Many, many people around the world are not getting enough iron — in fact, it’s the most common nutrient deficiency worldwide. So it’s probably no surprise that iron supplements are so popular, and that this mineral is also commonly found in many multivitamins.
But in your quest to give your body the nourishment it needs, you might run into an uncomfortable side effect: constipation.
Why you might need an iron supplement
If you don’t have enough iron, your body can’t make enough red blood cells to carry oxygen to where you need it. Iron is a crucial component of hemoglobin, a protein in your red blood cells that carries oxygen. Every single cell in your body requires oxygen, which your red blood cells deliver via its extensive network of blood vessels.
So if you are iron deficient, you could run into serious issues transporting oxygen throughout your body. A prime example is iron-deficiency anemia, a condition in which your body can’t make enough red blood cells. This can manifest in symptoms like fatigue, pale skin, shortness of breath, and dizziness.
Iron is found in a variety of dietary staples like meat, legumes, and leafy greens. However vegans and vegetarians might have a hard time meeting their recommended iron intakes, since heme iron, the better-absorbed form of iron, is found only in animal products. Iron deficiency is also common in those who have conditions like
Want to learn which nutrients you’re deficient in?
The Base Diet Deficiencies Test measures ferritin (a blood cell protein that indicates how much iron your body is storing) as well as vitamin B12 stores.
The link between iron, constipation, and other stomach issues
Because iron deficiencies are so common, iron supplements are also pretty popular. But unfortunately, iron supplements are notoriously hard on the stomach. This can lead to constipation, one of iron’s most common side effects, as well as other gastrointestinal issues like dark stool, nausea, and diarrhea.
Why does this happen? One theory is that the high amount of iron in your stomach from supplementation causes an osmotic effect that pulls water into your stomach and away from your lower gastrointestinal system (ie: your large intestine and your colon). As water leaves your lower GI tract, your stools can become dehydrated, harder, and smaller — and ultimately, more difficult to pass.
Another potential explanation is that iron can alter your gut microbiota, or the species of bacteria that reside in your gut. Excess iron is thought to encourage the growth of species like Protebacteria, a potentially pathogenic bacterial species that one study found to be frequently detectable in patients with chronic constipation.
Is the iron in your multivitamin the culprit behind constipation?
What if you aren’t taking an iron-specific supplement, but a multivitamin instead? Can that still lead to constipation and other gastrointestinal issues?
Multivitamins with iron, especially those that are marketed towards women, generally provide about 18 mg of iron, the recommended Daily Value for most adults. On the other hand, someone who has been diagnosed with iron deficiency will often be recommended to take iron at significantly higher levels — possibly up to 120 mg of iron per day for three months, according to the American Family Physician Journal.
But even though the dosage in your multi might be lower than an iron-specific supplement, some people might still find that it upsets their stomach. For example, a large meta-analysis of 43 different iron supplementation trials saw that iron supplementation tended to lend itself to gastrointestinal side effects among a total of 6,831 adult participants — but they couldn’t find any significant evidence that people who took higher doses were more likely to experience those symptoms than those who had a smaller dosage.
What to do if iron supplementation is causing constipation or gastro distress
While low iron levels are not good for you, it’s worth noting that excess iron supplementation can definitely be too much of a good thing if you aren’t sure how much you should be taking. Ingesting higher amounts of iron than you need can lead to free iron circulating in your blood, which can be toxic and lead to serious damage to your intestines and other organs.
The bottom line here is that yes, iron supplementation is often necessary, but taking any supplements willy-nilly, without actually knowing how much is currently in your system, is not a good idea. If you’re experiencing symptoms like lethargy and dizziness and suspect that you might have low iron levels, the very best thing you can do is check in with a healthcare professional and/or take a blood test.
At-home Energy and Diet tests by Base allow you to make more informed decisions about what your body needs. Ultimately, keeping track of your blood work allows you to have real, measurable data so that you always know if you’re hitting your health goals, overshooting, or falling short. And if your lab workup shows a true deficiency, you’ll get a recommended dosage that ensures you aren’t overdoing it.
Here’s what to do to combat constipation while on an iron supplement
When you genuinely need to take an iron supplement, some diet and lifestyle tweaks might help minimize the stomach issues.
- Pair your iron supplement with food. It’s often recommended to take your iron supplement on an empty stomach since it maximizes the amount of iron you can absorb from it. Unfortunately, taking it on an empty stomach is also part of the reason that it is so harsh on your gastrointestinal system to begin with. Some people find that pairing their iron supplement with a small amount of food helps to minimize the negative gastrointestinal side effects. If you do decide to pair your iron supplement with food, consider something rich in Vitamin C, which is known to promote iron absorption.
- Try a different kind of iron supplement. As opposed to regular iron supplements, “slow-release” iron pills take longer for your body to metabolize, which can also help minimize the side effects involved.
- Consider taking a stool softener. Adding a stool softener/antacid to your supplement regimen might make it easier for you to maintain regular bowel movements while taking an iron supplement. However, be sure to check in with a medical provider before doing this, since antacids might bind to your iron supplement and make it harder for your body to absorb as much iron as it needs.
- Increase your physical activity. Studies suggest that regular aerobic exercise like walking, jogging, cycling, and swimming might help people who report struggling with chronic constipation. Set aside a small block of time each day to get moving.
- Drink more water. Staying well-hydrated is crucial for fighting the dehydration in your lower gastrointestinal system that can contribute to constipation. Keep a water bottle on hand and make it a habit to refill regularly.
Bottom line
When you need to take an iron supplement and don’t want to be slowed down by constipation, your first course of action is to determine just how big of a dosage you need in the first place. From there, you can make select changes to your diet and lifestyle so that both your circulatory and your digestive systems can thrive in harmony.
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