5β-coprostanol is formed by the conversion of cholesterol to coprostanol in the gut of most higher animals by intestinal bacteria. It is generally accepted that the metabolism of cholesterol to coprostanol by gut bacteria proceeds in an indirect manner via ketone intermediates, rather than direct reduction of the Δ double bond. be seen in the figure proposed by Grimalt et al., (1990). 
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There are a small number of animals, however, that have been shown not to produce 5β-coprostanol and these can be seen in the table.