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More evidence that artificial sweeteners don't help weight loss

Posted Sep 12 2008 12:09pm
Posted on 11 February 2008

When it comes to healthy living, my tendency is to favour as natural a course as possible. The word ‘natural’ means different things to different people, but in the context of our diet I take it to mean food that is close as possible to the way it found in nature. This does not guarantee that a food will be healthy, of course. But common sense dictates that natural foods will be more suitable for our physiology than those that are processed, chemically manipulated and loaded with extraneous additives.

Not everyone agrees with this point of view, of course. Some would have us believe that unbelievably unnatural foods are good for us. An example of this is margarine and it’s supporters who enthusiastically promote this plastic and chemicalised food even though this position isn’t supported by the science.

Another example of how a novel, highly processed food can be spun as something healthy concerns the artificial sweeteners including saccharin and aspartame (NutraSweet, Canderel, Equal). The promise with these low-calorie sweeteners is that although they are intensely sweet, they are virtually devoid of calories, which makes them the ‘obvious’ preferred choice to sugar for those wanting to maintain a healthy weight.

Before we get on to the issue of weight, the first question we should ask about a food is ‘is it safe’? I mean, drinking diesel might be an effective aid to weight loss, but that does not make it a good nor healthy thing to do. Actually, there is considerable evidence that artificial sweeteners can be toxic to health.

Perhaps the most controversial of all artificial sweeteners is aspartame. As I have detailed in the past, a fair amount of evidence suggests this additive has potential to harm human health. Not surprisingly, aspartame’s manufacturers are keen to refer to the stack of evidence to say it’s safe. Less keen are they, however, for you to know about the pile of evidence and reports that says quite the opposite.

I should imagine another thing I suspect they would be unenthusiastic to know is that there is enormous disparity in the published results of industry funded and non-industry funded research: one on-line review reveals that while 100 per cent of industry funded studies proclaim aspartame to be benign, more than 90 per cent of independent studies and reports in the scientific literature say otherwise.

But this blog is not really about the safety of artificial sweeteners, but their effectiveness. The promise, remember, is that these are preferred to sugar for the purposes of weight control. What, is the evidence for this?

To know for sure whether artificial sweeteners are better than sugar for weight control they would need to be subjected to ‘randomised controlled trials’. This essentially means taking a group of individuals and randomly assign them to a diet containing artificial sweetener or sugar. In the ideal World, neither the participants nor the scientists conducting the study will know who is consuming what. At the end of a pre-determined period, the ‘code is cracked’ and an assessment can be made of who did better in the weight stakes (if anyone).

This sort of study that would be used to test the effectiveness of a pharmaceutical agent and validate it as fit for purpose. However, the same requirements do not exist for food. And despite all the talk about how artificial sweeteners are the ‘healthy’ choice for weight, I have not been able to trace one single randomised controlled trial in the scientific literature that has tested the weight loss ‘benefits’ of an artificial sweetener.

This doesn’t mean that such studies have not been done. They might have been done, whether they been published in another matter, however. I can’t prove this has happened, but if no such study has been done, one might ask ‘why’? I mean it’s not as though there’s not enough cash floating around in this particular industry to fund such a study.

One reason why the manufacturers may be hesitant to study the effectiveness of its product properly and publish the results is that here is at least some evidence that consuming artificially sweetened foods actually stimulates the appetite. For example, one British study found that women given saccharin-sweetened lemonade were found to consume considerably more calories overall compared to those drinking regular (sugary) lemonade [1]. In another study, experimenters found that subjects who had eaten yoghurt sweetened with saccharin were inclined to eat more than those who had eaten yoghurt sweetened with sugar [2]. There is other evidence which suggests that aspartame too has the capacity to stimulate the appetite [3].

With all this background in mind, I was interested to read today about a study which adds weight to the idea that artificial sweeteners do not help, and may hinder, healthy weight control [4]. Let me say upfront that this study was done in rats. I generally don’t do much reporting of animal studies. To be frank, there’s usually enough human-focused work out there not to need to examine animal studies. However, sometimes I do feel like animal research can further or deepen our knowledge and understanding, and this is one of those occasions.

I should also make clear that while this study has been widely covered on and off-line, it is not available to view in the on-line edition of the publication in which it appears (Behavioral Neuroscience). As a result, I have not read the actual study and am going on the reports of the study instead.

From these reports I have been able to glean that in this study, conducted at Purdue University in the USA, rats were fed with yoghurt sweetened with either sugar or saccharin. They were then allowed free access to other foods. Subsequent to eating the yoghurt, it appears that that the saccharin-fed mice ate more calories than their sugar-eating counterparts. Not only this, but they gained more weight (including in the form of fat) too.

Apparently, the authors of this study claim that their data: “…clearly indicate that consuming a food sweetened with no-calorie saccharin can lead to greater body-weight gain and adiposity than would consuming the same food sweetened with higher calorie sugar.”

I read that that one theory they have suggested for this ‘paradoxical’ finding is that the arrival of a sweet taste in the mouth helped prime the metabolism for the arrival of a calorie-heavy, sweet meal into the digestive system. And that when that meal did not duly arrive, the poor rats’ bodies got confused and have more trouble regulating its appetite when other food is around. This seems a very convoluted way of saying ‘artificial sweeteners have the capacity to stimulate the appetite more than sugar’. But then again, we already knew that was the case on the basis of previous work done, not in rats, but human beings.

References:

1. Rogers PJ, et al. Separating the actions of sweetness and calories: effects of saccharin and carbohydrates on hunger and food intake in human subjects. Physiol Behav 1989;45:1093–1099

2. Lavin JH, et al. The Effect of Sucrose- and Aspartame-Sweetened Drinks on Energy Intake, Hunger and Food Choice of Female, Moderately Restrained Eaters International Journal of Obesity. 1997;21:37-42

3. Tordoff MG, et al. Oral stimulation with aspartame increases hunger. Physiol Behav 1990;47:555–559

4. Swithers SE, et al. A Role for Sweet Taste: Calorie Predictive Relations in Energy Regulation by Rats. Behavioral Neuroscience 2008;122(1)

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