Rhubarb is a leaf stalk, not a fruit, and the leaves are not eaten. The stalks are among the richest foods measured: in one New Zealand study, raw stalks had 986.7 mg per 100 g, of which 287.3 mg was soluble oxalate. Cooking helps: boiling cut the soluble oxalate to 80.7 mg, a 72% drop, because it leaches into the water. The National Kidney Foundation says limiting very high oxalate foods such as rhubarb may be warranted for people with high urine oxalate despite getting enough calcium. 100 g raw gives 29.3 µg of vitamin K1, 32.6% of the 90 µg US for women.
Figures and sources are under Show the numbers.
Whose daily amount?
aged 31–50
ID card
Scientific name
Rheum rhabarbarum
Kingdom
plant
Family
Polygonaceae
Part eaten
leaf stalk
In the kitchen
cooked as a fruit
Botanically a leaf stalk, not a fruit. The leaves are not eaten.
100 g raw, for a 31–50-year-old woman, 70 kg. Each compound on its own; they are never added together.
: 987 mg in 100 g, no established safety limit. Human observational study
What changes it
Oxalate: Boiling rhubarb stalks for 10 minutes and discarding the water cut soluble 72% (287.3 to 80.7 mg/100 g) and total oxalate 23% (986.7 to 756.3). Across vegetables, boiling cut soluble oxalate 30–87%. [source]
Ripe fruit is the one part of a plant that 'wants' to be eaten, so its seeds get spread, and it drops its defenses as it ripens. Green tomatoes carry 0.9–55 mg of tomatine per 100 g; red ones 0.03–0.08 mg (Friedman & Levin 1995). Seeds, roots, tubers and leaves stay defended.
The US National Academies: 'The lower limit of dietary carbohydrate compatible with life apparently is zero, provided that adequate amounts of protein and fat are consumed.' The same report says the amount that gives optimal health 'is unknown', and still sets a recommended 130 g a day. [IOM 2005, p. 275][RDA 130 g a day]
The same 100 g against five sets of daily amounts for adults aged 31–50: US/Canada (National Academies), UK (PHE 2016), EU (EFSA), Australia/NZ (NHMRC) and WHO/FAO. Your choice is highlighted. Each line names its type (RDA, RNI, PRI, RDI, AI, and so on) and links to its source. Label amounts, with no absorption factors. Where a body sets no value, it says so; no other body's figure is used instead.
Nutrient
Per 100 g raw
Daily amounts, woman 31–50
Protein
0.9 g
US/Canada (your choice)1.96% of 46 g [RDA][source]
WHO1.55% of 58.1 g [safe level][source]0.83 per kg body weight × 70 kgfor top-quality protein (PDCAAS 1.0): "The value accepted for the safe level of intake is 0.83 g/kg per day, for proteins with a protein digestibility-corrected amino acid score value of 1.0. (PDF p. 256)"
Fiber
1.8 g
US/Canada (your choice)7.2% of 25 g [AI][source]total fiber
WHO0.374–1.12% of 19.6–58.8 mg, depends on diet [RNI][source]depends on diet: WHO gives one figure for each level of iron absorption from the diet (15%, 12%, 10% and 5%)
Zinc
0.1 mg
US/Canada (your choice)1.25% of 8 mg [RDA][source]
WHO1.02–3.33% of 3–9.8 mg, depends on diet [RNI][source]depends on diet: WHO gives one figure for each level of zinc absorption from the diet (high, moderate and low)
Other nutrients with a daily amount
Nutrient
Per 100 g raw
Daily amounts, woman 31–50
Vitamin D
0 µg (assumed zero by USDA)
US/Canada (your choice)0% of 15 µg [RDA][source]every food is by USDA
Australia/NZ0.2% of 2 g [SDT][source]NHMRC public consultation on sodium closed 30 Sep 2026; values may be revisedadequate intake (): 460–920 mg/day; shown for reference, no %
No absorption figure has been sourced for this food yet, so label amounts are shown unadjusted.
What comes with it: what the carbohydrate becomes
Per 100 g as eaten, from UK CoFID 2021 (McCance and Widdowson). CoFID gives starch and sugars as monosaccharide equivalents, so half of sucrose counts as glucose and half as fructose. This is a different measure from USDA's “carbohydrate, by difference” in the table above, and the two are never mixed.
rhubarb
Most of the carbohydrate in raw rhubarb is sugar. 100 g ends up as about 0.45 g of glucose and about 0.45 g of fructose.
Becomes glucosefree glucose + starch + half of sucrose
Boiling rhubarb stalks for 10 minutes and discarding the water cut soluble oxalate 72% (287.3 to 80.7 mg/100 g) and total oxalate 23% (986.7 to 756.3). Across vegetables, boiling cut soluble oxalate 30–87%. [source]
Threshold
No established threshold[source]No established threshold: no EFSA/JECFA/WHO/FDA value for . Clinical context only, not a safety limit: the Oxalosis & Hyperoxaluria Foundation gives a low-oxalate diet target of under 100 mg/day, and 'often under 50 mg per day' for people with significantly elevated urinary oxalate. The National Kidney Foundation says limiting very high-oxalate foods 'such as spinach, Swiss chard, almonds, navy beans, beets and rhubarb may be warranted' and advises eating calcium-rich foods at the same meal.
Effect
In three large US cohorts, the highest vs lowest fifth of dietary intake was linked to about 21–22% higher kidney stone risk in men and older women, but the authors concluded dietary oxalate is not a major risk factor for stones. Human observational study
Over time
Repeated intake: kidney stones
Most kidney stones are calcium , and stone crystals develop over weeks or months. In a large US study, men and older women eating the most oxalate had about a 21–22% higher risk of stones than those eating the least; in younger women there was no link. The authors concluded that dietary oxalate is not a major risk factor. The National Kidney Foundation advises eating enough calcium-rich foods rather than strictly limiting oxalate, and says limiting very high oxalate foods may be warranted for people with high urine oxalate despite getting enough calcium. Human observational study
Acceptable daily intake: the amount you could eat every day for life without appreciable risk, set by food-safety bodies.
LOAEL
Lowest dose at which any harmful effect was seen in studies.
MOE
Margin of exposure: how many times smaller your dose is than the lowest harmful dose. Bigger is safer. EFSA says what margin it counts as 'no concern'.
RAE
Retinol activity equivalents: vitamin A counted as what your body can actually make from it.
RDA
Recommended Dietary Allowance: the US daily amount that covers the needs of nearly all healthy people of a given age and sex.
AI
Adequate Intake: the US daily amount used when there isn't enough evidence to set an RDA.
Heme iron
The form of iron in meat and fish; absorbed much better than the nonheme iron in plants.
Nonheme iron
The form of iron in plants; less well absorbed, and easily blocked by tea, cocoa and phytate.
Provitamin
Something your body can turn into a vitamin, like beta-carotene into vitamin A.
Glycoalkaloids
Natural pesticides made by potatoes, tomatoes and eggplants.
Oxalate
A compound that binds calcium; high in spinach; linked to kidney stones in large studies.
Nitrate
Found naturally in leafy and root vegetables; has a safe daily limit, but is also studied for lowering blood pressure.
Glucosinolates
The cabbage family's defense chemicals. When the plant is chewed or cut, they break down into sharp-tasting mustard oils.
Goitrin
A breakdown product of progoitrin, found in the cabbage family. At high doses it reduces how much iodine the thyroid takes up.
Phytate
A plant's phosphorus store, mostly in seeds. It binds zinc and iron in the gut, so less of them is absorbed.
Lectin
A protein that binds sugars. The lectin in raw kidney beans causes severe vomiting; thorough boiling destroys it.
Furanocoumarins
Compounds in celery, parsnip and their relatives that make skin burn more easily in sunlight.
Cucurbitacins
Very bitter defense compounds of the squash and cucumber family. Bred out of store-bought varieties; not destroyed by cooking.
Agaritine
A natural compound in white button mushrooms. Cooking reduces it; long-term mouse studies are mixed.
Evidence grade
How strong the proof is: a regulator's assessment and human trials count most; animal and cell studies least.
Assumed zero
USDA didn't measure it; it assumes none is there (for example vitamin B12 in plants).
ARfD
Acute reference dose: the most you can take in within one day, or a single meal, without appreciable health risk, set by food-safety bodies.
Cyanogenic glycosides
Plant compounds that release hydrogen cyanide when the plant's cells are crushed or chewed. Found in cassava, lima beans, bitter almonds and apple seeds.
Amygdalin
The cyanogenic glycoside in almonds and apple seeds. Bitter almonds contain hundreds of times more than sweet ones.
Isoflavones
Soy compounds that act weakly like the hormone estrogen.
