Herbal laxatives: All you need to know

Whether you drink senna tea, pop psyllium capsules, or chug aloe juice... there is a lot you probably don't know about these remedies. I reveal the science behind herbs for constipation.

Aloe juice contains compounds that act as stimulant laxatives.

I'm excited to share an update on my Botanical Medicine and Health class at Emory University. We’ve reached mid-semester, and this is my favorite point in the class as students have built a strong foundation in some of the course’s core topics; they grasp the botany now and are becoming more familiar with the safety and efficacy of many classes of plant-derived bioactive molecules.

Currently, we're delving deep into the section on the pharmacological properties of medicinal plants for various body systems. In our most recent class, we explored the gastrointestinal (GI) tract, covering a range of indications such as heartburn, constipation, irritable bowel syndrome, and diarrhea.

The full scope of the GI lecture is hard to cover in a single newsletter post, so I’ll hone in on the one aspect I think may be of greatest interest to you all, my dear readers: herbal remedies for constipation.

What is constipation?

Constipation is not a disease, per se, but rather a symptom of another medical problem, and it can afflict anyone of any age. According to the National Institute of Diabetes and Digestive and Kidney Diseases, constipation is common in the US, with 16% of all adults and 33% of all adults over 60 experiencing symptoms. Notably, some people battle chronic constipation, while others may experience it only sporadically as a temporary issue.

Symptoms of constipation include:

• less than three bowel movements a week

• stools that are hard, dry, or lumpy

• stools that are difficult or painful to pass

• a feeling that not all stool has passed

Senna alexandrina (Egyptian senna) is native to upper Egypt in the Nubian region. It was once a major plant of trade, with the pods sold out of the historical port of Alexandria, Egypt. The fruits and leaves of this beautiful plant have long been valued for their laxative properties.

How do herbal remedies work to treat constipation?

Herbs have been used for millennia to relieve the symptoms of constipation. Here are the primary mechanisms of action through which they elicit these effects:

1. Stimulant laxatives: These herbs stimulate peristalsis to move the intestinal contents down the tube. Many stimulant laxative herbs also have the added benefit of acting as osmotic agents. They draw water into the bowel to soften the stool and increase the stool volume, assisting in triggering a bowel movement.

2. Bulk-forming laxatives: These herbs absorb water and increase the bulk of the stool’s material. Different herbs have different capacities for absorbing water, known as the swelling factor. I provide comparisons of swelling factor efficiency for different herbs below. The resulting larger stool can trigger the bowel to contract and result in a bowel movement.

Peristalsis is defined as the constriction and relaxation of the intestine muscles, creating wave-like movements that push the canal’s contents forward.

Most importantly, there are different safety and efficacy parameters to consider when selecting an herbal laxative. Not all of these are safe for regular use. I provide a simple breakdown of when to use or avoid certain herbal laxatives here for the paid and founding subscribers.

Herbal Stimulant Laxatives

There are a few popular herbal stimulant laxatives:

• Aloe juice is prepared as a homemade extraction of the leaf gel or can be purchased in health food stores or online vendors. Aloe juice is also beginning to appear in many ‘health’ beverages, mixed with other juice ingredients and flavors.

• Senna. Senna is an FDA-approved non-prescription over-the-counter (OTC) medication. It is taken as a tea (marketed by reputable brands like Traditional Medicinals or Senokot), or the active compounds (sennosides) are also sold in OTC pill or gummy form in products like:

  • Senokot Regular Strength

  • Senokot Laxative Gummies

  • Equate Maximum Strength Laxative

  • Equate Natural Laxative

  • ExLax

• Cascara sagrada. The bark of this plant is stripped and aged for months before use. Consumption of fresh bark will cause intense vomiting and diarrhea—never use fresh bark! In 2002, the FDA declared that non-prescription cascara sagrada products (including those containing the actives compounds, cascarosides) were not "generally recognized as safe and effective" (GRASE) for use as stimulant laxative ingredients in OTC drug products. Aloe products for this purpose were also deemed non-GRASE in the same FDA ruling. However, dietary supplements for both ingredients are still available on the market.

Other common sources of anthraquinone stimulant laxatives include rhubarb root and buckthorn.

Frangula purshiana is a large shrub to small tree native to the west coast of North America, ranging from California to British Columbia and in the Rocky Mountains of Montana. It is commonly known as cascara sagrada (from Spanish), which translates to “sacred bark”. The bark has been long used by Native People’s of this region as a laxative.

Chemistry and pharmacology of stimulant laxatives

Chemical structures of anthraquinone glycosides with stimulant laxative properties.

Each of the above ingredients shares a class of bioactive molecules in common: anthraquinone glycosides (AGs). Each plant produces a different subset of AGs:

• Aloe: aloin (found in aloe latex, concentrated in the section of the leaf between the inner gel and the outer leaf tissue)

• Senna: sennosides (found in the fruit (pod) or leaf of the plant)

• Cascara sagrada: cascarosides (found in the bark of the plant)

As the chemical structure and mechanism of action for these molecules are similar, their efficacy and safety profiles are also. Regarding timing (and depending on the dose), one can expect relief from symptoms around 8-12 hours after taking AG laxatives. For this reason, these are typically taken at night to relieve symptoms by morning. It is recommended to drink plenty of water (6-8 cups minimum) throughout the day when taking any of these medicines.

Side effects

Common side effects include abdominal pains, cramps, and diarrhea.

Safety concerns

Herbs rich in AGs (aloe, senna, cascara sagrada, rhubarb, and buckthorn) should only be used on a short-term basis. This is because long-term use can:

• Potentially increase risk of colorectal cancer (see this meta-analysis for more details)

• Lead to liver damage

• Lead to laxative dependence

People with stomach pain or inflammation, intestinal blockage, inflammatory bowel disease, or diarrhea should not use these medicines.

Bulk-Forming Laxatives

There are a few popular herbal bulk-forming laxatives:

• Psyllium. The seeds or the husks (seed covering) are used as the main ingredient. The husk powder has the highest swelling factor of any current options on the market (>40) and is available as a dietary supplement in capsules or loose powder sold in large bags. Established brands like Metamucil also sell a variety of flavored psyllium husk-based products. The whole seeds have a swelling factor > 9. I like to use psyllium in capsule form when needed for symptom relief.

The swelling factor is calculated as the volume of the drug (plant material) before and after water exposure. Drugs with a higher swelling factor are more effective in increasing the bulk of material as it passes through the intestine.

• Flax seed. Whole flax seeds have a swelling factor of 4, whereas the powder is slightly improved at 4.5. You can find many milled or powdered flax seed suppliers for this purpose. Note that flax seed oil is also available as a supplement, however, it does not elicit any bulk-forming laxative effects.

• Wheat bran. Wheat bran has a swelling factor of >4, similar to flax seed. It has more limitations as a laxative for regular use due to the presence of phytic acid. In large concentrations, phytic acid can interfere with the bioavailability of vitamins in your diet, leading to poorer nutritional status.

These ingredients may be used whole or ground into a powder. In general, the increased surface area of the ground powder yields a higher swelling factor.

Chemistry and pharmacology of bulk-forming laxatives

Psyllium husks (from Plantago psyllium and Plantago ovata) exhibit the highest swelling factor of any bulk-forming laxatives on the market. Drink lots of water when using this medicine.

Each of the above ingredients is rated by their swelling factor, or the ability of the drug product to absorb water. In the intestines, these materials mix with and expand the volume of the intestinal contents, storing more water in the stool and increasing pressure that stimulates bowel movement. Unlike stimulant laxatives, this approach is mechanical rather than chemical in nature.

Safety concerns

While the time to experience effects of bulk-forming laxatives (2-3 days) are not as fast as those of stimulant laxatives (8-12 hours), they offer a much better safety profile! Psyllium husks, in particular, yield the best swelling factor per amount consumed and are safe for long-term use. Wheat bran is not the best option for long-term use because of the presence of phytic acid, which can interfere with nutrient absorption.

The most important thing to do when using any bulk-forming laxative is to drink plenty of water! This is important to ensure the safe use of the product AND it provides the water necessary to yield the desired swelling effect in your intestines. Start small with your doses, drink plenty of water, and be patient, as it can take 2-3 days to experience symptom relief.

Any of these products must always be taken with plenty of water. For psyllium, in particular, drink a large full glass of water when taking them in capsule or powder form to wash it down and ensure that it won’t swell in the throat, causing choking.

As with any laxative, if you experience any sudden changes in bowel habits that continue for two weeks, or experience bleeding from the rectum, seek medical attention from your doctor.

Yours in health, Dr. Quave

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Cassandra L. Quave, Ph.D. is a disabled writer, speaker, podcast host, wife, mother, explorer, ethnobotanist, and professor at Emory University School of Medicine. She teaches college courses and leads a group of research scientists studying medicinal plants to find new life-saving drugs from nature. She hosts the Foodie Pharmacology podcast and writes the Nature’s Pharmacy newsletter to share the science behind natural medicines. To support her effort, consider a paid or founding subscription, with founding members receiving an autographed 1st edition hardcover copy of her book, The Plant Hunter.