University of British Columbia chemistry professor David Dolphin has a hypothesis about the origin of vampire folklore. He is an expert on porphyrins, which are ring-shaped metal-binding molecules. The best-known porphyrin is heme, which binds iron and, when complexed with the protein hemoglobin, transports oxygen. Porphyria is a family of inherited disorders caused by faulty heme production. People with the cutaneous type of porphyria are acutely sensitive to sunlight, a trait often ascribed to vampires. And there are other possible connections to vampirism, as Dolphin explained in a recent presentation :
Dr. Dolphin admits it’s only a theory but drinking blood would have allowed them to absorb more heme, which feeds back to ease up on excess porphyrin production. In fact, porphyria patients today get heme injections. Porphyrin build-up in teeth can make them appear reddish, possibly like bloody fangs. The disease is even associated with excess hair growth, especially on the forehead, possibly leading to the vampire’s trademark widow’s peak. The aversion to garlic may be explained by the fact that some chemicals in the plant, such as diallyl sulfone, increase the production of porphyrins in the body. Of course, he points out, that a wooden stake through the heart would kill anyone. As for the lack of a mirror image, Dolphin joked, “I’m a chemist, so I’ll leave that to the physicists.”While it's an interesting proposal, the Straight Dope takes a much more skeptical view:
(1) Porphyria comprises seven separate disorders. Skin problems are a fairly common symptom, but only the rarest form--congenital erythropoietic porphyria--causes severe disfigurement. Just 200 cases of this disease have been diagnosed, surely too few to account for the widespread belief in vampires. In any case, alleged vampires exhumed in the 18th century typically weren't disfigured but appeared as they had in life (except for being dead, of course).When the Straight Dope wrote the article in 1999, they asked Dolphin for comment:
(2) The idea that vampires abhor sunlight was an invention of fiction writers. In Europe during the 18th and 19th centuries, vampires were sometimes reported to have been sighted during the day. Bram Stoker's Dracula was deathly pale, but folkloric vampires, in the Balkans anyway, were said to be ruddy-faced due to blood consumption.
(3) Porphyria victims don't crave blood. Drinking blood will not alleviate their symptoms, nor has there ever been a general belief that it would. The blood chemicals porphyria victims need do not survive digestion.
(4) In light of the preceding, the scenario described in point #4 above [Porphyria symptoms can be brought on by stress - being bit by a sibling who also has the disease is stressful - the bite "causes" you to turn into a biter too] is unlikely.
(5) No one has proved that garlic worsens porphyria.
When I phoned, he didn't wish to speak to me and would say only that "it was just speculation" and that "I haven't worked in this area for many years."The response is a bit amusing in light of the fact that he lectured on the topic a just a few months ago. I guess the idea was just too interesting to give up.
Heme molecule via Dr. Karl Harrison's Chemistry, Structures and 3D Molecules site.