Some Amish are afflicted by genetic disorders, including dwarfism, and are also distinguished by the highest incidence of twinning in a known human population, various metabolic disorders and unusual distribution of blood-types. Since almost all of the current Amish descend primarily from about 200 founders in the 18th century, some genetic disorders from a degree of in-breeding exist in more isolated districts. However, Amish do not represent a single closed community, but rather a collection of different genetically closed communities. Some of these disorders are quite rare, or even unique, and serious enough that they increase the mortality rate among Amish children.

Maple Syrup Urine Disease is a genetic disorder characterized by an infant with sweet-smelling urine with an odor similar to that of maple syrup. Infants with this disease seem healthy at birth but if left untreated suffer severe brain damage and eventually die. Maple Syrup Urine Disease is caused by a deficiency of a certain metabolic enzyme. The deficiency leads to a toxic buildup of branched-chain amino acids (leucine, isoleucine, and valine) in the blood and urine.

An average human male's digestive system, consisting of the mouth, pharynx, esophagus, stomach, small intestine, large intestine, rectum, and anus is approximately 20 feet (6.5 meters) long from end to end.

Bile acids, one of the key components of bile, are produced by the liver and are used by the body to emulsify fat in the intestines. They are produced in the liver by the oxidation of cholesterol, and are stored in the gallbladder until the stomach releases its partially digested food. Synthesis of bile acids is a major consumer of cholesterol. The average body synthesizes about 800 mg of cholesterol per day and about half of that is used for bile acid synthesis. In total about 20-30 grams of bile acids are secreted into the intestine daily. About 90% the excreted bile acids are later reabsorbed further down the intestines to be reused.

Other than humans, almost all mammals have a penis bone, or baculum. Other species that are do not have this bone are horses, marsupials, rabbits, hyenas, and a few others. Most other primates, our closest relatives, are born with a penis bone.