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.” however. When the researchers repeated their study with subjects who took vitamin C only after exercise, no benefit was seen.
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. 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. They studied 10 smokers with the high-risk lipoprotein 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 monocytes 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.
Nutritional researchers are constantly uncovering new health benefits for vitamin C. Recent findings include vitamin C’s role in the following applications:
Respiratory illnesses: The impact of vitamin C in staving off the common cold has been hotly debated for more than three decades. Large, well-designed studies continue to show, however, that regular vitamin C supplements reduce the frequency and duration of the common cold. More serious illnesses also benefit from the antioxidant effects of vitamin C, particularly asthma. Asthmatic children given an antioxidant supplement containing 250 mg vitamin C and 50 mg vitamin E had markedly decreased responses to environmental asthma triggers. And vitamin C supplements (1,000 mg/day) also reduced the amount of long-term inhaled corticosteroids needed by adults with asthma.
Cancer: Exciting new work is showing that vitamin C supplementation may decrease the toxic effects of chemotherapy drugs (such as damage to heart tissue) and increase the anti-tumor activity of chemotherapy. Further, promising studies show that vitamin C may synergize with other antioxidant and anti-inflammatory nutraceuticals to help fight cancer. Chronic supplementation with vitamin C and other antioxidants might also serve a vital chemopreventive role, reducing the risk of actually developing cancer in the first place.
Diabetes: Human studies have now demonstrated that vitamin C supplements may help lower blood glucose levels in diabetics, with additional beneficial reductions in low-density lipoprotein (LDL) and plasma free radicals.
Stomach Health: Supplementing with vitamin C can also protect against oxidative damage wrought by the bacterium Helicobacter pylori, a major cause of gastritis and stomach ulcers. Vitamin C supplements can also reduce the dose of antibiotics needed to eradicate the organism, and may directly prevent the gastritis it causes. And there’s encouraging evidence that higher vitamin C levels are associated with lower long-term gastric cancer risk.
Supplementing with Vitamin C
The recommended intake to prevent overt vitamin C deficiency is 90 mg/day for men and 75 mg/day for women who do not smoke; for smokers, 125 mg/day for men and 110 mg/day for women are recommended. Clinical studies suggest that the amount of vitamin C required for optimal health is at least 400 mg/day, with some studies suggesting doses as high as several thousand milligrams daily. Many health practitioners recommend supplementing with at least 1,000 mg of vitamin C daily.
While vitamin C is generally considered safe and well-tolerated, a few words of caution most by applied. Individuals who have certain hematologic disorders such as thalassemia, anemia, or glucose-6-phosphate deficiency should consult a physician before supplementing with vitamin C, as should pregnant or nursing women.
Modern science is now eagerly embracing vitamin C’s enormous potential as an antioxidant capable of preventing and, in some cases, reversing a host of human ills. Helping to maximize the beneficial effects of exercise while minimizing the impact of destructive toxins like tobacco smoke, vitamin C also acts at the most fundamental levels to prevent endothelial changes that lead to atherosclerosis, while also blocking harmful DNA degradation that triggers malignant change and sets the stage for cancer. And as scientists learn still more about the vital role of oxidative damage in diseases ranging from asthma to stomach ailments, vitamin C’s importance is growing literally by the day. There is no doubt that future research will uncover even more astonishing findings on the health benefits of vitamins.