Doctors were stumped recently when they found a woman and her father both had a rare genetic mutation that causes anemia, yet only the woman showed signs of actually being anemic. Why had her father escaped this fate? Because he's a smoker, as it turns out.Hold your applause; smoking is not the new cure for low iron. Here's what seems to be going on: This genetic mutation causes one component of hemoglobin—an iron-rich protein in red blood cells that carries oxygen around the body—to rapidly bind with oxygen, then oxidize, fall apart, and lose its heme iron; eventually the deformed cells are destroyed. This usually causes anemia, or a low red blood cell count.As it turns out, this mutation also makes hemoglobin more likely to bind to carbon monoxide than to oxygen (this was established in previous research at Rice University). So in someone who smokes, hemoglobin would theoretically take up carbon monoxide from cigarettes rather than oxygen, thereby preventing oxidation and the cell breakdown that would occur in a nonsmoker with the mutation. The Rice researchers tested that theory for a new study in The Journal of Biological Chemistry by exposing the mutant version of hemoglobin to both oxygen and carbon monoxide. They found that the mutant protein is 80,000 times more likely to bond with CO compared to oxygen and, sure enough, being bound to CO slowed down the protein's oxidation and prevented the loss of heme iron without completely compromising oxygen transportation. It's not the first time researchers found a hemoglobin mutation linked to lower levels of iron in nonsmokers and stabilized ones in smokers, but you probably didn't hear about it: the studies were published in 1978, 1980, and 1983.Lighting up is protective against anemia in this case, the researchers say (another weird side perk of this mutation: it makes people more resistant to carbon monoxide poisoning). Still, the mutation means that his blood can't carry as much oxygen so he might feel more fatigued and short of breath even compared to other smokers. And it definitely doesn't cancel out the other ill effects of smoking, which include an increased risk of stroke, type 2 diabetes, chronic obstructive pulmonary disease (COPD), and a dozen types of cancer (but you knew that already).The daughter has mild anemia and the authors said she should NOT treat it with cigarettes. "She shouldn't smoke," Rice University biochemist John Olson said in a release. "But she could take antioxidants, such as a lot of vitamin C, which would help prevent oxidation of her mutant hemoglobin. Her anemia is not that severe. At the same time, she shouldn't worry too much about secondhand smoke, which might have a positive effect." A positive effect on her anemia, that is, but not on her overall health.