Review of Vitamin C
- What is Vitamin C?
- Who Should Consider Taking Vitamin C?
- Summary of Vitamin C's Physiological Effects
- Vitamin C Research
- Is Vitamin C effective?
- How to take Vitamin C
- Vitamin C References
Vitamin C is an anti-oxidant vitamin that has many essential roles within the body, including: 1) Proper immune function; 2) Production of collagen – keeps bones, ligaments, cartilage, skin and blood vessels strong; 3) production of anti-stress hormones; 4) Production of energy; 5) Protection against free radicals – molecules that cause great damage to cell structures such as DNA and proteins.
Researchers have found that people with low Vitamin C intakes are at greater risk of heart disease, certain cancers, and various infections.
Vitamin C is water soluble which means we cannot store it within our bodies. Also, we are unable to produce Vitamin C within our bodies, and therefore, it is vital for optimum health, that we consume adequate amounts of Vitamin C in our diets. Good sources of Vitamin C include: broccoli, peppers, kiwi fruit, oranges, tomatoes and other vegetables and fruit.
Since Vitamin C is vital for optimum health, supplementing additional Vitamin C may help to reduce the risk of infection, certain diseases, and improve general health.
- Reduced Risk of Infection and quicker recovery from colds
- appears to help stabilize blood sugar levels
- May help to control blood pressure
- Appears to Increase the number of "good" HDL cholesterol
- May reduce cortisol levels
- Appears to reduce cortisol levels
- May improve sperm fertility
- Appears to be non toxic and safe
Vitamin C supplementation has been shown to have many positive effects. A number of researchers have found that supplementing additional Vitamin C decreases the chances of getting respiratory infections like colds (Hemila and Douglas, 1999; Van Straten and Josling, 2002; Hemila, 2004). People who take Vitamin C supplements have been found to have significantly fewer colds, less than half the amount of total days with the virus, and a much shorter duration of severe symptoms (1.8 vs 3.1 days) (Van Straten and Josling, 2002). In some studies the incidence of common cold infections decreased by 91% following Vitamin C supplementation (Hemila, 2004). In fact, regular Vitamin C supplementation of 1g day, or more, has consistently reduced the duration of colds (Hemila and Douglas, 1999).
Research has also shown that Vitamin C supplementation may be beneficial to type II diabetes patients. In one study patients took no Vitamin C for the first week, then 1g/day for 4 weeks, followed by 3g/day for a further 4 weeks. The results showed that the mega dose of Vitamin C helped to control blood sugar levels and increased the patients anti-oxidant status (Park and lee, 2003).
A further benefit has been shown with its ability to help control blood pressure. When 500mg of Vitamin C was given daily to type II diabetes patients their systolic blood pressure dropped from 142 to 132 and their diastolic blood pressure dropped from 84 to 80mmHG (Mullan et al., 2002). Vitamin C may help to lower blood pressure by increasing the number of high density lipoproteins (HDL’s) which remove excess cholesterol from the walls of arteries. The same researchers also found that Vitamin C reduced arterial stiffness and therefore may be reducing artherosclerosis (hardening of the arteries).
Interestingly, Vitamin C may also help people to cope, physically better, with psychological stress (Brody et al., 2002). In this study healthy young adults were given 3x1000mg of vitamin C to consume each day for 14 days. They then under went the Trier Social Stress Test, which consists of public speaking and mental arithmetic. It was found that the subjects who consumed the Vitamin C had lower systolic blood pressure (an increase of 23 vs 31mmhg), less diastolic response, less subjective stress responses and a quicker rate of cortisol recovery.
Vitamin C may also help to protect non-smokers from the damaging effects of passive smoking. Researchers found daily Vitamin C supplementation decreased the level of oxidative stress in passive smokers (Dietrich et al., 2003). They concluded that Vitamin C may be important for the prevention of adverse health effects caused by passive smoking.
Vitamin C consumption may also be important for sports people. In weighlifters the consumption of 1000mg of Vitamin C, per day, for two weeks, reduced cortisol levels after the weighlifting session (Marsit et al., 1998). A number of studies have shown positive effects of lowering cortisol in endurance athletes (Nieman et al., 2000; Peters et al., 2001a; Peters et al., 2001b). The researchers demonstrated that higher intakes of Vitamin C (1500mg) were more beneficial than lower intakes (500mg) (Nieman et al., 2000; Peters et al., 2001b). However, lower doses were still beneficial. Peters et al., (2001a) found that the consumption of 2x500mg of vitamin C, daily, lowered cortisol by 30% post race. In fact just 200mg, twice daily, may be enough to reduce muscle soreness, and improve muscle function (Thomson et al., 2001). Cortisol causes a number of negative effects including: increased muscle breakdown, reduced muscle glycogen levels, and decreased immune function. Therefore by consuming additional Vitamin C on an ongoing basis you may reduce your risk of infection, decrease muscle breakdown and increase your rate of recovery.
Vitamin C supplementation (500-1000mg/day) has also been shown to reduce the amount of protein oxidation that occurs during exercise (Goldfarb et al., 2003). When combined with Vitamin E, it may be even more beneficial to sports persons. A combination of 500mg of Vitamin C and 1,200IU of Vitamin E was found to attenuate the drop in work rate, compared with the placebo group, during 300 maximal eccentric contractions (Shafat et al., 2004).
Some researchers have also found that Vitamin c may help to improve fertility by increasing sperm concentration, reducing the number of sperm clumped together, and reducing the number of abnormal sperm (Dawson et al., 1992; Sonmet et al., 2005).
Vitamin C consumption appears to be safe with few adverse effects when consumed up to 2000mg/day (Hathcock et al., 2005). At high doses (>2-3g/day) some individuals may experience gastrointestinal upset and diarrhea.
A number of studies appear to demonstrate that vitamin c can help to reduce the risk of infection, speed recovery from colds, and protect against oxidative damage.
For general health benefits consume 100-500mg per day in 2-3 divided doses. To reduce the risk of infection research suggests you should consume 1000-1500mg in 2-3 divided doses. To aid recovery from exercise consume 500-1000mg in 2-3 divided doses.
Brody, S., Preut, R., Schommer, K. and Schurmeyer, T. H. (2002) A randomised controlled trial of high dose ascorbic acid for reduction of blood pressure, cortisol, and subjective responses to psychological stress. Psychopharmacology (Berl). 159 (3), 319-324.
Dawson, E. B., Harris, W. A., Teter, M. C. and Powell, L. C. (1992) Effect of ascorbic acid supplementation on the sperm quality of smokers. Fertil Steril. 58, 1034-1039.
Dietrich, M., Block, G., Bnowitz, N. L., Morrow, J. D., Hudes, M., Jacob, P. 3rd., Norkus, E. P. and Packer, L. (2003) Vitamin C supplementation decreases oxidative stress biomaker f2-isoprostanes in plasma nonsmokers exposed to environmental tobacco smoke. Nutr Cancer. 45 (2), 176-184.
Goldfarb, A. H., Patrick, S. W., Bryer, S. and You, T. (2005) Vitamin C supplementation affects oxidative stress blood markers in response to a 30-minute run at 75% VO2max. Int J Sport Nutr Exerc Metab. 15 (3), 279-290.
Hathcock, J. N., Azzi, A., Blumberg, J., Bray, T., Dickinson, A., Frei, B., Jialal, I., Johnston, C. S., Kelly, F. J., Kraemer, K., Packer, L., Parthasarathy, S., Sies, H. and Traber, M. G. (2005) Vitamins E and C are safe across a broad range of intakes. Am J Clin Nutr. 81 (4), 736-745.
Hemila, H. (2004) Vitamin C supplementation and respiratory infections: a systematic review. Mil Med. 169 (11), 920-925.
Hemilla, H. and Douglas, R. M. (1999) Vitamin C and acute respiratory infections. Int J Tuberc Lung Dis. 3 (9), 756-761.
Hemilla, H. (1994) Does vitamin C alleviate the symptoms of the common cold?—a review of current evidence. Scandanavian Journal of Infectious Diseases. 26, 1-6.
Kelly, G. (2003) The interaction of Cigarette Smoking and Antioxidants. Part III:Ascorbic Acid. Alt Med Rev. 8 (1), 43-54.
Marsit, J. L., Conley, M. S., Stone, M. H., Fleck, S. J., Kearney, J. T., Schirmer, G. P., Keith, R. E., Kraemer, W. J. and Johnson, R. L. (1998) Effects of ascorbic acid on serum cortisol and the testosterone:cortisol ratio in junior elite weightlifters. J of Strength Cond Res. 12, 179-184.
Mullan, B. A., Young, I. S., Fee, H. and McCance, D. R. (2002) Ascorbic acid reduces blood pressure and arterial stiffness in type 2 diabetes. Hypertension. 40 (6), 804-809.
Nieman, D. C., Peters, E. M., Hensen, D. A. Nevines, E. I., Thompson, M. M. (2000) Influence of vitamin C supplementation on cytokine changes following an ultramarathon. J Interferon Cytokine Res. 20 (11), 1029-1035.
Park, H. S. and Lee, Y. M. (2003) Effects of vitamin C supplementation on blood sugar and antioxidative status in types II diabetes mellitus patients. Taehan Kanho Hakhoe Chi. 33 (2), 170-178.
Peters, E. M., Andersen, R., Nieman, D. C., Fickl, H. and Jogessar, V. (2001) Vitamin C supplementation attenuates the increase in circulating cortisol, adrenaline and anti-inflammatory polypeptides following ultramarathon running. Int J Sports Medicine. 22 (7), 537-543.
Peters E. M., Andersen, R. and Theron, A. J. (2001) Attenuation of increase in circulating cortisol and enhancement of the acute phase protein response in vitamin C-supplemented ultramarathoners. Int J Sports Med. 22 (2), 120-126.
Robson, P. J., Bouic, P. J. and Myburgh, K. H. (2003) Antioxidant supplementation enhances neutrophil oxidative burst in trained runners following prolonged exercise. Int J Sport Nutr Exerc Metab. 13 (3), 369-381.
Shafat, A., Butler, P., Jensen, R. L. and Donnelly, A. E. (2004) Effects of dietary supplementation with vitamins C and E on muscle function during and after eccentric contractions in humans. Eur J Appl Physiol. 93 (1-2), 196-202.
Sonmez, M., Turk, G. and Yuce, A. (2005) The effect of ascorbic acid supplementation on sperm quality, lipid peroxidation and testosterone levels of male Wister rats. Theriogenology. 63 (7), 2063-2072.
Thompson, D., Williams, C., McGregor, S. J., Nicholas, C. W., McArdle, F., Jackson, M. J. and Powell, J. R. (2001) prolonged vitamin C supplementation and recovery from demanding exercise. Int J Sport Nutr Exerc Metab. 11 (4), 466-481.
Van Straten, M. and Josling, P. (2002) Preventing the common cold with vitamin C supplement: a double-blind placebo-controlled survey. Adv Ther. 19 (3), 151-159.