Brain May Not Be Fooled by Sugar Substitutes (Aspartame makes you crave carbohydrates so you gain weight)

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latimes.com/features/health/la-he-sweet-brain31-2009aug31,0,2078819.story

 

 

latimes.com

 

 

 

 

The brain may not be fooled by sugar substitutes

 

 

 

 

Studies indicate that, on some level, we know

real from fake. So what does that mean with regard to weight loss?

 

By Douglas Fox

 

August 31, 2009

 

 

As the palette of artificial sweeteners has grown

and manufacturers have honed the skill with which

they blend them to mimic sugar taste, debate has

swirled around whether these sensory stand-ins

really help people consume fewer calories and avoid weight gain.

 

New research adds another dimension to the

uncertainty: It suggests that even when

artificial sweeteners fool the taste buds, they

still don't fool the ultimate arbiter of our

appetites -- our subconscious brains.

 

The latest evidence for this comes from a brain

scanning study performed in the Netherlands. Paul

Smeets, a neuroscientist at University Medical

Center Utrecht, used a technique called

functional magnetic resonance imaging (fMRI) to

measure brain responses in people sipping two

versions of orangeade, one containing sugar and

one containing a mix of four artificial

sweeteners: aspartame, acesulfame K, cyclamate and saccharin.

 

The mixture of artificial sweeteners was

concocted to match the taste of real sugar as

closely as possible. And the sugary and

artificial drinks were administered on different

days -- making it harder for the tasters to

notice any difference between the two. Subjects

often guessed wrong on which drink was which. " They didn't know, " Smeets says.

 

Yet the fMRI scans revealed consistent

differences in how their brains responded.

 

Both sugar and the noncaloric sweeteners

activated a brain region called the amygdala,

which signals sensory pleasure. But only the

sugared drink turned on a cherry-sized nugget of

brain tissue in a region called the caudate.

 

That little nugget, Smeets concluded, seemed to

represent an unconscious perception of calories

-- assessed quite separately from the sweet taste.

 

" We think the brain can distinguish, even if the

people themselves cannot distinguish, between a

caloric and a noncaloric sweet drink, " says

Smeets, who presented his results at the Human

Brain Mapping meeting in San Francisco in June.

 

Brain-imaging experiments sometimes draw

criticism for producing little more than colored

spots on a brain map -- high-tech Rorschach ink

blots that researchers may over-interpret

according to their own biases. But another study,

published earlier this year, suggests that Smeets is onto something.

 

Edward Chambers, an exercise physiologist at the

University of Birmingham in Britain, compared the

effects of sugar and artificial sweeteners on

peoples' ability to do hard aerobic exercise --

and he found some striking differences.

 

Chambers has previously shown that the mere taste

of sugar can improve endurance in athletes who

have fasted for several hours. If the athletes

rinse their mouth with sugared water but don't

swallow any, it improves their performance in an

hour-long cycling workout by a small but

consistent amount. The apparent promise that

sugar will soon reach the bloodstream provokes

the cyclists' brains to drive their legs harder

-- the same way that the promise of a paycheck in

the mail motivates a cash-strapped student to go shoe shopping.

 

But when Chambers tried the same experiment with

a mixture of the artificial sweeteners aspartame

and saccharin, he saw no such effect. Tasting the

artificial sweeteners didn't improve cycling

speed, even though they tasted sweet.

 

Tasting a nonsweet sugar, maltodextrin (whose

flavor was masked with aspartame and saccharin so

it tasted the same), did improve cycling speed.

 

" The sweetness is the conscious perception of the

substance, " Chambers says. " But there also

appears to be this unconscious nutrient-sensing

occurring " in the mouth. Athletes couldn't

consciously distinguish the sugared and

nonsugared drinks, but their brains picked up the difference.

 

Chambers also did fMRI scans of his athletes'

brains. He found that the sugared mouth rinses

strongly activated two reward centers in the

brain, the anterior cingulate cortex and caudate,

whereas the artificial sweeteners activated these

brain areas only weakly -- similar to Smeets' results.

 

These studies heighten lingering questions about

the usefulness of artificial sweeteners. Although

some studies over the years have found that

artificially sweetened foods and drinks reduce

calorie consumption and weight gain, others suggest they might not.

 

" We have some idea that in the short term there's

calorie savings " with artificial sweeteners, says

Adam Drewnowski, director of the Center for

Obesity Research at the University of Washington

in Seattle. " But then people say that what you do

today at lunch may not translate into saving

pounds of body weight at the end of four weeks. So we need more studies. "

 

Research has shown that drinking an artificially

sweetened beverage can whet the appetite and

stimulate people to eat more in a subsequent meal

-- an effect not seen when people drink a sugared

beverage or glass of water before eating. It

suggests that artificial sweeteners may turn on

brain areas that create appetite, but not provide

satiation. This might trigger people to eat a

bigger lunch, says Guido Frank, a psychiatrist

who studies eating disorders and brain responses

to sweeteners at the University of Colorado at

Denver. Frank's brain imaging experiments have hinted as much.

 

In addition, some epidemiological studies find

that people who regularly consume artificially

sweetened drinks carry, on average, a few more pounds than people who don't.

 

But other studies have muddied the picture.

 

A small study published in 2007 found that

artificially sweetened drinks trigger more eating

only in people who don't drink them very often.

People who habitually drink lots of artificially

sweetened beverages didn't consume a larger meal

after drinking one -- suggesting that their

subconscious brains have adjusted to the sweeteners over time.

 

" There is no 100% clear message, " Frank

concludes. But, he adds, just as people are

encouraged to keep an eye on their intake of real

sugars, so should the dietary role of artificial

sweeteners be carefully considered.

 

" If you manage to replace all your sugar drinks

with a combination of a glass of water, a can of

diet soda and three carrots, that would be a good

thing, " he says. " But you could argue that using

large amounts of artificial sweeteners is not

really as helpful as one might think, because

maybe you cannot really trick the brain. Maybe

the body still gets the calories from somewhere else. "

 

One approach might be to avoid the zero-calorie

drinks that crowd our grocery aisles in favor of

reduced-calorie drinks that combine artificial

sweeteners with real sugars. Such drinks might

preserve the brain's connection between sweetness and calories, Smeets says.

 

Or one might drink sugary drinks -- but more

slowly. A study published earlier this year by

Smeets found some merit to this advice. Smeets

allowed his subjects to drink their fill of

sugar-sweetened orangeade but strictly controlled

the size of their sips using a pump. People drank

less orangeade overall when their sip size was smaller.

 

The upshot, Smeets says, is that a low-tech

solution might suffice -- for example, drinking

through a thin straw rather than gulping, and

avoiding artificial sweeteners altogether. Or, as

Frank suggests, substituting a glass of cold

water for that 44-ounce soft drink.

 

" The ideal artificial sweetener would really fool

the body, " Smeets says. " But I'm not sure that is possible. "

 

<healthhealth

 

, <http://www.latimes.com/>The Los Angeles Times

 

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More information on aspartame on www.mpwhi.com,

www.dorway.com and www.wnho.net Aspartame

Toxicity Center, www.holisticmed.com/aspartame