Quick Hit Summary

Due to its antioxidant capabilities, one would naturally assume that vitamin C would protect against the development of heart disease and cancer. However, there is no current evidence to suggest that doses greater than the current RDA value (75-125 mg/d depending on demographics) reduces the incidences of these diseases. With respect to the common cold, the prophylactic use of vitamin C does not seem to reduce the incidence of development. A possible exception to this rule may be for those completing heavy physical labor. One study revealed that individuals receiving vitamin C were 50% less likely to develop a cold than those receiving a placebo. More research is still needed on this latter finding. I recommend taking supplemental vitamin C only as part of a balanced multi vitamin-mineral supplement. The remainder of your vitamin C intake should come from a variety of fruits and vegetables.

Antioxidants

Figure 1. Per serving, few things pack as much vitamin C as an orange.³⁵

Previously, we discussed what antioxidants were and how they function in the body in the article, Understanding Antioxidants, Free Radicals and Oxidative Damage. In addition, we’ve examined the potential ergogenic role of vitamin C in the article Dietary Antioxidants: Vitamin C & Athletic Performance/Recovery. In this article I’d like to discuss vitamin C and its potential role in chronic disease prevention and other health issues.

Vitamin C & Cardiovascular Disease

Prospective Epidemiological Studies

Prospective cohort studies have produced somewhat mixed results regarding vitamin C intakes and cardiovascular disease (CVD). Knekt et al, noted that vitamin C intakes 85mg/day vs. <60mg/day decreased the risk of coronary artery disease mortality by 51% in more than 2300 Finnish Women¹². Pandey et al. followed >1500 middle aged men for an average of 20+ years¹³. Upon reviewing the relationship between vitamin C and coronary artery disease (CAD) related death, Pandey et al found that those consuming >113 mg vs.<82 mg of vitamin C/day decreased CAD related deaths by 25%.

On the other hand, other studies have found no relationship between vitamin C intake and heart disease. In the Rotterdam Study, investigators examined the relationship between dietary vitamin C and myocardial infarction (MI) was examined in 1856 men and 2946 women (mean ages: 67-68 years old)¹⁴. Each individual was followed for an average of four years (11). At the end of the study, the same risk for MI was reported between those with higher (>170 mg/d) and lower (<63 mg/d) dietary intakes of vitamin C. Similar negative results have been reported in other trials as well¹⁵¹⁶. One possible explanation as to why conflicting results have been shown in prospective trials may be attributed to circulating plasma levels of vitamin C. Nyyssönen et al., suggested that vitamin C supplementation decreased coronary heart disease (CHD) only in those already deficient (defined as plasma concentration <2.0mg/l) in this vitamin¹⁷. In their study, involving 1605 healthy middle aged men, vitamin C concentrations < 2.0 mg/l were associated with a 250% increased risk for CHD. However, regardless of vitamin C concentrations above this level, the risk of CHD was not significantly different. In other words, plasma concentrations of 5.0 mg/l were no more protective than concentrations of 3.0 mg/l. According to Carr & Frei, , the average healthy individual should consume 90-100mg/day in order to ensure these levels are met¹⁸. In healthy males, 100mg/day has been shown to saturate vitamin C levels in various cells of the immune system¹⁹.

A Quick Aside on Cholesterol

One of the strongest risk factors associated with CVD is serum (blood) cholesterol. With respect to heart disease, earlier research in general focused on total cholesterol. However, as of late, research has shown that HDL and LDL cholesterol are stronger risk factors for CVD²⁰. HDL cholesterol is often characterized as the “good” cholesterol as it’s been shown to be protective against atherosclerosis. In contrast, LDL cholesterol gets trapped in the arterial walls. In the process it often suffers oxidative damage, leading to the formation of plaque. HDL cholesterol prevents this by scavenging LDL’s and removing them from circulation in a process referred to as reverse cholesterol transport²¹. Besides scavenging LDL cholesterol, in vitro studies have also shown HDL’s to inhibit factors associated with blood clot formation, as well as modulate the functions of the endothelial cells which line the inside of arteries²². Although somewhat controversial, elevated triglyceride levels also appear to be a risk factor for CHD²³.

Clinical Controlled Trials

Numerous clinical controlled trials have examined whether or not vitamin C can influence serum cholesterol levels. In a recently completed meta-analysis, McRae investigated the impact that vitamin C supplementation had on HDL, LDL and triglyceride levels²⁴. His meta-analysis included 13 previously conducted clinical controlled trials. Amongst other inclusion criteria, studies had to be 3-24 weeks in length (3 weeks is required for vitamin C to reach steady state in plasma following supplementation), participants had to be hypercholesterolemic at baseline and a minimum dose of 500 mg vitamin C/day was to be administered. Although results indicated that vitamin it had no significant effect on HDL levels, vitamin C did have a modest effect at lowering LDL cholesterol (−7.9 mg/dL) and triglycerides (−20.1 mg/dL) levels. For reference, below are the American Heart Association’s blood lipid (cholesterol, etc) levels associated with cardiovascular disease²⁵.

Total Cholesterol

• Desirable: <200
• Boderline/High Risk: 200-239
• High Risk: >240

HDL Cholesterol- Considered “good”, want higher levels

Men:

• Low- <40 mg/dL
• Average- 40-50 mg/dL
• High- >60 mg/dL

Women:

• Low- <50 mg/dL
• Average- 50-60 mg/dL
• High- .60mg/dL

LDL Cholesterol- Considered “bad”, want lower levels

• Optimal: <100 mg/dL
• Near/Above Optimal:130-159 mg/dL
• Borderline High: 160-189 mg/dL
• High: 190 mg/dL and above

Triglyceride Levels- higher levels are considered harmful

• Normal: less than 150 mg/dL
• Borderline-High: 150–199 mg/dL
• High: 200–499 mg/dL
• Very High: 500 mg/dL

Vitamin C & Cancer

Each day, DNA is bombarded with thousands of free radicals per day. In fact, some have hypothesized that it occurs at a rate of ~ 10^4 oxidative hits/cell/day²⁶. Thus, with its ability to deactivate free radicals in the plasma and regenerate vitamin E, many researchers have investigated whether or not vitamin C can prevent cancer.

Prospective Epidemiology Studies

Prospective cohort studies appear to indicate that the protective effect of vitamin C on cancer is maximized at 90-100 mg/day¹⁸. Beyond this intake level, one does not seem to receive any additional benefit with respect to cancer prevention. For instance, Sahyoun et al. followed 680 men and women (mean ages, 72 & 73 respectively) for 10 years²⁷. At the end of the study, there was no significant difference for all types of cancer amongst those consuming >388 mg/day vs. <90mg/day of vitamin C. In a larger scale study involving a much younger population (89,494 women; age spread- 30 to 55 years old), Hunter et al. examined the effects of vitamin C on prevention of breast cancer²⁸. Over the course of 8 years, it was found that no significant difference in rates of breast cancer were found between participants receiving >359 mg/day vs. <93 mg/day of vitamin C. On the other hand, instances were significant differences in cancer risk were present, participants in the lowest grouping (ie-quintile) of vitamin C consumption were consuming less than 90 mg/day. Pandey et al. followed 1556 middle aged men for 24 years¹³. With respect to vitamin C intake, consuming >113 mg/day decreased all cancer risk by 40% vs. participants receiving <82 mg/day.

Clinical Control Trials

There have been few large scale clinical control trials that have examined whether or not vitamin C can prevent the onset of cancer. In a recently published study by Gaziano et al., 14,641 male physicians were distributed into groups that received vitamin E with placebo, vitamin C with a placebo, a combination of vitamin E & C, or 2 placebo pills²⁹. 400 IU of vitamin E (or its placebo version) were taken every other day and 500 mg of vitamin C (or its placebo version) were consumed every day. The physicians were instructed not to consume any multivitamin containing >100% DV of vitamins A, C, E or beta-carotene. After 10 years, it was found that all groups had the same risk for developing lung, colorectal, prostrate, lung and total cancer (ie- all other types of cancers combined). See Table 1.

Table 1 Incidences of cancer in amongst the participants in Gaziano et al.’s study. Please note that despite absolute differences being found, the differences were not statistically significant²⁹.

Supplement Group	Total Cancer	Prostrate Cancer	Colon Cancer	Lung Cancer
Placebo	479	245	45	42
Vitamin E	491	255	42	31
Vitamin C	480	270	42	23
Vitamin E & C	493	238	33	27

In a somewhat similarly designed study, Lin et al. provided various antioxidant supplements that contained vitamin C (500 mg/day), vitamin E (600 IU every other day), beta-carotene (50 mg every other day) or a placebo to 8171 women (mean age 60 years old) over the course of 10 year³⁰. Upon completion of the study, it was found that regardless of what supplement they took, the risk for total cancer incidence and cancer mortality were the same.

A few caveats should be mentioned with the studies. These studies were both 10 years in length and included individuals who were well nourished. It may be that vitamin C (or E) may show a beneficial effect in clinical trials of longer duration or in populations with inadequate vitamin C intakes.

Vitamin C & The Common Cold/Upper Respiratory Track Infections

Besides possibly scurvy, the first health benefit that most laypersons attribute to vitamin C is protection against upper respiratory track infections (ie-common cold). In an extremely large scale meta-analysis, Douglas et al. statistically summarized all clinical controlled studies regarding the use of vitamin C to prevent and treat the common cold³¹. In studying the prevention of the common cold, they combined the results of 30 clinical controlled studies which included a total of 11,350 participants. They found that consistently consuming >200 mg or more of vitamin C did not significantly decrease the incidence of the common cold. Although long term supplementation of vitamin C in doses >200 mg does not prevent the common cold, this amount was found to slightly decrease the duration of the cold by 8% in adults and 13.5% in children. This comes out to about 1 day decrease of cold duration for every 10 days that a cold would normally last. However, it should be noted that if individuals started consuming vitamin C at the onset of cold symptoms, no difference in duration was present except in one study.

There appears to be one group of individuals who benefit from vitamin C supplementation with respect to the common cold. In the aforementioned meta-analysis conducted by Douglas et al., vitamin C supplementation was found to decrease the incidence of the common cold in a small subset of individuals completing heavy physical labor³¹. This subset included 6 studies consisting of 251 marathon runners, 279 students in an Alpine Swiss ski school, and 112 Canadian soldiers completing “subarctic winter exercises.” In comparison to those receiving a placebo, it was found that vitamin C supplementation >200 mg decreased incidence of upper respiratory track infection by 50%.

Daily Intake & Sources

The current RDA for vitamin C in adults is 90 mg (men) and 75 mg (women)³². For smokers, this value increases up to 125 mg (men) and 110 (women). As seen in Table 2 there are many sources of vitamin C that can be obtained in the diet.

*Table 2*Food sources of vitamin C³³³⁴. As a side note, the DV for vitamin C is currently outdated. It’s based off the 1968 RDA value (60 mg) rather than the current ones mentioned above [33].

Food	mg per serving	% Daily Value
Orange, 1 whole	98	163
Strawberries, 1c	94	156
Red Peppers, ¼ c	71	118
Kiwi Fruit, 1 whole	57	95
Lemon raw sections, ½ c	56.2	94
Green Pepper rings, 5	45	75
Broccoli, raw ½ c	41	68
Grapefruit, raw ½ c	38.4	64
Cantaloupe, ½ c	29	49
Cauliflower, raw ½ c	23	39
Sweet Potato, 1 whole	17	28
Baked Potato, 1 medium	16	27
Raspberries, ½ c	16	27
Butternut Squash, ½ c	15	25
Pineapple Chunks, ½ c	12	20
Tomato, ½ c	11.4	19

This list is by no means close to being complete. To search for the vitamin C content of a particular type of food not listed above, CLICK HERE.

Bottom Line

According to current research, vitamin C, in amounts > 90-110 mg/day, does not appear to reduce the risk of developing CVD or cancer. However, doses of 500 mg may provide small benefits to those with elevated blood lipid (cholesterol, etc) profiles. Studies also suggest that large doses of vitamin C will not prevent upper respiratory track infections. On the other hand, if taking > 200mg daily prior to the onset of a cold, it may slightly decrease the duration of the cold by 8-13% (ie- 1 day for a 10 day cold)³¹.

During times when one’s exercise/physical exercise is extremely ramped up, vitamin C intake of 200-400 mg/day may provide short term performance benefits and/or decrease the risk of catching a cold. Keep in mind that studies have not consistently shown these beneficial effects. Despite this potential benefit, I do not feel that mega-doses (> 1 g/day) of vitamin C supplements are warranted as they may increase oxidative damage following a workout.

As I’ve mentioned in previous articles, I recommend taking a multivitamin which contains 100% of the daily value (DV) for vitamin C. Additionally, one should eat multiple servings of fruits and vegetables to meet their vitamin C needs.

References

¹³ Pandey DK, Shekelle R, Selwyn BJ, Tangney C, Stamler J. Dietary vitamin C and b-carotene and risk of death in middle-aged men. Am J Epidemiol 1995;142:1269–78.

¹⁴ Klipstein-Grobusch K, Geleijnse JM, den Breeijen JH, Boeing H, Hofman A, Grobbee DE, Witteman JC. Dietary antioxidants and risk of myocardial infarction in the elderly: the Rotterdam Study. Am J Clin Nutr. 1999 Feb;69(2):261-6.

¹⁵ Rimm EB, Stampfer MJ, Asherio A, Giovannucci E, Colditz GA, Willett WC. Vitamin E consumption and the risk of coronary heart disease in men. N Engl J Med 1993;328:1450–6.

¹⁶ Kushi LH, Folsom AR, Prineas RJ, Mink PJ, Wu Y, Bostick RM.Dietary antioxidant vitamins and death from coronary heart disease in postmenopausal women. N Engl J Med 1996;334:1156–62.

¹⁷ Nyyssönen K, Parviainen MT, Salonen R, Tuomilehto J, Salonen JT. Vitamin C deficiency and risk of myocardial infarction: prospective population study of men from eastern Finland. BMJ. 1997 Mar 1;314(7081):634-8.

¹⁸ Carr AC, Frei B. Toward a new recommended dietary allowance for vitamin C based on antioxidant and health effects in humans. Am J Clin Nutr. 1999 Jun;69(6):1086-107.

¹⁹ Levine M, Conry-Cantilena C, Wang Y, et al. Vitamin C pharmacokinetics in healthy volunteers: evidence for a recommended dietary allowance. Proc Natl Acad Sci U S A 1996;93:3704–9.

²⁰ Boden WE.High-density lipoprotein cholesterol as an independent risk factor in cardiovascular disease: assessing the data from Framingham to the Veterans Affairs High—Density Lipoprotein Intervention Trial. Am J Cardiol. 2000 Dec 21;86(12A):19L-22L.

²¹ Schmitz G, Grandl M.The molecular mechanisms of HDL and associated vesicular trafficking mechanisms to mediate cellular lipid homeostasis. Arterioscler Thromb Vasc Biol. 2009 Nov;29(11):1718-22.

²² Nofer JR, Kehrel B, Fobker M, Levkau B, Assmann G, von Eckardstein A. HDL and arteriosclerosis: beyond reverse cholesterol transport. Atherosclerosis. 2002 Mar;161(1):1-16.

²³ Jeppesen J, Hein HO, Suadicani P, Gyntelberg F. Triglyceride concentration and ischemic heart disease: an eight-year followup in the Copenhagen Male Study. Circulation 1998;97(11):1029-36.

²⁴ McRae MP. Vitamin C supplementation lowers serum low-density lipoprotein cholesterol and triglycerides: a meta-analysis of 13 randomized controlled trials.J Chiropr Med.2008 Jun;7(2):48-58.

²⁵ American Heart Association. What Your Cholesterol Levels Mean. July 2009. Accessed November 8, 2009 from: http://www.americanheart.org/presenter.jhtml?identifier=183.

²⁶ Woodall AA, Ames BN. Diet and oxidative damage to DNA: the importance of ascorbate as an antioxidant. In: Packer L, Fuchs J, eds. Vitamin C in health and disease. New York: Marcel DekkerInc, 1997:193–203.

²⁷ Sahyoun NR, Jacques PF, Russell RM. Carotenoids, vitamins C and E, and mortality in an elderly population. Am J Epidemiol 1996;144:501–11.

²⁸ Hunter DJ, Manson JE, Colditz GA, et al. A prospective study of the intake of vitamins C, E, and A and the risk of breast cancer.N Engl J Med 1993;329:234–40.

²⁹ Gaziano JM, Glynn RJ, Christen WG, Kurth T, Belanger C, MacFadyen J, Bubes V, Manson JE, Sesso HD, Buring JE. Vitamins E and C in the prevention of prostate and total cancer in men: the Physicians’ Health Study II randomized controlled trial. JAMA. 2009 Jan 7;301(1):52-62. Epub 2008 Dec 9.

³⁰ Lin J, Cook NR, Albert C, Zaharris E, Gaziano JM, Van Denburgh M, Buring JE, Manson JE. Vitamins C and E and beta carotene supplementation and cancer risk: a randomized controlled trial. J Natl Cancer Inst. 2009 Jan 7;101(1):14-23. Epub 2008 Dec 30.

³¹ Douglas RM, Hemilä H, Chalker E, Treacy B. Vitamin C for preventing and treating the common cold. Cochrane Database Syst Rev. 2007 Jul 18;(3):CD000980.

³² Institute of Medicine. Food and Nutrition Board. Dietary Reference Intakes: Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press, 2000.

³³ Wardlaw GM, Hampl JS, and DiSilvestro RA. Perspectives in Nutrition. 6th edition. McGraw-Hill Companies.2004. Print.

³⁴ Fruits and Veggies More Matters. Fruit and Vegetable Nutrient Database. Produce for Better Health Foundation.2009. Accessed November 10, 2009 from: http://www.fruitsandveggiesmorematters.org/?page_id=164.

³⁵ Accessed June 14, 2010 from: http://en.wikipedia.org/wiki/File:Ambersweet_oranges.jpg