Benefits
Supports healthy blood sugar levels
In pooled analyses of small randomized trials in adults with prediabetes or early type 2 diabetes, oral aloe lowered fasting blood glucose and HbA1c more than placebo. One pooled analysis found a fasting glucose effect but no HbA1c change in prediabetes, and reviewers rated the trials few, varied in product and of poor quality.
Supports healthy blood lipid levels
In the same randomized trials in adults with prediabetes or early type 2 diabetes, aloe lowered triglycerides, total cholesterol and LDL cholesterol and raised HDL cholesterol compared with placebo. These were secondary outcomes, and in one trial the cholesterol and triglyceride changes appeared only at the higher of two doses.
Digestive comfort
Pooled data from three small placebo-controlled trials in adults with irritable bowel syndrome showed greater symptom improvement with oral aloe than placebo at 1 month, though not over 3 months, and none of the three trials beat placebo on its own main measure. A later 160-person trial found no difference between an aloe extract and a fiber control. The support for this use is weak.
Mechanism of action
Gel polysaccharides and glucose handling (proposed)
Reviewers of the blood sugar trials proposed that high molecular weight polysaccharides or phytosterols from aloe gel may enhance glucose uptake into cells and reduce cholesterol absorption from the gut, and rat studies suggest better insulin sensitivity. These are proposed explanations, not mechanisms shown in people.
Latex anthranoids as a stimulant laxative
Aloin and related glycosides in the latex pass to the large intestine, where gut bacteria convert them to aloe-emodin-9-anthrone. This speeds colonic transit and draws water and electrolytes into the colon, so a bowel movement follows 6 to 12 hours after a dose.
Aloe-emodin and the genotoxicity concern
Gut bacteria convert aloin to aloe-emodin. IARC reports that aloe preparations, acemannan and aloin A were not genotoxic in standard tests while aloe-emodin was, and suggests that the rat intestinal tumors are a consequence of this conversion. Activated carbon treatment (decolorization) removes most anthraquinones from whole leaf extract.
Clinical trials
Systematic review and meta-analysis of 5 randomized controlled trials (415 participants) of oral aloe in prediabetes and early untreated type 2 diabetes, using 0.2 to 2.8 g a day of powder or capsules, or juice, for 6 to 12 weeks. The authors judged the trials few and of poor quality and called the results inconclusive. (Zhang et al. 2016, Nutrients)
415 adults with prediabetes or early untreated diabetes
Compared with controls, aloe lowered fasting blood glucose by about 30 mg/dL and HbA1c by 0.41 percentage points, lowered triglycerides, total cholesterol and LDL cholesterol, and raised HDL cholesterol. Only one adverse event was reported across the trials, and the authors noted that safety data were limited.
Double-blind randomized placebo-controlled trial in Iran: 72 adults aged 35 to 65 with prediabetes took capsules of aloe vera extract, 300 mg or 500 mg twice daily, or a cellulose placebo for 8 weeks. The plant part used was not stated, and the authors declared no competing interests. (Alinejad-Mofrad et al. 2015, J Diabetes Metab Disord)
72 adults with prediabetes
Compared with placebo, both aloe groups had lower fasting blood glucose at weeks 4 and 8 and lower HbA1c at week 8. Total cholesterol, LDL cholesterol and triglycerides fell more than placebo only in the 500 mg group, and HDL cholesterol was higher than placebo in both groups at week 8. No adverse effects were reported.
Systematic review and meta-analysis of three randomized placebo-controlled trials in irritable bowel syndrome (151 patients); each of the three trials has its own card on this page. The authors noted a high dropout rate and possible carry-over in the crossover trial. (Hong et al. 2018, J Neurogastroenterol Motil)
151 adults with irritable bowel syndrome
Pooled, aloe improved symptom scores more than placebo (standardized mean difference 0.41) and more patients responded (risk ratio 1.69, from two trials). The benefit was significant at 1 month but not over 3 months. No aloe-related adverse events were found. None of the three trials showed a significant difference on its own main outcome.
Randomized double-blind placebo-controlled pilot trial in Sweden in irritable bowel syndrome (Rome III): AVH200 aloe extract effervescent tablets, 250 mg twice daily, or a vitamin C placebo for 4 weeks; the primary outcome was the responder rate. The maker, Calmino group AB, supplied the tablets, and academic grants funded the study. (Størsrud et al. 2015, J Gastrointestin Liver Dis)
68 adult outpatients
The primary outcome was not met: 55% responded on aloe versus 31% on placebo (p=0.09). Overall symptom severity fell within the aloe group, but the difference between groups was not significant (p=0.10). No serious adverse events occurred.
Randomized double-blind placebo-controlled trial in London of aloe vera in secondary care patients with irritable bowel syndrome that had not responded to earlier treatment; symptoms were assessed at 1 and 3 months, and 49 completed 1 month. (Davis et al. 2006, Int J Clin Pract)
58 adult hospital outpatients
11 of 31 patients on aloe (35%) and 6 of 27 on placebo (22%) responded at 1 month, a difference that was not significant (p=0.763). The authors found no evidence of benefit; a trend in one symptom subgroup (p=0.07) was not significant.
Multicenter randomized double-blind placebo-controlled crossover trial in Wales in irritable bowel syndrome: 60 mL of an aloe vera gel drink or placebo twice daily for 5 months in each period, with a 2-week washout between. Forever Living Products supplied the aloe free of charge and one author was affiliated with the company; a charity funded the study. (Hutchings et al. 2011, ISRN Gastroenterol)
110 adults randomized, 47 completed both periods
There was no difference between aloe and placebo in quality of life on any of the four questionnaires used. The authors noted that the many dropouts may have left the trial too small to detect a difference.
Randomized double-blind controlled trial in Sweden in irritable bowel syndrome (all subtypes, Rome III); the control was inulin, a fiber, rather than an inert placebo, and the main measure was the IBS Symptom Severity Score. Three authors were affiliated with Calmino Group AB, which makes the extract. (Ahluwalia et al. 2020, Neurogastroenterol Motil)
160 adults who completed the trial
Symptom severity fell in both groups with no difference between them (p=0.62), and responder rates were similar (39% on aloe, 45% on control). Fecal bacteria and metabolite profiles differed between aloe responders and non-responders.