Supplement analysis backed by scientific evidence · PT

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Limited evidenceWeight management

Yacon Syrup

Yacon syrup is essentially a fructooligosaccharide syrup — a prebiotic fibre with real effects on satiety and bowel habit. The single trial that made it a weight-loss phenomenon has never been replicated, and it is still a sugar-containing syrup.

What the science says

  • Causes weight loss Limited evidence

    The trial behind the hype ran 120 days in obese, mildly dyslipidemic premenopausal women at 0.14–0.29 g fructooligosaccharides/kg/day and reported significant decreases in body weight, waist circumference and BMI. No subsequent study has reproduced anything close: a 2025 systematic review of the last decade found only 7 trials totalling 161 participants, and none replicated that magnitude of weight loss.

  • Improves insulin sensitivity Limited evidence

    The original trial reported lower fasting insulin and HOMA-IR, and the 2025 review found reductions in fasting insulin, HOMA-IR and LDL cholesterol across the small literature. Acute postprandial glucose results were inconsistent and appeared to depend on each participant's baseline gut microbiota — a plausible explanation for why the effect does not travel between populations.

  • Increases satiety and bowel regularity Moderate evidence

    This is the most consistent finding and the least surprising: fructooligosaccharides reliably increase defecation frequency, shorten intestinal transit time and raise reported satiety. It is the standard prebiotic-fibre effect, available from cheaper sources such as inulin.

Dosage & safety

Studied doseStudies identified 0.14 g fructooligosaccharides/kg/day as the well-tolerated dose (about 10 g FOS, roughly 20–40 g of syrup for a 70 kg adult); 0.29 g/kg/day produced unacceptable GI symptoms. Typical retail label servings of 1–2 teaspoons (about 5–14 g of syrup) deliver considerably less FOS than the trials used.
SafetyDose-dependent bloating, flatulence, cramping and diarrhoea are the main issue and the main reason people stop; symptoms often ease with continued use. Fructooligosaccharides are a FODMAP — avoid if you have IBS with fermentable-carbohydrate sensitivity, SIBO or fructose malabsorption. Yacon syrup still contains free fructose and glucose alongside FOS, so it is not calorie-free and is not a zero-impact sweetener for people with diabetes. No safety data beyond about four months of use. Not studied in pregnancy or in children.

Scientific references

Where to buy

Zint, Organics, Yacon Syrup, Prebiotic Sweetener, 8 fl oz (236 ml)

View on iHerb

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