Constipation is a prevalent problem, with millions of sufferers. People who have had difficulties for years may be delighted to discover that a simple mineral might help improve bowel function. Many Americans don’t get enough magnesium in their diets, so they may benefit from a supplement. Others have low magnesium due to their acid-suppressing drugs (JAMA Internal Medicine, Aug. 8, 2011). Here are a few readers’ stories:
Magnesium for Constipation:
Q. I have found 500 mg of magnesium a day works like a charm against constipation. I take it in the morning along with my vitamins. One bottle I have seen even said “laxative” on the label. My doctor said it was fine.
A. It was smart to check with your doctor. Magnesium can have laxative properties, but 500 mg is above the RDA for both men and women. The popular liquid laxative Phillips’ Milk of Magnesia contains 500 mg of magnesium per tablespoon. As you can imagine, too much magnesium may cause diarrhea. Individuals may vary in how much they tolerate.
People with poor kidney function should avoid using supplemental magnesium as a laxative. This could put undue strain on the kidneys.
Magnesium Success Story:
Q. I had constipation for five years. Citrucel and extra bran on my cereal were no help. Although I drank lots of water, I still had very hard little stools like a rabbit’s.
At water aerobics a friend told me about taking magnesium. It has worked wonders for me.
I take 500 mg before going to bed and have a good response, usually before noon the next day. I asked my internist and cardiologist if it was safe to take and they both said no problem. The cardiologist even said it is good for the heart as well. I thought you might want to pass this along.
A. Magnesium has long been used to counter constipation. Too much of this mineral can cause diarrhea, though. Most people tolerate 300 mg with no problems, but those with kidney problems must avoid extra magnesium.
Dietary Supplements Can Ease Constipation:
Q. Here’s another vote for magnesium to promote regularity. I’m in my 50s and have had terrible constipation for more years than I can remember. I’ve tried drinking lots of water and adding fiber to my diet. I only eat whole grains, got rid of “white foods” (rice, potatoes, bread), ate prunes, drank prune juice–and nothing worked.
Then a good friend (who happens to be a doctor) asked if I had been tested for magnesium deficiency. I hadn’t. She suggested a magnesium supplement every night. From the very first pill I took, the results were miraculous, so I never bothered to go in for testing. It’s great to find a solution that isn’t a drug and is cheap!
A. Many people report that magnesium supplements can help fight constipation. Do not take so much that it gives you diarrhea, though. People with low kidney function should avoid extra magnesium, as poorly functioning kidneys would strain to get rid of it.
You can read more about magnesium for constipation and sluggish bowel here.
Another reader offered her experience:
“I am a 61-year-old woman who has struggled with constipation from the time I was a child in the 1950s. My mother would chase me around the house to give me an enema! A nurse practitioner suggested taking vitamin B6 with magnesium and it has worked very nicely.”
Rhonda shared:
“I suffered from constipation for years. Only when I started taking 500 mg magnesium twice a day did I find relief. It has been a miracle find for me.”
Overdosing on Magnesium:
Rhonda is dangerously close to a diarrhea dose of magnesium. Many people find that 300 to 400 mg of magnesium does the trick without precipitating a fast trot to the bathroom. Anyone taking magnesium daily should have kidney function monitored by a doctor.
Too much magnesium can be hard on the kidneys, as this reader points out:
“The People’s Pharmacy has gotten me into a problem with my dear wife. As a regular reader, I always share stuff with her if I think it may help. Your comment about taking magnesium supplements to help alleviate persistent constipation is a case in point.
“She started taking magnesium and it helped her bowel function immediately. I was happy to have her benefit from your column. So what’s the problem?
“Her 90-year-old father, a long-time heavy user of milk of magnesia, is now having significant kidney malfunction issues. His medical advisors have identified the laxative as the cause.
“My wife has abruptly stopped using her magnesium supplement because of what is occurring with her dad. Could you kindly comment on any kidney risks associated with magnesium?”
A. Magnesium is essential for muscles, nerves and bones. This mineral helps regulate blood sugar, blood pressure and heart rhythm.
People with kidney problems are unable to tolerate excess magnesium. They should avoid supplements, laxatives or antacids that contain this mineral. Overdosing on magnesium may overwhelm the system and result in magnesium toxicity. This may be what happened to your father-in-law because of his milk of magnesia habit.
Low Magnesium:
Very low magnesium levels are rare, but people with digestive problems and those taking PPIs or immune-suppressing drugs are more susceptible to this problem (Internal and Emergency Medicine, online June 27, 2018). Thiazide diuretics can also lead to lower magnesium levels (Pharmacoepidemiology and Drug Safety, online Aug. 01, 2018).
It makes sense to find out if you are low in magnesium. People with type 2 diabetes, in particular, are far more vulnerable to cardiovascular complications when their levels are low (Endocrine Reviews, May 8, 2023).
Learn More:
We discuss magnesium and other simple approaches to combat constipation in our Guide to Constipation and in our Guide to Digestive Disorders.
You can also learn more about magnesium and its multiple uses in our Show 969: Magnesium–The Neglected Mineral.
