Give Two Examples of Adaptation

Study under review: Vitamin C and E supplementation prevents some of the cellular adaptations to endurance-training in humans

Introduction

Antioxidants are substances that protect cells from oxidizing chemicals, such as free radicals. High levels of free radicals, particularly from dietary sources and pollution, cause cellular damage and may contribute to cancer^[1], heart disease^[2], and other disorders. However, low to moderate levels of free radicals are produced^[3] by moderate to intense physical exercise and can help cells to adapt to increased physical stress, as shown in Figure 1. On the other end of the scale, overtraining without the appropriate physical adaptations can overwhelm^[4] the body's ability to respond to the high levels of free radicals produced, and can damage the body in similar ways to other sources of free radicals. Vitamins A, C, and E are the primary dietary antioxidants.

Figure 1: How ROS may help muscle endurance and antioxidants may hinder it

Over 40% of the general population^[5] and over 50% of elite athletes^[6] in endurance sports take multivitamins and other dietary supplements. Due to the prevalence of supplements, particularly vitamins C and E, the question has been raised as to whether these supplements have a negative effect on endurance training and the mechanisms through which the body adapts to the cellular stress of endurance training. As previously mentioned, the body responds to the moderate levels of free radical production produced by endurance training by adapting at the cellular level. Over time^[7], the body can sustain higher and higher levels of free radical production because it improves muscular function and increases its natural antioxidant responses. Thus, it's possible that taking antioxidant supplements could neutralize the free radicals produced by the body in response to exercise, thus hindering the body's ability to adapt to progressively higher levels of free radicals.

Most previous research attempting to investigate the role of vitamin C and E supplementation has focused on endurance training alone by testing participants before and after the endurance training period. The study under review was designed to examine not only endurance training, but also the effects on an acute exercise session before and after the endurance training protocol. The hypothesis is that some long-term cellular adaptations to training are partly due to the effects of transient responses immediately following an exercise session. Several previous studies also assessed a lower dose of 500 milligrams a day of vitamin C, whereas this study looked at a higher dose of 1000 milligrams a day.

Common dietary antioxidants include vitamins C and E, which help neutralize free radical molecules in the body. They are supplemented by a large portion of the population, including more than half of endurance athletes. Because it is believed that free radicals contribute to the training adaptation resulting from endurance training, researchers hypothesized that antioxidant supplementation might reduce this adaptive response.

Who and what was studied?

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