Stevioside is safe!
by Prof. Jan M.C. Geuns
Lab. Functional Biology, KULeuven
Stevioside, the main sweet component in the leaves of Stevia rebaudiana (Bertoni) Bertoni tastes about 300 times sweeter than sucrose (0.4% solution). As the incidence of diabetes type 2 and obesitas is sharply increasing, the last one also due to too much fat and salt intake, stevioside is a good substitute for table sugar. The yearly costs of these diseases were estimated to be 30 billion euro in Germany, 5 billion in Belgium and 300 billion USD in the USA.
This sum includes the money for drugs, for hospitalisation, amputations, eye diseases going to blindness, treatment of heart and blood circulation problems, special diets, dental care, costs of the medical staff and so on. Assuming that the European population (± 454,000,000) is in a similar bad condition as the Belgian one, the yearly costs may be estimated at about 227 billion euro! Even this might be an underestimation as it does not include social aspects and human suffering.
The advantages of stevioside as a dietary supplement (daily intake estimated to be below 200 mg) for human subjects are manifold: it is stable, non-calorific and it maintains good dental health by reducing the intake of sugar and it opens the possibility for use by diabetic and phenylketonuria patients and obese persons. High concentrations of stevioside (250 mg thrice a day up to 500 mg thrice a day) lower blood pressure of hypertensive patients. Blood biochemistry parameters including lipid and glucose showed no significant changes. No significant adverse effect was observed and a quality of life assessment showed no deteriation. No decrease of male potency was observed. Moreover, stevioside possesses a potential as treatment of type 2 diabetes. Recently it was demonstrated that oral intake of stevioside causes a clear-cut reduction in the glycaemic response to a test meal.
In Brazil, Korea, Maleysia 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 or food additive respectively 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 aglycon steviol.
In 2004 researchers of the KULeuven (Belgium) organised an international symposium on “The Safety of stevioside”. Scientists from all over the world concluded that stevioside is safe:
- the lethal dose is very high (15-20 g/kg body weight),
- only low amounts are needed for sweetening purposes,
- stevioside is not carcinogenic. On the contrary, it has been proved that stevioside reduces breast cancer in rats as well as skin cancers in animals models,
- the absorption and metabolism have been studied in human volunteers. Stevioside is not absorbed by the guts. Only bacteria of the colon degrade stevioside to steviol. Part of this is absorbed but metabolised to steviol glucuronide and excreted in the urine. No free steviol was detected in the blood, - although steviol showed a weak mutagenic activity in one very sensitive strain of a bacterium, even high concentrations of oral steviol were harmless (up to 2 g/ kg body weight)! In this respect it is very interesting that the incidence of cancers in Japan is very low, although stevioside has been used for over 25 years,
- stevioside has not any effect on male or female fertility, nor on development and state of foetuses.
The lobby against stevioside is trying to circulate rumours of effects on male fertility. Contrary to these rumours, stevioside does not influence male fertility. High concentrations of stevioside can be used for lowering blood pressure even without affecting the male potency! (as do some of the other drugs used in hypertension). The false rumours are based on a non-sense experiment with rats. In that experiment, each rat was daily force-fed extracts from about 2.668 g of dry Stevia leaves per day, i.e. 5.34 % of the body weight! This is a very large amount: 53.4 g Stevia leaves/kg BW at the start of the experiments (rats weighing about 50 g) and about 13.75 g/kg BW at the end (rats weighing about 194 g). For an adult person of 65 kg this means extracts of 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 in which only one extremely large concentration was tested, should be questioned. If we assume a steviol glycoside content of 10%, this means that the young animals received 5.3 g steviol glycosides/kg BW and the older ones about 1.3 g/kg BW.
In the sixty-third meeting of the Joint Expert Committee for Food Additives of the WHO (Jecfa; 8-17 June 2004), a temporary Allowable Daily Intake (ADI) of 2 mg/kg BW (expressed as steviol) has been accepted, a step in the right direction for the worldwide general acceptance of stevioside and related compounds. However, Jecfa asked for additional research on the effects of low and high concentrations in patients with hypo- and normotension, in insuline dependent and –independent diabetes, stability studies and a better specification of the steviol glycoside mixture. To organise this research, we urgently need 600,000 euro.
The “Proceedings of the first symposium on the “Safety of Stevioside” are available at Euprint, Parkbosstraat 3, 3001 Heverlee, Belgium. Email: firstname.lastname@example.org .