Iceberg lettuce is 95.6% water, but it still carries : 84.4–87.5 mg per 100 g (EU median and mean). At the mean, about 296 g reaches the acceptable daily intake for a 70 kg adult (259 mg). The EU caps iceberg at 2,000 mg per kg grown outdoors and 2,500 mg per kg grown under cover. 100 g has 24.1 µg vitamin K1, 26.8% of the 90 µg US for women.
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
1.2 g
US/Canada (your choice)4.8% of 25 g [AI][source]total fiber
WHO0.697–2.09% 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
0.15 mg
US/Canada (your choice)1.88% of 8 mg [RDA][source]
WHO1.53–5% 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/NZ0.5% 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.
iceberg lettuce
UK CoFID 2021 has no entry for raw iceberg lettuce. USDA lists 1.97 g of sugars in 100 g and gives no starch figure; what it breaks down to is not worked out here.
0.326–0.338 of the [source]: 3.7 mg ion/kg body weight/day = 259 mg/day at 70 kg (SCF 1997, reconfirmed JECFA 2002, retained EFSA 2017).
Legal maximum in the food
EU Reg 2023/915: iceberg-type lettuce max 2,000 mg/kg grown outdoors, 2,500 mg/kg under cover [source]
Effect
EFSA: vegetable exposure unlikely to cause appreciable health risk. Regulatory assessment
Sesquiterpene lactones (lactucin, lactucopicrin)
Dose
raw: not in totals: no amount in the source data; explainer only
Threshold
No established threshold
Effect
The bitter taste. Isolated compounds were sedative/analgesic in mice at 15–30 mg/kg. Animal study
Used in / studied for
'Lettuce opium' (mainly wild lettuce) was a traditional sedative; little clinical evidence. A 2-week trial of lettuce SEED capsules (1,000 mg/day) improved sleep scores in pregnant women.Traditional use (not evidence)[source]
0 entries for this food are hidden pending verification. They are never shown with a value until checked.
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.
