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Comment by mcculley | Hacker News Reader

I just gave blood today. I have been trying to give blood as often as possible (once every eight weeks) to help keep cholesterol and iron low. Now, of course, I'm getting a free COVID-19 antibody test out of the deal. I'm wondering if this frequency of blood donations has a similar effect.

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> "They replace half the blood volume in mice"

I'd speculate the difference in volume is too great, having half your blood replaced with saline solution must feel awful.

Not really the same thing but I'm blood type O- and do the "Power Red" donation at Red Cross events. I have two units of blood taken out and the red cells and plasma are separated so the plasma can be returned along with saline to make up the difference in volume. I don't notice much of a difference besides feeling a little cold since the saline is at room temperature. However in that case I believe I'd only have ~10% of my blood volume replaced with saline.

« I don't notice much of a difference besides feeling a little cold since the saline is at room temperature. »

I've always wondered: Why don't they warm it up?!

"half of the blood plasma" Important difference.

Interesting point by aomix about the temperature, but that could be compensated for if it was needed.

I haven't donated plasma in a long time, but pretty much the only thing I felt when the blood cells and platelets were returned was a light tickling near the needle and sometimes a faint chemical taste or smell, presumably from some component in the replacement fluid. Exchanging several liters would take time, certainly, but it doesn't seem at all a given that it would be very disagreeable in the immediate term.

Slightly longer term, one might certainly wonder about the comfort effects of having stuff like hormones and cytokines, circulating antibodies, clotting factors, etcetera rapidly halved. That ought to jolt the homeostatic controllers good, and that could well be one of the reasons for the beneficial effects. And halving blood glucose should be potentially unpleasant, but I suspect the compensation would be very fast.

> That ought to jolt the homeostatic controllers good, and that could well be one of the reasons for the beneficial effects

Indeed, I'm wondering if this is yet another example of eustress. Other examples of eustress are exercise, sauna, and cryotherapy.

Eustress, that's a new one. I thought that was called hormesis.

Ah thank you, I came across the term hormesis from Dr Rhonda Patrick’s work

Aside from the altruistic aspect, I had extra motivation to give blood from an unfounded pet theory that the body isn't capable of removing all bad products that ends up in the bloodstream. Giving blood seemed like a safer way to purge some of these products than diy at-home phlebotomy. It's nice to finally have some research supporting this guess.

I was wondering that too. But donating only takes about 10% of your blood. So maybe not enough for any effect?

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