Thiamin, or vitamin B1, is a water-soluble vitamin that plays a role in energy production (through the synthesis of adenosine triphosphate [ATP]) and nerve conduction. (ATP is the major source of energy that the human body utilizes to do work.) Thiamin is found in abundance in foods such as lean pork, legumes, and yeast. In contrast, polished (white) rice, white flour, refined sugars, fats, and oils are foods lacking this vitamin. People at risk for thiamin deficiency include those who consume large quantities of alcohol and those who live in impoverished conditions, for such people are deficient in substantial amounts of vitamins and minerals.
Beriberi is a clinical manifestation of thiamin deficiency. Symptoms include nervous system abnormalities (e.g., leg cramps, muscle weakness), limb swelling, elevated pulse, and heart failure. Wernicke-Korsakoff syndrome is a related condition (with symptoms such as a jerky gait, disorientation, and impaired short-term memory) that occurs among alcoholics.
Pellegra is a disease caused by a dietary deficiency of, or a failure to absorb, niacin (vitamin B3) or the amino acid tryptophan, a precursor of niacin. pellagra means "rough skin." Primary symptoms include the "3 Ds": dementia (mental symptoms), dermatitis (scaly skin sores), and diarrhea.
Osteoporosis, which is characterized by a decrease in the mass of otherwise normal bone, is the most common metabolic bone disease. Normal bone is made of a hard outer shell (the cortex) and an inner network of spicules (fibers), called trabecular, that give bone its characteristic strength. Bone mass is maintained at a progressive and then constant level until around the age of thirty-five. This maintenance is accomplished through bone remodeling, a cycle of breaking down and building up of bone. Beginning around age forty, the rate at which bone breaks down can exceed that at which it is built, resulting in diminished mass and a diminished amount of calcium in the bone. For women, in addition to this normal age-related bone loss, menopause and its subsequent reduction in female hormone levels (specifically estrogen) because a specific loss in cortical and trabecular bone. In those who develop osteoporosis, the reduction in cortical and trabecular bone can be up to 30-40 percent, resulting in fragile bones that are prone to fracture.
Several factors contribute to the development of osteoporosis. Smoking, alcohol, and a sedentary lifestyle have all been shown to increase the risk of developing the disorder. Age and gender are also contributory factors. Women who have low estrogen levels (e.g., after menopause) are more likely to develop osteoporosis than others. Also, men generally maintain a higher bone density than women, making them less susceptible to the condition.
Rickets was once considered an extremely common disorder of childhood. The term itself is derived from the old English word for "twist," or "wrick," and throughout history children with rickets could be identified by their bowed legs and knock knees, which gave them a twisted appearance.
Rickets is caused by a deficiency in vitamin D. During growth, human bone is made and maintained by the interaction of calcium, phosphorus, and vitamin D. Calcium is deposited in immature bone (Osteoid) in a process called calcification, which transforms immature bone into its mature and familiar form. However, in order to absorb and use the calcium available in food, the body needs vitamin D. In rickets, the lack of this important vitamin leads to low calcium, poor calcification, and deformed bones.
Vitamin D is the only vitamin that can be both acquired through food and made by the body itself. Although vitamin D can be absorbed through foods rich in animal fat, such as milk, cheese, fish, and meat, this absorption constitutes only about 10 percent of what the body needs in a single day. The remaining 90 percent is created by the body. Ultraviolet radiation from the sun converts 7-dihydrocholesterol in the skin to vitamin D3. This is then converted to the hormone calcitriol (the active form of vitamin D) in the kidney. Calcitriol allows absorption of calcium and phosphorus in the gut, primarily in the small intestine, and maintains the body's balance of calcium and phosphate through the kidney and bone. Without adequate vitamin D, the body can only absorb 10 to 15 percent of the calcium available in food. This balance of vitamin D, calcium, and phosphate is essential to the growth and maintenance of bones, especially in children. Deficiencies can also occur in elderly adults.
Last Modified : 2/20/2020