Vitamins are one of the most important nutrients for the proper function of the human body. Although vitamins do not provide energy like carbohydrates or act as building blocks for tissue growth like protein, they help to synthesize and transport nutrients throughout the body, as well as keep systems in balance. Insufficient vitamin intake can lead to diseases; the connection between vitamins and deficiency diseases is well-known in conditions such as rickets, beriberi, scurvy and pernicious anemia. For example, ingesting too little vitamin C can lead to scurvy. Eating a balanced diet with fruits and vegetables helps to ensure an adequate vitamin intake.
Rickets is a disease caused primarily by the lack of adequate vitamin D, and its symptoms include weak bones, stunted skeletal development, and frequent muscle cramps. The relationship between vitamins and deficiency diseases can be seen when the body does not get enough vitamin D from sunlight, calcium or phosphates. These substances also act as electrolytes, or compounds that pass electrical impulses through the nervous system. When the body does not receive calcium from food, it draws from the skeletal system. The calcium and phosphorus that provide vitamin D can be found in milk and leafy vegetables, or vitamin supplements can be taken.
Beriberi also demonstrates the connection between vitamins and deficiency diseases. Thiamine, or vitamin B1, is a critical substance in the breakdown of glucose and other energy molecules. It also functions as a conductor for neural impulses by making the neural receptors more active. Without an adequate supply of B1, symptoms such as lethargy, slurred speech, rapid heartbeat and lack of muscle coordination can result. Dry beriberi affects the nervous system, while wet beriberi affects the cardiovascular system.
During the Age of Exploration, in the early 15th to 17th centuries, scurvy was a disease common in sailors due to the lack of vitamin C in their diets. Scurvy is the results of the body not absorbing iron, not producing enough collagen to keep tissue elasticity and thus not maintaining the immune system. The initial symptoms are poor appetite, diarrhea and weight loss; bleeding of the gums and other mucous tissues, tooth decay, skin disorders and infection of cartilage and connective tissue occurs as the disease progresses. Historically, scurvy was most often lethal when sailors had no access to citrus fruits as these provided the most vitamin C.
The connection between vitamins and deficiency diseases also includes pernicious anemia, which occurs when the body's red blood cell count decreases. This happens when not enough combalamin, or vitamin B12, is present in the body. Vitamin B12 normally combines with a protein called intrinsic factor, which is secreted in the stomach. When the combined B12 and intrinsic factor reach the small intestine, the substance is absorbed and converted to red blood cells.