In our efforts to reduce the risk of heart disease, regular exercise plays an important part in maintaining a healthy lifestyle. The increased delivery of oxygen-rich blood to tissues is a vital part of the process—but it can also produce destructive free radicals. Clearly, the solution is not to stop exercising! Rather, a series of recent studies shows how supplementation with vitamin C can mitigate free-radical damage from intense exercise.
British researchers evaluated the effects of just two weeks of modest vitamin C supplementation (200 mg twice daily) on the recovery from an unaccustomed bout of exercise. Eight healthy men were given either a placebo or vitamin C supplementation each day, and after 14 days performed a 90-minute-long running test. The supplemented group had less muscle soreness, better muscle function, and lower blood levels of the oxidative stress-induced molecule malondialdehyde. And although both groups experienced post-exercise elevations in levels of the inflammatory cytokine interleukin-6, increases in the supplemented group were smaller than in the placebo recipients. The scientists concluded that “prolonged vitamin C supplementation has some modest beneficial effects on recovery from unaccustomed exercise.” Timing is critical, however. When the researchers repeated their study with subjects who took vitamin C only after exercise, no benefit was seen.
Oxidative stress during exercise induces significant changes in proteins, producing compounds known as protein carbonyls. Measuring levels of protein carbonyls is therefore a useful indicator of oxidation. Exercise scientists at the University of North Carolina studied the impact of vitamin C supplementation (500 or 1,000 mg/day for two weeks) compared with placebo on oxidative stress indicators in 12 healthy men. As expected, exercise acutely reduced total blood levels of antioxidants in both groups. Levels of protein carbonyls increased by nearly four-fold in the placebo group, while vitamin C recipients experienced little or no elevation. This vital study demonstrates that vitamin C can protect against exercise-induced protein oxidation in a dose-dependent fashion.
Muscle soreness after exercising can be a big disincentive to continue on a healthy fitness program. That’s why the subsequent findings of that UNC group are so important. The scientists gave vitamin C supplements (3,000 mg/day) or placebo to a group of 18 healthy men for two weeks before and four days after performing 70 repetitions of an elbow extension exercise. Not surprisingly, considerable muscle soreness ensued, but it was significantly reduced in the supplemented group. The release of creatine kinase, an indicator of muscle damage, was also attenuated with vitamin C, compared with the placebo group. Blood levels of natural antioxidants fell significantly in placebo subjects, while vitamin C supplementation completely prevented this change. Results such as these suggest that the supplemented group would be much more enthusiastic about exercising the next day!
Minimizing Unhealthy Lifestyle Choices
Vitamin C may offer important protective benefits for smokers and those who are passively exposed to tobacco smoke. Smoking has been linked with elevated levels of C-reactive (CRP) protein, an inflammatory marker linked with an elevated risk of cardiovascular disease. As Life Extension readers know, it is crucial to monitor your CRP levels through regular blood testing and to keep your CRP under control in order to limit cardiovascular problems. Fortunately, vitamin C has been shown to play a role in helping to combat excessive CRP levels.
Researchers in Berkeley evaluated the impact of antioxidant supplementation on blood levels of CRP in both active and passive smokers. They studied 160 healthy adults who were actively or passively exposed to cigarette smoke and randomly assigned to receive placebo, vitamin C (515 mg/day), or an antioxidant mixture (including vitamins C, E, and lipoic acid). Subjects in the vitamin C group underwent a significant 24% reduction in their plasma CRP concentrations, while neither of the other groups showed a significant change. This remarkable result provides strong support for chronic supplementation with vitamin C, whether or not you smoke.
Smoking causes cancer in part by directly damaging DNA, which is a vital first step in the onset of cancer. In studying the effect of vitamin C supplements on reducing DNA damage in blood cells, Danish researchers gave relatively low doses (500 mg/day) of vitamin C as plain-release or slow-release tablets combined with vitamin E (182 mg/day), or placebo, for four weeks to a group of male smokers. The slow-release formulation of vitamin C reduced the number of DNA damage sites measured in white blood cells just four and eight hours after a single tablet, a positive result that was still evident at four weeks. The plain-release tablets also exerted a protective effect at four hours, suggesting benefits of long-term vitamin C supplementation in minimizing DNA damage.
Once DNA is damaged, however, smoking induces pro-inflammatory changes that can allow a malignant cell to become a dangerous tumor as well as causing blood vessel damage associated with atherosclerosis. Vitamin C supplementation is a logical approach to reducing the impact of these inflammatory changes, as was shown recently by a British investigative team.15 They studied 10 smokers with the high-risk lipoprotein ApoE4 gene as well as 11 non-smokers, all of whom took just 60 mg/day of vitamin C for four weeks. Remarkably, these high-risk smokers on this low-dose regimen responded with a marked reduction in levels of a host of pro-inflammatory cytokines. As the authors themselves pointed out, this study identified core molecular mechanisms that help explain the known benefits of vitamin C supplementation in smokers.
Literally scores of other studies have been published demonstrating the benefits of vitamin C supplements in smokers and those passively exposed to cigarette smoke. One study found that 500 mg of vitamin C twice daily for just two weeks reduced the depletion of vitamin E caused by smoking by up to 50%.
Two other studies investigating low and high doses of vitamin C supplementation revealed its benefits in improving endothelial function, a cornerstone of cardiovascular health, known to be impaired in smokers. The first study showed that just 60 mg of vitamin C daily given to a group of smokers for 12 weeks improved endothelial function as assessed by flow-mediated vasodilation. In the second study, Dutch researchers found that 2,000 mg/day of vitamin C for two weeks reversed endothelial dysfunction caused by the abnormal migration of monocytes7 implicated in atherosclerosis.
Furthermore, Berkeley public health researchers successfully reduced levels of F2-isoprostanes, a sign of oxidative stress and cell damage, in a group of 67 passive smokers who were given vitamin C supplements daily for two months. The researchers stressed the value of these findings in preventing tobacco smoke-induced health damage in non-smokers.
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