What has your gut microbiome ever done for you?


Our body acts as a host to vast array of micro-organisms. Often, we are only aware of these micro-organisms causing unwanted infection: for example when a cut on the skin becomes infected, or we suffer with a bout of infective gastro-intestinal upset. Actually, this perception of the micro-organisms, living both on and inside, only causing unwanted infections is very biased. The microbiome (all the micro-organisms, their genetic material and metabolites produced) plays a vital role in keeping us healthy.

Recent research demonstrates that elite level cyclists host distinct clusters of microbiome communities when compared to controls which contribute to more effective metabolic pathways.

The gut microbiota consist of the range of micro-organisms living in our gut, mainly the colon. Recent research reveals that the diversity and functions of the gut microbiota have far reaching impact on health. For example, there is an important interaction between these micro-organisms and mitochondria, which are the organelles in cells responsible for producing energy. This cross talk is of particular consideration for athletes who seek to optimise energy production for training and competition. The gut microbiota also interact with the immune system and central nervous system function, including behaviour. There is evidence that the gut microbiota even influences brain development.

Microbiome Mitochondria Feedback

On the other side of the coin, any disruption in the beneficial types of gut microbiota have been linked to chronic disease states including obesity, metabolic syndrome and mental health issues. What causes imbalances in gut microbiota to produce such problems? A possible aetiology is a poorly balanced diet, or the side effect of medication which does not support the growth and function of beneficial bacteria. Rather an overgrowth of potentially harmful bacteria is favoured: dysbiosis. In athletes there is a condition know as “leaky gut” which can result from endurance training. In this scenario, blood is diverted away from the gut during exercise to the exercising muscles. After stopping exercise, blood flow is restored to the gut resulting in a mild reperfusion injury. This results in a slightly “leaky gut” so that unwanted bacteria in the gut are able to pass into the body and provoke an inflammatory response. Equally this situation can also mean desirable nutrients in the gut as less well absorbed. Although a degree of inflammatory response supports desirable adaptations to exercise, clearly an over-response will be counter productive to improving sports performance.

The gut microbiota have been reported to regulate immune function. Athletes in heavy training can experience suppressed functional immunity so any strategies to support the gut microbiota will potentially be beneficial in preventing infection.

What can you do to support a beneficial gut microbiota to support health and sport performance?

  • Try to include at least one fermented food source in your diet every day to boost your probiotic bacteria. Try sourdough bread, yogurt, kefir (similar to yogurt), sauerkraut, kimchi (Korean fermented vegetables), tempeh and miso (fermented soya products) and kombucha (fermented teas). These products can be found in health food shops and are becoming more widely available in some supermarkets and lunch places.
  • Regularly eat pre-biotic foods like garlic, onion, leeks, chickpeas, beans and lentils. These provide fuel for your probiotic bacteria, enabling them to proliferate.
  • Have adequate fibre in your diet from a wide variety of plant foods: eg wholegrains, legumes, vegetables, fruits, nuts, seeds. Dietary fibre is fermented by your probiotic bacteria to produce short chain fatty acids (SCFAs) which play a key role in keeping your gut healthy.
  • Consume foods and drinks rich in polyphenols: eg berries, green tea, coffee, black tea, red wine, dark chocolate, apples. Polyphenols, found in many plant foods, have been shown to help increase probiotic bacteria in the gut.
  • Take a good quality, multi-species probiotic supplement during winter, heavy training blocks and when travelling abroad, especially for races. To find out more about the potential benefits of probiotic supplementation for athletes, see this blog by nutritional therapist Jo Scott-Dalgleish: http://www.endurancesportsnutritionist.co.uk/blog/probiotics-guide-endurance-athlete/

To find out more about the interaction between Health, Hormones and Human Performance come to the British Association of Sport and Exercise Medicine annual conference


Community characteristics of the gut microbiomes of competitive cyclists Microbiome August 2017

Ubiquitous Microbiome: impact on health, sport performance and disease

Endocrine system: balance and interplay in response to exercise training

Inflammation: Why and How Much? Dr N. Keay, British Association of Sport and Exercise Medicine 2017

Ubiquitous Microbiome: impact on health, sport performance and disease

Microbiome Mitochondria Feedback

The gut microbiome plays a key role in regulating the optimal degree of response to exercise required to stimulate desired adaptive changes.

We have at least as many bacterial cells as human cells in our bodies. We are all familiar with the effects of disturbing the balance of beneficial microbes in our gut. Beyond this, the gut microbiome (the range of microbes, their genetic material and metabolites) is essential for health. An interactive feedback exists between gut microbiota and functional immunity, inflammation, metabolism and neurological function

Sports performance: endurance exercise increases metabolic, oxidative and inflammatory stress, signalled by the release of exerkines from exercising tissue. This signalling network induces adaptive responses mediated via the Endocrine system. Maladaptation to exercise can be due either to an undesirable over-response or an insufficient response.

Intricate interactive feedback links exist between mitochondria and the gut microbiota. In addition to being the power generators of all metabolically active cells, mitochondria produce reactive oxygen species (ROS) and reactive nitrogen species during high intensity exercise. These oxidative stress signals not only mediate adaptive responses to exercise during recovery, but influence gut microbiota by regulating intestinal barrier function and mucosal immune response. Mitochondrial genetic variation could influence mitochondrial function and thus gut microbiota composition and function. Equally, the gut microbiota and its metabolites, such as short chain fatty acids, impact mitochondrial biogenesis, energy production and regulate immune and inflammatory responses in the gut to mitochondrial derived oxidative species. So nutritional strategies to support favourable gut microbiota would potentially support the beneficial effects of the interactions described above to optimise sport performance in athletes.

Conversely, disruption to favourable diversity of the gut microbiota, dysbiosis, is associated with increase in both inflammation and oxidative stress. Not a good situation for either health or sport performance. Alteration to the integrity of the intestinal wall increasing permeability can also be a factor in disrupting the composition of the gut microbiota. The resultant increased antigen load due to bacterial translocation across the gut wall is linked to increased inflammation, oxidative stress and metabolic dysfunction. “Leaky gut” can occur in high level endurance exercise where splanchnic blood flow is diverted away from the gut to exercising tissues for long periods of time, resulting in relative hypo-perfusion and an effective re-perfusion injury on stopping exercise. In the longer term the increased levels of inflammation, oxidative stress and antigen load impair adaptation to exercise and are associated with endocrine dysfunction in chronic disease states, for example autoimmune conditions, metabolic syndrome (type 2 diabetes mellitus, obesity) and depression.

Evidence links the composition of the gut microbiota to changes in circulating metabolites and obesity. For example, low abundance of certain species of gut microbiota reduces levels of circulating amino acid glutamine, which acts as a neurotransmitter precursor. Bariatric surgery is associated with changes in the release of gut hormones regulating food intake behaviour and energy homeostasis. In addition, beneficial changes are seen in the gut microbiota which could directly or indirectly support weight loss, via action on gut hormones.

Metformin is frequency used to improve insulin sensitivity in both type 2 diabetes mellitus and polycystic ovary syndrome. However, the mechanism is poorly understood. There is now evidence that the effect of metformin is mediated via changes in gut microbiota diversity. Transfer of stool from those treated with metformin improves insulin sensitivity in mice. In addition metformin regulates genes in some gut microbiota species that encode metalloproteins or metal transporters, which are know to be effective ligands. The pathophysiology of metabolic syndrome and obesity involves an inflammatory component which is triggered by gut dysbiosis and bacterial translocation, with increased generation of oxidative species. Probiotics have a potential role in regulating the redox status of the host via their metal ion chelating ability and metabolite production, which has an impact on the production of ROS and associated signalling pathways. Prebiotics found in dietary polyphenols promote these actions of favourable gut microbiota, which is of benefit in metabolic syndrome.

Recently it has been postulated that the gut microbiome, apart from playing a crucial role in health and pathogenesis of disease states, also impacts brain development, maturation, function and cognitive processes.

Understanding the role of the gut microbiome on metabolism, inflammation and redox status is very relevant to athletes where an optimal response to exercise training supports adaptations to improve performance, whereas an over or under response in these pathways results in maladaptive responses.

For further discussion on Health, Hormones and Human Performance, come to the BASEM annual conference


Endocrine system: balance and interplay in response to exercise training Dr N. Keay

Inflammation: Why and How Much? Dr N.Keay, British Association of Sport and Exercise Medicine 2017

The Crosstalk between the Gut Microbiota and Mitochondria during Exercise Front Physiol. 2017

Gut Microbiota, Bacterial Translocation, and Interactions with Diet: Pathophysiological Links between Major Depressive Disorder and Non-Communicable Medical Comorbidities Psychother Psychosom 2017

Gut microbiome and serum metabolome alterations in obesity and after weight-loss intervention Nature Medicine 2017

Metformin alters the gut microbiome of individuals with treatment-naive type 2 diabetes, contributing to the therapeutic effects of the drug Nature Medicine 2017

L’altération de la perméabilité intestinale : chaînon manquant entre dysbiose et inflammation au cours de l’obésité ? Med Sci (Paris)

Antioxidant Properties of Probiotic Bacteria  Nutrients 2017

The Impact of Gut Microbiota on Gender-Specific Differences in Immunity Front. Immunol 2017

Commentary: Dietary Polyphenols Promote Growth of the Gut Bacterium Akkermansia muciniphila and Attenuate High-Fat Diet-Induced Metabolic Syndrome Front. Immunol., 27 July 2017

Gut microbial communities modulating brain development and function Gut Microbes



One road to Rome: Metabolic Syndrome, Athletes, Exercise

One road to Rome

Metabolic syndrome comprises a cluster of symptoms including: hypertension, dyslipidaemia, fatty liver disease and type 2 diabetes mellitus (T2DM).

The underlying pathological process is insulin resistance which distorts metabolism. Temporal and mechanistic connections have been described between hyperinsulinaemia, obesity and insulin resistance. Insulin levels rise, potentially stimulated by excess intake of refined carbohydrates and in addition the metabolic actions of insulin are attenuated on target tissues such as the liver, skeletal muscle and adipose tissue. At a cellular level, inflammatory changes play a part in this metabolic dis-regulation. Mitochondrial action in skeletal muscle is impaired, compromising the ability to oxidise fat as a substrate, thus resulting in muscle glycolysis and a consequent rise in blood lactate.

Although much attention has been focused on restricting calories and treating elevated lipids with medication (statins), evidence is now emerging that this does not have the anticipated effect of reducing mortality from cardiovascular disease. In addition, it has been proposed that the gut microbiota plays a pivotal role in metabolism, inflammation and immunity.

Metabolic syndrome usually conjures an image of an overweight person with or on the verge of developing T2DM. However there is an interesting group of slim people who are also are at risk of developing metabolic syndrome due to insulin resistance. The majority of women with polycystic ovary syndrome (PCOS) present with menstrual disturbance of some description. However not all display the textbook characteristics of Stein-Leventhal syndrome (overweight, hirsute and with skin problems). There is in fact of spectrum of clinical phenotypes ranging from the overweight to the slim. In all phenotypes of PCOS, the crucial uniting underlying metabolic disturbance is insulin resistance. The degree of insulin resistance has been shown to be related to adverse body composition with increased ratio of whole body fat to lean mass.

Although this confuses the picture somewhat, it also simplifies the approach. In all cases the single most important lifestyle modification is exercise.

Exercise improves metabolic flexibility: the ability to adapt substrate oxidation to substrate availability. Endurance exercise training amongst athletes results in improved fat oxidation and right shift of the lactate tolerance curve. Conversely metabolic inflexibility associated with inactivity is implicated in the development of insulin resistance and metabolic syndrome.

What about nutritional strategies that might improve metabolic flexibility? Ketogenic diets can either be endogenous (carbohydrate restricted intake) or exogenous (ingestion of ketone esters and carbohydrate). Low carbohydrate/high fat diets (terms often used interchangeably with all types of ketogenic diets) have been shown to improve fat oxidation and potentially mitigate cognitive decline in older people.

However, in the case of athletes, the benefits do not necessarily translate to better performance. Despite reports of such diets enhancing fat oxidation and favourable changes in body composition, a recent study demonstrates that this, in isolation, does not translate into improved sport performance. A possible explanation is the oxygen demand of increased oxidation of fat needs to be supported by a higher oxygen supply. The intermediate group of endurance athletes in this study, on the periodised carbohydrate intake, fared better in performance terms. Another recent study confirmed that a ketogenic diet failed to improve the performance of endurance athletes, in spite of improving fat metabolism and body composition. Despite small numbers, this warrants particular mention as the majority of participants were women, who are in general very underrepresented in scientific studies.

In all likelihood, the reason that these type of diets (ketogenic, high fat/low carb: not always well defined!) did not improve sport performance is that only one aspect of metabolism was impacted and quantified. Although fat oxidation, modified via dietary interventions, is certainly an important component of metabolism, the impact on the interactive network effects of the Endocrine system should be evaluated in the broader context of circadian rhythm. For athletes this goes further, to include integrated periodisation of nutrition, training and recovery to optimise performance, throughout the year.

In addition to dietary interventions, medical researchers continue to explore the use of exercise mimetics and metabolic modulators, to address metabolic syndrome. Unfortunately, some have sought their use as a short cut to improved sport performance. Many of these substances appear on the WADA banned list for athletes. However the bottom line is that it is impossible to mimic, either through a dietary or pharmacological intervention, the multi-system, integrated interplay between exercise, metabolism and the Endocrine system.

Only one road to Rome!

Whatever your current level of activity, whether reluctant exerciser or athlete, the path is the same to improve health and performance. This route is exercise, supported with periodised nutrition and recovery. Exercise will automatically set in motion the interactive responses and adaptations of your metabolic and Endocrine systems.

For further discussion on Endocrine and Metabolic aspects of SEM come to the BASEM annual conference 22/3/18: Health, Hormones and Human Performance


Insulin action and resistance in obesity and type 2 diabetes Nature Medicine 2017

Inflammation: Why and How Much? Dr N. Keay, British Association of Sport and Exercise Medicine

The cholesterol and calorie hypotheses are both dead — it is time to focus on the real culprit: insulin resistance Clinical Pharmacist 2017

Skeletal muscle mitochondria as a target to prevent or treat type 2 diabetes mellitus Nature Reviews Endocrinology 2016

The essential role of exercise in the management of type 2 diabetes Cleveland Clinic Journal of Medicine 2017

β cell function and insulin resistance in lean cases with polycystic ovary syndrome Gynecol Endocrinol. 2017

The many faces of polycystic ovary syndrome in Endocrinology. Conference Royal Society of Medicine 2017

Association of fat to lean mass ratio with metabolic dysfunction in women with polycystic ovary syndrome Hum Reprod 2014

Sedentary behaviour is a key determinant of metabolic inflexibility Journal of physiology 2017

International society of sports nutrition position stand: diets and body composition J Int Soc Sports Nutr. 2017

A cross-sectional comparison of brain glucose and ketone metabolism in cognitively healthy older adults, mild cognitive impairment and early Alzheimer’s disease Exp Gerontol. 2017

Low carbohydrate, high fat diet impairs exercise economy and negates the performance benefit from intensified training in elite race walkers J Physiol. 2017

Ketogenic diet benefits body composition and well-being but not performance in a pilot case study of New Zealand endurance athletes J Int Soc Sports Nutr. 2017

Sports Endocrinology – what does it have to do with performance? Dr N. Keay, British Journal of Sports Medicine 2017

Hormones and Sports Performance

Endocrine system: balance and interplay in response to exercise training


Endocrine system: balance and interplay in response to exercise training

The process of homeostasis maintains a steady internal milieu. So how is it possible for adaptations to occur? What are the internal mechanisms that determine a good outcome versus a negative one?

Changes in the external environment, such as exercise training, challenge homeostasis, producing spatial and temporal responses in the internal environment. These cause interactions between muscle, bone and gut, modulated by the Endocrine system. The degree and nature of these responses dictate whether a positive adaptation occurs. An excessive response, or a response not in tune with the networks of the Endocrine system, can hinder adaptation or produce a maladaptive response. The balance and interplay of internal responses are crucial in determining the outcome to exercise training in the individual.


Local responses in exercising tissues

Exercising tissues release exerkines (metabolites, nucleic acids, peptides) which are packaged in exosomes and microvesicles. The content of these vesicle packages increases with intensity of endurance exercise in a dose-dependent manner. These exerkines have autocrine and paracrine effects, which modulate systemic adaptations to endurance exercise in the tissues themselves and those in the vicinity.

The range of these molecular responses from exercising tissues has been identified applying multi-omics (epigenomic, transcriptomic and proteomic analyses). Furthermore variance in trainability has been shown to be correlated with the integrated responses of tissue molecular signalling pathways to endurance exercise.

In a similar manner, the degree of inflammatory response and production of reactive oxygen and nitrogen species (RONS) to exercise mediate favourable adaptations. Inter-individual variations in redox status has been shown to determine the ability to adapt to exercise training. However, unlimited increase in response does not necessarily produce a better outcome. An over response to exercise in these signalling pathways, hinders adaptation.

Exercise promotes bone adaptation in terms of bone material, structure and muscle action. Paracrine crosstalk occurs between muscle and bone. Muscle myokines and insulin like growth factor 1 (IGF1) favour bone formation, whilst inflammatory molecules, such as interleukin 6 (Il-6) released during muscle contractions, favour bone reabsorption. The balance between these opposing processes determines whether bone remodelling is effective, or whether bone stress reactions occur over a pathological continuum. These responses and adaptations occur on the background of lifespan Endocrine environment, which impacts the outcome.

Gut microbiota

The gut microbiota support the regulation of inflammation at the local and systemic level. Furthermore the communication between the gut microbiota and mitochondria has been described as an important interaction in facilitating adaptive responses to exercise. Mitochondria are organelles crucial for production of ATP, as well as RONS. The gut microbiota are involved in mitochondrial biogenesis by regulating key mitochondrial transcriptional factors and enzymes . Furthermore, the metabolites of the gut microbiota such as short chain fatty acids, modulate the inflammatory effects of mitochondrial oxidative stress. Conversely genetic variants in the mitochondrial genome could impact mitochondrial function and thus the gut microbiota in terms of composition and activity.

The gut microbiota have a role in regulating intestinal permeability. Leaky gut is where epithelial integrity is lost at the tight junctions between cells in the gut lining. Leaky gut can occur in gut dysbiosis and also following endurance exercise where re-perfusion injury produces acute hyper-permeability. In these instances, increased gut permeability augments the antigen load and causes increased systemic inflammation and potentially can trigger autoimmune disease. This demonstrates that an excessive inflammatory response to exercise can hinder positive adaptation

Metabolic adaptations

Metabolic flexibility, the ability to respond and adapt to changes in metabolic demand, is enhanced with exercise training through these autocrine, paracrine and Endocrine mechanisms. Metabolic flexibility supports energy availability and fuel selection during exercise. Exercise mimetics, such as artificial metabolic modulators, have been reported to up-regulate gene expression to shift metabolism to fat oxidation in exercising muscle. This would potentially extend the limit of endurance exercise. However this “short cut” to adaptation favouring improved sport performance is illegal, with such molecular ligands on the World Anti-Doping Agency (WADA) banned list.

Hierarchy of control

There is a hierarchy of control in modulating multi-system adaptations to exercise. The Endocrine system is key. Exercise per se produces an Endocrine response, for example exercise is a key stimulus for growth hormone release via the hypothalamus, the neuroendocrine gatekeeper. Growth hormone supports the anabolic response to exercise. In addition, the Endocrine milieu during the lifespan has an impact on response and adaptations to exercise. Any disruption in the Endocrine system hinders adaptive changes. Endocrine dysfunction may occur as a result of non-integrated periodisation of exercise/nutrition and recovery as seen in relative energy deficiency in sports (RED-S). Dysfunction can also occur due to an Endocrine pathology.


Changes in external stimuli, such as exercise and nutrition, produce internal responses on autocrine, paracrine and Endocrine levels. These molecular signalling pathways drive adaptive changes through integrated, network effects. However any imbalances in these interactive responses can hinder desired adaptive changes and even result in negative maladaptive outcomes to exercise training.

For further discussion on Endocrine and Metabolic aspects of SEM come to the BASEM annual conference 22/3/18: Health, Hormones and Human Performance


Keay N, Logobardi S, Ehrnborg C, Cittadini A, Rosen T, Healy ML, Dall R, Bassett E, Pentecost C, Powrie J, Boroujerdi M, Jorgensen JOL, Sacca L. Growth hormone (GH) effects on bone and collagen turnover in healthy adults and its potential as a marker of GH abuse in sport: a double blind, placebo controlled study. Journal of Endocrinology and Metabolism. 85 (4) 1505-1512. 2000.

Sport Endocrinology presentation London 7/7/2017

Sports Endocrinology – what does it have to do with performance? Dr N.Keay, British Journal of Sport Medicine

Balance of recovery and adaptation for sports performance Dr N.Keay, British Association of Sport and Exercise Medicine

Inflammation: Why and How Much? Dr N.Keay, British Association of Sport and Exercise Medicine

Clusters of Athletes – A follow on from RED-S blog series to put forward impact of RED-S on athlete underperformance  Dr N.Keay, British Association of Sport and Exercise Medicine

Optimal Health: For All Athletes! Part 4 – Mechanisms Dr N.Keay, British Association of Sport and Exercise Medicine

The potential of endurance exercise-derived exosomes to treat metabolic diseases Nature Reviews Endocrinology

Exosomes as Mediators of the Systemic Adaptations to Endurance Exercise Cold Spring Harbor Perspectives in Medicine

Genomic and transcriptomic predictors of response levels to endurance exercise training
Journal of Physiology

Adaptations to endurance training depend on exercise-induced oxidative stress: exploiting redox inter-individual variability Acta Physiologica

Mechanical basis of bone strength: influence of bone material, bone structure and muscle action Journal of Musculoskeletal and Neuronal Interactions

The Crosstalk between the Gut Microbiota and Mitochondria during Exercise Frontiers in Physiology

Leaky Gut As a Danger Signal for Autoimmune Diseases Frontiers in Immunology

Metabolic Flexibility in Health and Disease Cell Metabolism

Hormones and Sports Performance

PPARδ Promotes Running Endurance by Preserving Glucose Cell Metabolism