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The immune system needs 9.5 hours of sleep in total darkness to recharge completely.
It is important to read food labels and choose foods with low cholesterol and saturated trans fat. You should limit saturated fat to no higher than 6% of daily calories.
The Babylonians wrote numbers in a system that used 60 as the base value rather than the number 10. They did not have a symbol for "zero."
HIV testing reach is still limited. An estimated 40% of people with HIV (more than 14 million) remain undiagnosed and do not know their infection status.
As the western states of America were settled, pioneers often had to drink rancid water from ponds and other sources. This often resulted in chronic diarrhea, causing many cases of dehydration and death that could have been avoided if clean water had been available.