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B Vitamins

B vitamins are a group of water-soluble vitamins that play essential roles in various physiological functions within the body. There are eight distinct B vitamins, each with its own unique functions and benefits. The B vitamins are:

  1. B1 (Thiamine):
    • Function: Thiamine is crucial for converting carbohydrates into energy. It also plays a role in nerve function.
    • Sources: Whole grains, legumes, nuts, seeds, pork, and fortified cereals.
  2. B2 (Riboflavin):
    • Function: Riboflavin is involved in energy production, antioxidant defense, and maintaining healthy skin and eyes.
    • Sources: Dairy products, lean meats, green leafy vegetables, and enriched grains.
  3. B3 (Niacin):
    • Function: Niacin is important for energy production, DNA repair, and plays a role in skin health.
    • Sources: Meat, poultry, fish, whole grains, and legumes.
  4. B5 (Pantothenic Acid):
    • Function: Pantothenic acid is involved in the synthesis of fatty acids and the production of hormones and neurotransmitters.
    • Sources: Meat, whole grains, legumes, and avocados.
  5. B6 (Pyridoxine):
    • Function: Pyridoxine is important for amino acid metabolism, the synthesis of neurotransmitters, and the formation of red blood cells.
    • Sources: Meat, poultry, fish, bananas, potatoes, and fortified cereals.
  6. B7 (Biotin):
    • Function: Biotin is essential for metabolism, especially in the breakdown of carbohydrates, fats, and proteins.
    • Sources: Liver, egg yolks, nuts, seeds, and certain vegetables.
  7. B9 (Folate or Folic Acid):
    • Function: Folate is crucial for DNA synthesis, cell division, and the formation of red blood cells.
    • Sources: Leafy green vegetables, legumes, citrus fruits, and fortified grains.
  8. B12 (Cobalamin):
    • Function: Vitamin B12 is essential for DNA synthesis, red blood cell formation, and neurological function.
    • Sources: Meat, poultry, fish, dairy products, and fortified cereals.

B vitamins are critical for maintaining good health and well-being. They play vital roles in energy metabolism, the formation of red blood cells, DNA synthesis, and the functioning of the nervous system. Since B vitamins are water-soluble, they are not stored in the body in large amounts, and excess amounts are excreted in urine. Therefore, it is important to regularly consume foods rich in B vitamins or, if necessary, take supplements to meet daily requirements.

B-Vitamins
B-Vitamins

Not getting enough of certain B vitamins can cause diseases. A lack of B12 or B6 can cause anemia.

Vitamin B1

Thiamin is also known as vitamin B1. It helps to convert glucose into energy and has a role in nerve function.

Good sources of thiamin

  • wholemeal cereal grains
  • seeds (especially sesame seeds)
  • legumes
  • wheatgerm
  • nuts
  • yeast
  • pork.

Solubility

Water

Function

Precursor for TPP; involved in nerve conduction

Thiamine acts as a precursor molecule for TPP, which is a coenzyme for enzymes involved in carbohydrate and amino acid metabolism. These enzymes include pyruvate dehydrogenase (glycolysis), α-ketoglutarate dehydrogenase (citric acid cycle), transketolase (pentose phosphate pathway), and branched-chain keto acid dehydrogenase (amino acid metabolism). TPP has also been implicated in nerve conduction.

Vitamin B1 (Thiamine) Deficiency

Thiamin deficiency is generally found in countries where the dietary staple is white rice. Deficiencies in the Western world are generally caused by excessive alcohol intake and/or a very poor diet. Symptoms include – confusion, irritability, poor arm or leg (or both) coordination, lethargy, fatigue and muscle weakness.

Beriberi is a condition caused by thiamin deficiency and affects the cardiovascular, muscular, gastrointestinal and nervous systems. It can be classified as ‘wet’ and ‘dry’ beriberi. ‘Dry’ beriberi affects the nervous symptom while ‘wet’ beriberi affects the cardiovascular system.

Wernicke-Korsakoff syndrome (also called ‘wet brain’) is another thiamin-deficiency disease linked to alcohol excess and a thiamin-deficient diet. Alcohol reduces thiamin absorption in the gut and increases its excretion from the kidneys.

Cause

Most commonly associated with alcoholism, which leads to thiamine deficiency through poor dietary nutrition and impaired absorption of thiamine. Thiamine deficiency is also associated with malnutrition, malabsorption syndromes, and dialysis treatment.

Clinical Manifestations

  • Early disease presents with muscle cramps, poor appetite, and peripheral motor and sensory neuropathy (dry beriberi).
  • More advanced disease may present with wet beriberi (dilated cardiomyopathy resulting in high-output heart failure and pulmonary edema) or Wernicke-Korsakoff syndrome, which is a combination of Wernicke encephalopathy (characterized by the triad of confusion, ataxia, and ophthalmoplegia) and Korsakoff syndrome (amnesia and confabulation).

Treatment and Prognosis

Thiamine supplementation.

About half of patients will only have partial or no resolution of their symptoms with treatment.

Vitamin B2

Riboflavin is primarily involved in energy production and helps vision and skin health.

Good sources of riboflavin

  • milk
  • yoghurt
  • cottage cheese
  • wholegrain breads and cereals
  • egg white
  • leafy green vegetables
  • meat
  • yeast
  • liver
  • kidney.

Solubility

Water

Function

Precursor for FAD and FMN

Vitamin B2 (Riboflavin) Deficiency

Riboflavin deficiency (or ariboflavinosis) is rare and is usually seen along with other B-group vitamin deficiencies. People at risk include those who consume excessive amounts of alcohol and those who do not consume milk or milk products.

Cause

Usually caused by dietary deficiency or other conditions associated with malnutrition, such as alcoholism.

Clinical Manifestations

Usually occurs in conjunction with other B vitamin deficiencies. Symptoms of riboflavin deficiency include dermatitis, glossitis, corneal vascularization, angular cheilitis (cracking at corners of lips), weakness, and anemia.

Treatment

Vitamin B2 supplementation.

Vitamin B3

Niacin is essential for the body to convert carbohydrates, fat and alcohol into energy. It helps maintain skin health and supports the nervous and digestive systems. Unlike other B-group vitamins, niacin is very heat stable and little is lost in cooking.

Solubility

Water

Source

  • meats
  • fish
  • poultry
  • milk
  • eggs
  • wholegrain breads and cereals
  • nuts
  • mushrooms
  • all protein-containing foods.

Function

  1. Precursor for NAD and NADP
  2. Niacin serves as a precursor for coenzymes NAD and NADP, both of which act as electron acceptors in a variety of oxidation-reduction reactions, especially in the citric acid cycle and the electron transport chain.

Supply

Niacin is supplied to the body through dietary ingestion or by endogenous synthesis from the amino acid tryptophan.

Vitamin B3 (Niacin) Deficiency

People who drink excessive amounts of alcohol or live on a diet almost exclusively based on corn are most at risk of pellagra. Others causes are associated with digestive problems where the body does not absorb niacin efficiently.

The main symptoms of pellagra are commonly referred to as the 3 Ds – dementia, diarrhoea and dermatitis. This disease can lead to death if not treated.

Cause

Causes include dietary inadequacy, alcoholism, Hartnup disease (results in deficiency of tryptophan), isoniazid treatment, and carcinoid syndrome.

Clinical Manifestations

Symptoms of mild deficiency include poor appetite with weight loss, weakness, and glossitis. More advanced deficiency results in pellagra, which consists of the triad of dermatitis (usually on sun-exposed areas), dementia, and diarrhea.

Treatment

Niacin supplementation.

Toxicity/ Side effects

High doses of niacin supplementation have been found to reduce LDL and VLDL levels and to increase HDL levels and thus can be used to treat hypercholesterolemia and hypertriglyceridemia. Side effects of high-dose niacin include peripheral flushing (caused by vasodilation) and GI upset.

Excessive niacin intake

Large doses of niacin produce a drug-like effect on the nervous system and on blood fats. While favourable changes in blood fats are seen, side effects include flushing, itching, nausea and potential liver damage.

Pantothenic acid (B5)

Pantothenic acid is needed to metabolise carbohydrates, proteins, fats and alcohol as well as produce red blood cells and steroid hormones.

Solubility

Water

Source

Pantothenic acid is widespread and found in a range of foods, but some good sources include:

  • liver
  • meats
  • milk
  • kidneys
  • eggs
  • yeast
  • peanuts
  • legumes.

Function

Constituent of coenzyme A and fatty acid synthase

Vitamin B5 Deficiency

Vitamin B5 (pantothenic acid) is a constituent of CoA and fatty acid synthase. Deficiency is rarely seen, but when it does occur (usually in conjunction with other B vitamin deficiencies), it may present with dermatitis, hair loss, and GI upset. Because pantothenic acid is found in such a wide variety of foods, deficiency is extremely rare.

Vitamin B6

Pyridoxine is needed for protein and carbohydrate metabolism, the formation of red blood cells and certain brain chemicals. It influences brain processes and development, immune function and steroid hormone activity.

Solubility

Water

Source

  • cereal grains
  • legumes
  • green and leafy vegetables
  • fish and shellfish
  • meat and poultry
  • nuts
  • liver
  • fruit.

Function

Precursor for pyridoxal phosphate; involved in heme synthesis.

  1. Vitamin B6 is a precursor forpyridoxal phosphate, which is a coenzyme that acts as a carrier of amine groups during the transamination reaction in amino acid breakdown, as a cofactor for cystathionine synthase during methionine metabolism, and as a cofactor during other decarboxylation and trans-sulfuration reactions. Pyridoxal phosphate is also involved in the synthesis of heme.

Vitamin B6 (Pyridoxine) Deficiency

Pyridoxine deficiency is rare. People who drink excessive amounts of alcohol, women (especially those on the contraceptive pill), the elderly and people with thyroid disease the most at risk.

Causes

Caused by dietary malnutrition, alcoholism, pregnancy, certain metabolic diseases (eg, homocystinuria), or certain pharmacologic agents (isoniazid, penicillamine, oral contraceptives) that interfere with pyridoxine metabolism or act as competitive inhibitors at pyridoxinebinding sites.

Clinical Manifestations

Mild deficiency results in personality disturbances (irritability, depression), dermatitis, and glossitis. More severe deficiency manifests as a peripheral neuropathy, seizures, and a sideroblastic anemia.

Treatment

Vitamin B6 supplementation.

Toxicity

Vitamin B6 toxicity can occur in patients receiving large doses of vitamin B6 over a long time. It generally manifests as a sensory neuropathy, which can be irreversible.

Excessive pyridoxine intake

Pyridoxine toxicity is mostly due to supplementation and can lead to harmful levels in the body that can damage the nerves.

Vitamin B7 (Biotin)

Biotin (B7) is needed for energy metabolism, fat synthesis, amino acid metabolism and glycogen synthesis. High biotin intake can contribute to raised blood cholesterol levels.

Solubility

Water

Sources

  • liver
  • cauliflower
  • egg yolks
  • peanuts
  • chicken
  • yeast
  • mushrooms.

Supply

Biotin can be ingested in the diet and is also synthesized in the bowel by intestinal flora.

Biotin Deficiency

Biotin deficiency is very rare – it’s widely distributed in foods and only required in small amounts. Over-consumption of raw egg whites over periods of several months (by bodybuilders, for example) can induce deficiency because a protein in the egg white inhibits biotin absorption.

Causes

Associated with long-term antibiotic use, increased ingestion of raw egg whites (which contain avidin, a protein that interferes with biotin digestion), and long-term parenteral nutrition.

Functions

Biotin acts as a cofactor for three different carboxylase enzymes:

  • Pyruvate carboxylase (converts pyruvate to oxaloacetate during gluconeogenesis),
  • Propionyl CoA carboxylase (involved in breakdown of propionyl CoA, a product of β-oxidation in fatty acid metabolism, to methylmalonyl CoA), and
  • Acetyl CoA carboxylase (converts acetyl CoA to malonyl CoA in fatty acid synthesis).

Clinical Manifestations

Deficiency is rarely seen, but symptoms include alopecia, dermatitis, GI upset, muscle pain with paresthesias, and elevated cholesterol levels.

Treatment

Biotin supplementation for patients requiring parenteral nutrition or long-term antibiotic use.

Vitamin B9 (Folic Acid)

Folate, or folic acid (the synthetic form of folate which is used extensively in dietary supplements and food fortification

) is needed to form red blood cells, which carry oxygen around the body. It helps the development of the foetal nervous system, as well as DNA synthesis and cell growth. Women of child-bearing age need a diet rich in folate for this reason.

If planning a pregnancy or in the first trimester of pregnancy, you should visit your doctor to make sure you’re getting enough folate. This is important to reduce the risks of neural tube defects such as spina bifida in the baby.

Solubility

Water

Sources

  • green leafy vegetables
  • legumes
  • seeds
  • liver
  • poultry
  • eggs
  • cereals
  • citrus fruits.

Since 2009, all bread sold in Australia (except organic) has been fortified with folic acid.

Functions

The reduced form of folic acid (tetrahydrofolate) acts as a cofactor for many one-carbon transfer reactions in nucleotide synthesis (especially the conversion of dUMP to dTMP in the synthesis of thymidylate), in methionine synthesis (especially the conversion of homocysteine to methionine), and in the conversion of serine to glycine and vice versa.

Folic Acid Deficiency

Causes

Caused by inadequate dietary intake (especially seen in alcoholics), medications that decrease folate absorption in the intestine (eg, sulfasalazine, phenytoin, TMP-SMX), sprue, methotrexate use (inhibits conversion of folic acid to active form), or conditions in which folic acid requirements are increased (eg, pregnancy or chronic hemolytic anemia).

Clinical Manifestations

Glossitis and diarrhea; neural tube defects can result from maternal folate deficiency.

Treatment

Folic acid supplementation.

Excessive folic acid intake

Although folic acid is generally considered non-toxic, excessive intakes above 1,000mcg per day over a period of time can lead to malaise, irritability and intestinal dysfunction. The main risk with excessive folate intake is that it can mask a vitamin B12 deficiency, so it’s best to consume these 2 vitamins within the recommended amounts.

Vitamin B12

Cyanocobalamin (or vitamin B12) helps to produce and maintain the myelin surrounding nerve cells, mental ability, red blood cell formation and the breaking down of some fatty acids and amino acids to produce energy. Vitamin B12 has a close relationship with folate, as both depend on the other to work properly.

Solubility

Water

Source

  • liver
  • meat
  • milk
  • cheese
  • eggs
  • almost anything of animal origin.

Function

  1. Cofactor in methionine metabolism and in propionyl coenzyme A metabolism.
  2. In methionine metabolism, vitamin B12 serves as a cofactor in the conversion of homocysteine to methionine.
  3. In the metabolism of propionyl CoA, a final product of fatty acid β-oxidation, vitamin B12 serves as a cofactor in the conversion of methylmalonyl CoA to succinyl CoA.

Absorption

When ingested, vitamin B12 becomes bound to intrinsic factor, a protein secreted by the parietal cells of the gastric mucosa. The vitamin B12-intrinsic factor complex is then absorbed in the distalileum, and the vitamin B12 is stored in the liver.

Vitamin B12 (Cobalamin) Deficiency

Because vitamin B12 is only found in foods from animal sources, people following strict vegan diets, as well as breastfed babies of vegan mothers, tend to be most commonly affected. Absorption of B12 from the gut also tends to decrease with age, so the elderly is another group who are more at risk of deficiency.

Causes

Causes include dietary deficiency (usually seen only in vegans), pancreatic insufficiency, decreased production of intrinsic factor (eg, pernicious anemia or gastrectomy), decreased ileal absorption of vitamin B12 (eg, Crohn disease, Diphyllobothrium latum infection, sprue, or surgicalresection of small intestine), or blind loop syndrome (leading to bacterial overgrowth and resulting competition for vitamin B12).

Clinical Manifestations

Neurologic abnormalities (ataxia, impaired proprioception, and vibratory sensation); glossitis; diarrhea; symptoms of autoimmune gastritis (if vitamin B12 deficiency is caused by pernicious anemia).

Treatment

Vitamin B12 supplementation.

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