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High blood pressure. According to current results, stevia extracts would be useful for people with hypertension, but doubts remain. In China, 2 clinical studies of very good quality and long duration (1 year and 2 years, 750 mg and 1500 mg of steviosides per day) yielded conclusive results in patients with mild or moderate hypertension (reduction of about 7%). Despite the quality of these trials, some analysts raise the very surprising fact that no placebo effects were observed in these two studies, which casts doubt on their conclusions. In 2006, a study conducted in Brazil was inconclusive.This may be due to the very small number of subjects and the much lower dosage than the Chinese trials. However, these 3 studies clearly established the safety of taking steviosides regularly over long periods of time.
In Paraguay and the United States, tests were conducted on people with normal or slightly lower than normal blood pressure.Taking 750 mg of stevia extract per day for 3 months and 1000 mg per day for 4 weeks did not have a measurable effect on the blood pressure of participants. The author of a synthesis hypothesizes that the beneficial effect of stevia on tension would only manifest itself when it is too high.
Uncertain efficacy Blood Glucose. Small trials indicate that stevia extract has:
– increased glucose tolerance and lowered blood glucose levels in healthy subjects.
– lowered blood glucose levels after a typical meal in patients with type 2 diabetes.
– lowered blood glucose levels after a meal in healthy, thin or obese people.
Despite these promising results, better and more extensive studies will be needed before concluding on the efficacy of stevia.
These results tend to corroborate the traditional use of stevia used in South America to treat diabetes. However, they were not confirmed by 2 other trials on healthy subjects. Again, the author of a synthesis hypothesizes that the beneficial effect of stevia on blood sugar levels would only manifest itself when it is too high.
Various. Researchers are also interested in the anti-inflammatory and anti-cancer effects of stevia extracts. Only in vitro and animal data are available at the moment.
Precautions
Potentially toxic? The Japanese believe they have demonstrated the safety of stevia and standardized stevioside extract. This has enabled this country and several others in Asia and South America to authorize its use as a food additive. Stevia and stevioside-standardized extracts have been used for about 30 years in these regions of the world.However, some countries, including Canada, have not yet authorized it.
The most common reason given for this caution is that steviosides could have a negative impact on human reproduction.According to a Paraguayan ethnobotanical source, stevia is considered, at high doses, to be an abortive plant. Health authorities are also concerned about a potential carcinogenic effect. After careful analysis of all the data on these issues, the World Health Organization (WHO) concluded in 2006 that steviosides have no adverse reproductive effects and are not carcinogenic.
The safe daily intake set by Health Canada under the natural health product regulations is similar to that set elsewhere in the world at 10 mg of steviosides per kilogram of body weight. This corresponds to 700 mg per day for an adult of 70 kg. For people consuming stevia leaf powder, this is equivalent to a maximum of 50 mg/kg, or 3 500 mg for an adult of 70 kg.
Carfull
People with type 2 diabetes, hypertension or hypotension who want to take stevia should check their blood glucose or blood pressure regularly, to have their medication adjusted if necessary.
Contraindications
As a precaution, some sources recommend that pregnant and breastfeeding women avoid consuming large amounts of stevia.
Adverse effects
Stevia may cause allergies in people with allergies to plants of the Asteraceae family (daisy, dandelion, chrysanthemum, etc.), although no cases have been reported to date.
According to an animal test, stevia does not cause cavities.
Interactions
With plants or supplements
The effects of stevia could be added to those of plants or supplements that have a hypotensive or hypoglycemic action.With some kind of medication.
The effects of stevia could be added to those of hypotensive or hypoglycemic drugs.
Stevia is commercially available in two main forms.
Dried leaf powder. Its sweetening power is 10 to 15 times higher than that of sugar. It has traditionally been used to soften the taste of bitter herbal teas.
Standard extract (at least 90% steviosides). It is a water-soluble white powder. It is also available in liquid form. Its sweetening power is much higher than that of refined sugar (100 to 300 times), without any calories. It has to be used very sparingly. The websites that make the trade present conversion tables (specific to their products) that allow to adequately measure this sweetener.
Taste.
The whole leaf has a slightly bitter aftertaste that may remind of licorice. The powder extract, once mixed with a liquid, would have less aftertaste. Flavoured liquid extracts are also available (mint, vanilla, etc.).
Dr. Pierre Haddad, Professor, Department of Pharmacology, Montréal University