Benefits
Digestive symptom scores alongside a prescribed acid reducer
In a double-blind Iranian trial of quince syrup as an add-on to a drug, 96 young children with reflux symptoms took ranitidine plus quince syrup or a sugar syrup placebo twice daily for 4 weeks. Total symptom scores differed at weeks 2, 4 and 6, in the authors' reading in favor of quince; swallowing difficulty and choking did not differ. It is one small trial.
Symptom scores in head-to-head trials with acid-reducing drugs
In 80 children with reflux symptoms, quince syrup and omeprazole both lowered symptom scores from baseline, with no significant difference between them, which does not show the two are equal. In an open-label trial in 137 pregnant women, general symptom scores differed between quince sauce and ranitidine at 2 weeks but not at the 4 week end point. Neither trial had a placebo, so neither shows how much quince helps on its own.
Nausea scores compared with vitamin B6 tablets
In 76 women 6 to 14 weeks pregnant with mild to moderate nausea and vomiting, a tablespoon of quince syrup three times daily for a week lowered a standard nausea score more than vitamin B6 tablets. There was no placebo, the quince group started with higher scores, and blinding was not described. Pooled analyses that rank quince highly rest on this one trial.
Bleeding and clotting times in mice and rats (animal work)
In mice, 14 days of an oral quince extract at 20 to 80 mg/kg a day lengthened bleeding and clotting times with rising dose and reduced deaths in a lung clot model, and in rats it lowered clot weight. These are animal results only; they are a reason for caution alongside blood thinners, not a benefit shown in people.
Blood fats and liver enzymes in a rat model (animal work)
In rats made diabetic with streptozotocin, an oral water extract of quince fruit lowered triglycerides and total and LDL cholesterol, raised HDL cholesterol, and reduced the liver enzyme ALT and the kidney markers urea and creatinine. No human trial of quince fruit has tested these measures.
Inflammatory signals in immune cells treated with peel polyphenols (lab work)
In human macrophage-like cells stimulated with bacterial LPS, a polyphenol extract of quince peel lowered release of TNF-alpha and IL-8, raised IL-10, and blocked activation of NF-kB, p38MAPK and Akt. This is test-tube work with a concentrated peel extract, not evidence from eating the fruit.
Mechanism of action
Pectin and fiber in the fruit
Quince fruit is known for its high pectin content, reported at about 2 g per 100 g, with crude fiber around 1.6 g per 100 g, which makes it useful as a gelling ingredient for paste and jelly. Whether pectin explains the symptom changes seen in the syrup trials has not been tested.
Polyphenols and inflammatory signaling (cell studies)
Quince fruit and leaf extracts contain phenolic compounds such as chlorogenic acid. In cell studies, a quince peel polyphenol extract dampened the NF-kB, p38MAPK and Akt pathways in stimulated immune cells. Whether eating the fruit has this effect in people is unknown.
Clotting-related prostanoids (animal studies)
In rats and mice given an oral quince extract, thromboxane B2 fell and 6-keto-PGF1α rose, which the authors link to a shift in the prostacyclin and thromboxane balance, alongside longer bleeding and clotting times. This has not been studied in people.
Clinical trials
Double-blind randomized trial at the gastroenterology clinic of Ghaem Hospital, Mashhad, Iran. Both groups took ranitidine syrup; one group added quince syrup and the other a sugar syrup placebo, twice daily for 4 weeks, per the registry record (IRCT20170501033750N2, registered retrospectively); funded by Babol University of Medical Sciences. (Naeimi et al. 2019, Complement Ther Med)
96 children with suspected gastroesophageal reflux disease (registered age range 1 to 4 years) seen at the clinic in 2017.
Total digestive symptom scores on the GSQ-YC questionnaire differed significantly between groups at week 2 (17.8 vs 23.4), week 4 (11.5 vs 18.8) and week 6 (12.2 vs 21.1); the authors conclude in favor of adding quince. Vomiting, refusal to eat, burping and belly pain differed at weeks 4 and 6, while swallowing difficulty and choking did not differ at any time point. The abstract does not give the quince syrup amount or report adverse events.
Randomized trial described as double-blind, from Shiraz University of Medical Sciences, Iran, comparing quince syrup with the acid-reducing drug omeprazole. (Zohalinezhad et al. 2015, Complement Ther Clin Pract)
80 children with symptomatic GERD, from infants to age 18; quince syrup 0.6 mL/kg/day or omeprazole (given in the abstract as 1 mL/kg/day).
Mean cumulative symptom scores fell from baseline in both groups at weeks 4 and 7, with no significant difference between groups. In children aged 5 to 18, scores were higher again at week 7 in both groups. With no placebo arm, the trial cannot show how much either treatment beat no treatment, and the lack of a difference does not show that the two are equal.
Randomized, open-label, active-controlled trial from Iranian schools of Persian medicine comparing concentrated quince fruit extract (quince sauce) with ranitidine for 4 weeks. (Shakeri et al. 2018, J Obstet Gynaecol)
137 pregnant women with GERD; ranitidine 150 mg twice daily or quince sauce after meals (dose listed in the abstract as 10 mg).
The General Symptom Score was lower with quince sauce than with ranitidine at 2 weeks (p = 0.036) but did not differ at 4 weeks (p = 0.074). Major Symptom Scores did not differ at 2 or 4 weeks. The trial was open-label with no placebo, so it does not show how well quince works on its own.
Randomized trial from Iranian traditional medicine and obstetrics departments comparing quince syrup with vitamin B6 tablets for 1 week, scored with the PUQE-24 nausea and vomiting scale. (Jafari-Dehkordi et al. 2017, J Obstet Gynaecol)
76 women at 6 to 14 weeks of pregnancy with mild to moderate nausea and vomiting (40 quince syrup, 1 tablespoon three times daily; 36 vitamin B6, 20 mg three times daily).
PUQE-24 scores fell from 9.5 to 5.2 on day 7 and 5.3 on day 14 with quince syrup, and from 8.4 to 7.3 and 7.7 with vitamin B6; the change was larger with quince (p < 0.001). There was no placebo, the quince group started with higher scores, and the abstract does not describe blinding, which would be hard with a syrup versus tablets.
Animal study of an aqueous Cydonia oblonga extract, a plant used in Uyghur medicine, on bleeding, clotting, clot breakdown and experimental thrombosis. (Zhou et al. 2014, J Ethnopharmacol)
Mice given the extract by mouth at 20, 40 or 80 mg/kg/day for 14 days versus untreated controls, plus rat thrombosis models.
Bleeding time lengthened 2.17 to 3.63 times and clotting time 1.44 to 2.48 times versus controls, deaths in a lung clot model fell by 27 to 53%, and clot weights in rats fell with dose. Thromboxane B2 fell and 6-keto-PGF1α rose. No human study has tested whether eating quince changes clotting.
Animal study of an aqueous extract of Cydonia oblonga fruit on blood fats and liver and kidney markers. (Mirmohammadlu et al. 2015, Iran J Pharm Res)
Rats with streptozotocin-induced diabetes given the fruit extract by mouth; doses are not given in the abstract.
Triglycerides, total cholesterol and LDL cholesterol fell and HDL cholesterol rose versus untreated diabetic rats; the liver enzyme ALT fell, and the rise in urea and creatinine was prevented. These are animal findings and have not been tested in people.