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B Vitamins: Details

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Also known as: Vitamin B complex
Formal name: B1 (thiamine or thiamin); B2 (riboflavin); B3 (niacin); B5 (pantothenic acid); B6 (pyridoxal phosphate); B7 (biotin)
Related tests: Vitamin B12 and Folate

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Detailed Information on the B vitamins

B1

Name: Thiamine or thiamin

Also known as: Vitamin F, Aneurin, Thiamine diphosphate (TDP) – physiologically active form

Role: B1 is a coenzyme that helps the body produce energy, is involved in glucose, amino acid, and alcohol metabolism, and is required for the proper functioning of the nervous system, heart, and muscles.

Sources: Cereals and whole grains, potatoes, pork, seafood, nuts, legumes

Deficiency: In U.S., found primarily with chronic alcoholism. Can cause:
Wet beriberi – severe deficiency associated with cardiovascular failure
Dry beriberi – associated with nervous system, peripheral neuropathy
Wernicke's encephalopathy, Wernicke-Korsakoff syndrome – mental changes

Test name: Thiamine (Thiamine diphosphate) in blood
Other ways to measure: Transketolase (functional thiamine test)

B2

Name: Riboflavin
Also known as: Vitamin G

Role: B2 is a coenzyme involved in energy production and is required for the metabolism of other B vitamins

Sources: Cereals and whole grains, green leafy vegetables, lean meats, dairy products, eggs, enriched breads.

Deficiency: Called ariboflavinosis, usually seen along with other vitamin deficiencies in those with alcoholism, malabsorption, liver disease, and in the elderly.

Test name: Riboflavin, blood or urine
Other ways to measure: Glutathione reductase in erythrocytes (activity)

B3

Name: Niacin
Also known as: Nicotinic acid, Nicotinamide, Vitamin P, Vitamin PP

Role: B3 is involved in enzyme reactions, metabolism, and energy production. It is given in pharmacologic doses to lower LDL-cholesterol and triglycerides and raise HDL-cholesterol

Sources: B3 is found in lean meats, eggs, fish, whole grain cereals and legumes.

Deficiency: Severe deficiency in conjunction with a low-protein diet causes: Pellagra - classic symptoms are dermatitis, diarrhea, and dementia; may also cause a rash in areas exposed to the sun.

Deficiencies also seen with alcoholism, cirrhosis, Hartnup disease, Crohn disease, and carcinoid syndrome. Niacin synthesis requires adequate B6, B2, iron, and copper. Up to 60% of niacin is synthesized from tryptophan.

Toxicity: Pharmacologic doses can cause flushing and headaches. High doses may affect liver.

Test name: Niacin metabolites: N1-Methylnicotinamide, 2-Pyridone in urine thought to be the most reliable measure of intake and body status
Other ways to measure: measured as NAD (Nicotinamide adenine dinucleotide) in blood or urine

B5

Name: Pantothenic acid

Role: B5 helps break down and use fats, proteins, and carbohydrates.

Sources: Most foods

Deficiency: B5 deficiency is rare as it is widely distributed in foods. Associated with "burning feet" and impaired wound healing.

Test name: Pantothenic acid in blood or urine

B6

Name: Pyridoxal Phosphate (PLP)
Also known as: Three main forms: Pyridoxine, pyridoxamine, and pyridoxal

Role: B6 is a coenzyme involved in amino acid metabolism and hemoglobin synthesis. It is also necessary for the nervous system and immune system.

Sources: Pork, fish, chicken, bananas, wheat germ, legumes.

Deficiency: B6 deficiency is rare by itself; adequate B2 is required for the formation of active PLP; may be seen with chronic alcoholism, malabsorption, smoking, and in asthmatics who take theophylline; can cause convulsions and decreased immunity. Both deficiency and toxicity can cause peripheral neuropathy.

Test name: Pyridoxal phosphate (PLP)
Other ways to measure: Vitamin B6 functional test, Urine 4-pyridoxic acid, urine xanthurenic acid

B7

Name: Biotin
Also known as: Vitamin H, Vitamin B-w

Role: B7 is a coenzyme that is necessary for fat, protein, and carbohydrate metabolism and plays a role in hormone production.

Sources: Soy, egg yolks, peanuts, legumes, bananas, and grapefruit. B7 is also made by intestinal bacteria.

Deficiency: Very rare; may occur in those receiving total parenteral nutrition and with some inborn errors of metabolism; can cause weakness, delayed development, rash, hair loss, weakness.

Test names: Biotin in urine
Other ways to measure: Urinary 3-hydroxyisovalerate excretion

B12

Name: Cyancobalamin
See the article on Vitamin B12 and Folate

Folic Acid

Name: Folate
Also known as: Vitamin B9, Vitamin M
See the article on Vitamin B12 and Folate

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