That’s the English name. They call it “long yan rou” in China, which translates as dragon’s eye meat. There, it has been used as part of their herbal medicinal practices for at least several hundred years. According to that tradition, it is believed to:
- benefit sleep and insomnia
- help with rapid heartbeat
- reduce anxiety and promote tranquility
- support the spleen and blood
- improve the appearance of skin
To be clear, that list is what traditional Eastern medicine purports. Those are not health advantages backed by Western medicine. In fact, if you look in the NIH’s PubMed database, you won’t find a single human clinical trial involving longan fruit. No for any disease or condition!
However, researchers here have begun studying the fruit more in the laboratory to explore the possibility of benefits. Some of their findings are quite intriguing.
Non GMO Longan Fruit Plant 無基改龍眼樹
What is longan fruit?
credit: Pouletic via Wikimedia Commons
About the size of a ping pong ball, this fruit comes from a subtropical tree which is native to the southern portion of China and Burma. Reaching up to 40 feet in height, it grows as wide as it does tall. A fully mature Dimocarpus longan tree can produce a massive crop of up to 500 lbs. of fruit (1).
Since each piece only weighs around 4 grams (0.14 oz.), that means up to 50,000 fruits per year, per tree.
In scientific circles, it’s also called Euphoria longan Lour. and Dimocarpus longan Lour. For the layman, misspellings of it are common including logan and lonan.
What does longan taste like?
For starters, you don’t eat the peel. That part is always discarded. The seed is rarely consumed, except when it is ground up and used in some herbal tonics, such as for a tea.
The sweet and juicy pulp is the part you eat. Its flavor is often compared to its relative, the lychee. Both are members of the soapberry family (Sapindaceae). Others compare its taste to the honeydew melon.
However you want to describe it, you won’t use the name of a citrus fruit. The longan has no acidity, or at least not any that your tongue will detect.
The scent is extremely subtle yet unique – if your nose can detect it, you will probably agree it’s what a gardenia flower smells like, albeit much milder.
As a food, it may be an acquired taste for you.
This is because of a distinct musky aftertaste, which is experienced with some varieties more than others. It’s most noticeable on the dried longan, since the flavors are concentrated. But after you devour a bag or two, you should be hooked!
Where can you buy it fresh?
The short answer is not many places. Your best option will be the dried, which are also delicious.
In addition to its native homeland, you will find this evergreen tree grown in Thailand, Taiwan, India, Vietnam, and Sri Lanka. It does need a change of seasons but without frost, which excludes the fully tropical climates.
Even trying to grow a longan tree in the Philippines – which is just a couple hundred miles south of Taiwan – doesn’t work. The constant warmth and lack of distinct seasons results in the tree not bearing fruit.
While you’re unlikely to find a longan tree for sale in California at most nurseries, some areas in Los Angeles, Orange, and San Diego counties can work well for growing it. Though it doesn’t handle SoCal’s hot summers very well, which will be an issue outside of the coastal communities. No one is growing it commercially in the CA.
It wasn’t until the 1990’s when commercial production of it began in the state of Florida (2). If you’re lucky enough to find fresh longan fruit for sale anywhere in the United States, chances are it was grown in Florida.
Since it does contain a lot of water, making longan fruit juice would be a nice treat if you can get your hands on the fresh stuff.
A number of tropical fruit farms in Florida grow it, which means you can find it fresh there when in season – July and August. Outside of that time and state, we haven’t seen it for sale (if you have, please share in the comments).
Here in Los Angeles where Superfoodly is based, we have never seen it for sale at Whole Foods, Trader Joe’s, or a place like Walmart. Where to buy it dried? Not at those places either!
Luckily, we remain satisfied buying the dried version online. Some sellers offer them by the pound for a reasonable price. You can’t use the dry ones for juicing, but adding a few to smoothies can work out great.
Even though it’s reportedly been used in Eastern medicine for several hundred years, if not longer, it’s a new food to Western cultures.
To give you an idea of just how early the science is about this fruit, only 68 pieces of research about it are found in the NIH’s PubMed database. Out of those, over 90% (63 of them) were published within just the past 10 years.
And we reiterate, none are clinical trials.
That means with the exception of the more straightforward benefits like vitamin and mineral content, all the other possible perks are unproven and only theoretical at this point. As fascinating as they are to read about, keep that in mind.
1. Nutritional value
Starting with the non-controversial stuff first.
A lot of people refer to it as a longan berry or a grape, even though it’s neither.
That being said, its nutrition is comparable to many berries, at least in terms of how many calories and grams of sugar (carbs) are found in a comparable serving size.
Fresh Longan Fruit Nutrition Facts Serving Size: 100g (about 3.5 ounces) Calories 60 Calories From Fat 0 % Daily Value* % Daily Value Total Fat 0.1g 0% Vitamin A 0 IU 0% Sodium 0mg 0% Vitamin C 84mg 140% Potassium 266mg 7% Vitamin B2 (riboflavin) 0.1mg 8% Total Carbs. 15g 5% Calcium 1mg 0% Fiber 1.1g 4% Iron 0.13mg 1% Protein 1.3g 2% Magnesium 10mg 2% *Percent Daily Values (DV) are based on a 2,000 calorie diet
Source: USDA National Nutrient Database
When looking at the basic nutrition facts, to be honest there’s nothing impressive with the exception of one nutrient… vitamin C.
How much vitamin C there is in longans is actually more than fresh oranges. A 100 gram serving of oranges will give you 88% of your daily value, versus 140% when eating “the dragon’s eye.”
Almost all of the values will be multiplied when eating the dried fruit. It’s much more nutritionally dense with the exception of vitamin C, as a fair amount degrades and breaks down over time (the same happens with dried berries).
The amount of moisture left can vary by supplier, but the USDA’s entry for the dried pegs the calorie count at 286 for the same 3.5 ounce weight… which is over 4x higher than fresh. That happens with any food when the water is removed.
One ounce is the typical serving size for dried berries and similar. How many calories there are in that same serving size of dried longans is comparable… 80 to 100 calories.
In 2016, researchers out of Thailand published a study looked at the anti-inflammatory benefits of longan (3). Not just the fleshy pulp we eat, but also testing the flower (which precedes the fruit formation) as well as the seed.
They tested is using macrophages in the lab. Those are a type of white blood cell which translates as “big eaters” in Greek.
That’s exactly what they do… macrophages are formed in response to an infection and “eat” the invader. They also break down foreign substances which shouldn’t be there and play an important in our body’s inflammation.
The bad news? The flower extract was the most effective at helping with those. No one eats that part.
The good news? The part we eat – the pulp – was also found to be anti-inflammatory.
The cited scientific reason why was because they inhibited lipopolysaccharide (LPS) induced nitric oxide production. The plain English explanation is their conclusion, which is simple to understand:
“These results suggest that the longan extracts possess anti-inflammatory property. Therefore, longan could provide potential dietary supplement for the treatment of inflammatory-related diseases.”
“Inflammatory diseases” is a rather broad category. Arthritis might be an obvious example, but the truth is that a lot of disease are either caused or made worse by inflammation.
Another study from back in 2012 looked at just the pericarps (4). See the diagram as to which parts those are.
We eat the mescocarp (the flesh) but not the exocarp (the peel) or the endocarp (the skin of inner seed).
Throughout the entire study, they only reference the pericarp, which is an umbrella term that includes all 3 of those things. So in their test, both the edible and non-edible parts were used.
They took these parts, dried them in an oven, and then ground them to become a powder. Next, they put the powder in a centrifuge and filtered away fiber and other inactive components. Last, they freeze dried the powder and used it to create a water-based concentration to test out on male mice.
Using topically applied carrageenan, they first caused inflammation on the hind paws of the mice (yes, that carrageenan found in most brands of almond milk is not good for you).
Next, they applied the concentration made from the fruit to see if it would help reduce inflammation. The last sentence of their conclusion was very similar to what the 2016 study said:
“Overall, the results suggest that longan pericarp may have the potential to be developed as a natural antioxidant or inflammatory inhibitor.”
3. Memory and cognition
Is this fruit a nooptropic – something that can enhance memory and cognitive function?
While it’s far too early to know, a study involving mice suggested just that possibility.
A university in South Korea tested out the pulp extract for 14 days in mice (5). Each day, they gave the mice a daily dose of either the fruit or plain saline water.
- The tested group received 50, 100, 200, or 400 mg per kg of body weight. This supplement was given orally.
- The control/placebo group received an equal volume of 0.9% saline water.
After comparing results from these two groups, it was said:
“…longan fruit enhances learning and memory, and that its beneficial effects are mediated, in part, by BDNF expression and immature neuronal survival.”
The dosage of longan extract pictured above was 200 mg per kg of body weight (which wasn’t even the highest dose tested). It appeared this benefited the hippocampus region of the brain for those three things measured.
In the intro of this study, they talk about how in Traditional Chinese Medicine, the fruit is prescribed as a tonic for forgetfulness, insomnia, and when caused by anxiety, heart palpitations. If there is any legitimacy to those alleged benefits, one has to wonder if the above research might be describing the actual mechanisms responsible.
This fruit has a lot of sugar content. Upon first impression, most would say that’s a very bad thing.
However the types of sugar it has – polysaccharides – were studied on rats at a university in China (7). The big surprise? These sugars seemed to correlate with protective effects on the brain.
Using an operation, a type of brain injury was intentionally inflicted on the rats; middle cerebral artery occlusion (MCAO).
Some rats received an oral dosage of longan polysaccharides at a dosage of 0.05 to 0.20g per kg of body weight, for 14 days prior to this injury.
Other rats received nimodipine, which is a medication used in humans for cerebral hemorrhaging.
The size of the injury (subsequent infarct) was reduced by the following percentages:
- 8% with the lowest longan dose (0.05g/kg)
- 13% with the middle dosage (0.10g/kg)
- 29.5% with the highest dose (0.20g/kg)
That compares to the 14% reduction in the rats getting the medication (nimodipine) at a dosage of 0.02g/kg.
The rate of edema also was improved in a dose-dependent manner using the fruit.
This led the researchers to conclude:
“The data suggest that polysaccharides of the Euphoria Longan (Lour.) Steud are capable of alleviating I/R injury by a mechanism that may involve decreasing oxidative stress.”
Before they grow into fruits, there are flowers on the longan tree. No one eats them, but the flower extract was studiedat university in Taiwan (8).
Using specialized lab rats which represented a Parkinson’s disease model, they tested oral administration of the flower extract on them. Based on their results, they said it…
“…appears to be useful in preventing and/or treating central nervous system neurodegenerative diseases, including Parkinsonism.”
Remember these are only mice and rat studies, and only two at that. It’s not enough to even be conclusive for thoseanimals, let alone humans.
On the topic of its polysaccharides but not specific to neurological, lab research suggests they might also play a role in some aspects of cancer metabolism.
In mice models, these sugars from the pulp were said to show NK (natural killer) cell cytotoxicity against a major type of lymphoma cell (9). Three specific types of the polysaccharides were suspected as being responsible for the apparent in vitro anti-cancer and immune system activity (10).
Other research has also observed anti-tumor activity from the polysaccharides in the lab (11).
5. Energy and fatigue
Is it an energy booster? While the study didn’t involve the fleshy pulp, a hot water extract of the seeds was studied in mice (12).
The dosages given were 50, 100, 200, and 400 mg per kg of body weight. After giving the mice swimming tests, it was said that the longan seed polysaccharides:
- extended swimming time
- increased hepatic glycogen
- reduced blood urea nitrogen
- decreased blood lactic acid
But apparently this was only statistically significant in groups receiving the two lower dosages.
For another study, this one using the flower extract in rats, the researchers said it (13):
“…characterizes antiobesity and hypolipidemic effects in vivo.”
But it’s totally unknown if during that 9 week period, the rats were more active, and if they were, whether it was because they had more energy. Those things weren’t monitored.
In short, there’s insufficient evidence to suggest it fights fatigue, even in animals. The exception being that most fruits, because of their sugar content, can provide at least a short-term boost of energy.
That’s why some people claim that even though they don’t contain caffeine, apples wake you up better than coffee. Coincidentally, a medium apple contains 13 grams of sugar, which is about the exact same amount found in a 100 gram serving of fresh longan. A one ounce serving of dried will have roughly the same amount.
The two potential drawbacks
With the exception of vitamin C – which it’s a very rich source of – there aren’t many antioxidants in longans.
Based on its ORAC value, which measures total antioxidant activity, its number of 330 is comparable to cantaloupe melon (319) and boiled carrots (326). Not impressive.
Those numbers are quite low relative to many superfoods. Even your average red apple with skin is 10x higher, when compared on an equal weight basis.
Is this bad? Not necessarily. Yes, it’s bad in the sense that you can’t count on this food as a source of antioxidants with the exception of vitamin C. But what’s good about it– as ironic as that may sound – is that it implies any other health benefits coming from it are not due to the antioxidants.
If any of the researched health benefits turn out to be for real, it’s likely they are coming from other phytonutrients in the plant.
That’s helpful to know because often, it’s unknown whether a given food is helping a condition in a unique way, or if it’s just a side effect of the fruit’s antioxidant content (which can happen with a few diseases, but notthe majority).
The other drawback has to do with its sugar. Is longan fruit for diabetics a good idea? Probably not.
On a per ounce basis of the fresh pulp, the sugar content is actually comparable to some other fruits. At 14 grams for 3.5 ounces, it’s similar to banana which is 12 grams.
That’s a lot, even for tropical fruit, which are known for their high sugar content.
How much sugar it has along with its low fiber content can create a bad side effect for diabetics. It means the sugar will hit the bloodstream relatively quick.
What’s the glycemic index of longan fruit?
Believe it or not, no one has measured it. While that may seem surprising, it’s not a simple lab test.
To find out, you need at least 10 healthy volunteers who are willing to consume 50 grams of the food and have their blood sugar monitored before and after. That’s according to the University of Sydney, who is the leader in the field of GI testing and research (14).
And while longan is not a berry, it is similar in portion size and testing those aren’t easy.
Given their standard serving size, many berries have a negligible impact on blood sugar. That’s why the raspberry’s GI value and load cannot be measured using the same glycemic index methodology.
But berries have lots of fiber, typically 3 to 6x more than this fruit does. Perhaps the incorrect moniker of longan grape is the best way to describe it, because just like grapes there’s a lot of sugar, with very little fiber to boot.
Even without knowing the glycemic index or glycemic load of longans, based on its basic nutrition facts, it’s safe to predict that it would not be a good choice if you have type 1 or type 2 diabetes.
For everyone else, it’s perfectly healthy so long as you eat it in moderation.
As far as other side effects of longan fruit and its parts, toxicological studies where rats were given high amounts for 13 weeks didn’t seem to find anything unusual (15).
Is it possible that you can have a longan fruit allergy?
Theoretically, yes – you can be allergic to the proteins in any food. That being said, for this particular food, it seems to be quite rare. Only one case study of an allergic reaction has been published on a single patient (16).
That’s not to say there aren’t others out there, but apparently it’s not common enough or causing bad enough side effects for other doctors to be writing about it, like they do with common food allergies.
How to Grow a Longan Tree
Slow growing to only about 6-7 metres, they will fit in many smaller gardens too, and will grow from tropical to subtropical zones, or also in less humid climates like California, or South and Western Australia, if they have plenty of protection from hot, dry winds in summer, which will probably cause the fruit to drop. Their preferred climate is a warm, humid summer followed by a cooler, dry winter. Some evidence suggests that areas with a number of days with minimum temperatures under 12 degrees C (54F) will produce better longan crops.
If you’re in a cooler district, create a warm microclimate for them in winter as cold, windy and rainy weather can interfere with pollination. As longans grow naturally as understory trees in the elevated rainforests of southern Asia, you will also need to protect your tree from direct sun, especially in its early years by growing it under shadecloth or in the dappled shade of another tree’s canopy. If you grow it unprotected, the leaves will inevitably burn, even in cooler climates. Longan trees are slightly more tolerant of frost than lychee.
Soil doesn’t need to be particularly rich but should be slightly acidic (pH of 5.5-6) and also well-drained, as longan trees will not tolerate ‘wet feet’ at all. A light, sandy loam is ideal. Although you could start them off in a large pot, they will eventually need to be grown in the ground to produce any quantity of fruit.
Flowers are scented, creamy-yellow and held in panicles and although there are both male and female flowers, the tree is self-fertile. Longan fruit appears in drooping clusters, ripening in mid to late summer. Each fruit is small and round, with a dull-yellow, thin outer ‘shell’ covering a white, translucent membrane (which is the fruit) and shiny black seed inside. Cut off the entire cluster but make sure you don’t harvest under-ripe fruit as it will not ripen after picking.
Longans are not quite as juicy as a lychee and they’re often described as slightly ‘musky’ by comparison but they are still tasty and good in cooking.
Growing them in Australia is easy along most of the east coast, with the added bonus that they are not attacked by fruit fly. There are people growing longans successfully in Perth and Victoria by creating the right microclimate. They also grow well in northern New Zealand.
In the USA they can be grown throughout the Zones 8-10 and also thrive in many parts of southern California.
Longan trees can be grown from fresh seed but, as seeds are very short lived, they are usually reproduced by cuttings or aerial layering (marcottage). New trees can take several years to become fruit-bearing.
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