Bacteria have a bad reputation, and you may spend hours protecting yourself and your family with anti-bacterial products. What you may not realize is that you are literally teeming with bacteria and other organisms too small to be seen with the naked eye. More than 100 trillion microbes occupy your body at any one time, and they serve as protectors as well as threats to your health.

Microbiome is the term for the community of bacteria and their genetic material living in your body. Scientists admit that they are a long way from understanding exactly how these microorganisms influence short- and long-term human health, but they know that the influence is strong. The National Microbiome Initiative was established in May of 2016 to expand our knowledge.

Yes, you should wash your hands frequently, particularly during flu and cold season when you might pick up and pass along bacteria that make you sick. After you use your hands to make a hamburger patty or prepare a chicken breast for cooking, you should also wash your hands promptly and thoroughly. Otherwise, you are likely to pick up bacteria such as E. coli that can cause food borne illness.

Some bacteria have a well deserved reputation. But any thought that you can or should wash your hands and body free of all bacteria should be banished from your mind.

The skin is itself part of the immune system, a barrier that protects the blood vessels and inner organs from harmful organisms.

It is also the part of our body that interacts with the outside world and, as a result, becomes colonized with numerous bacteria, viruses, fungi and other organisms. The vast majority of these organisms are harmless. Others protect us by fighting off more dangerous invaders or, in some cases, prompting the immune system to respond to a perceived threat.

Choosing Skin Environment

Your microscopic friends are a diverse lot. Some like skin folds; others prefer regions that are high (or low) in temperature and humidity. Your clothing,  cosmetics, moisturizers, lotions and soaps all influence these colonies of bacteria. If you are taking antibiotics or using antibacterial products, you will be affecting your skin bacteria, for better or worse.

Is it possible that some of your efforts to rid yourself of bacteria may be counter-productive? Some observational studies suggest that people living in super-clean environments are more vulnerable to certain inflammatory and autoimmune diseases. More research is needed to prove this “hygiene hypothesis.”

Our bodies, inside and out, become colonized with microorganisms during birth and immediately after. Vaginal birth babies have a higher bacterial count after one month compared to those born by caesarian section. Breast feeding also helps increase the number of bacteria. And all of this is considered highly important in promoting development of an effective immune system and preventing conditions such as eczema and asthma.

Family members have been found to have similar communities of bacteria, and this may account for similarities in body type and vulnerability to certain diseases, including diabetes. One study found that persons with a large number and a wide diversity of bacteria in their gastrointestinal systems had a lower rate of obesity and type 2 diabetes.

But your gut microbiome changes throughout life and is influenced by diet and lifestyle as well as by where you live and your close physical associates.

Smoking causes major changes in your gastrointestinal bacteria and has been linked to an increased risk of Crohn’s disease.

Stress may alter the gut microbiota; and, conversely, changes in the microbiota can have an effect on mood. Some research suggests that microbial changes associated with a poor diet may  worsen symptoms of depression.

One study found that professional athletes had greater diversity of gut bacteria than less active persons and that this benefit increased as they became more fit and followed a training diet.

You’re probably not thinking about your bacteria when you avoid smoking, exercise regularly or try to manage your stress. But they are involved in the process. Conversely, if you are sedentary or obese, you are changing the composition of your microbiome in a way that may make you more vulnerable to certain diseases or medical conditions.

Geography is also involved. Children in rural Africa and Venezuela have more diverse colonies of bacteria than children in the United States. On the other hand, Americans who travel to developing countries are at risk of picking up  gastrointestinal bacteria that result in short-term diarrheal illness and, sometimes, long-term bowel problems, including irritable bowel syndrome.

 When it comes to diet, it may be a two-way street. If you eat a high fat/high sugar diet, you are breeding microbes in your gut that thrive on that kind of diet and encourage you to feed them more of the same.

One study (2009) using mice that had been raised in a totally germ free environment, then injected with microorganisms from human fecal samples found that the number and type of microorganisms in the intestines could be changed in one day through a change in diet.

A later study (2014) replicated the results with humans. Comparing subjects eating only eggs, meat and cheese versus those eating only granola, lentils, fruits and vegetables, the researchers found that “the relative abundance of various bacteria species looked like it shifted within a day after the food hit the gut.”

To build a protective colony of intestinal bacteria, many experts recommend  prebiotics and probiotics.

Prebiotics are non-digestible food ingredients that resist stomach acids and absorption into the upper intestinal tract. They create short-chain fatty acids such as butyrate that may work against weight gain tendencies. Prebiotics are found in whole grains, fruits, root vegetables and legumes such as beans and lentils.

Probiotic foods contain beneficial bacteria. They include yogurt (without added sugar), cheese made from raw milk, kefir, lassi, sauerkraut, miso soup, soft cheese and sourdough bread.

Although the nutritional benefits of fiber are well established, there is, as yet, no solid evidence supporting the benefits of probiotics.

For better and worse, our microbiome reflects who we are–what we eat, what we inherited, where we live, the medications we have taken and our exercise habits. There is still much to be learned about the bacteria that inhabit our bodies, and there are no simple answers.

REFERENCES:

Eryn Blass, “The National Microbiome Initiative: fueling the discovery of the microscopic world around us,” Harvard University Graduate School of Arts and Sciences, July 20, 2016.

Geraldine O. Canny and Beth A. McCormick, “Bacteria in the intestine, helpful residents or enemies from within,” Infection and Immunity, August, 2008.

Michael A. Conlon and Anthony R. Bird, “The impact of diet and lifestyle on gut microbiota and human health,” Nutrients, January, 2015.

Sarah Dash, et al, “The gut microbiome and diet in psychiatry: focus on depression,” Current Opinion in Psychiatry, January, 2015.

Lawrence A. David, et al,  “Diet rapidly and reproducibly alters the human gut microbiome,” Nature, December 11, 2013.

Nathan Gray, “Diet can ‘rapid and reproducibly’ alter our gut bacteria: study,” Food Navigator, December 16, 2013.

Elizabeth E. Grice, “The skin microbiome,” Nature Reviews Microbiology, April 9, 2011.

David A. Johnson, “Enhancing the microbiome through diet, sleep, and exercise,” Medscape Gastroenterology, March 16, 2016.

David A. Johnson, M.D., “The gut microbiome’s role in nonalcoholic fatty liver disease,” Medscape Gastroenterology, November 19, 2015.

David A. Johnson, M.D., “The wide-ranging role of the microbiome,” Medscape Gastroenterology, September 15, 2015.

Tanya Lewis, “National Microbiome Initiative launched,” The Scientist, May 13, 2016.

Webb C. Reinoso, et al, “Protective and pro-inflammatory roles of intestinal bacteria,” Pathophysiology, June, 2016.

Tiny Hessman Saey, “Lawrence David’s gut check gets personal,” Science News, September 21, 2016.

“Skin bacteria could protect against disease,” ScienceDaily, November 11, 2016.

Michael W. Smith, M.D., “Probiotics and prebiotics: ask the nutritionist,” WebMD reviewed by Laura J. Martin , M.D.

Peter J. Turnbaugh, “The effect of diet on the human gut microbiome: a metagenomic analysis in humanized gnotobiotic mice,” Science Translational Medicine, November 11, 2009.

Ed Yong, “There is no ‘healthy microbiome,’” New York Times, November 1, 2014.