Generally better, but the answer is a little more nuanced.
We had access to data describing how DNA influences iron levels, and how DNA influences years of healthy life. This showed that the same DNA variations that change your levels of iron in the blood also change how many years you spend in good health.
Now, these genetic effects are relatively small, so we can confidently say that people who carry genes which cause them to have slightly lower iron levels (i.e. one standard deviation) than the population average will be healthier, on average.
However, extrapolating that further can be dangerous - for example, anyone with iron levels three standard deviations lower will not be three times healthier, they'd have no iron in their blood and be dead.
We had access to data describing how DNA influences iron levels, and how DNA influences years of healthy life. This showed that the same DNA variations that change your levels of iron in the blood also change how many years you spend in good health.
Now, these genetic effects are relatively small, so we can confidently say that people who carry genes which cause them to have slightly lower iron levels (i.e. one standard deviation) than the population average will be healthier, on average.
However, extrapolating that further can be dangerous - for example, anyone with iron levels three standard deviations lower will not be three times healthier, they'd have no iron in their blood and be dead.