The levels of manganese in some over-the-counterdietary supplements exceed US government recommended levels for safe consumption of the element, Reuters Health reports. Consuming too much manganese may cause abnormal neurological symptoms, such astremors, similar to those seen in Parkinson's disease patients, according to a report issued bythe Institute of Medicine, part of The National Academy of Sciences. In January 2001 US Institute of Medicine (IOM) announced that daily consumption ofmanganese from food, water and dietary supplements should not exceed the tolerable upperintake levels (UL) of 11 milligrams (mg) per day. Manganese is an essential nutrient involved in the formation of bone and the metabolism ofamino acids, lipids and carbohydrates. A deficiency in manganese can cause impairedgrowth and problems with reproductive function, and decreased blood levels have been seenin women with osteoporosis, according to the IOM report. Reuters Health was prompted to conduct its investigation after ConsumerLab.com of White Plains, New York posted a notice on its Web site on January 29th, stating that one of theproducts that it evaluates exceeded the UL for manganese. Of five dietary supplements purchased by Reuters Health, all exceed the UL for manganese. The US Food and Drug Administration does not regulate ingredients in supplements or dosage levels.