The story related in the OP rings false to me too.
For one thing (as another poster noted) in the U.S. you can only donate blood every 56 days, not six weeks as in the alleged case of the elderly man.
I have never heard of and can find no cases reported of symptomatic increased red blood cell mass (i.e. reactive polycythemia) as a result of regular blood donation that is halted. Long-term effects of blood donation have been studied without confirmation of any significant negative (or positive) health effects; the one cited in the OP hasn’t even come up on the radar screen.
What seems possible is that the elderly man had undiagnosed hemochromatosis which only came to light once he stopped regularly donating blood (a treatment for the condition). Not as dramatic as “Omigod, his regular blood donations turned him into a Blood-Donating Zombie For Life!!!”
I have two problems with the FOAF-style tale related in the OP. Passing along an undocumented story like this might tend to discourage people from regularly donating blood, if they think it could force them to do it for life.
Secondly, it once again illustrates a mindset that keeps popping up here on the Dope despite repeated attempts to drive a stake through its heart. A poster brings up a dubious story or proposition. Others express skepticism and cite their reasons. The original poster glosses over or ignores the objections and triumphantly says “You haven’t proved me wrong!”.
With tales like this, it’s the obligation of the claimant to show that they are correct, and once again that has not happened here.
Jackmannii M.D. (whose training included blood banking and hematology).
Even without the input of the doctor, we have two stories here to consider: We have the OP, and we have Elendir’s Heir, which present two very different scenarios. Moreover, the OP’s story is second-hand. Nevertheless, it is implying that the condition of the elderly gentleman neighbor of the OP’s oh-so-very-honest-never-would-ever-enhance-a-tail friend represents some kind of general nature of the human body. After all, that’s the title of the thread. So even if the elderly gentleman’s case were an undiagnosed disease, the apparent claim of the OP is askew. I’d go with the first hand information case of Elendir’s Heir as a the body’s natural tendency.
I’m not a doctor, but I do work in a medical field. I cannot count the number of educated, inelligent, trustworthy people who have recounted very confused tales of medical matters to me. Unless you have some background in medicine, it is very easy to get the wrong end of the stick, especially as doctors and nurses often have limited time to convey very complicated information and sometimes fail to realise how little their patients are understanding.
Crawlspace mentioned homeostasis upthread. That’s the process by which human biology regulates a huge number of of processes, including haemoglobin levels. What happens is that the body has a setpoint and tries to keep the haemoglobin at that level. If the level goes too low (say after a blood donation), more of a hormone called erythropoetin is produced, and that in turn causes more red blood cells to be made. If the level gets a bit too high, erythropoetin production gets turned down and fewer red blood cells get made.
If homeostasis was working correctly for your FOAF, it doesn’t matter how regularly he’d donated blood, or for how long, if his haemoglobin levels got too high, his body should have slowed up producing red blood cells until it got back to the normal level.
It seems very plausible to me that he had undiagnosed haemochromatosis. Iron levels build up slowly and it’s usually gets diagnosed when people are in their forties. If he had regularly donated blood from well before then, his levels of iron wouldn’t have built up and his lab results would have been normal or near to normal. Genetic testing could have shown it, but there would have been no reason for anyone to suspect it, so no reason to do the genetic test.
It also seems possible he had developed polycythaemia, but I think it’s less likely than him co-incidentally developing the disease, but having it masked by his regular blood donations. However if he did develop it because of the donations, frankly I’d still see it as a failure of homeostasis and therefore an example of a human body actually being worse than usual at adapting to a situation.