Vitamin B is divided into several subgroups numbered 1, 2, 3, 5, 6, 9 and 12. All are water-soluble and occur in dairy products, meats and leafy vegetables. Vitamin B1 has the chemical name of thiamine, B2 is riboflavine and B5 is pantothenic acid. Vitamin B6 (pyridoxine) may be useful in mouth inflammation, morning sickness and nervous tension. Vitamin B9 is an alternative name for folic acid. Vitamin B12 (cyanocobalamin or hydroxocobalamin) is used as an injection to treat pernicious anaemia. Nicotinic acid (vitamin B3) is specifically found in peanuts, meat, grain and liver. It is used in the treatment of certain types of headache, nervous disorders, poor circulation and blood diseases.
The amount of the various vitamins B in blood can be measured. The normal values are:-
- Vitamin B1
Male 8.9 µg/100 mL
Female 7.6 µg/100 mL
- Vitamin B2 2.6 to 3.7 µg/100 mL
- Vitamin B3 Average 0.6 mg/100 mL
- Vitamin B12 150 to 660 pmol/L (200 to 900 ng/mL)
It is almost impossible to have a lack of only one in the group. If one is missing, several will usually be missing. A lack of vitamin B may cause anaemia and other blood diseases. Beriberi is caused by a lack of vitamin B1, and pellagra by a lack of vitamin B3, while pernicious anaemia is due to a lack of vitamin B12. A lack of vitamin B6 (pyridoxine) may be an uncommon side effect of some medications (eg. isoniazid, penicillamine), genetic disorders and in poor nutrition. It causes epileptic like seizures, dermatitis, mouth sores and dryness, vomiting, weakness and dizziness. The blood levels of pyridoxine can be measured to confirm the diagnosis, which is easily corrected by vitamin B6 supplements.
Excessive blood levels of any of the B group vitamins may be due to taking too many vitamin B supplements. Usually there are no serious effects as excess passes out in the urine. Very high doses of pyridoxine (vitamin B6) may cause nerve damage and poor coordination, numbness around the mouth, clumsiness, muscle weakness and loss of position sense. Very high doses of niacin (vitamin B3) may cause severe flushing, itchy skin, diarrhoea and liver damage. Long-term complications are uncommon.