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There are over 65,000 known species of protozoa. About 10,000 species are parasitic.
When blood is deoxygenated and flowing back to the heart through the veins, it is dark reddish-blue in color. Blood in the arteries that is oxygenated and flowing out to the body is bright red. Whereas arterial blood comes out in spurts, venous blood flows.
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.
Throughout history, plants containing cardiac steroids have been used as heart drugs and as poisons (e.g., in arrows used in combat), emetics, and diuretics.
People with alcoholism are at a much greater risk of malnutrition than are other people and usually exhibit low levels of most vitamins (especially folic acid). This is because alcohol often takes the place of 50% of their daily intake of calories, with little nutritional value contained in it.