Straight from the tree, an olive is too bitter to eat. It holds oleuropein, a bitter compound, and every table olive has been cured to get rid of it. Curing takes a few days with lye or a few months with brine or salt. The same fruit ends up green, brown or black depending on when it is picked and how it is cured, and the black olives in cans are picked green and darkened by air bubbled through the lye.
Botanically an olive is a drupe, a fruit with one stone, like a cherry or a peach. It is fatty for a fruit: canned ripe olives have 10.9 g of fat per 100 g, about 80% of their calories, and most of it is monounsaturated. They also have 6.28 mg of iron per 100 g, 35% of the daily value, and on this site olives rank third of 34 foods for the flavonoid luteolin. The catch is salt: 735 mg of sodium per 100 g, 32% of the daily value.
Olive oil gets most of the research, and its results do not automatically apply to the whole fruit. A 2020 review found few laboratory, animal or human studies of table olives. The cards below put table olive studies first, and the two olive oil cards are labeled plainly.
Health benefits of olives
The top findings from 11 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 →- ★★★Olive oil polyphenols protect blood fats (EU claim)In 2012 the EU authorized a health claim that polyphenols in olive oil protect blood fats from oxidative stress. The claim is for olive oil, not table olives.
- ★★Fewer heart events on an olive-oil Mediterranean dietIn 7,447 adults in Spain at high heart risk, a Mediterranean diet with extra-virgin olive oil lowered major heart events (hazard ratio 0.69). The comparison was a low-fat diet, and this is olive oil in a whole diet, not table olives.
- ★★Modestly lower cholesterol and triglycerides, from supplementsAcross 14 trials in 594 people, supplements of olive compounds (oleuropein, hydroxytyrosol or tyrosol) modestly lowered total cholesterol, triglycerides and insulin. These were not whole olives, and the authors say more studies are needed.
- ★Lower oxidative stress and inflammation markersIn 25 healthy adults, 12 green olives a day for 30 days lowered a marker of oxidative stress and interleukin-6, an inflammation marker. There was no comparison group, so the results are preliminary.
- ★Little effect on blood sugar after breadIn seven short trials in healthy volunteers, oleuropein, the bitter olive compound, did not change blood sugar after bread. In solution it cut the rise after a smaller sucrose dose, but not after a larger sucrose or glucose dose.
All 11 studies, strongest evidence first
Olive oil polyphenols earned an EU health claim for protecting blood lipids from oxidative stress
This is olive oil, not table olives. The European Food Safety Authority reviewed the evidence in 2011, and the EU authorized the claim in 2012 for olive oil with at least 5 mg of hydroxytyrosol and its derivatives per 20 g, eaten as 20 g a day. The claim does not cover table olives.
Olive compounds taken as supplements modestly lowered total cholesterol, triglycerides and insulin
Meta-analysis of 14 human trials with 594 people, testing oleuropein, hydroxytyrosol or tyrosol, the main olive phenols, not whole olives. The effects were small and the trials varied a lot, and the authors say more studies are needed.
A Mediterranean diet with extra-virgin olive oil lowered major heart events (hazard ratio 0.69) against a low-fat diet
This is olive oil inside a whole diet, not table olives. Randomized trial of 7,447 adults in Spain at high heart risk, followed for a median of 4.8 years. The first report was withdrawn over randomization problems and re-analyzed; results were similar after leaving out 1,588 people.
12 green olives a day for 30 days lowered a marker of oxidative stress and interleukin-6
Small pilot study of 25 healthy adults who ate 12 Nocellara del Belice green olives a day, measured before and after. The abstract describes no comparison group. Fat mass fell and muscle mass rose, gut Lactobacilli did not change significantly, and the authors call the results preliminary.
Oleuropein, even as found in olives, did not change blood sugar after bread in healthy volunteers
Seven crossover trials in healthy volunteers tested oleuropein, the bitter olive compound, mostly prepared from olive leaves, in capsules, in solution or as it occurs in olives. In solution it cut the blood sugar rise after 25 g of sucrose, but not after 50 g of sucrose or glucose. One author is an employee of the company BioActor.
An olive fruit extract with hydroxytyrosol did not beat placebo for arterial stiffness in 11 days
Double-blind trial of 36 people at risk of arterial stiffness, 12 per group, taking 250 or 500 mg of the extract or placebo. All three groups, placebo included, improved on the stiffness score, and the authors report a 21.64% triglyceride drop in the higher-dose group. The company that makes the extract funded the study and employs the authors.
An olive fruit extract with 50 mg of maslinic acid eased mild knee pain slightly more than placebo and the group lost weight
Randomized, double-blind trial of 20 middle-aged and elderly volunteers with mild knee joint pain; both groups improved, and weight and body mass index fell in the maslinic acid group after 12 weeks. It was small and preliminary, and it was not registered in a public database.
Table olives lowered blood pressure by about 15 mmHg in hypertensive rats but not in normal rats
Arbequina olives were given by gavage at 3.85 g per kg, as a single dose or daily for 7 weeks. The drop appeared in the second week and held, and body weight did not change. Only a few olive compounds reached the blood, including maslinic acid, oleanolic acid, hydroxytyrosol and luteolin.
Table olives lowered blood pressure by about 19 mmHg in hypertensive rats and changed their gut bacteria
Rats ate Arbequina olives at 3.85 g per kg for 7 weeks. Malondialdehyde and angiotensin II fell, and gut bacteria shifted toward more Lactobacillus and Bifidobacterium. Rat results often do not carry over to people.
Table olives cut early colon lesions by 54.1% in rats given a carcinogen
Rats got Arbequina olives by gavage for 49 days. Early precancer markers called aberrant crypt foci fell 54.1% and mucin-depleted foci fell 35.7%, and maslinic and oleanolic acids were the main olive compounds found in the colon. These are early markers in rats, not cancer in people.
Hydroxytyrosol from table olives stayed in rat blood for up to 8 hours
Rats got destoned Arbequina olives by gavage at 3.85 or 7.70 g per kg. Hydroxytyrosol had a half-life of about 2.5 hours and was cleared mostly as a sulfate. The authors say olives give a steadier blood profile than other hydroxytyrosol foods, but this shows absorption, not a benefit.
Who should be careful with olives
Most people can eat olives freely. Take a little care if one of these applies:
- High blood pressure or a sodium limit. USDA values for canned ripe olives are 162 mg of sodium in 5 large olives (22 g), 7% of the daily value, and 735 mg per 100 g, 32%. The WHO advises adults to keep sodium under 2,000 mg a day, so a big handful counts.
- Home-cured olives. Olives are a low-acid food, so University of California food preservers say home-canned olives must be pressure canned with a tested processing time, because of botulism. To prevent softening they suggest a storage brine with at least 10% salt, pressure canning or the refrigerator.
How to choose, store and eat olives
- Green, Spanish style: soaked in 2 to 4% lye for 8 to 10 hours, then fermented in an 8 to 12% salt brine for about three months. About 60% of the world’s table olives are made this way.
- Black ripe, California style: picked green, cured in lye with air bubbled through to turn them black, then canned in a mild brine. This is the type the USDA values on this page describe.
- Naturally black, Greek style: ripe olives cured in brine with no lye, or packed in salt for a month or longer until they shrivel. Oil-cured olives are dry-cured ones softened in olive oil for several months.
Check the sodium on the label, because brine strength varies: the Codex standard sets a minimum of 5% salt for treated olives, 6% for natural olives and 8% for dried olives. Acrylamide, a compound that forms when food is heated, turned up in black olives: FDA’s Total Diet Study found 123 to 424 parts per billion in fiscal years 2003 to 2006, and a 2023 study of black table olives found 208 to 773 micrograms per kilogram. Those are measured levels, not a verdict on harm, and no study here tested what they mean at the amounts people eat.
Sources
- Salt reduction. World Health Organization fact sheet.
- Olives, ripe, canned (small-extra large). USDA FoodData Central, FDC ID 169094.
- Curing, preserving and eating olives. UCCE Master Food Preservers of Amador and Calaveras Counties, University of California Agriculture and Natural Resources. 2019.
- Mermelstein NH. Putting olives on the table. Food Technology, Institute of Food Technologists. 2017.
- Survey data on acrylamide in food: Total Diet Study results. US Food and Drug Administration.
- Hölzle E, Becker L, Oellig C, Granvogl M. Heat-introduced formation of acrylamide in table olives: analysis of acrylamide, free asparagine, and 3-aminopropionamide. J Agric Food Chem. 2023.
History of olives
The olive tree is old. Studies of wild olives, called oleasters, point to three long-lived refuges around the Mediterranean: the Near East including Cyprus, the Aegean, and the Strait of Gibraltar. Plastid DNA work places the first domestication in the northern Levant, followed by spread across the Mediterranean along with the expansion of early civilizations.
A review of Middle Eastern evidence argues that the heartland of domestication is wider than the Jordan Valley and takes in the Levant. It calls domestication a long and ongoing process linked to the early production of oil and to olive trade. Later genetic work on cultivated olives found three gene pools, roughly western, central and eastern, and signs that crosses with wild olives shaped the crop and perhaps allowed local domestications.
The fruit itself needed a trick to become food. Raw olives are very bitter and astringent, so people learned to cure them, which removes much of the oleuropein. The Spanish-style green olive is still the world’s most common table olive, at about 60% of the total according to a 2017 industry magazine.
Olives reached California with the Franciscan mission of San Diego de Alcalá, and pioneers later grew new trees from mission cuttings, which gave the Mission variety its name. In 1892 Freda Ehmann moved to California after her husband’s death and kept a grove near Oroville. She worked with a University of California food scientist on a pickling method that could be sold, and is credited with launching the state’s olive industry. California now grows more than 95% of US olives, and more than 90% of its crop becomes black ripe olives.
Olive trees reached Japan in 1908 on Shodo Island, which produces over 95% of Japan’s olives. Worldwide, roughly 10 million metric tons of olives are produced a year, and about 90% of them go to olive oil, according to the same 2017 article, so a table olive is a minority product of a crop grown mostly for oil.
Sources
- Besnard G, Khadari B, Navascués M, et al. The complex history of the olive tree: from Late Quaternary diversification of Mediterranean lineages to primary domestication in the northern Levant. Proc Biol Sci. 2013.
- Kaniewski D, Van Campo E, Boiy T, et al. Primary domestication and early uses of the emblematic olive tree: palaeobotanical, historical and molecular evidence from the Middle East. Biol Rev Camb Philos Soc. 2012.
- Diez CM, Trujillo I, Martinez-Urdiroz N, et al. Olive domestication and diversification in the Mediterranean Basin. New Phytol. 2015.
- Olive. Wikipedia.
- Mission olive. Wikipedia.
- Freda Ehmann. Wikipedia.
- Mermelstein NH. Putting olives on the table. Food Technology, Institute of Food Technologists. 2017.
- Rocha J, Borges N, Pinho O. Table olives and health: a review. J Nutr Sci. 2020.
Frequently asked questions about olives
Are olives good for you?
In small amounts, yes, with salt as the catch. Canned ripe olives have 116 kcal, 10.9 g of fat, mostly monounsaturated, and 1.6 g of fiber per 100 g, plus 6.28 mg of iron, 35% of the daily value. The evidence for eating olives is thin: a pilot of 25 adults saw lower markers of oxidative stress and inflammation, and a trial of oleuropein found no effect on blood sugar after bread. The strong evidence here belongs to olive oil.
Can you eat olives straight from the tree?
No. Raw olives are very bitter because of oleuropein, and curing in lye, brine, salt or water removes it. Curing takes a few days with lye or a few months with brine or salt, so every table olive you buy has already been through it.
Are olives high in sodium?
Yes, because curing uses salt. Five large canned ripe olives (22 g) have 162 mg of sodium, 7% of the daily value, and 100 g has 735 mg, 32%. Brine strength differs by type and brand, so check the label.
How many olives can you eat a day?
No study here sets an amount. The one pilot trial used 12 green olives a day for 30 days in healthy adults. If 12 olives were canned ripe ones, they would give about 390 mg of sodium and 62 kcal, so the salt is what limits a handful, especially with high blood pressure.
Are olives a fruit?
Yes. An olive is a drupe, a fruit with a single stone, like a cherry or a peach. It is not sweet, though: canned ripe olives list 0 g of sugar in the USDA data, and 80% of their calories come from fat.
Are green or black olives healthier?
No study here compares them. They are the same fruit, picked at different ripeness or cured in different ways, and California black olives are picked green and darkened with air in lye. The numbers on this page are USDA values for canned ripe olives, so check labels for other types, and note that black olives carry measured acrylamide.
Are olives or olive oil healthier?
Olive oil has the stronger evidence. The EU approved a health claim for olive oil polyphenols, and a Mediterranean diet with extra-virgin olive oil went with fewer major heart events (hazard ratio 0.69) in a trial of 7,447 adults. For table olives we found only small trials and rat studies, and olives add fiber but also salt.
Do olives lower blood pressure?
Not shown in people. In hypertensive rats, Arbequina table olives lowered blood pressure by about 15 mmHg in one study and 19 mmHg in another, but no human trial here tested it. Olives are also salty, and the WHO links excess sodium to higher blood pressure.