Talking Gut-Brain Axis Nutrition With NOWโ€™s Neil Levin

Vitamin Retailer (VR) reached out to Neil E. Levin, CCN, DANLA, senior nutrition education manager for Bloomingdale, IL-based NOW,

VR: We now know that there is a bi-directional relationship between the brain and the gut, critically involving the vagus nerve, in this way connecting the 100 billion neurons in the brain with the 500 million neurons in the gut. How important is the gut-brain axis, and why?

Levin: In the past, researchers have underestimated the role of the gut in emotional and mental well-being. This is partially because doctors thought that GI disturbances were often the result of emotional problems and other stresses, or even psychosomatic; but today the thinking has shifted to consider gut problems themselves as a potential trigger for mood changes. Johns Hopkins Medicine has stated that between 30% and 40% of the population has functional bowel problems at some point in their lives. Harvard Medical reports that the connection between the brain and the gut โ€“ the stomach and intestines โ€“ is a bi-directional circuit wherein a troubled brain can send signals downward and a troubled intestine can send signals upward. The signals can be chemical or hormonal.

So, if a person experiences stomach or intestinal distress, it can be either a cause or a symptom of stress and mood issues. But when these GI issues have no apparent cause, it is reasonable to look to the central nervous system in the brain for emotional and mood problems as the trigger.

There is also evidence that digestive system activity can affect thinking skills and memory, which is a topic of research at Johns Hopkins and elsewhere. Various probiotic strains have been shown to both interact with this part of the nervous system and to interact with gut hormones and nerve signals for a much broader effect on metabolism and body chemistry than was previously known. Nerves in the gut area also affect body systems, including metabolism and blood sugar.

VR: Gut bacteria that affect the brain, along with mood and stress, are often referred to as โ€œpsychobiotics.โ€ Please elaborate, give a product example; what has the best science?

Levin: It is almost a given that, โ€œbad stomach, bad mood.โ€ However, I may disagree with some of my colleagues over whether one or two specific probiotic strains have as much benefit as straightening out the microbiome via both diet and appropriate supplementation.

That said, there are some specific probiotic strains that have evidence of aiding with mood and stress.

In the Sisu study, a randomized, double-blind, placebo-controlled, and parallel clinical trial, L. paracasei Lpc-37 improved psychological and physiological markers of stress and anxiety in healthy adults.* This probiotic significantly reduced perceived stress and tended to improve many other biomarkers related to stress in the general population.* This specific strain is used in several probiotic formulas by NOW, including the popular Probiotic-10 line of products, BerryDophilus, and Probiotic Defense, although at lower dosages than what was used in the Sisu study.

Sleep quality strongly relates to mood. An exploratory study showed an improvement across time in different aspects of the profile of mood state (sad mood, anger, and fatigue) in healthy individuals which took probiotics for six weeks. Sleep quality also reportedly improved after probiotics intake. There was no similar improvement in the control group.

VR: Talk about gut health, probiotics, and skin health. Whatโ€™s the linkage? What product would you point to? What science would you point to?

Levin: Similar to the gut-brain axis, there is a gut-skin axis; a relationship in which the immune properties of the gut microbiota can also influence skin health. Specialized oral probiotics have been suggested as a potential clinical approach to prevent photoaging of the skin from sun exposure.

Part of the normal biological function of the microbiota is to suppress pathogens by competition, by synthesizing antimicrobial materials in the gut, and by producing the short-chain fatty acids to maintain gut barrier integrity. Another normal function of the microbiota is to upregulate the production of immune factors such as IgA, which can attach to antigens to reduce pro-inflammatory factors.

The enhancement of protective barriers in the gut also enhances the protective barrier of the skin against undesirable microbes. The mechanisms that suppress undesirable microbes in the gut also enhance the suppression of undesirable microbes in the skin. While 70 percent of immune cell activity is in the GI tract, these cells do migrate to other parts of the body to supply normal healthy immunity. Reducing their workload in the gut and enhancing their vitality allows these immune cells to better provide their benefits in other areas of the body, including the skin, maintaining the normal homeostatic state of the body. The common use of oral antibiotics to treat acne is one example of the gut-skin axis recognized by conventional medicine.

VR: What about prebiotics, postbiotics and synbiotics? Where do they fit in here?

Levin: Probiotics are defined as live microbes that safely convey a health benefit to the host. In order to determine both safety and efficacy, it is necessary to properly identify the genetics of each strain and submit it to toxicological and clinical studies. Probiotics are typically consumed either in raw foods/beverages (including ones that have first been heated and then inoculated without subsequent heating) or in the form of dietary supplements.

Prebiotics are nutrients, typically forms of dietary starches or fiber, which are food for probiotics. Prebiotics selectively stimulate growth and activity of probiotic bacteria in the colon to benefit the host. Some studies have indicated that the consumption of prebiotics is more effective at maintaining or raising levels of beneficial bacteria in the gut than taking the actual live organisms, which require a food source. Since Americans typically only get one-third of the recommended amount of fiber in our diets, that is one potential cause of a prebiotic deficit that inhibits the health of our microbiome.

Postbiotics are defined as beneficial substances produced by probiotics. They can modulate gut microbiota composition by selectively supporting or inhibiting the growth of various types of bacteria, in general favoring probiotic ones. Other postbiotic compounds can enhance the gut barrier function, serve as modulators of inflammatory and oxidative processes, and help modulate immune response; these are all normal functions of a healthy digestive system containing an appropriate microbiome.

VR: What about good bacteria and energy metabolism?

Levin: Gut probiotics can actually generate short-chain fatty acids (SCFAs) by fermenting resistant starches and fiber that are normally not digested in the small intestine to be available for general energy in our bodies. This creates a sparing effect where these fermentation products (SCFAs) in the large intestine can supply energy to the gut cells to maintain the integrity of their barrier function. This supports immunity and tolerance to foods, as well. All of these processes in the body are energetic, and the ability to directly supply food sources to these energy-hungry gut cells allows more of the bodyโ€™s energy to go to other needs including the heart, brain, metabolism, repairs, and immunity. L-glutamine is another potential energy source for these cells in the gut, but it is also an alternate energy source for the brain; this is an example of the potential sparing effect of supplying energy to gut cells via fermentation of prebiotics rather than needing to use other types of nutrients for that purpose.

VR: How can retailers break down these complicated concepts and connections for their customers?

Levin: I always suggest that retailers focus on the clinically relevant benefits of specific strains of probiotics. They should look for the Latin binomial, the genus and species such as Lactobacillus acidophilus, but also look for a third designation of the strain, which is often a combination of letters and numbers such as La-14. Once you have all three parts of a strainโ€™s name you can type or paste that into PubMed (the NIHโ€™s National Library of Medicine online database) within quotation marks to search for that strain and its body of evidence in the published scientific peer-reviewed literature (โ€œLactobacillus acidophilus La-14โ€).

I also point out that taking oral probiotic supplements is not a self-sufficient way to maintain a healthy microbiome because the addition of sufficient prebiotics, both resistant starches and fiber, is also required in the same way that you wouldnโ€™t plant a garden without fertilizing and watering the plants to sustain their growth.

I donโ€™t think thereโ€™s a big need to discuss synbiotics, the simple combination of prebiotics and probiotics, or postbiotics, substances produced by the probiotic strains to act as agents of their biological benefits in our bodies. While it is useful to discuss them as part of a comprehensive discussion, the simple message for consumers is that they need both probiotics and something to feed them, whether itโ€™s in the same formula or not, and thereโ€™s normally no need to go into the specific mechanics (postbiotics) of exactly how they result in benefits to the host (person).


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