Guide to vitamin B

We need B vitamins for a healthy nervous system, for converting food to energy and for making red blood cells.

There are eight B vitamins in total and they are all water-soluble and can’t be stored in the body, so a constant supply from your diet is required – otherwise levels can quickly become depleted. Taking a supplement is a popular back-up.

Dr Sarah Brewer says: ‘B vitamins are needed for many different functions in the body, and are vital for energy production in cells. Lack of B vitamins is associated with physical symptoms such as feeling tired and run down, as well as emotional symptoms such as low mood, irritability and anxiety.’

What do B vitamins do?

The B vitamin family includes: vitamin B1 (thiamin) which aids the nervous system and enzyme function, making energy available; B2 (riboflavin) for healthy skin and eyes; B3 (niacin) needed to release energy from food; B5 (pantothenic acid) for mental performance and normal heart function support; B6 (pyridoxine) for reducing tiredness and fatigue; and B7 (biotin) for the metabolism of fat.

Vitamin B9 (folic acid) is essential for neural tube development in babies in the first weeks of pregnancy, and all women planning a pregnancy and pregnant women are advised to take a 400mcg supplement for the first three months of their pregnancy.

Vitamin B12 is needed for red cell production and the production of myelin, the protective sheath around nerves. 


Feeling tired affects one in five people and one in 10 suffer long term fatigue. It’s much more common in women. There are many causes, but a shortage of B vitamins can sometimes be a factor. Vitamin B6 releases stored energy as well as helping to form haemoglobin, the substance in red blood cells that carries oxygen around the body. Vitamins B1, B2 and B12 all release energy from food, too.

Mood and stress

B vitamins are sometimes referred to as the ‘stress vitamins’ as symptoms of deficiency can include irritability, tension and anxiety. They are needed to make brain chemicals including serotonin, a ‘feel-good’ neurotransmitter.

Some studies have found low levels of folate and B12 in depressive patients. A 2013 Swansea University study concluded high levels of vitamin B supplements may be effective in improving mood states in healthy individuals.

A Cochrane review also found that taking B12, folic acid and B6 enhanced and sustained response to antidepressants over a 12-month period. One review concluded folic acid and vitamin B12 should be tried to improve treatment outcomes in depression.  

Getting vitamin B from your diet

The best sources of vitamin B1 are found in vegetables (especially peas), fresh and dried fruits, eggs, wholegrains and liver.

Vitamin B2 (riboflavin) is found in milk, eggs, rice and fortified cereals.

Meat, fish, wholegrains, eggs and milk are good sources of vitamin B3.

Vitamin B5 is found in chicken, beef, potatoes, oats, kidney, eggs, broccoli and wholegrains.

Pork, chicken, turkey, fish, wholegrains, eggs, pulses, soya, peanuts, potatoes, bananas and avocados all contain vitamin B6.

Vitamin B12 is found in meat, fish, milk, cheese and eggs. Vegans are particularly at risk of deficiency, but vegetarian sources include fortified foods and some sea vegetables. 

Folic acid is found in green leafy vegetables, liver, peas, chickpeas, brown rice, asparagus, oatmeal and avocados.


There are some issues with taking high doses of some B vitamins. For example, taking more than 200mg of vitamin B6 for extended periods can lead to loss of feeling in the arms and legs (called peripheral neuropathy). This is usually reversible. Experts say daily doses of 10mg to 200mg are unlikely to cause harm, though.

Taking doses of folic acid higher than 1mg daily can disguise vitamin B12 deficiency. The Department of Health says taking 2mg a day, or less, in vitamin B12 supplements is unlikely to cause any harm. 

Correct dosage

There are daily recommended nutritional intakes set for individual B vitamins: these include 1.4mg a day for men and 1.2mg a day for women for B6, and 0.0015mg a day for vitamin B12. However, many people find it easier to take a supplement combining all eight of the essential B vitamins.

Nothing beats a healthy, balanced diet to provide all the nutrients we need. But when this isn't possible, supplements can help. This article isn't intended to replace medical advice. Please consult your healthcare professional before trying supplements or herbal medicines.

B vitamins are needed for many different functions in the body, and are vital for energy production in cells.

Dr Sarah Brewer


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