Articles > Vitamin C Benefits

Cancer

Carr, C. and Frei, B., “Toward a new recommended dietary allowance of vitamin C based on antioxidant and health effects in humans”, American Journal of Clinical Nutrition, 1999, Vol. 69, pp. 1086-1107

“A multitude of epidemiologic studies have shown that increased consumption of fresh fruit and vegetables is associated with a reduced risk of most types of cancer. Fruit and vegetables contain many constituents that may contribute to protection against cancer, including antioxidant vitamins. … Kromhout et al reported a significant 64% risk reduction of lung cancer with vitamin C intakes > 83 mg/d. … Pandley et al observed a significant 39% lower risk of all cancers in men consuming > 113 mg of vitamin C/d than those consuming, 82 mg/d. A vitamin C intake > 50 mg/d from the diet plus regular supplements, totaling approximately 300 mg/d, was found to be associated with a moderate 21% risk reduction of all cancers in men compared with a dietary intake of < 49 mg/d, although no significant effect was observed in women.”

Weber, P., Bendich, A., and Schalch, W., “Vitamin C and Human Health – A Review of Recent Data Relevant to Human Requirements”, International Journal of Vitamin and Nutritional Research, 1996, Vol. 66, pp. 19-30

“In a comprehensive review of vitamin C and cancer risk, Block found “extremely strong and consistent” evidence of a protective effect against cancers of the stomach, esophagus, oral cavity, and pharynx: 17 of 19 studies showed statistically significant associations between low intake of dietary vitamin C and increased risk of cancer at these sites. … A recent study by Kune et al compared 41 men from Melbourne, Australia with oral or pharyngeal cancer to 398 male controls. This study found a significant risk reduction of oral/pharyngeal cancer of 79% in the patients having a vitamin C intake of > 106 mg/day with no further risk reduction in the patients with vitamin C intake of > 201 mg/day. In an area of China with a high rate of stomach cancer, serum levels of vitamin C were assayed out of a population of 3,433 subjects. Histological diagnosis was made employing a gastric mucosa tissue sample as collected by gatroscopy. Subjects with low vitamin C serum levels had a 50% higher risk for gastric metaplasia, which is considered to be a pre-cancerous lesion. … A recently published study on gastric cancer and micronutrients conducted during 1988 and 1989 in Barcelona, Spain found that subjects in the uppermost quartile of dietary vitamin C intake showed a statistically significant gastric cancer risk reduction of 69%. Finally, a Swedish study pointed out that vitamin C intake in the highest quartile vs. the lowest quartile 20 years prior to cancer manifestations was significantly associated with reduction in the risk of gastric cancer.”

Cardiovascular Disease

J.T. Salonen; K. Nyyssönen, R. Salonen; H.-M. Lakka, J. Kaikkonen; E. Porkkala-Sarathaho; S. Voutilainen; T. A. Lakka; T. Rissanen; L. Leskinen; T.-P. Tuomainen; V.-P. Valkonen; U. Ristonmaa; and H.E. Poulsen, "Antioxidant Supplementation in Atherosclerosis Prevention (ASAP) study: a randomized trial of the effect of vitamin E and C on 3-year progression of carotid atherosclerosis", Journal of Internal Medicine, 2000, Vol. 248, pp. 377-386

“OBJECTIVES: To study the efficacy of vitamin E and C supplementation on the progression of carotid atherosclerosis, hypothesizing an enhanced preventive effect in men and in smokers and synergism between vitamins. DESIGN AND SUBJECTS: Double-masked two-by-two factorial trial, randomization in four strata (by gender and smoking status) to receive twice daily either 91 mg (136 IU) of d-alpha-tocopherol, 250 mg of slow-release vitamin C, a combination of these or placebo for three years. A randomized sample of 520 smoking and nonsmoking men and postmenopausal women aged 45-69 years with serum cholesterol >/= 5.0 mmol L-1 were studied. SETTING: The population of the city of Kuopio in Eastern Finland. INTERVENTION: Twice daily either a special formulation of 91 mg of d-alpha-tocopherol, 250 mg of slow-release vitamin C, a combination of these (CellaVie(R)) or placebo for three years. MEASUREMENTS: Atherosclerotic progression, defined as the linear regression slope of ultrasonographically assessed common carotid artery mean intima-media thickness (IMT), was calculated over semi-annual assessments. RESULTS: The average increase of the mean IMT was 0.020 mm year-1 amongst men randomized to placebo and 0.018 mm year-1 in vitamin E, 0.017 mm year-1 in vitamin C and 0.011 mm year-1 in the vitamin combination group (P = 0.008 for E + C vs. placebo). The respective means in women were 0.016, 0.015, 0.017 and 0.016 mm year-1. The proportion of men with progression was reduced by 74% (95% CI 36-89%, P = 0.003) by supplementation with the formulation containing both vitamins, as compared with placebo. CONCLUSIONS: Our study shows that a combined supplementation with reasonable doses of both vitamin E and slow-release vitamin C can retard the progression of common carotid atherosclerosis in men. This may imply benefits with regard to other atherosclerosis-based events.”

“Vitamin E and vitamin C are considered two of the most important dietary antioxidants. Vitamin E may also have other anti-atherogenic properties. When vitamin E works as an antioxidant it is oxidized to harmful a-tocopheroxoyl radicals, which need to be reduced back to a-tocopherol. Vitamin C can regenerate harmful a-tocopheroxoyl radical to a-tocopherol. Theoretically, supplementing high-risk individuals with high doses of vitamin E alone could even promote rather than reduce lipid peroxidation. Also, in our prospective population study, vitamin C deficiency was associated with increased risk of coronary events. For these reasons we designed a randomized clinical trial in which not only vitamin E but also vitamin C was supplemented.”

“The doses of the supplements were chosen to keep the plasma ratio of vitamin C and E concentrations similar to that of unsupplemented persons. This was tested in pilot and kinetic studies. The pilot studies also established that a reasonably constant plasma level of vitamin C was achieved by the dosing of one slow-release tablet in the morning and another in the evening.”

“The covariate-adjusted IMT increase was 50.9% less (0.009 vs. 0.018 mm year-1) in men who received both vitamins E and C, compared with other men (P = 0.044) and 45.0% less (0.011 vs. 0.020 mm year-1) compared with the placebo men (P = 0.049). Differences between other supplementation groups were not statistically significant. The treatment effect of the vitamin C + E combination was larger amongst smoking men than non-smoking men. In smoking men, the covariate-adjusted IMT increase was reduced by 64% and in nonsmoking men, by 30%. None of the treatment effects were significant in women.”

“In men, the proportion of those who experienced progression was reduced by 74% (95% CI 36-89%, P = 0.003) in the group randomized to receive both vitamins, as compared with those who received only placebo. The respective treatment effect was nonsignificant in groups that received only vitamin E or vitamin C, although there were trends towards protection.”

“The present findings are the first demonstration in a population-based study of an atherosclerotic disease preventing effect of supplementation with antioxidant vitamins. Our study suggests that the benefit may be limited to men, and possibly to men who are at increased oxidative stress such as smokers or those who have insufficient status of dietary or endogenous antioxidants. The observed effect modification by gender and smoking status needs to be retested in further clinical trials.”

“The progression rate in smoking men who received vitamin E and C supplements was lower than in nonsmoking men receiving placebo. Thus, in this study the preventive effect of the supplementation was at least equal to the atherosclerosis promoting effect of smoking. This is not a trivial effect from the public health point of view.”

“The vitamins E and C supplements were safe. There were neither excess death nor excess other adverse events in the groups randomized to supplements, although the sample size was not designed to detect effects on either deaths or other disease events. Both the adherence to treatment and the bioavailability of the supplements were good, judged based on increases of plasma vitamin levels. The drop-out rate during the trial was exceptionally low.”

“In conclusion, our study shows that a formulation providing combined supplementation with reasonable doses of both vitamin E and slow-release vitamin C for at least three years can retard the progression of common carotid atherosclerosis substantially in regular smoking men. However, this study does not provide evidence for any substantial preventive effect in postmenopausal women, although a small benefit cannot be ruled out. As common carotid plaques and increased intimal-media thickness have been shown to predict coronary events, this observation may imply benefits with regard to atherosclerosis-related events.”

Carr, C. and Frei, B., “Toward a new recommended dietary allowance of vitamin C based on antioxidant and health effects in humans”, American Journal of Clinical Nutrition, 1999, Vol. 69, pp. 1086-1107

“Enstrom et al showed a risk reduction in cardiovascular disease of 42% in men and 25% in women consuming > 50 mg vitamin C/d from the diet plus regular supplements, corresponding to approximately 300 mg total vitamin C/d. An earlier study b Enstrom et al indicated that intakes of vitamin C > 250 mg/d were not associated with an additional risk reduction for cardiovascular disease, although subsequent reanalysis of the data indicated that intakes > 750 mg/d were associated with a reduction in overall mortality. Sahyoun et al reported a significant 62% lower risk of cardiovascular disease in a population of elderly men and women consuming > 388 mg vitamin C/d than in those consuming < 90 mg/d.”

Weber, P., Bendich, A., and Schalch, W., “Vitamin C and Human Health – A Review of Recent Data Relevant to Human Requirements”, International Journal of Vitamin and Nutritional Research, 1996, Vol. 66, pp. 19-30

“In an analysis of data from the U.S. First National Health and Nutrition Examination Survey (NHANES I) and its 10-year follow-up study, Enstrom et al found strong inverse relationships between vitamin C intake and all-cause mortality and cardiovascular mortality especially in men. This study included more than 11,000 people and assessed vitamin C intake form both diet and supplementation. At the highest level of vitamin C consumption (> 50 mg/day from diet plus regular use of supplements), men had an almost 50% lower rate of death from cardiovascular disease and women had a 35% lower rate.”

Cataract

Carr, C. and Frei, B., “Toward a new recommended dietary allowance of vitamin C based on antioxidant and health effects in humans”, American Journal of Clinical Nutrition, 1999, Vol. 69, pp. 1086-1107

“Several epidemiological studies have investigated the association of vitamin C intake with the incidence of cataract. Two case-controlled studies indicated a strong inverse association between high intakes of vitamin C and cataract. Robertson et al found that intakes of >300 mg vitamin C/d were associated with a 70% reduced risk of cataract. Similarly, Jacques and Chlack found that daily intakes of >490 mg were associated with a 75% lower risk of cataract than intakes <125 mg/d. … Two studies, one of them involving > 50,000 women, indicated that vitamin C has a positive effect on cataract risk when supplements were taken for > 10 y; risk reductions of 45% and 77-83% were reported.”

Weber, P., Bendich, A., and Schalch, W., “Vitamin C and Human Health – A Review of Recent Data Relevant to Human Requirements”, International Journal of Vitamin and Nutritional Research, 1996, Vol. 66, pp. 19-30

“In a smaller U.S. study (77 cases, 35 controls), low intake of vitamin C was associated with a statistically significant 11-fold increase in the risk of posterior subcapsular cataracts. Also, low vitamin C intake was associated with a 3.7-fold increase in risk of cortical cataracts. It is noteworthy that in this study, "low" intakes were defined as less than 125.3 mg per day (the 20th percentile cut-off in this population). This, in the study an intake of twice the RDA of vitamin C was considered the "low" intake group, and substantially higher intakes were associated with reduced risk of cataracts.”

Deficiency

Hampl J., PhD, RD, Taylor C., and Johnston C., PhD, RN, FACN, "Intakes of Vitamin C, Vegetables and Fruits: Which Schoolchildren Are at Risk?" Journal of the American College of Nutrition, 1999, Vol. 18, No. 6, pp. 582-590

“Our analyses revealed that a considerable number of children had low intakes of vitamin C. Among the seven to twelve-year-olds, 12% of boys and 13% of girls had mean vitamin C intakes that were less than 30 mg/day. Among 13 to 18-year-olds, 14% of boys and 20% of girls consumed less than 30 mg/day vitamin C. An even greater proportion of children had marginal vitamin C intakes. For both age groups, 21% of boys and 27% of girls daily consumed between 30 mg and 60 mg of vitamin C.”

Johnston, C., PhD, RD and Corte C., "People with marginal vitamin C status are high risk of developing vitamin C deficiency", Journal of the American Dietetic Association, July 1999, Vol. 99, No. 7, pp. 854-856

“The Recommended Daily Allowance (RDA) for vitamin C is 60 mg/day, an amount associated with plasma vitamin C concentrations ranging from 28 to 34 µmol/L. Plasma vitamin C concentrations ranging from 11 µmol/L to less than 28 µmol/L represent marginal vitamin C status, which Jacob defines as a moderate risk of developing vitamin C deficiency due to low tissue stores. Plasma vitamin C concentrations less than 11 µmol/L are indicative of vitamin C deficiency. The average daily intake of vitamin C in men in the United States is about twice the RDA, yet the prevalence of vitamin C deficiency and marginal vitamin C status in men is 13% and 24% respectively. Women consume an average of 90 mg vitamin C daily, and the prevalence of vitamin C deficiency and marginal vitamin C status in women is 9% and 18%, respectively. These data indicate that although the average vitamin C indicate in adult men and women is adequate, vitamin C deficiency and marginal vitamin C status are strikingly prevalent in these populations.”

Johnston, C. PhD, FACN and Thompson L., MS, "Vitamin C Status of an Outpatient Population", Journal of the American College of Nutrition, 1998, Vol. 17, No. 4, pp. 366-370

“Modern societies with year-round access to fresh fruits and vegetables, most of which are rich sources of vitamin C, seldom develop scurvy, and the disease is usually considered in a historical context. However, examination of the recent medical literature suggests that scurvy continues to be observed in developed nations. … The number of these recent case reports is surprising, and little research has been conducted to determine the prevalence of vitamin C deficiency in the US population. This study showed that vitamin C deficiency was present at surprisingly high rates among generally healthy patients visiting a health care facility for routine health exams, gynecological exams, and pregnancy exams. … the present study demonstrated that vitamin C depletion and vitamin C deficiency was evident in an outpatient population (prevalence rates, 30.4% and 6.3%, respectively). Symptoms associated with vitamin C deficiency are subtle but physiologically relevant.”

Shapiro, L. PhD, Samuels, S. PhD, Breslow L., MD, PhD, and Camacho T., MA, "Patterns of Vitamin C Intake from Food and Supplements: Survey of an Adult Population in Alameda County, California", The American Journal of Public Health, July 1983, Vol. 73, No. 7, pp. 773-778

“Fourteen per cent of respondents appeared to have no regular source of vitamin C. This group includes persons who reported that they did not have at least two servings of fruit or vegetables almost every day, had none of the specified juices on an average day, and did not take vitamin C pills each day. Because of possible underreporting, 14 per cent is probably too high an estimate of persons who had inadequate vitamin C. However, there is cause for concern if any segment of the population lacks a regular source of vitamin C sufficient to meet nutritional needs.”

Fertility

Weber, P., Bendich, A., and Schalch, W., “Vitamin C and Human Health – A Review of Recent Data Relevant to Human Requirements”, International Journal of Vitamin and Nutritional Research, 1996, Vol. 66, pp. 19-30

“A recently published review concluded that vitamin C appears to improve human fertility by various mechanisms. The result of controlled human studies also support a possible role of vitamin C in human fertility. Fraga et al have demonstrated that dietary vitamin C protects human sperm against endogenous oxidative DNA damage. A placebo-controlled study in 75 smokers found a significant dose-dependent improvement of six sperm qualities after 4 weeks of daily supplementation with vitamin C. Sperm quality increased in the 200-mg group by 15% and in the 1,000 group by 40%.”

Immunity

Weber, P., Bendich, A., and Schalch, W., “Vitamin C and Human Health – A Review of Recent Data Relevant to Human Requirements”, International Journal of Vitamin and Nutritional Research, 1996, Vol. 66, pp. 19-30

“Vitamin C supplementation has been shown to reduce the severity of symptoms associated with the common cold. In people who experience extreme physical stress, vitamin C may be of benefit in preventing respiratory infections. A double-blind trial conducted in South Africa showed that marathon runner consuming 1 g vitamin C per day had a significantly lower rate of post-race respiratory infection as compared to those consuming 500 mg/day. … In HANES II serum vitamin C levels were negatively associated with chronic bronchitis indicating that vitamin C intake might be of value in subjects with chronic respiratory problems.”

Shapiro, L. PhD, Samuels, S. PhD, Breslow L., MD, PhD, and Camacho T., MA, "Patterns of Vitamin C Intake from Food and Supplements: Survey of an Adult Population in Alameda County, California", The American Journal of Public Health, July 1983, Vol. 73, No. 7, pp. 773-778

“Pauling's claim for preventative and therapeutic benefits of large doses of vitamin C was challenged in a double blind study, from which an unexpected finding emerged, namely, that disability from all types of acute illness was 30 per cent lower in subjects who received 1000 mg of vitamin C daily than in those that received placebos. A subsequent double blind study led to the conclusion that a large therapeutic dose of vitamin C at the time of acute illness may help diminish disability from acute infection.”

Mortality

Kay-Tee Khaw; Sheila Bingham; Ailsa Welch; Robert Luben; Nicholas Wareham; Suzy Oakes; and Nicholas Day, "Relation between plasma ascorbic acid and mortality in men and women in EPIC-Norfolk prospective study: a prospective population study", The Lancet, 2001, Vol. 357, pp. 657-663

“Methods - We prospectively examined for 4 years the relation between plasma ascorbic acid concentrations and mortality due to all causes, and to cardiovascular disease, ischaemic heart disease, and cancer in 19,496 men and women aged 45-79 years.”

“Findings - Plasma ascorbic acid concentration was inversely related to mortality from all-causes, and from cardiovascular disease, and ischaemic heart disease in men and women. Risk of mortality in the top ascorbic acid quintile was about half the risk in the lowest quintile (p<0.0001). The relation with mortality was continuous through the whole distribution of ascorbic acid concentrations. 20 µmol/L rise in plasma ascorbic acid concentration, equivalent to about 50 g per day increase fruit and vegetable intake, was associated with about a 20% reduction in risk of all-causes mortality (p<0.0001), independent of age, systolic blood pressure, blood cholesterol, cigarette smoking habit, diabetes, and supplement use. Ascorbic acid was inversely related to cancer mortality in men but not for women.”

“Interpretation - Small increases in fruit and vegetable intake of about one serving daily has encouraging prospects for possible prevention of disease.”

“Ascorbic acid (vitamin C) plays a part in many biological processes, including free radical scavenging, collagen and hormone synthesis, haemostatis, and protection of lipid membranes which might affect chronic disease risk.”

“In this cohort, plasma ascorbic acid was specifically related to fruit and vegetable intake, and an increase in 20 µmol/L plasma ascorbic acid concentration was associated with an increase of about 50 g daily or one serving of fruit and vegetables. A change from the second to fourth quintile (eg, 30th-70th percentile), was associated with 30% reduction in mortality risk, which suggests that small and feasible shifts within the normal population intake could have a substantial effect on mortality risk. Plasma ascorbic acid might indicate the intake of such foods that are rich in other nutrients such as potassium, folate, calcium, magnesium, non-starch polysaccharides, isoflavonoids, and others that might confer health benefits.”

Periodontal Health

Weber, P., Bendich, A., and Schalch, W., “Vitamin C and Human Health – A Review of Recent Data Relevant to Human Requirements”, International Journal of Vitamin and Nutritional Research, 1996, Vol. 66, pp. 19-30

“Legott et al assessed periodontal status in 11 nonsmoking healthy men following controlled intake of different levels of vitamin C (5 mg, 60 mg, 600 mg per day). They reported that the number of bleeding sites and the gingival inflammation index was inversely related to vitamin C intake levels.”

Stroke

Weber, P., Bendich, A., and Schalch, W., “Vitamin C and Human Health – A Review of Recent Data Relevant to Human Requirements”, International Journal of Vitamin and Nutritional Research, 1996, Vol. 66, pp. 19-30

“In another recently published study of a 20 year follow-up cohort of randomly selected 730 male and female elderly people living in different areas of Britian, those in the highest tertile of vitamin C intake, which was > 44.9 mg per day, had a 50% lower risk of experiencing a stroke.”

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