I’ve been feeling a little run down lately, and I noticed that my multivitamins did not have an iron supplement. So I went and got a daily iron supplement and I noticed that the bottle says “Do not exceed one pill a day.” Now I never had any intention of doing so, but it made me curious: What happens if I do?
I am pretty sure your body controls how much Iron you absorb. If you are low on iron you may absorb 30% of the Iron you take, if you have enough you only absorb 10% or so (I don’t remember the exact numbers). There is also a widespread disease where people absorb 50%+ of the iron they eat and easily get iron toxicity but I don’t remember what that disease is called.
High iron levels are a risk factor for diabetes.
Yes, your body does control how much Fe you absorb. Most people ingest 10-15mg of Fe daily but only ~1mg is actually absorbed. I am aware of a couple of syndromes where iron overload is a problem.
Hereditary hemochromatosis: Inborn error of Fe absorption. The body increases it’s absorption of Fe eventually saturating all available storage systems. The excess Fe starts to accumulate in the tissues, causing hyperpigmentation of the skin, diabetes, cirrhosis of the liver, pituitary insufficiency, hypogonadism, heart arrythmias, heart failure and arthritis. 10% of Caucasians of N. European descent are carriers for the trait.
Due to frequent blood transfusions: Patients who suffer from aplastic anemia produce red blood cells at a very decreased rate from normal. RBCs are chock full of Fe, so when the transfused cells break down in the recipient’s bloodstream, the excess Fe can start accumulating in the tissues. Many patients are put on chelating therapy to prevent this from happening: Desferal is circulated in the bloodstream from a little portable pump which the patient wears 9-12 hours a day.
Rarely, hemosiderosis (iron overload without associated tissue injury) can be caused by protracted ingestion of iron supplements over many years.
Source: Tietz, N.W. Fundamentals of Clinical Chemistry, 3rd Ed. 1987, pp 819-820
Hemochromatosis takes years to develop, even in people who have a “double dose” of the gene (about 1 in 250*).
OTOH, more acute iron poisoning is relatively common, especially in kids.
Here is an interesting little paper by someone I know. Take a peek at the photos or, better yet, check out the PDF.
*this implies that the gene carrier frequency is about 1 in 8 (!)
Even in cases of heriditary hemochromatosis (we test for the mutations involved in my lab), patients usually don’t present with symptoms until their 40s or later. In other words, it takes decades of your body mistakenly uptaking way too much iron before enough damage is done that you start feeling it. Unfortunately, once someone is showing symptoms, it’s usually too late, and they die of cirrhosis of the liver or heart damage, which is why we have the genetic test in the first place, so it can be caught before the symptoms show up.
I was on iron supplements for a while, and at first they prescribed way, way too much for me, giving me minor iron poisoning. It was awful; terrible nausea and general malaise. Not something you’d like to try.