Medically reviewed by Onikepe Adegbola, MD, PhD
Doctors prescribe iron supplements if you have iron deficiency or anemia. Iron deficiency can occur when there is severe blood loss, heavy menstrual cycles, pregnancy, Crohn’s disease, or kidney failure. Constipation is a common side effect of taking iron supplements.
It may get to the point that patients would prefer not to take iron at all than suffer from constipation, which is one of the worst outcomes. It can be frustrating to have chosen the right medicine and dosage only to find that compliance is the bottleneck. But why does iron cause constipation?
Causes For Iron-Induced Constipation
- Iron ion-induced water transport
A study titled “Ileus Due to Iron Pills: A Case Report and Literature Report on the Importance of Stool Softeners“ was published in Cureus 2020.
According to this study, excess iron ions in the stomach create an osmotic gradient that facilitates the passage of water into the intestinal lumen. This water is pulled from the intestines to maintain the acid-base balance in the gastrointestinal tract(the digestive system passageway from mouth to anus), making stools harder.
- Metabolism of iron in the stomach
In patients who use traditional supplements, breaking iron into ions in the stomach is the prime cause of upset stomach and constipation. When the quantity of ions increases, excess water is absorbed into the stomach to dilute ion concentration. Water is drained from the lower gastrointestinal system, making stools harder and difficult to pass.
- Type of salt in iron supplement
Although iron bisglycinate is the most stomach-friendly of the divalent iron salts and has fewer adverse effects, some people may be sensitive to it. As a result, they may experience constipation after taking iron bisglycinate.
Trivalent iron salts may have more unabsorbed iron, which causes constipation more commonly than divalent iron salts. The more iron you ingest, the more likely you experience adverse effects.
- Rate of iron absorption
According to a study, iron supplements induce constipation, as iron absorption is poor, both from diet and supplements. On average, iron from meals is absorbed by the body at a 10% rate in women and 5% in men. In cases of iron shortage, the absorption rate rises by up to 20%. The iron that remains unabsorbed by the body nourishes harmful microorganisms in the intestines, which may cause constipation.
- The unabsorbed iron ions
A study titled “Ferrous versus Ferric Oral Iron Formulations for the Treatment of Iron Deficiency: A Clinical Overview” was published in The Scientific World Journal in 2012.
According to this study, the quantity of iron not absorbed by the body induces constipation. The unabsorbed iron may be higher in trivalent iron (e.g., Ferrum Lek prescription medicine), which induces constipation more frequently than divalent iron salts.
When Taking Iron Tablets, There Are A Few Things You May Do To Avoid Constipation.
- Choose natural sources of iron
The simple approach to avoid iron deficiency and constipation from taking iron supplements is to eat iron-rich foods in your diet. As compared to plant sources, two to three times more iron is absorbed from animal sources. Lean beef, turkey, chicken, and oysters are among the foods that contain the most iron.
Beans, dark green leafy vegetables, tofu, healthy grains, and nuts are all sources of iron for vegetarians. Iron absorption will be improved by including a source of vitamin C.
- Choose the right dose of iron supplement.
Many options for iron supplements are available in the market. Ferric iron salts, such as ferrous sulfate and ferrous gluconate, are the most prevalent source of iron supplements. However, iron pills in this form are more likely to cause constipation as a side effect. Instead, choose gentle iron supplements like heme iron polypeptides, carbonyl iron, iron amino-acid chelates, and polysaccharide-iron complexes to prevent constipation.
- Drink a lot of water
Drink eight glasses of water in a day while taking an iron tablet. This helps relieve constipation and gives your intestines the fluids they need to generate softer stools.
- Drink orange juice
Drink orange juice with the iron tablet to provide your intestines with the fluids to produce softer stools. Orange juice has the extra benefit of containing vitamin C. Vitamin C increases iron absorption in the gut.
Vitamin C and iron together produce iron chelate, a compound that improves iron solubility in the small intestine.
- Follow a correct approach while taking iron supplements
To lessen the possibility of constipation, divide your prescription into three smaller daily doses. Start with a half-dose and progressively raise the amount every three days until you reach the complete dosage.
- Get your body moving
Even without iron supplementation, a sedentary lifestyle might promote constipation. Exercise every day to promote regular bowel motions. Walking or 20 minutes of mild exercise or a bike ride are good options.
- Know what to eat and what not to
Diet plays a role in regulating your bowel movements. Add high-fiber foods like whole grains, berries, fruit, vegetables, and legumes to your diet. Fiber adds bulk to stool and facilitates regular, smooth bowels. A handful of dried plums daily will help keep your intestines in a good state.
Avoid raw hard bananas, wheat products, blueberries and blackcurrants, a meat-heavy meal, cow milk, and cheese that can cause constipation.
Add sauerkraut, yogurts, pickles, natto, miso, tempeh, and fermented soy products that include living bacteria that enhance the microbiota of the stomach.
Constipation is a typical adverse effect of iron supplements. However, if you need to increase your iron consumption, dietary adjustments may help you avoid gastrointestinal discomfort. Include fruits and vegetables rich in iron to fulfill daily iron requirements. Additionally, ensure hydration, lifestyle modification, and regular exercise to prevent constipation. If you’re still bothered by the side effects of iron consumption, consult your doctor and only take supplements as advised.
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Eating, diet, & nutrition for constipation. (2022, March 14). National Institute of Diabetes and Digestive and Kidney Diseases. NIDDK | National Institute of Diabetes and Digestive and Kidney Diseases. https://www.niddk.nih.gov/health-information/digestive-diseases/constipation/eating-diet-nutritio
Ems, T., St Lucia, K., & Huecker, M. R. (2022). Biochemistry, Iron Absorption. In StatPearls [Internet]. StatPearls Publishing.
Exercise to ease constipation. (n.d.). WebMD. Retrieved June 6, 2022, from https://www.webmd.com/digestive-disorders/exercise-curing-constipation-via-movement
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Tolkien, Z., Stecher, L., Mander, A. P., Pereira, D. I. A., & Powell, J. J. (2015). Ferrous sulfate supplementation causes significant gastrointestinal side-effects in adults: A systematic review and meta-analysis. PloS One, 10(2), e0117383. https://doi.org/10.1371/journal.pone.0117383