Why "Functional" Sports Nutrition? Today's athlete requires more than just a good diet and a handful of supplements.

It is unlikely that you will have seen the words; functional, sports and nutrition grouped together before. It is very much a new concept, which arises from the integration of a number of different disciplines. Functional Nutrition implies the field of Nutritional Therapy, Clinical Nutrition, Nutritional Medicine, Functional Medicine or whatever term you personally use for it. It is a discipline that is focused on integrative health and is gradually gaining credence within the CAM disciplines and is used by some allopathic practitioners.

The prevailing authority for nutrition in sports is the dietetic model, a practical discipline that analyses the nutritional adequacy of an athlete’s diet based on training demands. It quantitatively assesses the quantity and balance of nutrients consumed, with the aim of striving towards optimum sports performance. The American College of Sports Medicine (ACSM) position statement provides a good understanding of this approach. (1)

If you consider the pyramid in Figure 1 that is used by the ‘Athletes Performance’ Institute in the United States (2), there are 3 levels of dietary support: Functional Nutrition for Health; Performance Nutrition; and Supplements. Many athletes tend to jump straight to the top of the pyramid and enquire about ergogenic aids that may assist their athletic performance: nutritional practitioners may hear questions like ‘how much creatine do I need to run faster’ or ‘will ZMA speed my recovery’? The Sports Dietetic model works well for the middle tier of Performance Nutrition when individual differences are considered – this requires an adequate number of calories for the athlete’s sporting endeavour, the appropriate ratios between the macronutrients (protein, fat and carbohydrates), timing of food and drinks before, during and after exercise and sufficient micronutrient intake (vitamins and minerals).

Figure 1 

The base of the pyramid, Functional Nutrition for Health, is well explained by the Institute of Functional Medicine (3) in the United States. IFM was founded in 1990 and since then, Dr Jeffrey Bland and colleagues have been pursuing a quest to educate medical practitioners about ‘integrative medicine’, a concept that is well explained by their spider’s web in Figure 2. If one area of your health is imbalanced (the web is damaged), chances are that other areas are affected too. For example, it is recognised that an important function of the gastrointestinal tract is innate immunity (4,5), so depletion of friendly bacteria (dysbiosis) can imbalance systemic immunity, leading to inflammation in the joints, skin irritation and even mood and behavioural changes through the so-called gut-brain axis (5).

Figure 2

Although we may be inclined to place elite athletes on a pedestal of invincibility, whether they are world-class or weekend warriors, they are actually human and will require attention to the regulation of body systems like immunity, digestion, blood sugar control and adrenal health in the same way as general population. In addition, athletes have added stresses that are unique to their sport. For example, elite road cyclists may spend 4-6 hrs per day on their bike. It is unlikely that they can eat enough to balance the needs of their body day after day, so the adrenal glands may be heavily relied upon to support blood sugar levels. Regular ‘withdrawals’ from the body’s bank account on a long-term basis may result in overtraining, exhaustion, hypoglycaemia and performance decrements.

An example of the importance of establishing functional health before considering performance nutrition is demonstrated by research showing that gastrointestinal symptoms are experienced by 30% to 65% of long distance runners. (6) Pathophysiologic processes hypothesised to account for the symptoms included mechanical factors, reduced splanchnic blood flow, ischaemia, medication influences and the biochemical changes of exercise. The mucosal compromise seemed to allow entry of endotoxins into the portal (liver) circulation and the inflammatory cytokines TNF-α and IL-6 were measured, suggesting involvement of the detoxification and immune systems.

Within the Functional Sports Nutrition (FSN) concept, sports people are recognised as individuals. Roger Williams coined the term ‘Biochemical Individuality’ in 1956. (7) He recognised physiological variations among people and how these related to individual responses to the environment and unique nutritional needs. Individual differences have also been recognised in the sports nutrition field. A quote from Paul Greenhaff (8), one of the original researchers into creatine supplementation, exemplifies this: “It has been suggested by some researchers in the ergogenics field, that the same supplement can produce favourable results in some individuals, neutral effects in others and occasionally detrimental effects in some”.

FSN is also an interconnected concept that recognises strengths in lots of different modalities. A clinic in London called ‘Health Dept.’ used this integrated model: it comprised of Personal Training, Nutritional Therapy, Physiotherapy and Neurolinguistic Programming (NLP). Each practitioner communicated with each other towards the greater health of the client. Conversely, the Dept. of Health in the UK has many specialist departments (such as gastroenterology, ENT and cardio-respiratory medicine) that often treat the client in quite isolated ways. Ironically, it does not have a department called ‘health’. 

The challenges that are faced by any health system before it gains acceptance is that scientific validation is often required. Research has evolved over the years into expected standards of clinical testing that will make a study worthy of submission into a peer-reviewed scientific journal. Hence, in sports and nutrition, double-blind, placebo-controlled studies have high levels of credibility – the trouble is that in order to check if a nutrient has a certain effect on the body, a very specific research question must be asked. For example, does Vitamin C supplementation induce power increases in a 30-sec cycle test? It is a specific ‘does x influence y’ question. The human body, though, is a non-linear, higher-order, integrated system where the effect of one nutrient will depend on the activities of many other nutrients and systems in the body (as the IFM web shows). Integrated understanding of the body will therefore require research capable of exploring complexity.

Building up a scientific rationale for a new systems approach is challenging, but ideas can be adopted from other disciplines. A good starting point from the field of exercise physiology is the question of what causes fatigue in the body. Scientists have been debating this point for years and testing their theories through rigorous scientific studies.

Theories include (9):

  • - Cardiovascular Model – endurance performance is limited by the ability of the heart to beat.
  • - Energy Supply Model – performance is limited by the ability to produce ATP from aerobic and anaerobic metabolism.
  • - Energy Depletion Model – in events lasting more than 2-3hrs, glycogen depletion limits athletic performance.

Although all these models make sense in their own way and will certainly play a role in fatigue, each one is very isolated to peripheral mechanisms. Prof. Tim Noakes popularised the concept of the Central Governor (10,11), which is illustrated in Figure 3. It suggests that ultimately fatigue is regulated at higher centres in the brain – this notion was supported by several observations, including the fact that endurance performance seemed to be boosted by elevated levels of stimulating neurotransmitters (dopamine) and reduced levels of relaxing neurotransmitters (serotonin). The model recognises that the peripheral mechanisms will feedback to the brain, but the ultimate control resides in the higher centres. This thinking also matches what you can learn about peripheral feedback mechanisms from basic physiology texts – for example, chemoreceptors detect the partial pressure of oxygen and carbon dioxide in the carotid arteries and aorta and feedback the information to the cardiovascular centres in the brain. (12) Peripheral adjustments are then made based on all of the information available to the brain. The central model is a sophisticated and integrated model of explaining fatigue and could be seen to include input from unconscious parts of the brain that would process ‘prior learning’, something that would certainly contribute to how much an athlete can ‘give’ in competition.

Figure 3 

You can add one more layer to the Central Governor model and explore the field of Psycho-neuro-immunology (PNI). PNI is a convergence of disciplines, including behavioural science, neuroscience, endocrinology and immunology (13) and is an understanding that your conscious and unconscious thought, your spirituality and your nervous system can affect immunity and related body systems. This mind-body approach echoes the philosophies of ancient traditional medicine such as Traditional Chinese Medicine (TCM) or Indian medicine (Ayurveda), which have until recently, not received recognition by Western medicine. The discoveries of neuropeptides and their involvement in our emotions by the Molecular Biologist Candace Pert (14), has added a great deal of scientific credibility to these ancient methodologies and modern mind-body awareness.

When assessing an athlete, all of the body systems should be considered in a functional way (Figure 2) as you would do with general population. Of particular interest in sporting populations might be the following areas:

  • - Oxidative Stress and Antioxidant Support – increased concentration of oxygen-stress when training. Compromised detoxification increases demands.
  • - Inflammation – may be systemic due to high training loads and imbalanced metabolic function and/or local due to specific sporting traumas
  • - Acid-Alkaline Balance – metabolic acidosis may be of concern in endurance athletes undergoing a combination of high-volume and high-intensity training
  • - Energy Pathways – as an example of a functional approach, this is considered in detail below

Energy Pathways

Every exercise physiology student learns about the energy pathways – the breakdown of glucose or glycogen by glycolysis; lactic acid production in an anaerobic environment; use of the Krebs cycle in an aerobic environment and oxidative phosphorylation to produce ATP, the chemical form of energy.

What is generally not taught or written in text books, is the reliance of these pathways on enzyme cofactors (vitamins and minerals that make the conversions possible). For example, glycolysis and the Krebs cycle rely on B-vitamins, lipoic acid and the minerals iron, magnesium and manganese. (15) Oxidative phosphorylation additionally needs Coenzyme Q10 (16), while fat metabolism has a requirement for l-carnitine. (15) So, when athletes display signs of fatigue or overtraining, it is worth assessing micronutrient sufficiency. However, thinking in an integrated way, it is important to note that these nutrients may be fractioned off to a system or pathway with more immediate needs. For example the adrenal glands, which come under pressure during heavy training or life stresses, are reliant on B-vitamins and magnesium. (17) Additionally, detoxification pathways are reliant on certain B-vitamins (18), so simply by focusing your therapy on the energy pathways, you will not necessarily cover the needs of other systems.

It should be clear from this example that all of our systems are interconnected and can support or deplete one another. This is where the functional method of thinking, while potentially more complex, can provide longer-term treatment than the isolated cause and effect ideology.  

Functional Testing

Functional laboratory testing is available at a small number of speciality laboratories and is used by Nutritional Therapists and Integrative Medical Practitioners in the UK. The Genova Lab (19) in New Malden, Surrey processes most functional testing in the country.

Any test that might be used within the general population is relevant to an athlete if the practitioner notes that particular imbalance during history taking. Markers of immunity, inflammation, oxidative stress, digestion and detoxification may be implicated in individual cases. From a functional perspective, 3 particularly useful tests to use with athletes are the Metabolic Analysis Profile (MAP), Amino Acids (or the combined ‘ONE” test) and the Adrenal Stress Profile.

With a good understanding of a number of biochemical pathways, or a willingness to learn, the ONE test with around 80 markers can reveal a wealth of information. The MAP part of the test has markers for intestinal dysbiosis and absorption; glycolysis, Krebs cycle and fatty acid metabolism; methylation; neurotransmitters and general co-factor need. Since amino acids are structural building blocks, you can learn about many bodily functions. In particular, Branch Chain Amino Acids (Leucine, Isoleucine & Valine) are essential for maintaining skeletal muscle health and their levels can reflect an anabolic or catabolic environment (15, 20); glutamine is also broken down during high volume exercise and is a fuel for immune and brain cells (20); tyrosine and phenyl-alanine supply adrenaline, non-adrenaline and dopamine (20); collagen is made of proline, lysine and glycine, along with Vitamin C for cross-linking. (15) Glutathione, part of the enzyme antioxidant system, is up-regulated during exercise training (21) due to the demands of increased oxidative stress. It is made of glutamine, cysteine and glycine and requires the co-factor selenium for function. (22)

The Adrenal Stress Index is an invaluable tool to monitor an athlete for overtraining and lifestyle stresses. It has been the feature of a prior publication (23) and will be discussed in future editions of this journal.

Returning to the pyramid in Figure 1, based on needs of the athlete that are assessed by history taking, physical examination and possibly laboratory testing, the nutritional practitioner will set dietary recommendations. Food choices will be based on functional needs such as: digestive and detoxification, allergies and intolerances, inflammation, stress and overtraining and the social-cultural position of the athlete. In addition, performance nutrition requires adequate quantity of food for the training loads of the athlete, while also recognising individual differences in macronutrient needs – Metabolic Typing is one such model that recognises varying metabolic requirements. (24) Several on-line facilities can assess an athlete’s diet for caloric consumption plus macro- and micronutrient intakes. (25, 26)   

Most athletes will benefit from some nutritional supplements. Obvious choices might include a comprehensive multi-nutrient and antioxidant – the exact formula can be guided by the athlete’s history and test results if taken. Other possible supplements may include support for: digestion, detoxification, adrenal and sex hormones, immunity, inflammation and blood sugar. In addition, all athletes are advised to make appropriate use of sports and recovery drinks and may benefit from educated use of ergogenic aids (supplements that are purported to aid performance). This final step in the nutritional process will conclude the top of the pyramid.

Functional Sports Nutrition is simply a concept that suitably qualified and experienced nutritional practitioners are free to adopt. The International Society of Sports Nutrition aptly sums up the integrative nature of such a concept as we strive for the best care of our athletes: “The future of sports nutrition will dictate that we collectively will have to have a higher standard of care and education for counseling athletes, whether individually or in groups. The integration of many different disciplines (physiology, metabolism, psychology, etc.) will become a minimum mandatory set of disciplines for any aspiring sports nutritionist”. (27)


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