Humans need a number of vitamins in their body to survive. A group of the vitamins needed for vitality include the fat soluble vitamins, which includes vitamins A, D, E, and K. Deficiency in these vitamins is rare, but rather, over consumption is the problem often associated with these vitamins.
Fat soluble vitamins are vitamins that are stored in fatty tissues and in the liver. These vitamins, unlike water soluble vitamins, are stored for long periods of time in the body. As a result, consuming too many of the fat soluble vitamins can lead to toxicity problems throughout the body. According to Seager and Slabaugh, authors of Chemistry for Today: General, Organic, and Biochemistry, "Some vitamins (A, D, E, and K) have very nonpolar molecular structures and therefore dissolve only in nonpolar structures" (690). Thus, lipids in the body are the solvents, classifying the vitamins as fat soluble.
Vitamin A plays an essential role in eyesight and allowing the eyes to adjust to light changes. According to an article in Newsweek, "Some studies find that diets high in carotenoids (which form vitamin A) reduce the risk of cataracts" (1). Vitamin A also maintains moisture of the lungs, throat, mouth, and nose. People often consume Vitamin A in foods such as carrots, butter, and egg yolk. Toxicity is more of a problem in the United States than deficiency due to overuse of multivitamins. Symptoms of overuse, or toxicity, includes irritability and blurred vision, among many other things. In the rare case of a deficiency in this vitamin, scaly skin and night blindness often occurs (Anderson 1).
Vitamin D is often associated with calcium. It allows formation of bones and teeth, regulation of calcium and phosphorus, and plays a role in keeping bones and teeth strong in the elderly years. Vitamin D is consumed through many dairy foods, oily fish, and direct sunlight. Vitamin D deficiencies, like Vitamin A, are uncommon...