HSR's (Health Supplement Retailer) Guide to VitaminsB VitaminsThe B vitamins consist of 11 water-soluble nutrients; they are considered co-enzymes that help the body metabolize food into energy, synthesize antibodies for the immune system and provide support for the daily mechanics of life. Even though this vitamin comes in many forms, it is easy to become deficient in B vitamins, especially for vegetarians, since meat is a naturally abundant source of these nutrients. BiotinBiotin is one of the more recently discovered B vitamins. It was first isolated in 1936, and the structure was identified in 1942 and the structure of the vitamin was synthesized in 1943. It is essential for the activity of many enzyme systems. Biotin absorption takes place in the proximal small intestine. Dietary biotin, which is protein-bound, must be acted upon by intestinal enzymes in order to liberate free biotin for absorption. Some biotin is also absorbed from the distal small intestine where it is biosynthesized by the normal flora in the intestine. Biotin deficiency in humans is very rare, probably due to the fact that biotin is synthesized by beneficial bacteria in the human gastrointestinal (GI) tract. Biotin plays a vital role in the production of energy from the metabolism of carbohydrates and fats. It is involved in the manufacture of fats and the excretion of byproducts from protein metabolism. It is also known as the vitamin that produces healthy hair and helps prevent graying. Applications include:
CholineClassifying choline as a vitamin is questionable since humans synthesize it; however, because the rate of synthesis is normally insufficient to meet human metabolic needs, choline has been included as an essential vitamin nutrient. The primary dietary source of choline is in the form of the phospholipid phosphatidylchotine (PC). Choline is readily absorbed throughout the small intestine. Most foods contain choline in the form of PC. Both pancreatic secretions and cells in the intestinal mucosa contain enzymes that are capable of hydrolyzing PC, which releases the choline for absorption. Choline plays a critical role in the higher level cerebrocortical functions of thoughts, memory and intellect. It is a precursor to and component of the neurotransmitter acetylcholine (ACh), which is involved in regulating a wide range of neurological activities, including the functions of movement, coordination and the stimulation of muscle contraction. High doses of PC may improve memory and cognitive function. It also functions in the metabolism of fat and the transport of fat from the liver, and can serve as a methyl donor in many important biochemical pathways, its clinical applications include:
Cobalamin (B12)Cobalamin is the generic name of vitamin B12 because it contains the heavy metal cobalt, which gives this water-soluble vitamin its red color. Vitamin B12 is an essential growth factor and plays a role in the metabolism of cells, especially those in the gastrointestinal tract, bone marrow, and nervous tissue. Several different cobalamin compounds exhibit vitamin B12 activity. The most stable form is cyanocobalamin, which contains a cyanide group that is well below toxic levels. To become active in the body, cyanocobalamin must be converted to either methylcobalamin or adenosylcobalamin. A protein in gastric secretions called intrinsic factor binds to vitamin B12 and facilitates its absorption. Without intrinsic factor, only a small percentage of vitamin B12 is absorbed. Once absorbed, relatively large amounts of the vitamin can be stored in the liver. Vitamin B12 primarily functions as a methyl donor, transferring methyl groups to synthesize DNA and to convert homocysteine to methionine. It functions as a hydrogen carrier in hydrogen transfer reactions and is necessary for the maturation of red blood cells. It plays a major role in the functioning and maintenance of the nervous system and is required for the synthesis of myelin, the insulation around nerves.
Folic Acid (B9)Isolated in 1946 from spinach leaves, its name comes from folium, the Latin word for "leaf." In the body, folic acid is converted to its biologically active form tetrahydrofolic acid (THFA). Niacin and vitamin C are necessary for this conversion. Folic acid absorption occurs primarily in the first part of the smal intestine via two separate mechanisms: active transport, which requires a folate-binding protein, and passive diffusion, which accounts for 20 percent to 30 percent of folate absorption. Like cobalamin, folic acid is necessary for the synthesis of DNA and RNA. It is essential for proper cellular division and the transmission of the genetic code to all newly formed cells. It is required for some methylation reactions, such as the conversion of homocysteine to methionine. Folic acid is involved in the synthesis of proteins and various amino acids and is essential for healthy blood cells. It may be best known as the vitamin that is necessary for the closure of the neural tube during pregnancy.
InositolInositol is a compound that has been known for a long time, but it was in 1940 scientists first realized that it was an essential nutrient. It is found in the liver, kidney, skeletal and heart muscle. It is also present in the leaves and seeds of many plants. In animal tissues, inositol occurs as a component of phospholipids; in plants, it usually occurs as phytic acid, the hexaphosphate ester of inositol. In humans, inositol is synthesized in the intestinal tract by beneficial bacteria. Phosphatidylinositol (PI) facilitates the production of arachidonic acid, As part of phospholipids in cellular membranes, PI helps to mediate cellular responses to external stimuli. Some studies have shown that inositol is as effective as the pharmaceutical imipramine in treating depression. Studies have also shown inositol to provide significant improvement in patients with obsessive-compulsive disorder and panic attacks. Inositol is useful in the prevention and treatment of diabetic neuropathy,' and post-mortem studies have found the sciatic nerves of diabetic individuals contain significantly lower concentrations of inositol compared to controls. Niacin (B3)Niacin, known as vitamin B3, can be synthesized in humans by converting tryptophan to niacin. It functions metabolically as a component of two important co-enzymes: nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP), known as the pyridine nucleotides. These niacin-containing co-enzymes play an essential role in more than 200 chemical reactions in the body. Niacin, which is also known as nicotinic acid, lowers elevated blood lipide and may reduce mortality. In addition to being used alone, it has also been used in combination with cholesterol-lowering drugs to increase the lipid-lowering effect of the drugs. Niacinamide, which is also known as nicotinamide, has been used in patients newly diagnosed with Type I diabetes to prevent further destruction of pancreatic beta cells, in patients with Type 11 diabetes who cannot be controlled with sulfonylureas,' and in people with arthritis.
Panthothenic Acid (B5)Roger Williams, Ph.D., discovered vitamin B5 in 1933 and, since it is present in all cells, he named it pantothenic acid from the Greek word pantothen, meaning "everywhere." Pantothenic acid plays a number of essential metabolic roles, including the production of some hormones and neurotransmitters, and is involved in the metabolism of all carbohydrates, fats and proteins. Pantethine, which is the stable and most active form of pantetheine, has been reported to be effective at improving abnormal lipid profiles in both adults and children. It reportedly lowers elevated triglycerides and LDL cholesterol while raising levels of beneficial HDL cholesterol.' Pantethine has been reported to be especially effective at lowering elevated blood lipide in patients with diabetes without hindering blood sugar control. It participates in the metabolism of acetaldehyde' and assists with synthesis of steroid hormones and proper functioning of the adrenal glands. Co-enzyme A (CoA), which is the active form of pantothenic acid, helps transfer two carbon units in a wide variety of biochemical reactions. CoA enhances the release of energy from carbohydrates in the Krebs cycle and assists the synthesis of phospholipids, fats, cholesterol, bile acids and acetylcholine. Applications include:
Pyridoxine (B6)Pyridoxine (vitamin B6) functions as a cofactor in more than 100 enzyme reactions. Many of its activities are related to the metabolism of amino acids and other proteins include hemoglobin, serotonin, hormones and prostaglandins. After entering a cell, vitamin B6 is phosphorylated and converted into its active form, pyridoxal 5 phosphate (PLP). Vitamin B6 is readily absorbed in the intestines. The mucosal cells contain the enzyme pyridoxal kinase, which catalyzes the conversion to the active form PLP. Vitamin B6 can be neurotoxic when taken in large doses. In both case reports and clinical studies, doses of 1 g/d to 6 g/d have been associated with neurotoxicity. All patients recovered without problems after discontinuing or substantially reducing their intake of vitamin B6. Pyridoxine is required for the production of neurotransmitters derived from amino acids such as serotonin, gamma amino butyric acid (GABA), norepinephrine, acetylcholine and histamine. It regulates amino acid metabolism and is necessary for the formation of hemoglobin and the growth of red blood cells. Applications include:
Riboflavin (B2)Riboflavin is essential for normal growth and development, reproduction, lactation, physical performance and well-being. It participates in essential biochemical reactions, especially those that yield energy. Vitamin B2 is water-soluble and must be supplied daily. Riboflavin belongs to a group of yellow fluorescent pigments called flavins. In its pure state, it is a yellow crystalline powder with a slight odor. When excreted, it gives the urine a characteristic bright yellow color. Riboflavin combines with phosphoric acid to become part of two important flavin co-enzymes, FMN (flavin mononucleotide) and FAD (flavin adenine dinucleotide). FMN and FAD are known to bind to more than 100 flavoprotein enzymes. These riboflavin-containing enzymes, which function as hydrogen carriers, catalyze many of .the oxidation-reduction reactions in cells. Vitamin B2 is absorbed from the upper part of the small intestine, and is better absorbed when taken with food. Only approximately 15 percent is absorbed if taken alone versus 60 percent if taken with food. The conversion of riboflavin into its coenzymes takes place in most cells throughout the body, but especially in the cells of the small intestine, liver, heart and kidneys. Riboflavin has antioxidant activity, both by itself and as part of the enzyme glutathione reductase. It plays a role in the conversion of carbohydrates to ATP in the production of energy and is necessary for growth and reproduction. FMN and FAD play roles in fatty acid synthesis. Thiamine (B1)Vitamin B1, also known as thiamine, was the first of the B vitamins to be discovered. It was isolated in 1926 as a water-soluble, crystalline, yellowish- white powder with a salty, slightly nutty taste. In 1936, Roger Williams, Ph.D., synthesized it and determined the chemical formula. Thiamine plays a vital role in the conversion of blood sugar (glucose) to energy in the Krebs cycle and is involved in the synthesis of acetylcholine metabolic activities primarily affect the nerves, muscles and cardiovascular system. Beriberi is the classic vitamin B1 deficiency syndrome. When beriberi occurs in the United States, it is most commonly seen in severely malnourished infants or elderly people. In adults, alcoholism, hemodiatysis or peritoneal dialysis, malabsorption syndromes and diets consisting primarily of highly processed, refined foods can be causes of vitamin BI deficiency? gastrointestinal symptoms can include anorexia, indigestion and weight loss. Two lipid-soluble forms of vitamin B1 are available. One is named thiamine propyl disulfide (TPD). The second is thiamine tetrahydrofurfuryl disulfide (TTHF), which is sometimes called fursulthiamine. There is some indication that these compounds are more efficiently absorbed and utilized than water-soluble thiamine hydrochloride and some companies are beginning to include them in product formulations. Thiamine plays an essential role in energy production, and plays a role in conversion of glucose to energy. It helps convert fatty acids to hormones such as cortisol and progesterone, and turn amino acids into proteins, hormones and enzymes. Alcohol interferes with the absorption of vitamin B1, which is necessary for the metabolism of alcohol. Severe deficiency associated with alcohol consumption produces a condition called Wernicke-Korsakoff syndrome. Reprinted from the November 2002 issue of HSR's Guide to Vitamins |
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