Last year, in my article on sugar alternatives for Vitamin Retailer magazine, I included information on several natural sugar alternatives, including stevia. Since not much has changed since then with regard to any new natural sugar alternative entering the market, I decided to make stevia the focus of this year’s sugar alternatives article with an examination of stevia’s benefits, along with being an effective sweetening agent. The fact is, in-vitro, animal and human studies have variously demonstrated that stevia’s pharmacological activities and therapeutic benefits include antitumor and anticancer, anti-inflammatory, anti-hyperglycemic, antihypertensive, antidiarrheal, immunomodulatory, diuretic and enzyme inhibitory actions.1 In this article, I will review research on the use of stevia for its antioxidant properties, and its effects on glucose tolerance, insulin sensitivity, satiety and blood pressure.
Although I provided this background information on stevia in last year’s article, it bears repeating here. Native to subtropical and tropical regions from western North America to South America, stevia is a genus of herbs and shrubs in the sunflower family. Stevia rebaudiana, commonly known as stevia, is grown for the sweetness of its leaves. Stevia’s sweetness occurs more slowly and lasts longer duration than sugar. The limitation of stevia is that its extracts generally have a bitter aftertaste, sometimes described as licorice like. The compounds in stevia providing its sweet taste are called steviol glycosides, and provide up to 300 times the sweetness of sugar. The major steviol glycosides are stevioside and rebaudioside A (aka, RebA).2 It is important to note that whole-leaf stevia or crude stevia extracts have not had GRAS (generally recognized as safe) approval as a food additive. Rather, Sweet Green Fields, Blue California, McNeil Nutritionals, Cargill and Whole Earth Sweetner/Merisant have all received GRAS approval for concentrated rebaudioside A products derived from stevia.3
Besides its functioning as a sugar alternative, stevia may offer other health benefits. Human research indicates that stevioside (750-1,500 mg/day) may be effective in lowering blood pressure in hypertensive patients.4 Other clinical research suggests that stevioside 1,000 mg/day) might reduce postprandial glucose levels by 18 percent in people with type 2 diabetes.5 However, since the GRAS approved stevia compound is rebaudioside A, it is not clear that commercially available products will have the same effects.
Antioxidant Properties, Glucose Tolerance and Insulin Sensitivity
A study6 examining the effect of harvest time and site found that that stevia contains a high level of phenols and high antioxidant activity. As expected, stevia was found to be effective for inhibiting free radicals. The authors concluded that, “The strong antioxidant properties make very interesting the possibility of using stevia extracts to improve functional food properties.”
In another study,7 the effects of stevia on streptozotocin (a naturally occurring chemical that is particularly toxic to the insulin-producing beta cells of the pancreas in mammals)-induced diabetic rats was examined. The rats were divided into different groups, including groups fed whole stevia leaves powder or extracted stevia polyphenols. The results showed that there was a reduction of blood glucose, and an improvement in insulin levels in the stevia whole leaves powder and extracted polyphenols fed rats compared to control diabetic group. Furthermore, stevia whole leaves powder and extracted polyphenols also reduced the free radical activity (as measured by MDA concentration in liver) and improved antioxidant status through antioxidant enzymes. Glucose tolerance and insulin sensitivity were improved. In addition, stevia leaves and extracted polyphenol alleviated kidney damage caused by streptozotocin.
The glucose tolerance and insulin sensitivity benefits demonstrated by stevia in rats gives rise to the question, does stevia have similar benefits in humans? Apparently so. In one study,8 the effect of aqueous stevia extracts on a glucose tolerance test was investigated in 16 normal volunteers. Aqueous extracts of 5 grams of leaves were given at six-hour intervals for three days. Glucose tolerance tests were performed before and after each stevia administration. Results showed that stevia extract improved glucose tolerance, decreasing plasma glucose levels during the test and after overnight fasting in all volunteers.
In another study,9 12 people with type 2 diabetes received 1,000 mg/day of stevioside, a constituent of stevia, or a placebo with a test meal. Later, those that received the stevioside were given the placebo instead with the test meal, and vice-versa. In either case, blood samples were drawn at 30 minutes before and for 240 minutes after ingestion of the test meal. Results showed that, compared to control, stevioside reduced post-meal glucose levels by 18 percent (P =.013). In addition, stevioside also increased the insulinogenic index by approximately 40 percent by compared to control (P <.001). The authors concluded, “Stevioside may be advantageous in the treatment of type 2 diabetes.”
Given its benefits for glucose tolerance, one might speculate that stevia would also have benefit as part of a weight-loss program. However, some critics suggest that using stevia rather than sugar as a sweetener would simply cause the dieter to eat more calories in compensation. To test this hypothesis, a study10 was conducted in which 19 healthy lean (BMI=20.0-24.9) and 12 obese (BMI=30.0-39.9) individuals (18-50 years old) received preloads containing stevia (290 calories), aspartame (290 calories), or sucrose (493 calories) before the lunch and dinner meals. Hunger and satiety levels were reported before and after meals, and every hour throughout the afternoon. Participants provided blood samples immediately before and 20 minutes after the lunch preload. Results showed that, despite the caloric difference in preloads (290 calories vs. 493 calories), participants did not compensate by eating more at their lunch and dinner meals when they consumed stevia and aspartame versus sucrose. Self-reported hunger and satiety levels did not differ between groups. Furthermore, stevia preloads significantly reduced post-meal glucose levels compared to sucrose preloads (p<.01), and post-meal insulin levels compared to both aspartame and sucrose preloads (p<.05). This research demonstrates that stevia can indeed be used to maintain satiety while dieting, and even help modulate glucose levels in the process.
In addition to the aforementioned benefits of stevia, this alternative sweetener has also been shown to help reduce blood pressure in people with hypertension. In a multicenter, randomized, double-blind, placebo-controlled trial11 in 168 men and women (aged 20-75) with mild hypertension, the effects of 500 mg stevioside powder or placebo three times daily for two years were examined. Blood pressure was measured at monthly clinic visits; patients were also encouraged to monitor blood pressure at home using an automated device. After two years, the stevioside group had significant decreases in average systolic blood pressure (from 150 to 140 mmHg) and diastolic blood pressure (from 95 to 89 mmHg) compared to starting blood pressure (P < 0.05) and compared with placebo (P < 0.05). Based on patients’ records of self-monitored blood pressure, these effects were noted beginning approximately one week after the start of treatment and persisted throughout the study.
Another multicenter, randomized, double-blind, placebo-controlled study12 was undertaken in 106 hypertensive men and women (aged 29-75). Subjects received 250 mg stevioside or placebo three times daily. Their blood pressure was measured monthly for one year. The results were that after three months, the systolic and diastolic blood pressure of the stevioside group decreased significantly (systolic: 166.0 to 152.6mmHg; diastolic: 104.7 to 90.3 mmHg, P<0.05), and the effect persisted during the whole year.
In addition to its effectiveness as a sweetening alternative to sugar, stevia has other benefits to offer. Research has shown that stevia and its steviol glycosides have antioxidant properties, and positive effects on glucose tolerance, insulin sensitivity, satiety and blood pressure. VR
1 Chatsudthipong V, Muanprasat C. Stevioside and related compounds: therapeutic benefits beyond sweetness. Pharmacol Ther. 2009 Jan;121(1):41-54.
2 Abdullateef RA, Osman M. Studies on effects of pruning on vegetative traits in Stevia rebaudiana Bertoni (Compositae). International Journal of Biology. 2012;4(1):146-153.
3 What refined Stevia preparations have been evaluated by FDA to be used as a sweetener? U.S. Food and Drug Administration. Last updated 04/10/2014. Retrieved April 13, 2014 from www.fda.gov/AboutFDA/Transparency/Basics/ucm214865.htm.
4 Ulbricht C, Isaac R, Milkin T, et al. An evidence-based systematic review of stevia by the Natural Standard Research Collaboration. Cardiovasc Hematol Agents Med Chem. 2010 Apr;8(2):113-27.
5 Gregersen S, Jeppesen PB, Holst JJ, Hermansen K. Antihyperglycemic effects of stevioside in type 2 diabetic subjects. Metabolism 2004;53:73-6.
6 Tavarini S, Angelini LG. Stevia rebaudiana Bertoni as a source of bioactive compounds: the effect of harvest time, experimental site and crop age on steviol glycoside content and antioxidant properties. J Sci Food Agric. 2013 Jul;93(9):2121-9.
7 Shivanna N, Naika M, Khanum F, Kaul VK. Antioxidant, anti-diabetic and renal protective properties of Stevia rebaudiana. J Diabetes Complications. 2013 Mar-Apr;27(2):103-13.
8 Curi R, Alvarez M, Bazotte RB, Botion LM, Godoy JL, Bracht A. Effect of Stevia rebaudiana on glucose tolerance in normal adult humans. Braz J Med Biol Res. 1986;19(6):771-4.
9 Gregersen S, Jeppesen PB, Holst JJ, Hermansen K. Antihyperglycemic effects of stevioside in type 2 diabetic subjects. Metabolism. 2004 Jan;53(1):73-6.
10 Anton SD, Martin CK, Han H, Coulon S, Cefalu WT, Geiselman P, Williamson DA. Effects of stevia, aspartame, and sucrose on food intake, satiety, and postprandial glucose and insulin levels. Appetite. 2010 Aug;55(1):37-43.
11 Hsieh MH, Chan P, Sue YM, Liu JC, Liang TH, Huang TY, Tomlinson B, Chow MS, Kao PF, Chen YJ. Efficacy and tolerability of oral stevioside in patients with mild essential hypertension: a two-year, randomized, placebo-controlled study. Clin Ther. 2003 Nov;25(11):2797-808.
12 Chan P, Tomlinson B, Chen YJ, Liu JC, Hsieh MH, Cheng JT. A double-blind placebo-controlled study of the effectiveness and tolerability of oral stevioside in human hypertension. Br J Clin Pharmacol. 2000 Sep;50(3):215-20.