How we rate
“Strong” = several concordant meta-analyses or systematic reviews. “Moderate” = one synthesis, or several controlled trials. “Limited” = early trials only. The rating is about the quality of the studies, not about how useful the supplement is.
Chitosan
Marketed to "bind fats", chitosan causes a weight loss of barely 1 to 2 kg more than a placebo, a loss deemed clinically insignificant in good quality trials; it slightly lowers cholesterol.
Benefits
- Cholesterol: an average of −0.20 mmol/L of total cholesterol and LDL in an analysis of 14 trials (1,108 participants), with no effect on HDL or triglycerides.
- Weight: 1.7 kg more lost than with a placebo in the Cochrane review (15 trials, 1,219 participants), between 0.89 and 1.84 kg according to more recent meta-analyses.
- Blood glucose: a drop in fasting blood glucose and glycated hemoglobin in a meta-analysis of 10 trials (1,473 people with metabolic syndrome or diabetes), mostly at 1.6 to 3 g per day for at least 13 weeks.
- With a diet: in 72 adults with hepatic steatosis ("fatty liver") following a diet at −500 kcal per day, 1.5 g per day for 8 weeks slightly reduced weight, waist circumference, and liver enzymes more than a placebo.
Precautions
Transit: in 60 women taking 3 g per day for 12 weeks, stools became harder (towards constipation) and gut microbiota diversity decreased. Tolerance: no more adverse effects than with a placebo in the Cochrane review, and no severe adverse effects reported in the analysis of 14 trials. Vitamins: at 4.5 and 6.75 g per day for 8 weeks, no drop in vitamins A, E, D or blood carotenoids. Limitations: what does not work: in the only good quality trials, weight loss drops to 0.6 kg, with no clear difference from placebo; a 2021 meta-analysis concludes that the loss does not reach the 2.5 kg threshold deemed useful. The largest trial: in 250 adults, 3 g per day for 24 weeks caused a weight loss of only 0.4 kg, versus 0.2 kg regained under placebo, a difference that the authors deem clinically insignificant. No "bound" fats: in 12 volunteers, chitosan did not increase fats eliminated in stools, and the Cochrane review sees no difference either. Cholesterol: two trials find no effect, one at 4.5 and 6.75 g per day for 8 weeks, the other in 88 obese adults without a diet. Blood pressure: no drop in systolic pressure in a meta-analysis of 8 trials (617 participants), a drop in diastolic pressure only in trials exceeding 2.4 g per day and lasting less than 12 weeks; another meta-analysis finds −2.68 mmHg for systolic.
Recommended dosage
1.5 to 3 g per day in recent trials, up to 6.75 g per day in a safety trial.
How to take it
- For whom: most trials involve overweight or obese adults, sometimes with high cholesterol.
- Dose: 3 g per day in the largest trial (250 adults, 24 weeks); 1.5 to 3 g per day in recent trials.
- Duration: 4 to 24 weeks in weight trials; for blood glucose, the effect only appears in studies lasting at least 13 weeks.
- Multiple intakes: trials divide the dose into 2 or 3 intakes per day, in capsules or tablets.
- Without a diet, nothing: in 88 obese adults without dietary instructions, no effect on weight or cholesterol; recent positive trials often combine it with a diet or a lifestyle change.
- Timing of intake: no study in this sheet compares taking it before, during, or after a meal.
Did you know?
Sold as a "fat blocker", chitosan did not increase fat excretion in the stools of 12 volunteers, whereas orlistat, a drug, increased it by 16 g per day.
What the studies say
This large network meta-analysis compares the effects of 18 nutraceuticals on weight loss in overweight or obese adults, including 111 randomized clinical trials and 6171 participants. Regarding chitosan, the study indicates, with moderate certainty, a small improvement in body weight (-1.70 kg). Overall, nutraceutical supplementations may lead to slight weight loss.
Shahinfar H, Jayedi A, Torabynasab K, Payandeh N, Martami F, Moosavi H, Bazshahi E, Shab-Bidar S. — Pharmacological research (2023) — View the source study
For information only: not a substitute for medical advice. Dietary supplements are not a replacement for a varied, balanced diet. Learn more