In biology class, when I was a child, I saw a movie showing some of the critters, magnified in horrifying detail, that inhabit our eyelashes, skin and scalp. I was disgusted, even though our teacher described them as harmless, even as she simultaneously played up their “ick” factor. I couldn’t stop scratching for a week. Not only are there tiny insects that live on our body, there is also a microbiome of bacteria, viruses and fungi that also call us home. Medical science is just now starting to realize that not only are they harmless, our bacterial co-inhabitants are beneficial for our health and are in fact critical to our well-being.
The average adult has between five and six pounds of bacteria living in her digestive tract alone. In fact there are ten times more bacterial cells living in the human body than there are human cells. These bacteria are not merely harmless inhabitants of our gut, but in fact help our bodies to function. We provide them with a home and food and they provide us with improved health and well-being, in the perfect symbiotic relationship (a relationship whereby organisms of a different species depend on and maybe even benefit each other).
Probiotics, which means “for life” in Greek, are the healthy bacteria that reside within us. They support the immune system by helping to fight off diseases and they assist in digesting food and synthesizing necessary vitamins required for metabolism. They may even provide psychological benefits to their host by reducing depression and anxiety and helping to control appetite.
Dr. Seth Bordenstein, a geneticist at Vanderbilt University, believes factors that drive evolution for humans may also impact and drive evolution for the symbiotic bacteria that inhabit us. He also believes that given the necessity of the microbiome for human well-being, it is likely that our symbiotic bacteria are as important as human genes in impacting human evolution. A growing body of evidence is showing that it is not only our human genes but also the genes of the trillions of microbes (bacteria, fungi and viruses) that live within each person that impact the functioning of our bodies.
Scientists, through their study of fruit flies, are starting to believe that having the right balance of bacteria in your gut can promote a longer and healthier life. Although there is lots more study that needs to be done on this very exciting hypothesis, it does provide all the incentive I need to keep my own personal gut bacteria in balance, healthy and thriving.
Feeding Our Healthy Gut Bugs
For those of us who are interested in promoting the healthy gut bugs that live within us, it’s not just a case of “don’t do this and don’t do that.” Not only should we stop doing certain things – stop getting stressed-out, stop taking antibiotics regularly and stop drinking alcoholic beverages, there are certain things that we should be doing more of to keep our beneficial gut bugs healthy and strong so that they can improve our health, well-being and even longevity. (Phew….this sounds like a lot of work!)
Certain types of foods, called prebiotics provide excellent sources of food for the beneficial gut bacteria that are cohabiting our bodies. Prebiotics are non-digestible carbohydrates that remain in your digestive tract that the probiotics eat. Eating a diet rich in prebiotics can help the healthy gut bacteria within your body grow and thrive. There are even prebiotics in breast milk. Mother’s milk contains oligosaccharides that babies cannot digest, but which provides food to the healthy bacteria found in their intestinal tracts.
Prebiotics are found in the following foods:
- whole grains (barley, rye, oats, flaxseed and other grains)
- beer (unpasteurized)
- maple syrup
- red wine
- dark, leafy vegetables such as spinach and kale
- legumes, such as red kidney beans and lentils
- other fresh fruits and vegetables
When prebiotics and probiotics are together in a nutritional supplement intended to stimulate the healthy bacteria in the large intestine, they are known as synbiotics. There are foods that are synbiotics, delivering both a probiotic (live bacteria) and the prebiotic food that it requires. Supplementing your diet with synbiotics can promote healthy intestinal flora.
Kefir is a milk drink to which kefir grains have been added and then fermented, making a synbiotic. Kefir has very high levels of probiotics and the friendly microbes that it contains have been shown to be effective at actually colonizing the gut. It contains a wider range of healthy of heathy strains of bacteria and yeasts than are found in yoghurt.
Many things that we commonly eat contain live bacteria (probiotics) that are terrific for us. Eating them can support the healthy colonization of your digestive tract by good bacteria.
During fermentation, yeast are added to a food to change its structure – sugars and starches are broken down during fermentation. Fermented food contains probiotics, often in quantities much higher than are found in probiotic supplements.
These foods contain good quantities of probiotics:
- Yoghurt (provided it contains live, active cultures – read the label to be sure)
- Buttermilk (uncooked only)
- Sourdough Bread
- Soft Cheese (either aged or containing raw (unpasteurized) milk)
- Cultured Cottage Cheese
- Miso (Japanese dish of fermented soy beans)
- Kombucha (fermented sweet tea drink)
- Tempeh (Indonesian fermented soybean patty)
- Sauerkraut (labeled as containing live cultures or unheated)
- Kimchi (Korean dish of fermented and pickled cabbage)
Food with Minimal Chemical Additives
Scientists are starting to suspect that chemicals added to our food, such as preservatives and other food additives including food dyes, can influence our gut microbiota. Preservatives work by killing bacteria and like antibiotics they don’t just kill the disease causing pathogens, they kill beneficial ones too. That preservatives might impact our gut microbiome makes sense to me – if preservatives prevent bacterial growth in food, isn’t it reasonable to think that they might also impact the bacteria living inside our intestinal tract as our bodies digestive the preservative containing food? Even the antibiotics and chemicals fed to livestock that are included in our food supply may have an effect. More research in this area will be helpful.
Eating a diet rich in sugar, fat and meat can impact the mix of gut bacteria, leading to a lower overall diversity of gut bacteria and a higher prevalence of bacteria associated with inflammation, allergy and obesity.
Eating fresh, relatively unprocessed food rich in whole grains, fruits and vegetables and fermented foods will help your gut microbiome to stay healthy and thrive. We are what we eat, but our gut bugs are what we eat, too. By nourishing and keeping them healthy, they will return the favor to us.
The following articles provide additional information on the topics discussed here:
- Here & Now on National Public Radio (September 10, 2013). Research Shows that Microbes are Crucial for our Health.
- The New York Times (June 18, 2012). Tending the Bodies’ Microbial Garden.
- Real Food University How to Make Your Own Probiotic Food.