BBC News' Karen Bowerman: Health food store staff are not required to be trained before giving advice

Which? magazine sent undercover researchers into 30 shops in five areas of the country, including London.

They asked questions about remedies for indigestion and anxiety.

When confronted with someone over 40 who has experienced indigestion and weight loss for the first time, staff should tell the customer to visit a GP to rule out more serious causes such as ulcer or stomach cancer.

And before handing out Kava, a natural remedy for anxiety, an assistant should ask whether the customer is taking tranquilisers, to avoid the dangerous side-effects that could be caused by mixing the drugs.

But in the Which? study, only a few stores offered good advice.

In 11 out of 15 shops visited for indigestion, either no advice, or the wrong advice was offered.

And in six out of 15 asked about anxiety, Kava was sold with no questions about conventional medication.

Serious side-effects

And at one shop, when the researcher said that she was taking conventional tranqulisers, she was advised to stop, despite the fact that sudden withdrawal of such medication can cause serious side-effects.

In an editorial, Which? magazine called for basic training for all staff to be made a legal requirement.

It added: "Generally, the staff in the health food shops we visited failed to ask the necessary basic questions about existing medical conditions."

Most of the stores surveyed were small, independent outlets, rather than major chains such as Holland and Barrett.

A spokesman for Holland and Barrett said that all its staff underwent a comprehensive training programme.

Checking on staff

"We do a considerable amount of secret surveying of staff ourselves," she said.

"We would always refer customers to a doctor if it is not a very straightforward inquiry."

Holland and Barrett would support any moves to introduce mandatory training for all health food shop assistants, she said.

There are more than 2,000 health food shops in the UK.

Dr Paul Davis talking on the BBC's One O'Clock News

Dr Paul Davis, from the Royal College of General Practitioners, said that pregnant women, or people with heart problems or epilepsy should be particularly careful when buying from health shops.

He said: "Some of these (remedies) are potentially able to affect the unborn baby, and disastrous effects could occur".

He recommended that shop assistants should refer people back to their GPs where there was any doubt about the advice they could give.

The government has indicated that increased regulation of the herbal medicine industry is likely, first through controls on vitamin B6, then by changes to rules on the future licensing of remedies.