More than one million people, mainly women, are said to use B6 - some swallowing a gobstopper size daily dose. It is taken for problems as diverse as premenstrual tension, acne and sickle cell anaemia but scientists on the health department's Committee on Toxicity of Chemicals in Food warned last August that large doses taken over a long period could cause nerve damage.
The vitamin industry reacted with commendable speed, establishing a lobbying group and mobilising health conscious customers everywhere to write protest letters to their MPs. More than 110,000 letters were received and the Agriculture Committee felt it expedient to set up an inquiry.
Its report makes uncomfortable reading for the COT scientists who are accused of being "curt to the point of rudeness" and producing a report that is "scientifically unjustifiable," and "palpably wrong".
Now I hold no brief for ill-mannered scientists. But it is the content of expert advice that I value. And if I am forced to choose between a bunch of MPs with a couple of science O-levels between them and a committee of experts with years of research experience, I don't have much difficulty deciding whose advice I prefer.
Moreover, what for me is the key conclusion in the Agriculture Committee's report seems to have been largely overlooked - that the evidence that vitamin B6 confers benefit on those who take it is "inconclusive." The committee is absolutely straight about this. "Many consumers may experience a placebo effect rather than any actual health benefit," it says.
This would not be surprising. Vitamin B6 is found in a wide variety of foods including cereals, potatoes, meat, milk and beer and is essential for breaking down protein for use by the body. However, the recommended daily requirement is a modest 1.6mgs for adult women and 1.4mgs for adult men. Thus even the 10mg dose that will still be available on free sale under the government's proposed restrictions is over five times the daily amount most people need and should be enough to deal with a sackload of protein. .
The most surprising aspect of the row is the modesty of the Government proposal that has provoked it. We are not talking of a ban on vitamin B6 here, merely a restriction of its free sale to 10 mg tablets over the counter and up to 49 mgs from pharmacies.
The COT scientists have kept their own counsel since the Agriculture Committee reported but are said to be livid about the criticisms. They say there was not one study which swayed them, , but a whole series which all pointed in the same direction - to evidence of harmful effects when the vitamin is taken in excess of 50 mgs daily for months or years. The row has left consumers perplexed and Jeff Rooker, the Food Safety Minister, with a conundrum. Whatever policy he now announces is certain to be attacked.