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The average human gut is home to perhaps 500 to 1,000 different species of bacteria.
Vaccines prevent between 2.5 and 4 million deaths every year.
It is difficult to obtain enough calcium without consuming milk or other dairy foods.
More than 4.4billion prescriptions were dispensed within the United States in 2016.
People about to have surgery must tell their health care providers about all supplements they take.
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