Research shows strong associations between the types and amount of gut bacteria and chronic conditions such as diabetes and obesity. Many medical experts believe that genetics and lifestyle behaviors cause obesity and type 2 diabetes. However, there's a growing body of research examining the role of the intestinal microbiota as a potential contributor to the diabetogenic era.
Many scientists don't believe the changes in our diet and physical activity can account for the rising epidemic either. The trend among researchers is a newer belief in the role gut bacteria—the microbiota—that have changed and may be partially responsible in obesity, obesity-related inflammation, and insulin resistance, which leads to type 2 diabetes.
The gut microbiota are a densely populated and diverse collection of bacteria that are found in the intestines. In fact, there are 10 trillion to 100 trillion bacteria and other microscopic organisms living in our gut, with each person hosting at least 160 different species. Imagine that! Research suggests an interrelation between the different microbiota species that may work together for the benefit of the human body. Experts believe that a wide diversity of bacteria in the gut is beneficial. "We're just now starting to understand the role [the microbiota species] collectively play in our health, including diabetes, obesity, heart disease, and even cancer," says Kristi L. King, MPH, RDN, CNSC, LD, a senior pediatric dietitian at Texas Children's Hospital and spokesperson for the Academy of Nutrition and Dietetics. "Just as your kidneys are essential for creating urine, we're seeing how essential these bugs are for keeping us healthy. We know that without them, or [with] a significant imbalance, our health could suffer greatly."
Many factors shape our microbiota as it evolves throughout our lives. A baby's gut is sterile at birth, and the diversity of microbiota depends on how the child was delivered. Vaginal birth compared to cesarean section results in more diverse microbiota. Infants who are breast-fed have a greater diversity of microbiota than those fed infant formula. Nutrition, genetics, antibiotic use, diabetes, and even our environment shape our microbiota." According to the International Life Sciences Institute, "An increased proportion of Bifidobacteria and Lactobacilli is thought to represent a 'healthier' microbial composition."
Scientists are learning how manipulation of the gut microbiota could offer a new approach in the management of obesity and type 2 diabetes. Three modulators of gut microbiota—prebiotics, probiotics, and synbiotics—continue to garner interest as novel therapeutic agents.
1. Prebiotics are described as nondigestible substances that stimulate the growth or activity of potentially beneficial gut microbiota. The International Scientific Association of Probiotics and Prebiotics defines a prebiotic as "a selectively fermented ingredient that results in specific changes, in the composition and/or activity of the gastrointestinal microbiota, thus conferring benefit(s) upon host health." Studies show that prebiotics can increase the proportion of Bifidobacteria and Lactobacilli. Bifidobacteria is associated with improved health by inhibiting the growth of pathogenic bacteria, modulating the immune system, producing digestive enzymes, repressing the activities of rotaviruses, and restoring microbial integrity of the gut microbiota following antibiotic therapy. Inulin, for example, is naturally occurring in foods such as artichoke, asparagus, chicory, garlic, and onion. However, the amount of inulin in these foods doesn't reach the 5 to 8 g daily requirement needed to modulate gut microbiota. So functional food developers add inulin to products that are frequently consumed such as cereals, candy, pastries, biscuits, yogurts, and table spreads. The benefits of a high-fiber diet that includes whole grains, vegetables, fruits, and legumes are well established. As research on fibers with prebiotic properties continues, they can be recommended as part of daily fiber intake; however, it's important to encourage consumption of fiber from a variety of sources.
2. Probiotics are live bacteria that are either the same as or similar to the bacteria found naturally in the human body and may be beneficial to health. They're often referred to as "good bacteria" or "helpful bacteria." The Food and Agriculture Organization and the World Health Organization define probiotic bacteria as "live micro-organisms which, when administered in adequate amounts, confer a health benefit on the host." There is a growing body of clinical evidence showing that probiotics reduce inflammation, oxidative stress, and intestinal permeability, which can increase insulin sensitivity and reduce autoimmune response.
3. A symbiotic is formed when a probiotic and prebiotic are combined. Studies have shown that every probiotic benefits from a select number of carbohydrates. When prebiotics are selected based on their ability to stimulate the growth of the probiotic part, the effects of the probiotic are enhanced.Many products sitting on store shelves carry the label "probiotic," but all too often they don't meet qualifying criteria for probiotics, such as defined contents, viability at the end of shelf life, and evidence of health benefits. The International Scientific Association for Probiotics and Prebiotics recommended that the term "probiotic" be used only on those products that actually deliver live microorganisms with suitable viable counts of specific strains with an expectation of delivering health benefits.
As we learn more about the gut microbiota, we'll be able to individually tailor diets to help minimise or prevent symptoms of chronic disease. In the meantime, nutrition intervention strategies should emphasize healthful plant-based eating patterns that include fermented foods such as yogurt, kefir, sourdough bread, and kimchee.