NEW YORK (Reuters Health) - Some vitamin B supplements may contain more than the recommended amount of the nutrients, according to a new report by ConsumerLab.com.

ConsumerLab.com, a commercial testing company in White Plains, New York, conducted the study. For a fee, the company licenses its flask-shaped ``Seal of Approved Quality'' to companies whose products pass testing.

``Consumers should be aware that more than 40% of the products that we evaluated exceeded levels at which they are known to be safely tolerated--some having more than 10 times the upper limit,'' said Dr. Tod Cooperman, ConsumerLab.com's president, in a prepared statement from the company.

ConsumerLab.com tested 21 B vitamin supplement products. Some contained a single dose of a particular B vitamin while others included several. The eight B vitamins are thiamine (B-1), riboflavin (B-2), niacin (B-3), pantothenic acid (B-5), pyridoxine (B-6), cyanocobalamin (B-12), folic acid (folate) and biotin.

Nine of the 21 products exceeded established Tolerable Upper Intake Levels (ULs) for adults--''above which there is increased risk for side effects with regular use,'' according to the report.

ULs are established by the Institute of Medicine of the National Academies.

The report notes that three of the niacin-only products exceeded the UL for niacin as did six of the seven B complex products. The UL for niacin is 35 milligrams (mg), while these products included recommended daily doses ranging from 400 mg to 510 mg.

``There may be good medical reasons for exceeding these levels, but there may also be significant side effects,'' Cooperman warns. ``People interested in using high doses of B vitamins should consult with a healthcare professional.''

In addition to those findings, ConsumerLab.com reports that one of the B complex products contained amounts of the nutrients lower than what was stated on the label.

The findings underscore the fact that vitamin supplements may benefit from tighter regulation.

Vitamin B dietary supplements are becoming increasingly popular due to last year's decision by the US Food and Drug Administration to allow manufacturers to tout recent findings about the ability of B vitamins to reduce vascular disease risk.

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