1. Background

Vitamin B 5 is pento- thenic acid! Although rare, excess pyridoxine can lead to irreversible sensory neuropathy. Biotin is a coenzyme in all carboxylase enzyme complexes that are not vitamin K -dependent!

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  2. Vitamin B complex.
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Eating raw eggs contain avidin impairs the resorption of biotin. Biotin loves avidin! Fol iage leafy green vegetables contains Fol ate! Unlike vitamin B 12 deficiency , folate deficiency is not associated with neurologic symptoms. Folic acid supplementation is recommended at least one month before conception and during the entire 9 months of pregnancy. Vitamin B 12 is the only water-soluble vitamin that is stored in the body in significant amounts!

Vitamin C deficiency results in s C urvy due to impaired C ollagen synthesis. Clinical science Vitamins are a group of chemically diverse organic compounds that an organism requires for normal metabolism. Fat-soluble vitamins Water-soluble vitamins Vitamins Vitamin A retinol Vitamin D calciferol Vitamin E tocopherol Vitamin K phytomenadione Vitamin B 1 thiamine Vitamin B 2 riboflavin Vitamin B 3 niacin Vitamin B 5 pantothenic acid Vitamin B 6 pyridoxine Vitamin B7 biotin Vitamin B 9 folate Vitamin B 12 cobalamin Vitamin C ascorbic acid Sources Mainly diet Intestinal flora: small amounts of vitamin K are synthesized by intestinal bacteria Vitamin D is predominantly synthesized in the body Mainly diet Intestinal flora: small amounts of vitamin B 7 , B 9 , and B 12 are synthesized by intestinal bacteria Absorption Absorption depends on intestinal and pancreatic function Require lipids for absorption Absorption in the intestine via specific luminal transporters Storage Can be stored for long periods of time in the liver and adipose tissue Not stored in the body, except vitamins B 9 and B 12 , which are stored in the liver Hepatic stores of B9 last for approx.

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  • Functions Function primarily as Hormones vitamin D Antioxidants e. Name Active forms Sources Functions Deficiency Toxicity Vitamin A retinol Retinal Retinoic acid Liver , kidney , butter, egg yolks, leafy vegetables Vision retinal pigments Antioxidant Gene transcription Differentiation of epithelial cells into specialized tissue i. Characteristics Synonyms : retinol Active forms : retinal , retinoic acid Sources Plant sources ; : as inactive provitamin esp.

    Vitamin A deficiency [1] Causes Disorders associated with fat malabsorption : inflammatory bowel disease e. Keratinizing squamous metaplasia of the bladder pearl-like plaques on cystoscopy Xerosis cutis Poor growth Immunosuppression ; : vitamin A deficiency increases the risk of a measles infection taking a severe course. Therapeutic uses Measles Treatment with vitamin A is recommended for all individuals with vitamin A deficiency especially common in resource-limited or developing countries Administering vitamin A reduces complications and mortality in individuals with vitamin A deficiency Skin conditions, including severe cystic acne e.

    Characteristics Active form : 1,dihydroxyvitamin D 1,2 5- OH 2 D 3 , calcitriol Sources : Ergocalciferol vitamin D 2 ; : mushrooms ; , fo rtified foods ; e. Vitamin K deficiency [10] Causes Liver failure e. Characteristics Synonyms : thiamine Active form : thiamine pyrophosphate TPP ; activation via intracellular phosphorylation of thiamine Sources : whole grain cereals e. Therefore, thiamine should be administered prior to glucose Clinical features Beriberi : inadequate thiamine uptake due to malnutrition , heavy drinking , or increased demand e.

    Also used in the respiratory burst , the cytochrome P system , and by glutathione reductase.

    Sources : meat liver , cereals, seeds, legumes Synthesis in the liver very small amounts : derived from tryptophan ; ; requires vitamins B 2 and B 6 Resorption : passive resorption in the intestine Functions Cofactor for redox reactions e. Characteristics Synonyms : pyridoxine Active form : pyridoxal phosphate PLP Sources : nuts, whole grains, vegetables, yeast , meat esp. Therapeutic use Tuberculosis : administer pyridoxine to prevent IHN-induced peripheral neuropathy Hyperemesis gravidarum.

    Characteristics Synonyms : biotin Sources Plants e. Characteristics Synonyms : folic acid , folate Active form : tetrahydrofolic acid THF Sources Leafy green vegetables , fortified foods e. Function THF : coenzyme for 1-carbon transfer and methylation reactions Involved in the synthesis of purine bases Vitamin B9 deficiency [20] Causes most common vitamin deficiency in the US Insufficient intake ; , malnutrition Alcohol use disorder Small bowel disease e.

    Therapeutic uses Prenatal supplementation 0. Characteristics Synonyms : cobalamin Active forms : methylcobalamin and adenosylcobalamin activation occurs in the liver Sources Almost exclusively in animal products except honey ; some dried and fermented plant foods e. Duodenum : Cobalamin is released from haptocorrin by trypsin and binds to intrinsic factor IF , a protein produced by the parietal cells of the stomach that facilitates cobalamin absorption in the ileum.

    B Vitamins and the Brain: Mechanisms, Dose and Efficacy—A Review

    Functions Cofactor for enzymatic reactions DNA synthesis via methionine synthase Odd-chain fatty acid metabolism via methylmalonyl CoA mutase Vitamin B 12 deficiency Causes Malnutrition , restricted diet e. Characteristics Synonyms : ascorbic acid , ascorbate Active form : ascorbate Sources : fruits and vegetables Resorption Passive resorption via oral mucosa Active resorption in the intestine especially jejunum Transport in blood : mainly free, only very small amounts as dehydroascorbate Storage : no specialized vitamin C stores; high concentrations in organs that require vitamin C as a cofactor e.

    Prepare and succeed on your medical exams. Find hundreds of Learning Cards covering all clinical subjects Practice answering thousands of USMLE-formatted multiple choice questions in the Qbank Explore concepts in depth with interactive images, videos and charts Fill knowledge gaps with the help of supportive features and an analysis of your progress. It appears that JavaScript is disabled in your browser.

    Kalinyak, J. Bean, et al. Fairfield, K. McCaddon, A. Regland, P. Hudson, and G. Miller, J. Green, D. Mungas, et al. Morris, M. Prescott, N. Ulrich, C. Robien, and R.

    American Dietetic Association. Cite this article Pick a style below, and copy the text for your bibliography. October 20, Retrieved October 20, from Encyclopedia. Then, copy and paste the text into your bibliography or works cited list. Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia. Vitamin B complex is a set of 12 related water-soluble substances. Eight are considered vitamins , by virtue of needing to be included in the diet, and four are not, as the body can synthesize them.

    Since they are water-soluble, most are not stored to any great extent and must be replenished on a daily basis. Biotin in particular is not always included in B complex supplements. The four unnumbered components of B complex that can be synthesized by the body are choline, inositol, PABA, and lipoic acid. As a group, the B vitamins have a broad range of functions. These include maintenance of myelin, which is the covering of nerve cells. B vitamins are also key to producing energy from the nutrients that are consumed.

    Three members of this group—folic acid, pyridoxine, and cobalamin—work together to keep homocysteine levels low. Some B vitamins prevent certain birth defects like neural tube defects , maintain healthy red blood cells, support immune function, regulate cell growth, aid in production of hormones, and may have a role in preventing some types of cancer. They also function in maintenance of healthy skin, hair, and nails. There are many claims for usefulness of various B vitamins. Thiamine is thought to be supportive for people with Alzheimer's disease.

    Niacin at very high doses is useful to lower cholesterol, and balance high-density HDL and low-density LDL lipoproteins. Some evidence shows that niacin may prevent juvenile diabetes type I insulin dependent in children at risk.

    The metabolic processes of folic acid and Vitamin B12 deficiency Mahmood L - J Health Res Rev

    It may also maintain pancreatic excretion of some insulin for a longer time than would occur normally. Niacin has also been used to relieve intermittent claudication and osteoarthritis , although the dose used for the latter risks liver problems. Pyridoxine is used therapeutically to lower the risk of heart disease , and to relieve nausea associated with morning sickness and to treat premenstrual syndrome PMS. In conjunction with magnesium, pyridoxine may have some beneficial effects on the behavior of children with autism. Folic acid may reduce the odds of cervical or colon cancer in certain at risk groups.

    Homocysteine —An amino acid produced from the metabolization of other amino acids High levels are an independent risk factor for heart disease. Macrocytic anemia —A condition caused by cobalamin deficiency, which is characterized by red blood cells that are too few, too fragile, and abnormally large.

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    Neural tube defect —Incomplete development of the brain, spinal cord , or vertebrae of a fetus, which is sometimes caused by a folic acid deficiency. Vitamin B complex is most often used to treat deficiencies that are caused by poor vitamin intake, difficulties with vitamin absorption, or conditions causing increased metabolic rate such as hyperthyroidism that deplete vitamin levels at a higher than normal rate. Biotin and pantothenic acid are rarely deficient since they are broadly available in food, but often those lacking in one type of B vitamin are lacking in other B components as well.

    An individual may be symptomatic due to an inadequate level of one vitamin but be suffering from an undetected underlying deficiency as well. One possibility of particular concern is that taking folic acid supplements can cover up symptoms of cobalamin deficiency. In general, poor B vitamin levels will cause profound fatigue and an assortment of neurologic manifestations, which may include weakness, poor balance, confusion, irritability, memory loss, nervousness, tingling of the limbs, and loss of coordination.

    Depression may be an early sign of significantly low levels of pyridoxine and possibly other B vitamins.

    The importance of the B vitamins

    Additional symptoms of vitamin B deficiency are sleep disturbances, nausea, poor appetite, frequent infections, and skin lesions. This anemia can also result if a person stops secreting enough intrinsic factor in the stomach. The result of a lack of intrinsic factor is pernicious anemia, so called because it persists despite iron supplementation.

    The classic signs of pellagra are dermatitis, dementia , and diarrhea. Thiamine deficiency is similarly rare, save in the severely malnourished and alcoholics. A significant depletion causes a condition known as beriberi, and it can cause weakness, leg spasms, poor appetite, and loss of coordination.

    People are at higher risk for deficiency if they have poor nutritional sources of B vitamins, take medications or have conditions that impair absorption, or are affected by circumstances that increase the need for vitamin B components above the normal level. People who frequently fast or diet may also benefit from taking B vitamins.

    Vegans will need to use brewer's yeast or other sources of supplemental cobalamin, since the only natural sources are meats. Risk factors that may decrease absorption of some B vitamins include smoking, excessive use of alcohol, surgical removal of portions of the digestive tract, and advanced age. Some of the drugs that may cause this are corticosteroids , colchicine, metformin, phenformin, omeprazol, colestipol, cholestyramine, methotrexate, tricyclic antidepressants, and slow-release potassium.