Psyllium

Plantago ovata Forssk. (synonym P. ispaghula Roxb.) belongs to Plantaginaceae, the plantain family; NCBI Taxonomy files it as taxon 185002. Das and Trivedi (Indian Horticulture 2023), writing in the Indian Council of Agricultural Research’s horticulture magazine, note that the genus Plantago contains about 200 species and that P. ovata is native to the Mediterranean region and West Asia, extending east to the Sutlej and Sindh in Pakistan, with populations in the Canary Islands, southern Spain, North Africa, and the Middle East. It is a low annual herb that bears short flower spikes above its leaves; the Indian variety Gujarat Isabgol-1, released in 1976, grows to about 50 cm, with spikes of 4.0–4.5 cm, and matures in 110–115 days. The Hindi and Gujarati name isabgol comes, the same authors explain, from Persian words meaning horse’s ear, for the boat-like shape of the seed. In trade it is called blond psyllium, a name also used in US federal regulations.

India dominates the crop. Das and Trivedi describe it as introduced and cultivated in north Gujarat and adjoining western Rajasthan and Madhya Pradesh, now spreading to Punjab, Haryana, Uttar Pradesh, and Karnataka; India supplies roughly 80% of the psyllium husk powder on the world market, and 90–95% of Indian production is exported. The plant is fussy about weather. Seeds germinate best at 20–25°C but need 30–35°C and dry conditions at maturity, because unseasonal rain or even heavy dew makes the ripe seeds swell and drop, which can destroy a harvest. Regions with winter rain are unsuitable. Most of the crop is exported as husk rather than whole seed.

Two medicinal products come from the plant. Ispaghula husk is the outer seed coat (episperm) and collapsed adjacent layers removed from the seed (EMA). EMA’s assessment report describes it as about 85% water-soluble fibre, a highly branched arabinoxylan made of roughly 65% xylose, 20% arabinose, 6% rhamnose, and 9% galacturonic acid, able to absorb up to 40 times its own weight in water. Whole ispaghula seed has 20–30% mucilage in its coat and absorbs up to 10 times its weight, so seed doses are larger. In EU terminology psyllium seed means the darker seeds of two related species, Plantago afra and P. indica, sometimes sold as black psyllium, which have their own monograph at higher doses. None of these should be confused with the common lawn and roadside plantains, broadleaf plantain (P. major) and ribwort plantain (P. lanceolata), although Bernedo and colleagues (Journal of Investigational Allergology and Clinical Immunology 2008) found mild allergic cross-reactivity between P. ovata seed and ribwort plantain pollen.

Plantain seeds are old medicines. EMA’s assessment report notes that Dioscorides, in the first century AD, described three plantain species: seeds of one were taken with wine for diarrhoea and for vomiting blood, and the seeds of Plantago psyllium were considered cooling and were applied as a compress, with attar of roses, vinegar, and water, for gout, swellings, dislocations, and headache. The same report records that psyllium appears in ancient Indian Ayurvedic prescriptions, and that in Unani medicine in Pakistan the husk is used for fevers, catarrh, and kidney complaints, a decoction of the seed for coughs and colds, and crushed seeds as a poultice for rheumatic and glandular swellings. Across traditions, EMA summarises, psyllium was used as an emollient, demulcent, and diuretic in the USA, Europe, India, and China.

European pharmacy gradually narrowed the uses to the bowel. EMA cites Hager’s German pharmacy handbook of 1927, which described oral and topical use of Plantago psyllium seed mucilage for inflammation; a 1966 text listing cough, catarrh, whooping cough, diarrhoea, and urethritis; and a 1967 reference that mentions only chronic constipation, dysentery, and chronic diarrhoea. The World Health Organization published a monograph on plantain seed covering P. afra, P. indica, P. ovata, and P. asiatica in 1999. Licensed products appeared early: EMA records ispaghula granules on the Belgian market since 1963 and powder since 1984. In India, agricultural research developed commercial varieties for Gujarat and Rajasthan from the 1970s, building an export crop that now supplies most of the world.

Modern regulation came on two fronts. In the United States, the FDA’s health claim for soluble fibre and coronary heart disease (21 CFR 101.81), first written for oats, was amended in February 1998 to include psyllium husk, provided a food supplies at least 1.7 g of psyllium soluble fibre per serving towards a daily total of 7 g, and foods containing dry psyllium husk must carry a warning to eat them with a full glass of liquid. EMA’s assessment report adds that because of oesophageal obstruction with granular psyllium laxatives taken without enough liquid, the FDA in 2007 stopped psyllium granules from being sold over the counter without an approved application. In Europe, the herbal committee adopted its first monographs on ispaghula husk and seed in July 2006 and revised them on 14 May 2013. The American College of Gastroenterology’s 2021 IBS guideline strongly recommended soluble fibre.

Psyllium works physically in the bowel. EMA’s monograph explains that when ispaghula husk is taken with enough liquid, at least 30 ml per gram, it swells into a mucilage that increases the volume of intestinal contents; the resulting stretch stimulus triggers defaecation, and the swollen gel forms a lubricating layer that eases transit. EMA’s assessment report cites data that psyllium increases stool weight by about 3.7 g for each gram consumed, and a 15-person study by Marlett and colleagues in which part of the husk survived the colon unfermented as a viscous gel, producing stools that were bulkier and moister than with comparable amounts of other fibres. The husk is only partly fermented (about 72% resisted fermentation in laboratory tests), which is why it bulks stool rather than simply feeding gut bacteria. The laxative effect usually begins within 12–24 hours, sometimes taking two to three days to peak. EMA’s assessment report also records national authorisations in several EU countries for use as an adjunct in diarrhoea, including diarrhoea in IBS.

The cholesterol effect is thought to run through bile acids. In a crossover trial cited by EMA, 20 men with moderately raised cholesterol took 15 g of husk daily for 40 days; those whose LDL cholesterol fell by more than 10% showed a significant rise in bile acid synthesis. In another, 23 adults taking 10.2 g daily for eight weeks had LDL cholesterol 6.5% lower than baseline, with rises in cholesterol precursors, suggesting the liver was drawing on cholesterol to replace bile acids lost in the stool. For blood sugar, viscous gel-forming fibres are thought to blunt the rise in glucose after meals, and Gibb and colleagues (American Journal of Clinical Nutrition 2015) found the effect greatest in people whose glucose control was worst.

Psyllium is barely digested. Its sugar chains are joined by bonds human enzymes cannot break; EMA notes that less than 10% of the mucilage is hydrolysed in the stomach, releasing arabinose, of which 85–93% is absorbed. The same gel that bulks stool can trap or slow other substances in the gut, which is the basis for the advice to space psyllium away from medicines and for EMA’s caution about minerals, vitamin B12, and several narrow-margin drugs.

Constipation is the core indication. EMA accepts ispaghula husk and seed as well-established medicines for habitual constipation and for conditions in which easy defaecation with soft stool is desirable, such as painful defaecation after rectal or anal surgery, anal fissures, and haemorrhoids, and advises that bulk-forming laxatives be tried before other laxatives if dietary change fails. Van der Schoot and colleagues (American Journal of Clinical Nutrition 2022) pooled 16 randomised trials with 1,251 adults with chronic constipation: 66% responded to fibre supplements versus 41% to control (risk ratio 1.48), and fibre increased stool frequency and improved consistency. Psyllium and pectin were the fibres with significant effects, and the benefit appeared mainly at doses above 10 g a day taken for at least four weeks. Flatulence was more common with fibre, and the authors cautioned that results varied considerably between trials.

Irritable bowel syndrome: Moayyedi and colleagues (American Journal of Gastroenterology 2014) pooled 14 trials with 906 patients and found that fibre reduced the risk of persistent IBS symptoms (relative risk 0.86, ten patients needing treatment for one to benefit), with the benefit confined to soluble fibre such as psyllium (relative risk 0.83, number needed to treat 7); wheat bran did not help. The largest single trial, by Bijkerk and colleagues (BMJ 2009), randomised 275 primary-care patients to 10 g of psyllium, 10 g of bran, or rice-flour placebo daily for 12 weeks. Adequate symptom relief was reported by 57% on psyllium versus 35% on placebo in the first month and 59% versus 41% in the second, and symptom severity fell by 90 points versus 49 at three months, with no difference in quality of life. Bran helped only in the third month, and dropouts were highest in the bran group, mainly because symptoms worsened. The ACG’s 2021 guideline, citing seven ispaghula trials with 499 patients, recommends soluble but not insoluble fibre for global IBS symptoms, a strong recommendation based on moderate-quality evidence. EMA’s monograph covers the husk only as an adjunct in constipation-predominant IBS.

Cholesterol: Jovanovski and colleagues (American Journal of Clinical Nutrition 2018) pooled 28 randomised trials with 1,924 participants. A median dose of about 10.2 g of psyllium a day lowered LDL cholesterol by 0.33 mmol/L (roughly 13 mg/dL), non-HDL cholesterol by 0.39 mmol/L, and apolipoprotein B by 0.05 g/L, with moderate-quality evidence for LDL. EMA describes an LDL reduction of about 7% in mild to moderate hypercholesterolaemia, notes that no studies have measured heart attacks, strokes, or deaths, and says use as an adjunct to diet in high cholesterol requires medical supervision. Brum and colleagues (American Journal of Cardiology 2018) pooled three trials lasting 4–12 weeks and reported that adding psyllium to a statin lowered LDL by about as much as doubling the statin dose; three of the five authors worked for Procter & Gamble.

Blood sugar: Gibb and colleagues (American Journal of Clinical Nutrition 2015) analysed 35 randomised trials and reported that in people being treated for type 2 diabetes, psyllium taken before meals for several weeks lowered fasting glucose by 37.0 mg/dL and HbA1c by 0.97 percentage points. There was no glucose lowering in people with normal blood sugar and only a modest effect in prediabetes. The analysis was written mainly by Procter & Gamble employees and drew partly on the company’s own clinical records, so independent confirmation matters. EMA advises that people with diabetes take ispaghula husk only under medical supervision because diabetes medicines may need adjusting.

EU well-established use, ispaghula husk (EMA/HMPC/199774/2012, adopted 14 May 2013): for constipation or to soften stool, adolescents, adults, and older people take 7–11 g a day in one to three doses; children aged 6 to 12 take 3–8 g a day, and use under 6 is not recommended. As a fibre supplement in constipation-predominant IBS or alongside diet for high cholesterol, adults take 7–20 g a day in one to three doses, not recommended under 12. The laxative effect starts after 12–24 hours. If constipation persists for more than three days of use, consult a doctor or pharmacist.

EU well-established use, ispaghula seed (EMA/HMPC/304390/2012, adopted 14 May 2013): 8–40 g a day in two or three doses for adolescents and adults, 4–25 g for children aged 6 to 12, for constipation and stool softening only. Psyllium seed from P. afra or P. indica has a separate monograph at 25–40 g a day in three doses. For every product, EMA’s method of use is the same: take at least 30 ml of water, milk, fruit juice, or similar liquid for each gram, either mixing the product into the liquid or swallowing it and then drinking enough liquid, and keep drinking adequately through the day. Take it during the day, not immediately before bed, and at least half an hour to an hour before or after other medicines. When preparing powder, avoid breathing it in, to reduce the risk of becoming sensitised.

In food, the US health claim applies to products providing at least 1.7 g of soluble fibre from psyllium husk per serving, as part of a diet low in saturated fat and cholesterol that supplies 7 g or more a day. Such foods containing dry or incompletely hydrated husk must carry a notice that they should be eaten with at least a full glass of liquid, may cause choking otherwise, and should not be eaten by people with difficulty swallowing. EMA notes that flatulence usually settles as treatment continues. The fluid rule applies to capsules and granules as well as loose powder.