By GAUTAM NAIK
The artificial sweeteners in diet soda, yogurt and other foods consumed
by millions can raise the blood sugar level instead of reducing it, according
to new experiments in mice and people. The provocative finding—made possible
through a new avenue of research—is likely to stoke the simmering controversy
over whether artificial sweeteners help or hinder people's ability to lose
weight and lower their risk of diabetes.
The research shows that zero-calorie sweeteners such as saccharin,
sucralose and aspartame can alter the population of bacteria in the gut and
trigger unwanted changes such as higher blood glucose levels—a risk factor for
diabetes. "The scope of our discovery is cause for a public reassessment
of the massive and unsupervised use of artificial sweeteners," said Eran
Elinav, a physician and immunologist at Israel's Weizmann Institute of Science
and lead author of the study, which appeared Wednesday in the journal Nature.
Though many people consume artificial sweeteners instead of sugar to
control their weight, the scientific evidence that they work is mixed. Some
studies have indicated that the sweeteners can help lead to weight loss, while
others suggest they contribute to weight gain. One reason is that it isn't
clear whether people who consume artificial sweeteners are overweight because
of what they eat—or whether overweight people are the ones who typically
gravitate to such products.
Based on existing evidence, guidelines jointly published in 2012 by the
American Heart Association and the American Diabetes Association noted that
artificial sweeteners "when used judiciously…could facilitate reductions
in added sugar," and thus influence weight loss. The new Nature study
marks a significant advance because it brings together two separate areas of
research—the role of sweeteners in raising blood sugar levels, and the complex
workings of the vast colonies of bacteria that inhabit the gut. Individuals can
have differing bacterial colonies in their gut, meaning people respond
differently to what they consume.
In one experiment, the researchers found that mice whose diets included
saccharin, sucralose or aspartame had significantly higher blood-glucose levels
than mice whose diet included sugar, or no sugar at all. They next wanted to
test whether the fake sweeteners caused that metabolic change by altering the
balance of microbes in the animals' gut.
They transplanted bacteria from artificial-sweetener-fed mice or
sugar-fed mice into other mice that were bred to have no gut bacteria of their
own and that had never consumed a sweetener product. They found that the
bacterial transfer from the sweetener-fed mice raised the blood sugar levels in
the transplant recipients—suggesting that the gut microbes had triggered the
higher sugar levels in mice fed fake sweeteners.
Was the same link true for people? Dr. Elinav and his colleagues
examined the relationship between long-term consumption of artificial
sweeteners and various metabolic measurements in some 380 nondiabetic people.
They found that the bacteria in the gut of those who regularly ate fake
sweeteners were notably different from those who didn't. In addition, there was
a correlation between the sweetener consumption and a susceptibility to glucose
intolerance, which is a disturbance in the blood glucose level.
Correlation, however, doesn't necessarily mean causation. In the next
experiment, seven volunteers who normally didn't consume fake sugar were asked
to consume products high in the sweeteners. After four days, four of them had
significantly higher blood-sugar levels as well as altered populations of
bacteria in their gut—an outcome similar to what was seen in mice.
"This susceptibility to sweeteners [can now] be predicted ahead of
time by profiling the microbes in the people," said Eran Segal, a
co-author of the study and computational biologist at the Weizmann Institute.
In a statement, the Calorie Control Council, a trade group that
represents makers of artificial sweeteners and other food products, said the
Nature study suffered from several limitations. It said the results from the
mouse experiments may not apply to humans, while the human experiments had a
small sample size. It said further research was needed.
Researchers aren't sure about the exact mechanisms causing the
imbalance in the gut bacteria populations. But they found that several types of
bacteria that changed after the consumption of artificial sweeteners previously
had been associated with Type 2 diabetes in humans.
The results appears to demonstrate that for some people, artificial
sweeteners can alter the composition of gut bacteria in such a way that it may
contribute to—rather than reduce—certain metabolic conditions related to
obesity, such as glucose intolerance.
"We've been wondering why people who consume [artificial]
sweeteners don't always lose weight," said Judy Wylie-Rosett, a nutrition
expert at Albert Einstein College of Medicine in New York, who wasn't involved
in the Nature research. "This is a very intriguing study because it's the
first one that looks at gut microbes."
Artificial sweeteners have been around for more than a century. But no
one thought to embark on this type of study before because scientists'
understanding of how gut microbes respond to different foods and the metabolic
changes they induce is still in its infancy.
Some 100 trillion microbes live in the human body. Together, they have
at least 100 times as many genes as we do. Unlike the genes we are born with,
those microbes can be easily manipulated via drugs or changes in diet. This
knowledge has sparked a big push to understand the role of microbes in
regulating human health.
The authors of the Nature study are now recruiting hundreds of
volunteers for a much more ambitious study that will try to establish a link
between gut bacteria, their responses to hundreds of common food products and
the physical changes they induce in connection with obesity, diabetes and other
diseases.
Source: http://online.wsj.com/articles/research-shows-zero-calorie-sweeteners-can-raise-blood-sugar-1410973201?mod=trending_now_3
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