As discussed in The Cholesterol Myths (see sidebar), much evidence supports the theory that people born with very high cholesterol, so-called familial hypercholesterolemia, are protected against infection. But if inborn high cholesterol protects against infections, inborn low cholesterol should have the opposite effect. Indeed, this seems to be true.
Children with the Smith-Lemli-Opitz syndrome have very low cholesterol because the enzyme that is necessary for the last step in the body’s synthesis of cholesterol does not function properly. Most children with this syndrome are either stillborn or they die early because of serious malformations of the central nervous system. Those who survive are imbecile, they have extremely low cholesterol and suffer from frequent and severe infections. However, if their diet is supplemented with pure cholesterol or extra eggs, their cholesterol goes up and their bouts of infection become less serious and less frequent.14