New Body, New Diseases
There is a comfortable assumption running under all superhero fiction that a powerful physiology is a healthy one. It is exactly backwards. Novel machinery means novel failure modes, and the failure modes of a system nobody has seen before are, by definition, ones nobody knows how to recognise.
Take regeneration. A body that rebuilds itself has, as we have seen, solved the cancer problem somehow — but "solved" in biology never means "abolished", it means "suppressed to an acceptable rate by mechanisms that can themselves fail". A regenerating superhuman who develops a malignancy would develop a very peculiar one: fast, possibly capable of the same regenerative tricks as the rest of him, and resistant to the treatments that work by outpacing ordinary cell division. His healing factor and his tumour would be, in effect, competing with each other, and there is no oncology for that.
Take metabolism. A body that can release energy at extraordinary rates has an endocrine system controlling the release, and endocrine systems fail in characteristic ways: too much, too little, at the wrong time, or in response to the wrong signal. A thyroid storm in an ordinary person is a medical emergency with a mortality rate. What is the equivalent for someone whose metabolic ceiling is a hundred times higher? Presumably something that cooks him from the inside in a matter of minutes, and presents at triage as a young man who is confused and very hot.
Take an unusual immune system. Enhanced immunity is not a free good; the immune system's problem has never been strength but discrimination, and the more aggressive the response the more important the ability to distinguish self from non-self. Autoimmune disease is the price we already pay for the immune system we have. An enhanced one would have enhanced errors, and the target would probably be the novel tissue, because novel tissue is exactly what an immune system is most likely to fail to recognise. There is a particularly horrible version of this: a man whose body decides, at thirty-four, that his own extraordinary organ is foreign.
from How to Think Seriously About Superheroes (2026)
