There’s Little Evidence That Probiotics Help Most GI Symptoms
By Shawn Radcliffe
Probiotics are a booming business, consumed by millions of health-conscious Americans in pill form, fermented foods like yogurt, or other food products.
But a new guideline by the American Gastroenterological Association cautions that there's not enough scientific evidence to recommend using these so-called good bacteria and yeasts to treat most digestive diseases.
"While our guideline does highlight a few use cases for probiotics, it more importantly underscores that the public's assumptions about the benefits of probiotics are not well-founded, and there is also a major variation in results based on the formulation of the probiotic product," said guideline panel chair Dr. Grace L. Su, a gastroenterologist at the University of Michigan, in a news release.
Probiotics Helpful for Only Certain Conditions
Probiotics are live microorganisms that are intended to provide health benefits. Some probiotics are available by prescription in certain countries, but most are sold over the counter.
In the United States, probiotics marketed as dietary supplements don't need pre-approval from the Food and Drug Administration (FDA), but companies aren't allowed to make health claims about these products.
Although we sometimes think of bacteria as harmful "germs," our stomach and intestines actually contain millions of helpful bacteria and yeast. Together, they form a community known as the gut microbiome.
The human gut contains an estimated 300 to 500 different bacterial species. These interact in complex ways, both with each other and with the human body.
In addition to the guideline, the AGA released a technical review of existing scientific studies on the link between probiotics and gut health. This review found that probiotics may be beneficial for some GI (gut-related) conditions.
Certain probiotics may be helpful for preterm, low-birthweight infants — shortening the number of days they spend in the hospital and reducing the time for them to take full feeds.
Specific probiotics may also reduce the risk of Clostridium difficile infection in adults and children taking antibiotics. C. difficile is a bacterium that causes diarrhea and inflammation of the colon.
Likewise, the review found that certain probiotics may be helpful in the management of pouchitis, a complication of ulcerative colitis that has been treated surgically.
For other conditions, the review found that there was a shortage of scientific evidence to support the use of probiotics.
"Patients taking probiotics for Crohn's, ulcerative colitis or [irritable bowel syndrome] should consider stopping," said Su in the news release.
"The supplements can be costly and there isn't enough evidence to prove a benefit or confirm lack of harm."
The review also found that probiotics don't appear to be helpful for children with acute gastroenteritis, an inflammation of the digestive tract that can cause nausea, vomiting, and diarrhea.
However, the review only looked at research done in North America. Some research carried out in other countries has shown that certain probiotics were effective in reducing the duration of diarrhea in children with acute gastroenteritis.
Benefits Depend on Specific Probiotic Strains
One strength of the AGA's review is that it considered the effect of single-strain or multi-strain probiotics on gut health separately, rather than lumping them all together as "probiotics."
Dr. Daniel J. Merenstein, a professor of family medicine at Georgetown University, and his colleagues wrote recently in the Journal of Family Practice that the benefits of probiotics depend on the strain, dosage, and condition being treated.
"Just as we know that not all antibiotics are equally effective for all infections, so, too, effectiveness among probiotics can — and often does — vary for any given condition," they wrote.
"Effectiveness also may vary from patient to patient."
Interest in probiotics has grown as more research has shown how the gut microbiome can affect health, both negatively and positively.
This extends beyond GI health, with some studies finding a link between which bacteria are present in the gut and mental illnesses such as anxiety and depression.
However, most studies use specific single-strain or multi-strain probiotics — usually high-quality probiotics that aren't available over the counter. That's why taking "just any" probiotic may not be helpful.
Merenstein and his colleagues wrote that physicians recommending probiotics for their patients should look to the scientific evidence, where available, for which probiotics to use.
"Simply recommending that a patient 'take probiotics' is not particularly helpful when the individual wants a product that will aid a specific condition," they wrote.
While probiotics are generally safe, as living bacteria they can cause harm in some circumstances, especially in people with compromised immune systems. Anyone with a health condition should talk to their doctor before taking probiotics.
Some people use probiotics to improve their gut health, but research also shows that diet can modify the composition of the gut microbiome.
In particular, low-fat, high-fiber diets can have a beneficial effect, not just on the microbiome but also on your overall health — two aspects of your body that are intimately connected.
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By Joni Sweet
If you get a call from a number you don't recognize, don't hit decline — it might be a contact tracer calling to let you know that someone you've been near has tested positive for the coronavirus.
Interviews With Contact Tracers<p>Contact tracing is a public health strategy that involves identifying everyone who may have been in contact with a person who has the coronavirus. Contact tracers collect information and provide guidance to help contain the transmission of disease.</p><p>It's been used during outbreaks of sexually transmitted infections (STIs), Ebola, measles, and now the coronavirus that causes COVID-19.</p><p>It starts when the local department of health gets a report of a confirmed case of the coronavirus in its community and gives that person a call. The contact tracer usually provides information on how to isolate and when to get treatment, then tries to figure out who else the person may have exposed.</p><p>"We ask who they've been in contact with in the 48 hours prior to symptom onset, or 2 days before the date of their positive test if they don't have symptoms," said <a href="https://case.edu/medicine/healthintegration/people/heidi-gullett" target="_blank">Dr. Heidi Gullett</a>, associate director of the Center for Community Health Integration at the Case Western Reserve University School of Medicine and medical director of the Cuyahoga County Board of Health in Ohio.</p>
“You’ve Been Exposed”<p>After the case interview, contact tracers will get to work calling the folks who may have been exposed to the coronavirus by the person who tested positive.</p><p>"We give them recommendations about quarantining or isolating, getting tested, and what to do if they become sick. If they're not already sick, we still want them to self-quarantine so that they don't spread the disease to anyone else if they were to become sick," said Labus.</p><p>Generally, the contact tracer won't ask for additional contacts unless they happen to call someone who is sick or has a confirmed case of the virus. They will help ensure the contact has the resources they need to isolate themselves, if necessary. The contact tracer may continue to stay in touch with that person over the next 14 days.</p><p>"We follow the percentage of people that were contacts, then converted into being actual cases of the virus. It's an important marker to help us understand what kind of transmission happens in our community and how to control the virus," said Gullett.</p>
Why You Should Participate (and What Happens If You Don’t)<p>A <a href="https://www.thelancet.com/journals/laninf/article/PIIS1473-3099(20)30457-6/fulltext" target="_blank">Lancet study</a> from June 16, which looked at data from more than 40,000 people, found that COVID-19 transmission could be reduced by 64 percent through isolating those who have the coronavirus, quarantining their household, and contacting the people they may have exposed.</p><p>The combination strategy was significantly more effective than mass random testing or just isolating the sick person and members of their household.</p><p>However, contact tracing is only as effective as people's willingness to participate, and a small number of people who've contracted the coronavirus or were potentially exposed are reluctant to talk.</p><p>"Contact tracers have all been hung up on, cussed at, yelled at," said Gullet.</p><p>The hesitation to talk to contact tracers often stems from concerns over privacy — a serious issue in healthcare.</p>
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By James Shulmeister
Climate Explained is a collaboration between The Conversation, Stuff and the New Zealand Science Media Centre to answer your questions about climate change.
If you have a question you'd like an expert to answer, please send it to firstname.lastname@example.org
What was the climate and sea level like at times in Earth’s history when carbon dioxide in the atmosphere was at 400ppm?<p>The last time global carbon dioxide levels were consistently at or above 400 parts per million (ppm) was around <a href="https://www.nature.com/articles/nature14145" target="_blank">four million years ago</a> during a geological period known as the <a href="http://www.geologypage.com/2014/05/pliocene-epoch.html" target="_blank">Pliocene Era</a> (between 5.3 million and 2.6 million years ago). The world was about 3℃ warmer and sea levels were higher than today.</p><p>We know how much carbon dioxide the atmosphere contained in the past by studying ice cores from Greenland and Antarctica. As compacted snow gradually changes to ice, it traps air in bubbles that contain <a href="https://www.cambridge.org/core/journals/annals-of-glaciology/article/enclosure-of-air-during-metamorphosis-of-dry-firn-to-ice/09D9C60A8DA412D16645E6E6ABC1892F" target="_blank">samples of the atmosphere at the time</a>. We can sample ice cores to reconstruct past concentrations of carbon dioxide, but this record only takes us back about a million years.</p><p>Beyond a million years, we don't have any direct measurements of the composition of ancient atmospheres, but we can use several methods to estimate past levels of carbon dioxide. One method uses the relationship between plant pores, known as stomata, that regulate gas exchange in and out of the plant. The density of these stomata is <a href="https://journals.sagepub.com/doi/abs/10.1177/095968369200200109" target="_blank">related to atmospheric carbon dioxide</a>, and fossil plants are a good indicator of concentrations in the past.</p><p>Another technique is to examine sediment cores from the ocean floor. The sediments build up year after year as the bodies and shells of dead plankton and other organisms rain down on the seafloor. We can use isotopes (chemically identical atoms that differ only in atomic weight) of boron taken from the shells of the dead plankton to reconstruct changes in the acidity of seawater. From this we can work out the level of carbon dioxide in the ocean.</p><p>The data from four-million-year-old sediments suggest that <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2010PA002055" target="_blank">carbon dioxide was at 400ppm back then</a>.</p>
Sea Levels and Changes in Antarctica<p>During colder periods in Earth's history, ice caps and glaciers grow and sea levels drop. In the recent geological past, during the most recent ice age about 20,000 years ago, sea levels were at least <a href="https://science.sciencemag.org/content/292/5517/679.abstract" target="_blank">120 meters lower</a> than they are today.</p><p><span></span>Sea-level changes are calculated from changes in isotopes of oxygen in the shells of marine organisms. For the Pliocene Era, <a href="https://agupubs.onlinelibrary.wiley.com/doi/full/10.1029/2004PA001071" target="_blank">research</a> shows the sea-level change between cooler and warmer periods was around 30-40 meters and sea level was higher than today. Also during the Pliocene, we know the West Antarctic Ice Sheet was <a href="https://www.nature.com/articles/nature07867" target="_blank">significantly smaller</a> and global average temperatures were about 3℃ warmer than today. Summer temperatures in high northern latitudes were up to 14℃ warmer.</p><p>This may seem like a lot but modern observations show strong <a href="https://journals.ametsoc.org/jcli/article/23/14/3888/32547" target="_blank">polar amplification</a> of warming: a 1℃ increase at the equator may raise temperatures at the poles by 6-7℃. It is one of the reasons why Arctic sea ice is disappearing.</p>
Impacts in New Zealand and Australia<p>In the Australian region, there was no Great Barrier Reef, but there may have been <a href="https://link.springer.com/content/pdf/10.1007/BF02537376.pdf" target="_blank">smaller reefs along the northeast coast of Australia</a>. For New Zealand, the partial melting of the West Antarctic Ice Sheet is probably the most critical point.</p><p>One of the key features of New Zealand's current climate is that Antarctica is cut off from global circulation during the winter because of the big <a href="https://www.tandfonline.com/doi/abs/10.3402/tellusa.v54i5.12161" target="_blank">temperature contrast</a> between Antarctica and the Southern Ocean. When it comes back into circulation in springtime, New Zealand gets strong storms. Stormier winters and significantly warmer summers were likely in the mid-Pliocene because of a weaker polar vortex and a warmer Antarctica.</p><p>It will take more than a few years or decades of carbon dioxide concentrations at 400ppm to trigger a significant shrinking of the West Antarctic Ice Sheet. But recent studies show that <a href="http://nora.nerc.ac.uk/id/eprint/521027/" target="_blank">West Antarctica is already melting</a>.</p><p>Sea-level rise from a partial melting of West Antarctica could easily exceed a meter or more by 2100. In fact, if the whole of the West Antarctic melted it could <a href="http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.695.7239&rep=rep1&type=pdf" target="_blank">raise sea levels by about 3.5 meters</a>. Even smaller increases raise the risk of <a href="https://www.pce.parliament.nz/publications/preparing-new-zealand-for-rising-seas-certainty-and-uncertainty" target="_blank">flooding in low-lying cities</a> including Auckland, Christchurch and Wellington.</p>
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