By Charnicia Huggins

NEW YORK, Aug 18 (Reuters) Many valerian-containing herbal sleep supplements do not contain as much of the key ingredient as needed to be effective or as much as the manufacturer claims, according to a ConsumerLab.com report on the topic. And some tested supplements were contaminated with cadmium or lead.

Valerian, a popular herb used as a sedative and calming agent, ''can help people with sleep problems,'' Dr Tod Cooperman, president of ConsumerLab.com said in a statement.

''Unfortunately, many marketed supplements don't match up to products that have been shown to work,'' he added.

Experts may not know the specific chemical components of the herb that make it effective, but valerenic acids have been previously associated with good quality valerian, according to the ConsumerLab report.

ConsumerLab.com determined the quality and quantity of valerian contained in many of the products available today.

Only four of 14 herbal supplements tested provided the amount of valerenic acids shown to be clinically effective, according to the ConsumerLab.com report.

Among the 10 products that failed testing, two supplements were contaminated with cadmium, which is known to cause cancer and is toxic to the kidneys.

Eight others did not contain as much valerian as expected.

Further, one of these eight supplements was also contaminated with lead, which can impair brain function and may have an affect on blood pressure as well.

Cooperman's advice: ''If you use valerian, choosing a product that passed ConsumerLab.com's testing should improve your odds of it being effective and free of contaminants.'' REUTERS AB BS1123