Due to them saying that "the association might be due to an already-known correlation to haemochromatosis" I'm assuming they didn't have the data to correlate haemochromatosis to the data.

Haemochromatosis is a genetic disorder where individuals are unable to get rid of excess iron. If properly diagnosed, this is easily treatable with bloodletting (blood donation in this century :-)

Haemochromatosis is the sort of genetic disease that could really screw with data like this. Undiagnosed haemocromatosis leads to early death....so the correlation of excess iron to longevity should be treated as a weak piece of evidence until we can exclude people with the genetic disorder.

Great comment! For the iron - ageing link, we used two pieces of data: the effect of DNA on blood iron levels, and the effect of DNA on how long and healthy you live. We found the mutation that causes hereditary haemochromatosis had a large effect on early death (as expected). However, other genetic variations that increased blood iron levels also had a proportional effect on early death. So it looks like it is higher iron levels, not just haemochromatosis, that may accelerate the rate of ageing.

does this boil down to "diets that are high in iron, aka meat, will yield a life that is less long compared to a diet that is low in iron (meatless)?"

Is there any evidence that eating more meat actually causes higher blood iron levels?

Can someone answer the first question before we introduce a sixth?