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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
An identified risk factor for osteoporosis is the intake of excessive amounts of vitamin A. Dietary intake of approximately double the recommended daily amount of vitamin A, by women, has been shown to reduce bone mineral density and increase the chances for hip fractures compared with women who consumed the recommended daily amount (or less) of vitamin A.
Normal urine is sterile. It contains fluids, salts, and waste products. It is free of bacteria, viruses, and fungi.
Cytomegalovirus affects nearly the same amount of newborns every year as Down syndrome.
The heart is located in the center of the chest, with part of it tipped slightly so that it taps against the left side of the chest.