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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
Human stomach acid is strong enough to dissolve small pieces of metal such as razor blades or staples.
The average adult has about 21 square feet of skin.
According to the CDC, approximately 31.7% of the U.S. population has high low-density lipoprotein (LDL) or "bad cholesterol" levels.
Human kidneys will clean about 1 million gallons of blood in an average lifetime.
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