Stevia rebaudiana is an herb used as a natural alternative to artificial sweeteners. Stevia is classified as a supplement, not a food additive, although several large beverage manufacturers are seeking to have it re-classified for that purpose. Stevia is sold primarily as a liquid extract, powder or tablets. It is much sweeter than sugar, and can be bitter if used in large quantities.
Adverse Reactions
Although individual cases of mild bloating and nausea have been reported, there are no reports of serious adverse reactions or toxicity when using stevia. If you are allergic to plants in the daisy family (Asteraceae compositae), you could have an allergic reaction to stevia, although none have been reported.
Hypertension
In 2003, researchers reported the results of a two-year study of men with hypertension (high blood pressure) in the journal "Clinical Therapeutics." Stevioside, a sweetening chemical contained in stevia, significantly lowered blood pressure when compared to a placebo; quality of life was also improved, and there were no negative side effects noted by researchers. However, stevia does not seem to have a blood pressure-lowering effect in people who have normal or low-normal blood pressure, according to a four-week study of 100 people reported in "Food and Chemical Toxicology" in 2008. If you have hypertension and are taking anti-hypertensive medications while using stevia, monitor your blood pressure closely.
Interaction With Lithium
Stevia can cause increased levels of lithium in those who take the drug. Stevia seems to have a diuretic effect in this situation. If you are taking lithium, talk with your doctor before using stevia or products sweetened with stevia.
Insulin Sensitivity and Blood Glucose
Stevioside increased insulin sensitivity in animals who were insulin resistant and fed a high fructose diet, according to study results published in 2005 in "Hormone and Metabolic Research." Stevioside also shortened the time it took for the animals to respond to medications administered to lower blood sugar levels, including oral anti-diabetic agents and insulin. Stevia does not seem to lower blood sugar in people with normal levels, only in individuals with elevated blood sugar levels. If you are taking oral anti-diabetic medications or insulin while using stevia, monitor your blood sugar levels closely to avoid hypoglycemia.
Other Side Effects
Researchers at Nihon University in Japan reported in 2002 that stevia inhibited tumor growth in laboratory studies. Researchers at Mahidol University in Thailand reported in 2006 that stevia inhibited inflammation in laboratory studies. Neither study has been reproduced in humans to date (2009). Stevia may be effective in preventing cavities (dental caries).
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