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Medicinal uses continued
A good deal of experimental work has been done on the effects of stevia and stevioside on cardiovascular functioning in man and animals. Some of this work was simply looking for possible toxicity, while some was investigating possible therapeutic astion. In neither case have significant properties been found. When any action at all is observed, it is almost always a slight lowering of arterial blood pressure at low and normal doses, changing to a slight rise in arterial pressure at very high doses.22 The most curious finding is a dose dependent action on heart beat, with a slight increase appearing at lower doses, changing to a mild decrease at higher doses. In neither instance is the result remarkable, and it is extremely doubtful that humans would experience any effect at normal doses.23 The long term use of stevia would probably have a cardiotonic action, that is, would produce a mild strengthening of the heart and vascular system.
The ability of stevia to inhibit the growth and reproduction of bacteria and other infectious organisms is important in at least two respects. First, it may help explain why users of stevia-enhanced products report a lower incidence of colds and flus, and second, it has fostered the invention of a number of mouthwash and tooth paste products. Research clearly shows that Streptococcus mutans, Pseudomonas aeruginos, Proteus vulgaris and other microbes do not thrive in the presence of the non-nutritive stevia constituents.24 This fact, combined with the naturally sweet flavor of the herb, makes it a suitable ingredient for mouth washes and for tooth pastes.25 The patent literature contains many applications for these kinds of stevia-based products. Stevia has even been shown to lower the incidence of dental caries.
Digestive Tonic Action.
In the literature of Brazil, stevia ranks high among the list of plants used for centuries by the "gauchos" of the southern plains to flavor the bitter medicinal preparations used by that nomadic culture. For example, it was widely used in their "mate." Through much experimentation, these people learned that stevia made a significant contribution to improved digestion, and that it improved overall gastrointestinal function.26 Likewise, since its introduction in China, stevia tea, made from either hot or cold water, is used as a low calorie, sweet-tasting tea, as an appetite stimulant, as a digestive aid, as an aid to weight management, and even for staying young.46
Effects on the Skin.
One of the properties of a liquid extract of stevia that has not yet been investigated experimentally is its apparent ability to help clear up skin problems. The Guarani and other people who have become familiar with stevia report that it is effective when applied to acne, seborrhea, dermatitis, eczema, etc. Placed directly in cuts and wounds, more rapid healing, without scarring, is observed. (This treatment may sting for a few seconds, but this is followed by a significant lowering of pain.) Smoother skin, softer to the touch is claimed to result from the frequent appllication of stevia poultices and extracts. Current FDA labelling regulations are forcing U.S. suppliers to label their stevia as something other than a sweetener; an appeal to its soothing action on the skin has been the most frequent alternative.
Effects on Reproduction.
An interesting pseudo-phenomenon arose at one time, and, sadly, still receives attention from time to time, in the popular press and even by serious scientists. It is sad because the whole thing is a hoax; if not that, it is at least a case of very badly mistaken identity. It seems that in 1968 a paper appeared that claimed that certain tribes of Indians in Paraguay (the Matto Grosso) used stevia tea as a contraceptive, with apparently very good results27 In subsequent experimental work, utilizing rats, these researchers found that the treatment was supposedly good for periods up to 2 months.
Subsequent work has repeatedly failed to replicate the 1968 study.28-31 Furthermore, at least one attempt to locate tribes in northeastern Paraguay that used stevia to control fertility failed to confirm the story. One effect on reproductive physiology that appears to be valid, but which is in need of further study before definitive conclusions can be drawn, is a healing effect on the processes underlying prostate disease.32 Just how important this finding is must await further research.
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