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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
For about 100 years, scientists thought that peptic ulcers were caused by stress, spicy food, and alcohol. Later, researchers added stomach acid to the list of causes and began treating ulcers with antacids. Now it is known that peptic ulcers are predominantly caused by Helicobacter pylori, a spiral-shaped bacterium that normally exist in the stomach.
It is difficult to obtain enough calcium without consuming milk or other dairy foods.
About 3% of all pregnant women will give birth to twins, which is an increase in rate of nearly 60% since the early 1980s.
In 2006, a generic antinausea drug named ondansetron was approved. It is used to stop nausea and vomiting associated with surgery, chemotherapy, and radiation therapy.