Thursday, June 14, 2012

Not sugar alone



Recently  we said be careful of sugar, well ad artificial sweeteners to that list too.
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Because anyone looking to artificial sweeteners as an alternative, as pastel-packaged reassurances that regulators won’t ever need to pry donuts from their cold, dead and pudgy hands, science offers only more uncertainty. 
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Some studies even suggest that fake sugar may cause the same problems as real sugar.
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That’s the $64,000 question, said Susan Swithers of the Ingestive Behavior Research Center at Purdue University. 
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There are several epidemiological studies showing increased risk of metabolic syndrome in coincidence with the consumption of diet sodas — a rich source of sweeteners. 
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But how they should be interpreted is not really clear right now. 
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Because they’re correlational studies, they don’t tell us what caused what.
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Artificial sweeteners are a fast-growing, multi-billion dollar product, present in thousands of foodstuffs and synthesized by chemists as zealously as drug researchers pursue blockbuster drugs. 
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But as described in a massive 2008 American Journal of Clinical Nutrition Review, the seemingly obvious health benefits expected of low-calorie sugar replacements have failed to materialize.
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Even as Americans consumed more sweeteners, waistlines continued to expand. 
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Cause and effect was ambiguous. 
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Sweeteners might lead to weight gain, but maybe people most prone to gaining weight consume the most sweeteners. 
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This association may be coincidental or causal, and either mode of directionality is plausible,concluded that study’s authors.
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Artificial sweetener use might be fuelling -- rather than fighting -- our escalating obesity epidemic.
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Other researchers, however, are more suspicious. 
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When University of Texas Health Science Center epidemiologists conducted a 9-year-long study of 5,158 adult residents of San Antonio, Texas they found a link between sweeteners and obesity.
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It persisted even after statistically accounting for gender, ethnicity, diet and beginning-of-diet body mass index. 
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These findings raise the question whether artificial sweetener use might be fueling — rather than fighting — our escalating obesity epidemic, they wrote.
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Another study of 6,184 adult Americans linked diet soda consumption with higher rates of metabolic syndrome, the umbrella term for a physiological disruption that leads to heart disease, stroke and type 2 diabetes. 
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Once again, the link survived statistical adjustment for demographics, lifestyle and diet.
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That’s precisely what’s expected from eating too much sugar, which at least in rats is converted in the liver to fat. 
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That in turn provokes, via as-yet-unidentified mechanisms, resistance to insulin, a hormone used by cells to process glucose, better known as blood sugar.
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When insulin’s signals are ignored, blood sugar levels rise. 
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Metabolic syndrome follows. 
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But why should this happen when eating fake sugar, not real?
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Swithers thinks she knows. 
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In 2008, she and fellow Purdue researcher Terry Davidson fed rats a yoghurt supplement sweetened either with glucose a simple sugar, or zero-calorie saccharin. 
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Apart from the supplement, both groups ate standard rat fare. 
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Those that ate saccharin didn’t eat any more than the sugar group, but packed on more fat, gained more weight and consumed extra calories. 
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A follow-up 2009 study reinforced the findings, and found that unusual weight gain persisted even when rats stopped eating sweeteners.
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According to Swithers, two mechanisms may be responsible. 
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When the rats’ bodies learned that sweetness didn’t predict an imminent caloric rush, as would naturally be produced by sugar-rich foods, their bodies may have automatically shifted into calorie-saving mode. 
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At the same time, metabolic acceleration that normally occurs when eating high-calorie foods, and helps to process them, may have been slowed.
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All of our work has been in rats. 
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We think similar processes happen in humans, but we haven’t tested them, Swithers said.
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Steve Snodgrass

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