1) Is Stevia safe for diabetics?
Yes, Stevia and stevioside used as a sweetener are absolutely safe
(Boeck-Haebisch, 1992). The chronic study by Chan et al. (2000) with
human volunteers has demonstrated that blood biochemical parameters were
not altered by 250 mg stevioside thrice a day for 1 year.
2) Are the sugar moieties of stevioside safe for diabetics?
Stevioside, the main sweet component of Stevia, is about 300 times
sweeter than table sugar. Therefore, only small amounts need to be used
for sweetening purposes. It is not taken up by the intestines and is not
metabolised by enzymes of the gastro-intestinal tract as the sugar
bonds in stevioside are b-glucosidic bonds. However, it is degraded to
steviol and sugar moieties by bacteria of the human colon. To substitute
for the total amount of added sugar in the food (± 131 g per person per
day in Belgium) less than 400 mg stevioside are required per day. This
means that in the colon only about 240 mg of glucose is released from
the 400 mg stevioside. It can be estimated that about 1/3 of this
glucose is metabolised by the bacteria of the colon, 1/3 is excreted and
about 1/3 is taken up (± 80 mg) which of course is a neglectible amount
of glucose. See also FAQ about steviol.
3) Is stevioside carcinogenic?
NO. Stevioside is not taken up by the intestines and is not metabolised
by enzymes of the gastro-intestinal tract. However, it is degraded to
steviol and sugar moieties by bacteria of the human colon. A weak
mutagenic effect of steviol (only 90 % purity) in one sensitive
Salmonella typhimurium TM 677 strain has been demonstrated but this does
not mean that stevioside used as a sweetener should be carcinogenic in
se, even if the stevioside is transformed to steviol by bacteria in the
colon! The activity of steviol in Salmonella typhimurium TM677 was very
low and was only about 1/3000 of that of 3,4-benzopyrene, and that of
steviol methyl ester 8,13 lactone was 1/24500 of that of furylfuramide
(Terai et al., 2002). Although a weak activity of steviol and some of
its derivatives was found in the very sensitive S. typhimurium TM677
strain, the authors concluded that the daily use of stevioside as a
sweetener is safe. Moreover, the presence in the blood of the chemically
synthesised steviol derivatives after feeding stevioside is not proven
at all. Very high doses of steviol (90% purity) intubated to hamsters (4
g/kg bw), rats and mice (8 g/kg BW) did not induce micronucleus in bone
marrow erythrocytes of both male and female animals. However, these
doses showed some cytotoxic effect to the female, but not to the male of
all treated animal species (Temcharoen et al., 2000). It is not
excluded that the toxicity is due to the 10% impurities present.
The safety of oral stevioside in relation to carcinogenic activity is
evidenced by the work of Yamada et al. (1985), Xili et al. (1992),
Toyoda et al. (1997) and Hagiwara et al. (1984) with rats. Very
significant inhibitory effects of stevioside were reported on tumor
promotion by 12-O-tetradecanoylphorbol-13-acetate in carcinogenesis in
mouse skin (Yasukawa et al., 2002). Stevioside exhibited significant
inhibitory effects on the two-stage mouse skin carcinogenesis in vivo
induced by 7,12-dimethylbenz[a]anthracene (DMBA) and
12-O-tetradecanoylphorbol-13-acetate (TPA). Stevioside also inhibited
mouse skin carcinogenesis initiated by peroxinitrite (Konoshima and
Takasaki, 2002). The authors concluded that stevioside might be a
valuable natural sweetener as a chemopreventive agent against chemical
carcinogenesis. In 1999 the JECFA clearly stated: "Stevioside has a very
low acute oral toxicity. Oral administration of stevioside at a dietary
concentration of 2.5% to rats for two years, equal to 970 and 1100 mg
kg-1 BW per day in males and females, respectively, had no significant
effect. Reduced body-weight gain and survival rate were observed at a
dietary concentration of 5% stevioside. There was no indication of
carcinogenic potential in a long-term study..."(WHO, 1999). Moreover,
there have never appeared reports proving that the use of Stevia or
stevioside enhances the number of cancers in populations, even after a
very long time of use (eg. Paraguay: more than 500 years, Japan: more
than 25 years, South-Korea: 16 years, Brazil: 13 years, China: 12 years
or the USA: since 1995 admitted as a dietary supplement).
4) How much steviol will be taken up by the colon?
If all of the added sugar (131 g/day) is substituted for by stevioside,
which is nearly impossible, then about 400 mg stevioside is required per
day. Degradation in the colon gives about 160 mg steviol. About 90 % of
the steviol formed is excreted with the faeces. Small amounts of
steviol are taken up by the colon and conjugated to be excreted in the
urine. In hamsters fed 250 mg steviol/kg body weight, a free steviol
concentration of about 102 µg/ml plasma was without harmful effects. In
humans no free steviol could be detected in plasma after oral
administration of 750 mg stevioside per person per day (± 12 mg/kg bw).
The maximal peak concentration of conjugated steviol was around 20
µg/ml, i.e. far below the values found safe for hamsters. As less than
400 mg stevioside will be used per day, this value will be rather below
10 µg/ml. The conjugated steviol derivatives are excreted into the
urine.
5) Is Stevia safe for phenylketonuria (PKU) patients?
Yes, Stevia and stevioside are absolutely safe as the chemical structure
of stevioside is a diterpene glycoside that is totally different from
aspartame.
6) Stevia and Blood Pressure
In a study with humans, stevioside (250 mg thrice a day) was
administered for 1 year to 60 hypertensive volunteers (Chan et al.,
2000). After 3 months the systolic and diastolic blood pressure
significantly decreased and the effect persisted during the whole year.
Blood biochemistry parameters including lipid and glucose showed no
significant changes. No significant adverse effect was observed and
quality of life assessment showed no detoriation. The authors concluded
that stevioside is a well tolerated and effective compound that may be
considered as an alternative or supplementary therapy for patients with
hypertension. Although blood pressure was lowered, no effects on male
potency were observed, a characteristic that improves quality of life!
In the treated group, the average blood pressure at the beginning of the
study was about 166/102. By the end of the study, this had fallen to
153/90. In contrast, no significant reductions were seen in the placebo
group. Liu et al. (2003) reported that the underlying mechanism of the
hypotensive effect of administered stevioside in dogs (200 mg/kg BW) was
due to inhibition of Ca2+ influx from extra-cellular fluid.
7) Is it true that Stevia or stevioside influence reproduction?
Not at all! The results of a decrease of live birth rate in rats (Planas
and Kuc, 1968) by Stevia decoctions were refuted by Shiotsu (1996) who
did more reliable experiments with many more animals using methods as
similar as possible to the methods used by Planas and Kuc. No effect on
general condition, body weight, water consumption, live birth rate or
litter size was found. No effects of stevioside were found on fertility
or reproduction in mice, rats or hamsters (ref.: see toxicological
studies) .
Whereas Melis (1999) suggested a possible decrease of the fertility of
male rats by a very high dose of Stevia extract, Oliveira-Filho et al.
(1989) who administered extracts with similar stevioside content stated
that there is certainly not an effect on male fertility. It is not sure
that the observed effects were due to the stevioside present in the
extract. It should also be mentioned that the used extract
concentrations were extremely high, at the start of the experiments even
5.34 % of the body weight (or around 5.3 g stevioside/kg bw). For an
adult person of 65 kg this means 3.47 kg of dry Stevia leaves or about
34.7 kg fresh leaves/day, i.e. more than 50% of the body weight! The
significance of such experiments where only one extremely high
concentration was tested, should be questioned. Melis' results are also
in contradiction with those of a huge number of other researchers, who
could not reveal any effect on fertility of male or female animals.
8) How much Stevia or stevioside may be consumed per day?
An acceptable daily intake (ADI) of 7.9 mg stevioside/kg BW was
calculated (Xili et al., 1992). However, this ADI should be considered
as a minimum value as the authors did not test concentrations of
stevioside higher than 793 mg/kg BW. From various chronic toxicity
studies an ADI of 20 mg/kg BW can be deduced (safety factor 100). Even
an ADI of 7.9 mg/kg BW means that a person of 65 kg may consume 513 mg
pure stevioside per day. For substituting all the added sugar in the
food (about 131 g/day), which is nearly impossible, less than 436 mg
stevioside are required. This amounts equals about 4.36 g dried Stevia
leaves (10% sweetener content).
9) How much dried Stevia leaves or how much stevioside should be used for sweetening purposes?
All depends upon the sweetener contents of the dried Stevia leaves. This
may vary between 6 and 15 % of the dry weight. Therefore, the dried
leaves are between 18 and 45 times sweeter than sugar. This means that
100 g of dry leaves (6% stevioside) correspond to 1800 g sugar or to
4500 g sugar (15% in the leaves).
Pure stevioside is only used in the food industry and is not for sale in
shops. It is always mixed with other compounds to dilute the extreme
sweetness and to facilitate the weighing in the kitchen. Depending upon
how much bulk compounds are added the sweetness of the mixture varies
and you should try it out yourself.
The most frequent mistake people make with Stevia or stevioside is
measuring out too much. Very tiny amounts of the powder can greatly
sweeten. It's easy to add too much Stevia, which overwhelms the taste
buds. It is a challenge to find the right amount of Stevia to use
because it is so highly concentrated.
Stevia comes in many forms: (The sweetness varies with each form.)
- liquid concentrate, easy to measure in drops (slight licorice flavor)
- white powdered extract, non-licorice flavor (the form primarily used in Japan)
- it is sometimes blended with a non-sweet filler called maltodextrin.
- fresh Stevia leaves - extremely sweet taste with a strong licorice flavor
- dried leaf, finely powdered (licorice flavor)
10) How many calories are in Stevia extract?
Virtually none. Stevia extracts are considered to have zero calories,
zero carbohydrates, zero sugar, zero fat and zero cholesterol.
11) Can Stevia extract replace sugar in the diet?
In the first place it has to be said that the food industry adds too
large amounts of sugar to our food. This added sugar is virtually devoid
of nutritional benefits and, at best, represents empty calories in the
diet. We really do not need this added sugar in the food. We are
supposed to eat fresh fruit and vegetables daily and these contain
enough sugars for our body. Stevia is much sweeter than sugar and has
none of sugar's unhealthy drawbacks. In case of hypoglycemia, Stevia or
stevioside are of course unable to substitute for sugar. Consult your
physician.
12) What about Stevia or stevioside and dental health?
From experiments with albino Sprague-Dawley rats Das et al. (1992)
concluded that neither stevioside nor rebaudioside A is cariogenic
(cavity causing).
Although rather high concentrations of stevioside and Stevia extracts
were shown to reduce the growth of some bacteria, the concentrations
used for sweetening purposes are rather low. Therefore, the benificial
effect of the use of stevioside would rather be due to the substitution
of sucrose in the food by a non-cariogenic substance.
Moreover, stevioside is both fluoride compatible and significantly
inhibits the development of plaque, thus Stevia may actually help to
prevent cavities.
13) Can Stevia or stevioside be used in cooking and baking?
Absolutely! The melting point of stevioside is 198 °C without
decomposition or browning. It is extremely heat stable in a variety of
everyday cooking and baking situations, compatible with dairy products
and with acidic fruits such as strawberries, oranges, limes and
pineapples. Moreover, it is pH stable, non-fermentable and does not
darken upon cooking and therefore it has a wide range of applications in
food products.
14) What is the composition of a Stevia extract?
The four major steviol glycosides are: stevioside, rebaudioside A,
rebaudioside C and dulcoside A. It has long been known that rebaudioside
A has the best sensory properties (sweetest, least bitter) of the four
major steviol glycosides. On the whole plant level, steviol glycosides
tend to accumulate in tissues as they age, so that older lower leaves
have more sweetener than younger upper leaves. Since chloroplasts are
important in precursor synthesis, those tissues devoid of chlorophyll,
like roots and lower stems, contain no or trace amounts of glycosides.
Once flowering is initiated glycoside concentrations in the leaves begin
to decline.
15) How to prepare a Stevia Extract?
A liquid extract can be made from fresh or from dried and ground Stevia
leaves. Simply combine a measured portion of Stevia leaves or herbal
powder with pure alcohol (Brand, or Scotch will also do) and let the
mixture sit for 24 hours. Filter the liquid from the leaves or powder
residue (eg. using a coffee filter) and dilute to taste using pure
water. Note that the alcohol content can be reduced by slowly heating
the extract and allowing the alcohol to evaporate off. A pure water
extract can be similarly prepared, but will not extract quite as much of
the sweet glycosides as will the alcohol. Each liquid extract can be
cooked down and concentrated into a syrup.
16) What is the legal status of Stevia and stevioside?
Both the Stevia plant, its extracts, and stevioside have been used for
several years as a sweetener in South America, Asia, Japan, China, and
in different countries of the EU. In Brazil, Korea and Japan Stevia
leaves, stevioside and highly refined extracts are officially used as a
low-calorie sweetener. In the USA, powdered Stevia leaves and refined
extracts from the leaves have been used as a dietary supplement since
1995. In 2000, the European Commission refused to accept Stevia or
stevioside as a novel food because of a lack of critical scientific
reports on Stevia and the discrepancies between cited studies with
respect to possible toxicological effects of stevioside and especially
its aglycone steviol (Kinghorn, 2002; Geuns, unpublished). The
advantages of stevioside as a dietary supplement for human subjects are
manifold: it is stable, it is non-calorific, it helps maintain good
dental health by reducing the intake of sugar and opens the possibility
for use by diabetic and phenylketonuria patients and obese persons.
Since 2005 Stevia and its extracts are approved as an additive in animal feed in Europe.
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