על ידי תמי_גלילי* » 25 פברואר 2011, 16:20
In 1968 Professor Joseph Kuc, then a member of Purdue University’s department of biochemistry, performed a study on rats to see if stevia had any contraceptive effect. Undertaken with a faculty member at the University of the Republic in Montevideo, the study was prompted by a rumor that Indian women in South America used the herb for contraceptive purposes. It should be noted that researchers have been unable to duplicate the conclusions of this study.
While the results of the Kuc study might appear at first glance to bear out such rumors, closer examination raises doubts about the methods that were used, and how they apply to the typical way in which stevia is consumed. In fact, Kuc himself, although still standing by his findings of marked, relatively long-term reductions in the numbers of offspring born to female rats administered his stevia solution, acknowledges that those results aren’t necessarily applicable to human consumption.
The Kuc study involved a very high concentration — ten milliliters of a dosage administered in about 20 minutes — of a concoction derived by drying to a powder and boiling not just the leaves, but material from the stevia plant that would not ordinarily be consumed. This liquid replaced the animals’ drinking water, and was given at such a rate as to equate with a person drinking 2.5 quarts of liquid in less than half an hour.
The study also only utilized one dosage level. Typically, a biological effect (such as what Kuc reported) would be demonstrated by using a variety of doses to establish what is known as a dose-response relationship.
Kuc acknowledges that the study “absolutely needs to be redone” (just as all research, in his view, needs to be “checked and rechecked” to determine whether it “stands the test of time”). He further concedes that this finding, in itself does not constitute an important reason for keeping stevia off the U.S. market.
Kuc also notes something else: that effects in rats aren’t necessarily experienced by people — as illustrated by the apparent lack of any correlation between the results of his rat research and birth rates among regular stevia consumers. As pointed out in the Lipton petition to the FDA, “…if this reproductive effect in rats is real and can be extrapolated to humans, then one might suspect that there would be very few children in some regions of Paraguay.”
Scraping the bottom of the research barrel
A second study dealing with stevia’s supposed contraceptive effect was performed on female mice and published in a Brazilian pharmacological journal in 1988. It was later informally translated by an FDA employee familiar with Portuguese. The only problem is that, outside of the FDA, no one in the scientific community gives it credence.
The research at issue, according to one authority who analyzed it (Professor Mauro Alvarez of Brazil’s State University of Maringa Foundation) “caused surprise with regard to the lack of information about the quantities that were administered and the preparation of the infusions, because mice, due to their low body weight, cannot receive high volumes intragastrically without suffering major stress.” What’s more, the study involved a small number of test animals and was “highly susceptible to external influences,” he observed.
The same study was characterized by Mark Blumenthal, editor of Herbalgram — a newsletter published jointly by the American Botanical Council and Herb Research Foundation — as “the kind of research which FDA would never accept if a petitioner was using it (as a basis for) his or her arguments.” In his opinion, “The FDA would laugh them out of the room.”
What’s perhaps most interesting about the FDA’s citation of these two studies, however, is that what it regards as a possibly harmful effect is just as apt to be viewed as a beneficial one. As the authors of the Lipton petition put it, “One would think that this effect would make stevia extract the perfect contraceptive agent — easy to consume… and effective long-term — and would be intensely pursued by pharmaceutical companies, the World Health Organization, etc. Obviously this has not happened (or if it has, then there was no effect), which casts further doubt on the validity of the data.”
Excerpted from “The Stevia Story: A tale of incredible sweetness & intrigue, copyright 2000, by Donna Gates
In 1968 Professor Joseph Kuc, then a member of Purdue University’s department of biochemistry, performed a study on rats to see if stevia had any contraceptive effect. Undertaken with a faculty member at the University of the Republic in Montevideo, the study was prompted by a rumor that Indian women in South America used the herb for contraceptive purposes. It should be noted that researchers have been unable to duplicate the conclusions of this study.
While the results of the Kuc study might appear at first glance to bear out such rumors, closer examination raises doubts about the methods that were used, and how they apply to the typical way in which stevia is consumed. In fact, Kuc himself, although still standing by his findings of marked, relatively long-term reductions in the numbers of offspring born to female rats administered his stevia solution, acknowledges that those results aren’t necessarily applicable to human consumption.
The Kuc study involved a very high concentration — ten milliliters of a dosage administered in about 20 minutes — of a concoction derived by drying to a powder and boiling not just the leaves, but material from the stevia plant that would not ordinarily be consumed. This liquid replaced the animals’ drinking water, and was given at such a rate as to equate with a person drinking 2.5 quarts of liquid in less than half an hour.
The study also only utilized one dosage level. Typically, a biological effect (such as what Kuc reported) would be demonstrated by using a variety of doses to establish what is known as a dose-response relationship.
Kuc acknowledges that the study “absolutely needs to be redone” (just as all research, in his view, needs to be “checked and rechecked” to determine whether it “stands the test of time”). He further concedes that this finding, in itself does not constitute an important reason for keeping stevia off the U.S. market.
Kuc also notes something else: that effects in rats aren’t necessarily experienced by people — as illustrated by the apparent lack of any correlation between the results of his rat research and birth rates among regular stevia consumers. As pointed out in the Lipton petition to the FDA, “…if this reproductive effect in rats is real and can be extrapolated to humans, then one might suspect that there would be very few children in some regions of Paraguay.”
Scraping the bottom of the research barrel
A second study dealing with stevia’s supposed contraceptive effect was performed on female mice and published in a Brazilian pharmacological journal in 1988. It was later informally translated by an FDA employee familiar with Portuguese. The only problem is that, outside of the FDA, no one in the scientific community gives it credence.
The research at issue, according to one authority who analyzed it (Professor Mauro Alvarez of Brazil’s State University of Maringa Foundation) “caused surprise with regard to the lack of information about the quantities that were administered and the preparation of the infusions, because mice, due to their low body weight, cannot receive high volumes intragastrically without suffering major stress.” What’s more, the study involved a small number of test animals and was “highly susceptible to external influences,” he observed.
The same study was characterized by Mark Blumenthal, editor of Herbalgram — a newsletter published jointly by the American Botanical Council and Herb Research Foundation — as “the kind of research which FDA would never accept if a petitioner was using it (as a basis for) his or her arguments.” In his opinion, “The FDA would laugh them out of the room.”
What’s perhaps most interesting about the FDA’s citation of these two studies, however, is that what it regards as a possibly harmful effect is just as apt to be viewed as a beneficial one. As the authors of the Lipton petition put it, “One would think that this effect would make stevia extract the perfect contraceptive agent — easy to consume… and effective long-term — and would be intensely pursued by pharmaceutical companies, the World Health Organization, etc. Obviously this has not happened (or if it has, then there was no effect), which casts further doubt on the validity of the data.”
Excerpted from “The Stevia Story: A tale of incredible sweetness & intrigue, copyright 2000, by Donna Gates