Get things moving without going overboard. Here’s what experts want you to know about magnesium and constipation.
Reviewed by Dietitian Katey Davidson, M.Sc.FN, RD, CPT
Key Points
- Taking too much magnesium can cause digestive side effects and, in severe cases, toxicity.
- Magnesium-rich foods can help you meet your daily needs without the same risk of excess.
- Staying hydrated and getting enough fiber can also support bowel regularity.
When constipation has you backed up, you may be eager to find a solution that can get things moving as quickly as possible. Your health care provider may have suggested taking a magnesium supplement, but now you’re left wondering how it works and whether taking more than the recommended dose could speed up relief.
While getting magnesium from food is generally best, supplements may provide additional support when needed. But when it comes to using magnesium for constipation, is more always better? We spoke with a gastroenterologist and dietitians to get to the bottom of how much magnesium is appropriate for constipation, whether you can take too much and what else you can do to keep your bowels moving regularly.
Can You Take Too Much?
When constipation lingers, it’s easy to assume that taking more magnesium could lead to faster relief. But when it comes to magnesium supplementation, Rabia de Latour, MDsays that it is possible to take too much.
Magnesium supplements, such as magnesium oxide and magnesium citrate, help relieve constipation by drawing water into the intestines, which softens stools and makes them easier to pass. But this same laxative effect can also cause gastrointestinal discomfort when magnesium is taken in excess.
In fact, “taking too much magnesium can cause diarrhea, nausea and vomiting, as well as abdominal pain and cramping,” says de Latour. With very high doses, she warns that excess magnesium can be toxic and potentially life-threatening, resulting in an increased heart rate, low blood pressure, difficulty breathing, muscle weakness and even cardiac arrest. The risk of toxicity is even greater for people with impaired kidney function, as their kidneys may not be able to effectively clear magnesium from the body.
To avoid these side effects, Anna Brown, M.S., RDnotes that the upper limit for magnesium supplements is 350 milligrams per day for adults. “Many standard forms come in 120-mg capsules, so typically around 3 capsules is the maximum amount,” she adds. When supplementing with magnesium, she recommends starting with the lowest dose and working your way up slowly based on how your body responds. More importantly, you should always talk to your health care provider before starting a magnesium supplement to determine the right dose for your individualized needs.
Food Sources of Magnesium
The good news is that excess magnesium from food does not pose the same health risk as supplements in healthy individuals. For adults, the recommended intake is 310 to 320 mg per day for women and 400 to 420 mg per day for men, depending on age. Yet, many adults fall short of these recommended amounts.
To meet your needs, Becky Bell, M.S., RDN, CLT, IFNCPsuggests prioritizing magnesium-rich foods in your diet. Some examples include:
- Pumpkin seeds, roasted, 1 ounce: 156 mg (37% Daily Value)
- Chia seeds, 1 ounce: 111 mg (26% DV)
- Almonds, dry-roasted, 1 ounce: 80 mg (19% DV)
- Spinach, boiled, ½ cup: 78 mg (19% DV)
- Cashews, dry-roasted, 1 ounce: 74 mg (18% DV)
- Peanuts, oil-roasted, ¼ cup: 63 mg (15% DV)
- Black beans, cooked, ½ cup: 60 mg (14% DV)
- Edamame, shelled, cooked, ½ cup: 50 mg
- Dark chocolate, 1 ounce: 42 mg (10% DV)
- Yogurt, plain, low-fat, 8 ounces: 42 mg (10% DV)
- Oatmeal, instant, 1 packet: 36 mg (9% DV)
- Banana, 1 medium: 32 mg (8% DV)
- Avocado, cubed, ½ cup: 22 mg (5% DV)
Other Tips for Constipation
Magnesium may help get things moving, but it’s not the only way to relieve constipation. Here are a few additional tips to support regular bowel movements:
- Increase Hydration. “Your colon absorbs water from stool, so when you’re dehydrated, it can be harder and more difficult to pass a bowel movement,” says Brown. She suggests staying hydrated from sources like water, herbal teas, smoothies, soups and high-water-content foods like watermelon, cucumbers and tomatoes.
- Consume Kiwis and Prunes. Bell highlights that both kiwis and prunes have been shown to increase stool frequency. For the best results, eat two kiwifruits or drink a half-cup to 1 cup of prune juice per day.
- Increase Fiber Amount and Diversity. “Aim for roughly 25 to 30 grams of fiber per day from a variety of plants like vegetables, fruit, beans, lentils, whole grains, nuts and seeds,” says Brown. Fiber adds bulk and softness to stool, while eating a variety of plants helps support a healthier gut environment. The key is to increase your fiber intake slowly and drink plenty of water to avoid stomach discomfort and bloating.
- Train Your Bowels. Brown emphasizes that many of us are always in such a rush that we don’t give ourselves time to actually use the bathroom. “Give yourself 10 to 15 unhurried minutes every morning, ideally after drinking water or eating breakfast, when the gastrocolic reflex naturally stimulates the colon.” She notes that over time, this can “train” your body to expect a bowel movement at this time.
- Support Your Circadian Rhythm. “Your digestive tract follows a daily rhythm, with gut motility ramping up after waking and eating,” says Brown. To help reinforce this rhythm and encourage predictable bowel movements, she recommends consistent sleep and wake times, morning sunlight and regular meals.
Our Expert Take
It turns out that you can, in fact, take too much magnesium to relieve constipation. Magnesium can help soften stools, but it may also cause diarrhea, cramping, digestive discomfort and even toxicity when taken in excess. Therefore, it’s important to follow your health care provider’s guidance and the dosing instructions for your specific supplement. Beyond magnesium supplementation, staying hydrated, getting enough fiber and responding to your body’s natural urge to go can all help support bowel regularity.