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12 February 2007

The nervous system: Other B-vitamins

In this article, DietDoc explores the effects of important members of the B-complex vitamins on the health of the central nervous system (CNS).

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In this article, DietDoc explores the effects of important members of the B-complex vitamins on the health of the central nervous system (CNS).

Pyridoxine
Pyridoxine, or vitamin B6, is essential for the synthesis or metabolism of practically all the neurotransmitters (chemicals which help to transmit messages in the CNS).

A deficiency of pyridoxine causes symptoms such as tiredness, nervousness, irritability, depression, insomnia, and difficulty with walking. In addition, dizziness, neuritis, neuralgia and carpal tunnel syndrome (loss of feeling or pins and needles in the hands caused by swelling of connective tissue in the wrist which presses on nerves) are linked to a vitamin B6 deficiency.

Long-term use of anticonvulsants containing phenytoin or succinimide may reduce blood levels of pyridoxine. Antidepressant drugs, monoamine oxidase (MAO) inhibitors, antihypertensive drugs, anticancer drugs, oral contraceptives, and anti-TB drugs, may also lower pyridoxine levels in the blood and cause irritability, peripheral neuropathy and convulsions.

A pyridoxine supplement is used to treat diet- and drug-related pyridoxine deficiency. It is important to adhere to the dose prescribed by your doctor as overdoses of pyridoxine may cause memory loss.

Rich dietary sources of pyridoxine include:

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  • Meat, fish, potatoes, bananas and legumes (dry beans, peas, lentils and soy products).

Vitamin B12
In addition to preventing so-called pernicious anaemia, vitamin B12 or cyanocobalamin is essential for the maintenance of myelin (a component of the CNS). Inadequate synthesis of myelin leads to neurological damage.

A vitamin B12 deficiency in breastfeeding mothers (e.g. those eating a strict vegan diet) can expose infants to brain atrophy, myoclonic seizure disorder, microencephaly and cortical blindness, which may be irreversible in some cases.

Patients with pernicious anaemia may develop loss of cognitive function and even dementia, unless they receive supplementary vitamin B12. Down syndrome patients often have an inability to absorb vitamin B12 and suffer from lowered B12 status. Treatment of vitamin B12 deficiency is achieved by injections and/or use of oral supplements in conjunction with the so-called intrinsic factor (a compound produced by the stomach which aids absorption of B12).

Vitamin B12 is exclusively found in foods derived from animals, like liver, red meat, poultry, fish, eggs, milk and dairy products.

Folic acid
Deficiency of folic acid or folate is associated with anaemia and neuropathy in adults, but the most serious neurological sequelae of a maternal folic acid deficiency are neural tube defects such as spina bifida in the newborn.

It is estimated that 5-10% of the population suffer from deficiencies of folic acid due to inadequate dietary intake. Malabsorption conditions, such as coeliac disease and sprue can also lead to low folate reserves.

Folate deficiency in pregnancy is common and has prompted the recommendation that women should ingest 400 micrograms of folate a day for three months before conception and for the entire course of pregnancy.

In countries where folate supplementation is prescribed during pregnancy and staple foods are fortified with folate, the incidence of neural tube defects has decreased dramatically. In South Africa, bread flour and maize meal are increasingly being fortified with folate, which should help to prevent these birth defects.

Folate deficiency may also be caused by the use of anticonvulsants and chronic abuse of alcohol.

Folate supplements are usually prescribed to prevent neural tube defects and folate-deficiency anaemia of pregnancy.

The following foods are good sources of folate:

Liver, fresh vegetables, and fortified staple foods such as bread and maize meal.

Biotin
Although biotin deficiencies are rare in humans, a lack of biotin can cause fatigue, nausea, anorexia, muscle pains and loss of feeling in the hands and feet. Use of anticonvulsants may reduce biotin levels in the blood and some doctors advocate the use of a concomitant biotin supplement for patients receiving anticonvulsants.

Good dietary sources of biotin include:
Liver, cooked egg yolk, soy flour, cereals and yeast.

Conclusion
The B-complex vitamins (thiamine, riboflavin, niacin, pyridoxine, vitamin B12, folic acid and biotin) play an important role in keeping the brain and nervous system healthy. Most of these B-vitamins are also essential during pregnancy to ensure that the brain and nervous system of the foetus develop properly.

If you suffer from symptoms such as tiredness, irritability, depression or nervousness, it may be a good idea to take a B-complex supplement. Patients on anticonvulsant therapy are at risk of developing multiple B-vitamin deficiencies and will benefit from taking a B-complex supplement. If you are on any kind of chronic medication, ask your doctor if you need to supplement your vitamin B intake.

Individuals eating an unbalanced or deficient diet also need to consider taking a B-complex supplement to prevent neurological symptoms associated with vitamin B deficiencies. Also select foods that are rich in B-vitamins and use bread and maize meal that have been fortified with B-vitamins to boost your daily intake. – (Dr I.V. van Heerden, DietDoc)

Any questions? Ask DietDoc

 
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