The name “stevia” commonly refers to sweeteners derived from the leaves of Stevia rebaudiana Bertoni. Long before stevia gained popularity as an alternative sweetener, Stevia rebaudiana leaves were used by indigenous South Americans to sweeten beverages and medicines. The glycosides responsible for its sweet taste were isolated in 1931 and were later incorporated into stevia-based sweeteners.
The plant’s steviol glycosides have been estimated to be 100-300 times sweeter than sugar, meaning that only a small amount is needed to impart a sweet taste. Stevia is commonly used as a sugar alternative. The use of stevia in place of sugar significantly lowers the relative caloric and carbohydrate content of food and beverages. In addition to its use as an alternative sweetener, does stevia also offer other benefits for our health?
Analysis of extracts of stevia leaves revealed the presence of the flavonoids quercetin-3-O-arabinoside, quercitrin, apigenin, apigenin-4-O-glucoside, luteolin, and kaempferol-3-O-rhamnoside. Evaluation of the extracts’ free radical scavenging capacity determined that “Stevia rebaudiana may be useful as a potential source of natural antioxidants.”1
Stevia Makes a Better Sweetener
While saccharine’s taste is perceived to be less than ideal among some people and aspartame has been recently associated with weight gain in an animal model,2 stevia could be a better option as a sugar substitute. “We found that aspartame blocks a gut enzyme called intestinal alkaline phosphatase (IAP) that we previously showed can prevent obesity, diabetes and metabolic syndrome; so we think that aspartame might not work because, even as it is substituting for sugar, it blocks the beneficial aspects of IAP,” explained Richard A. Hodin, MD, concerning the recent research conducted by his team at Massachusetts General Hospital. “Our findings regarding aspartame’s inhibition of IAP may help explain why the use of aspartame is counterproductive.”
In a study in which aspartame, stevia and sucrose were consumed before lunch and dinner, stevia significantly lowered glucose levels following meals in comparison with sucrose and reduced post-meal insulin levels compared to sucrose as well as with aspartame.3
Potential Therapeutic Effects of Stevia
In a review of stevioside and related compounds, V. Chatsudthipong and C. Muanprasat of Mahidol University from Bangkok note that “A number of studies have suggested that, beside sweetness, stevioside along with related compounds, which include rebaudioside A (second most abundant component of S. rebaudiana leaf), steviol and isosteviol (metabolic components of stevioside) may also offer therapeutic benefits, as they have anti-hyperglycemic, anti-hypertensive, anti-inflammatory, anti-tumor, anti-diarrheal, diuretic, and immunomodulatory actions.”4
Stevia and Diabetes Research
The Journal of Diabetes Complications reported a study in which rats were pretreated with diets that contained stevia whole leaf powder, polyphenols or fiber, or no stevia for a month prior to being injected with a diabetes-inducing drug (streptozotocin). Animals that received stevia leaf or polyphenols exhibited lower blood glucose and liver enzymes compared to diabetic animals pretreated with a control diet.5 Those that received stevia leaf or polyphenols also showed improvements in glucose tolerance and insulin sensitivity and did not experience kidney damage from the diabetes-inducing drug, unlike control-fed diabetic rats.
An early human study of the effects of stevia extract involved 16 healthy subjects who were given stevia extract every six hours for three days while a control group received a different solution. Glucose tolerance tests were conducted and fasting glucose levels were measured before and after the treatment period. Those who received stevia had lower plasma glucose levels during glucose tolerance testing and decreased fasting glucose levels compared with pretreatment values.6
In a cross-over study involving 12 type 2 diabetics, stevioside supplementation lowered glucose levels after a meal, suggesting a potential use in the treatment of diabetic humans.7
A review of the potential roles of stevia in treating insulin resistance and diabetes notes that, “On the whole, researchers worldwide agree on the antidiabetic effects of Stevia; but they differ on how the effects contribute towards combating this metabolic disease . . . Some assert that Stevia’s utility is due to its antioxidant properties; this is supported by analysis of the phenols that may be extracted from the plant. Stevia has a large overall proportion of phenols, up to 91 mg/g; it is proposed that these constituents extracted from the leaves are the major agents contributing towards the antihyperglycemic activities exerted by the plant. This is further supported by the fact that the leaves have a greater ability to scavenge free radicals and prevent lipid peroxidation than controls […]”8
Stevia and High Blood Pressure Research
Research in rats and dogs suggests that stevioside “is an effective antihypertensive natural product.”9 The effect appears to be stronger in experimental hypertensive animals than those with normal blood pressure.10
When tested in a randomized, double-blind, placebo-controlled trial of 106 men and women with hypertension, stevioside consumed three times per day was associated with a mean reduction in systolic blood pressure of 12 mmHg and an average diastolic reduction of 8 mmHg from baseline values after three months—a benefit that continued throughout the course of the 12 month study.11
Those who received a placebo experienced changes in blood pressure that were not significantly different than those measured at the beginning of the trial. “Stevioside was found to be a safe and effective compound in the treatment of hypertension although the amplitude of blood pressure lowering was slightly less than other antihypertensive drugs,” note Paul Chan and colleagues. “It could therefore be used as a supplementary therapy since it has already been used as a taste-modifying agent for more than two decades.”
A subsequent two year randomized, double-blind, placebo-controlled trial of stevioside in subjects with mild essential hypertension resulted in an average decline in systolic blood pressure of 10 mmHg and 6 mmHg diastolic blood pressure, improved quality of life and a lower incidence of the development of left ventricular hypertrophy compared with the placebo group at the end of the treatment period.12
In adults with normal and low-normal blood pressure, as much as 1,000 milligrams per day of rebaudioside A from stevia did not affect resting, seated, systolic, diastolic or mean arterial blood pressure or heart rate, which suggests that stevia may not lower blood pressure among those who don’t have hypertension.13
Stevia May Help Protect Teeth
Stevia has other benefits such as helping to prevent dental caries when used in place of sugar.14 In addition to helping to eliminate the acidic effect of sugar on tooth enamel, stevia helps inhibit some of the caries-causing bacteria.15
Stevia and stevioside appear to not only be nontoxic alternative sweeteners when used in moderation, but to benefit specific health conditions and help protect the teeth when used as a sugar substitute.
“Acute and subacute toxicity studies revealed a very low toxicity of Stevia and stevioside,” writes J. M. Geuns in a review published in the journal Phytochemistry.16 “The conclusion is that Stevia and stevioside are safe when used as a sweetener. It is suited for both diabetics, and phenylketonuric patients, as well as for obese persons intending to lose weight by avoiding sugar . . . No allergic reactions to it seem to exist.”
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- Giacaman RA et al. Arch Oral Biol. 2013 Sep;58(9):1116-22.
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