Vitamins, continued metabolic function

Vitamin B12 is continually secreted in the bile, but most of this is reabsorbed and available for metabolic functions. If circulating vitamin B concentrations exceed the binding capacity of the blood, the excess wiU. be excreted in the urine, but in most circumstances the highest losses of vitamin B12 occur through the feces. 

The continued production of organic matter in the sea requires the availability of the many building blocks of life, including essential major elements such as carbon (C), nitrogen (N), and phosphorus (P) essential minor elements such as iron, zinc, and cobalt and, for many marine organisms, essential trace organic nutrients that they cannot manufacture themselves (e.g., amino acids and vitamins). These required nutrients have diverse structural and metabolic function and, by definition, marine organisms cannot survive in their absence. 

The most clearly documented role lor selenium is as a necessary component of glutathione peroxidase. Selenium is also involved in the functions of additional enzymes, e.g.. type I iodoihvronine deiodinase. leukocyte acid phosphatase, and glucuronidases. A role for selenium in electron transfer has been suggested as has involvement in nonheme iron proteins. Selenium and vitamin b appear to be necessary lor proper functioning of lysosomal membranes. A role for selenium in metabolism of thyroid hormone has been continued. 

Vitamin B12 (cobalamine) is needed to metabolize fatty adds and amino acids and to synthesize DNA in cells. Vitamin C also has several functions. It is needed to synthesize collagen, the most abundant protein in the body, but it also acts as an antioxidant, helping to reduce the risk of developing chronic diseases like heart disease and cancer. Water-soluble vitamins are not stored in the body. Because they are eliminated in urine, a continuous daily support through diet is required. However, even foods that contain the necessary vitamins can have reduced vitamin content after storage, processing, or cooking. Therefore, many people take a multivitamin tablet to supplement their diet. To ensure that these tablets contain the labeled amounts of vitamins, there must be a quality control assay for these tablets. 

FUNCTIONS. Vitamin D is primarily associated with calcium and phosphorus. It influences the absorption of these minerals and their deposit in bone tissue. Research is continuing to unfold the relationship of vitamin D to calcium and phosphorus metabolism. Although there are many gaps in our knowledge relative to the exact mechanism by which vitamin D carries out its various physiological functions, the current thinking is as follows ... 

---