Hypertension and Stevia

Stevia is an herb that is best known as a calorie-free sweetener. Taken in high doses, it may reduce blood pressure. Stevia's active ingredients are called steviosides.

It appears that stevia lowers blood pressure by mechanisms similar to those of calcium channel blockers such as verapamil (Calan SR).⁹

Read more details about Stevia.

In a 1-year, double-blind, placebo-controlled study of 106 people with moderate hypertension (approximately 165/103), steviosides at a dose of 250 mg three times daily reduced blood pressure by approximately 10%.¹² Full benefits took months to develop. However, this study is notable for finding no benefits at all in the placebo group. This is unusual and tends to cast doubt on the results.

Benefits were also reported in a 2-year, double-blind, placebo-controlled study of 174 people with milder hypertension (average initial BP of approximately 150/95).⁷⁰ This study used twice the dose of the previous study: 500 mg three times daily. A reduction in blood pressure of approximately 6%-7% was seen in the treatment group as compared to the placebo group, beginning within 1 week and enduring throughout the entire 2 years. At the end of the study, 34% of those in the placebo group showed heart damage from high blood pressure (left ventricular hypertrophy), while only 11.5% of the stevioside group did, a difference that was statistically significant. No significant adverse effects were seen.

However, once again, no benefits at all were seen in the placebo group. This is a red flag for problems in study design. Both of these studies were performed in China, a country that has a documented history of questionable medical study results.⁷¹

Furthermore, a study by an independent set of researchers failed to replicate these findings.¹²⁹ And, another study involving people with diabetes, as well as healthy subjects, found that stevia, at a dose of 250 mg three times daily, had no significant effect on blood pressure after 3 months of treatment.¹³⁰

Furthermore, a study by an independent set of researchers failed to replicate these findings.¹²⁹ And, another study involving people with diabetes, as well as healthy subjects, found that stevia, at a dose of 250 mg three times daily, had no significant effect on blood pressure after 3 months of treatment.¹³⁰

Stevia is sold as a powder to be added to foods as needed for appropriate sweetening effects. It tastes slightly bitter if placed directly in the mouth. In liquids, though, this is generally not noticeable, and most people find the taste delightfully unique.

In the studies showing an effect on blood pressure, stevia was given as a standardized extract supplying 250-500 mg of stevioside three times daily (a dose considerably higher than any reasonable use of stevia as a sweetener).

• Practitioner of Traditional Chinese Medicine (herbalist and/or acupuncturist)
• Western herbalist
• Integrative MD

Safety Issues

Animal tests and the extensive Japanese experience with stevia suggest that this is a safe herb. ¹ Based primarily on the apparently incorrect belief that stevia has been used traditionally to prevent pregnancy, ² some researchers have expressed concern that stevia might have an antifertility effect in men or women. However, evidence from most (though not all) animal studies suggests that this is not a concern at normal doses. ^{3 4} The two studies described above in which use of very high dosages of a stevia extract led to reductions in blood pressure raise at least theoretical concerns about stevia's safety. In theory, the herb could excessively reduce blood pressure in some people. Furthermore, if stevia can reduce blood pressure, that means that it is, in some fashion, acting on the cardiovascular system.

Since sugar substitutes are meant to be consumed in essentially unlimited quantities by a very wide variety of people, the highest levels of safety standards are appropriate, and unknown effects on the heart and blood circulation are potentially worrisome. This concern is somewhat mitigated by the fact that the daily dose of stevioside used in those studies was considerably higher than is likely to be consumed if whole stevia is used for sweetening purposes. Reassurance also comes from the study that found no effect with a dose of 15 mg/kg per day.

Safety in young children, pregnant or nursing women, or those with severe liver or kidney disease has not been conclusively established. Because of the concerns raised in the previous paragraph, individuals with cardiovascular disease should use high doses of stevia extracts only under physician supervision.

1. Kinghorn AD, Soejarto DD. Current status of stevioside as a sweetening agent for human use. Econ Med Plant Res. 1985;1:22.
2. Kinghorn AD, Soejarto DD. Current status of stevioside as a sweetening agent for human use. Econ Med Plant Res. 1985;1:22.
3. Melis MS. Effects of chronic administration of Stevia rebaudiana on fertility in rats. J Ethnopharm 1999;167;157-161.
4. Oliveira-Filho RM, Uehara OA, Minetti CA, et al. Chronic administration of aqueous extract of Stevia rebaudiana (Bert.) Bertoni in rats: endocrine effects. Gen Pharmacol. 1989;20:187-191.

9. Melis, M.S. and A.R. Sainati, Effect of calcium and verapamil on renal function of rats during treatment with stevioside. J Ethnopharmacol 1991;33(3):257-62.
12. Chan P, Tomlinson B, Chen YJ, et al. A double-blind placebo-controlled study of the effectiveness and tolerability of oral stevioside in human hypertension. Br J Clin Pharmacol. 2000;50:215-220.
70. Hsieh MH, Chan P, Sue YM, et al. Efficacy and tolerability of oral stevioside in patients with mild essential hypertension: a two-year, randomized, placebo-controlled study. Clin Ther. 2003;25:2797-808.
71. Vickers A, Goyal N, Harland R, et al. Do certain countries produce only positive results? A systematic review of controlled trials. Control Clin Trials. 1998;19:159-166.
129. Vickers A, Goyal N, Harland R, et al. Do certain countries produce only positive results? A systematic review of controlled trials. Control Clin Trials. 1998;19:159-166.
130. Barriocanal LA, Palacios M, Benitez G, et al. Apparent lack of pharmacological effect of steviol glycosides used as sweeteners in humans. A pilot study of repeated exposures in some normotensive and hypotensive individuals and in Type 1 and Type 2 diabetics. Regul Toxicol Pharmacol. 2008 Mar 5.