Written by: Kelsey Schaffstall, Dietetic Intern for Hailey Crean Nutrition LLC

The gut has been receiving a lot of attention in research lately, and rightly so. ‘You are what you eat’ has taken on new meaning since scientists have discovered fascinating connections between diet, genetics, disease, and the microenvironment inside our gut.

What is the gut microbiome?

The gut microbiome, also called the gut microbiota, refers to the nearly five pounds of bacteria and microorganisms living inside the human gastrointestinal (GI) tract (1).  It is estimated that the number of bacteria in the gut is over 10x the number of cells in the human body. ‘Probiotics’ refer to the bacteria themselves, while ‘prebiotics’ refers to the high fiber foods that feed these bacteria, allowing them to survive and thrive. This vast community of bacteria can either help or harm you due to its complex role in digestion, vitamin synthesis, and metabolism (1). ‘Dysbiosis’ is a commonly used term to describe a disrupted gut microbiome, which could result in health problems.

What affects the gut microbiome?

A number of factors influence the bacteria in your gut including diet, disease, medications (especially antibiotics), and genetics (2).  Because of so many possible influences, the bacteria in your gut is constantly changing.  Some researchers have reported that diet has the largest influence on your gut bacteria, estimating that what you eat is responsible for 57% of your bacterial makeup (1).  This is striking considering that it is estimated that genetics only contribute to about 12% of the variations in gut bacteria between people (1).  One of the best examples of diet’s influence on gut bacteria is that significant differences are observed between the guts of breastfed vs. formula-fed infants (1).

What do we know so far?

A huge amount of research explores the link between the gut microbiome and metabolic diseases like obesity and diabetes. Findings have shown that certain types of bacteria can increase the amount of energy, or calories, taken from food, and cause chronic low-grade inflammation. Studies suggest that a high-fat Western diet can lead to dysbiosis, resulting in insulin resistance and metabolic disorders (2). Researchers have also found that diabetic subjects have different microbiota composition than similar healthy subjects (1).  Major differences identified in diabetics include a decrease in bacteria that produce butyrate, which is believed to decrease appetite, increase satiety, reduce insulin resistance, and improve lipid profiles (3).  While researchers have identified a number of possible links, there is still much to be discovered about exactly how the gut microbiome contributes to obesity and metabolic disorders.

Should I take a probiotic?

After reading all this, you’re probably wondering what the best probiotic supplement is. Not so fast- the science just isn’t quite there yet. While research has made huge progress on this topic, there isn’t a true consensus on what probiotic products are effective. Not to mention, they can also be pretty expensive. The American Gastroenterological Association’s (AGA) latest clinical practice guidelines reports that evidence is lacking in support of using probiotics in the management of most gastrointestinal diseases. The report also acknowledges the fact that most probiotic products on the shelves are not well understood, regulated, or proven to be effective contributing to confusion amongst consumers (4).

How can I improve my gut bacteria profile?

Since the diet is thought to have the largest influence on the gut microbiome, why not start there instead? Yogurt and kefir are easily accessible foods, filled with billions of probiotic bacteria, and their influence on the gut microbiome has been highly studied. Studies have shown that regular yogurt consumption is associated with weight loss, reduced inflammatory markers, and reduced risk of Type 2 Diabetes (2).  These beneficial effects are likely due to the beneficial lactic acid bacteria found in fermented dairy products, which have been shown protect to the lining of the gut, decrease enzymes released from harmful bacteria, and support the body’s innate immune response (2).   Prebiotic foods are also important to include in your diet in order to help your gut microbiome thrive. Choose a variety of high fiber whole grains, fruits, and vegetables with your gut health in mind. Some common prebiotic foods are oats, garlic, onion, cabbage, asparagus, artichokes, sweet potatoes, and bananas.

Take home message

Research in this area continues to evolve however what is becoming clear is that factors beyond macronutrient profile and calorie counts influence overall health outcomes. To help boost beneficial gut bacteria consider adding a probiotic food source and bulk up on prebiotic foods to help the helpful gut bacteria thrive!

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