Longan fruit has been used in Traditional Chinese Medicine for thousands of years as a remedy for many diseases, ranging from insomnia to snake bites. Researchers suspect that active compounds and antioxidants in longan may support cognition, brain and heart health, and immune defense – but how strong is the existing evidence? Read on to learn about the potential health benefits and side effects of longan.
What is Longan Fruit?
Traditional Uses
Longan (Dimocarpus Longan) is a fruit grown in China, India, Thailand, and many other Asian countries. It belongs to the same family (soapberry) as fruits like lychee [1].
The longan fruit is used as in Traditional Chinese Medicine (TCM) as a sleep aid, relaxant, to improve digestion, alleviate nerve pain, reduce fever, clean parasites, and even as an antidote to snake poison [1, 2].
The fruit looks like an eyeball when peeled, which earned it the name “dragon’s eye” in Chinese.
The fruit, flowers, and seeds of longan are all used to prepare traditional remedies. Longan flowers are sold in herb markets, have a fruity aroma, and are used to prepare an infusion in Taiwan. The powder of dried longan seeds is traditionally used to reduce bleeding, relieve swollen lymph glands, and soothe eczema [1].
Longan fruit is succulent and has gained popularity as an exotic refreshment. Thanks to this demand, longan fruit is now produced in large quantities in China. Wine from the longan fruit is also considered a “functional food” in TCM, used for various ailments [3, 4, 5].
However, longan supplements have not been approved by the FDA for medical use. Supplements generally lack solid clinical research. Regulations set manufacturing standards for them but don’t guarantee that they’re safe or effective. Speak with your doctor before supplementing.
Active Compounds & Mechanisms
Longan flowers, seeds, pulp, and the whole fruit contain a unique combination of bioactive compounds, many of which are still poorly understood.
Longan flowers and seeds are rich in polyphenols, which are antioxidants. They contain proanthocyanidins, which are also the main active compounds in grape seed extract and have been researched for supporting heart and immune health [1].
Longan fruit, pulp, and extracts contain:
- Antioxidants, such as ellagic acid, quercetin, and kaempferol [6, 7]
- Polysaccharides, which may boost immunity [6, 7]
- Adenosine, which is implicated in sleep and relaxation. Adenosine is also produced naturally in the body and is suspected to boost restorative deep sleep (opposite to caffeine) [8, 9].
- Uridine, which seems to boost cognition and mood in animals [8]
- Chlorogenic acid, which might support weight loss and protect the heart [7]
- GABA, the main “calming” and “relaxing” neurotransmitter [10]
- Vitamin C [11]
- Corilagin, which is being researched for reducing blood pressure [12]
On the whole, however, few clinical studies have been carried out with longan or its active compounds.
Scientists think that the pulp contains more active compounds than the fruit, but these can vary depending on the manufacturer and longan variety [7].
Longan leaf extract, although even less researched and used, seems to be rich in unusual and potentially anti-inflammatory sugar-bound flavonoids. Two of these compounds were completely unknown to science until recently – and they have yet to be studied in humans [13, 14].
Potential Health Benefits of Longan
Insufficient Evidence for:
The following purported benefits are only supported by limited, low-quality human studies.
There is insufficient evidence to support the use of longan for any of the below-listed uses. Remember to speak with a doctor before taking longan supplements. Longan and TCM remedies should never be used as a replacement for approved medical therapies.
1) Anemia
In a study of 200 pregnant women with anemia, a Traditional Chinese Medicine (TCM) combination, which included longan increased red blood cell count and hemoglobin. As an add-on remedy, it had a stronger effect than just the standard treatment (ferrous fumarate, vitamin C, and folic acid) after 2 weeks [15].
The same combination used for 2 weeks could also boost red blood cell, hemoglobin, and improve anemia in older people and in women with anemia [16, 17].
In all three of the above studies, longan was used as part of “dietotherapy,” a TCM approach that involved 6 g dried pulp and 2 eggs per day along with other specific herbs. The exact contribution of longan to the observed effects is unknown. Clinical trials are needed.
2) Insomnia
Dried seeds of longan fruit have long been used as a traditional remedy for insomnia. The indication in TCM for longan is to “revitalize the heart & spleen, nourish blood & calm the mind.” And although it’s still commonly used as a sleep aid, no clinical studies can attest to this effect [18].
Animal studies point to sleep-enhancing effects: longan improved sleep in stressed mice [19].
In mice, longan seed did not directly improve sleep but enhanced the effects of a sleep-inducing sedative (pentobarbital) by boosting GABA activity in the brain. We can’t translate findings from lab animals to humans [20].
Longan also contains adenosine, which had anxiety-relieving effects in mice. Adenosine is sometimes viewed as the body’s natural sleep aid, and one that caffeine blocks [8, 9].
Scientists hypothesize that the adenosine content in longan may help explain its traditional use for sleep and anxiety, but proper clinical trials are required to verify this [8, 9].
Lacking Evidence (Animal Research)
No clinical evidence supports the use of longan for any of the conditions listed in this section.
Below is a summary of the existing animal and cell-based research, which should guide further investigational efforts. However, the studies listed below should not be interpreted as supportive of any health benefit.
3) Brain Health
Longan flowers appeared to prevent Parkinson’s disease in rats. The authors suspect longan protected dopamine neurons in the brain from damage. Scientists are also investigating whether longan can boost antioxidants and reduce inflammation in brain cells [21].
In another animal experiment, polysaccharides from longan reduced brain damage in rats with stroke and increased antioxidant enzymes such as glutathione and SOD in the brain. They also increased the activity of genes that are hypothesized to protect brain cells (Bcl-2) [22].
A Traditional Chinese Medicine herbal mix containing longan seemed to prevent brain damage in mice with Alzheimer’s disease. This herbal mix was thought to activate an antioxidant protein (HO-1) in the brain’s memory hub, the hippocampus [23, 24].
Remember, however, that the effects of longan on brain health in humans are unknown due to a lack of clinical data.
4) Immune Defense
Scientists investigated how longan pulp increases the activity of white blood cells in cell studies [25, 26, 27].
The polysaccharides in longan are hypothesized to be its strongest immune-boosting compounds, but this hasn’t been confirmed. Researchers only suspect that the immune-enhancing effects might be stronger in a less acidic environment – at least in test tubes [25, 26, 27].
In one cell study, scientists explored whether longan polysaccharides increased in the number of spleen immune cells (splenocytes), whether these immune cells can ingest and degrade harmful foreign materials, and if longan can activate natural killer cells [28].
In one experiment, longan pulp polysaccharides increased antibody production in mice with suppressed immune systems [29].
Different polysaccharides in longan were also studying for enhancing the activity of immune B-cells, which make antibodies and are part of the Th2 response [30].
Human data are lacking.
5) Antioxidant Action
Longan is rich in gallic acid and ellagic acid, which have been described as excellent antioxidants. Researchers are studying if the fruit’s extract can neutralize free radicals and reduce inflammation in immune cells. The effects of longan extract and its antioxidants haven’t been investigated in humans, though [31].
In mice, longan extract appeared to reduce inflammation by boosting antioxidant enzymes such as glutathione and SOD [2].
Longan seeds extracts contain more ellagic acid than mango kernel extracts [32].
6) Inflammation
Scientists hypothesize that the antioxidants in longan may affect antioxidant enzymes and inflammatory pathways, but human data are lacking.
In immune cells, researchers explored whether longan reduces nitric oxide and TNF-alpha, both of which propel inflammation. Its effect on blocking a key inflammatory enzyme, COX-2, was also investigated. For example, a group of common OTC painkillers (NSAIDs) works by blocking COX-2 [2].
In another cell study, the flower extract was studied for reducing nitric oxide and inflammation better than the seed and pulp. The authors proposed that it might block inflammatory pathways that increase cytokines on a DNA level (NF-kB and AP-1, MAPK), but far more research is needed [33].
7) Diabetes
The impact of longan on diabetes in humans is unknown.
Longan flower extract improved insulin resistance in mice fed a high-sugar diet. It also appeared to boost antioxidant defense and prevent high blood pressure. Scientists think it merits to be researched in clinical trials of people with metabolic syndrome, a condition marked by insulin resistance [34].
8) Heart Health & Blood Pressure
A component from longan seeds (corilagin) reduced blood pressure in rats with high blood pressure. The authors hypothesize that longan may act by relaxing the blood vessels, reducing the fight-or-flight response, and decreasing noradrenaline. Clinical trials are needed to verify these proposed mechanisms [35].
9) Gout
We don’t know how longan might impact gout in humans.
In test tubes, longan leaves could somewhat block the enzyme (XOD) that causes uric acid buildup in gout. Many drugs used to treat gout black this enzyme, but their effectiveness has been clinically verified [36].
In the same cellular study, longan leaves had a weaker effect compared to the typical gout medication (allopurinol), while the fruit didn’t affect the XOD enzyme at all. The effects of longan were much weaker compared to papaya, which outdid even the conventional medication in this specific test (that doesn’t mean papaya is more effective than gout medication, though!) [36].
Scientists are also exploring whether longan seeds can block this pathway in cells. The seeds also seem to reduce blood uric acid levels in mice with gout [37].
10) Memory
Longan fruit extract improved learning and memory in mice, but its impact on human cognition remains unexplored [38].
In mice, the extract increased BDNF in the hippocampus, considered to be the most important brain region for memory one of the few ones where we know new brain cells can be created. This extract could also increase the survival of young brain cells [38].
A mix of 4 herbs including longan improved memory in mice with Alzheimer’s disease. It could also protect the brain from oxidative stress, which might be important for preventing cognitive decline [39].
11) Fat Burning
Although a couple of animal studies have been carried out, we know nothing about the impact of longan on fat burning and weight loss in humans. Have in mind that weight loss in lab animals – under controlled and unnatural settings – often doesn’t translate to any meaningful effect in humans.
That said, longan fruit extract prevented weight gain and a rise in blood lipids in rats fed a high-calorie diet. Its proposed effects wide included all of the following [40]:
- Reduced body weight and overall fat
- Reduced blood triglycerides levels
- Reduced liver fats
- Reduced the activity of genes implicated in storing fats in the body (FAS)
- Increased the activity of genes that reduce LDL (LDLR)
- Increased PPAR alpha, which is hypothesized to boost metabolism and fat burning
- Enhanced fat elimination through the stool
Longan fruit extracts also contain probiotic bacteria (Pediococcus pentosaceus), a type of lactic acid bacteria. This plant-based probiotic reduced weight gain, overall and liver fats in obese mice fed a high-fat diet. As with longan extract, human data on this probiotic strain are lacking [41].
12) Anti-Aging
According to one unverified theory, longan’s antioxidant compounds (which might neutralize free radicals) and its glucose-reducing and insulin-sensitizing potential warrant further research in the anti-aging science domain [42].
Researchers explored whether longan could reduce glycation in cells, a process that is theorized to contribute to aging. Glycation is a process during which important proteins and DNA are changed and their activity altered. Limited research suggests that people with diabetes, due to high blood sugar, might be especially affected by it [43, 44, 45].
Proanthocyanidins in longan fruit seemed to increase the response to insulin in animals. Theoretically, this might help prevent complications and aging-related health problems in people in diabetes [34, 46].
However, no clinical studies have confirmed this. Plus, many factors that drive aging are still unknown. For now, the purported anti-aging benefits of longan remain uncertain.
13) Energy Levels
Some scientists believe that the polysaccharides in the seed extract may reduce fatigue and boost energy. In mice, they enhanced endurance, increased energy stores, and reduced lactic acid, which causes muscle fatigue and cramps. Clinical studies haven’t been conducted [47].
14) Bone Health
One study explored whether longan fruit extract increases the activity of bone-building cells [48].
Cancer Research
Longan has not been shown to treat or prevent cancer.
Longan contains compounds that were researched mostly in cancer cells. A couple of experiments were done on lab animals. Scientists believe that phenolic compounds, flavonoids, and polysaccharides found in the flowers, fruit, or seed may have some value, but this is still uncertain [49, 50, 51].
Remember that many substances have anti-cancer effects in cells, including downright toxic chemicals like bleach. This doesn’t mean that they have any medical value. On the contrary, most substances (natural or synthetic) that are researched in cancer cells fail to pass further animal studies or clinical trials due to a lack of safety or efficacy.
Longan seed extracts were researched in lymphoma, colon, liver, breast, uterine, and lung cancer cells. Based on these experiments, some researchers think that longan deserves to be studied further in breast cancer cells [1].
On a DNA level, longan is being investigated for affecting the activity of genes that help cancer cells divide and spread. Scientists want to know if it can silence cancer-causing genes, also known as “oncogenes”, and turn on cancer-fighting genes, “antioncogenes” in cells [1].
One of the “bad” genes that is hypothesized to be especially important (cyclin D1) is implicated in several aspects of cancer, from its initial growth and spreading to drug resistance and metastasis. The clinical relevance of this gene is still uncertain, though [1].
Scientists also explored the following types of longan formulations and the pathways they might act upon in cells:
- Longan seed extract on matrix metalloproteinases (in test tubes and in colon cancer cells). MMPs are hypothesized to help cancers invade tissues and cause metastases [52, 53, 54].
- Longan flower extract on autodestructive mechanisms – caspases and processes in the mitochondria (by increasing Bcl-2) – implicated in cancer and autoimmune and brain diseases [1].
High-quality longan fruit extracts over their isolated ingredients on liver, lung, and stomach cancers [55, 56, 57].
One research team is chemically modifying a compound from longan fruit (an alpha D-glucan) to see if it is active against a type of head and neck cancer in cells [58].
Thus, much more research is needed before the effects of longan on cancer in people are determined.
Limitations and Caveats
Clinical studies investigating the effects of longan are lacking The majority of studies have been done in mice or cells. Just a couple of studies examined the effects of longan as a herbal combination in Traditional Chinese Medicine.
Various studies focused on different parts of the plant, such as the fruit, pulp, seed, or specific extracts. The fruit varieties, its parts, and extracts differ a lot in the number of active compounds they contain.
Longan Side Effects & Safety
Keep in mind that the safety profile of longan is relatively unknown, given the lack of well-designed clinical studies. The side effects described here are not exhaustive and you should consult your doctor about other potential side effects, based on your health condition and possible drug or supplement interactions.
Some people may be allergic to longan. In one reported case, a man with mango allergies and asthma experienced itching, hives, and swelling after consuming longan [59].
Lychee contains compounds that may dramatically reduce blood sugar in humans. Several medical issues have been associated with lychee, which belongs to the same family as longan. It’s unknown if longan fruit may have the same effects. It’s particularly important to consult your doctor before supplementing if you are on anti-diabetes medication [60, 61, 62].
Longan Supplementation
Natural Sources
Longan fruit is sold fresh in Asian markets, or available as a dried fruit, mostly in Chinese stores.
Longan is also limitedly available in tincture, capsules, or powder form [63].
Extracts are made from the flowers, fruit, or seeds. Most supplements are Traditional Chinese Medicine preparations, in which longan is often combined with other herbs. You may see “Long Yan Rou” on some supplements – this is the Chinese name for longan.
Dosage
Due to the lack of clinical studies, a proper longan dosage cannot be established.
A couple of conducted clinical studies used 6 g of the dried pulp/day.
The typical TCM dosage is 6 – 15 g/day of the fruit.
