Stevia rebaudiana Bertoni
Stevia is a food sweetener that has been used in countries such as Brazil and Japan for decades. The sweetener comes from the stevia plant—a small, shrubby perennial that bears small white flowers. It grows in Paraguay, Brazil, Central America, some Middle Eastern countries, Southeast Asia, and China. There are more than 300 species of stevia, which be longs to the family Asteraceae/Compositae.
In comparison to other sweeteners, stevia is 200 to 300 times sweeter than sugar, while aspartame, also known as Equal, is 200 times sweeter than sugar and sucralose, also known as Splenda, is 600 times sweeter than sugar. Stevia does not have any calories. In some Asian countries, stevia is used in foods such as soy sauce, pickled products, or dried seafood to diminish the salty taste.
In the United States, stevia is available as a dietary supplement and sweetener. However, there are concerns about stevia’s ability to cause genetic mutations. Although stevia is widely used in Asia and many Latin American countries, the regulatory bodies in other countries have chosen not to approve stevia as a food, and some have placed limits on the amount that should be consumed.
USES
Stevia has been used to treat diabetes and high blood pressure and to improve heart function. However, stevia has not been studied long term in diabetes. The safety of taking stevia for long periods of time is unknown.
DOSE
Studies of stevia have used inconsistent doses, although in blood pressure studies, patients have been given doses of 750–1,500 mg a day.
STUDIES
Two small studies have addressed stevia’s impact on blood glucose. One was in patients with diabetes and the other was in patients without diabetes.
• One study evaluated stevia or a placebo (dummy pill) given with a test meal to 12 patients with type 2 diabetes. A1C, a measure of average blood glucose over 3 months, was 7.4%. Patients were given 1 gram (g) stevia or maize starch with the meal. Blood was drawn 30 minutes before the meal and at various times for 4 hours thereafter. Stevia significantly decreased post-meal blood glucose by 18%.
• The study in 16 subjects without diabetes found that stevia significantly decreased plasma glucose levels. However, the authors did not provide actual numbers, only a figure for their results.
Stevia has also been studied for blood pressure.
• A year-long study using 250 mg stevia three times a day in people without diabetes showed a significant improvement in systolic (14 mmHg decrease) and diastolic blood pressure (12 mmHg decrease).
• A 2-year study in 162 Chinese patients with high blood pressure, but without diabetes, also showed benefits. In this well-designed study (multi-center, randomized, double- blind, placebo-controlled), the patients took 500 mg stevioside powder or a placebo three times a day for 2 years. In the stevia group, systolic blood pressure decreased significantly from 150 to 140 mmHg at the end of the study. In the placebo group, systolic pressure increased from 149 to 150 mmHg. The difference between stevia and a placebo was significant. Diastolic pressure decreased from 95 to 89 mmHg in the stevia group, whereas diastolic pressure decreased from 96 to 95 mmHg in the placebo group. The difference between the groups was significant.
SIDE EFFECTS AND DRUG INTERACTIONS
Side effects of stevia include nausea, bloating, dizziness, headache, weakness, and muscle pain. Some people also complain of a bitter aftertaste. In 2-year studies, patients did not experience adverse effects on their kidneys, liver, cholesterol, or electrolytes, such as sodium or potassium. In blood pressure studies lasting up to 2 years, 1,500 mg daily has been used safely without serious adverse effects other than upset stomach and other effects that quickly resolved.
Women of childbearing age, especially pregnant women, should avoid stevia because of the concern of decreased birth weight (based on animal studies) and the potential for genetic mutations. Because it belongs to the family of plants called Asteraceae/Compositae, stevia may cause allergies in people who are allergic to ragweed, marigolds, chrysanthemums, or daisies.
In animal studies, there have been reports of kidney problems, impaired reproductive activity, and some birth defects. However, sometimes very high doses of stevia are used in these studies. There is a concern that adding stevia to beverages such as colas could expose consumers to high doses of stevia, because consumers may drink large quantities.
In theory, stevia may cause low blood glucose when taken with other diabetes medications or extremely low blood pressure when taken with blood pressure medications. Since stevia may have some diuretic properties it may interact with lithium, a drug used to treat bipolar disorder, and result in elevated lithium concentrations, which may be harmful to people taking these medications.