CLINICAL

  NUTRITION

PAY ATTENTION TO YOUR GUT

A LOOK AT THE “SECOND BRAIN” AND HOW TO MAINTAIN ITS HEALTH

KIMBERLY K. REED, O.D., F.A.A.O.

LATELY AN explosion of health-related information about the billions of bacteria inhabiting the gut, also known as gut “flora” or, more precisely, the human microbiome (HMB), has been released. This incredibly intricate and complex system is responsible for so many processes that govern the human health ecosystem (neuroendocrine signaling, digestion and manufacturing of nutrients), that many experts have dubbed it the “second brain.”

Here is an overview of this system, its link with disease and what you can do to ensure your patients’ HMBs are healthy.

OVERVIEW

The HMB is comprised of the tens of billions of bacteria, viruses and fungi, along with their genetic material, that live in and on the human body.

Most of the HMB organisms are bacteria, and the majority are anaerobes living in the gastrointestinal tract. In each of us, these organisms weigh between 2 pounds to 6 pounds.

Great variability exists regarding the relative predominance of different species depending upon several factors, including age, nutrient intake, body mass and chaotic life events, such as major illness or intense periods of stress.

For example, patients who are obese tend to have a different HMB than those who are lean. It is unclear whether this is due to the foods commonly eaten or whether it is actually, in part, a cause of extra weight. Evidence exists to support both sides, and the “obese microbiome” is thought to allow more calories to be absorbed from food than a “lean microbiome.” More work is needed in this area, but it is a potential target for obesity management. In fact, several studies suggest that eating a protein- and plant-based diet can positively impact the gut environment to create a more lean HMB. Specifically, resveratrol may reduce inflammation in the gut and, thereby, provide a more healthful environment for friendly bacteria. In addition, probiotics containing Lactobacillus gasseri have been shown in some studies to be helpful for patients trying to lose weight, although not all studies report consistent findings. Finally, the ingestion of prebiotics, notably inulin, is also thought to promote a more hospitable environment for beneficial gut bacteria. Sudden increases in inulin intake can have the unpleasant side effect of increased gas, but this usually dissipates with regular use.

HMB AND DISEASE

When the HMB is out of balance, it is linked to a long list of diseases involving the digestive, neuro-endocrine, mood and affect and metabolic systems. In fact, antibiotic use can dramatically change the HMB within hours in that the elimination of “friendly” bacteria causes the bloating and diarrhea many people experience when taking a course of antibiotics. With regard to specific diseases, HMB has been linked with Crohn’s disease, uveitis, Alzheimer’s disease and autism, among others.

One aspect of the proposed mechanism in HMB-related disease pathogenesis is the interaction of the genetic material of these bacteria with human genes. Whether a certain gene that codes for a specific protein is turned “on” or “off” depends upon a variety of factors, collectively known as “epigenetics,” and the HMB has a powerful influence in this regard. Careful manipulation of the HMB by following specific dietary protocols like a ketogenic, gluten-free plan, as well as targeted pre- and probiotics has shown great promise in disease modulation and continues to be studied intensely.

ACHIEVING A HEALTHY HMB

For patients to achieve and maintain a healthy HMB, recommend a probiotic during and following a course of oral antimicrobial therapy. (A good way to explain probiotic ingestion: If we nourish and take care of vegetables, all is well. But if the vegetables are unhealthy, the weeds take over. Antibiotics “kill” both the vegetables and the weeds, so the probiotic protects the vegetables.) Next, coach patients to reduce, or better, eliminate sugar and processed/refined carbohydrates from their diets, as these substances are notorious for creating an adverse HMB, especially when eaten with fatty foods (cake with frosting, etc.). Instruct them to opt instead for plant-based foods with an emphasis on green leafy vegetables, moderate protein intake and adequate healthy fats. Finally, encourage patients to ask their primary care physicians about whether a specific probiotic, prebiotic, or “symbiotic” (combined pre- and probiotic) product would be beneficial. OM

DR. REED is a former professor at the NOVA Southeastern University College of Optometry in Fort Lauderdale, Fla., a member of the Ocular Nutrition Society and author of numerous articles on ocular nutrition, disease and pharmacology. She recently accepted a position with Shire Pharmaceuticals, which begins in January. To comment on this column, visit tinyurl.com/OMcomment.