Here’s your freak-out factoid for the day: There are 100 trillion cells that make up your body. But what percent are genuinely “you” and which are “others”—specifically, the microbes that live in your gut, on every square millimeter of your skin (a bit more so in the dark, damp spots), in your blood, on your hair and, especially, in your mouth? Answer: By cell count, it’s 10 percent you, 90 percent them.
To those microbes, you’re their planet. Most were born on you and will live their entire lives with you. And it’s a two-way relationship. Most of the microbes—which are made up of bacteria, viruses, some fungi and parasites—are harmless or even beneficial. The handful of bad microbes that inhabit humans (HIV, e.coli, salmonella, MRSA and gonorrhea, to name a few) are called pathogens, invaders that can make you sick and sometimes kill you.
Why we need microbes
According to a health report from Harvard Medical School, “The Truth About Your Immune System,” science has progressed significantly in recent years toward understanding the role that microbes play in our health. Ideally, your immune system learns to recognize which of these body invaders are friends and which are foes.
Good microbes in the human body provide us many benefits:
- Nutrients: Biotin (which helps maintain blood sugar levels, among other vital functions) and vitamin K (blood coagulation) are produced by gut flora (K also comes from leafy green vegetables). Fermentation from gut bacteria also produces acetic acid, which contributes to muscle development.
- Digestion: Bacteria in the gut produce enzymes necessary to break down some carbohydrates. Also, it can aid our absorption of calcium, magnesium and iron.
- Disease prevention: Some good bacteria help fight off the bad, pathogenic varieties.
This is why it is not uncommon to experience intestinal discomfort and diarrhea after a regimen of antibiotics. Humans’ overuse of antibiotics, and the extensive use of antibiotics in industrialized livestock practices, is believed to be altering and compromising human gut bacteria.
How we “catch” them
Over some nice family dinner in the near future, ask your mother if she delivered you vaginally or by Caesarian section. That way you’ll learn if you acquired your very first bacterium in the mess of fluids (including fecal matter) present in a natural birth. If you were born by C-section, you might have been more susceptible to infections, allergies and asthma, according to a study conducted by researchers at the University of Puerto Rico. But all infants also acquire microbes through contact with hospital personnel, fathers, family, household pets, friends and the surrounding environment during the first months of life.
Where do we get our bad pathogens, the bacteria and viruses that can make us ill? Here are some myths and facts, culled from the germy world:
Toilet seats vs. desks: According to Dr. Charles Gerba, a professor of environmental microbiology at The University of Arizona, office desktops, phones and computer keyboards and the mouse are “400 times more dirty than your toilet seat.” Hard to imagine? It’s worst for people who eat at their desks, where crumbs provide nutrients to insects and microbes. Still, it seems wrong to eat on a toilet seat.
Restaurants: Anyone who has ever worked in a restaurant knows how easy it is to inflict revenge on difficult customers. So the first rule is to always be nice to your server. But many restaurants make mistakes with cutting boards or have employees who do not heed hand-washing directives. The Centers for Disease Control advises to be particularly vigilant about how well meat and eggs are cooked. As a food microbiologist once told me, “everything is on everything; it’s all a matter of parts per billion (ppb).” The FDA sets standards for acceptable levels of fecal matter, for example, in everything from bottled water to eggs, juices, frozen and packaged foods. Try not to think about it.
The gym: “The Today Show” reporter Janice Lieberman went to two gyms in New York a few years ago with an environmental scientist who swabbed equipment, floors, locker room benches, showers, faucets and water fountains. It was shocking, shocking!, that she discovered various bacteria related to body functions in several locations. Notably, she did not report mass illnesses among members. So the germs are there—wash your hands, wear flip-flops in the shower and sit only on dry towels.
Sex: We all know about HIV prevention through safer sex practices (condoms, no blood exposures, etc.). Those same practices help reduce transmission of the bacteria that cause gonorrhea, Chlamydia and syphilis. Of note, the herpes virus is transmissible despite the use of condoms when the site of an infection is outside the condom region (e.g., on the mouth). Of course, bacteria exist in and around the anus—the flesh-eating bacteria (antibiotic-resistant MRSA) has been identified in several gay communities in recent years—such that handling a condom post-coitus can introduce the top to new microbes. Tip: Everyone take a nice, hot shower together, before and after, as recommended by Rick Sowadsky, MSPH with the Nevada State Health Division AIDS Program. It won’t prevent HIV or most other STDs, but it can reduce the risk of Giardia, Hepatitis A and other fecal infections.
What about immunity-boosting products, including probiotics? The Harvard report debunks the claims that over-the-counter products can strengthen your immunity. “The concept of boosting immunity actually makes little sense scientifically,” it says, noting that a complex and delicate balance of bacteria is something that cannot be accomplished by non-professionals. WebMD reports that bacteria-rich yogurts and kefirs are known to be effective only with children, and sometimes with adults, who have diarrhea.
How bacteria might make us fat
This might be taken way out of proportion, but it is an interesting scientific development.
A study out of the Emory University School of Medicine has found that healthy laboratory mice can be made fat mice when they are introduced to intestinal bacteria from fat lab mice. “Our results suggest that excess caloric consumption is not only a result of undisciplined eating but that intestinal bacteria contribute to changes in appetite and metabolism,” said senior author of the study, Andrew Gewirtz, Ph.D.
Transferring those findings onto humans, Gewirtz says, “This suggests that it’s possible to ‘inherit’ metabolic syndrome (tendency toward obesity) through the environment, rather than genetically. Maybe bacteria that increase appetite are playing a part.”
Note, that’s not license to go out and eat a whole pint of Ben & Jerry’s New York Super Fudge Chunk. The fat mice probably aren’t happy being fat. Try not to allow bacteria to be your destiny.
About Russ Klettke: Russ Klettke is a business, fitness and nutrition writer based in Chicago, and author of “A Guy’s Gotta Eat, the regular guy’s guide to eating smart” (with Deanna Conte, MS RD LD, Marlowe/DaCapo Press, 2004). He also is the anal-retentive chef when making chicken at home, which sometimes means using an elbow or chin to control the kitchen sink faucet.