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Vitamin B6: a B-complex vitamin unlike any other
Vitamin B6 is the generic name for three related compounds (pyridoxine, pyridoxal and pyridoxamine) which the body converts into a single active form, pyridoxal phosphate.
In this form, it acts as a cofactor in over a hundred enzymatic reactions, mainly related to amino acid metabolism. It is one of the most versatile B vitamins, and this is reflected in the wide range of its recognised functions.
Vitamin B6 contributes to normal energy metabolism, the normal functioning of the nervous system, normal homocysteine metabolism, normal protein and glycogen metabolism, normal psychological functions, the normal formation of red blood cells, the normal functioning of the immune system, the reduction of fatigue and the regulation of hormonal activity.
However, it differs from its B-group cousins in one specific respect, and this point forms the basis of this entire article: it is the only water-soluble vitamin for which toxicity due to excess intake has been clearly established. We will return to this in detail, as it is the most useful piece of information you can take away about it.
Recommended intakes
The nutritional reference value is around 1.7 mg per day for an adult man and 1.6 mg for a woman. These are small amounts, easily met by a varied diet.
Requirements increase with protein intake, as vitamin B6 plays a role in protein metabolism. A high-protein diet (common amongst bodybuilders) therefore naturally leads to slightly higher requirements, which are generally met by the additional food intake that such a diet entails.
Pregnancy, breastfeeding and advancing age are other situations where requirements are increased.
Vitamin B6 and magnesium: why this combination
This is one of the most common combinations in supplementation, and it is not merely a marketing ploy.
Magnesium carries out most of its functions inside cells. Vitamin B6, however, promotes its entry into and retention within the intracellular compartment. A magnesium intake accompanied by B6 therefore results in more efficient cellular utilisation than a magnesium intake on its own.
The logic works both ways: magnesium, for its part, helps convert vitamin B6 into its active form. Each facilitates the action of the other.
This synergy explains why the pair is routinely included in formulations designed to address stress, nervousness, fatigue and nervous system comfort – two areas in which both nutrients have recognised functions. These combined formulations can be found in the B-complex category.
One point to bear in mind, which few people realise, is that because this combination is so common, it is easy to end up taking multiple sources of B6 without realising it; a magnesium-B6 complex, a multivitamin and a pre-workout formula may each contain it. We’ll see in a moment why this accumulation deserves more than just a shrug.
Vitamin B6 deficiency: rare but real
An isolated B6 deficiency is uncommon in countries where people have a varied diet. When it does occur, it is usually due to specific circumstances rather than simply an insufficient intake.
The symptoms described are:
- unusualtiredness and irritability
- skin lesions, notably seborrhoeic dermatitis and cracks at the corners of the mouth
- inflammation of the tongue and oral mucosa
- tingling or numbness in the extremities
- anaemia, as vitamin B6 is required for the synthesis of haemoglobin
- a weakened immune system
Conditions that increase the risk of this deficiency: chronic alcohol consumption, kidney disease, autoimmune diseases, and, in particular, certain medications (isoniazid, penicillamine, certain anti-epileptic drugs) that directly interfere with the metabolism of the vitamin.
One point to note: anaemia linked to a B6 deficiency is microcytic, with small red blood cells, whereas anaemia linked to vitamins B9 and B12 is macrocytic. This distinction, visible on a blood count, helps the doctor to guide their reasoning and illustrates why the diagnosis of fatigue cannot be made on the basis of clinical judgement alone.
Excess vitamin B6: the real cause for concern
Here is the information that sets this vitamin apart from all the others in the B group, and which alone justifies reading this article.
It is often said that water-soluble vitamins are safe even in excess, as the kidneys eliminate any surplus. This is true for B12, B9 and vitamin C. It is not true for B6.
High and prolonged intakes of vitamin B6 can cause peripheral neuropathy: damage to the nerves in the hands and feet, manifesting as tingling, numbness, pain and coordination problems.
This phenomenon is all the more confusing as these symptoms resemble those of a deficiency. A person who experiences tingling and increases their B6 intake to remedy it may therefore actually worsen the very condition they are trying to correct.
The upper safe limit has been revised downwards by the EFSA to 12 mg per day for adults. This is a low threshold, and it is easily reached: many supplements contain doses of vitamin B6 that far exceed actual requirements.
The practical approach consists of three steps: add up the B6 content of all your products, including combination formulas and fortified drinks; do not exceed the doses stated on the labels; and if you experience tingling whilst taking supplements, speak to your doctor rather than increasing the dose.
Rest assured on one point: it is impossible to reach these levels through diet alone. The risk relates exclusively to supplementation.
Where to find vitamin B6
Unlike vitamin B12, which is found almost exclusively in animal products, vitamin B6 is widely distributed across both plant and animal sources, which explains why deficiencies are rare.
The best sources are poultry and fish, particularly salmon and tuna, offal, potatoes, pulses (chickpeas in particular), bananas, oilseeds and whole grains.
Two key preparation techniques help to preserve these nutrients: as vitamin B6 is heat-sensitive and water-soluble, gentle cooking methods and saving the cooking juices prevent significant losses. Furthermore, refining cereals removes a significant portion of these nutrients, giving wholegrain varieties a clear advantage.
Frequently asked questions
Why combine vitamin B6 and magnesium?
Because vitamin B6 helps magnesium enter cells, where it carries out its functions. A magnesium supplement taken alongside vitamin B6 is therefore utilised more effectively than one taken on its own.
The reverse is also true: magnesium helps convert vitamin B6 into its active form. The two nutrients also have recognised shared functions relating to fatigue and the nervous system, which explains why they are routinely included in formulations designed to combat stress.
What is the recommended daily dose of vitamin B6?
The nutritional reference value is around 1.6 to 1.7 mg per day for adults, and the upper safe limit set by the EFSA is 12 mg per day.
The gap between the two may seem comfortable, but it is quickly bridged: many supplements contain doses significantly higher than required. A useful habit is to add up all your sources before introducing a new one.
Can vitamin B6 be dangerous?
Yes, at high doses and over a prolonged period, and this is what sets it apart from the other B vitamins. It can cause peripheral neuropathy, tingling, numbness and coordination problems.
The pitfall lies in the similarity of these symptoms to those of a deficiency, which can lead to people increasing their doses rather than reducing them. This risk applies only to supplementation: it is not possible to reach these levels through diet alone.
Does vitamin B6 help with stress?
It contributes to normal psychological functions, the normal functioning of the nervous system and the reduction of fatigue. These are recognised claims, and they justify its inclusion in formulations designed to support nervous system balance.
We must remain cautious about the scope of these claims: contributing to the normal functioning of the nervous system is not the same as treating a state of stress. Long-term stress requires a more comprehensive approach than simply taking supplements.
Should B6 be taken on its own or as part of a complex?
A complex is generally a more sensible choice, as the B vitamins work in synergy: B6, B9 and B12 are all involved in homocysteine metabolism, and a high, isolated intake of just one of them can upset the balance of the whole system.
High-dose B6 on its own is justified in specific situations, usually identified by a doctor. For maintenance purposes, our selection of the best B-vitamin supplements features the comprehensive formulations available.
Three things to remember about this vitamin: it has numerous functions and deficiencies are rare; the combination with magnesium is based on a genuine physiological mechanism rather than a marketing claim; and it is the only water-soluble vitamin for which prolonged excess poses a documented problem. This last one is the least well-known of the three, and it is probably the one that will be most useful to you.