What the evidence says. Early or small human trials; promising but not yet conclusive.
Nutrition per serving 1 cup, pitted (96 g)
Water79.5 g83%
Sugars13.1 g14%
Fibre1.1 g1%
Other carbs0.2 g0%
Protein1.3 g1%
Fat0.1 g0%
What's in one serving, by weight — average composition (USDA).One serving as % of the adult daily requirement (FDA Daily Values). The bold outer ring = 100% of a day's needs.
Longan (Dimocarpus longan) is a fruit used for exceptionally high vitamin c density for an antioxidant/immune-support contribution. NutriDex grades the human evidence as Preliminary. Longan ("dragon's eye") is a lychee relative whose fresh pulp is unusually rich in vitamin C and contains hydrolysable tannins (corilagin, gallic and ellagic acid) and bioactive polysaccharides. The great majority of the evidence is preclinical: cell and rodent studies show antioxidant, anti-inflammatory, anti-hyperglycemic (alpha-amylase/alpha-glucosidase inhibition), immunomodulatory and antitumor activity, mostly from concentrated pericarp, seed or polysaccharide extracts rather than the amount of pulp a person would eat. Human data are very sparse: a single 12-week randomized, double-blind, placebo-controlled trial (n=50, ages 55-75) of a longan pulp-and-seed extract beverage found a significant reduction in the bone-turnover marker alkaline phosphatase versus placebo, with no significant change in lipid or glycemic markers and a good safety profile. No large prospective cohorts or meta-analyses isolate whole longan intake from overall fruit consumption. Reported antioxidant/anti-diabetic effects also depend heavily on extract type and processing (e.g., thermal "aging" raises phenolic content), limiting translation to the raw fruit. Overall the human evidence is preliminary, and longan is best regarded as a nutritious vitamin-C-dense fruit rather than a proven therapeutic.
Purported Benefits
✓Exceptionally high vitamin C density for an antioxidant/immune-support contribution
✓Polyphenols (gallic acid, corilagin, ellagic acid) with in-vitro antioxidant and free-radical-scavenging activity
✓Preclinical anti-hyperglycemic effects via alpha-amylase / alpha-glucosidase inhibition (extract studies)
✓Longan-pulp polysaccharides show immunomodulatory and antitumor activity in animal/cell models
✓Possible favorable shift in a bone-turnover marker (single small human RCT of a pulp/seed extract)
✓Low fat, source of potassium and copper
Dosing & Compounds
Typical Dose
About 1 cup of fresh pitted pulp (~96 g, roughly 20-30 fruits); dried longan is far more energy- and sugar-dense per gram.
Active Compounds
Vitamin C (L-ascorbic acid)Hydrolysable tannins (corilagin, gallic acid, ethyl gallate)Ellagic acid and ellagitanninsFlavonoids (epicatechin, quercetin glycosides)Bioactive polysaccharides / polysaccharide-protein complexesPotassium and copperB-vitamins (riboflavin)
Safety & Cautions
⚠
Generally safe as a food. Dried longan is concentrated in sugar and calories and can spike blood glucose, so people with diabetes should account for it. Possible cross-reactive allergy in those sensitive to lychee or other Sapindaceae fruits. As with unripe lychee, eating large amounts on an empty/undernourished stomach has been linked theoretically to hypoglycin-type effects—keep portions moderate, especially in children. Bioactive-extract supplements are not interchangeable with the fruit and lack long-term human safety data; potential additive effects with glucose-lowering or immune-modulating drugs are unstudied. Educational only — always check with your doctor or pharmacist before combining Longan with any medicine.
Longan is most often taken for Exceptionally high vitamin C density for an antioxidant/immune-support contribution, Polyphenols (gallic acid, corilagin, ellagic acid) with in-vitro antioxidant and free-radical-scavenging activity, Preclinical anti-hyperglycemic effects via alpha-amylase / alpha-glucosidase inhibition (extract studies), Longan-pulp polysaccharides show immunomodulatory and antitumor activity in animal/cell models. Vitamin C-rich "dragon's eye" with polyphenol-packed pulp
Does Longan work — what does the evidence say?
Preliminary evidence. Early or small human trials; promising but not yet conclusive. Longan ("dragon's eye") is a lychee relative whose fresh pulp is unusually rich in vitamin C and contains hydrolysable tannins (corilagin, gallic and ellagic acid) and bioactive polysaccharides. The great majority of the evidence is preclinical: cell and rodent studies show antioxidant, anti-inflammatory, anti-hyperglycemic (alpha-amylase/alpha-glucosidase inhibition), immunomodulatory and antitumor activity, mostly from concentrated pericarp, seed or polysaccharide extracts rather than the amount of pulp a person would eat. Human data are very sparse: a single 12-week randomized, double-blind, placebo-controlled trial (n=50, ages 55-75) of a longan pulp-and-seed extract beverage found a significant reduction in the bone-turnover marker alkaline phosphatase versus placebo, with no significant change in lipid or glycemic markers and a good safety profile. No large prospective cohorts or meta-analyses isolate whole longan intake from overall fruit consumption. Reported antioxidant/anti-diabetic effects also depend heavily on extract type and processing (e.g., thermal "aging" raises phenolic content), limiting translation to the raw fruit. Overall the human evidence is preliminary, and longan is best regarded as a nutritious vitamin-C-dense fruit rather than a proven therapeutic.
What is the typical dose of Longan?
About 1 cup of fresh pitted pulp (~96 g, roughly 20-30 fruits); dried longan is far more energy- and sugar-dense per gram.
Is Longan safe? Any cautions or side effects?
Generally safe as a food. Dried longan is concentrated in sugar and calories and can spike blood glucose, so people with diabetes should account for it. Possible cross-reactive allergy in those sensitive to lychee or other Sapindaceae fruits. As with unripe lychee, eating large amounts on an empty/undernourished stomach has been linked theoretically to hypoglycin-type effects—keep portions moderate, especially in children. Bioactive-extract supplements are not interchangeable with the fruit and lack long-term human safety data; potential additive effects with glucose-lowering or immune-modulating drugs are unstudied.
How many studies support Longan?
NutriDex cites 8 sources for Longan, graded "Preliminary".
Cite this page
APA
Peh, D. (2026). Longan (Dimocarpus longan): Benefits, Dosage, Side Effects & Evidence. NutriDex — The Supplement Research Compendium. Retrieved 16 Sept 2026, from https://nutridex.info/s/longan
BibTeX
@misc{nutridex_longan,
author = {Peh, Daryl},
title = {Longan (Dimocarpus longan): Benefits, Dosage, Side Effects \& Evidence},
year = {2026},
howpublished = {NutriDex --- The Supplement Research Compendium},
url = {https://nutridex.info/s/longan},
note = {Reviewed by Dr Daryl Peh, MBBS Singapore, MMed FM. Accessed 2026-09-16}
}
For medical claims, citing the underlying primary studies linked above is preferred. NutriDex is an educational reference, not medical advice.