Rhubarb is a vegetable that most people cook like a fruit. You eat only the leaf stalks, which are tart, and the large leaves are poisonous. Raw stalks hold just 1.1 g of sugar per 100 g, so the sweetness of a pie or crumble comes from what is added. The same genus also gives medicinal rhubarb, a dried root used for centuries in Chinese medicine, which is a different use and is labeled as root in the studies below.
The leaves contain oxalic acid, typically about 0.5% of the leaf, and anthrone glycosides, and extension services say they should never be eaten. Which compound does the harm is still debated, and serious poisonings are rare. The stalks are safe to eat, but they are also one of the higher-oxalate vegetables, which is why rhubarb comes up with kidney stones.
In Yorkshire, England, the first rhubarb of the year is grown in the dark. Growers move the plants into sheds with all light shut out, and pickers work by candlelight because light stops the growth. Forced rhubarb of this kind is tenderer and sweeter than outdoor rhubarb.
Health benefits of rhubarb
The top findings from 20 studies, strongest evidence first
What the stars mean
- Strong. Several randomized trials, pooled in a meta-analysis, point the same way, or regulators (FDA or EFSA) have approved the claim.
- Moderate. Good randomized trials support it, but there are fewer of them, or their results vary.
- Limited. Small, short or single trials, or mixed results. Promising, but it needs confirmation.
Population and lab studies get no stars: they show a link or a mechanism, not proof.
How we rate evidence →- ★★Fewer menopause symptoms, from a root extractA branded root extract, not the stalks, cut menopause symptom scores by 15.12 points more than control therapy across 4 trials. In one 12-week trial, hot flushes were fewer and milder.
- ★Lower “bad” LDL cholesterolTen men with high cholesterol ate 27 g a day of rhubarb stalk fiber powder for 4 weeks, and LDL fell 9%. There was no control group, and it was powder, not cooked stalks.
- ★Improved stool frequency and consistencyIn middle-aged adults, a rhubarb root extract (12.5 or 25 mg a day for 30 days) beat placebo. It was a supplement, not the stalks.
- ★Adds oxalate to urine, a kidney stone riskIn 9 healthy adults on controlled diets, researchers counted rhubarb among the high-risk foods for kidney stones because of the oxalate it adds to urine. The study gave no figure for rhubarb alone.
- Population studyLinked to kidney failure in one caseA person with type 1 diabetes developed acute kidney failure with oxalate crystals after eating too much rhubarb. One case cannot show how much is too much.
All 20 studies, strongest evidence first
A standardized extract from the root of rhapontic rhubarb, not the stalk, lowered menopause symptom scores across 4 trials
Meta-analysis of 4 trials (390 women) of ERr 731, a branded extract from the root of Rheum rhaponticum sold for menopause symptoms. This is a different use from eating the stalks. The Menopause Rating Scale score fell by 15.12 points more than with control therapy. The authors note possible bias and high heterogeneity and ask for more trials.
The root extract ERr 731 taken for 12 weeks cut menopause symptom scores and hot flushes more than placebo
Double-blind randomized trial in 109 perimenopausal women (54 on one tablet a day, 55 on placebo). Total symptom scores fell more on the extract (P under 0.0001), and hot flushes were fewer and milder from week 4. No adverse events were linked to it. This was a root extract in a tablet, not rhubarb stalks.
27 g a day of rhubarb stalk fiber for 4 weeks lowered LDL cholesterol by 9% in men with high cholesterol
Ten men with high cholesterol ate 27 g a day of a dried fiber powder made from rhubarb stalks (74% fiber) while the rest of their diet stayed the same. Total cholesterol fell 8% and HDL did not change. Both levels returned to baseline 1 month after the fiber stopped. The abstract describes no control group, and this was a fiber powder, not cooked stalks.
In 9 healthy adults on controlled diets, researchers counted rhubarb among the high-risk foods for kidney stones because of the oxalate it adds to urine
Nine healthy adults ate a low-oxalate diet with and without single oxalate-rich foods. Dietary oxalate made up to two-thirds of the oxalate in urine, and how much was absorbed depended on the food. The authors rated chocolate, peanuts, beetroot, rhubarb and spinach as high-risk foods, and tea and strawberries as not a real risk. The abstract gives no figure for rhubarb alone.
Oxalate loads given into the stomach, including rhubarb, were absorbed there: up to 62% reached the urine after 6 hours
Experiment in 6 adults fed by tube, with a balloon holding the load in the stomach. The 5 mmol oxalate loads came as sodium oxalate, sodium oxalate with calcium gluconate, rhubarb or spinach. Calcium oxalate was absorbed as well as soluble oxalate, with 15 to 21% in urine after 2 hours and 24 to 45% after 4 hours. This setup holds food in the stomach unusually long, and the abstract gives no figure for rhubarb alone.
In one healthy volunteer, only about 2.4% of the oxalate in spinach and rhubarb meals was absorbed
Study of a single healthy person who ate oxalate-rich meals of spinach and rhubarb, with and without added labeled oxalate. Calcium oxalate was absorbed to the same extent as soluble oxalate, mostly between 1 and 8 hours after the meal in the upper small bowel. One person cannot stand for everyone, and the result is far lower than in the stomach experiment above.
A rhubarb root extract taken for 30 days improved stool frequency and consistency in middle-aged adults
Double-blind randomized trial in middle-aged volunteers (95% women, average age 58) taking 12.5 or 25 mg a day of the extract, dosed by its rhein content, or placebo. Both doses improved stool frequency, consistency and perceived transit compared with placebo, and the extract was safe over the 30 days. The article describes a dry extract of Rheum palmatum root, a supplement and not the stalks, and the trial was small.
Rhubarb powder solution sprayed through a gastroscope stopped upper gut bleeding more often than norepinephrine within 48 hours in 14 trials
Meta-analysis of 14 randomized trials (1,493 patients) comparing sprayed rhubarb powder solution with norepinephrine for sudden non-varicose upper gut bleeding. At 0.1 to 0.15 g/mL the hemostatic effect was higher at 48 hours (relative risk 1.18) and rebleeding was lower. This is a hospital procedure with a medicinal powder, not food, and the authors call the trials small and of substandard quality.
In three large US cohorts, the highest dietary oxalate intake went with a 21 to 22% higher risk of kidney stones in men and older women
Cohorts of 45,985 men, 92,872 older women and 101,824 younger women, with 4,605 stones over a combined 44 years. Spinach gave over 40% of oxalate, and 8 or more servings a month went with a 30% (men) and 34% (older women) higher risk. Younger women showed no link. The abstract does not mention rhubarb, and the authors say the data do not make dietary oxalate a major risk factor.
In a review of 108 people with biopsy-proven oxalate kidney damage, excess dietary oxalate was behind 20% of cases and 55% needed dialysis
Systematic review of 57 case reports and 10 case series of secondary oxalate nephropathy in native or transplanted kidneys. Fat malabsorption was the most common cause (88%), followed by excessive dietary oxalate (20%), and 33% of patients died. The authors call the condition rare but potentially devastating. The review is not specific to rhubarb.
Eating too much rhubarb was linked to acute kidney failure from oxalate crystals in a person with type 1 diabetes
Case report of one patient with type 1 diabetes and previously normal kidney function. A biopsy showed oxalate crystals in the kidney tubules and blood oxalate was raised. The authors say excessive dietary oxalate can cause acute kidney failure, especially in people with existing kidney disease. One case cannot show how much rhubarb is too much.
Women who kept taking the root extract ERr 731 for up to 96 weeks had symptom scores that kept falling, with no related adverse events
Observational follow-up of the 109-woman trial above: 80 women joined the first 48 weeks (39 from the extract group, 41 from placebo) and 51 continued for a second 48 weeks. Women who switched from placebo had scores like those of the extract group after 18 weeks on it. There was no placebo comparison in this follow-up, and the product is a root extract, not the stalks.
Rhubarb stalk fiber in mice fed cholesterol lowered plasma cholesterol by 13% and liver cholesterol by 34%
Study in mice, not people. Mice ate a diet with 50 g of rhubarb fiber per kg for 4 weeks. They lost more bile acids in their feces and had higher activity of cholesterol 7 alpha-hydroxylase, the enzyme that turns cholesterol into bile acids, which the authors say may explain the cholesterol drop.
Rhubarb stalk fiber did not lower cholesterol in diabetic rats
Study in two rat models of diabetes, not people. The fiber changed neither plasma cholesterol nor triglycerides, though it slightly raised the activity of cholesterol 7 alpha-hydroxylase in one model. The authors saw no apparent benefit for lowering cholesterol under diabetic conditions.
Rhubarb stalk fiber at up to 5% of a rat diet did not reduce calcium absorption despite the oxalic acid in it
Study in rats, not people. Rats ate diets with 0, 1, 3 or 5% rhubarb stalk fiber, or pure oxalic acid equal to 5% fiber, for 4 weeks, with the same calcium in every diet. Calcium retention and apparent absorption rose as the rhubarb fiber rose, while cellulose lowered it. The authors tested this because the fiber is high in oxalic acid.
A compound from a water extract of rhubarb stalks killed E. coli and S. aureus bacteria in the lab
Lab study. The purified compound was active against E. coli, Aggregatibacter actinomycetemcomitans and S. aureus and slowed the growth of MCF-7 breast cancer cells without cytotoxicity. It killed slow-growing bacteria best. These are tests on plates and cells, so nothing is known about eating rhubarb.
Extracts of rhubarb stalks and roots blocked the inflammatory enzyme COX-2 in human blood vessel cells
Lab study on human endothelial cells with extracts from the stalks (petioles) and underground parts of garden rhubarb and rhapontic rhubarb, and two stilbene compounds. The extracts lowered COX-2 activity and gene expression, cytokine levels and the attachment of white blood cells. Cell and computer tests only.
Extracts of rhubarb stalks and roots reduced clotting of human blood plasma by about 40% in the lab
Lab study using blood plasma and vessel cells with extracts from the stalks (petioles) and roots of two Rheum species. The extracts blocked thrombin and factor Xa, two clotting enzymes, which points to an anticoagulant action. This is a test tube result, not a trial in people.
Mice given a rhubarb root extract were protected from diet-induced obesity and diabetes
Study in mice, not people. Mice on a high-fat, high-sugar diet got 0.3% rhubarb extract for 8 weeks and stayed leaner, with less liver fat and no diabetes, without eating less. Their gut bacterium Akkermansia muciniphila increased. The article describes an extract of Rheum palmatum root, and one author co-founded a company working on Akkermansia.
Fermenting rhubarb juice with one lactic acid bacterium for 96 hours cut its oxalate by 17.5%
Lab study that screened 34 lactic acid bacteria strains from traditional dairy products. With the best strain, Levilactobacillus brevis, oxalate fell from 10.44 to 8.50 mmol/L. The authors aim at low-oxalate drinks for people at risk of kidney stones, and no one has tested whether such a juice changes stone risk.
Who should be careful with rhubarb
Most people can eat rhubarb stalks freely. Take a little care if one of these applies:
- The leaves. Never eat them. They hold oxalic acid and other toxins, serious poisoning can cause kidney failure, and deaths have been reported but are rare. Cut the leaves off and throw them away.
- Kidney stones or kidney disease. Rhubarb is high in oxalate, and web and app sources list between 511 and 984 mg per 100 g. The NIDDK says people who have had calcium oxalate stones may want to avoid it, and one case report links a large amount of rhubarb to acute kidney failure in a person with type 1 diabetes. For everyone else, a 1999 review says occasional high-oxalate foods are no problem.
- Warfarin. Raw rhubarb has 29 µg of vitamin K per 100 g, which can change how this blood thinner works. You do not need to avoid it; keep the amount steady from week to week and check with your clinic before big changes.
How to choose, store and eat rhubarb
- Raw or stewed: raw stalks are very tart and have 21 calories and 1.1 g of sugar per 100 g. Pies, crisps and jams are not low in calories because of the sugar added to them.
- Cooked in water: a 1999 review says soaking and cooking high-oxalate foods leaches some oxalate out, and in a lab test, fermenting rhubarb juice for 96 hours cut its oxalate by 17.5%.
- Red, pink or green: the color comes from anthocyanins and varies with the variety and how the plant is grown. It does not show whether a stalk is fit to cook, and forced rhubarb is the tender, sweeter kind.
Choose fresh, crisp stalks and cut off any leaves right away. Keep the stalks in a plastic bag in the refrigerator, or cut and freeze them, blanching for 1 minute in boiling water for better flavor and color. Two extension services advise throwing away stalks that froze on the plant and turned mushy, because oxalic acid may have moved in from the leaves.
Sources
- Are rhubarb leaves toxic?. Oregon State University Extension.
- Rhubarb. University of Illinois Extension. 2017.
- Prairie Fare: Rhubarb, anyone? North Dakota State University Extension.
- Rhubarb. Wikipedia (leaf oxalic acid content, anthrone glycosides, stalk color).
- Eating, diet, and nutrition for kidney stones. NIDDK, National Institutes of Health.
- Noonan SC, Savage GP. Oxalate content of foods and its effect on humans. Asia Pac J Clin Nutr. 1999.
- Attalla K, De S, Monga M. Oxalate content of food: a tangled web. Urology. 2014.
- Tallqvist H, Vaananen I. Death of a child from oxalic acid poisoning due to eating rhubarb leaves. Ann Paediatr Fenn. 1960.
- Kalliala H, Kauste O. Ingestion of rhubarb leaves as cause of oxalic acid poisoning. Ann Paediatr Fenn. 1964.
- Dietary advice for patients taking warfarin. Cambridge University Hospitals NHS Foundation Trust.
- Anticoagulant medicines: considerations. NHS.
- EFSA Panel on Food Additives and Nutrient Sources added to Food. Safety of hydroxyanthracene derivatives for use in food. EFSA J. 2018.
- EFSA Panel on Nutrition, Novel Foods and Food Allergens. 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 J. 2024.
History of rhubarb
Rhubarb began in the mountains of Asia. Medicinal rhubarb was called “the great yellow” in China, and a text thought to be about 1,800 years old already describes its use. It was used as a medicine, and trade carried it along the Silk Road to the West. Marco Polo found it grown in the mountains of Tangut province.
The name is a story in itself. It comes from Greek rha barbaron, “foreign rha”, and rha was the ancient name of the Volga River. A Japanese scholar traces the edible rhubarb, Rheum rhaponticum, to the Volga and Black Sea (Pontus) regions, which gave it the name rhaponticum.
Travel across Asia made the root costly. It sold for several times the price of cinnamon, opium or saffron, and the envoy Clavijo, writing about his 1403 to 1405 journey to Samarkand, listed it among the best goods arriving there. It reached Europe in the 14th century through Aleppo and Smyrna as “Turkish rhubarb”, and later “Russian rhubarb” was the most valued.
High prices pushed Europeans to grow their own. Seeds from Abyssinia reached the Edinburgh Botanic Garden in 1774 and rhubarb was harvested in Scotland by 1786. The kitchen use took off in the 18th century as sugar got cheaper, and one herbal dates English cooking with it to 1820. In America, John Bartram grew it in Philadelphia from the 1730s, and Thomas Jefferson planted it at Monticello in 1809 and 1811.
Forcing in the dark was developed in the early 1800s in West Yorkshire. At the peak, up to 200 tons of rhubarb a day left the area before 1939, and the region once made 90% of the world’s winter forced rhubarb. Twelve farmers applied for protection and Yorkshire Forced Rhubarb got EU protected designation of origin in 2010.
The leaves had a darker moment. During World War I, Britain mistakenly recommended them as a food and people were poisoned, and the printed advice was found again in World War II, with more deaths.
Sources
- Rhubarb. Wikipedia.
- Rhubarb Triangle. Wikipedia.
- Uchibayashi M. Rhubarb in the East and the West (in Japanese). Yakushigaku Zasshi. 2001.
- Liudvytska O, Ponczek MB, Ciesielski O, et al. Rheum rhaponticum and Rheum rhabarbarum extracts as modulators of endothelial cell inflammatory response. Nutrients. 2023.
Frequently asked questions about rhubarb
Is rhubarb good for you?
For most people, the stalks are a low-calorie food, but the evidence for health benefits is thin. Raw rhubarb has 21 calories, 1.8 g of fiber and 29 µg of vitamin K per 100 g, which is 24% of the daily value, and 1 cup (122 g) gives 30%. The only trial of the stalk itself was small: 27 g a day of a dried stalk fiber powder lowered LDL cholesterol by 9% in 10 men, with no control group. Eat the stalks, never the leaves.
Are rhubarb leaves poisonous?
Yes. The leaves contain oxalic acid, typically about 0.5% of the leaf, and anthrone glycosides, and extension services say people should never eat them. Serious poisoning can cause kidney failure, and deaths have been reported but are rare; Finnish doctors described the death of a child who ate the leaves in 1960. Cut the leaves off as soon as you buy or harvest the stalks.
Is rhubarb a fruit or a vegetable?
Botanically it is a vegetable, because you eat the leaf stalk, but cooks use it like a fruit. Because the stalks are tart, recipes add sugar, and desserts made with rhubarb are not low in calories as a result.
Can you eat rhubarb raw?
Yes, the stalks are safe to eat raw, but they are very tart, so most people stew or bake them with sugar. A 1999 review says soaking and cooking high-oxalate foods leaches some oxalate out, so cooking in water may lower it a little. No study here measured this for rhubarb.
Is rhubarb high in oxalate, and does it cause kidney stones?
Yes, it is one of the higher-oxalate vegetables: web and app sources list between 511 and 984 mg per 100 g. In a study of 9 adults, rhubarb was counted among the high-risk foods for stone formers, and the NIDDK says people who have had calcium oxalate stones may want to avoid it. A large US study of oxalate and stones named spinach, not rhubarb, and found only a modest link, and a 1999 review says occasional high-oxalate foods are no problem for most people. If you form stones, ask your clinic how much is right for you.
Does rhubarb make you poop?
The root does, and no study here tested whether the stalks do. In a 30-day trial, a rhubarb root extract dosed at 12.5 or 25 mg of rhein a day improved stool frequency and consistency in middle-aged adults compared with placebo. The European Food Safety Authority said in 2018 that hydroxyanthracene compounds in such extracts should be treated as genotoxic and carcinogenic unless data show otherwise, and in 2024 that the safety of root preparations could not be established. Talk to a clinician before using a root supplement.
Is rhubarb good for menopause?
Not the stalks. A branded extract from the root of rhapontic rhubarb, taken as a tablet, cut menopause symptom scores more than placebo in a 109-woman trial, and a meta-analysis of 4 trials (390 women) agreed, although the authors note possible bias and high heterogeneity. Nobody has tested cooked rhubarb stalks for menopause symptoms.
Is rhubarb good for weight loss?
No study here tested it. Raw rhubarb has 21 calories and 1.8 g of fiber per 100 g, so the stalks fill a plate for few calories, but pies, crisps and jams are not low in calories because of the added sugar. A rhubarb root extract kept mice lean on a high-fat diet, but that was a mouse study and not a result for people.