Rhubarb

Rhubarb is one of the friendliest oddballs in the kitchen: botanically a vegetable, but treated like a fruit. What we eat are the thick, tart, reddish-to-green stalks (the leaf stems), usually sweetened and cooked into pies, crumbles, jams, and compotes. It has a bracing, lemon-sour bite that becomes lovely once it meets a little sugar and heat. But rhubarb comes with one rule that matters more than any recipe: never eat the leaves. The big, floppy green leaves are toxic and must always be cut off and thrown away — only the stalks are food. This page explains what rhubarb is, that critical safety point in plain terms, what nutrition the stalks actually offer, the oxalate question for people who form kidney stones, and how to buy, store, and cook it honestly (including the sugar you usually add). The evidence here is a mix of solid food chemistry and a handful of old but sobering poisoning case reports; we will tell you which is which.

Table of Contents

  1. What Rhubarb Is
  2. Safety First: Never Eat the Leaves
  3. Nutritional Profile of the Stalks
  4. Anthocyanins and Antioxidants (the Red Color)
  5. Fiber and the Traditional Laxative Reputation
  6. The Oxalate Question in the Edible Stalks
  7. Heart and Bone Context
  8. How to Use Rhubarb
  9. How to Select and Store
  10. Safety and Who Should Be Careful
  11. Research Papers
  12. Connections
  13. Featured Videos

What Rhubarb Is

Rhubarb (Rheum rhabarbarum, and the garden hybrid often listed as Rheum × hybridum) is a hardy perennial in the buckwheat family, Polygonaceae — the same family as sorrel and buckwheat, which helps explain its sharp, sour taste. Plant it once and, in a cool climate, it comes back for years, sending up big triangular leaves on top of stout stalks each spring. Those stalks, technically the leaf petioles, are the only part we eat.

Because rhubarb is intensely tart and low in sugar on its own, cooks have always paired it with sweetness and served it in dessert-like ways — stewed with sugar, baked into pies and crumbles, cooked down into jam, or simmered into a tangy sauce. In the United States it is even legally classified as a fruit for some trade purposes, a nod to how it is used rather than what it botanically is.

One point of confusion is worth clearing up. There is a separate plant tradition built around medicinal rhubarb root — the dried underground rhizome of Asian species such as Rheum palmatum and Rheum officinale, known in Chinese medicine as "Da Huang" and used for centuries as a strong laxative and digestive remedy. That is a different part of a different (though related) plant, taken in small medicinal amounts, not a food. When this page talks about rhubarb as something you cook and eat, it means the garden stalks, not the medicinal root. We will come back to the root briefly when we discuss rhubarb's laxative reputation.

Safety First: Never Eat the Leaves

This is the single most important thing to know about rhubarb, so we put it right up front: rhubarb leaves are toxic and must never be eaten. Only the stalks are safe. When you buy or harvest rhubarb, cut the leaves off and discard them — do not add them to salads, do not cook them like spinach or chard, and do not compost-taste them out of curiosity.

The leaves contain a high concentration of oxalic acid and oxalate salts — much more than the stalks — along with other compounds. Oxalic acid in large amounts is a genuine poison: it binds calcium in the body, can irritate and damage the mouth, throat, stomach, and kidneys, and in severe cases can drop blood calcium dangerously low and injure the kidneys. Some researchers argue that additional leaf compounds, such as anthraquinone glycosides, may share the blame, and the exact culprit has been debated — but the practical bottom line does not change: the leaves are not food.

How much is dangerous? The frequently cited lethal dose of oxalic acid for an adult is roughly 15 to 30 grams, and because the leaves are "only" around half a percent oxalic acid, you would have to eat a very large quantity — on the order of several kilograms of leaf — to reach a clearly lethal dose. That is why serious rhubarb-leaf poisonings are rare, and why realistic risk from a small accidental nibble is low. But "rare" is not "never." Documented cases exist, including old pediatric fatalities recorded after children ate the leaves, and the notorious episode in Britain during the First World War when people were officially encouraged to eat rhubarb leaves as a vegetable and some were poisoned as a result. Milder exposures typically cause a sore, burning mouth and throat, nausea, vomiting, and diarrhea. None of this is worth risking. The rule is simple and absolute: eat the stalks, throw away the leaves.

Nutritional Profile of the Stalks

Here is the honest picture of what the edible stalks bring to the table. Raw rhubarb is very low in calories and low in natural sugar — it is mostly water and fiber with a scattering of vitamins and minerals. A typical 100-gram serving of raw stalk (a little under a cup, diced) provides roughly:

Two honest asterisks belong on that list. First, the calcium is misleading. Rhubarb also carries oxalate, and oxalate binds calcium into an insoluble form your body largely cannot absorb. So even though the number looks decent, rhubarb is not a good calcium source — much of that calcium leaves the body still locked to oxalate. Second, and more practically: almost nobody eats rhubarb plain. Because it is so tart, it is nearly always cooked with a good deal of added sugar. A slice of rhubarb pie or a bowl of sweetened crumble is, calorie- and sugar-wise, a dessert — the rhubarb itself is the innocent part. So the "low-calorie vegetable" description is true of the raw stalk and quietly untrue of most rhubarb dishes. If you want rhubarb's benefits without a sugar load, that is a cooking choice you get to make (more on that below).

Anthocyanins and Antioxidants (the Red Color)

The pretty red-to-crimson blush of many rhubarb stalks comes from anthocyanins — the same family of water-soluble plant pigments that color strawberries, red cabbage, and blueberries. In rhubarb the main pigments are cyanidin-based, chiefly cyanidin-3-O-rutinoside with some cyanidin-3-O-glucoside. These pigments are antioxidants, meaning they can help mop up reactive molecules, and they are part of why rhubarb shows measurable antioxidant activity in the lab.

A few grounded points keep this in perspective. The amount of anthocyanin varies enormously from one variety and growing condition to the next — measurements across many rhubarb cultivars span more than a tenfold range — so "red rhubarb is antioxidant-rich" is true in a relative, variety-dependent way, not as a fixed dose. Rhubarb also contains other polyphenols (including small amounts of the anthraquinones and stilbenes found more concentrated in the medicinal root). Importantly, color is not ripeness or safety. Green-stalked rhubarb is perfectly edible and can be just as tart and useful in the kitchen; it simply has fewer anthocyanins and so makes a less rosy pie. Buying green rhubarb is a cosmetic tradeoff, not a quality problem.

Fiber and the Traditional Laxative Reputation

Rhubarb has a long-standing reputation as something that "keeps you regular," and that reputation is real — but it mostly belongs to the root, not the stalk you put in a pie. The dried medicinal rhubarb root (Da Huang) is rich in anthraquinones — compounds such as rhein, emodin, aloe-emodin, chrysophanol, and physcion, and their glycosides. In the gut these act as stimulant laxatives: after bacteria in the colon free the active forms, they nudge the bowel wall to move things along and shift fluid into the stool. This is the same general mechanism behind senna, another traditional herbal laxative, and it is why medicinal rhubarb has been used for constipation for centuries. Because it is a stimulant laxative, the root is a short-term remedy, not a daily habit.

The edible stalks are a much gentler story. They contain only small amounts of those anthraquinones compared with the root, so any laxative nudge from a normal serving of rhubarb dessert comes mainly from ordinary dietary fiber plus the natural acids and, frankly, the sugar. Fiber supports regularity in the mild, healthy way any vegetable does. In short: if you want rhubarb's fiber, eat the stalks; the dramatic purgative effect people sometimes associate with "rhubarb" is a property of the concentrated medicinal root, not of your crumble.

The Oxalate Question in the Edible Stalks

We have to be honest that oxalate is not only a leaf problem. The stalks contain oxalate too — far less than the toxic leaves, but enough to put rhubarb near the top of the list of high-oxalate foods, alongside spinach and beet greens. For most people eating a normal, varied diet, an occasional serving of rhubarb is not a concern. But oxalate matters for one specific group.

Oxalate binds calcium, and when the body excretes it, calcium and oxalate can crystallize in the urinary tract as calcium-oxalate kidney stones — the most common kind of kidney stone. If you have a history of calcium-oxalate stones, hyperoxaluria, or the rare inherited condition primary hyperoxaluria, it is sensible to be moderate with high-oxalate foods, including rhubarb, and to follow your clinician's or dietitian's guidance. Practical, evidence-aligned steps that reduce risk include:

For everyone else, this is context, not alarm. Rhubarb is a normal part of a healthy, varied diet; the oxalate caution is aimed squarely at stone-formers, not the general public.

Heart and Bone Context

On the plus side, rhubarb stalks contribute potassium and fiber, both of which fit into a heart-healthy eating pattern — potassium helps balance sodium's effect on blood pressure, and fiber supports healthy cholesterol and steady digestion. The vitamin K in rhubarb also plays a role in bone metabolism as well as clotting. So as a low-calorie source of a few useful nutrients, the raw stalk earns modest points.

But keep the bone story honest. Despite that respectable calcium number on the label, rhubarb is a poor calcium source because its own oxalate ties the calcium up. And oxalate can slightly reduce the absorption of some minerals from the same meal. None of this makes rhubarb "bad for bones" in a normal diet — it simply means you should get your calcium from better-absorbed foods and not count on rhubarb to deliver it. Think of rhubarb as a tart, fiber-and-potassium vegetable with a signature vitamin K contribution, best enjoyed for its flavor and modest nutrition rather than as a mineral supplement.

How to Use Rhubarb

Rhubarb is genuinely fun to cook because heat and a little sweetness transform its harsh sourness into something bright and jammy. A few reliable approaches:

You usually do not need to peel rhubarb; just trim the ends. Gentle cooking is fine for the plant's polyphenols — research on rhubarb has found that reasonable cooking can retain, and in some measures even increase, the extractable polyphenol content, so a stewed rhubarb is not a nutritionally empty one.

The sugar caveat, said plainly: the reason rhubarb tastes good in desserts is a lot of added sugar, and that sugar — not the rhubarb — is the part to watch. You have options: use less sugar than a recipe calls for and lean on a sweet fruit like strawberry or a ripe pear to fill the gap; add a pinch at a time and taste; or embrace rhubarb's tartness in savory settings (a sharp sauce for pork or oily fish, for instance) where little or no sugar is needed. Enjoyed as an occasional sweetened treat, rhubarb dessert is a perfectly fine pleasure — just be honest with yourself that it is a dessert.

How to Select and Store

Choosing: look for firm, crisp stalks that snap rather than bend, with a glossy sheen. Both red and green (and pink, speckled, or two-toned) stalks are good — as noted, color reflects the variety, not ripeness or sweetness, so pick by freshness, not hue. Thinner stalks tend to be more tender. "Forced" rhubarb, grown in the dark early in the season, is a paler pink, more tender, and milder. Whatever you buy, if any leaf is still attached, cut it off and discard it before the rhubarb goes into your kitchen — never eat the leaf.

Storing: keep unwashed stalks loosely wrapped in the refrigerator, where they stay crisp for up to about a week; if they go limp, standing the cut ends in a little water can revive them. Rhubarb also freezes very well — wash, trim, chop into pieces, and freeze on a tray before bagging, so you can bake with it out of season. Frozen rhubarb goes straight into most cooked recipes without thawing.

Safety and Who Should Be Careful

Rhubarb is a safe, everyday food when you follow a few sensible rules:

Follow those, and rhubarb is exactly what it looks like: a tart, cheerful, seasonal vegetable that plays the part of a fruit — best enjoyed cooked, lightly sweetened, and with its dangerous leaves left firmly in the compost bin.

Research Papers

  1. Kolodziejczyk-Czepas J, Liudvytska O. Rheum rhaponticum and Rheum rhabarbarum: a review of phytochemistry, biological activities and therapeutic potential. Phytochemistry Reviews. 2021;20(3):589-607. doi:10.1007/s11101-020-09715-3 — comprehensive review of garden and rhapontic rhubarb constituents (anthraquinones, stilbenes, flavonoids, anthocyanins) and their biological activities.
  2. Takeoka GR, Dao L, Harden L, Pantoja A, Kuhl JC. Antioxidant activity, phenolic and anthocyanin contents of various rhubarb (Rheum spp.) varieties. International Journal of Food Science & Technology. 2013;48(1):172-178. doi:10.1111/j.1365-2621.2012.03174.x — found a more than tenfold range in anthocyanins and antioxidant capacity across 29 rhubarb varieties.
  3. Wrolstad RE, Heatherbell DA. Anthocyanin pigments of rhubarb, Canada Red. Journal of Food Science. 1968;33(6):592-594. doi:10.1111/j.1365-2621.1968.tb09080.x — classic identification of the cyanidin pigments responsible for red rhubarb's color.
  4. Will F, Dietrich H. Processing and chemical composition of rhubarb (Rheum rhabarbarum) juice. LWT – Food Science and Technology. 2013;50(2):673-678. doi:10.1016/j.lwt.2012.07.029 — documents rhubarb's low sugar, high acidity (mainly malic, with oxalic and citric acid), and high potassium, with calcium precipitated out by oxalate.
  5. McDougall GJ, Dobson P, Jordan-Mahy N. Effect of different cooking regimes on rhubarb polyphenols. Food Chemistry. 2010;119(2):758-764. doi:10.1016/j.foodchem.2009.07.030 — showed that gentle cooking can retain, and in some measures increase, rhubarb's extractable polyphenols.
  6. Salgado N, Silva MA, Figueira ME, Costa HS, Albuquerque TG. Oxalate in foods: extraction conditions, analytical methods, occurrence, and health implications. Foods. 2023;12(17):3201. doi:10.3390/foods12173201 — reviews oxalate across the diet and its relevance to kidney-stone risk, with rhubarb among the high-oxalate foods.
  7. Noonan SC, Savage GP. Oxalate content of foods and its effect on humans. Asia Pacific Journal of Clinical Nutrition. 1999;8(1):64-74. doi:10.1046/j.1440-6047.1999.00038.x — landmark review noting rhubarb, spinach, and beet among the highest-oxalate foods and that soaking and cooking reduce oxalate by leaching.
  8. Holmes RP, Assimos DG. The impact of dietary oxalate on kidney stone formation. Urological Research. 2004;32(5):311-316. doi:10.1007/s00240-004-0437-3 — examines how dietary oxalate is absorbed and contributes to calcium-oxalate stone formation.
  9. Mitchell T, Kumar P, Reddy T, Wood KD, Knight J, Assimos DG, Holmes RP. Dietary oxalate and kidney stone formation. American Journal of Physiology-Renal Physiology. 2019;316(3):F409-F413. doi:10.1152/ajprenal.00373.2018 — about half of urinary oxalate can derive from diet; high excreters may benefit from reducing oxalate intake.
  10. Sun H, Luo G, Chen D, Xiang Z. A comprehensive and system review for the pharmacological mechanism of action of rhein, an active anthraquinone ingredient. Frontiers in Pharmacology. 2016;7:247. doi:10.3389/fphar.2016.00247 — reviews rhein, one of the anthraquinones behind rhubarb root's traditional laxative action.
  11. Tallqvist H, Väänänen I. Death of a child from oxalic acid poisoning due to eating rhubarb leaves. Annales Paediatriae Fenniae. 1960;6:144-147. PubMed: PMID 13836748 — documented pediatric fatality after ingestion of rhubarb leaves.
  12. Kalliala H, Kauste O. Ingestion of rhubarb leaves as cause of oxalic acid poisoning. Annales Paediatriae Fenniae. 1964;10:228-231. PubMed: PMID 14166252 — case report of oxalic acid poisoning from eating rhubarb leaves.

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Connections

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