Artificial Sweetener Fails to Fool the Brain

The implicit advantage that artificial sweeteners have over sugar is that, being virtually devoid of calories, they’re a better option for those wanting to control their weight. However, as I described in a recent blog post here, there is no good evidence that artificial sweeteners promote weight loss compared to sugar. Plus, there is actually some evidence that artificial sweeteners may promote weight gain: in one study (referred to in the blog post linked to above), rats eating artificially-sweetened yoghurt were found to eat more and get fatter than rats fed yoghurt sweetened with sugar.

Some evidence has suggested that artificial sweeteners have the capacity to stimulate appetite, so I was very interested to read this week about a study which looked more deeply into the effect that artificial sweeteners have on the brain. In this study, women were given a drink a solution containing either the artificial sweetener sucralose (brand name Splenda) or sucrose (table sugar). As they drunk this their brain activity was monitored using what is known as ‘functional magnet resonance imaging’ (basically, this allowed researchers to see what parts of the brain are activated once individuals had tasted the sucralose/sucrose solution).

One part of the brain that the researchers focused on in this study is known as the ‘insula’. The insula is involved in the brain’s sensing of taste, and it also believed to play a role in enjoyment and the sensation of ‘pleasantness’. Interestingly, drinking sugar activated the brain regions involved in registering pleasure more extensively than drinking sucralose.

This difference was found despite the fact that individuals were unable to distinguish between sucrose and sucralose on the basis of taste. In other words, while individuals are unable to consciously distinguish between sugar and sucralose, the brain appeared to know the difference. And it appears that an artificial sweetener may simply not give the level of pleasure and satisfaction that may be derived from sugar. This, in turn, could lead individuals to seek satisfaction from other foodstuffs.

Now, if this is true of artificial sweeteners in general, then it might help to explain why rats eating an artificially sweetened food end up eating more and getting fatter than rats eating the same food sweetened with sugar. It might also explain why there is such a dearth of good evidence regarding the ‘benefits’ of artificial sweeteners with regard to weight control. The results of this study seem to suggest that you just can’t trick the brain into thinking it’s had something (sugar) when it hasn’t.

References:

Frank GK, et al. Sucrose activates human taste pathways differently from artificial sweetener. Neuroimage. 2008;39(4):1559-69

7 Responses to Artificial Sweetener Fails to Fool the Brain

  1. Liz 20 June 2008 at 9:26 am #

    There are a number of studies that reflect this e.g. the work by Davidson and Swithers – http://www.purdue.edu/UNS/html4ever/2004/040629.Swithers.research.html – though to see critcisms of this go to http://findarticles.com/p/articles/mi_qn4188/is_20040708/ai_n11470297

    It goes to show how complex the satiety mechanisms are and how sophisticated the brain is. Given this, it makes sense to eat foods in as natural a form as possible because our brain has developed to cope with these foods.

    As sweet flavours are so alluring and sweet foods are so readily available it’s difficult for people to reduce them in their diet, but these studies certainly suggest that artifical sweeterners are not a good alternative.

  2. RNB 20 June 2008 at 1:51 pm #

    As a diabetic, my question is how do the natural non-carb sweeteners play into all this, e.g. Stevia?

  3. Dan 20 June 2008 at 6:25 pm #

    I don’t dispute the findings, but I wonder what kind of overall diet these people were on? Were they on the recommended high starch diet? Since they are on a high glucose-producing diet anyway, maybe they are craving sugar and their brain can tell the difference between sugar and artificial sweetner.

    I am on a low carb diet and use splenda moderately. It doesn’t create any cravings for me. Maybe with a low carb diet and more fat, they would feel satisfied and the brain wouldn’t be wanting sugar anyway.

    Just my speculation. Thanks for all the great blog entries.

  4. helen 22 June 2008 at 10:05 pm #

    Like Dan I use splena although sparingly I find it doesn’t taste exactly the same as sugar anyway it is not as sweet anyway since not having sugar for over 6 years I actually find I can’t stand the taste of it anyway it seems to be overly sweet to me and I don’t enjoy it like I did in my addiction to sugar days. I know for a fact that it actually deadens your taste buds so it is just one more reason to stay away. whereas when I use splenda in to sweeten something if the recipe calls for one cup of sugar I find 2 or 3 teaspoons of splenda to be totally adequate for that satisfying sweet taste! go figure?

  5. Dave 23 June 2008 at 3:00 pm #

    This article lends some credence:

    http://diabetes.diabetesjournals.org/cgi/content/full/55/11/2986

    Some interesting excerpts:

    “The SPM analysis, which corrects for global differences between groups, shows the most robust insulin-driven increases in relative glucose metabolism in bilateral ventral striatum and prefrontal cortex, including the insula. This network is involved in the integration of food-seeking behavior and food intake with hypothalamic energy balance control systems (8). The ventral striatum in particular mediates reward responses and has received intense interest in addictive disorders (30,31). A role for insulin in this region is highly relevant to food-seeking and feeding behaviors, implicating insulin in the reward sensations associated with eating, which themselves reflect the importance of food intake to survival.”

  6. HerbalJunky 30 March 2010 at 2:12 am #

    I will suggest use natural sweeteners like stevia rather than artificial ones. Stevia is not only zero calorie, zero glycemic index and all natural but also if taken with inulin fiber helps maintain a good cholesterol level.

    HerbalJunky

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  1. Masenka.Be » Blog Archive » Alternatives for sugar - 5 February 2009

    [...] taking light products. About a third of people, men and women alike, use some kind of sweetener. Sugar replacements don’t give extra calories like sugar. Also their are not so bad for your teeth. But remember that too much sweetener is also [...]

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