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Vitamin C is a water-soluble vitamin that is used in many tissues throughout the body. The adrenal gland contains the highest concentration of vitamin C, and the vitamin plays a crucial role in both the adrenal cortex and adrenal medulla [1]. Humans are one of the few species that cannot manufacture the vitamin in the body and must depend on diet or nutritional supplementation as a source of vitamin C. The best sources of vitamin C are fresh fruit (especially in the citrus family, including oranges, lemons, limes and tangerines), strawberries, cantaloupe and currants. Green leafy vegetables, including Brussel sprouts, collard greens, lettuce, cabbage, peas and asparagus, are also good sources.

During the early days of sea exploration, European sailors were often afflicted with scurvy. Private firms would supply a ship’s crew with food for long voyages. These firms charged a flat rate, so the cheaper the food supplied, the more money a firm would make. Common sailors were given salt fish, salt beef and rye crackers, all of which lack vitamin C. The officers got a few extras including potatoes, which contain vitamin C and protected them against scurvy. Sailors from other parts of the world didn’t get scurvy because they ate foods containing vitamin C. The Vikings ate sauerkraut and the Chinese ate bean sprouts, both of which are high in vitamin C. The name chemical name for vitamin C, ascorbic acid, is derived from a-, meaning without, and scorbuticus, meaning scurvy.

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Vitamin B is a complex of eight water soluble vitamins active in cell metabolism. They include Thiamine (vitamin B1), Riboflavin (vitamin B2, also called vitamin G), Niacin (vitamin B3, also called vitamin P), Pantothenic acid (vitamin B5), Pyridoxine and Pyridoxamine (vitamin B6), Biotin (vitamin B7, also called vitamin H), Folic acid (vitamin B9, also called vitamin M) and Cyanocobalamin (vitamin B12).

Note: This review is not meant to be a comprehensive or definitive glossary, but rather to identify each vitamin’s function and highlight recent research findings of each of the B vitamins.

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Vitamin A consists of a group of compounds that play an important role in vision, bone growth, reproduction, cell division and cell differentiation [1]. It helps to regulate the immune system and may also help lymphocytes (meaning a type of white blood cell) better fight infection [2]. In general, there are two forms of vitamin A:

• Vitamin A found in foods that come from animals is called preformed vitamin A and is absorbed in the form of retinol, the most biologically active form of vitamin A.
• Vitamin A found in plants is called provitamin A carotenoid, which can be made into retinol in the body.

Vitamin A deficiency can lead to eye problems including dryness of the cornea and night blindness. Vitamin A plays an important role in maintaining the integrity of epithelial cells (the cell type that line hollow organs and glands and that make up the outer surface of the body). Consistent with this role, the incidence of diseases of the respiratory tract is increased during moderate vitamin A deficiency [3]. Vitamin A deficiency has been associated with an increased risk of various epithelial cancers, including skin, lungs, stomach and breast cancer) [4]. Additionally, an isomer (meaning a molecule with the same chemical formula but different structure) of retinol, all-trans-retinoic acid, has been shown to help cancer patients with metastatic renal cell carcinoma [5]. As vitamin A is essential for the growth of bones, teeth and soft tissues, a deficiency of vitamin A can contribute to bone loss associated with osteoporosis [6].

Carotenoids are highly colored fat-soluable organic pigments that are naturally occurring in photosynthetic organisms. Common provitamin A carotenoids, which are also unoxidized carotenoids, such as alpha-carotene, beta-carotene and lycopene, are known as carotenes. In photosynthetic organisms, carotenoids participate in the energy transfer process or protect against auto-oxidation. In animals, carotenoids have been linked to oxidation-preventing mechanisms and are efficient free-radical scavengers, functioning as antioxidants.

References

1. Gerster H. Vitamin A–functions, dietary requirements and safety in humans. Int J Vitam Nutr Res. 1997;67(2):71-90.
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2. Semba RD. The role of vitamin A and related retinoids in immune function. Nutr Rev. 1998 Jan;56(1 Pt 2):S38-48.
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3. Biesalski and Nohr. Importance of vitamin-A for lung function and development. Mol Aspects Med. 2003 Dec;24(6):431-40.
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4. Basu TK. Vitamin A and Cancer of Epithelial Origin. J Hum Nutr. 1979 Feb;33(1):24-31.
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5. Mirza et al. All-trans-retinoic acid improves differentiation of myeloid cells and immune response in cancer patients. Cancer Res. 2006 Sep 15;66(18):9299-307.
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6. Advani and Wimalawansa. Bones and nutrition: common sense supplementation for osteoporosis. Curr Womens Health Rep. 2003 Jun;3(3):187-92.
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