Kumquats are an oddball among citrus fruits. In addition to their small size, their peel is edible and actually much sweeter than the pulp. They’re filled with vitamins, minerals, antioxidants, and anti-inflammatory compounds that offer a range of potential benefits. Find out how to add them to your diet or use their essential oil.
What Is a Kumquat?
Kumquats are a group of citrus trees that produce small, round or oval-shaped fruits. Their name comes from the Cantonese word ‘kamkwat’ (金橘), which means “golden orange/tangerine”. Since the peel is thin and sweeter than the pulp, kumquats are usually eaten whole as opposed to other citrus fruits [1+].
Kumquats are native to China, from where they were introduced to Japan, Taiwan, and Southeast Asia centuries ago. Today, kumquats are also cultivated in warm regions of Europe, the US (especially California and Florida), South America, Australia, South Africa, and India. They are grown for their fruits or as decorative trees [2+, 3+].
These peculiar fruits were once classified under their own genus (Fortunella). They have since been merged into the same genus as oranges, lemons, mandarins, and grapefruits (Citrus) within the Rutaceae family. There are four main cultivated kumquat species [4+, 5+, 6+]:
- ‘Nagami’ or ‘oval kumquat’ (Citrus margarita)
- ‘Marumi’ or ‘round kumquat’ (Citrus japonica)
- ‘Meiwa’ or ‘large round kumquat’ (Citrus crassifolia)
- ‘Mame’ or ‘Hong Kong kumquat’ (Citrus hindsii)
Of these, only oval kumquat is normally grown in Western countries.
Kumquats are typically eaten raw, pickled or candied, and used to make marmalades, liquors, and sauces. In traditional herbal medicine, they are used for sore throat, coughing, inflammation, and protecting the blood vessels. Most of these traditional uses remain, however, scientifically unproven [7+, 8+, 2+, 9].
Fruit Taste & Size
Kumquats have a typical citrus flavor. The peel is sweet, fleshy, and very aromatic due to the presence of essential oils and flavonoids. In turn, the pulp is juicy and very sour [10+, 11+, 12+].
Kumquats are among the smallest citrus fruits (together with calamondins). They range from the approximate size of a pea (C. hindsii) to 1.5 inches broad (C. crassifolia). The species usually grown in Western countries (C. margarita) is the most oval-shaped one, with an average weight of 15-20 g and the size of a large olive [13+].
Loquat vs Kumquat
Because both names contain the Cantonese syllable ‘quat’ (meaning ‘orange’ or ‘tangerine’) and the fruits even look somewhat alike, some people confuse kumquats and loquats. However, these species are quite different and don’t even belong to the same families.
Loquat (Eriobotrya japonica), also known as Japanese medlar, is a bigger tree with characteristic large leaves (belonging to the Rosaceae family). It produces orange-golden, pear-shaped fruits with thin skin (that is usually not eaten) and sweet, slightly acidic flesh [14+].
Snapshot of Kumquat
Proponents
- Easy to eat (bite-sized and eaten with the peel)
- You can eat it raw or add to many recipes
- Good source of fiber, vitamins, and minerals
- Antioxidant and anti-inflammatory
- May help lower blood fat and sugar levels
- May help lose weight
- May reduce digestive issues
- May improve bone health
Skeptics
- Most benefits are insufficiently investigated
- Some people might find the pulp overly sour
Benefits of Kumquat Fruits
Effective for:
1) Nutritional Boost
A 100-g serving of kumquats (5-6 fruits) supplies [15+]:
- Calories: 71
- Water: 81 g
- Carbs: 15.9 g (9.4 g sugars and 6.5 g fiber)
- Proteins: 1.88 g
- Fats: 0.86 g
- Provitamin A: 290 IU (10% of recommended vitamin A daily intake)
- Vitamin C: 43.9 mg (73% of recommended daily intake)
- Calcium: 62 mg (6% of recommended daily intake)
- Magnesium: 20 mg (7% of recommended daily intake)
This means that kumquats are a good source of nutrients, especially carbohydrates, vitamins, and minerals. Their high water and fiber content, combined with their low calorie count, makes them a perfect filling snack for people watching their weight.
2) Packed with Antioxidants
Kumquats contain several unique antioxidant flavonoids (such as DGPP, margaritene, isomargaritene, fortunellin, and poncirin). Flavonoids are more abundant in the peel than in the pulp, and in green than in ripe fruits. Kumquat extracts can break down free radicals in test tubes and their antioxidant activity increases with the flavonoid content [7, 16, 2, 17].
Vitamin C is another powerful antioxidant found in relatively high amounts in kumquats (approximately 12 mg/fruit) [15+, 18, 19].
3) Lowering Cholesterol
In obese mice fed high-fat diets, kumquat extract lowered blood fat and cholesterol levels. The extract probably works by turning on PPAR-a, a protein that revs up metabolism and fat-burning [20].
Free radical-damaged LDL triggers an inflammatory response that causes cholesterol to build up inside the arteries. Citrus fruits might prevent this by releasing antioxidant compounds such as vitamin C and flavonoids. An advantage of kumquat over other citrus fruits is that the edible peel provides additional flavonoids [21+, 22+, 20].
The cholesterol-lowering effect of kumquat has not been tested in humans. But eating other citrus fruits or drinking their juice reduced blood cholesterol levels (both free and bound to LDL) in 9 trials on over 500 people. Kumquat might have similar effects [23, 24, 25, 26, 27, 28, 29, 30, 31].
Kumquats also contain phytosterols (amyrin, lupenone, and sitosterol). Being chemically similar to cholesterol, phytosterols interfere with its uptake in the gut. In animals fed high-sugar and -fat diets, phytosterols reduced blood cholesterol levels [32, 33, 34, 35, 36].
What’s more, soluble fibers – such as those in kumquat – can absorb water and form a thick paste that prevents cholesterol uptake in the gut. Citrus fibers reduced blood cholesterol levels in 2 clinical trials on almost 100 people and 2 animal studies [33, 37, 38, 39, 40].
Possibly Effective for:
4) Promoting Bone Health
Kumquats are a source of calcium, a mineral that is essential to bone formation and health [41].
Citrus juice and pulp reduced bone loss in rats with osteoporosis, possibly by providing flavonoids. Indeed, the flavonoid poncirin promoted the formation of the cells that build and repair bones (osteoblasts) in cell-based studies, while preventing mineral loss in mice with osteoporosis [42, 43, 44, 45].
Beta-cryptoxanthin is the carotenoid found in kumquats. The body can use it to build antioxidant defense and make vitamin A [1, 46].
Juice enriched with beta-cryptoxanthin increased bone formation and reduced its breakdown in 3 clinical trials on over 130 people. In cell-based studies, it stimulated the activity of bone-building cells, while blocking bone-degrading cells (osteoclasts) [47, 48, 49, 50, 51, 52, 53].
Although the results are promising, the evidence to claim that kumquats improve bone health is still limited. More clinical trials are needed.
5) Helping Burn Fat and Lose Weight
In normal and obese mice fed a high-fat diet, kumquat extract reduced weight gain, fat cell size, and blood fat levels [20].
In test tubes, complex sugars isolated from kumquat blocked the pancreatic enzyme that helps digest fats in the gut. This suggests that eating this fruit might help you absorb only a part of the fat you eat. Additionally, kumquats’ flavonoid poncirin prevented fat cells from maturing [54, 44].
Kumquat’s high fiber content may also reduce food intake by increasing satiety, as seen in a clinical trial on 30 people who added orange fiber to their diets [55].
Additionally, kumquat increases PPAR-a, which boosts fat-burning [20].
Being a nutritious, hydrating, low-calorie fruit, kumquats seem like a good addition to weight-loss and fat-loss plans. However, the evidence is still limited and further research in humans is needed.
6) Lowering Blood Sugar
Kumquat extract reduced blood sugar levels and insulin resistance in diabetic and obese mice [56, 20].
Plus, soluble fiber reduces blood sugar uptake in the gut. In a clinical trial on 34 overweight men, orange fiber (2.55 or 5.48 g 1x/day) reduced blood sugar and insulin spikes after meals rich in sugar and fats. Kumquats likely offer similar benefits [57].
However, a small clinical trial and two animal studies cannot be considered strong evidence that eating kumquats helps lower blood sugar. Additional studies in humans are needed before we can make definitive claims on this benefit.
7) Cancer Prevention
Two meta-analyses of 19 studies associated high citrus intake with a reduced risk of stomach cancer. This effect was possibly due to poncirin, which is also found in kumquats. Poncirin reduced the growth and increased the death of stomach cancer cells in test tubes [58, 59, 60, 61].
Another kumquat component, the carotenoid beta-cryptoxanthin, was associated with a slightly decreased frequency of lung cancer in an observational study on over 400k people [62].
A study on almost 500 people associated eating citrus peel (but not their pulp or juice) with a reduced frequency of a skin cancer type. Because kumquats have a thinner and sweeter peel than any other citrus fruits, it may be easier to reap this benefit by eating them [63].
Although promising, the evidence to suggest kumquats as an effective aid in cancer prevention is still limited. It’s important to note that the fact that eating kumquats (or other citrus fruits) was associated with lower cancer frequency in the studies doesn’t necessarily mean that it was the cause of this reduced frequency. Many different genetic and environmental factors could have influenced the risk of cancer.
Animal and Cell Studies (Lack of Evidence):
Helping with Digestion
Complex sugars from kumquat extract triggered a shift toward a beneficial gut microbe–one that improves carb digestion and prevents gut infections (increasing Bifidobacterium adolescentis) – in test tubes. Hence, kumquats might act as good prebiotics [64].
And, as mentioned above, kumquat’s flavonoids fortunellin and poncirin improved inflammatory digestive issues in mice [65, 66, 67, 68].
The high fiber content of kumquats suggests these fruits may be used as an add-on to medical therapies for digestive issues such as constipation, IBS, GERD, and ulcers [69+, 70].
However, the evidence is mostly based on animal and cell-based studies whose results may not be the same in humans. Additionally, everyone reacts differently, so be sure to discuss it with your doctor and first try them out in moderation if you have gut issues or food sensitivities.
Anti-Inflammatory
The main anti-inflammatory compounds of kumquat are its flavonoids. Kumquats contain only traces of common citrus flavonoids (like naringenin and hesperidin) but much higher levels of unique ones that are barely found in other species [4+].
The main flavonoid of kumquat is DGPP. This compound is a derivative of phloretin, which is highly cherished in antioxidant skincare products. Although we know little about DGPP, phloretin reduced inflammation in mice with arthritis, asthma, and colitis [71, 72, 73, 74, 75].
Kumquats are also rich in margaritene and isomargaritene. The building block of both is called acacetin. Acacetin prevented inflammation in multiple animal and cellular studies [76, 77, 78, 79, 80, 81].
Fortunellin, another flavonoid in kumquats, protected mice from heart damage due to diabetes and IBD. It worked by blocking inflammatory responses [82, 65].
Kumquats’ less abundant compound, poncirin, also reduced inflammation in mice with colitis and stomach ulcers. Plus, it lowered the activation of inflammatory pathways in immune cells (macrophages) [66, 67, 83].
The anti-inflammatory flavonoids in kumquat probably act in synergy. Increasing your intake of this fruit might help prevent some chronic inflammatory issues – However, note that the research is limited to animal and cell studies, many of which didn’t test kumquat’s flavonoids but related compounds.
Immune System Support
Natural killer cells target and kill cancer cells or those infected by viruses. Kumquat extract activated and increased the capacity of natural killer cells in dishes and stressed mice. Its active compounds beta-cryptoxanthin and limonene likely carry this effect [8, 1].
Kumquats are a good source of vitamin C, which supports the immune system and may protect it from the harmful effects of free radicals. Vitamin C also helps white blood cells develop and move to infection sites [19].
Kumquat Essential Oil
Both the peel and seeds of kumquats are very rich in essential oil. It can be extracted by directly squeezing the peel (cold press) or by grinding the peel and seeds and distilling them with water [10+, 11+, 32, 13].
Kumquat essential oil mainly contains terpenoids such as limonene (up to 94%) and some others (beta-myrcene, germacrene D, and alpha-pinene). Limonene is found in most citruses and gives them that characteristic, refreshing fragrance [84, 85, 32, 86].
Several commercial brands of kumquat oil are available. You can use it alone or combine it with other essential oils. Its smell and taste are somewhat similar to other citrus essential oils… but it has something unique. This is probably due to an astonishing 82 components identified in the peel oil! [11]
People report using the oil in various ways, such as:
- Diluting one drop in 120 mL of liquid (e.g., for digestive issues)
- Adding a couple of drops in a diffuser (to ‘cleanse’ and perfume the air)
- 1-2 drops on the skin (e.g., for wounds and infections)
Because its main component limonene may cause skin allergic reactions if repeatedly used, it’s recommended to dissolve kumquat essential oil in carrier oils (coconut, avocado, olive) before applying it on the skin [87, 88, 89].
Do the benefits of the essential oil differ from those of the fruit? In short – to an extent. The oil is also packed with antioxidants and anti-inflammatory compounds. But it contains different active compounds. And unlike the fruit, preliminary evidence suggests it might also help fight infections and heal wounds.
Kumquat Essential Oil Benefits
Effective as:
Antioxidant
The terpenoids in kumquat essential oil are potent antioxidants. They broke down free radicals in several studies in test tubes [10, 85, 90, 32].
Possibly Effective for:
Dissolving Gallstones
Gallstones are small stones made up of bile components that build up in the gallbladder. Although normally harmless, they may cause inflammation in the gallbladder and pancreas. Kumquat’s component limonene dissolved gallstones at least partially in 75% of cases in a trial on 200 people. It was also effective in animals and test tubes. Further research in humans should confirm these promising, preliminary results [91, 92].
Animal and Cell Research (Lack of Evidence):
Researchers are investigating other potential benefits of kumquat essential oil. Because the research is mostly at the animal and cell stage, we cannot conclude that the oil has these benefits in humans.
Anti-Inflammatory
Kumquat essential oil reduced the production of an inflammatory messenger (nitric oxide) in immune cells (macrophages) [93].
Its main component limonene reduced inflammation in the kidneys, stomach lining, bowel, lungs, and airways in multiple animal studies [94, 95, 96, 97, 98, 99].
Cancer Prevention
Below, we will discuss some preliminary research on kumquat essential oil’s anticancer activity. Except for two small clinical trials (with modest results), it’s still in the animal and cell stage. Further clinical studies have yet to determine if its compounds are useful in cancer therapies.
Do not under any circumstances attempt to replace conventional cancer therapies with kumquat essential oil or any other supplements. If you want to use it as a supportive measure, talk to your doctor to avoid any unexpected interactions.
Kumquat essential oil reduced the growth and increased the death of prostate cancer cells in one study. Its main component, limonene, likely carries this effect [90].
In a trial on 32 people with advanced cancer, limonene reduced cancer progression in a woman with breast cancer and three people with colon cancer. Another trial on 40 women with breast cancer revealed that limonene can travel to the breast tissue, where it reduced a cancer-promoting protein [100, 101].
In animal and cell-based studies, limonene was active against the following cancer types:
- Breast [102, 103, 104, 105, 106, 107]
- Liver [108, 109, 110, 111]
- Stomach [112, 113, 114]
- Lung [115, 116, 117]
- Pancreatic [118, 119, 106]
- Colon [120, 121, 110]
- Skin [122, 123]
- Leukemia [124]
- Prostate [125]
- Lymph node [126]
Limonene prevented cancer in animals fed cancer-causing chemicals. It also reduced tumor growth and spread, while making cancer cells more sensitive to anticancer drugs.
However, this compound caused kidney cancer in rats. In these animals, it was transformed into a toxic compound. But this dangerous reaction only occurred in adult male rats, implying that limonene is highly unlikely to cause kidney cancer in humans [127, 128, 129].
Improving Metabolic Disorders
In diabetic mice, kumquat oil’s main component (limonene) lowered blood sugar, increased blood insulin, and prevented diabetes complications such as kidney damage and cataracts [130, 131].
In rats fed a high-fat diet, limonene reduced blood sugar, fat, and cholesterol levels. It also lowered insulin resistance and fat buildup in the liver, helping to prevent metabolic syndrome [132, 133].
Improving Digestive Issues
The essential oils of lemon and bitter orange – and their main components limonene and alpha-pinene – healed and prevented stomach ulcers in rats. They increased the production of protective mucus in the gut and helped the stomach lining regenerate. Limonene also reduced bowel inflammation in rats with colitis [134, 135, 136, 96].
Helping Heal Wounds
Limonene obtained from orange and fennel essential oils increased tissue repair and reduced inflammation in mice and rats with skin wounds. Since it’s the main component of kumquat essential oil, the same benefits are likely [137, 138].
Helping Fight Infections
In cell-based studies, kumquat essential oil reduced the growth of some bacteria causing [93, 86]:
- Acne and skin infections (Staphylococcus epidermidis, Cutibacterium acnes)
- Food poisoning (E. coli, Salmonella typhimurium, Staphylococcus aureus, Bacillus cereus)
Similarly, it inhibited some yeasts causing [93, 86]:
- Acne (Malassezia furfur)
- Thrush (Candida albicans)
For this reason, it has become a popular addition to skincare products. However, these are very preliminary results that have not yet been studied in humans or even in animals. Further research should determine if kumquat essential oil is effective against the diseases caused by these organisms.
How to Eat Kumquat
Fresh kumquats are best if eaten whole (with the peel). To avoid dirt and pesticide residues, it’s important to wash them first.
Because most people dislike the bitter taste of the seeds, it’s better to spit them out or cut the kumquat before eating it to remove them.
Some people say that gently rolling the fruit between your fingers before eating it will help release the essential oils and improve its taste.
Put the kumquat in your mouth and chew it well. The longer you chew, the sweeter it will taste. If you find the pulp too sour, you can eat the peel only or squeeze the juice out.
In addition to eating them as fresh fruits, you can use kumquats in a wide variety of ways. Some possibilities include:
- Marmalades, jams, and jellies
- Chutneys, marinades, and sauces
- Sliced in salads and sandwiches
- Baked into cakes or bread
- Pickled in vinegar
- Candied
- Ice cream
- Boiled in slices to make tea
- Extracts (infused in vodka)
- Using the peel as tiny dessert cups after scooping out the pulp
- Garnishing for cakes and cocktails
Take-away
Kumquats are unique, nutrient-dense, olive-sized citruses. Aside from providing you with important nutrients, they also boast a range of unique bioactive compounds. The fresh fruits may speed up your metabolism, boost fat-burning, and keep some chronic diseases at bay although more clinical research is needed to confirm these potential benefits. Unlike other citruses, the peel of kumquats is sweet and delivers an added dose of antioxidants.
The essential oil – although hard to come by – is fragrant and may help with skin health, wound healing, and gallstones according to limited evidence.
Next time you see an odd-looking small citrus in the store, give it a shot. And if you end up liking kumquats enough, it’s relatively easy to grow a small tree in your home.
Where to Buy and How to Choose Your Kumquat
Although kumquats are increasingly available, it’s still uncommon to find them at supermarkets. You can buy them from online retailers and specialty stores or, if you live in a region where they are grown, at farmer markets. And interestingly enough, you can also order them on online.
Another possibility is to buy a tree (you can get it on online), since they are small and grow well in pots. In addition to producing fruits, they make very nice decorative plants. Although they are relatively cold-resistant, it’s better to bring them indoors if winters get chilly where you live.
Their season depends on the variety, but most kumquats ripen between November and April. When buying kumquats, it’s important to check that the peel – which is very delicate – is not damaged. You might prefer to buy organic kumquats, since their peel will contain fewer pesticide residues.
Unlike other citrus fruits, their shelf life is quite short. If you’re not going to eat them in 2-3 days, it’s better to keep them in the fridge.
