Rhubarb: strong trials about the root, thin data about the stalk

Rhubarb has two lives. In the kitchen it is a sour pink stalk that needs sugar to be edible. In clinical research it is a Chinese medicine made from the root, and nearly every strong finding filed under the name belongs to that second life. Medicinal rhubarb added to early tube feeding shortened hospital stay by 4.49 days (95% CI 6.09 to 2.90 days shorter) in 11 randomized trials in 724 adults with severe acute pancreatitis, trials run almost entirely in China with the root given as a drug. Nothing in that tells you what a crumble does. The stalk itself has been tested once, and not as food. Ten men with high cholesterol ate 27 g of dried stalk fiber a day for 4 weeks and their total cholesterol fell 8 percent and LDL 9 percent, in an uncontrolled trial with ten people and no comparison group. Both numbers went back to baseline a month after they stopped, and 27 g of fiber from blanched dried stalks is far more stalk than a bowl of stewed rhubarb. The NIH lists rhubarb among foods high in oxalic acid, and a large amount of rhubarb put one woman with type 1 diabetes and mild diabetic nephropathy into acute kidney failure with oxalate crystals through her kidney tubules. The report does not say how much she ate. One analysis found 1,235 mg of oxalate per 3.5 oz (100 g) of rhubarb, while a 2023 review advises people prone to kidney stones to keep high-oxalate foods under 40 to 50 mg a day, a limit a few grams of rhubarb already reach. For the root, the EU herbal monograph allows a nightly dose equal to 20 to 30 mg of rhein for no more than 1 week and rules it out in pregnancy, breastfeeding and children under 12. EFSA could name no daily intake of its active compounds that is free of health concern.

The numbers, per 3.5 oz (100 g)

As people eat it, per 3.5 oz (100 g)

How much is actually in it

• One analysis cited in a 2023 review found 1,235 mg of oxalate per 3.5 oz (100 g) of rhubarb. The review says 50 to 200 mg a day does not appear to cause problems for healthy people and advises stone formers to keep high-oxalate foods under 40 to 50 mg a day. — published oxalate measurements in foods; healthy people and people prone to kidney stones Evidence D source
  Rhubarb 1235 mg total oxalate per 3.5 oz (100 g) fresh weight; 50 to 200 mg a day not a problem for healthy people; under 40 to 50 mg a day advised for stone formers

What your body absorbs

• The NIH Office of Dietary Supplements lists rhubarb among the foods high in oxalic acid, a compound that binds calcium into indigestible salts. The absorption figures the agency gives, about 5 percent from spinach against 27 percent from milk, were measured on spinach and not on rhubarb. — general population, agency fact sheet for health professionals Evidence E source
  Calcium absorption about 5 percent from spinach versus 27 percent from milk, oxalic acid named as the cause

What it does to your health

• Adding medicinal rhubarb to early enteral nutrition shortened hospital stay by 4.49 days (95% CI 6.09 to 2.90 days shorter) across 11 randomized trials in 724 patients with severe acute pancreatitis. — adults hospitalized with severe acute pancreatitis, pooled from 11 randomized trials (n = 724) Evidence A source
  Length of hospital stay mean difference -4.49 days, 95% CI -6.09 to -2.90, P < .00001
• Thirty days of rhubarb extract standardized to 12.5 mg or 25 mg of rhein a day improved stool frequency and consistency compared with placebo in 39 analyzed middle aged adults with long standing transit problems. — middle aged volunteers with chronic transit problems, 95 percent women, average age 58 years (n = 42 randomized, 39 analyzed) Evidence B source
  Stool frequency and consistency and perceived transit improved in both rhubarb doses versus placebo, no effect size given in the abstract
• Ten men with high cholesterol who ate 0.95 oz (27 g) of dried rhubarb stalk fiber a day for 4 weeks lowered total cholesterol by 8 percent and LDL cholesterol by 9 percent, and both returned to baseline a month after they stopped. — ten hypercholesterolemic men, 4 weeks of supplementation then 1 month washout (n = 10) Evidence C source
  Total cholesterol -8 percent, LDL cholesterol -9 percent, HDL unchanged, return to baseline after withdrawal

Safety, limits and interactions

• The EU herbal monograph sets rhubarb root at a dose equal to 20 to 30 mg of hydroxyanthracene derivatives, counted as rhein, once a day at night, for no more than 1 week. It warns that longer use can impair bowel function and cause laxative dependence. — adolescents, adults and elderly using rhubarb root for occasional constipation Evidence E source
  Single dose equal to 20 to 30 mg hydroxyanthracene derivatives as rhein, once daily at night; not more than 1 week; long-term use to be avoided
• People taking digoxin-type heart drugs, antiarrhythmics, QT-prolonging drugs, diuretics, corticosteroids or liquorice root should ask a doctor before using rhubarb root, because laxative potassium loss can change how these act. — people on cardiac glycosides, antiarrhythmics, QT-prolonging drugs, diuretics, corticosteroids or liquorice root Evidence E source
  Potassium loss from laxative use potentiates cardiac glycosides and interacts with antiarrhythmics; consult a doctor first
• EU law records that EFSA could not name any daily intake of hydroxyanthracene derivatives free of health concern. Since 2021 food preparations of rhubarb root containing them are under Union scrutiny. — foods and food supplements placed on the EU market Evidence E source
  EFSA could set no safe daily intake of hydroxyanthracene derivatives; rhubarb root preparations containing them placed under Union scrutiny (Annex III Part C)
• In 2024 EFSA reviewed new industry studies on rhubarb root preparations and concluded that their safety cannot be established. The tests were negative, but the preparations contained a compound known to damage DNA in animals. — food preparations from rhubarb root and related HAD plants Evidence E source
  All submitted genotoxicity tests negative, but preparations poorly characterized and containing an in vivo genotoxic compound; safety cannot be established
• A 2010 toxicology review estimates that about 9.9 lb (4.5 kg) of rhubarb leaves would carry a lethal dose of oxalic acid for a 130 lb (59 kg) adult. It notes the hypothesis that recorded deaths from rhubarb involved some other substance. — humans, estimate from a rat oral LD50 of oxalic acid Evidence D source
  About 22 g oxalic acid estimated lethal for a 130 lb (59 kg) adult, equal to about 9.9 lb (4.5 kg) rhubarb leaves; fatal rhubarb cases hypothesized to involve another substance
• In the one reported case of oxalate nephropathy after eating a large amount of rhubarb, the woman reached hospital with serum creatinine 3.6 mg/dl and an estimated glomerular filtration rate of 13.3 ml/min/1.73 m2, which is stage 5 kidney failure. — the same single adult with type 1 diabetes, 52 years old, admitted after days of nausea and vomiting (n = 1) Evidence C source
  Serum creatinine 3.6 mg/dl and eGFR 13.3 ml/min/1.73 m2 by the MDRD equation at admission
• Among 15 herbal slimming products bought from websites with no physical address, one sold as containing rhubarb rhizome proved to be a prescription medicine, and the withdrawn drug sibutramine was detected in other supplements from the same purchase. — 15 diet-aid products containing crude drugs, purchased from 15 internet sites and imported to Japan (n = 15 products) Evidence C source
  1 of 15 items labeled as rhubarb rhizome was a prescription medicine, sibutramine detected in other items in the set

What people believe that the data does not support

• An umbrella review of 19 systematic reviews found that the reported mortality benefit of rhubarb in organophosphate poisoning rests on very low quality studies, and it recommends against routine use of rhubarb for that indication. — people treated for organophosphate self-poisoning, evidence pooled from 19 systematic reviews (n = 19 systematic reviews) Evidence A source
  Reported mortality reduction judged very low quality evidence, recommendation against routine use
• A meta-analysis of 118 studies of nitrate rich and polyphenol rich foods found no endurance performance benefit for rhubarb, against a trivial overall benefit for nitrate of SMD 0.15. — adults tested on endurance exercise performance across 118 studies of nitrate, polyphenol, L-arginine and L-citrulline foods (n = 118 studies) Evidence A source
  No benefit in the subgroup holding rhubarb, overall nitrate SMD 0.15 and polyphenol SMD 0.17, both p<0.001

Who this works differently for

• The EU monograph contraindicates rhubarb root in pregnancy, because of a genotoxic risk from anthranoids such as emodin, during breastfeeding, because rhein reaches breast milk, and in children under 12. — pregnant and breastfeeding women, children under 12 Evidence E source
  Contraindicated in pregnancy (genotoxic risk of anthranoids such as emodin and aloe-emodin), in lactation (rhein passes into breast milk) and under 12 years
• Eating a large amount of rhubarb caused acute kidney failure with oxalate crystals deposited in the kidney tubules in one adult with type 1 diabetes whose kidney filtration had been normal before. — one adult with type 1 diabetes, mild diabetic nephropathy and previously normal excretory renal function (n = 1) Evidence C source
  Acute crystal induced renal failure, biopsy showed prominent tubular deposition of oxalate crystals, serum oxalate raised
• In 96 adults with diabetic nephropathy, rhubarb capsules of 350 mg three times a day for 12 weeks improved clinical and biochemical measures less than keto analogs of essential amino acids did, with no difference in side effects. — 96 adults with diabetic nephropathy at one tertiary center in North India, three equal arms, 12 weeks (n = 96) Evidence B source
  Keto amino acid arm improved more than the rhubarb arm on clinical and biochemical measures, side effects not different between the two, P > 0.05

The bottom line

Two of the things rhubarb gets sold for have been tested and failed. A meta-analysis of 118 studies of nitrate rich and polyphenol rich foods found no endurance benefit in the subgroup that held rhubarb, where it was pooled with red spinach and Swiss chard, against a trivial overall nitrate effect of SMD 0.15. An umbrella review of 19 systematic reviews found that the reported mortality benefit of rhubarb in organophosphate self poisoning rests on very low quality evidence, and it recommends against routine use. Constipation is the one use with a placebo controlled trial behind it. A root extract standardized to 12.5 mg or 25 mg of rhein a day improved stool frequency and consistency over 30 days in 39 analyzed adults with long standing transit problems, most of them women near 58. That trial had about 13 people per arm, was funded by the supplement maker and reported no effect size, and the extract is a concentrate of the root rather than food. The EU herbal monograph for rhubarb root sets a dose equal to 20 to 30 mg of hydroxyanthracene derivatives, counted as rhein, once a night for no more than 1 week. It warns that longer use can impair bowel function and cause dependence on laxatives, and that trial ran about four times past the limit. People taking digoxin-type heart drugs, antiarrhythmics, QT-prolonging drugs, diuretics, corticosteroids or liquorice root are told to ask a doctor before using it, because the potassium lost to a laxative can change how these act. As a food supplement the root has been under EU scrutiny since 2021. EFSA could not name any daily intake of its hydroxyanthracene derivatives free of health concern, and in 2024 it concluded that the safety of rhubarb root preparations cannot be established. In 96 adults with diabetic nephropathy in North India, rhubarb capsules of 350 mg three times a day for 12 weeks improved clinical and biochemical measures less than keto analogs of essential amino acids did, and side effects did not differ. Who should be careful is anyone whose kidneys are already damaged. Eating a large amount of rhubarb caused acute kidney failure with oxalate crystals deposited through the kidney tubules of one 52 year old woman with type 1 diabetes and mild diabetic nephropathy, whose filtration had been normal before. She arrived with serum creatinine 3.6 mg/dl and an eGFR of 13.3 ml/min/1.73 m2, which is stage 5 kidney failure, and the report does not say how much she had eaten. One case shows that this can happen. It does not show how often. The NIH Office of Dietary Supplements lists rhubarb among the high oxalate foods that bind calcium into indigestible salts. Its absorption figures, 5 percent for spinach against 27 percent for milk, were measured on spinach, and the agency adds that in a varied diet such interactions probably have little nutritional consequence. Rhubarb root capsules bought online are a different risk from the vegetable. Among 15 herbal slimming products bought from websites with no physical address, picked on purpose from suspect sites, one item labeled as rhubarb rhizome was a prescription medicine, and sibutramine, a withdrawn drug, turned up in others from the same batch. The EU monograph rules rhubarb root out in pregnancy, because of a genotoxic risk from anthranoids such as emodin seen in experimental data, during breastfeeding, because rhein reaches breast milk, and in children under 12. We found no trial of rhubarb in pregnancy or in children. For the stalk as food, one analysis cited in a 2023 review found 1,235 mg of oxalate per 3.5 oz (100 g). The same review advises people prone to kidney stones to keep high-oxalate foods under 40 to 50 mg a day, so even a small portion of rhubarb is far above that limit. No study we found measured how much of that oxalate a person absorbs from a portion of stewed stalks. The leaves are a separate matter. A 2010 toxicology review estimates from a rat figure that about 9.9 lb (4.5 kg) of leaves would carry a lethal dose of oxalic acid for a 130 lb (59 kg) adult, and notes the hypothesis that recorded deaths from rhubarb involved some other substance. That unknown substance does not make the leaves any safer, and kidney harm, as the case above shows, comes far below a lethal dose.

Sources

1. hf2-rhub-6 · narrative review
   1235 mg total oxalates/100 g FW for rhubarb ... Hence, regular consumption of high-oxalate foods by healthy individuals as a part of a balanced and diversified diet does not appear to cause health issues if daily consumption is from 50–200 mg/day, whereas for individuals susceptible to kidney stone formation dietary modification is crucial for its prevention. For these individuals, it is recommended to limit the consumption of high-oxalate foods to less than 40–50 mg oxalate/day since they can present a health threat in these cases.
   Foods (Basel), 2023;12(17):3201, Oxalate in Foods: Extraction Conditions, Analytical Methods, Occurrence, and Health Implications · checked 2026-10-08
2. rhub-r2-06 · fact sheet
   Certain compounds in plants (e.g., oxalic acid, phytic acid) can decrease calcium absorption by forming indigestible salts with calcium [3]. As a result, absorption of calcium is only 5% for spinach, whereas it is much higher, at 27%, for milk [3]. In addition to spinach, foods with high levels of oxalic acid include collard greens, sweet potatoes, rhubarb, and beans [1].
   NIH Office of Dietary Supplements, Calcium fact sheet for health professionals · checked 2026-09-24
3. rhub-r2-01 · meta-analysis
   Eleven randomized controlled trials (724 patients) were included. Meta-analysis showed significantly shorter length of hospital stay (days) (mean difference [MD], -4.49; 95% CI, -6.09 to -2.90; P < .00001)
   JPEN J Parenter Enteral Nutr, 2020 · checked 2026-09-24
4. rhub-r2-02 · randomized controlled trial
   Subjects (95% women, average 58 years old) were randomized to three groups treated with RE at two different doses determined by its content of rhein (supplementation of 12.5 mg and 25 mg per day) vs. placebo (maltodextrin) for 30 days. ... Stool frequency and consistency, and perceived change in transit problem, transit speed and difficulty in evacuating, investigated by validated questionnaires, were improved in both groups of RE-treated volunteers compared to placebo.
   Int J Mol Sci, 2022 · checked 2026-09-24
5. rhub-r2-07 · uncontrolled clinical trial
   Ten hypercholesterolemic men were assigned to consume 27 g of ground rhubarb stalk fiber per day for 4 weeks. ... Rhubarb fiber supplementation resulted in significant lowering of serum total cholesterol (8%) and low-density lipoprotein (LDL) cholesterol (9%), while high-density lipoprotein cholesterol (HDL) concentrations remained unchanged. The depressed total and LDL cholesterol levels returned to baseline after the fiber supplementation was withdrawn for 1 month.
   J Am Coll Nutr, 1997 · checked 2026-09-24
6. hf2-rhub-1 · EU herbal monograph
   Single dose: Herbal preparation equivalent to 20-30 mg hydroxyanthracene derivatives, calculated as rhein, to be taken once daily at night. ... Not to be used for more than 1 week. ... Long-term use of stimulant laxatives should be avoided, as use for more than a brief period of treatment may lead to impaired function of the intestine and dependence on laxatives.
   European Medicines Agency, HMPC, European Union herbal monograph on Rheum palmatum L. and Rheum officinale Baillon, radix, Revision 1, EMA/HMPC/113700/2019 (2020) · checked 2026-10-08
7. hf2-rhub-3 · EU herbal monograph
   Patients taking cardiac glycosides, antiarrhythmic medicinal products, medicinal products inducing QT-prolongation, diuretics, adrenocorticosteroids or liquorice root, have to consult a doctor before taking rhubarb root concomitantly. ... Hypokalaemia (resulting from long-term laxative abuse) potentiates the action of cardiac glycosides and interacts with antiarrhythmic medicinal products.
   European Medicines Agency, HMPC, European Union herbal monograph on Rheum palmatum L. and Rheum officinale Baillon, radix, Revision 1, EMA/HMPC/113700/2019 (2020) · checked 2026-10-08
8. hf2-rhub-4 · EU regulation
   the Authority concluded that hydroxyanthracene derivatives should be regarded as genotoxic and carcinogenic unless there are specific data to the contrary and that there is a safety concern for extracts containing hydroxyanthracene derivatives although uncertainty persists. The Authority was unable to provide advice on a daily intake of hydroxyanthracene derivatives that does not give rise to concerns for human health. ... in Part C, the following entries are added in alphabetical order: ‘preparations from the root or rhizome of Rheum palmatum L., Rheum officinale Baillon and their hybrids containing hydroxyanthracene derivatives’
   Commission Regulation (EU) 2021/468 of 18 March 2021 amending Annex III to Regulation (EC) No 1925/2006 as regards botanical species containing hydroxyanthracene derivatives, OJ L 96 · checked 2026-10-08
9. hf2-rhub-5 · EFSA scientific opinion
   All the results of the genotoxicity studies on plant preparations were negative. ... In line with the EFSA Scientific Committee statement on genotoxicity assessment of chemical mixtures, considering the presence of an in vivo genotoxic compound, the plant preparations used in these studies have to be considered of concern for genotoxicity. Thus, the safety of preparations containing HADs from the root or rhizome of Rheum palmatum L., Rheum officinale Baill. and their hybrids
   EFSA NDA Panel, Scientific Opinion on additional scientific data related to the safety of preparations of Rheum palmatum L., Rheum officinale Baill. and their hybrids, Rhamnus purshiana DC., Rhamnus frangula L. and Cassia senna L., EFSA Journal 2024;22(5):e8766 · checked 2026-10-08
10. hf2-rhub-7 · narrative review
    Oxalic acid (oxalate) is generally found in rhubarb (0.2–1.3%) ... Using the oral LD 50 value of 375 mg/kg in rats, it has been estimated that ingestion of approximately 22 g of oxalic acid could be lethal to a 59 kg human [ 85 ]. Because approximately 4.5 kg of rhubarb leaves would have to be ingested in order to achieve a lethal dose, it has been hypothesized that documented cases of fatal rhubarb poisoning in humans were due to consumption of some other substance than oxalic acid [ 67 ].
    Dolan LC, Matulka RA, Burdock GA. Naturally occurring food toxins. Toxins (Basel), 2010;2(9):2289-2332 · checked 2026-10-08
11. rhub-r2-05 · case report
    On admission an elevated serum creatinine was noted, with creatinine levels initially being 3.6 mg/dl and an estimated glomerular filtration rate (eGFR, according to the modified of diet in renal disease (MDRD) equation) of 13.3 ml/min/1.73 m2.
    BMC Nephrol, 2012 · checked 2026-09-24
12. rhub-r2-10 · cross-sectional study
    Diet-aid products containing Bukuryo (Poria sclerotium), Bakumondo (Ophiopogonis tuber), or Daio (rhubarb rhizome) were purchased through websites that did not provide physical addresses or which advertised misleading medicines ... One item stated to contain rhubarb rhizome was identified as a prescription medicine ... Sibutramine was detected in items confirmed to be supplements, including those containing Poria sclerotium and Ophiopogonis tuber.
    BMC Complement Altern Med, 2015 · checked 2026-09-24
13. rhub-r2-03 · umbrella review
    The systematic reviews and meta-analyses on gastric lavage, plasma exchange with hemoperfusion, lipid emulsions, magnesium sulfate, penehyclidine, rhubarb, and xuebijing have reported significant reductions in mortality, but the evidence comes from very low-quality studies.
    West J Emerg Med, 2026 · checked 2026-09-24
14. rhub-r2-08 · meta-analysis
    Among nitrate-rich foods, beneficial effects were seen for beetroot, but not red spinach or Swiss chard and rhubarb.
    J Int Soc Sports Nutr, 2021 · checked 2026-09-24
15. hf2-rhub-2 · EU herbal monograph
    The use in children under 12 years of age is contraindicated (see section 4.3 Contraindications). ... The use during pregnancy is contraindicated due to experimental data concerning a genotoxic risk of several anthranoids, e.g. emodin and aloeemodin. Lactation The use during lactation is contraindicated because after administration of anthranoids, ... active metabolites, such as rhein, were excreted in breast milk in small amounts.
    European Medicines Agency, HMPC, European Union herbal monograph on Rheum palmatum L. and Rheum officinale Baillon, radix, Revision 1, EMA/HMPC/113700/2019 (2020) · checked 2026-10-08
16. rhub-r2-04 · case report
    Here, we describe a case of acute crystal-induced renal failure associated with excessive ingestion of rhubarb in a type 1 diabetic with previously normal excretory renal function. Renal biopsy revealed mild mesangial sclerosis, but prominent tubular deposition of oxalate crystals in the kidney.
    BMC Nephrol, 2012 · checked 2026-09-24
17. rhub-r2-09 · randomized controlled trial
    Group II (rhubarb) that received conservative management along with rhubarb capsule (350 mg, thrice daily) ... The KAA group showed more marked improvement in clinical features as well as biochemical parameters compared to the rhubarb group. ... There was no statistical difference between the rhubarb and KAA groups with respect to side effects (P > 0.05).
    Saudi J Kidney Dis Transpl, 2016 · checked 2026-09-24