Studies with rats showed that animals the consumption of foods or fluids containing non-nutritive sweeteners was associated with increases in food intake, body weight gain, and body fat accumulation, compared to consumption of foods and fluids sweetened with glucose.
Susan Swithers, Ashley Martin, and Terry Davidson from Purdue University’s Department of Psychological Sciences report their findings in the journal Physiology & Behavior.
“The research reported here provides an answer to the question ‘Can consuming non-nutritively-sweetened foods or fluids promote increased energy intake and body weight gain compared to sugar-sweetened foods and fluids?’” wrote the researchers. “In principle, the answer clearly seems to be yes.”
Of mice and men
Commenting on whether their results with rats are applicable to the “much more complex and uncontrolled human food environment”, the researchers noted that it was “plausible, if not probable”, that both humans and animals relate sensory properties of food to the nutritive payload after eating in order to maintain energy levels.
Energy regulation may also be disrupted when sweetened foods do not translate into calories, they said.
“Thus, it is conceivable that just as exposure to non-predictive sweet taste-calorie relationships in the laboratory promotes increased intake, body weight and body adiposity in rats, the widespread use of non-caloric sweeteners by humans outside of the laboratory may have similar effects on the predictive validity of sweet tastes and ultimately on the ability of humans to control their intake and body weight,” said the researchers.
Extensive use
The study once again focuses attention on the use of sweeteners in foods and beverages. The use of sweeteners in food and beverage products is widespread and has gathered yet more pace as food firms seek to deliver healthier products, with less sugar, to consumers. According to Leatherhead International, the global market for sweeteners was worth US$1.83bn in 2007.
Although all the sweeteners used in foods have been approved and are deemed safe by the food safety authorities, internet forums, newspaper reports and some scientific literature continue to garner suspicion.
The new study looked at the effects of saccharin, the most extensively used sweetener in the world, when fed to rats in yoghurt. Two groups of animals were used: Both groups received 30 g of plain unsweetened yogurt providing 0.6 kcal per gram on some days and 30 g of either a yogurt sweetened with 20 per cent glucose, providing 1.2 kcal per gram, or a yogurt sweetened with 0.3 per cent saccharin on the other days, for five weeks.
Results showed that animals in the saccharin group consumed an average of about 50 calories per week more, gained about 10 grams more weight, and had significantly higher body fat levels, compared to the rats in the glucose group.
“Our research provided evidence consistent with the hypothesis that these effects of consuming saccharin may be associated with a decrement in the ability of sweet taste to evoke thermic responses, and perhaps other physiological, cephalic phase, reflexes that are thought to help maintain energy balance,” wrote the researchers.
“Thus, the claim that there is no viable mechanistic explanation of how intake of non-nutritive sweeteners could promote weight gain can be repudiated,” they concluded.
Source: Physiology & Behavior
Published online, doi: 10.1016/j.physbeh.2009.12.021
“High-intensity sweeteners and energy balance”
Authors: S.E. Swithers, A.A. Martin, T.L. Davidson
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Readers' response
"This study uses 0.3 per cent of saccharinem which means 160 grams equivalent of sucrose/glucose in a 180 grams serving of yogurt, whereas 20 per cent of glucose means only 36 grams in a 180 grams serving. Maybe the rats simply loved the very, very sweet, saccharine version and ate more of it.
Humans certainly would not. So much saccharine, they could not bear, tastewise."
- Hans Heezen, SWEETCONSULT, Switzerland
"This study again repeats the problem of their previous studies. I contacted the authors after their last study published with similar conclusions asking "why saccharin". Their answer was that the rats really like the taste of saccharin (more so than nutritive sweeteners) so they use it so that they can get rats to consume the product. Then they conclude that "non-nutritive sweeteners" boost energy consumption. Huh? The conclusion is that rats like saccharin"
- Dr Carolyn Merkel, Mariner Analytical LLC, USA
"The claims made in this rat study do not bear scrutiny. There is an extensive body of science based on well-conducted human trials that demonstrates that food and drinks with low calorie sweeteners help people to control their weight. Suggesting that low calorie sweeteners can cause people to gain weight is scientifically and physiologically implausible.
Given the serious consequences of overweight and obesity, foods and drinks with low calorie sweeteners make an important contribution to public health."
The International Sweeteners Association (ISA).