The importance of nutrition in sport was first recognised by the ancient Olympians and today, there remains wide spread acceptance of its role in improving sports performance as well as general health. In fact it has been stated “no single factor plays a greater role in optimizing performance than diet”.
Our blog this week has been written by Miranda Harris, Nutritional Therapist, University Lecturer and keen athlete. Miranda will be talking at our May event about the physical and psychological effects of exercise on the body’s systems and how a personalised nutritional approach can play a part in enhancing individual performance, while maintaining optimum health and helping to prevent injury and aid recovery. In this week’s blog Miranda focuses on the importance of the right type, quantities and timing of macronutrients.
The importance of personalised nutrition for optimum performance and health
By meeting energy requirements, the right type of macronutrients and the proper timing of nutrients in the diet, training adaptations may be optimised and thus performance improved. In addition, consideration of micronutrient requirements is equally important due to the added demands of exercise. Conversely by not meeting these needs to augment physiological changes, muscle mass and strength may be lost, there may be increased susceptibility to both illness and injury, delayed recovery of fatigue after exercise and increased prevalence of overreaching and overtraining, leading to reduced athletic performance and poor health. As with all clients, an integrated approach needs to be adopted, with underlying pathophysiology and symptom manifestation e.g. frequent upper respiratory tract infections or gut issues factored in, as well as lifestyle demands, which may include work and family.
Exercise benefits are far-reaching: Exercise may help to lower the risk factors of many non-communicable chronic diseases such as cardiovascular disease (CVD), Type 2 Diabetes Mellitus (T2DM) and cancer. It may contribute to a healthy lifestyle, and even slow down the ageing process. Fitness benefits include aerobic and muscular endurance, increased muscular strength and flexibility, improved heart rate recovery and reduced fatigue. Metabolic enhancements may reduce HBAc1 and fasting blood glucose, aid weight management and body fat loss, and ameliorate blood lipid abnormalities. Psychological effects are well-reported, and moderate aerobic exercise has been shown to lower symptoms of depression and anxiety.
However there are certain negative effects of exercise to consider. While the Female Athlete Triad is a well-known syndrome of disordered eating, menstrual dysfunction and low bone mineral density, an extension of this Triad has been observed in men and women, known as Relative Energy Deficiency in Sport (RED-S). This is where energy intake is insufficient to meet the needs of body functions and has a range of short and long-term consequences, which include decreased endurance and training response, reduced muscle strength and increased risk of injury, impaired judgement and coordination, and increased incidence of irritability and depression.
Gastrointestinal symptoms are common in endurance sports, caused by mechanical factors such as impact (running) and posture (cycling), and physiological factors, which include gut perfusion, motility, and gut barrier function. Needless to say nutrition may impact negatively due to increased intake of carbohydrate substances like fructose, and other simple sugars, as well as inadequate hydration resulting in a higher concentration of carbohydrate than can be absorbed. The frequent use of non-steroidal anti-inflammatory drugs (NSAID) may exacerbate these effects.
It is has been reported that moderate and regular exercise may be beneficial for immune function, with upregulation of the antioxidant defense system and mobilisation of certain anti-inflammatory immune cells occurring after moderate intensity. Conversely pro-inflammatory cytokines (IL1β; TNFα) have been associated with intense and/or prolonged training or competing for events such as marathons and Ironman, which may lead to immunosuppression and increased susceptibility to illness and infection.
Endocrine disruptions involve the sympathetic nervous system and the hypothalamic-pituitary-adrenal axis, further compromising immune function and leading to overreaching, or in severe instances, overtraining, a more serious condition on the continuum, which affects other physiological and psychological functions adversely. If this goes undetected, it may result in ‘burn out’ and long periods of rest may be required thereafter.
Fortunately a personalised and holistic nutritional approach may help to prevent this occurring. Unsurprisingly, our body systems are greatly influenced by caloric and macronutrient intake, in particular if partaking in prolonged or intensive bouts of exercise. This will be addressed in the following section.
Carbohydrate (CHO): Rather than recommend specific percentages of macronutrients, guidelines refer to grams (g)/kg/day (d), depending on volume and intensity of exercise. For example, light volume and intensity or skill-based sports may require as little as 3g/kg CHO/d, whereas for those training between 1 and 3 hours/d, if the exercise is moderate to intense, the athlete will need between 6-10g/kg/d and up to 12g/kg/d if the volume is over 4 hours/d. Evidence is equivocal as to the effectiveness of training on a lower CHO diet, and experience in clinical practice has shown some athletes manage well on lower amounts of CHO despite high volume training (ultraendurance marathon training of up to 75 miles/week), which equates to approximately 45% of total calorific intake, however the training is low to moderate intensity and therefore the athlete is more likely to be using energy released from fat, rather than from glycogen stores. As soon as the intensity increases, the CHO percentage required will increase accordingly.
The percentage of fat and CHO metabolised will be determined by a measuring method known as the non-protein respiratory exchange rate (RER), and represents the pulmonary exchange of carbon dioxide and oxygen under various metabolic and physiologic conditions. The higher the RER, the more CHO will be metabolised. Of course it is possible for the athlete to train accordingly, and there is evidence that low CHO strategies may enhance the metabolic adaptations of training, however there is a paradox – if the athlete is unable to train at high intensities due to insufficient CHO, they may not be able to make the necessary adaptations to improve!
As well as the amount of daily CHO, other factors to consider are types of CHO and timing of intake before, during and after exercise, known as nutrient timing. Advice on type of CHO would include complex CHO and sources of low Glycaemic Index (GI)/Glycaemic Load (GL) foods. In some situations, it may be advisable to avoid gluten rich foods, in particular bread and pasta, often eaten in abundance, especially before endurance events where a ‘pasta party’ is a popular pre-event ritual.
Alternative sources of CHO, such as oats, rice, quinoa, sweet potatoes and a wide range of fresh vegetables are worth considering, as well as some fruit. During exercise there is no need for CHO if duration is less than 60 minutes, unless the intensity is very high. Exogenous CHO oxidation may be limited by intestinal absorption and therefore combining different types of CHO, which use different transporters in the gut may be beneficial. For example a 2:1 ratio of glucose:fructose may increase oxidation rate from 1g/minute up to 1.5g/minute, however this needs to be tested in training as fructose can increase gastric upset.
It is also worth mentioning that there are also other health concerns that may be associated with fructose consumption (a lot of sports products are high in fructose and it would be advisable to look for product without fructose or with a lower percentage of fructose).
A useful method of calculating CHO requirements during training is to work on the formula of 0.6g/kg/hour. The type of exercise will dictate whether drinks or food are most suitable and can include CHO drinks, gels, gel blocks or easily digestible snacks, such as buckwheat pancakes and homemade energy bars. After exercise, if intense or prolonged i.e. one hour of high intensity interval training (HIIT), it is vital to replenish glycogen stores, and this can be achieved with high GL or GI foods or drinks, the latter is often preferable as it is an effective was to rehydrate as well.
Homemade smoothies with fresh fruit (berries and bananas), coconut oil or nut butter and yoghurt are one suggestion. Research has shown that milk or chocolate milk is an effective recovery drink with a combination of CHO, protein and fats, as well as electrolytes.
A final point to make about CHO: maintaining blood glucose levels particularly during intense or prolonged exercise may help to attenuate increases in certain hormones (adrenocorticotropic hormone (ACTH), cortisol and adrenaline) and reduce immune responses related to physiological stress and inflammation.
Protein: This is necessary for muscle repair and recovery, as well as muscle hypertrophy, with insufficient intake leading to muscle wasting and impaired performance. Protein supports immune function and hormonal balance, and can act as an energy source if necessary. Intake needs to be specifically tailored to the needs of the athlete, depending on training and competition demands. Similar to CHO, guidelines are based on type of training and range from 1g-2g/kg/d, with higher amounts needed for strength training. A healthy athlete may be able to tolerate this safely, however research shows that smaller and regular intake is preferable to large amounts at one time/meal.
An athlete, who wants to gain muscle mass, needs to be in a nitrogen balance as well as a positive energy balance to avoid the use of body tissue for energy metabolism. Where possible, protein should be sourced from food, however there may be a requirement for a powder supplement. Depending on preference types of powder include whey, casein, soya and hemp, some of which have a higher Biological Value than others. Absorption rates vary between the different powders, and therefore can be used at different times, depending on requirements (e.g. whey is fast absorbing so is ideal post exercise, whereas casein is much slower and may therefore be beneficial as an evening supplement).
Evidence on sports nutrition is equivocal but can often be explained by small sample sizes, difference in study design and methods of assessment, as well as unrealistic testing situations. Nutrient timing is not exempt from this and one aspect is the need for protein during exercise. Probably the time when protein would be beneficial is during ultraendurance events, when intensity is lower and time to completion may be over 24 hours.
Protein taken after exercise may help to shift the body from a catabolic to an anabolic state and reduce muscle breakdown as well as the production of cortisol and adrenaline. In the first few hours after exercise, muscle cells are sensitive to insulin and a combination of protein and CHO may help to increase muscle glycogen stores, reach positive net muscle protein balance and thus drive the synthesis of muscle protein, while inhibiting fat deposition. As to exact timing – as soon after endurance and strength training as is practical, and especially if the athlete is planning to train again the same day.
Fat: Sufficient fat is necessary for fat-soluble vitamins such as A, D, E and K; for the health of cell membranes, hormonal balance, nerve function and to modulate the effects of exercise, which include inflammation and oxidative stress. It can be utilised to replenish intramuscular triacylglycerol stores as well. Guidelines range from 0.5-1.5g/kg/d depending on body weight and composition goals. Sources of fat include nuts and seeds, oily fish, avocados and oils e.g. olive or coconut oil.
Supplements and ergogenic aids: A comprehensive appraisal is outside the scope of this blog, however it goes without saying that exercise may increase the demand for micronutrients involved in the different metabolic pathways and muscle biochemical adaptations. In particular those athletes who obtain suboptimal micronutrients from their diet, either because their diet is inadequate or because they restrict energy intake or certain food groups, may benefit from supplements such as a multi vitamin and mineral and additional magnesium and Vitamin D.
Supplementing with antioxidants to protect cell membranes from oxidative damage may not be necessary if the athlete has a well-developed endogenous antioxidant system and eats a diet rich in a wide variety of vegetables and some fruit, which would provide a range of phytonutrients and antioxidants. The same advice is applicable to fish oils to ameliorate any proinflammatory cytokines, food first! However, supplementing with live bacteria is often beneficial for many athletes considering the high frequency of gut symptoms.
Possible ergogenic aids include caffeine, creatine and nitrates (from beetroot), however a final point about any type of supplementing, is to be aware of the Anti Doping Guidelines and the World Anti-Doping Agency’s list of prohibited products. A recent BBC State of Sport investigation into doping in UK amateur sport revealed widespread use of performance enhancing substances, which include vitamin and L-carnitine injections, painkillers, steroids and amphetamines.
Miranda is a Nutritional Therapist and lecturer in Nutrition Therapy/Sports Nutrition at the University of Worcester. Her MSc in 2012 involved research into Nutrition Behaviour, Knowledge and Attitudes of competitive cyclists. She has 6 years private practice experience with a variety of clients. She provides personalised sports nutrition for a range of health and weight management issues, as well as performance goals. She has a great understanding of the importance of nutrition for performance but also for prevention and recovery of injury. Miranda is a keen athlete herself and is currently training for Iron Man 2018.
Many thanks to Miranda for this fantastic article. If you have any questions regarding the topics that have been raised, or any other health matters please do contact me (Clare) by phone or email at any time.
firstname.lastname@example.org, 01684 310099
The Cytoplan editorial team: Miranda Harris and Clare Daley
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Last updated on 12th April 2017 by cytoffice