Benefits
Smaller blood sugar rise after carbohydrate meals
In single-dose crossover trials, Salacia extract taken with a carbohydrate meal or sugar drink lowered the after-meal rise in blood sugar compared with control: by 14% and 22% (glucose area) at 240 and 480 mg in 66 adults with type 2 diabetes, and by about 34% at 1,000 mg in healthy adults. In two other studies only the insulin response fell significantly. These are short-term measures.
Lower insulin response after meals
Several single-meal trials found a smaller insulin rise with Salacia: 14% and 19% lower insulin area at 240 and 480 mg in adults with type 2 diabetes, 29% lower at 1,000 mg (but not at 500 or 700 mg) in healthy adults, and lower insulin area after a sugar drink at 300 and 500 mg (not 200 mg). The sugar-drink study was run by the extract maker.
Lower HbA1c and fasting blood sugar over 12 weeks
In 100 adults with prediabetes, 500 mg a day of S. reticulata extract for 12 weeks lowered fasting and after-glucose blood sugar and HbA1c more than placebo, and 600 mg a day of S. chinensis extract lowered HbA1c in another 12-week trial. In adults with type 2 diabetes, a Salacia tea lowered HbA1c versus placebo and a Salacia biscuit by 0.25 points. The trials used different products.
Mechanism of action
Slower carbohydrate digestion (alpha-glucosidase inhibition)
Salacia extracts inhibit alpha-glucosidase, the gut enzymes that split sugars and starches into absorbable glucose, so carbohydrate is absorbed more slowly. In a dose-response study, breath hydrogen rose as the Salacia dose increased, a sign that more carbohydrate reached the colon to be fermented by gut bacteria.
Other targets in laboratory studies
A review of laboratory and animal research reports that Salacia extracts also act on aldose reductase, pancreatic lipase, PPAR-alpha and GLUT4-mediated glucose uptake. These findings come mostly from cell and animal studies and have not been confirmed in people.
Gut hormone responses
In overweight adults, a single dose of S. chinensis with breakfast raised peptide YY and ghrelin peak areas but did not change GLP-1 area or overall appetite. In a 12-week trial in adults with prediabetes, total GLP-1 differed between the Salacia and placebo groups. What these hormone changes mean for everyday blood sugar is not known.
Clinical trials
Randomized, double-blind crossover study: a standard liquid meal alone or with 240 mg or 480 mg of S. oblonga extract. The first author was affiliated with Abbott Laboratories (Williams et al. 2007, Am J Clin Nutr)
66 adults with type 2 diabetes, tested after an overnight fast.
Both doses lowered the glucose area after the meal (by 14% and 22%) and the adjusted peak glucose (by 19% and 27%) versus the control meal, and lowered the insulin area (by 14% and 19%). Results apply to a single high-carbohydrate meal, not long-term blood sugar control.
Double-masked, randomized crossover study of a beverage meal with 0, 500, 700 or 1,000 mg of S. oblonga extract (Heacock et al. 2005, J Am Diet Assoc)
39 healthy adults without diabetes (average age about 26).
At 1,000 mg, the glucose area fell 23%, which was not statistically significant (P = .32), and the insulin area fell 29% (P = .01) versus control; 500 and 700 mg had no effect. Breath hydrogen rose with dose, suggesting more carbohydrate reached the colon.
Randomized, double-blind, placebo-controlled crossover study of a single 1,000 mg dose of NR-Salacia (S. chinensis extract) before a carbohydrate-rich meal (Koteshwar et al. 2013, Pharmacogn Mag)
Healthy adult volunteers.
Plasma glucose at 90 minutes was 13% lower than with placebo, and the glucose area over 180 minutes was about 34% lower. Mild abdominal cramping, bloating, vomiting and headache occurred in both the Salacia and placebo periods.
Randomized, double-blind, placebo-controlled crossover study of 200, 300 and 500 mg of S. chinensis extract taken with a sucrose drink; all authors were employed by the extract maker, OmniActive (Jeykodi et al. 2016, J Diabetes Res)
35 healthy adults.
The insulin area after the sugar drink was significantly lower than with placebo at 300 and 500 mg, but not at 200 mg, and the glucose area did not differ significantly at any dose. No significant adverse events were seen. This was a single-dose study.
Two randomized, double-blind, placebo-controlled studies: a single-dose crossover of 150, 300 or 600 mg, and a 12-week parallel trial of 600 mg a day; the first two authors worked for Kobayashi Pharmaceutical (Kobayashi et al. 2021, J Med Food)
Adult volunteers in both studies.
Single doses lowered blood glucose and insulin after a meal in a dose-dependent way, with 600 mg having the largest effect. Over 12 weeks, 600 mg a day improved several blood glucose measures, including HbA1c and glucose tolerance, compared with placebo.
Randomized, double-blind, placebo-controlled trial of 500 mg a day of a standardized S. reticulata extract for 12 weeks; one author worked for Daehan Chemtech, a Korean company (Baek et al. 2026, J Med Food)
100 adults with both raised fasting and raised after-glucose blood sugar (prediabetes).
Compared with placebo, the extract lowered fasting glucose, glucose at 90 and 120 minutes of a glucose tolerance test, glucose areas measured from 0 to 30 minutes through 0 to 120 minutes, HbA1c and triglycerides, and raised 1,5-anhydroglucitol. No clinically meaningful safety concerns were reported.
Randomized, double-blind, placebo-controlled crossover trial: Kothala Himbutu (S. reticulata) tea for 3 months and placebo tea for 3 months (Jayawardena et al. 2005, J Ethnopharmacol)
51 adults with stable type 2 diabetes, all given diet, exercise and lifestyle advice.
HbA1c at the end of the Salacia period was lower than after placebo (6.29% vs 6.65%, P = 0.008). The daily glibenclamide dose fell by 1.89 mg during the Salacia period and rose by 2.25 mg during placebo (P = 0.07).
Randomized, double-blind, placebo-controlled three-way crossover study of 300 or 500 mg of S. chinensis extract with a fixed breakfast; supported by OmniActive Health Technologies, a Salacia extract maker, and the US Department of Agriculture (Hao et al. 2017, Nutrients)
48 overweight or obese adults (average age about 32).
The extract did not change overall appetite after the meal, though hunger was lower in women at 300 mg. Glucose, insulin and amylin areas were lower than with placebo, peptide YY and ghrelin peaks were higher, and GLP-1 area did not differ.
Triple-blind, randomized, placebo-controlled two-period crossover trial of a Kothala Himbutu (S. reticulata) biscuit taken as a snack, with HbA1c as the primary outcome (Siribaddana et al. 2023, Cureus)
136 adults with type 2 diabetes randomized; average starting HbA1c about 8.5%.
HbA1c fell 0.35 points from baseline after the Salacia biscuit and 0.10 after the placebo biscuit, a difference of about 0.25 points in favor of Salacia. No serious kidney or liver adverse effects were reported.