BBC correspondent Nicola Carslaw: "Three million women swear by vitamin B6"

Last year the government planned to restrict the sale of the supplement to 10mg per day.

In the past it had advised that taking too much of the vitamin could lead to nerve damage.

However, it put the plans on hold following strong opposition from the health food lobby.

The new finding adds weight to the campaigners' arguments, even though the researchers say further studies are needed before they reach a solid conclusion.

Millions take the pills

At present three million Britons take daily doses of Vitamin B6 up to 200mg. Two million women use the vitamin in high doses to combat pre-menstrual syndrome, alleviate morning sickness and the side-effects of the pill.

More than one million men take it to fight stress and increase energy. B6 is also used in conjunction with magnesium to treat autism.

The researchers from North Staffordshire Hospital and Keele University looked at the results of previously conducted trials.

In total, they looked at nine studies that involved nearly 1,000 women. The women took either vitamin B6 or a dummy pill.

Twice as effective

Analysis of the various findings showed that B6 was twice as effective as the placebo in relieving pre-menstrual syndrome.

The research also found that very high daily doses - 600mg for instance - were no more beneficial than lower ones and they recommend that women who want to treat their symptoms should start off with around 50mg a day and take no more than 100.

The investigators, led by Dr Katrina Wyatt, said: "Results suggest that doses of vitamin B6 up to 100mg/day are likely to be of benefit in treating pre-menstrual symptoms and pre-menstrual depression."

They published their study in the British Medical Journal.

Study 'confirms women's beliefs'

Dr Wyatt told BBC News Online: "We think that this will confirm the belief of many women that there may be some benefit in treating premenstrual symptoms with vitamin B6.

"Our study has added together all the existing trials and come out with an overall result indicating that 50-100 mg per day of vitamin B6 may be a useful treatment for PMS.

"Unfortunately, the low quality of the trials make a definitive clinical recommendation impossible

She added that their study "found no evidence of neurological side effects from vitamin B6 at doses of 50-100mg".

"We now believe there is good evidence to support the funding of a national trial of vitamin B6 in the treatment of PMS, the results of which will allow us to make a definitive recommendation," she said.

Restrictions planned

Last year, in the face of campaigning from the health food industry and consumers, the government postponed plans to limit the free sale of Vitamin B6 to 10mg a day pending further scientific investigations into into its long-term safety.

The government plans had originally come about following a report from the committee on Toxicity of Chemicals in Food, Consumer Products and the Environment Department of Health group.

It recommended that an excess of Vitamin B6 could damage the nervous system, leading to a loss of sensation in the hands and feet as well as permanent nerve damage.

The issue is now being examined by the Expert Group on Vitamins and Minerals, which could take up to two years to report back.

Meanwhile, the government continues to rely on the earlier scientific findings and recommend that nobody take more than 10mg a day.

Gareth Zeal, of the Vitamin B6 Campaign, said vitamin B had also been shown to reduce the risk of heart disease.

He said: "It should be freely available for people who want to help their own health."