
Pathways to Well-Being
92 episodes — Page 1 of 2
Supporting Patients in the Era of GLP-1 Medications Monique Class, MS, APRN-BC

Understanding Histamine Intolerance with Amy Rolfsen, ND
On this episode of Pathways to Well-Being, we welcome Dr. Amy Rolfsen, naturopathic physician, educator, and medical consultant at Diagnostic Solutions Laboratory, to discuss assessment options and treatments that can help patients with histamine intolerance.

Nutrition, Menopause, and Women’s Health at Midlife and Beyond with Annina Burns, PhD, RDN, FMCP
On this episode of Pathways to Well-Being, new host and IFM Director of Medical Education Kelechi Uduhiri, MD, welcomes nutritionist, women’s health expert, and AIC 2026 speaker Annina Burns, PhD, to discuss how the functional medicine collaborative care team model can help empower women to understand their unique nutritional needs and improve their health in midlife and beyond.
In Conversation with the 2025 Linus and Ave Helen Pauling Award Winner Deanna Minich, MS, PhD, and Jeffery Bland, PhD
On this special episode of Pathways to Well-Being, IFM co-founder Dr. Jeffery Bland talks with the winner of the 2025 Linus and Ave Helen Pauling Award in Functional Medicine, Dr. Deanna Minich.

Exploring the Potential of Psychedelics in Mental Health with Robin Carhart-Harris, PhD
On this episode of Pathways to Well-Being, noted psychiatric researcher Robin Carhart-Harris, PhD, discusses the potential of psychedelic-assisted therapies to better understand how these agents may be applied therapeutically to support mental health and brain function.

Vagus Nerve Stimulation: Modulating the Parasympathetic Response
On this episode of Pathways to Well-Being, Peter Staats, MD, MBA, discusses the role of the vaganerve is modulating the body’s response to chronic and acute stressors, and explores vagus nervestimulation therapies for restoring parasympathetic balance.

Ketogenic Diets and Brain Health with Dr. Terry Wahls
On this episode of Pathways to Well-Being, legendary IFM educator Dr. Terry Wahls discusses how low-carbohydrate dietary plans like paleo and keto can provide the necessary nutrients to fuel the brain and help prevent cognitive decline and neurodegeneration, as well as how we can help patients implement and sustain these dietary changes to improve brain health.

Breath, Autonomic Balance, and Health with Sachin Patel, DC
On this episode of Pathways to Well-Being, we welcome AIC 2025 presenter Dr. Sachin Patel to discuss the importance of breathing, mindfulness, and achieving balance from within.

Whole Health and Transforming Healthcare Systems With Tracy Gaudet, MD
On this episode of Pathways to Well-Being, Whole Health pioneer and featured 2025 AIC speaker TracyGaudet, MD, who has years of experience as an agent of change in healthcare systems, will explore whathealthcare transformation means and how practices and hospital systems alike can begin to achieve it.

Healing the Physiological Effects of Trauma
On today’s episode of Pathways to Well-Being, AIC 2025 speaker Aimie K. Apigian, MD, MS, MPH, explores physiological dysfunction rooted in past trauma, differentiates between the body’s stress response and trauma response, and discusses how trauma affects mental, emotional, and physical markers of health.

Optimizing Protein Intake for Muscle Health and Improved Health Across the Lifespan
On today’s episode of Pathways to Well-Being, 2025 AIC speaker Donald Layman, PhD, FASN,explores why muscle health is so important to overall health, the lifestyle-based approaches thatbenefit muscle quality and preservation, and the important role that protein plays.

Chronic Infections as an Underlying Cause of Persistent Symptoms
On today’s episode of Pathways to Well-Being, Tom Sult, MD, discusses the important clinical connections between chronic infections and common persistent symptoms and how to manage them using functional medicine strategies. Transcript: https://www.ifm.org/podcast/chronic-infections-persistent-symptoms

Pediatric Food Allergies & Intolerances with Rebecca Carey, MD
Pediatric gastroenterologist Rebecca Carey, MD, shares how childhood GI issues and sensitivities influence adult health. Transcript: https://www.ifm.org/podcast/food-allergies-intolerances-pediatric-health

Revisiting the Trending Topics in Functional Medicine of 2024
As a systems-based approach, the functional medicine model looks all facets of health; evaluating why disease occurs and uncovering what each patients needs to thrive. Over the past year, we’ve discussed how this personalized approach to dysfunction and disease makes a difference in clinical outcomes. On this special episode of Pathways to Well-Being, we’re revisiting some of the trending topics and highlights of 2024. From brain health and thyroid health, to Long COVID, menopause, the gut microbiome and beyond, we’ll explore how the core concepts of functional medicine, such as precision nutrition, lifestyle modifications, and honoring the patient's story, can impact these diverse areas of care because they make health goals achievable and sustainable long-term. Transcript: https://www.ifm.org/podcast/2024-trending-topics-in-functional-medicine

Linking Stress and Inflammation to Chronic Disease
Mylene Huynh, MD, MPH, IFMCP, explores the connections between stress, inflammation, and disease and highlights ways to effectively transform stress to improve health. Transcript: https://www.ifm.org/news-insights/stress-inflammation-chronic-disease/

Optimizing Cancer Care & Prevention
Rebecca Knackstedt, MD, PhD, discusses the benefit of lifestyle-based modalities in supporting breast cancer treatment. Transcript: https://www.ifm.org/podcast/breast-cancer-care-and-prevention

The Impact of Toxins on the Gut Microbiome, With Dr. Joseph Pizzorno
On this episode of Pathways to Well-Being, Dr. Joseph Pizzorno discusses clinical indicators of toxic overload and how the integrity of the gut microbiome can influence an individual’s sensitivity to ubiquitous toxins. Transcript: https://www.ifm.org/news-insights/impact-of-toxins-on-the-gut-microbiome/

Improving Thyroid Function by Targeting the Gut Microbiome
On today’s episode of Pathways to Well-Being, clinical researcher and thyroid expert Michael Ruscio, DC, discusses the functional medicine approaches to optimizing and balancing thyroid hormone levels. Transcript: https://www.ifm.org/news-insights/improving-thyroid-function-gut-microbiome/

Biological Aging and Extending Healthspan, With Dr. Kara Fitzgerald
On this episode of Pathways to Well-Being, Dr. Kara Fitzgerald discusses epigenetics, longevity, and how diet and lifestyle-based interventions can slow biological aging to optimize the healthspan. Full transcript: https://www.ifm.org/news-insights/biological-aging-health-span

Neuroinflammation, Brain Function, & Mental Health
On this episode of Pathways to Well-Being, we welcome Jaquel Patterson, ND, to explore the systemic impacts of neuroinflammation on physiological and psychiatric conditions and outline functional medicine approaches to optimizing brain health. Full transcript: https://www.ifm.org/news-insights/neuroinflammation-brain-function-mental-health/

Whole-Person Care for Perimenopause Symptoms
Carrie Levine, CNM, IFMCP discusses whole-person care for perimenopause and personalized approaches for assessing and treating fluctuating hormonal patterns. Full transcript: https://www.ifm.org/news-insights/podcast-july-2024-whole-person-care-perimenopause/

Drug-Induced Nutrient Depletion and How Functional Medicine Pharmacists Can Help
In this episode of Pathways to Well-Being, we welcome functional medicine pharmacists Dr. Lara Zakaria and Dr. Melody Hartzler to discuss drug-induced nutrient depletions and the role of pharmacists on collaborative care teams. View full transcript here: https://www.ifm.org/news-insights/podcast-july-2024-nutrient-depletion-and-pharmacists/

Mental-Emotional-Spiritual Connections to Physiology
In this episode of Pathways to Well-Being, Kara Parker, MD, discusses social determinants of health and assessing mental-emotional-spiritual well-being. Read episode transcript here: https://www.ifm.org/news-insights/podcast-june-2024-mental-emotional-spiritual-connections/

Exploring the Gut-Skin Connection
In this episode of Pathways to Well-Being, Drs. Michael Chapman and Patti Devers from Genova Diagnostics discuss the connection between skin and gut health. Read episode transcript here: https://www.ifm.org/news-insights/podcast-may-2024-exploring-the-gut-skin-connection/

How the Changing Seasons Impact Nutrition, Health, & the Body’s Internal Clock
In this episode of Pathways to Well-Being, we welcome 2024 AIC speaker Dr. Deanna Minich to discuss the intricate relationship between the changing seasons, circadian rhythms, the foods we eat, and our health

The Phytobiome, Planetary Health, and Human Disease
In this episode of Pathways to Well-Being, we welcome 2024 AIC speaker Dr. Michael Ash to discuss what we know about the phytobiome and its potential implications for planetary and human health View episode transcript: https://www.ifm.org/news-insights/podcast-april-2024-phytobiome-planteray-health/

Micronutrient Deficiencies, Ultra-Processed Foods, & Personalized Food Plans
In this episode of Pathways to Well-Being, we welcome Dr. Liz Lipski to discuss the importance of micronutrients and how emphasizing these components in personalized therapeutic food plans may benefit a patient’s health. Read episode transcript here: https://www.ifm.org/news-insights/podcast-april-2024-micronutrient-deficiencies-processed-foods/

ADHD Management: The Benefits of Lifestyle-Based Interventions & Functional Lab Testing
In this episode of Pathways to Well-Being, Dr. Kate Kresge from Rupa Health discusses nutrition, exercise, and functional lab testing in the context of ADHD management. Click to view episodes transcript: https://www.ifm.org/news-insights/podcast-march-2024-adhd-management/

Long COVID & the Functional Medicine Approach to Care
In this episode of Pathways to Well-Being, functional medicine expert Dr. Elroy Vojdani discusses long COVID and how personalized care that addresses root causes may help.

The Oral-Systemic Connection & Personalized Nutrition Interventions
The oral and gut microbiomes have a complex relationship influenced by several factors, including the micronutrients, macronutrients, and phytochemicals that we consume. Research suggests that the intestinal microbiome can be influenced by diet, and that these dietary interventions, while they may not result in the same responsiveness in all patients, may improve the symptoms and outcomes of a broad spectrum of diseases such as obesity, diabetes mellitus, non-alcoholic fatty liver disease, colorectal cancer, cardiovascular disease, and more. Today on Pathways to Well-Being we are talking with Megan Barnett, functional medicine nutritionist, about the oral-systemic connection and the role of personalized nutrition on these microbiota. We will be discussing how the oral microbiome influences inflammatory pathways via the gut creating dysbiosis, and how personalized nutrition may help bring the body back into balance.

Intermittent Fasting and Heart Health
Intermittent fasting may be an appropriate therapeutic approach for some patients and has been associated with improved health across a range of areas.1-4 Research suggests that the potential benefits of fasting work through multiple pathways from reducing oxidative stress to triggering autophagy. What are potential benefits when intermittent fasting therapies are used in the prevention and treatment of cardiovascular disease? And how can the latest research help inform clinical interventions? In this episode of Pathways to Well-Being, intermittent fasting expert Dr. Jason Fung joins us to discuss the fasting-heart health connection and how personalized intermittent fasting treatments may help improve patient outcomes. Click to view episodes transcript: https://www.ifm.org/news-insights/intermittent-fasting-and-heart-health/.

Whole Health and Functional Medicine in 2023 and Beyond
Whole Health and the Whole Health approach received a lot of attention in 2023. The move toward a cultural transformation in care delivery to include both prevention and treatment with conventional and complementary approaches that embed each patient in a “circle of health” was noted by the National Academies of Sciences, Engineering, and Medicine as a potential model for higher-value care nationally. Prioritizing a person-centered, integrated approach to health care that focuses on health creation and well-being by incorporating patients’ goals into their health care changes the focus from “What’s the matter with you?” to “What matters to you?” If that sounds a lot like functional medicine, it should; these two models of care are aligned in many ways. Today, we welcome IFM CEO Amy R. Mack, along with IFM Directors of Medical Education Drs. Robert Luby and Dan Lukaczer, for a conversation through the lens of Whole Health, with a look back on the important themes that emerged in 2023 and a look ahead to what is to come for the Whole Health approach and functional medicine. View episodes full transcript: https://www.ifm.org/news-insights/whole-health-and-functional-medicine-2023-and-beyond/

Diabetes Subtypes and Individualized Approaches to Metabolic Health
Metabolic dysfunction is common in many communities and contributes to many of the most debilitating chronic diseases across the globe. The spectrum of metabolic function includes several points for intervention both before and after the diagnosis of conditions such as type 2 diabetes. The functional medicine approach to assessing and treating metabolic dysfunction involves a personalized approach to each patient, including understanding the root causes of each patient’s issues and developing individualized treatment plans to address those specific causes. Researchers recently proposed a system for subtyping type 2 diabetes cases that may aid clinicians with pattern recognition and lead to therapeutic plans that are more tailored to each diabetes patient. On this episode of Pathways to Well-Being, we welcome Dr. Yousef Elyaman to discuss the functional medicine approach to metabolic health and how subtyping of diabetes might help clinicians identify and treat patients with metabolic dysfunction. Click to view episodes transcript: https://www.ifm.org/news-insights/diabetes-subtypes-and-individualized-approaches-to-metabolic-health/.

Environmental Toxins & Cancer: Exposure, Risks, and the Path Forward
Toxins and environmental chemicals pervade our everyday lives, and the human body has adapted over the years to withstand the increasing volume and complexities of these exposures. However, chronic exposure to known carcinogenic substances present in the environment, our indoor spaces, and even in the products we use, may contribute to significant health risks. When should clinicians begin to suspect toxicity as a contributing factor to disease and cancer? In this episode of Pathways to Well-Being Dr. Robert Rountree, discusses the connections between toxicant exposure and cancer risk, highlighting the critical role of the body’s detoxification pathways and offering key preventive strategies. Click to view full transcript: https://www.ifm.org/news-insights/environmental-toxicants-cancer-exposure-risks-and-the-path-forward/

Fasting and the Gut Microbiome: Exploring the Connection and Health Benefits
A therapeutic fasting intervention may be an appropriate component for a personalized treatment strategy and may improve health across a range of areas, from mental and cognitive performance to cardiometabolic health to the effectiveness of cancer treatments. Research suggests that the potential benefits of fasting work through multiple pathways, such as reducing oxidative stress, enhancing mitochondrial health, and triggering autophagy. Now, more studies indicate that fasting also positively impacts the gut microbiome. What’s that connection? What are the gut health benefits? And how can the latest research help inform clinical treatments? In this episode of Pathways to Well-Being, IFM educator and functional medicine expert Dr. Patrick Hanaway joins us to discuss the fasting-gut connection and to explore how a beneficial gut microbiome response to fasting may translate to improved patient outcomes. Click to view full transcript: https://www.ifm.org/news-insights/fasting-and-the-gut-microbiome-exploring-the-connection-and-health-benefits/

Exploring Mood Disorders and Brain Health Through the Lens of Functional Psychiatry
Mood disorders such as depression and anxiety are multi-factorial in nature, resulting from physiological and biochemical imbalances, and psycho-social imbalances. The field of functional psychiatry aims to identify the somatic root causes that contribute to mental health disorders. Due to the complexity and sensitivity around how these conditions manifest in each patient, the optimal treatment plan goes beyond a singular treatment modality and focuses on truly bringing the body, mind, and spirit back into balance. In this episode of Pathways to Well-Being, noted functional medicine psychiatrist Dr. Achina Stein joins us to explore how various body systems affect mental health and walks us throughs her approach to the diagnostic workup. Click here to view episode transcript: https://www.ifm.org/news-insights/exploring-mood-disorders-and-brain-health-through-the-lens-of-functional-psychiatry/

Akkermansia & Gut Health With Dr. Colleen Cutliffe
In this podcast, Dr. Colleen Cutliffe, a PhD scientist and the co-founder and CEO of the microbiome company, Pendulum Therapeutics, discusses the role that different bacterium such as Akkermansia play in optimal gut health and function. Click here to view episode transcript: https://www.ifm.org/news-insights/akkermansia-gut-health-with-dr-colleen-cutcliffe/

Food and Mood: Nutritional Psychiatry, the Microbiome, and Mental Health
Mental health disorders including depression and anxiety are a major cause of disability and reduction in quality of life worldwide. Many people who experience these conditions do not achieve lasting remission from pharmaceuticals or talk therapy alone. In the past ten years, the practice of nutritional psychiatry has developed to help fill this void. Focused on integrating dietary change into a broader treatment plan that may include medication, talk therapy, and other lifestyle approaches, nutritional psychiatry has helped many patients. On this episode of Pathways to Well-Being, Dr. Uma Naidoo joins us to discuss the connections between food and mood and how dietary change can impact the gut microbiome and improve mental health outcomes. Click here to view episode transcript: https://www.ifm.org/news-insights/food-and-mood-nutritional-psychiatry-the-microbiome-and-mental-health/

Navigating Menopause: Hormones, Mental-Emotional Function, and Sexual Health
The transition to menopause is a significant hormonal shift that marks each woman’s life and every journey is different depending on the person’s unique hormonal profile, health history, and wellness path. Along with the common vasomotor symptoms, women may also experience changes in arousal or desire and in mental-emotional function. Through nutrition and lifestyle change, women can stay empowered during menopause and maintain sexual health and optimal mental-emotional function. In this episode of Pathways to Well-Being, leading sexual health and menopause expert Dr. Anna Cabeca will discuss her functional medicine approach to optimizing functional hormones, mental-emotional function, and sexual health during the stages of menopause. Click here to view episode transcript: https://www.ifm.org/news-insights/navigating-menopause-functional-hormones-libido-and-sexual-health/

Nutrition’s Role in Anxiety Disorders: Evaluating Mental Wellness With Dr. Kate Henry
What role does nutrition play in anxiety disorders? Kate Henry, ND Head of Medical Education at RUPA Health, speaks with IFM podcast host Kalea Wattles, ND on this pertinent topic. Anxiety disorders in the US are common, affecting approximately 40 million adults every year. Concerns about mental health remain elevated three years after the onset of the COVID-19 pandemic, with 90% of US adults believing that the country is facing a mental health crisis. Both anxiety and panic disorders may severely impair a patient’s ability to function in life. While in some patients, mental wellness may be challenging to cultivate and maintain, clinical strategies that include nutrition interventions may have significant impacts. Dr. Wattles speaks with Dr. Henry about the nutritional imbalances that may contribute to the root cause of many mental health problems, as well as the role functional testing, including testing for nutrient deficiencies, which can help the clinician direct an appropriate treatment plan. Click here to view episode transcript: https://www.ifm.org/news-insights/nutritions-role-in-anxiety-disorders-evaluating-mental-wellness/

Phytocannabinoids for Treating Common Conditions
Description: Understanding medical cannabis, how it interacts with the human brain and body and the current clinical applications is necessary for all healthcare professionals now that it is available in most states and many countries. Bonni Goldstein, MD, will discuss her clinical experience using phytocannabanoids to treat common conditions as well as her research into using them as a treatment in pediatric populations. Click here to view episode transcript: https://www.ifm.org/news-insights/phytocannabinoids-for-treating-common-conditions/

Increasing Healthspan: From Micronutrients to Hormetic Stressors, With Dr. Rhonda Patrick
In this podcast, Rhonda Patrick, PhD, discusses healthy aging and longevity using personalized lifestyle-based approaches and emphasizes the importance of micronutrients, healthy fat intake, physical activity, and hormetic stress for disease prevention. Click here to view episode transcript: https://www.ifm.org/news-insights/increasing-healthspan-from-micronutrients-to-hormetic-stressors-with-dr-rhonda-patrick/

The Oral Microbiome & Systemic Disease
After the gut, the second largest and most diverse microbiome in the body is located in the mouth. The oral microbiome is becoming an increasing area of interest in the medical community as research highlights several connections between chronic oral dysbiosis and systemic diseases, with inflammation being a common link. Pathogenic oral bacteria may influence inflammatory pathways particularly via the gut and by translocation through perivascular spaces. Thus, maintaining balance is the oral microbiome is a critical strategy for reducing inflammatory burden and reducing the risk of certain diseases. On this episode of Pathways to Well-Being, we welcome 2023 Annual International Conference speaker Doug Thompson, DDS, FAAMM, ABAAHP, to discuss new prevention and treatment opportunities that bridge the gap between dental care and health care. Click here to view episode transcript:https://www.ifm.org/news-insights/the-oral-microbiome-systemic-disease/

Fueling for Fitness: Igniting Metabolism Through Personalized Lifestyle Interventions
Jade Teta, ND discusses modifiable lifestyle factors integral to metabolic health, explores the intricate connections between hormones and an individual’s metabolism, and shares clinical pearls for collaborative, effective and sustainable personalized interventions. Click here to view episode transcript: https://www.ifm.org/news-insights/fueling-for-fitness-igniting-metabolism-through-personalized-lifestyle-interventions/

Healthy Aging and Longevity with Mark Hyman, MD
Dr. Mark Hyman discusses the hallmarks of aging and how to optimize health and longevity through modifiable lifestyle factors and hermetic therapies. Click here to view episode transcript: https://www.ifm.org/news-insights/healthy-aging-and-longevity-staying-young-forever-with-mark-hyman-md/

Root Causes & Treatment of Mast Cell Disease
Mast cell activation disorders may present as episodic inflammatory symptoms that come and go over time making them difficult to diagnose. These fluctuating symptom patterns include allergic-type responses and non-specific symptoms ranging across the cardiovascular, endocrine, gastrointestinal, dermatologic, and respiratory systems. Chronic diseases and lifestyle choices may influence mast cell dysregulation and overall immune system activation. Identifying potential antecedents and triggers of mast cell activation is an important clinical step for determining the impact of this activation on a patient’s medical condition and for developing a treatment plan that supports both structural integrity and a healthy immune response. On this episode of Pathways to Well-Being, we welcome a pioneer in mast cell disease research, Dr. Lawrence B. Afrin to discuss recent advances in the literature and provide new insights on treating this complex disorder. Click here to view episode transcript: https://www.ifm.org/news-insights/root-causes-treatment-of-mast-cell-disease/

The 2022 Functional Medicine Year in Review
Functional medicine continues to equip healthcare providers with the latest tools, technology, and research to innovate patient care and enhance clinical outcomes. Throughout 2022, we’ve had our finger on the pulse of several prominent topics in the research literature such as mast cell activation syndromes, new research on dementia prevention, diabetes remission, and a perennial favorite, the gut microbiome. A systems-based approach to health and disease is being increasingly acknowledged, with modifiable lifestyle factors taking a central role in cultivating the health outcomes we seek for our patients. On this episode of Pathways to Well-Being, we’re recapping the functional medicine year in review with IFM’s Director of Medical Education Dan Lukaczer, ND, IFMCP, and the Director of Medical Education Initiatives Robert Luby, MD, IFMCP. They will discuss the clinical advances and clinical pearls gleaned from this calendar year, explore the state of research for trending topics in medicine, and shine light on new ways to enhance health, healing, and hope going forward. Click here to view episode transcript: https://www.ifm.org/news-insights/the-2022-functional-medicine-year-in-review/

Addressing the Root Causes of Cognitive Decline and Dementia
As life expectancy increases around the world, so too are the rates of dementia and cognitive decline. These conditions may be a major concern for some patients, especially those with a family history or increased genetic risk for neurodegenerative disease. Multi-pronged lifestyle interventions including nutrition and exercise offer hope for the prevention and delay of cognitive decline by reducing neuroinflammation and improving brain plasticity. On this episode of Pathways to Well-Being, we welcome Dr. David Haase to discuss the precursors to cognitive decline, how to address neurodegeneration, and support patient’s brain health long-term. Click here to view episode transcript: https://www.ifm.org/news-insights/addressing-the-root-causes-of-cognitive-decline-and-dementia/

Functional Medicine Approaches to Cancer Care
Conventional mainstays of cancer treatment may include surgery, radiation, chemotherapy, hormone therapy, and targeted therapy, but these approaches may not be as effective as standalone treatments. Supporting cancer patients with complementary lifestyle-based interventions such as nutrition, exercise, and mind-body therapies, may help reduce the side effects of cancer treatment and improve outcomes. On this episode of Pathways to Well-Being, Dr. Aisha Chilcoat is joining us to discuss functional medicine approaches to oncology and how to support cancer patients during and after their treatment. Click here to view episode transcript: https://www.ifm.org/news-insights/functional-medicine-approaches-to-cancer-care/

Psychobiotics: Therapeutic Potential for Modulating the Gut-Brain Axis
Communication between the gut and the brain is bidirectional and researchers continue to study whether brain and behavioral alterations seen in some mental health and neurological conditions are the result of intestinal dysbiosis or vice versa. This research had opened up therapeutic possibilities for targeting the microbiome to support overall mental and physical health. On this episode of Pathways to Well-Being, Dr. Holly Lucille joins us to discuss the concept of psychobiotics—beneficial probiotic bacteria in the gut that may improve health along the gut-brain axis as well as mental health outcomes. Click here to view episode transcript: https://www.ifm.org/news-insights/psychobiotics-therapeutic-potential-for-modulating-the-gut-brain-axis/