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Study Highlights Why Some Probiotics Survive Longer in the Gut Than Others

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As scientists continue to find out more about the human microbiome, that ecosystem of bacteria that live on and inside us, it’s clear that influencing the type of bacteria that colonize your skin and gut can have tangible effects on your health and well-being. But just how to change the composition of your bacteria isn’t clear, and there’s still not enough research to show that the probiotics available now are effective at treating specific disorders. Gut bacterial colonies tend to be very stable even in the face of probiotic treatments, and studies have indicated that alterations in the gut bacteria in cases of fecal transplants tend to be temporary.

However, a new study finds that selecting the right bacterial strain for the gut environment can make a major difference in whether or not the probiotic can impact the microbiome. Published today in Cell Host & Microbe, the study was led by Jens Walter, an associate professor of nutrition, microbes, and gastrointestinal health at the University of Alberta.

The research team gave 23 volunteers a daily dose of the probiotic strain AH1206 of the bacteria Bifidobacterium longum, one of the most common species of bacteria found in the gut. Half took the bacteria dose for two weeks while the other half took a placebo, and then the two groups switched for a second two-week round. The researchers periodically checked their gut flora composition via fecal samples in the months that followed. A third of the volunteers who took the probiotic showed lasting changes to their gut microbiome, showing evidence of the strain’s colonization up to six months afterward. In the other two-thirds of the group, the bacteria had disappeared within a month.

These “persisters,” as the researchers call them, had slightly different microbiomes than the other volunteers at the outset of the study. They had lower levels of that particular species or species with similar genes. Essentially, the bacteria could only survive if it was filling a particular gap in the microbiome. If pre-existing bacterial strains had already colonized the gut, the new bacteria had to compete for the same resources, and usually didn’t survive.

With only 23 volunteers (and just eight “persisters”), this study is far from definitive, especially since the researchers didn’t control for volunteers’ different diets. But Walter likens the main idea back to Darwinism. “Competition in ecosystems is especially harsh amongst closely related species because they have the same resource requirements,” he explains in a press statement. But if someone has lost a particular strain of bacteria or their body never had it in the first place, it’s possible to repopulate the microbiome with that strain. By figuring out who would be a “persister,” researchers could potentially personalize probiotics to be more effective, the study indicates.

The study also suggests that the reason commercially available probiotics might be ineffective is that the strains they contain—if they even contain the type of bacteria claimed on the label—aren’t indigenous to the gut, and thus, perhaps unsurprisingly, aren’t very well adapted to survive there.

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science
New Patient Test Could Suggest Whether Therapy or Meds Will Work Better for Anxiety
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Like many psychological disorders, there's no one-size-fits-all treatment for patients with anxiety. Some might benefit from taking antidepressants, which boost mood-affecting brain chemicals called neurotransmitters. Others might respond better to therapy, and particularly a form called cognitive behavioral therapy, or CBT.

Figuring out which form of treatment works best often requires months of trial and error. But experts may have developed a quick clinical test to expedite this process, suggests a new study published in the journal Neuropsychopharmacology.

Researchers at the University of Illinois at Chicago have noted that patients with higher levels of anxiety exhibit more electrical activity in their brains when they make a mistake. They call this phenomenon error-related negativity, or ERN, and measure it using electroencephalography (EEG), a test that records the brain's electric signals.

“People with anxiety disorders tend to show an exaggerated neural response to their own mistakes,” the paper’s lead author, UIC psychiatrist Stephanie Gorka, said in a news release. “This is a biological internal alarm that tells you that you've made a mistake and that you should modify your behavior to prevent making the same mistake again. It is useful in helping people adapt, but for those with anxiety, this alarm is much, much louder.”

Gorka and her colleagues wanted to know whether individual differences in ERN could predict treatment outcomes, so they recruited 60 adult volunteers with various types of anxiety disorders. Also involved was a control group of 26 participants with no history of psychological disorders.

Psychiatrists gauged subjects’ baseline ERN levels by having them wear an EEG cap while performing tricky computer tasks. Ultimately, they all made mistakes thanks to the game's challenging nature. Then, randomized subjects with anxiety disorders were instructed to take an SSRI antidepressant every day for three months, or receive weekly cognitive behavioral therapy for the same duration. (Cognitive behavioral therapy is a type of evidence-based talk therapy that forces patients to challenge maladaptive thoughts and develop coping mechanisms to modify their emotions and behavior.)

After three months, the study's patients took the same computer test while wearing EEG caps. Researchers found that those who'd exhibited higher ERN levels at the study's beginning had reduced anxiety levels if they'd been treated with CBT compared to those treated with medication. This might be because the structured form of therapy is all about changing behavior: Those with enhanced ERN might be more receptive to CBT than other patients, as they're already preoccupied with the way they act.

EEG equipment sounds high-tech, but it's relatively cheap and easy to access. Thanks to its availability, UIC psychiatrists think their anxiety test could easily be used in doctors’ offices to measure ERN before determining a course of treatment.

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Food
A Pitless Avocado Wants to Keep You Safe From the Dreaded 'Avocado Hand'
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The humble avocado is a deceptively dangerous fruit. Some emergency room doctors have recently reported an uptick in a certain kind of injury—“avocado hand,” a knife injury caused by clumsily trying to get the pit out of an avocado with a knife. There are ways to safely pit an avocado (including the ones likely taught in your local knife skills class, or simply using a spoon), but there’s also another option. You could just buy one that doesn’t have a pit at all, as The Telegraph reports.

British retailer Marks & Spencer has started selling cocktail avocados, a skinny, almost zucchini-like type of avocado that doesn’t have a seed inside. Grown in Spain, they’re hard to find in stores (Marks & Spencer seems to be the only place in the UK to have them), and are only available during the month of December.

The avocados aren’t genetically modified, according to The Independent. They grow naturally from an unpollinated avocado blossom, and their growth is stunted by the lack of seed. Though you may not be able to find them in your local grocery, these “avocaditos” can grow wherever regular-sized Fuerte avocados grow, including Mexico and California, and some specialty producers already sell them in the U.S. Despite the elongated shape, they taste pretty much like any other avocado. But you don’t really need a knife to eat them, since the skin is edible, too.

If you insist on taking your life in your hand and pitting your own full-sized avocado, click here to let us guide you through the process. No one wants to go to the ER over a salad topping, no matter how delicious. Safety first!

[h/t The Telegraph]

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