Answer:

As discussed below, a number of supplements and foods can help treat or prevent constipation — although some traditionally used supplements may not help. Some supplements can worsen constipation. Use the links for additional information.

Supplements that may help with constipation

Foods and supplements high in fiber may help to relieve constipation.

Supplements high in fiber include psyllium, glucomannan (a water-soluble fiber) and ground flaxseed. Be aware, however, that ConsumerLab has found some psyllium products to have relatively high levels of lead, a toxic heavy metal (see the Psyllium Fiber Supplements Review), and there is a safety concern when using glucomannan.

Simply eating two servings per day of high-fiber fruits may help prevent or treat constipation (Bae, Pediatr Gastroenterol Hepatol Nutr 2014; Dreher, Nutrients 2018; Bellini, Nutrients 2021). Fruits that are good sources of fiber include kiwi fruit (5 grams per cup), pears (4 grams per cup), apples (with skin) (3 grams per cup), apricots (3 grams per cup), mangos (3 grams per cup), figs (2.4 grams per 3 figs), and prunes (2.1 grams per 3 prunes) (USDA 2018 data compiled on MyFoodData.com). In fact, a study among people with chronic constipation showed that eating about 5 prunes (50 grams) twice daily for 3 weeks increased the number of bowel movements somewhat more than taking 11 grams of psyllium with water (Metamucil) twice daily: Prunes led to an increase of 2.4 bowel movements per week versus 1.6 with psyllium. Prunes also produced slightly softer stools than psyllium, although both similarly reduced straining (Attaluri, Aliment Pharmacol Ther 2011).

To avoid gastrointestinal disturbances such as bloating or flatulence, gradually add high-fiber fruits to your diet.

Although ripe bananas are a good source of fiber (3 grams per cup), they contain tannins and amylase-resistant starch which may aggravate pre-existing constipation (Bae, Pediatr Gastroenterol Hepatol Nutr 2014). Similarly, inulin, which is mostly fiber and is marketed as a prebiotic, has been shown to be modestly beneficial for increasing the frequency of bowel movements in people with constipation, although it may increase gas.

A specific probiotic product was found to significantly increase the number of bowel movements per week in people with chronic constipation. (Other strains have been found to be helpful for constipation associated with IBS).

Magnesium and aloe vera juice (with latex) can help to relieve constipation due to their laxative effects. Be aware, however, of safety concern with aloe latex — see the “Concerns and Cautions” section of the Aloe Vera Review.

Supplements that may not help with constipation

Baking soda is touted as a remedy for constipation, but there is no evidence to support this use. Proponents claim that drinking baking soda dissolved in water may help relieve constipation by pulling water into the digestive tract, which causes muscle contractions that may promote bowel movements. However, no clinical studies have evaluated the effectiveness of baking soda for constipation, and there are a number of serious adverse reactions that can occur with overuse of baking soda (see our CL Answer about baking soda for details).

Marshmallow (Althaea officinalis) root (which is unrelated to confectionery marshmallows) has been used in the form of teas and syrups, most often as a treatment for cough. It has also been used traditionally to treat constipation (Shah, J Med Plants Res 2011), but there is no clinical evidence to support this use.

Supplements that may cause or worsen constipation

There are a number of supplements that can cause constipation. Iron supplements, for example are a common culprit. The good news, however, is that certain forms of iron may be less likely to cause constipation than others.

Similarly, calcium supplements can cause constipation in some people, but one particularly popular form of calcium may be more likely to do so than another.

Some people find that protein powders and drinks cause constipation and bloating.

Other supplements reported to cause constipation, although less frequently, include cinnamon, berberine, nattokinase, chlorella, NAC (N-acetyl cysteine) and beta-sitosterol.

Excessive intake of vitamin D as a supplement can cause hypercalcemia (too much calcium in the blood) with symptoms including constipation.

If you take one of the supplements above and experience constipation, you may want to consider trying a different form, when possible (such as with iron and calcium), or stopping the supplement to see if that helps.