Benefits
Sweetness without sugar calories
Purified steviol glycosides are reported to be 200 to 400 times sweeter than table sugar, so very small amounts replace the sweetness of sugar. In a crossover trial, glucose 20 minutes after a stevia preload at lunch was lower than after a sucrose preload, and people did not make up the missing calories at lunch or dinner. This reflects taking sugar out of the food.
Glucose results at stevioside doses far above sweetener use
Two pooled analyses of randomized trials found fasting glucose about 4 mg/dL lower than with control, both rated low certainty; in one, the drop appeared at 3,342 mg a day or more, far above the amounts used to sweeten food. HbA1c did not differ in either. A single 1 g stevioside dose with a meal lowered the post-meal glucose rise in 12 adults with type 2 diabetes, while rebaudioside A trials found no change.
Blood pressure in placebo-controlled trials
A 2 year trial in adults with mild high blood pressure taking 1,500 mg of stevioside a day reported lower blood pressure than placebo. Other trials found no change: 750 mg of stevioside a day for 3 months, and 1,000 mg of rebaudioside A a day for 16 weeks. A pooled analysis of 9 trials found no significant change in systolic pressure, a small drop in diastolic pressure, and no effect for rebaudioside A.
Gut bacteria shifts in a two-week trial
In a randomized trial of 120 healthy adults, two weeks of stevia sachets at doses below the acceptable daily intake changed the makeup of stool and mouth bacteria. In the same trial, significant worsening of the glucose response was reported for saccharin and sucralose only. The authors called for further study of what these changes mean clinically.
WHO guidance on sweeteners and weight control
The World Health Organization recommends against using non-sugar sweeteners, naming stevia and stevia derivatives, to control body weight or reduce the risk of noncommunicable diseases. Its review found no long-term benefit for body fat and possible links with type 2 diabetes, cardiovascular disease and mortality in adults. The recommendation is conditional and excludes people with pre-existing diabetes.
Dental plaque acidity compared with sugar
In a small randomized study, 20 volunteers rinsed with 10% solutions of stevioside, rebaudioside A or sucrose. Plaque pH fell lower after sucrose than after either stevia extract from 5 to 30 minutes, and in lab tests sucrose supported more Streptococcus mutans biofilm. The authors called the extracts nonacidogenic; tooth decay itself was not measured.
Forms and regulatory status
FDA has not questioned GRAS conclusions for high-purity (at least 95%) steviol glycosides under their notified uses; whole stevia leaf and crude stevia extracts are not considered GRAS and may not be imported as sweeteners. The acceptable daily intake is 4 mg per kg of body weight per day as steviol equivalents, and EFSA found insufficient grounds to raise it.
Mechanism of action
Sweet and bitter taste differ between glycosides
Steviol glycosides differ in how fast their sweetness appears and fades and in how bitter they taste. In taste panel testing, rebaudioside M and rebaudioside D tasted sweet sooner, left less aftertaste and were nearly free of bitterness, while stevioside and rubusoside had an immediate bitter taste and a lingering aftertaste.
Breakdown by gut bacteria
Intestinal bacteria remove the sugar units from rebaudioside A, releasing steviol, which is absorbed and converted to steviol glucuronide. In adults given 3 g of rebaudioside A, some intact rebaudioside A appeared in blood within an hour, and steviol and steviol glucuronide peaked at about 19.5 hours.
Interaction with the gut microbiome
Because intestinal bacteria break steviol glycosides down, these sweeteners meet the gut microbial community directly. In a two-week human trial, stevia changed the makeup of stool and mouth bacteria as a group, and the health meaning of that shift has not been established.
Clinical trials
Acute paired crossover study; a standard test meal was given with 1 g of stevioside or 1 g of maize starch as control. (Gregersen et al. 2004, Metabolism)
12 adults with type 2 diabetes
Compared with maize starch, stevioside lowered the incremental area under the post-meal glucose curve by 18% (P = 0.013) and raised the insulinogenic index by about 40%. Insulin, GLP-1 and GIP areas under the curve did not change significantly. This was a single dose with a single meal.
Randomized, placebo-controlled trial of 1,000 mg rebaudioside A a day (n=60) versus placebo (n=62) for 16 weeks. (Maki et al. 2008, Food Chem Toxicol)
Men and women aged 33 to 75 with type 2 diabetes
Change in HbA1c did not differ between rebaudioside A (0.11%) and placebo (0.09%; p=0.355). Changes in fasting glucose, insulin, C-peptide and fasting lipids did not differ either, blood pressure was not altered, and hypoglycemic episodes showed no excess versus placebo.
Randomized, double-blind, placebo-controlled study in three groups given stevioside 250 mg three times daily or placebo for 3 months, in Paraguay. (Barriocanal et al. 2008, Regul Toxicol Pharmacol)
Adults with type 1 diabetes, adults with type 2 diabetes, and adults without diabetes with normal or low-normal blood pressure
After treatment, systolic and diastolic blood pressure, glucose and HbA1c in the stevioside groups did not differ significantly from baseline, and no side effects were seen. The authors concluded that steviol glycosides taken as a sweetener showed no pharmacological effect.
Randomized, placebo-controlled, open-label, two-way crossover trial; oral glucose tolerance test 19 hours after 3 g of rebaudioside A or placebo; registered as NCT03510624. (Simoens et al. 2022, Eur J Drug Metab Pharmacokinet)
30 adults with type 2 diabetes on metformin or no therapy, aged about 64, mostly men
The glucose area under the curve over the first 2 hours did not differ from placebo (difference -0.7 h·mg/dL, P = 0.95), and insulin and C-peptide were also comparable. Intact rebaudioside A appeared in plasma within 1 hour, and steviol and steviol glucuronide peaked at about 19.5 hours.
Crossover design with three test days; preloads before lunch and dinner sweetened with stevia (290 kcal), aspartame (290 kcal) or sucrose (493 kcal), in balanced order. (Anton et al. 2010, Appetite)
19 lean and 12 obese adults aged 18 to 50
Glucose 20 minutes after the lunch preload was lower with stevia than with sucrose (p<.01), and insulin was lower than with both aspartame and sucrose (p<.05). Participants did not eat more at lunch or dinner to make up the calories, and hunger and fullness ratings did not differ between conditions.
Randomized controlled trial of saccharin, sucralose, aspartame or stevia sachets for 2 weeks at doses below the acceptable daily intake, versus controls given the glucose vehicle or nothing, plus transfer of participants' microbiomes into germ-free mice. (Suez et al. 2022, Cell)
120 healthy adults
As groups, each sweetener, stevia included, altered stool and oral bacteria and the blood metabolome. Significant impairment of glycemic responses was reported for saccharin and sucralose only. Mice given microbiomes from top and bottom responders showed glycemic responses largely reflecting their human donors.
Multicenter, randomized, double-blind, placebo-controlled trial; capsules of 500 mg stevioside or placebo three times daily for 2 years. (Hsieh et al. 2003, Clin Ther)
168 Chinese men and women aged 20 to 75 with mild essential hypertension who completed the trial
After 2 years, systolic pressure fell from 150 to 140 mm Hg and diastolic pressure from 95 to 89 mm Hg in the stevioside group, significantly more than with placebo (P < 0.05). Body mass index and laboratory tests did not change, and adverse effects did not differ between groups.