stress occurs.5 When this happens, these reactive chemical species can injure or even kill cells, damage DNA and attack enzymes and other compounds.