Stroke is a leading cause of serious long-term disability and death for Americans. Stroke-related healthcare costs in the United States totaled nearly $56.5 billion between 2018 and 2019, encompassing expenses related to healthcare services, medications, and missed work days. (46)
Research suggests that the gut-brain axis plays a role in stroke recovery, prompting the exploration of gut-healing interventions like probiotics to modulate inflammation, enhance rehabilitation, and decrease the burden of stroke-related disability. Recognizing the intricate links between stroke and the gut opens avenues for holistic stroke management strategies that address both neurological and gastrointestinal aspects of health.
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Understanding the Gut-Brain Axis
The gut-brain axis (GBA) is a bidirectional communication network connecting the gastrointestinal (GI) tract and the central nervous system (CNS). Signals originating in the brain influence the function of the GI tract and vice versa. Research reveals that the gut and brain interact through various means, including the vagus nerve, neurotransmitters, and the gut microbiome.
The GI tract is innervated by an extensive neuronal network called the enteric nervous system (ENS), composed of 400-600 million neurons. The ENS is the largest unit of the peripheral nervous system; hence, why the gut has been termed the "second brain." The vagus nerve, or cranial nerve X, is the longest cranial nerve and a primary component of the nervous system's parasympathetic ("rest and digest") division. The brain and the ENS utilize the vagus nerve as a highway to transmit signals to each other. The vagus conveys sensory information from the gut to the brain, which sends motor signals back to the gut. Psychological stress reduces vagal tone, which has been described in patients with irritable bowel syndrome (IBS) and inflammatory bowel disease (IBD).
The commensal bacteria that reside in the gut, called the gut microbiota, also modulate the GBA by producing neurotransmitters and other metabolites, like short-chain fatty acids (SCFAs). Neurotransmitters are chemical messengers that assist in transmitting electrical signals through the nervous system to regulate physiological and mental processes. One of the functions of the gut microbiota is producing neurotransmitters, including dopamine, GABA, glutamate, and serotonin. In fact, more than 90% of serotonin, which influences mood and gut function, is produced in the gut. (16)
SCFAs, including acetate, butyrate, and propionate, are byproducts of bacterial fermentation of dietary fibers. SCFAs serve as an energy source for colonocytes (the cells lining the colon), modulate the release of neurotransmitters, and have anti-inflammatory properties. SCFAs can cross the blood-brain barrier, promote neuronal health, and mitigate neuroinflammation. (38, 41)
Stroke, marked by reduced blood flow to the brain, profoundly affects the GBA. Imbalances in the gut microbiota, the CNS, and ENS are linked to increased inflammation and oxidative stress, which are underlying factors implicated in stroke pathogenesis. Strokes can also affect gut health and function. The initial oxygen and nutrient deprivation during a stroke trigger shifts in the gut microbiome, perpetuating inflammation. Difficulty swallowing and other changes in gut motility, common complications of stroke, can further negatively impact gut health by affecting eating patterns and the gut microbiome composition. (33)
The Impact of a Stroke on Gut Health
Stroke effects on gut health extend beyond the immediate neurological consequences, encompassing direct and indirect repercussions on the GBA. One notable direct effect is the alteration of gut motility. The disruption of blood flow to the brain during a stroke can impair the regulatory signals transmitted through the vagus nerve, leading to changes in gastrointestinal function. This, in turn, can result in slowed gut motility, affecting the timely movement of food through the digestive tract. Dysphagia (difficulty swallowing) affects more than 50% of stroke survivors and is correlated to a higher risk of death during hospital admission. According to a recent 2022 stroke registry study, approximately half of dysphagia complications persist after hospital discharge, imposing a lasting burden on patients' health. Constipation emerges as the second most prominent symptom in patients with brain stem infarcts, with a 45% overall incidence. Constipation history not only correlates with worse stroke outcomes but the use of laxatives is also associated with increased stroke risk in patients with constipation. (50)
Stroke-induced dysmotility induces shifts in dietary patterns, given that dysphagia and other musculoskeletal deficits present challenges with preparing and eating food. In a 2003 study, 66% of stroke survivors had slight-to-moderate eating disabilities six months after their stroke. Additionally, neurological deficits resulting in diminished taste and smell can contribute to a loss of appetite. Collectively, these put stroke survivors at risk of eating and drinking less than they need. Low-fiber diets reduce microbial diversity and SCFA production, sustaining intestinal dysbiosis, cardiometabolic dysfunction, and chronic inflammation. Malnutrition increases the risk of bacterial infections and systemic inflammation, which charge neuroinflammation.
The concept of dysbiosis in stroke patients holds implications for the recovery process and future stroke risk. Dysbiosis can contribute to increased neurological and vascular inflammation, potentially exacerbating the systemic effects of a stroke. Scientists have identified multiple types of bacteria associated with an increased risk for ischemic stroke, severity of stroke, and poorer stroke-recovery outcomes, including Fusobacterium, Negativibacillus, Lentisphaeria, and Acidaminococcus. Interestingly, Acidaminococcus produces succinate, which has been linked to increased risk factors for cardiovascular disease. (36)
Research is uncovering the significance of the gut microbiome in neurological and vascular recovery, prompting exploration into interventions that aim to restore microbial balance. Studies exploring the use of fecal microbiota transplant (FMT), which is the transfer of donor fecal matter to a recipient to manipulate the recipient's gut microbial composition, have shown promise in its use to normalize post-stroke dysbiosis and improve post-stroke outcomes. (35, 43)
Functional Medicine Approach to Gut Health Post-Stroke
Functional medicine treatment post-stroke involves a personalized and comprehensive approach that recognizes the importance of GBA on neurological recovery. Functional medicine doctors conduct thorough health assessments to identify individual factors influencing gut health and stroke recovery. This includes a detailed analysis of medical history, lifestyle, and environmental factors in addition to specialty testing to assess neurological, cardiovascular, and gastrointestinal health. Particular attention should be given to understanding the patient's unique physiological makeup and any pre-existing conditions that may influence the GBA. This approach recognizes the uniqueness of each patient, acknowledging that one-size-fits-all solutions may not be effective in the complex interplay of gut health and stroke recovery.
Cardiometabolic Assessment
Atherosclerosis is the leading cause of ischemic strokes. High cholesterol, hypertension, elevated blood sugar, obesity, and a family history of premature cardiovascular events increase an individual's risk for atherosclerotic cardiovascular disease (ASCVD). Stroke prevention involves routine monitoring of cardiometabolic parameters associated with vascular disease, including:
- Blood pressure
- Comprehensive Metabolic Panel by Access Med Labs
- Hemoglobin A1c by Access Med Labs
- Lipid Panel Comprehensive by BostonHeart Diagnostics
- Fasting Insulin (In) by ZRT Laboratory
Oxidative Stress Markers
Oxidative stress plays a crucial role in the progression of ischemic stroke and the development of ischemic brain injury. Reactive oxygen species (ROS), generated during cerebral ischemia, contribute significantly to oxidative stress and are implicated in cell death, ultimately leading to brain damage upon reperfusion. Consequently, there is a growing focus on neuroprotective therapies targeting various stages of the cerebral ischemia cascade, including free radical scavengers and anti-inflammatory agents. (53)
The Oxidative Stress 2.0 panel by Genova Diagnostics is a urine test that measures 8-hydroxy-2’-deoxyguanosine (8-OHdG) and lipid peroxides. Elevated levels of either biomarker indicate increased levels of systemic oxidative stress and the need for interventions that reduce oxidative damage.
Comprehensive Microbiome Assessment
Analyzing the composition and diversity of the microbiome with a comprehensive stool analysis, such as GI-MAP by Diagnostic Solutions, allows for the identification of specific microbial signatures associated with stroke risk, enabling targeted interventional measures. This test also provides information regarding digestion function and intestinal inflammatory burden to support healthcare providers in recommending holistic treatment recommendations that support overall gut health and function in stroke survivors.
Nutritional Assessment
Malnutrition is an important predictor of poor prognosis for stroke recovery, correlated to increased stress reaction, higher frequency of infections, greater mortality, worse outcome, and longer hospitalization admittance. Conversely, proper nutrition is linked to improved motor function, cognition, ability to perform activities of daily living, and mood in stroke survivors. A comprehensive micronutrient test, such as NutrEval by Genova Diagnostics, assesses nutritional status by screening for protein, vitamin, mineral, fatty acid, and antioxidant insufficiencies. These results help guide healthcare professionals tailor nutritional and supplemental protocols to optimize health and recovery based on a patient's cellular nutritional needs.
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Nutritional Interventions for Gut Health
Nutritional interventions confer multifaceted benefits that contribute to neurological healing, cardiovascular health, and optimal gut function.
Nutrition is critical in supporting brain health and promoting neurological healing after a stroke. Omega-3 fatty acids and antioxidants have neuroprotective properties, whereas diets high in saturated fats and refined sugars are associated with decreased neuronal genesis and increased inflammation.
Nutrition is also a cornerstone for optimizing cardiovascular function, which is why it is a first-line treatment in managing cardiovascular disease. Extensive evidence supports the efficacy of the Mediterranean, DASH, MIND, and Nordic diets in reducing overall cardiovascular risk and mortality. These dietary patterns have been shown to positively alter blood pressure, lipid profiles, glucose control, and inflammation, collectively contributing to improved cardiovascular health outcomes.
Dietary properties associated with inflammation and gut dysbiosis typically include a high intake of processed foods, refined sugars, saturated fats, and low-fiber foods. These dietary patterns often lead to increased levels of inflammatory markers in the body and disturbances in the composition of the gut microbiota. Ultra-processed foods are associated with gut dysbiosis, cognitive impairment, and psychological illness. In contrast, a diet that promotes a healthy gut environment typically consists of whole, minimally processed foods rich in fiber, vitamins, and antioxidants. These include fruits, vegetables, whole grains, legumes, nuts, and seeds. Such a diet provides essential nutrients that support the growth of beneficial bacteria in the gut and help regulate inflammation. Additionally, fermented foods like yogurt, kefir, sauerkraut, and kimchi contain probiotics that contribute to a diverse and balanced gut microbiome. A meta-analysis of 26 randomized controlled trials comparing the efficacy of enteral nutrition with probiotics to enteral nutrition alone in stroke patients concluded that the addition of probiotics to nutritional therapy results in improvements in nutritional status, the gut microbiome, intestinal mucosal barrier function, immune function, and gastrointestinal motility.
The Role of Lifestyle in Supporting Gut Health
Stress profoundly influences gut health through the intricate interplay of the GBA. Chronic stress triggers changes in the gut that can contribute to increased intestinal permeability, a phenomenon often referred to as "leaky gut." This alteration allows substances like bacteria, toxins, and undigested food particles to cross the intestinal barrier into the bloodstream, sparking inflammatory immune responses. Concurrently, stress can disrupt the balance of the gut microbiome, leading to dysbiosis and potential gastrointestinal issues. The release of stress hormones, such as cortisol and catecholamines, can induce low-grade inflammation in the gut, impacting overall digestive function. Additionally, stress influences neurotransmitter levels and immune system responses in the gut, contributing to functional gastrointestinal disorders. Recognizing and managing stress through mindfulness and relaxation techniques alleviates stress and positively impacts the gut. Yoga and mindfulness have been deemed clinically valuable in stroke rehabilitation and correlated to improvements in cognition, mood, balance, and perceived stress levels in stroke survivors.
Exercise promotes the diversity and abundance of beneficial gut microbes, contributing to a healthier gut microbiome. Additionally, it reduces inflammation throughout the body, including the gut, and enhances the integrity of the gut barrier, preventing the leakage of harmful substances into the bloodstream. Physical activity stimulates the release of neurotransmitters such as serotonin and dopamine, which impact mood and gut function. As exercise is a potent stress-reliever, it positively influences the GBA by reducing stress levels. These collective effects on the GBA promote overall gut health and play a crucial role in positive clinical outcomes for stroke recovery. Exercise supports neurological healing, aids in vascular health, and contributes to improved motor and cognitive recovery post-stroke.
Insomnia affects up to 56% of stroke survivors; however, quality sleep is essential for supporting stroke recovery. During sleep, the body undergoes essential repair processes, consolidates memories, and regulates neurotransmitters involved in mood and stress response. Sleep is integral in maintaining a balanced gut microbiome, as disruptions in the sleep-wake cycle can impact the composition and diversity of gut microbes. Moreover, sufficient sleep is associated with reduced inflammation, supporting overall gut health and preventing disruptions in the gut barrier function. A good sleep regimen optimizes neural repair, cognitive function, and emotional well-being. Individuals experiencing adequate sleep demonstrate improved motor recovery and cognitive outcomes post-stroke, emphasizing the crucial role of sleep in fostering positive clinical outcomes and overall neurological recovery.
Monitoring and Adapting the Plan
Optimizing stroke recovery involves a dynamic and personalized approach to gut health, emphasizing ongoing monitoring and adaptation of the gut health plan. Regular health evaluations are crucial in assessing patients' progress and addressing challenges individuals face in their recovery journey. These evaluations provide valuable insights into the impact of the gut health plan on overall well-being, allowing for timely adjustments based on individual responses and emerging needs.
Adjustments to dietary and lifestyle plans are paramount for tailoring interventions to the evolving requirements of stroke survivors. As recovery progresses, dietary preferences, tolerances, and nutritional needs may change. Adapting the gut health plan ensures that it remains relevant and effective, supporting the individual's unique requirements and enhancing the overall recovery.
Engaging with a multidisciplinary team is integral to comprehensive stroke recovery. Collaboration among healthcare professionals, including neurologists, cardiologists, dietitians, physiotherapists, and mental health specialists, ensures individuals receive holistic and integrative care to manage and address all aspects of health pertinent to stroke recovery and prevention.
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Revitalizing Gut Health in Stroke Recovery: Key Takeaways
The functional medicine perspective on stroke recovery illuminates the pivotal role of gut health in enhancing clinical outcomes. As research continues to shed light on the gut-brain axis and its implications on neurological health, we realize that supporting the gut microbiome and intestinal barrier function through diet and lifestyle is integral to enhancing stroke recovery. Incorporating gut-healing modalities into post-stroke care opens new avenues for comprehensive recovery and underscores the interconnected nature of the body's systems, providing a pathway toward enhanced resilience and improved quality of life.
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