By Paige Oliver
Humans, along with guinea pigs and fruit bats, cannot make vitamin C, also known as ascorbic acid (AA); therefore we must consume it in our diet. Vitamin C plays an important role in many body processes such as neurotransmitter synthesis, the synthesis of collagen, which is a structural protein in skin, tendons, bone and cartilage, and the synthesis of carnitine, which is important in fat metabolism (1,2).
Vitamin C is also known for its antioxidant function (i.e. it is a reducing agent). It not only protects cells in the body from free radicals and reactive oxygen species, but it can also help regenerate other important antioxidants like vitamin E and glutathione (1-3). The current recommendation of vitamin C is even 35mg/day higher for smokers than for nonsmokers due to the increased oxidative stress cigarettes cause, making it the only nutrient with an additional requirement for smokers (1,2).
However, because vitamin C is easily oxidized, processed foods are often not fortified with vitamin C, and the vitamin C content of foods – even fresh fruits and vegetables – can be affected by oxygen, heat, light, processing and storage times (1,3,4). If you do not consume fresh produce quickly, you may benefit from purchasing frozen fruits and vegetables because they are better protected against oxidation. In fact, the closer an opened carton of ready-to-drink juice is to its expiration date, the less vitamin C it may contain. It may contain up to 60% less vitamin C than what the label claims simply because it has been stored too long or been exposed to one of the other factors that affect vitamin C content (4,5).
Diets high in vitamin C are associated with a lower risk for heart disease and certain cancers. While the exact mechanisms by which this occurs are not completely understood, increased intake of fruits and vegetables (along with the effects of their non-nutritive components and vitamin C) may offer a protective effect against certain diseases (1-3,4).
Good sources of vitamin C include: 1 medium orange (70mg), 1 cup strawberries (85mg), ½ cup chopped green pepper (60mg) and 1 cup raw cauliflower (45mg) (1,2).
Individuals with a history of kidney stones, hemochromatosis or thalassemia should talk with their doctor or dietitian before consuming high amounts of vitamin C (2).
References:
- Oregon State University: Linus Pauling Institute. Micronutrient Information Center: vitamin C. Available at http://lpi.oregonstate.edu/infocenter/vitamins/vitaminC/. Accessed March 21, 2012.
- Gropper SS, Smith JL, Groff JL. Advanced Nutrition and Human Metabolism. 5th Ed. Belmont: Wadsworth; 2009.
- Food and Nutrition Board, Institute of Medicine. DRI Report – Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press; 2000.
- Burdurlu HS, Koca N, Karadeniz F. Degradation of vitamin C in citrus juice concentrates during storage. J Food Eng. 2006;74:211-216.
- Johnston CS, Bowling DL. Stability of ascorbic acid in commercially available orange juices. J Acad Nutr Diet. 2002;102(4):525-529.
