Jamun (black plum): nutrition, health claims and what research shows on diabetes

In early June 2026, jamun, the dark purple to nearly black seasonal fruit known in Bangladesh as jam, was arriving in markets across the country. On 8 June that year Jagonews24 published a health feature on it, citing the US National Center for Biotechnology Information (NCBI) and the National Library of Medicine. It said jamun contains vitamins, minerals, antioxidants and dietary fibre, and that eating it regularly in moderation can help with blood-sugar control, digestion, immunity and heart health.

This report checks those claims against health authorities, official food-composition tables and peer-reviewed research. It separates what has been tested in people from what has only been seen in animals or laboratory experiments, and from what rests on tradition alone. It also explains what the jamun tree is, where the fruit is traded in Bangladesh, and who should talk to a doctor before eating it. Every fact here comes from sources published on or before 8 June 2026.

Jamun is Syzygium cumini, an evergreen tree of the myrtle family (Myrtaceae), the family that also includes cloves and guava. In English the fruit is called black plum, Java plum, jambolan or Indian blackberry. A 2012 review in the Asian Pacific Journal of Tropical Biomedicine by M. Ayyanar and P. Subash-Babu describes the tree as native to the Indian subcontinent, growing in India, Bangladesh, Myanmar, Nepal, Pakistan, Sri Lanka and Indonesia.

According to Wikipedia, the tree can grow to 30 m and live for more than 100 years. It flowers in March and April and its fruit develops by May or June. As it ripens the fruit turns from green to pink, then crimson and finally black. Its taste combines sweet, mildly sour and astringent notes, and it stains the tongue purple. Ayyanar and Subash-Babu describe greyish-brown bark, leathery leaves and small, fragrant, greenish-white flowers borne in clusters; the fruit is 1.5 to 3.5 cm long with a single large seed.

In her 1987 book Fruits of Warm Climates, hosted by Purdue University's New Crop Resource Online Program, the horticulturist Julia Morton wrote that jamun grows from sea level to about 1,800 m but does not fruit above about 600 m. It thrives in areas of heavy rainfall and, once established, tolerates drought; it does best on higher, well-drained land. In India the fruiting season runs from late May through June and July.

Morton noted that jamun seeds lose their viability quickly and germinate in about two weeks. Semi-hardwood cuttings treated with growth hormones gave about 20 percent success, and the tree is also propagated by budding, grafting and air-layering. The fruit is picked by hand as it ripens, so a tree needs several pickings over a season. Wikipedia records that the species is considered invasive in Florida, South Africa, parts of the Caribbean and Hawaii, where it crowds out native vegetation.

In Bangladesh, jamun comes mostly from trees in homesteads, beside ponds and along roads; commercial orchards are rare. The Daily Star's Bangla edition reported on 28 June 2023 that Bangladesh produced 8.786 million tonnes of fruit on 474,000 hectares in 2006-07, rising to 14.3 million tonnes on 734,000 hectares in 2021-22. Over the same period the number of fruit types grown rose from 56 to 72, and daily fruit intake per person rose from 55 g in 2006 to 85 g in 2018. The report listed jamun among the fruits grown on a large scale, though it gave no separate production figure for it.

Muladuli in Ishwardi, Pabna, is known as a major wholesale market for jamun. The Daily Ittefaq reported on 29 June 2024 that, in season, jamun worth Tk 2 million to 2.5 million changed hands there every day, and three to four truckloads left daily for Dhaka, Chattogram, Sylhet, Barishal and other parts of the country. Three local types are sold there, known as hari jam, thaki jam and khude jam. Wholesale prices were Tk 80 to 100 a kilogram depending on size, and retail prices Tk 140 to 160. Because jamun has a short season, the market runs for a month at most.

In the same report, the depot owner Aminur Rahman Babu said people from seven or eight upazilas, including Ishwardi, bring jamun to Muladuli, and that jamun worth roughly Tk 25 million to 30 million is traded there each year. The Ishwardi upazila agriculture officer, Mita Sarkar, said commercial jamun farming had not yet begun in Ishwardi, and expressed hope that the volume of trade would one day encourage farmers to plant jamun orchards.

The Daulatdia ferry ghat area of Goalanda upazila in Rajbari is another trading point. The Daily Star's Bangla edition reported on 14 June 2024 that, by traders' estimates, 18,000 to 20,000 kg of ripe jamun went from there to Dhaka every day. According to the Goalanda upazila agriculture office, the upazila had 4,760 jamun trees and was expected to yield 238 tonnes that year, with an average price of Tk 105 a kilogram. The upazila agriculture officer said the average price the previous year had been Tk 55. The local season there runs from the second week of May to the last week of June.

Prices are higher in the capital. The Daily Observer reported from Karwan Bazar on 20 May 2025 that large jamun was selling wholesale at Tk 350 to 400 a kilogram and retail at Tk 500 to 550. A vendor there told the paper that jamun is not cultivated much any more, and that fewer trees mean a limited supply.

Sources do not agree on jamun's nutritional values; the figures vary with the variety, ripeness, soil and method of analysis. The most relevant table for Bangladesh is the Food Composition Table for Bangladesh, compiled by the Institute of Nutrition and Food Science (INFS) at the University of Dhaka and published in June 2013 with support from the National Food Policy Capacity Strengthening Programme. Its entry for kalojam (jambolan, raw) gives the following per 100 g of edible portion:

• energy 39 kcal; water 88.2 g
• protein 0.9 g; fat 0.5 g; available carbohydrate 6.1 g
• total dietary fibre 3.5 g
• calcium 23 mg; iron 0.8 mg; magnesium 37 mg; phosphorus 16 mg
• potassium 172 mg; sodium 28 mg; zinc 0.21 mg
• vitamin A 93 µg; thiamin 0.09 mg; riboflavin 0.02 mg
• vitamin C 74.1 mg

The US Department of Agriculture's FoodData Central lists "Java-plum (jambolan), raw" with quite different values per 100 g: 60 kcal, 83.1 g water, 15.6 g carbohydrate, 0.72 g protein, 0.23 g fat, 19 mg calcium, 0.19 mg iron, 15 mg magnesium, 79 mg potassium and 14.3 mg vitamin C. The analysis cited in Julia Morton's book gives 1.2 to 1.62 mg iron, 55 mg potassium and 5.7 to 18 mg vitamin C per 100 g, with 0.3 to 0.9 g crude fibre.

A 2022 review in the journal Foods by Madiha Qamar and colleagues in Pakistan shows how wide the range is: across the studies it compiled, vitamin C in jamun ranged from 5.7 to 137 mg per 100 g. The authors write that jamun contains good amounts of vitamins, minerals and fibre and is low in calories and fat. Rather than relying on a single number, it is fairer to say that jamun is a juicy, low-calorie fruit that contains vitamin C and potassium, in amounts that vary widely from fruit to fruit.

Jamun's colour comes from pigments called anthocyanins. Ayyanar and Subash-Babu list several glycosides of delphinidin, malvidin and petunidin in the fruit, along with gallic acid and sugars such as raffinose, glucose and fructose. Qamar and colleagues report that the peel holds more phenolic compounds than the pulp or the seed, and that peel extract showed greater antioxidant activity in laboratory tests.

The Jagonews24 feature said that compounds called jamboline and jambosine in jamun's seed and fruit help convert carbohydrate into sugar slowly. The sources state this more cautiously. Both Morton's book and the Ayyanar and Subash-Babu review say the seed is claimed to contain an alkaloid, jambosine, and a glycoside, jambolin or antimellin, which halts the conversion of starch into sugar. In other words, this is a claim about the seed, not about the ripe flesh.

Jamun seeds have long been used in folk treatment of diabetes in South Asia. Morton wrote that in 1940 a researcher named Mercier found that an aqueous seed extract injected into dogs lowered blood sugar for long periods, but had no effect when given by mouth. She also cited work at the Central Drug Research Institute in Lucknow, India, in which a dried alcoholic extract of the seeds, given orally, reduced blood sugar and glycosuria in patients. Ayyanar and Subash-Babu note that the anti-diabetic activity of different parts of the plant has been tested in diabetic animals since the 1960s and 1970s, but that most of these studies used crude preparations without establishing their chemical profile.

Controlled trials in people have given mixed results. Claudia Teixeira and colleagues at the Federal University of Rio Grande do Sul in Brazil ran a double-blind, randomised controlled trial in patients with type 2 diabetes, reported in Diabetes Care in 2004 and in full in the Journal of Clinical Pharmacy and Therapeutics in 2006. Twenty-seven patients were followed for 28 days in three groups: one received a tea made from jamun leaves, one the standard diabetes drug glyburide, and one a placebo. Fasting blood glucose fell significantly with glyburide but did not change with the jamun-leaf tea or the placebo. The researchers concluded that tea made from jamun leaves has no blood-sugar-lowering effect.

Writing in the Journal of Ethnopharmacology in 2006, the same group reported that experiments in normal rats, diabetic rats, healthy volunteers and patients with diabetes were all negative for an effect of jamun-leaf tea and extracts on blood sugar, and concluded that patients and physicians should not rely on it. On the other hand, the 2022 Foods review cites a 2010 clinical trial by Sahana and colleagues that reported oral jamun-seed preparations to be effective in type 2 diabetes with no toxic effects. The authors of both reviews say more clinical research is needed to identify the active compounds and confirm any benefit.

The US National Center for Complementary and Integrative Health (NCCIH), in a page updated in November 2023, is clear that medical treatment for diabetes should not be replaced with an unproven health product or practice, that dietary supplements may interact with medicines, and that for most supplements there is no evidence of benefit in diabetes. The World Health Organization's fact sheet of 14 November 2024 says the number of people living with diabetes rose from 200 million in 1990 to 830 million in 2022, and that diabetes directly caused 1.6 million deaths in 2021. WHO advises reaching and keeping a healthy weight, being physically active, eating a healthy diet that avoids sugar and saturated fat, and not smoking; treatment can require medicines such as metformin and, when needed, insulin.

People with diabetes who want to eat jamun should therefore remember that ripe jamun also contains sugar, which counts towards their daily carbohydrate. Neither the fruit, nor jamun-seed powder, nor jamun-leaf tea is a substitute for diabetes medicine. Never stop or reduce medicine or insulin on your own; if you want to eat jamun or any part of the plant regularly, talk to your doctor or a dietitian first.

The original feature called jamun rich in dietary fibre. The INFS table gives 3.5 g of total dietary fibre per 100 g, a moderate amount; the older analysis cited by Morton gives 0.3 to 0.9 g of crude fibre. MedlinePlus, the health information service of the US National Library of Medicine, says soluble fibre attracts water and turns to gel during digestion, slowing it, and may help lower cholesterol, while insoluble fibre adds bulk to the stool and appears to help food pass more quickly through the stomach and intestines. No study in people on whether jamun's own fibre eases constipation was found in the sources.

On vitamin C, MedlinePlus (January 2025) says the vitamin is needed to form collagen, a protein used to make skin, tendons, ligaments and blood vessels; it helps heal wounds, aids the absorption of iron and, as an antioxidant, blocks some of the damage caused by free radicals. The body cannot make or store vitamin C, so it must come from food. Adult men need 90 mg a day and adult women 75 mg. By the INFS figure, 100 g of jamun could supply a large share of that; by the USDA figure, much less.

No study in people supporting the original claim that jamun helps the body fight viruses, bacteria and infections was found in the sources. MedlinePlus says that for most people vitamin C supplements or vitamin C-rich foods do not reduce the risk of catching a cold; people who take supplements regularly may have slightly shorter colds or somewhat milder symptoms. The antimicrobial and antioxidant activities reported for jamun extracts are, in Ayyanar and Subash-Babu's words, mainly from experimental settings.

MedlinePlus says the body needs potassium to support heart health, muscle function and bone health. Jamun contains 172 mg of potassium per 100 g by the INFS figure and 79 mg by the USDA figure; it is not among the fruits MedlinePlus names as good potassium sources, such as bananas, citrus fruits, kiwi and apricots. No direct study in people showing that jamun controls blood pressure or lowers the risk of heart disease was found in the sources; the cardioprotective and lipid-lowering effects mentioned by Qamar and colleagues come from animal and laboratory work.

The original feature said jamun's iron and vitamin C may slightly reduce the risk of anaemia. The iron figures differ widely between sources: 0.8 mg per 100 g by INFS, 0.19 mg by USDA and 1.2 to 1.62 mg in the analysis cited by Morton. That does not make jamun a significant source of iron, so the anaemia claim has been left out of this report. MedlinePlus does say that vitamin C aids iron absorption from food. Anyone with symptoms of anaemia should have a blood test and see a doctor.

No trials in people were found for the claims about brighter skin, slower ageing or liver protection. Qamar and colleagues say the evidence for liver protection comes from animals and various laboratory models. On weight, jamun has 39 kcal per 100 g by the INFS figure and 60 kcal by the USDA figure, so it is a low-calorie fruit, but no specific study showing that eating it leads to weight loss was found. The original's claim that jamun gives energy and freshness in hot weather was not found in any authoritative source and has been dropped.

The original said jamun leaves and bark have long been used in traditional medicine, and the sources confirm it. Ayyanar and Subash-Babu record traditional use of the bark for sore throat, bronchitis, asthma, dysentery and ulcers, and of the fruit to remove bad breath. Morton wrote that a decoction of the bark is taken for dysentery and diarrhoea and used as a gargle for mouth complaints. These are descriptions of traditional use, not proof that they work; no study in people showing that jamun strengthens the gums was found.

According to Morton, jamun bark contains 8 to 19 percent tannin, is widely used for tanning leather and yields durable brown dyes. The same book warns that excessive oral intake of tannin-rich plant products can be dangerous to health. Jamun wood is red or reddish-grey with a close, straight grain, and has been used for beams, posts, bridges, boats, farm implements and railway sleepers. The leaves are used as livestock fodder, and the flowers are much visited by bees; Morton noted that in India's Western Ghats jamun flowers furnish most of the honey.

Jamun has kitchen uses as well. Morton wrote that the ripe fruit is eaten raw and made into tarts, sauces and jam, and that soaking it in salt water reduces its astringency. In India and other tropical countries the juice is made into jelly, sherbet and syrup, and even vinegar. The 2022 Foods review likewise says jamun is eaten fresh, as chutney and as jam, and that its juice is used for syrups, sherbets and squashes.

The fruit also has deep roots in the region's culture. Wikipedia notes that Buddhist texts describe the young Buddha meditating under a jambu tree, and that the fruit appears in Hindu tradition. In Bangladesh, the Daily Ittefaq opened its 2024 report on the Ishwardi jamun market by recalling a line from the rural poet Jasimuddin's poem "Mamar Bari", in which children colour their mouths with the sweet juice of ripe jamun.

People with kidney disease need to be careful. MedlinePlus (April 2026) says people with kidney problems, particularly those on dialysis, should not eat too many potassium-rich foods. In a report in the Daily Star's Bangla edition on 12 June 2024, Rehana Begum, associate professor of food and nutrition science at the Government College of Applied Human Science, likewise said kidney patients who want to eat jamun must consult a doctor first.

For the reasons given above, people with diabetes should not use jamun fruit, seed or leaves in place of their medicine, and should not stop their medicine. They should tell their doctor before using any herbal product, since NCCIH warns that supplements may interact with medicines. Care is also needed with home-made decoctions of jamun bark or seed, because Morton's book warns that excessive intake of tannin-rich plant products can be dangerous. Pregnant women, children and people with long-term illnesses should talk to a doctor before using jamun seed or leaves as a remedy.

For healthy people, jamun can be part of a balanced diet like any other seasonal fruit. WHO's healthy-diet fact sheet of 26 January 2026 says everyone older than 10 should aim for at least 400 g of fruit and vegetables a day, and that a healthy diet helps protect against malnutrition and against noncommunicable diseases including diabetes, heart disease, stroke and cancer. WHO also advises keeping free sugars below 10 percent of daily energy, so whole fruit is a better choice than sweetened jamun drinks or jam.

Photo: Adityamadhav83 / Wikimedia Commons (CC BY-SA 3.0)

Sources: Jagonews24; Institute of Nutrition and Food Science, University of Dhaka (Food Composition Table for Bangladesh, 2013); USDA FoodData Central; World Health Organization; MedlinePlus (US National Library of Medicine); US National Center for Complementary and Integrative Health; Asian Pacific Journal of Tropical Biomedicine; Foods (MDPI); Diabetes Care; Journal of Clinical Pharmacy and Therapeutics; Journal of Ethnopharmacology; Julia Morton, Fruits of Warm Climates (Purdue University); The Daily Ittefaq; The Daily Star Bangla; The Daily Observer; Wikipedia