Benefits
Fasting glucose and HbA1c
In two Korean placebo-controlled trials in adults with type 2 diabetes, pinitol at 1,200 mg was reported to lower fasting glucose, HbA1c and the insulin-resistance score HOMA-IR. In the larger, 66-person trial everyone stayed on oral glucose-lowering drugs, and the HbA1c drop was significant in those starting above 8% but not below. In older adults without diabetes, 2 g a day for 6 weeks did not change fasting glucose or insulin.
Insulin sensitivity measured by clamp and glucose tolerance tests
Trials that measured insulin action directly found no effect. In 22 adults with obesity and raised blood sugar, about 20 mg/kg a day for 4 weeks did not change insulin-driven glucose uptake on a clamp test. In older adults without diabetes, 2 g a day for 6 weeks, or a single 1 g dose, did not change glucose tolerance, insulin sensitivity or muscle insulin-receptor activation.
Post-meal blood sugar after a carbohydrate load
In 15 Korean adults with type 2 diabetes, 1.2 g of pinitol taken 60 minutes before a rice meal lowered the rise in blood glucose, with no change in insulin. In 30 healthy adults, a pinitol-rich drink lowered glucose and insulin 45 and 60 minutes later at a 6 g dose, but not at 2.5 or 4 g. These were one-day tests, not long-term use.
Creatine retention and resistance training results
In a 3-day pilot in 20 young men, adding 0.5 g of D-pinitol twice a day to creatine loading raised estimated creatine retention from 61% to 83%, while 2 g a day did not help. In a later 4-week double-blind trial in 24 trained men, creatine retention did not differ with or without pinitol, and lean mass rose more with creatine alone.
Liver fat and liver enzyme levels
In a 12-week double-blind trial in 90 adults with fatty liver confirmed by ultrasound, pinitol at 300 or 500 mg a day was reported to lower liver fat content, liver enzymes, a urinary oxidative-stress marker and post-meal triglycerides compared with placebo. It is a single trial in people with a diagnosed liver condition and has not been repeated.
Mechanism of action
Raises blood D-chiro-inositol
In a 4-week trial, adults taking D-pinitol had blood pinitol levels 48 times and D-chiro-inositol levels 14 times those of the placebo group. This is why D-pinitol is linked to D-chiro-inositol, an inositol involved in insulin signaling, although the higher levels did not improve insulin sensitivity in that trial.
Insulin-like effect on muscle cells in lab and animal work
In rat muscle cells, D-pinitol increased glucose uptake through a PI3-kinase dependent pathway, and an oral dose lowered high blood glucose in insulin-deficient mice but not in normal or obese mice. In mice given a glucose load, oral D-pinitol increased movement of the GLUT4 glucose transporter in muscle. These are lab and animal findings.
Slow absorption and hormone effects
In healthy volunteers, oral D-pinitol peaked in blood after almost 4 hours and had a half-life over 5 hours. A 15 mg/kg dose did not change glucose but lowered insulin and raised glucagon and ghrelin. From a sugary carob syrup, peak levels were about 40% of those expected, probably because the sugars compete for absorption.
Clinical trials
Randomized, double-blind, placebo-controlled trial of soybean-derived pinitol 20 mg/kg/day for 28 days, with insulin sensitivity measured by hyperinsulinemic-euglycemic clamp and glucose, fatty acid and glycerol kinetics. (Davis et al. 2000, Diabetes Care)
22 adults with obesity (mean BMI 36.6) and diet-treated type 2 diabetes or glucose intolerance; 12 pinitol, 10 placebo.
Pinitol did not change baseline glucose production, insulin-mediated glucose disposal, or the release of free fatty acids and glycerol. Blood pinitol rose 48-fold and D-chiro-inositol 14-fold compared with placebo, and no toxicity was observed. The primary insulin-sensitivity outcome was null.
Randomized, placebo-controlled trial of 1,000 mg pinitol twice daily in a non-nutritive drink during weeks 2 to 7 of a 7-week protocol, with oral and intravenous glucose tolerance tests and thigh muscle biopsies. (Campbell et al. 2004, J Nutr)
15 older adults without diabetes (6 men, 9 women; mean age 66); 7 pinitol, 8 placebo.
Urinary pinitol rose 17-fold, but fasting glucose, insulin and C-peptide, the responses to oral and intravenous glucose, insulin sensitivity indices, and muscle insulin-receptor content and activation were all unchanged. No effect on any glucose outcome.
Double-blind, placebo-controlled crossover study with four 1-day trials: 1,000 mg pinitol or placebo, followed 60 minutes later by 75 g glucose or a sham drink, with muscle biopsies. (Stull et al. 2009, Horm Metab Res)
15 older adults without diabetes (mean age 62).
Blood pinitol rose and stayed raised for 240 minutes, but pinitol did not change glucose or insulin responses, insulin sensitivity, or activation of the muscle insulin receptor. The dose was absorbed but had no measured effect.
Randomized, double-blind, placebo-controlled, parallel-group trial of 600 mg soybean-derived pinitol twice daily for 13 weeks at a hospital in Pusan, Korea. (Kim et al. 2005, Eur J Clin Nutr)
30 Korean adults with type 2 diabetes.
The abstract reports that pinitol significantly lowered fasting glucose, insulin, fructosamine, HbA1c and HOMA-IR, and lowered total and LDL cholesterol and blood pressure while raising HDL. It does not give group sizes or the size of each change. A short report from a small single-center trial.
Randomized, placebo-controlled trial of 1,200 mg pinitol or a matching placebo in people who kept taking their usual oral glucose-lowering drugs. (Kim et al. 2012, Ann Nutr Metab)
66 Korean adults with type 2 diabetes who had taken oral glucose-lowering drugs for at least 3 months; 33 pinitol, 33 placebo.
HbA1c, fasting glucose and HOMA-IR fell more with pinitol than with placebo. The HbA1c drop was significant in people starting above 8.0% (p < 0.01) but not in those below 8.0% (p = 0.16). Adiponectin, free fatty acids and CRP did not differ between groups. The abstract does not state the trial length.
Single-blind pilot in which subjects matched for body mass were randomly assigned to placebo, creatine alone (5 g four times daily), creatine with 1 g/day or 2 g/day D-pinitol, or 5 days of D-pinitol before creatine with D-pinitol, for 3 days; retention estimated from urinary creatine. Not indexed in PubMed. (Greenwood et al. 2001, J Exerc Physiol Online)
20 healthy young men with no prior creatine use, split across five groups.
Estimated 3-day creatine retention was 49.7 g (83%) with creatine plus 1 g/day D-pinitol versus 36.6 g (61%) with creatine alone (p < 0.03). The 2 g/day dose gave no benefit (36.7 g), and the pre-loading group reached 46.7 g (p = 0.08). Retention was estimated from urine, not measured in muscle, and the study was partly funded by the D-pinitol maker, Humanetics, and by MetaResponse Sciences.
Randomized, double-blind trial of creatine plus D-pinitol versus creatine alone (20 g/day for 5 days, then 5 g/day for 23 days) during a supervised 4-week resistance training program. (Kerksick et al. 2009, J Strength Cond Res)
24 resistance-trained men.
Whole-body creatine retention rose in both groups with no difference between them. Strength and body composition improved in both groups, but lean mass and fat-free mass rose significantly more with creatine alone (p < 0.05). Adding D-pinitol gave no extra benefit.
Randomized, double-blind, placebo-controlled trial of placebo, low-dose (300 mg/day) or high-dose (500 mg/day) pinitol for 12 weeks, measuring liver fat, liver enzymes, lipids and oxidative stress. (Lee et al. 2019, J Nutr Biochem)
90 adults with fatty liver confirmed by ultrasound.
The pinitol group had significantly lower liver fat content, liver enzymes, urinary malondialdehyde and post-meal triglycerides, and higher glutathione peroxidase, than the placebo group. The abstract does not report the size of the changes or results for each dose separately.