Frequently asked Questions and Answers (FAQs)
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.