# How can one tiny iron supplement a day constipate me so badly? **URL:** \ **Category:** Factual Questions\ **Created:** [August 19, 2011, 9:42pm UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376 "2011-08-19T21:42:57Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![OpalCat](https://avatars.discourse-cdn.com/v4/letter/o/8edcca/32.png) [@OpalCat](https://boards.straightdope.com/u/OpalCat)\ **Post date:** [August 19, 2011, 9:42pm UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/1 "2011-08-19T21:42:57Z")
It seems like somthing so tiny shouldn’t be able to fundamentally alter the texture of one’s feces to the extent that it does. Because of my surgery, when I’m not taking supplements, my “natural” consistency tends toward the softer end. Like peanut butter. But when I take iron supplements it turns into something like…oh… well, it feels roughly like a bowling ball. What is the mechanism by which this happens? Anyone know? (I avoid it for the most part by taking stool softeners daily but if I forget…boy howdy.) Anyway I’m just interested in the science of it. ---
**Author:** ![Cheshire\_Human](https://avatars.discourse-cdn.com/v4/letter/c/5f8ce5/32.png) [@Cheshire\_Human](https://boards.straightdope.com/u/Cheshire_Human)\ **Post date:** [August 20, 2011, 3:23am UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/2 "2011-08-20T03:23:13Z")
You might want to skip opiates, since they have an unpleasant tendency to cause constipation. I personally would be wary of amphetamines, here, too, since they are also implicated in bowel function. Iron supplements are not usually implicated in this sort of problem. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [August 20, 2011, 4:33am UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/3 "2011-08-20T04:33:22Z")
> [@Cheshire\_Human](#): > > You might want to skip opiates, since they have an unpleasant tendency to cause constipation. I personally would be wary of amphetamines, here, too, since they are also implicated in bowel function. Iron supplements are not usually implicated in this sort of problem. Depends on which hole you’re taking them in. Anyway, if you’re taking opioids… well, William S. Burroughs, who would know, said that heroin users would get so stopped up you’d need to take an apple corer to their asses to get them cleaned out. So it’s pretty well known that opioids make muscles less willing to work, which applies to the muscles responsible for making feces flow normally, which leads to constipation. The link between iron and constipation seems a lot more tenuous. ---
**Author:** ![kittenblue](https://avatars.discourse-cdn.com/v4/letter/k/ba8739/32.png) [@kittenblue](https://boards.straightdope.com/u/kittenblue)\ **Post date:** [August 20, 2011, 5:39am UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/4 "2011-08-20T05:39:41Z")
Don’t know why everyone is discussing opiates and amphetamines when you are asking about iron, but here: "Studies have shown that iron can slow down the digestive system. This can also contribute to slowing of normal bowel movement. This may be because iron is a metal in its basic form. Metals can carry a charge that is magnetic or electric, affecting muscles and nerves in the bowel. ``` Iron supplements are available in ferrous and ferric forms. Ferrous iron (ferrous sulfate, ferrous fumarate and ferrous gluconate) tends to be the best-absorbed. Iron can be taken in pill and liquid forms. Iron supplements that work quickly add more of the metal to the body, so they may cause more constipation. Slow-release forms of iron may be easier on the digestive system but not be absorbed as effectively. Liquid iron also tends to be less constipating, especially since the dose can be controlled more easily. The least-constipating form of iron is food. Soybeans, oatmeal and iron-fortified cereals contain the supplement along with fiber, but some people need supplements to get enough iron. Taking iron supplements without food more frequently causes constipation because the iron is absorbed better. Eating a meal, especially one high in fiber from vegetables or legumes, helps the iron move through the digestive system. Red meat can help the body absorb iron better, as can vitamin C. Blood tests can monitor the levels of iron and determine if your body is absorbing the needed amount." ``` So that should answer the “Why”. And I forgot to grab the link, but it was an E-How article titled, “Why do iron supplements Cause Constipation” I’m severely anemic since my gastric bypass, and I’ve been studying up, because this year the doctor wants me to do supplements as well as the five IV iron infusions I just finished up. The IV stuff did NOT have negative effects for me, but it also isn’t enough. ---
**Author:** ![Ferret\_Herder](https://avatars.discourse-cdn.com/v4/letter/f/e47774/32.png) [@Ferret\_Herder](https://boards.straightdope.com/u/Ferret_Herder)\ **Post date:** [August 20, 2011, 1:06pm UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/5 "2011-08-20T13:06:40Z")
> [@kittenblue](#): > > Don’t know why everyone is discussing opiates and amphetamines when you are asking about iron, but here: Because she also takes those on occasion and they may be having an effect. That being said, I’ve seen iron supplements that are combined with a stool softener in one gel cap, so you may find that to be a better solution, such that you won’t forget the latter. ---
**Author:** ![njtt](https://avatars.discourse-cdn.com/v4/letter/n/ecd19e/32.png) [@njtt](https://boards.straightdope.com/u/njtt)\ **Post date:** [August 20, 2011, 1:12pm UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/6 "2011-08-20T13:12:00Z")
> [@kittenblue](#): > > “This may be because iron is a metal in its basic form. Metals can carry a charge that is magnetic or electric, affecting muscles and nerves in the bowel.” That part, at least, is sciencey sounding bullshit/woo, and unfortunately it is the only part of your quote that directly addresses the original question. ---
**Author:** ![OpalCat](https://avatars.discourse-cdn.com/v4/letter/o/8edcca/32.png) [@OpalCat](https://boards.straightdope.com/u/OpalCat)\ **Post date:** [August 20, 2011, 7:01pm UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/7 "2011-08-20T19:01:23Z")
> [@Ferret\_Herder](#): > > Because she also takes those on occasion and they may be having an effect. > > That being said, I’ve seen iron supplements that are combined with a stool softener in one gel cap, so you may find that to be a better solution, such that you won’t forget the latter. My hematologist says those barely get absorbed, though. He said it’s one of medicine’s “good ideas that didn’t pan out” things. ---
**Author:** ![OpalCat](https://avatars.discourse-cdn.com/v4/letter/o/8edcca/32.png) [@OpalCat](https://boards.straightdope.com/u/OpalCat)\ **Post date:** [August 20, 2011, 7:04pm UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/8 "2011-08-20T19:04:01Z")
> [@kittenblue](#): > > Don’t know why everyone is discussing opiates and amphetamines when you are asking about iron, but here: > > "Studies have shown that iron can slow down the digestive system. This can also contribute to slowing of normal bowel movement. This may be because iron is a metal in its basic form. Metals can carry a charge that is magnetic or electric, affecting muscles and nerves in the bowel. > > ``` > Iron supplements are available in ferrous and ferric forms. Ferrous iron (ferrous sulfate, ferrous fumarate and ferrous gluconate) tends to be the best-absorbed. Iron can be taken in pill and liquid forms. Iron supplements that work quickly add more of the metal to the body, so they may cause more constipation. Slow-release forms of iron may be easier on the digestive system but not be absorbed as effectively. Liquid iron also tends to be less constipating, especially since the dose can be controlled more easily. The least-constipating form of iron is food. Soybeans, oatmeal and iron-fortified cereals contain the supplement along with fiber, but some people need supplements to get enough iron. > > Taking iron supplements without food more frequently causes constipation because the iron is absorbed better. Eating a meal, especially one high in fiber from vegetables or legumes, helps the iron move through the digestive system. Red meat can help the body absorb iron better, as can vitamin C. Blood tests can monitor the levels of iron and determine if your body is absorbing the needed amount." > > ``` > > So that should answer the “Why”. And I forgot to grab the link, but it was an E-How article titled, “Why do iron supplements Cause Constipation” > > I’m severely anemic since my gastric bypass, and I’ve been studying up, because this year the doctor wants me to do supplements as well as the five IV iron infusions I just finished up. The IV stuff did NOT have negative effects for me, but it also isn’t enough. Thanks for the info! I need the supplements because of my surgery and my vegetarianism. I’ve had to get the iron infusions, too. I used to say they had a rusted out old Chevette out back that they’d scrape off for my appointments. ---
**Author:** ![jabiru](https://avatars.discourse-cdn.com/v4/letter/j/bbce88/32.png) [@jabiru](https://boards.straightdope.com/u/jabiru)\ **Post date:** [August 20, 2011, 11:55pm UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/9 "2011-08-20T23:55:42Z")
I eat little meat, so tend towards anaemia. I’ve tried a lot of different iron supplements, most of which had a constipating effect to a greater or lesser degree. The ones which I found best were the liquid ones. Not as easy to swallow, admittedly, but a lot gentler on the other end of the GI tract. ---
**Author:** ![Cicero](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cicero/32/3594_2.png) [@Cicero](https://boards.straightdope.com/u/Cicero)\ **Post date:** [August 21, 2011, 11:46am UTC](https://boards.straightdope.com/t/how-can-one-tiny-iron-supplement-a-day-constipate-me-so-badly/593376/10 "2011-08-21T11:46:08Z")
Just read a few of my posts on the toilet. That will be inspiration enough.