Cucumber is about 95% water, so a cup of slices (104 g) holds 99 g of water and only 16 calories. In the kitchen it is a vegetable, but botanically it is a berry of the type called a pepo, and a cousin of melon and squash.
Cucumber plants make bitter compounds called cucurbitacins, with cucurbitacin C the main one. In 2014, researchers found nine cucumber genes that build it, plus a switch gene called Bt that turns the pathway on in the fruit, and signs that farmers selected against Bt as they bred nonbitter cucumbers. In a 2023 study of 69 inbred lines, only six had any cucurbitacin C that could be detected in the fruit. Bitterness still matters in the squash family: French poison centers logged 353 cases from bitter, non-edible squash in five years, mostly vomiting and diarrhea, with no deaths.
Cucumber has been studied far less as a food than as a source of extracts. The human trials below used concentrated extracts or powders, and in lab tests cucumber ranked last among common vegetables for antioxidant measures. The peel makes a clear difference in the USDA data: 16.4 µg of vitamin K per 100 g with the peel, and 7.2 µg peeled.
Health benefits of cucumbers
The top findings from 16 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 →- ★Less knee osteoarthritis pain, from an extractA concentrated cucumber extract (not slices) eased knee osteoarthritis pain over 180 days, more so at the higher dose than placebo. In another trial with no placebo, scores fell 70% against 33% with glucosamine-chondroitin.
- ★Lower LDL cholesterol and triglycerides, from seed extractIn 47 people with mild hyperlipidemia (high blood fats), cucumber seed extract capsules for 6 weeks lowered both compared with placebo. This was seed extract, not the flesh you eat.
- ★No clear difference in mood, sleep or anxietyIn 80 adults, a cucumber powder for 60 days improved scores in both groups. The difference between the groups over time was not statistically significant.
- Population studyVegetables linked to better hydration in childrenIn German children, 100 g more solid fruit and vegetables a day went with a 46 mL larger free water reserve (a urine hydration marker). Polish schoolchildren who ate vegetables more often had lower odds of dehydration, and neither study looked at cucumber alone.
All 16 studies, strongest evidence first
A cucumber extract taken for 180 days cut knee osteoarthritis scores by 70%, against 33% with glucosamine-chondroitin
Randomized trial in 122 people aged 40 to 75 with moderate knee osteoarthritis, comparing 10 mg of a water extract of cucumber (Q-Actin) twice a day with glucosamine-chondroitin. There was no placebo group, and the study was sponsored by IminoTech, which supplied the extract. This was a concentrated extract, not cucumber slices.
A standardized cucumber extract for 180 days eased knee osteoarthritis pain in a dose-dependent way compared with placebo
Placebo-controlled trial in 101 people with knee osteoarthritis (91 finished), using 20 mg or 100 mg a day of an extract standardized to over 1% of an iminosugar called ido-BR1. The abstract gives no percentages, and two authors are affiliated with the company PhytoQuest. It tested an extract, not the vegetable.
A cucumber powder for 60 days improved mood, sleep and anxiety scores, but the difference between groups over time was not statistically significant
Placebo-controlled trial in 80 adults (average age 50) taking 20 mg a day of a standardized Cucumis sativus powder (Q-Actin) or a rice-protein placebo. Scores improved in both groups, and the cucumber group improved more on fatigue, mood, sleep, stress and anxiety, but the authors urge caution and call for larger trials. No adverse effects were reported.
Cucumber seed extract capsules for 6 weeks lowered LDL cholesterol and triglycerides compared with placebo in people with mild hyperlipidemia
Double-blind trial in which 47 people finished (24 took 500 mg a day of seed extract, 23 took placebo). Total cholesterol and BMI also fell and HDL rose compared with placebo; the abstract reports p-values, not amounts. A small trial of seeds, not the flesh you eat.
In children, 100 g more solid fruit and vegetables a day went with a 46 mL larger free water reserve, a urine marker of good hydration
Cohort of 442 German children aged 4 to 10 with 1,286 three-day weighed food records and 24-hour urine samples. It covers fruit and vegetables as a group, not cucumber alone. A negative reserve, a sign of risk of low hydration, was seen in 22% of the children, and solid fruit and vegetables supplied 12% of their total water intake.
Food moisture supplied 27% of total water intake in the UK and 36% in France
Analysis of two national diet surveys, one in the UK and one in France. It covers all foods, not cucumber alone. People who drank less did not make up for it with more water-rich foods, and 80 to 90% of the differences in total water intake came from fluids. Several authors work for Danone Research.
Schoolchildren who ate vegetables more often had lower odds of being dehydrated
Cross-sectional study of 2,849 Polish children aged 10 to 12. Hydration was estimated from total body water by impedance, and diet by a food frequency questionnaire. Vegetables are one group here, juice and more physical activity also went with lower odds, and a snapshot cannot show cause.
Of 27 common vegetables, cucumber had the lowest cellular antioxidant activity
Laboratory study using a cell-culture assay on 27 vegetables commonly eaten in the US, alongside phenolic content and ORAC values. Beets, broccoli and red pepper scored highest. These are cell-based scores, not proof of a health effect in people.
Among 10 common vegetables, cucumber ranked last for both total phenolics and total antioxidant activity
Laboratory analysis of the 10 vegetables most eaten per person in the US. Broccoli had the most phenolics and red pepper the highest antioxidant activity. Spinach was strongest against liver cancer cells in a dish, and cucumber was not among the top five.
Tests of three Korean cucumber types found the highest antioxidant activity in the peel of the Chuichung cultivar and the flesh of the Mini cultivar
Laboratory study of three cultivars (Chuichung, White Dadagi and Mini), measuring peel and flesh separately. Apigenin and quercetin derivatives, chlorophylls, lutein and alpha- and beta-carotene tracked with antioxidant activity. It shows that both parts carry these compounds and that cultivar matters; it did not test any effect in people.
In mice given a diabetes-causing chemical, cucumber peel extract nearly reversed most of the changes in blood sugar and blood fats
Study in mice, not people. Ethanol extracts of cucumber, squash and round gourd peels were tested at 250 and 500 mg per kg a day, and squash peel worked best. An extract is not the same as eating the peel.
When cucumbers were peeled, more than 95% of the Salmonella on the surface stayed on the peel
Laboratory experiment with cucumbers dipped in Salmonella Newport and then half-peeled by hand. Transfer to the edible flesh ranged from 0 to 0.6% and to the peeler from 0 to 2.2%. Peeling removes most surface germs, but a few can still move to the flesh or the tool.
A cucumber fruit extract cut the release of the inflammatory signals IL-8 and GM-CSF in blood vessel cells
Cell study on pig aortic endothelial cells exposed to a bacterial toxin (LPS) and a water-ethanol extract of cucumber fruit at up to 2 mg/mL. IL-6 and IL-1 alpha fell later, and the anti-inflammatory IL-10 rose. Cells in a dish, not people.
In diabetic rats, methanol extracts of cucumber and pumpkin lowered blood sugar to values similar to non-diabetic rats
Rat study. Diabetes was triggered with streptozotocin, and the rats then received extracts at 200 or 400 mg per kg for 21 days, with metformin as a comparison. Liver enzymes, blood fats and tissue damage also improved. This was an extract dose, not a food portion.
Cucurbitacin C, the bitter compound of cucumber, slowed the growth of human cancer cells and of tumors in mice
Cell and mouse study using purified cucurbitacin C, with mice that carried transplanted human tumors treated at 0.1 mg per kg. Low doses halted the cell cycle and high doses caused cell death. It is the bitter, irritating compound that breeding has largely removed from cucumbers, so it says little about eating them. A correction was published in 2024.
Compounds from bitter cucumber leaves slowed the growth of four human cancer cell lines
Laboratory study that isolated ten cucurbitacin C relatives, seven of them new, from the bitter leaves, not the fruit. Six compounds slowed liver, lung, prostate or colon cancer cells, and the two strongest on liver cells were still less potent than the drug taxol. Cells in a dish, not people.
Who should be careful with cucumbers
Most people can eat cucumbers freely. Take a little care if one of these applies:
- Warfarin. Cucumber has some vitamin K, 16.4 µg per 100 g with the peel and 7.2 µg without, a modest amount that can still 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.
- Ragweed or grass pollen allergy. A review notes that people with ragweed allergy can get an itchy mouth and throat from melon, cucumber, banana and zucchini, usually with the raw food. About 1 to 2% of people with this pollen-related food allergy have severe reactions.
- Salmonella on the skin. Whole cucumbers caused a 2024 US outbreak of 551 cases in 34 states. Rinse them under running water before cutting or peeling, and take extra care with children under 5, adults 65 and older, and people with weakened immune systems.
How to choose, store and eat cucumbers
- With the peel: USDA data list 16.4 µg of vitamin K and 45 µg of beta-carotene per 100 g with the peel, against 7.2 and 31 µg peeled. In a lab test, peeling left more than 95% of the Salmonella on the peel.
- Raw: a cup of slices (104 g) has 99 g of water and 16 calories. If you have irritable bowel syndrome, Monash University lists 75 g as one low FODMAP serve.
- Pickled: dill pickles hold 809 mg of sodium per 100 g, against 2 mg in fresh cucumber, so the brine is what to watch.
Choose firm, dark green cucumbers with no soft spots or bulge in the middle, and keep them unwashed in a plastic bag in the fridge for up to a week. If a cucumber tastes strongly bitter, spit it out and throw it away. Residues are no reason to skip cucumbers: in USDA tests of 708 samples in 2024, only 5 had a residue above the legal limit.
Sources
- Dietary advice for patients taking warfarin. Cambridge University Hospitals NHS Foundation Trust.
- Anticoagulant medicines: considerations. NHS.
- Cucumber, with peel, raw. USDA FoodData Central (SR Legacy).
- Cucumber, peeled, raw. USDA FoodData Central (SR Legacy).
- Pickles, cucumber, dill or kosher dill. USDA FoodData Central (SR Legacy).
- Muluk NB, Cingi C. Oral allergy syndrome. Am J Rhinol Allergy. 2018.
- Salmonella outbreak linked to cucumbers, June 2024. CDC. 2024.
- Laughlin M, Bottichio L, Weiss J, et al. Multistate outbreak of Salmonella Poona infections associated with imported cucumbers, 2015-2016. Epidemiol Infect. 2019.
- Jung J, Schaffner DW. Enterobacter aerogenes B199A may be an effective surrogate for quantifying transfer of Salmonella Newport 96E01152C-TX from cucumber peel to edible flesh and peeler during peeling. J Food Prot. 2022.
- Low FODMAP shopping list. Monash FODMAP blog.
- Cucumbers. University of Nebraska–Lincoln Extension.
- Le Roux G, Leborgne I, Labadie M, et al. Poisoning by non-edible squash: retrospective series of 353 patients from French Poison Control Centers. Clin Toxicol (Phila). 2018.
- Pesticide Data Program annual summary, calendar year 2024. USDA Agricultural Marketing Service.
History of cucumbers
Cucumbers come from Asia. DNA work on about 100 Cucumis samples found that cucumber and melon are both of Asian origin, with wild cucumbers in India and the Southeast Asian species Cucumis hystrix as the closest relative of the cultivated plant. Surprisingly, melon’s closest relative lives in Australia.
People have grown cucumbers for at least 3,000 years. They were domesticated in India from a wild form called Cucumis sativus var. hardwickii, and East Asian types split from Indian ones about 2,500 years ago, according to genetic modeling. A genome study of 115 cucumber lines found that fruit crops went through narrower bottlenecks than grain crops, and flagged a gene region tied to the loss of bitterness.
The Romans loved them. Pliny the Elder wrote that Emperor Tiberius had cucumbers on his table every day, summer and winter, grown on raised beds on wheels that were rolled into the sun and sheltered under frames glazed with a transparent stone. Wikipedia notes that his cucumber was probably small, like a gherkin, a word that comes from the early modern Dutch for a small pickled cucumber.
Cucumbers crossed the Atlantic with the Spanish, who brought them to Haiti in 1494. When Jacques Cartier reached the site of today’s Montreal in 1535, he found large cucumbers already growing there. China now grows about 78% of the world’s 88 million tonnes.
Not everyone approved. In 1663 Samuel Pepys recorded hearing that a man had died from eating cucumbers, John Evelyn wrote in 1699 that the cucumber was thought fit to be thrown away, and Samuel Johnson reported that English physicians said to slice one, dress it with pepper and vinegar, and then throw it out.
Sources
- Sebastian P, Schaefer H, Telford IR, Renner SS. Cucumber (Cucumis sativus) and melon (C. melo) have numerous wild relatives in Asia and Australia, and the sister species of melon is from Australia. Proc Natl Acad Sci U S A. 2010.
- Qi J, Liu X, Shen D, et al. A genomic variation map provides insights into the genetic basis of cucumber domestication and diversity. Nat Genet. 2013.
- Shang Y, Ma Y, Zhou Y, et al. Biosynthesis, regulation, and domestication of bitterness in cucumber. Science. 2014.
- Min K, Song K, Lim S, Yi G, Lee EJ. Cucurbitacin and volatile compound profiling reveals independent domestication of cucumber (Cucumis sativus L.) fruit. Food Chem. 2023.
- Cucumber. Wikipedia.
Frequently asked questions about cucumbers
Is cucumber good for you?
It is a light, watery food, but the proof of benefits is thin. Raw cucumber with peel has 15 calories, 95.2 g of water, 0.5 g of fiber, 147 mg of potassium and 16.4 µg of vitamin K (14% of the Daily Value) per 100 g. No study here tested whole cucumber on health outcomes, and the trials of cucumber extracts are small.
Is a cucumber a fruit or a vegetable?
Both, depending on who asks. Botanically it is a fruit, a berry of the type called a pepo, because it grows from a flower and holds seeds. In the kitchen and on nutrition tables it counts as a vegetable.
Should you peel cucumbers?
You do not need to. USDA data list 16.4 µg of vitamin K and 45 µg of beta-carotene per 100 g with the peel, against 7.2 and 31 µg peeled. If you do peel, rinse first: in a lab test, more than 95% of the Salmonella stayed on the peel, but a few moved to the flesh or the peeler.
Why is my cucumber bitter, and is it safe?
The bitterness comes from cucurbitacins, mainly cucurbitacin C, which breeding has largely removed: only six of 69 cucumber lines in one study had any detectable in the fruit. If a cucumber tastes strongly bitter, spit it out and throw it away. Poisoning is documented from bitter squash, where 58% of 353 patients in France had diarrhea, vomiting or stomach pain and none died, and we found no comparable series for cucumbers.
Do cucumbers hydrate you?
They add water, but no trial here compared cucumber with drinking. A cup of slices (104 g) holds 99 g of water. Food as a whole supplied 27% of water intake in the UK and 36% in France, and in 442 children each extra 100 g of fruit and vegetables went with 46 mL more spare body water. These are links, not proof.
How many calories and carbs are in a cucumber?
Raw cucumber with peel has 15 calories per 100 g, or 16 in a cup of slices (104 g). Per 100 g it has 3.1 g of net carbs, 1.67 g of sugars, 0.5 g of fiber, 0.65 g of protein and 0.11 g of fat. It fills a plate cheaply, but no trial here tested cucumber for weight loss.
Is cucumber good for people with diabetes?
It fits easily, but no human trial here tested cucumber on blood sugar. It has about 3.1 g of net carbs per 100 g. Extracts lowered blood sugar in rats given a diabetes-causing drug, which is a long way from eating slices. Check portions and medicines with your care team.
Does cucumber cause gas?
No trial here measured gas. Monash University lists cucumber as low FODMAP at a 75 g serve, about half a cup, so a small serving is usually fine for irritable bowel syndrome. If cucumber bothers you, try a smaller portion.