Potential Benefits of Thumb-sucking and Nail-biting in a Too-Clean World

In a world of Lysol and Purell, it's easy to become all-consumed with keeping clean. And why not? We're on the go more than ever now:  we're working longer hours (1, 2), spending more time commuting (3), and we’re under constant pressure to keep up to date on all the available social media networks (4). No one has time to be slowed down with the flu or a cold. So we dab on a little hand sanitizer before we eat, clean our houses regularly with bleach-containing products, and hold our breath when someone sneezes in a crowded elevator (or maybe that's just me).

But is there such a thing as being too clean? Researchers who are focused on testing this so-called "hygiene hypothesis" think there may be.

 

The hygiene hypothesis proposes that living in a germ-free world is disadvantageous to our health. Studies testing the hygiene hypothesis have shown correlations between our squeaky-clean developed societies and increases in allergic conditions, compared to developing societies lacking modern infrastructures that support public health (5, 6). Some studies even point to differences in the levels of allergic conditions in cities versus rural towns within the same country (7). While such studies only suggest correlations, and don't definitively show clean environments cause a predisposition to allergies, their findings are worth considering.

While the biological explanation for the hygiene hypothesis is still being studied, evidence from such studies so far suggests that when our immune systems aren't regularly challenged by germs normally present in the environments we've been co-evolving with for millennia, the result is an immune system that is predisposed to allergic reactions. Our immune systems rely on a series of specialized cells programmed and primed to respond to different pathogenic and environmental challenges in a coordinated fashion:  for example, some cells respond to bacteria and viruses while others respond to parasites. Researchers investigating biological explanations for the hygiene hypothesis have proposed that a lack of exposure to bacteria and viruses in childhood causes a shift in the population of immune cells away from cells primed and ready to attack those germs and instead toward a population of cells programed to respond to allergic stimuli (6).

Of course being clean is a good thing. An awareness of how diseases spread and how to take precautions against them is one of the reasons why modern society has been able to flourish. Hand washing and sterilization techniques introduced in the 1800s by Dr. Ignaz Semmelweis dramatically reduced a common cause of death in maternity wards (9). Modern epidemiology enables us to learn and track how certain diseases can be spread (including the recent outbreak of E. coli in flour) so we can take preventative measures to avoid further spread of diseases. We're careful to cook our food thoroughly to avoid food borne illnesses like salmonellosis. All of these behaviors protect us from unwanted illnesses, and allow us to carry on with our lives. While we certainly don't want to undo all of the advances we've made in limiting the spread of disease, evidence suggests that there needs to be a balance between being too dirty and too clean.

A line of souvenirs at Disney parks last summer included hand sanitizers featuring popular kids characters. Image from https://disneyparks.disney.go.com/blog/2015/08/summer-of-souvenirs-continues-with-new-items-at-disney-parks/

For example, it was recently published in the journal Pediatrics (8) that thumb-sucking and nail-biting, generally thought of as being unsanitary, may help children avoid developing environmental allergies. The results came out of the Dunedin Multidisciplinary Study, in which researchers followed over 1,000 children born in Dunedin, New Zealand between 1972 and 1973 throughout adulthood. For this particular question, children were first examined at ages 5, 7, 9, and 11 and then tested for certain allergies at 13 and 32 years of age. The researchers conducting this study, Stephanie Lynch and Dr. Robert Hancox (from the University of Otago, New Zealand), and Dr. Malcolm Sears (McMaster University and St Joseph’s Healthcare, Ontario, Canada), found that the individuals who had been frequent thumb-suckers or nail-biters as children tested positive for allergic sensitivities less often than those who had not frequently engaged in those habits. More specifically, the researchers report that 49% of participants who had not been frequent thumb-suckers or nail-biters had positivity allergy tests, whereas only 31% of participants who had sucked their thumbs and bit their nails as young children had positive allergy tests. 

Granted, this is only one study and it's still probably not a good idea to advocate for children keeping their dirty hands in their mouths all of the time. After all, no one wants their child to be sick. But perhaps thumb-sucking is one thing parents don't have to worry about so much after all. Perhaps instead, we can trust that our bodies are designed to deal with those little germ and dirt exposures, and maybe even benefit from them in the long run.

http://peanuts.wikia.com/wiki/%22Pig-Pen%22

Contributed by:  Kelly Hallstrom

Follow Kelly on Twitter.

1. http://abcnews.go.com/US/story?id=93604&page=1

2. https://www.theguardian.com/business/2016/mar/27/britons-working-longer-hours-with-no-gain-in-productivity-study-finds

3. https://www.washingtonpost.com/news/wonk/wp/2016/02/25/how-much-of-your-life-youre-wasting-on-your-commute/

4. http://www.dummies.com/how-to/content/ways-to-stay-uptodate-with-social-media-changes.html

5. http://www.ncbi.nlm.nih.gov/pubmed/9643741

6. http://www.ncbi.nlm.nih.gov/pubmed/11964470

7. http://www.ncbi.nlm.nih.gov/pubmed/9228959

8. http://pediatrics.aappublications.org/content/early/2016/07/07/peds.2016-0443

9. http://www.npr.org/sections/health-shots/2015/01/12/375663920/the-doctor-who-championed-hand-washing-and-saved-women-s-lives

Pull Up A Stool And Let's Talk About Your Microbiome

A medical case report recently made headlines supporting the notion that the bacteria inside our gut have something to do with the size of our gut.

Clostridium is a nasty strain of bacteria that is resistant to many antibiotics. Normally, the many other species of bacteria in the gut keep Clostridium in check, but when those friendly bacteria are wiped out during antibiotic therapy, Clostridium can thrive and produce severe inflammation (colitis) and diarrhea. This can develop into a serious illness that claims the lives of 14,000 Americans every year.

A novel way to treat this condition is through use of fecal microbiota transplant (FMT). In other words, the patient ingests the intestinal bacteria from a healthy person to replenish their own stock and get Clostridium back under control. We will leave it to your imagination as to how doctors collect the good bacteria, but let's just say you can make some decent money if you're willing and able to donate. Thankfully for patients, FMT is available in pill form.

As unappealing as it sounds, fecal transplants - which repopulate intestinal bacteria in the recipient - are proving to be very effective in treating some serious ailments. 

As reported recently, a young woman with a stable weight of ~130 pounds had to undergo FMT to fight a Clostridium infection. The good news is that she beat the infection, but the bad news is that she gained 34 pounds in 16 months, classifying her as obese with a BMI of 33. Even more alarming is that she could not lose weight despite being on a supervised liquid diet and exercise program. The donor for the FMT (her teen daughter) was overweight, but otherwise in good health, so doctors are now recommending that FMT donors be of normal weight.

In light of this news, here's a beginner's guide to the tiny creatures calling you "home"...

You are not just a person – you are an ecosystem. Your body is home to trillions of microscopic critters, including viruses, bacteria, and fungi, living on or inside you. Collectively, these communities of microbes constitute what is called your “microbiome”.

And there are more of “them” than “you” – the number of microbes inhabiting your body is larger than the number of cells making up your body! To put this in perspective, it has been estimated that your microbiome weighs about 3 pounds. Good news if you’re on a diet – when you step on the scale tonight, feel free to subtract 3 pounds of stuff that isn’t “you” per se.

A new study concerning our microbiome seems to be coming out each week, so it is time we get to know our microbial roommates.

1. Where does your microbiome come from?

We are born virtually sterile, but quickly receive an infusion of bacteria from our mom, first through the birth canal and then through the milk. Over 900 species of bacteria have been found in breast milk, and these are the pioneers that settle into your gut, which appears to stabilize by the age of 3. Of potential interest are babies born by caesarean section or those who are fed formula instead of breast milk. Babies delivered via C-section do in fact have a different microbiome and may be at higher risk for certain types of allergies and obesity (more on this below). Our microbiome continues to receive fresh new imports as we move through, inhale, and ingest our environment.

How much of you is really you? There are more microbes in your body than the number of cells making up your body. We are just now beginning to appreciate the many things they do for us.

2. Your microbiome is like your own personal “germ cloud”.

You’ve probably noticed that everyone’s home smells a little different. Sometimes this is due to cooking, pets, or the amount of trash they let accumulate, but it is also due in part to the microbiome of the inhabitants. Researchers have found that you are surrounded by a “germ cloud”, and you leave pieces of your microbiome wherever you go like a trail of breadcrumbs. It might even be possible for police to use microbiomes to track people one day like they currently use fingerprints or DNA. In other words, you have a “microbiome fingerprint” that is left behind like a germ echo wherever you go.

This “germ cloud” may also explain how dogs can track people so easily. The byproducts generated by the millions of bacteria living on your skin are aromatic (odorous), producing a scent that is released into the air as you move. Animals with a keen sense of smell can get a whiff of these aromatic compounds and follow them to the source.

Speaking of “germ clouds”, if you ever wondered if it is possible to fart out germs, some brave scientists have sniffed out the answer to this question. You can read about the results here.

3. Antibiotics substantially alter your microbiome.

We take antibiotics to get rid of pathogenic bacteria that make us sick. The problem is they are not selective, so they destroy a lot of our friendly bacteria in addition to the bad guy. We need these friendly bacteria to do all sorts of things – to name just a few:  they help us digest food, make vitamins, and build anti-inflammatory compounds.

Another important thing our microbial friends do is keep infections in check. For example, yeast infections from pathogenic fungi can arise if good bacteria are not around competing for resources. And some bacteria, like the nasty Clostridium difficile, are naturally resistant to many antibiotics. When good bacteria are killed as collateral damage in an antibiotic treatment, the growth of Clostridium can run amok. These bacteria secrete a toxin that causes diarrhea and they can lead to a life-threatening superinfection in some patients.

4. Your microbiome may protect you from allergies or obesity.

Several recent studies have correlated unusual microbiome composition with the presence of certain allergies. Dr. Hans Bisgaard has shown that infants harboring fewer species of gut bacteria have an increased risk of developing certain allergies as they grow up. More recently, Dr. Catherine Nagler has shown that certain bacterial species offer protection from peanut allergies.

Dr. Martin Blaser has found that administration of penicillin to mice soon after birth altered their gut microbiome in such a way that it made them more prone to obesity as adults. Remarkably, the tendency to grow obese is transferrable to germ-free mice – in other words, by transplanting the microbes from the penicillin treated mice to normal mice made the normal mice more susceptible to weight gain.

Studies such as these make it tantalizing to speculate that we may be able to treat certain ailments in humans by altering our microbiome with specific probiotic regimens. Maybe they could even slip these bacteria into our peanut butter instead of deadly Salmonella.

5. How do scientists study the microbiome?

Advances in DNA sequencing have allowed scientists to rapidly map the genomes for many microbial species, which provides us with a “genomic fingerprint”. We can process samples swabbed from the skin or body cavities, or process stool samples, for DNA sequencing. Usually just sequencing the 16S ribosomal RNA gene is enough to distinguish one bacteria species from another.  

It should be mentioned that some scientists are issuing cautions about over-interpreting microbiome studies. Many of the studies altering the microbiome have been performed in mice, so it remains to be determined to what extent the findings can be extrapolated to humans. Furthermore, many of the methods used to alter the microbiome in lab animals do not faithfully mimic what humans do with antibiotics. For example, in some studies the investigators give large doses of antibiotics over unusually long periods of time to see an effect in lab animals, which does not equate to the typical dosing of antibiotics in humans. Finally, many of these studies are correlative and have not yet definitively demonstrated causation. There is a big difference between correlation and causation.

6. So should I take my microbiome into my own hands?

Much more research needs to be done to assess the true impact of the microbiome versus other factors that come into play, such as host genetics, diet, and the environment. It is argued that some microbiome studies are hyped up and way overblown. Long story short:  if you or your child becomes sick with an infectious agent, it is not wise to withhold antibiotic treatment out of fear that it will cause allergies or obesity. If you are overweight, a healthier diet and plenty of exercise is going to do much more than any probiotic pill. In fact, there is little evidence that the popular probiotics on the market do anything to remedy the wide-ranging health problems some claim to treat, although there is data showing potential benefit in treating some gastrointestinal maladies, especially acute diarrhea caused by rotavirus.

Go here to learn more about the NIH human microbiome project.

Contributed by:  Bill Sullivan, Ph.D.

Follow Bill on Twitter.

Lax S, Smith DP, Hampton-Marcell J, Owens SM, Handley KM, Scott NM, Gibbons SM, Larsen P, Shogan BD, Weiss S, Metcalf JL, Ursell LK, Vázquez-Baeza Y, Van Treuren W, Hasan NA, Gibson MK, Colwell R, Dantas G, Knight R, & Gilbert JA (2014). Longitudinal analysis of microbial interaction between humans and the indoor environment. Science (New York, N.Y.), 345 (6200), 1048-52 PMID: 25170151

Bisgaard, H., Li, N., Bonnelykke, K., Chawes, B., Skov, T., Paludan-Müller, G., Stokholm, J., Smith, B., & Krogfelt, K. (2011). Reduced diversity of the intestinal microbiota during infancy is associated with increased risk of allergic disease at school age Journal of Allergy and Clinical Immunology, 128 (3), 646-65200000 DOI: 10.1016/j.jaci.2011.04.060

Cox, L., Yamanishi, S., Sohn, J., Alekseyenko, A., Leung, J., Cho, I., Kim, S., Li, H., Gao, Z., Mahana, D., Zárate Rodriguez, J., Rogers, A., Robine, N., Loke, P., & Blaser, M. (2014). Altering the Intestinal Microbiota during a Critical Developmental Window Has Lasting Metabolic Consequences Cell, 158 (4), 705-721 DOI: 10.1016/j.cell.2014.05.052

Stefka, A., Feehley, T., Tripathi, P., Qiu, J., McCoy, K., Mazmanian, S., Tjota, M., Seo, G., Cao, S., Theriault, B., Antonopoulos, D., Zhou, L., Chang, E., Fu, Y., & Nagler, C. (2014). Commensal bacteria protect against food allergen sensitization Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1412008111

Williams NT (2010). Probiotics. American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists, 67 (6), 449-58 PMID: 20208051

Alang, N., & Kelly, C. (2015). Weight Gain After Fecal Microbiota Transplantation Open Forum Infectious Diseases, 2 (1) DOI: 10.1093/ofid/ofv004

Attack Of The Germs!

No one likes being sick, especially with the flu. The body aches, the fevers, and the congestion all leave us desperate for ways to end the misery. Indeed, it’s growing increasingly hard to ignore the commercials telling us to stock up on flu-fighting products, like disinfectants and hand sanitizers. But how much do these items really help you avoid becoming the flu’s next victim, and do they have other consequences that we should be aware of?

Let’s first take a look at how many of the popular disinfectants work. Cleaners like Lysol have different types of salts in them that kill germs by disrupting important protein interactions, which causes the pathogen to stop functioning normally. These salts can also work by breaking up the membrane that surrounds bacteria and some viruses, essentially breaking open the pathogen and causing everything inside it to leak out. In both of these cases, the germs stop growing or are killed altogether.

Alcohol-based hand sanitizers work in a similar manner. At concentrations of at least 60%, ethyl alcohol (or ethanol) is effective at killing some viruses, including influenza viruses. Ethanol works by changing the shape of proteins, and therefore interferes with their ability to properly interact with other proteins. Ethanol can also disrupt membranes.

 

Image of Influenza virus from the CDC highlighting proteins on the outer surface that help the virus infect cells, and the viral genome located inside.

While killing off the germs that can make us sick sounds like a good way to stay healthy, the problem with using disinfectants and sanitizers to do this is that these products kill nearly all of the microbes in our environment. While there are many microbes that make us sick, there are also many that we need to help keep us healthy. If we kill those microbes off too, then we may put ourselves at risk for developing other health problems. 

On and within our bodies live millions and millions of good microbes that do things from helping us digest food, to helping keep bad microbes out of our bodies. These good microbes encompass the population known as the microbiome. The microbiome populations shift depending on the location of the body. For example, we have good bacteria that live on our skin, the population of which differs from the population of good bacteria that live in our digestive tracts. There is increasing interest in exploring the functions of the different microbiome populations, and many studies are showing that the microbiome has important roles in keeping us healthy. For example, it is thought that irregularities in the gut microbiome population may have a role in some inflammatory bowel diseases like Crohn’s disease and ulcerative colitis. It is possible that killing off the beneficial microbes in and on our bodies counteracts any good effect from killing off germs.

 

Keeping our good microbes around is only part of the story. According to the CDC, we are currently on the brink of a public health crisis due to the increasing numbers of microbes that are becoming resistant to common antibiotics. Due to our overuse and misuse of antibiotics, we have created strains of bacteria that are no longer susceptible, or able to be killed, by standard treatments. As bacteria populations are constantly exposed to antibiotics, many of those bacteria will be killed because they are sensitive to the antibiotic, but there will be some that are naturally able to withstand the actions of the antibiotic. Eventually, the population of bacteria that was initially a mix of sensitive and resistant will transition to a population of bacteria that is completely resistant, as all of the susceptible bacteria are killed off. What is the impact on us? In 2013, the CDC reported that at least 2 million people in the United States become infected with antibiotic-resistant bacteria, and that at least 23,000 of these people die from their infections.

Perhaps the most well-known case is MRSA, or methicillin-resistant Staphylococcus aureus. Staph bacteria are common and normally cause minor skin infections; however, MRSA has been highlighted in the media several times over recent years due to the outbreaks of invasive infections it has caused due to its resistance to standard antibiotics. MRSA is but one example of the bacterial strains that develop resistance to antibiotics due to constant exposure to them.

As we continue the cycle of overuse and misuse of antibiotics, we eventually will find ourselves at a point where no antibiotics will be effective against bacterial pathogens. Many public health experts suspect that point is near. There is reason to believe that constant use of disinfectants will eventually lead to the development of germs that are resistant to those disinfectants, just as we see happening with bacteria and antibiotics.

So how do we keep ourselves healthy without potentially setting ourselves up for other health problems later? We can start by limiting our use of disinfectants, and go back to simpler, tried-and-true methods of preventing the spread of communicable diseases. Despite the popularity of disinfectants and hand sanitizers, the CDC still maintains that hand-washing is one of the best ways to avoid spreading and catching viral and bacterial infections from others. Wash your hands before you eat, and avoid touching your hands to your eyes and nose.  If you are sick, do your best to sneeze or cough into the crook of your elbow (i.e., do the “Dracula sneeze”) rather than into your hands, and wash your hands frequently to avoid spreading your germs to others.

 

Of course, use soap that does not contain antimicrobial additives, like triclosan, to avoid encouraging the development of strains resistant to this compound. Soap is a potent killer of germs all by itself - it does not need supplemental antibiotics. While some companies are moving away from including triclosan, it is still present in many products, so be sure to check your labels.

Disinfectants have their place; they’re good for cleaning up food preparation areas that have come into contact with raw meat, for example. And, in times when you’re without clean water and soap, hand sanitizer can be a great tool for keeping your hands clean. But as with most things in life, these items should be used with care and arguably in balance with other washing methods in order to avoid creating greater problems down the line.

Contributed by:  Kelly Hallstrom
Visit Kelly’s blog, You Don’t Have To Be A Rocket Scientist
Follow Kelly on Twitter.

 

CDC Threat Report on Drug-Resistant Bacteria:

http://www.cdc.gov/drugresistance/threat-report-2013/

CDC and hand washing:

http://www.cdc.gov/handwashing/

 

Greenblum, S., Turnbaugh, P., & Borenstein, E. (2011). Metagenomic systems biology of the human gut microbiome reveals topological shifts associated with obesity and inflammatory bowel disease Proceedings of the National Academy of Sciences, 109 (2), 594-599 DOI: 10.1073/pnas.1116053109

6 Things You Need To Know About Your Microbiome

You are not just a person – you are an ecosystem. Your body is home to trillions of microscopic critters, including viruses, bacteria, and fungi, living on or inside you. Collectively, these communities of microbes constitute what is called your “microbiome”.

And there are more of “them” than “you” – the number of microbes inhabiting your body is larger than the number of cells making up your body! To put this in perspective, it has been estimated that your microbiome weighs about 3 pounds. Good news if you’re on a diet – when you step on the scale tonight, feel free to subtract 3 pounds of stuff that isn’t “you” per se.

A new study concerning our microbiome seems to be coming out each week, so it is time we get to know our microbial roommates.

1. Where does your microbiome come from?

We are born virtually sterile, but quickly receive an infusion of bacteria from our mom, first through the birth canal and then through the milk. Over 900 species of bacteria have been found in breast milk, and these are the pioneers that settle into your gut, which appears to stabilize by the age of 3. Of potential interest are babies born by caesarean section or those who are fed formula instead of breast milk. Babies delivered via C-section do in fact have a different microbiome and may be at higher risk for certain types of allergies and obesity (more on this below). Our microbiome continues to receive fresh new imports as we move through, inhale, and ingest our environment.

How much of you is really you? There are more microbes in your body than the number of cells making up your body. We are just now beginning to appreciate the many things they do for us.

2. Your microbiome is like your own personal “germ cloud”.

You’ve probably noticed that everyone’s home smells a little different. Sometimes this is due to cooking, pets, or the amount of trash they let accumulate, but it is also due in part to the microbiome of the inhabitants. Researchers have found that you are surrounded by a “germ cloud”, and you leave pieces of your microbiome wherever you go like a trail of breadcrumbs. It might even be possible for police to use microbiomes to track people one day like they currently use fingerprints or DNA. In other words, you have a “microbiome fingerprint” that is left behind like a germ echo wherever you go.

This “germ cloud” may also explain how dogs can track people so easily. The byproducts generated by the millions of bacteria living on your skin are aromatic (odorous), producing a scent that is released into the air as you move. Animals with a keen sense of smell can get a whiff of these aromatic compounds and follow them to the source.

Speaking of “germ clouds”, if you ever wondered if it is possible to fart out germs, some brave scientists have sniffed out the answer to this question. You can read about the results here.

3. Antibiotics substantially alter your microbiome.

We take antibiotics to get rid of pathogenic bacteria that make us sick. The problem is they are not selective, so they destroy a lot of our friendly bacteria in addition to the bad guy. We need these friendly bacteria to do all sorts of things – to name just a few:  they help us digest food, make vitamins, and build anti-inflammatory compounds.

Another important thing our microbial friends do is keep infections in check. For example, yeast infections from pathogenic fungi can arise if good bacteria are not around competing for resources. And some bacteria, like the nasty Clostridium difficile, are naturally resistant to many antibiotics. When good bacteria are killed as collateral damage in an antibiotic treatment, the growth of Clostridium can run amok. These bacteria secrete a toxin that causes diarrhea and they can lead to a life-threatening superinfection in some patients.

4. Your microbiome may protect you from allergies or obesity.

Several recent studies have correlated unusual microbiome composition with the presence of certain allergies. Dr. Hans Bisgaard has shown that infants harboring fewer species of gut bacteria have an increased risk of developing certain allergies as they grow up. More recently, Dr. Catherine Nagler has shown that certain bacterial species offer protection from peanut allergies.

Dr. Martin Blaser has found that administration of penicillin to mice soon after birth altered their gut microbiome in such a way that it made them more prone to obesity as adults. Remarkably, the tendency to grow obese is transferrable to germ-free mice – in other words, by transplanting the microbes from the penicillin treated mice to normal mice made the normal mice more susceptible to weight gain.

Studies such as these make it tantalizing to speculate that we may be able to treat certain ailments in humans by altering our microbiome with specific probiotic regimens. Maybe they could even slip these bacteria into our peanut butter instead of deadly Salmonella.

5. How do scientists study the microbiome?

Advances in DNA sequencing have allowed scientists to rapidly map the genomes for many microbial species, which provides us with a “genomic fingerprint”. We can process samples swabbed from the skin or body cavities, or process stool samples, for DNA sequencing. Usually just sequencing the 16S ribosomal RNA gene is enough to distinguish one bacteria species from another.  

It should be mentioned that some scientists are issuing cautions about over-interpreting microbiome studies. Many of the studies altering the microbiome have been performed in mice, so it remains to be determined to what extent the findings can be extrapolated to humans. Furthermore, many of the methods used to alter the microbiome in lab animals do not faithfully mimic what humans do with antibiotics. For example, in some studies the investigators give large doses of antibiotics over unusually long periods of time to see an effect in lab animals, which does not equate to the typical dosing of antibiotics in humans. Finally, many of these studies are correlative and have not yet definitively demonstrated causation. There is a big difference between correlation and causation.

6. So should I take my microbiome into my own hands?

Much more research needs to be done to assess the true impact of the microbiome versus other factors that come into play, such as host genetics, diet, and the environment. It is argued that some microbiome studies are hyped up and way overblown. Long story short:  if you or your child becomes sick with an infectious agent, it is not wise to withhold antibiotic treatment out of fear that it will cause allergies or obesity. If you are overweight, a healthier diet and plenty of exercise is going to do much more than any probiotic pill. In fact, there is little evidence that the popular probiotics on the market do anything to remedy the wide-ranging health problems some claim to treat, although there is data showing potential benefit in treating some gastrointestinal maladies, especially acute diarrhea caused by rotavirus.

Go here to learn more about the NIH human microbiome project.

Contributed by:  Bill Sullivan, Ph.D.

Follow Bill on Twitter.

Lax S, Smith DP, Hampton-Marcell J, Owens SM, Handley KM, Scott NM, Gibbons SM, Larsen P, Shogan BD, Weiss S, Metcalf JL, Ursell LK, Vázquez-Baeza Y, Van Treuren W, Hasan NA, Gibson MK, Colwell R, Dantas G, Knight R, & Gilbert JA (2014). Longitudinal analysis of microbial interaction between humans and the indoor environment. Science (New York, N.Y.), 345 (6200), 1048-52 PMID: 25170151

Bisgaard, H., Li, N., Bonnelykke, K., Chawes, B., Skov, T., Paludan-Müller, G., Stokholm, J., Smith, B., & Krogfelt, K. (2011). Reduced diversity of the intestinal microbiota during infancy is associated with increased risk of allergic disease at school age Journal of Allergy and Clinical Immunology, 128 (3), 646-65200000 DOI: 10.1016/j.jaci.2011.04.060

Cox, L., Yamanishi, S., Sohn, J., Alekseyenko, A., Leung, J., Cho, I., Kim, S., Li, H., Gao, Z., Mahana, D., Zárate Rodriguez, J., Rogers, A., Robine, N., Loke, P., & Blaser, M. (2014). Altering the Intestinal Microbiota during a Critical Developmental Window Has Lasting Metabolic Consequences Cell, 158 (4), 705-721 DOI: 10.1016/j.cell.2014.05.052

Stefka, A., Feehley, T., Tripathi, P., Qiu, J., McCoy, K., Mazmanian, S., Tjota, M., Seo, G., Cao, S., Theriault, B., Antonopoulos, D., Zhou, L., Chang, E., Fu, Y., & Nagler, C. (2014). Commensal bacteria protect against food allergen sensitization Proceedings of the National Academy of Sciences DOI: 10.1073/pnas.1412008111

Williams NT (2010). Probiotics. American journal of health-system pharmacy : AJHP : official journal of the American Society of Health-System Pharmacists, 67 (6), 449-58 PMID: 20208051

The Friday Five

Highlighting some of the coolest science news we’ve seen lately.

1. Birds of a feather really do flock together. A recent study finds that you and your friends have similar DNA.

2. Can science help us understand our political differences? Experiments in this new study show that conservatives respond significantly more rapidly to threatening stimuli.

3. You won’t believe the camouflage this gecko is capable of. The only thing better is its name:  the satanic leaf-tailed gecko.

4. Ivan Seah Yu Jun explains Alzheimer’s disease in under 5 minutes in this TED video.

5. So your friends scoff when you rather fist bump than handshake. Now science has justified your action. Fist bumps are the best way to greet someone without adopting their germs.

Science quote of the week:

"All the conditions of happiness are realized in the life of the man of science." –Bertrand Russell 

Contributed by:  Bill Sullivan

Follow Bill on Twitter: @wjsullivan

Hibbing, J., Smith, K., & Alford, J. (2014). Differences in negativity bias underlie variations in political ideology Behavioral and Brain Sciences, 37 (03), 297-307 DOI: 10.1017/S0140525X13001192

Christakis, N., & Fowler, J. (2014). Friendship and natural selection Proceedings of the National Academy of Sciences, 111 (Supplement_3), 10796-10801 DOI: 10.1073/pnas.1400825111