London - If you are suffering from a cold, read this before reaching for the orange juice. Consuming vitamin C does little to help your symptoms, a new study suggests.

It found that washing your hands is one of the best defences against the common cold – while zinc tablets can also prevent it.

But they dismiss vitamin C supplements as having no effect.

The new review – looking at medical and non-medical remedies to prevent and treat the common cold – also shows natural remedies often suggested for winter bugs have little evidence supporting them.

Ginseng, gargling, vapour rubs and homeopathy have “unclear” benefits, according to a review published in the Canadian Medical Association Journal.

Antibiotics were also ineffective, because they only work on bacteria when colds are caused by viral infections.

Adults can expect to suffer between two and five colds a year, although they don’t always lead to symptoms.

Symptoms such as sore throat, stuffy or runny nose, cough and malaise are usually worse for the first three days but can last up to three weeks.

A new review by Dr Michael Allan, of the University of Alberta in Canada, and Dr Bruce Arroll, of the University of Auckland, New Zealand, concludes that clean hands, with alcohol rubs and gloves, is the best prevention based on findings from 67 trials.

Zinc supplements of 10 or 15mg a day works for children, resulting in lower rates of colds and less time off school caused by colds, they say.

The doctors believe the evidence suggests adults would also benefit from taking zinc.

Researchers also found paracetamol, ibuprofen and perhaps antihistamine-decongestant combinations are among the best treatments for a cold.

Dr Allan said: “Although self-limiting, the common cold is highly prevalent and may be debilitating. It causes declines in function and productivity at work and may affect other activities such as driving.”

Just five percent of clinically diagnosed colds involve a bacterial infection, yet antibiotics are sometimes used inappropriately for viral infections, said Allan.

Misused antibiotics can be harmful, he added.

The researchers said there is some evidence that probiotics – supplements containing “friendly” bugs – may help prevent colds, although the types and the combinations of organisms varied in the studies as did the formulations, making comparison difficult.

Antihistamines combined with decongestants and/or pain medications appear to be somewhat or moderately effective in treating colds in older children – but not in children under the age of five – and adults.

Ibuprofen and paracetamol help with pain and fever, although ibuprofen appears better for fever in children.

Ipratropium, a drug used to treat allergies and chronic obstructive pulmonary disorder, may alleviate a runny nose when used in a nasal spray but has no effect on congestion.

Cough medicines show no benefit in children, but may offer slight benefit in adults, while honey has a slight effect in relieving cough symptoms in children over the age of one.

The long-held belief that vitamin C assists in preventing and treating colds, like other so-called remedies, largely comes from research studies of poor quality and inconsistent results, says the review.

Allan said: “Much more evidence now exists in this area, but many uncertainties remain regarding interventions to prevent and treat the common cold.

“We focused on randomised controlled trials and systematic reviews and meta-analyses of trials for therapy, but few of the studies had a low risk of bias.

“However, many of the results were inconsistent and had small effects – for example, vitamin C – which arouses suspicion that any noted benefit may represent bias rather than a true effect.” – Daily Mail