Antioxidants and Exercise

Given the complexity of the human body it would be unwise to simply say that reactive oxygen species (ROS) are bad and antioxidants are good.  Metabolic by-products of muscle contractions, ROS cause lipid peroxidation and damage the protein machinery of cells, yet they have emerged as also being part of a complex biochemical signaling network in skeletal muscles.   Research such as Ristow et al. (2009) suggests that such species are necessary for exercise-induced adaptations since they are prevented by high doses of antioxidants.  Muscle function adaptations include contractile protein expression, angiogenesis and mitochondrial biogenesis, as well as increased insulin sensitivity which is one of the most clinically relevant effects of exercise.  The biochemical signaling pathways which are activated by exercise have also been shown to up-regulate antioxidant defence enzymes, such as superoxide dismutase, which defend against ROS.

Clinical trials of antioxidant supplements in disease prevention have generally been disappointing.  Whilst normal doses of antioxidants from the diet are required to support the defence system, Bouayed and Bohn (2010) suggest that adverse effects may result from the high doses that tend to be used in studies, by interfering with the crucial role that low levels of ROS has in many physiological functions.  Also such high doses of single antioxidant compounds may be toxic under certain conditions where other compounds that act in synergy are lacking, such as may be the case with the increased risk of lung cancers among smokers who take beta-carotene supplements.  It would interesting to see whether this increased risk is still there if beta-carotene is complemented by a range of other phytonutrients which could act in synergy.


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