That being true or not, I suspect giving blood is more likely a healthy than and an unhealthy thing to do, especially for men and non-menstruating women. And it certainly can save someone else's life.
As a matter of fact I would not be here if it hadn't been for a blood transfusion. $40 worth of blood from a cleaning lady named "Schramm". As a baby, all my blood had to be drained from my six week old body as a last resort, to be replaced with Frau Schramm's blood. I finally recovered from my severe anemia (ABO) after weeks of experiments - an eternity for my poor parents who had helplessly put my bassinet on Doctor Wolf's desk in Duisburg, Germany two months earlier. He had humbly warned them that he may not be able to return their baby to them alive.
Thank you, Dr. Wolf, and Thank You, Frau Schramm. Blood bank - here I come!