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Vitamin B Nutrient Guide: Deficiency, foods and supplements

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The benefits of B vitamins, what happens if you're deficient, how to get B vitamins from your diet and what supplements are available.

What do the B vitamins do?

The B vitamins are vitamins B1 (thiamin), B2 (riboflavin), B3 (niacin), B5 (pantothenic acid), B6 (pyridoxine), B7 (biotin), B9 (folate or folic acid) and vitamin B12 (cyanocobalamin). In addition, three other nutrients are often added to a vitamin B complex supplement because of their complementary actions. Example nutrients include choline, inositol and para-amino-benzoic acid, or PABA.

There are over 20 authorised claims for B vitamins, including contributing to a normal energy-yielding metabolism, the normal functioning of the nervous system and heart, normal psychological function, maintenance of normal red blood cells, vision, hair and skin, reduction of tiredness and fatigue… the list goes on.

Did you know? Nutrients that were once called B4 (adenine), B8 (inositol), B10 (PABA) and B11 (another form of folate) were later found not to be essential for life and lost their designation as vitamins.

Vitamin B foods

B vitamins play a key role in how carbohydrates, protein and fats are metabolised and converted to energy to provide fuel for our cells.

Because B vitamins work in complementary ways, they are often combined in a single supplement known as a B group complex, which is used to help reduce tiredness and fatigue, support immunity, brain and nervous system function, aid memory and to maintain a healthy heart and red blood cells.

Food sources of B vitamins include wholegrains, meats, eggs and dairy products, beans, nuts, seeds and dark green leaves.

Vitamin B deficiency

Because B vitamins have vital roles in metabolism, deficiencies can lead to serious health problems, including fatigue, muscle weakness, reduced immunity, skin rashes, sores around the mouth, poor healing and dementia.

A severe lack of vitamin B3 produces a deficiency disease known as pellagra, while vitamin B1 deficiency causes a disease known as 'beri-beri', meaning 'extreme weakness' although these deficiency diseases are rare in developed countries.

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Vitamin B benefits

Energy production

  • Contributes to normal energy-yielding metabolism (B1, B2, B3, B6, B7, B12)

B vitamins play a central role in metabolism, and are needed during the metabolism of carbohydrate, protein and fat to release energy. B vitamins are essential for the production of energy from glucose, for example, and for the release of energy from muscle starch stores (glycogen) and to process fatty acids released from body fats and amino acids from recycled proteins.

Reduction of tiredness and fatigue

  • Contributes to the reduction of tiredness and fatigue (B2, B3, B5, B6, B9, B12)

Because B vitamins are needed for energy production, they are especially important for muscle cells that contract regularly, and to reduce tiredness and fatigue. In a study involving 80 healthy, elderly women, taking a B1 supplement for 6 weeks significantly improved general wellbeing and decreased feelings of fatigue.1

Immune support

  • Contributes to normal function of the immune system (B9, B12)

Some B vitamins, such as B2 and B12, are needed for the production of antibodies to help protect against viral and bacterial infections.

Nervous system support

  • Contributes to normal functioning of the nervous system (B1, B2, B3, B6, B7, B12)
  • Contributes to the protection of cells from oxidative stress (B2)
  • Has a role in the process of cell division (B9, B12)
  • Contributes to maternal tissue growth during pregnancy (B9)

B vitamins are involved in the way nerves conduct messages, and are essential for the central and peripheral nervous systems to work properly. B group vitamins are needed for optimal brain function, and deficiency of these vitamins has been associated with higher levels of nerve inflammation and oxidative stress within the brain.2

Folate is particularly important during early foetal development when the brain and spinal cord are forming, to help prevent birth abnormalities known as neural tube defects (e.g. spina bifida).3

Psychological function

  • Contributes to normal mental performance (B5)
  • Contributes to normal psychological function (B1, B3, B6, B7, B9, B12)
  • Contributes to normal protein and glycogen metabolism (B6)

B vitamins are needed to supply energy (glucose) for brain cells and to produce brain communication chemicals (neurotransmitters) such as serotonin. Taking B supplements can therefore help to preserve brain health.4

Maintenance of normal hair, skin and mucous membranes

  • Contributes to the maintenance of normal skin (B2, B3, B7)
  • Contributes to the maintenance of normal hair (B7)
  • Contributes to the maintenance of normal mucous membranes (B2, B3)

B vitamins are important for maintaining healthy hair, skin, nails and mucous membranes such as those lining the mouth and intestines. Biotin (vitamin B7) is especially vital for stimulating cell growth in healing tissues, helps to rejuvenate ageing skin and reduces skin mottling.

It is added to many hair care products as pantothenate to promote the growth of strong, healthy hair. In women with brittle nails, taking biotin supplements was found to increase nail plate thickness by 25%.5 Splitting of nails was also reduced.

Healthy circulation

  • Contributes to the normal metabolism of iron (B2)
  • Contributes to the maintenance of normal red blood cells (B2)
  • Contributes to the maintenance of normal red blood cell formation (B6, B12)
  • Has a role in the process of cell division (B9, B12)
  • Contributes to normal cysteine synthesis (B6)
  • Contributes to normal homocysteine metabolism (B6, B9, B12)

Vitamin B2 is involved in the metabolism of iron and, together with B12, is needed to produce normal red blood cells in which the iron-containing blood pigment, haemoglobin, carries oxygen around the body. Vitamins B6, B12 and folic acid are also needed to break down homocysteine – a harmful amino acid which, when allowed to build up in the circulation, is an important risk factor for the development of atherosclerosis, coronary heart disease and stroke.6

Maintenance of normal vision

  • Contributes to the maintenance of normal vision (B2)

Some B vitamins are important for eye health. Vitamin B2, for example, is an antioxidant that helps to reduce oxidative stress in the eyes, and deficiency can increase the risk of developing cataracts.7


B vitamins are water-soluble so are unlikely to build up in the body to cause side-effects. Although vitamin B12 can be stored in the liver, the European Food Safety Authority (EFSA) could find no adverse effects on which to base a tolerable upper intake level.8

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