The role of antioxidant nutrients in human health is now well established. A number of antioxidants are produced endogenously in humans, the most well known cellular antioxidant being the glutathione system. Cellular levels of glutathione are inversely associated with all cause mortality, and high cellular glutathione concentrations are increasingly being seen as essential to health. However, the antioxidant cellular defenses work in synergy (here) and in this regard a number of exogenous antioxidants are also pivotal for good health. These include vitamin C and vitamin E, as well as a number of plant derived secondary metabolites the biggest group of which are the polyphenols and carotenoids. These antioxidants are consumed in the diet, are bioavailable, and are now known to interact with each other in human cells and tissues, protecting them from oxidative stress. The health benefits of plant foods may to some extent come from their antioxidant nutrients.
A number of diseases such as cardiovascular disease and cancer are thought to involve oxidative stress in their aetiology. However, the number of diseases that are being shown to involve excessive free radical generation as part of their development is diverse. Hearing loss for example is a condition that may involve oxidative stress, as free radical generation has been discovered to play a role in the deterioration in function of the inner ear. Animal experiments have shown therapeutic effects on hearing loss with supplements of carotenoids, vitamin C and vitamin E, through reductions in free radical formation. Interestingly, animal studies also suggest that such antioxidant nutrients work synergistically with magnesium to protect the inner ear, although the mechanism is not fully understood. However, despite the positive studies in animals, few human studies have been performed and the effects of antioxidant nutrients and magnesium in human subjects is therefore not clear.
Some epidemiological studies have investigated the relationship between antioxidant intake, magnesium intake and hearing loss in humans. For example, in one study1, researchers examined the relationship between intakes of β-carotene, vitamin C and vitamin E as well as magnesium, on the hearing threshold in adults living in the United States of America. The subjects included in the study numbered 2592 and were between the ages of 20 and 69 years. The results of the study showed that after adjusting for known confounding variables, consumption of β-carotene, vitamin C and magnesium were associated with better pure tone averages (a behavioural test used to measure auditory sensitivity) both at normal speech and higher frequencies. When vitamin C or β-carotene were combined with magnesium, they resulted in a better pure tone average score at high frequencies, suggesting that magnesium plays a modulatory role in the effects of both vitamin C and β-carotene.
Dr Robert Barrington’s Nutritional Recommendation: This study suggests that high intakes of antioxidant nutrients and magnesium are associated with a reduced risk of hearing loss. Of course it is difficult to ascribe cause and effect in such an association, but the animal studies to date do support a role for antioxidants and magnesium as preventative factors in hearing loss. High quality diets based on traditional eating practices supply high amounts of phytochemicals including antioxidants to humans, and such diets are also rich in magnesium. The recommendation is therefore to eat a high quality diet in order to prevent deterioration of the auditory components of the inner ear.
RdB
