Artificial sweeteners may promote diabetes, claim scientists

Controversial research suggests artificial sweeteners may raise blood sugar levels by promoting growth of certain gut bacteria.

 Artificial sweeteners may contribute to soaring levels of diabetes, according to a controversial study that suggests the additives could exacerbate the problem they are meant to tackle.

Researchers in Israel found that artificial sweeteners used in diet drinks and other foods can disrupt healthy microbes that live in the gut, leading to higher blood sugar levels – an early sign of diabetes.
Sweeteners such as saccharin, aspartame and sucralose are widespread in western diets and are often used to cut calories or prevent tooth decay. The additives are so common that scientists behind the latest study called for a reassessment of the “massive usage” of the chemicals.

“Our findings suggest that non-caloric artificial sweeteners may have directly contributed to enhancing the exact epidemic that they themselves were intended to fight,” the authors write in the journal Nature.

Eran Elinav, a senior author on the study at the Weizmann Institute of Science in Rehovot, said that while the evidence against the sweeteners was too weak to change health policies, he had decided to give them up.

But the study has left many experts unconvinced. The findings draw largely on tests of just one sweetener in mice, raising doubts about their relevance for people, and to other sweeteners. Large studies in humans have found that sugar substitutes can help people maintain a healthy weight and protect against diabetes.

“This new report must be viewed very cautiously,” said Stephen O’Rahilly, director of the Metabolic Diseases Unit at Cambridge University, “as it mostly reports findings in mice, accompanied by human studies so small as to be difficult to interpret.”

Brian Ratcliffe, professor of nutrition at Robert Gordon University in Aberdeen, said: “Most of the effects that they report relate to saccharin with little or no effect of aspartame. Their paper ought to be limited to ‘saccharin’ in the title rather than attributing the effects to all artificial sweeteners.”

The UK is poised to fall in line with World Health Organisation recommendations to halve sugar intake to 5% of daily calories, a move expected to drive sales of diet drinks and low-calorie foods.
In the first of a series of experiments, the Israeli group found that mice fed on three artificial sweeteners – saccharin, aspartame and sucralose – developed high blood sugar levels. But when the mice were given antibiotics to kill off their gut microbes, the ill effects disappeared.

The scientists then focused on saccharin. They transferred gut microbes from mice fed on the sweetener to different mice that had no gut bacteria of their own. Soon after, the recipient mice developed high blood sugar levels themselves. Genetic analyses of the gut microbes from mice fed on saccharin found that as a group they behaved differently, breaking down more carbohydrate in the diet than normal.

The scientists ran tests on 400 people and found that those who consumed the most artificial sweeteners had different gut microbes than others, and on average were heavier and more glucose intolerant.

In their final set of experiments, the scientists gave seven people the maximum allowed daily dose of saccharin for a week. Each dose was enough to sweeten around 40 cans of diet cola. At the end of the week, four in seven had high blood sugar levels and their gut microbes mirrored the changes seen in mice fed on the additives.

To round off the study, the researchers transferred bugs from the people who developed high blood sugar after massive doses of artificial sweeteners into mice that had no gut bugs of their own. These mice went on to develop high blood sugar too.

According to Elinav, the study shows that artificial sweeteners may contribute to higher blood sugar in mice and some people. One possible explanation is that artificial sweeteners let some microbes thrive at the expense of others, leaving a population that extracts more energy from the diet than normal.

“This large body of work we’ve performed should be studied further because of the potentially harmful effects that could be happening from sweetener consumption to very large subsets of the population,” said Eran Segal, a co-author of the paper.

There are studies that report more diabetes among people who consume lots of diet drinks. But in many cases it is impossible to work out what is to blame. Lots of people are already fat and on course to develop diabetes when they turn to diet drinks to lose weight.

Nita Forouhi, head of nutritional epidemiology at Cambridge, said the study suggested artificial sweeteners were not the “innocent magic bullets” they were intended to be. “But it does not yet provide sufficient evidence to alter public health and clinical practice,” she said.

Christopher Corpe of King’s College London, who studies how the gut senses sugars, said that future work needed to draw on much larger numbers of healthy and obese or diabetic people who consume more realistic amounts of artificial sweeteners.

Poliomyelitis

Fact sheet N°114
Updated October 2015

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Key facts

·                                 Polio (poliomyelitis) mainly affects children under 5 years of age.

·                                 One in 200 infections leads to irreversible paralysis. Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.

·                                 Polio cases have decreased by over 99% since 1988, from an estimated 350 000 cases then, to 359 reported cases in 2014. The reduction is the result of the global effort to eradicate the disease.

·                                 Today, only 2 countries (Afghanistan and Pakistan) remain polio-endemic, down from more than 125 in 1988.

·                                 As long as a single child remains infected, children in all countries are at risk of contracting polio. Failure to eradicate polio from these last remaining strongholds could result in as many as 200 000 new cases every year, within 10 years, all over the world.

·                                 In most countries, the global effort has expanded capacities to tackle other infectious diseases by building effective surveillance and immunization systems.

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Polio and its symptoms

Polio is a highly infectious disease caused by a virus. It invades the nervous system, and can cause total paralysis in a matter of hours. The virus is transmitted by person-to-person spread mainly through the faecal-oral route or, less frequently, by a common vehicle (e.g. contaminated water or food) and multiplies in the intestine. Initial symptoms are fever, fatigue, headache, vomiting, stiffness of the neck and pain in the limbs. One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, 5% to 10% die when their breathing muscles become immobilized.

People most at risk

Polio mainly affects children under 5 years of age.

Prevention

There is no cure for polio, it can only be prevented. Polio vaccine, given multiple times, can protect a child for life.

Global caseload

Polio cases have decreased by over 99% since 1988, from an estimated 350 000 cases in more than 125 endemic countries then, to 359 reported cases in 2014.

Today, only 2 countries in the world remain endemic for the disease–the smallest geographic area in history. Of the 3 strains of wild poliovirus (type 1, type 2, and type 3), wild poliovirus type 2 was eradicated in 1999 and case numbers of wild poliovirus type 3 are down to the lowest-ever levels with the no cases reported since November 2012 from Nigeria.

The Global Polio Eradication Initiative

Launch

In 1988, the forty-first World Health Assembly adopted a resolution for the worldwide eradication of polio. It marked the launch of the Global Polio Eradication Initiative (GPEI), spearheaded by national governments, WHO, Rotary International, the US Centers for Disease Control and Prevention (CDC), UNICEF, and supported by key partners including the Bill and Melinda Gates Foundation. This followed the certification of the eradication of smallpox in 1980, progress during the 1980s towards elimination of the poliovirus in the Americas, and Rotary International’s commitment to raise funds to protect all children from the disease.

Progress

Overall, since the GPEI was launched, the number of cases has fallen by over 99%. Today, only 2 countries in the world remain polio-endemic: Pakistan and Afghanistan.

In 1994, the WHO Region of the Americas was certified polio-free, followed by the WHO Western Pacific Region in 2000 and the WHO European Region in June 2002. On 27 March 2014, the WHO South-East Asia Region was certified polio-free, meaning that transmission of wild poliovirus has been interrupted in this bloc of 11 countries stretching from Indonesia to India. This achievement marks a significant leap forward in global eradication, with 80% of the world’s population now living in certified polio-free regions.

Of the 3 types of wild poliovirus (type 1, type 2 and type 3), type 2 wild poliovirus transmission has been successfully stopped (since 1999).

More than 13 million people are able to walk today, who would otherwise have been paralysed. An estimated 1.5 million childhood deaths have been prevented, through the systematic administration of Vitamin A during polio immunization activities.

Opportunity and risks: an emergency approach

The strategies for polio eradication work when they are fully implemented. This is clearly demonstrated by India’s success in stopping polio in January 2011, in arguably the most technically-challenging place, and polio-free certification of the entire South-East Asia Region of the World Health Organization occurred in March 2014.

However, failure to implement strategic approaches leads to ongoing transmission of the virus. Endemic transmission is continuing in Pakistan and Afghanistan. Failure to stop polio in these last remaining areas could result in as many as 200 000 new cases every year, within 10 years, all over the world.

Recognizing both the epidemiological opportunity and the significant risks of potential failure, the new Polio Eradication and Endgame Strategic Plan 2013-2018 has been developed, in consultation with polio-affected countries, stakeholders, donors, partners and national and international advisory bodies. The new Plan was presented at a Global Vaccine Summit in Abu Dhabi, United Arab Emirates, at the end of April 2013. It is the first plan to eradicate all types of polio disease simultaneously – both due to wild poliovirus and due to vaccine-derived polioviruses.

Future benefits of polio eradication

Once polio is eradicated, the world can celebrate the delivery of a major global public good that will benefit all people equally, no matter where they live. Economic modelling has found that the eradication of polio would save at least US$ 40–50 billion over the next 20 years, mostly in low-income countries. Most importantly, success will mean that no child will ever again suffer the terrible effects of lifelong polio-paralysis.

Does Marijuana Change the Brain?

by Tia Ghose, Senior Writer | August 26, 2015 11:00am ET

The effects of marijuana on the brain may be more complicated than experts previously thought, and may depend on factors related to the person using the drug, such as their genetics, two new studies suggest.

Marijuana use does not lead to smaller brain size in teens, one of the new studies found. That finding contrasts with previous research suggesting the drug does have this effect.

But in people who are genetically prone to schizophrenia, marijuana could alter their brain development in potentially negative ways, according to the other new study.



Together, the two new studies point to a complicated and confusing picture of marijuana's effects on young brains. The studies suggest that a person's environment, culture and genes all play murky roles in the process. 

Long-term effects

Dozens of studies have researched the differences between the brains of pot smokers and those of people who don't smoke marijuana. Overall, the research shows that heavy pot smokers — those who use pot at least three times a day — tend to have smaller gray-matter volumes in the orbitofrontal cortex , a brain region tied to addiction, but they also had greater connectivity between brain regions, according to a 2014 study in the journal Proceedings of the National Academy of Sciences.

Other studies have shown that people who smoke pot in their teen years have lower IQs later on . And several studies have found that people whosmoke pot are more likely to develop schizophrenia than those who don't use the drug.

But the problem plaguing all of these studies is that people who smoke marijuana are different from those who don't in lots of ways, and untangling cause and effect can be incredibly tricky, the researchers said.

No obvious differences

To get a better picture of the effects of marijuana on the teenage brain, Arpana Agrawal, a geneticist at Washington University in St. Louis, and her colleagues looked at magnetic resonance imaging (MRI) studies of the brains of 241 pairs of same-sex siblings, including some who were twins.

In some pairs, only one sibling had smoked marijuana; in others, both had smoked pot; and in some, neither sibling had used cannabis. By studying such pairs, who share half their DNA, the team hoped to untangle the effects of marijuana from those of other factors, such genetics or the environment of a person's home.

The team found that teens who had smoked pot — even once — did have smaller brain volume in the amygdala, a region associated with emotion processing and reward seeking, compared with those who had not smoked pot. The pot smokers also had smaller volume in the right ventral striatum, a brain region tied to reward processing.

However, the siblings who did not smoke pot but who shared similar genes and environment with their pot-smoking siblings also tended to have smaller volume in these key brain regions, compared with siblings who both avoided marijuana.

"That suggests there might be common factors, genetic and environmental, that predispose us to using marijuana that also contribute to variations in our brain volumes," Agrawal told Live Science.

High risk factors

In a second study, Dr. Tomáš Paus, a neuroscientist at the Rotman Research Institute, Baycrest in Toronto, and his colleagues used MRI to study the brains of more than 1,500 teenage boys. In one subgroup, the team looked at the teenagers' brains at two points in time: when the youngsters were almost 15 and almost 19 years old.

They found that over the four years, those who had smoked pot and also had several genes that increased their risk of schizophrenia had thinning in the cortex — the outer, gray matter of the brain — compared with those who had the same genes but had not smoked pot.

It's not clear what the thinning in this brain region means for what's going on inside the brain. It could be that the pot smokers had less-connected brain cell networks, fewer capillaries nourishing blood vessels in the cortex or fewer support cells, such as glial cells, Paus speculated.

However, the findings do hint that marijuana itself could be responsible for the thinning in the cortex, Paus said. The brain regions that showed the greatest cortical thinning also have high concentrations of cannabinoid receptors, which bind the active ingredients in marijuana, Paus said.

Schizophrenia is rare, and Paus noted that even among teens with the highest genetic risk of schizophrenia, only 4 percent actually develop the disease. About 1 percent of people in the general population have schizophrenia. In the study, the team didn't follow the teens long enough to see how many developed the disorder.

In addition, because schizophrenia is so rare, the study was too small to get a statistically meaningful answer to the question of whether smoking pot increased the teens' risk of the disorder, he added.

Still, the findings suggest that in susceptible people, smoking pot could alter brain development. "All we are saying is that if you combine cannabis use with the genetic risk, then the brain is maturing in a slightly different way," Paus told Live Science.

Jury still out

But scientists still aren't sure whether, and how, marijuana harms young brains.

"We really do not fully understand what impact marijuana use has on us, and I think, in particular, in youth," Agrawal said.

In an editorial accompanying the new studies in the journal, Dr. David Goldman, a neurogeneticist at the National Institute on Alcohol Abuse and Alcoholism in Rockville, Maryland, wrote that the effects of marijuana may vary among people.

"Because of diversity in genotype and environment, one person's sugar may be another's poison," Goldman wrote.

Still, that doesn't mean marijuana is safe for people with the "right" genes, Goldman added. Like other drugs, the effect of marijuana is dependent on the dose, and as high-concentration tetrahydrocannabinol (THC) weed becomes increasingly popular, the effect of the drug could change, he said.