Sports Nutrition
In the context of lifestyle medicine
In the course of their practice, integrative healthcare practitioners encounter patients who are on an exercise continuum, a continuum that ranges from sedentary adults with good intentions all the way to elite athletes. The rapid expansion of research under the umbrella term ‘sports nutrition’ is relevant not only to the very small percentage of North Americans who might be considered elite athletes, but may also be of use to more ordinary folks. We argue that central research findings related to nutritional influences on performance can be selectively used as a means to support sedentary adults who may be struggling with initiating and maintaining an exercise program. Low motivation and high perceived exertion, associated with a lowered mental outlook, are primary obstacles to exercise adherence. We hypothesize that the same nutritional variables that assist in athletic success, including the Mediterranean diet, plant-based antioxidants such as astaxanthin, cherries and beetjuice, fish oil, branched chain amino acids, and creatine, may be factors with much more broad public health implications in terms of being able to support lifestyle change among the ordinary North American population.
Introduction
There are volumes of international research attesting to the value of regular exercise in the reduction of chronic disease risk, overall mortality, and improvement in mental outlook (Blumenthal 2011). Whereas much has been written concerning the obesity epidemic and the prevalence of sedentary behavior, there are small signs of hope related to participation in moderate intensity physical activity among Canadians. For example, the latest statistics show a 4% increase in the number of physically active Canadians compared to this number in 2003 (Humphreys 2013), and separate data also reflects an increase in time spent in more intense levels of leisure time physical activity (Gilmour 2007). Participation in structured athletics, particularly among females in academic programs, has seen dramatic growth (Shriver 2013). Trends also suggest that North Americans are now more likely to receive physical activity recommendations from healthcare providers – a 40% increase over the last decade (Barnes 2012). Current medical students are more likely to be physically active than the general population, and a high level (69%) of Canadian medical students perceive exercise counseling to be highly relevant to clinical practice (Holtz 2013). Overall, this signals a beginning of a shift in perception, with both the public and the medical profession recognizing the importance of physical activity, and beginning to implement small lifestyle changes.
None of these encouraging signs, however, should be used to gloss over the staggering realities that despite these changes, only 15% of Canadian adults are meeting current guidelines for physical activity (Colley 2011). The same research suggesting that soon-to-be physicians believe exercise counseling to be important also shows that 86% of these graduating medical students consider themselves to be ill-prepared for such counseling: 70% reported no training on interacting with patients concerning exercise (Holtz 2013). The more salient point is that integrative healthcare practitioners are increasingly being called upon to provide exercise counseling to patients on a wide spectrum with regard to their comfort and familiarity with physical activity. This spectrum includes Canadians showing the beginnings of interest in the initiating a more active lifestyle for preventive health or for disease management, as well as those who are engaged in elite athletic endeavors. In between these extremes is the so-called “weekend warrior,” engaged in irregular patterns of sport participation, and/or those involved in regularly structured athletic programs such are recreational hockey. Part of the valued expertise that integrative healthcare practitioners bring to such encounters with this diverse group of patients is their in-depth knowledge of nutrition as it relates to dietary practices as well as nutritional supplementation.
The Relevance of Nutrition
The lessons learned from recent studies in the realm of nutrition in sports performance may, at first glance, seem to be of little importance, even trivial, when discussing serious and potentially life-threatening conditions, such as depression and obesity. However, investigations aimed at outcomes such as hitting the finish line tape faster, increasing endurance time to fatigue, or pushing just a bit more weight in strength training, ultimately provide nutritional insights with broader potential (Maughan 2011). It is becoming clear that nutrition is a variable relevant to all those who are on the exercise/sport continuum. It has the potential to influence motivation to participate in physical activity; to reduce perception of fatigue, a barrier that often impedes subsequent participation; to influence cognitive readiness for exercise; to enhance the enjoyment of the exercise experience; to enhance recovery for the next bout of physical activity; to minimize the risk of injury; and, genetic endowment and training being equal, to influence performance itself.
Although the term sports nutrition is often associated with having a primary role in support of the muscles (readiness for task, repair, anabolic processes etc.), nutritional influences are also of vital importance for motivation and performance, factors that are centrally regulated through the central nervous system (CNS). In sedentary adults, the motivation to engage in physical activity is low, and the normal post-exercise lift in mood is often not experienced. For example, in those with depression and/or obesity (vs. healthy/normal weight controls), motivation is a primary barrier to physical activity (Searle 2011). Among these patients, despite their awareness of the benefits of exercise, there are lower pleasure ratings reported after exercise, and perceived exertion is much higher while energy levels lower (Ekkekakis 2011), and this in turn impairs intent to participate in future physical activity (Weinstein 2010). On the other hand, a more positive perception of the experience of exercise encourages future participation (Annesi 2005, Kwan 2010). Integrative healthcare practitioners can take advantage of recent discoveries in nutritional sciences as a means to help break the cycle of negative affect and associated higher levels of perceived exertion, both of which contribute to a generalized exercise intolerance.
The Mediterranean Diet Example
Before discussing more reductionist investigations of single nutrients, e.g. branch chain amino acids, vitamins, minerals etc., it may be worthwhile to examine the influence of the broad aspects of diet as they related to mental outlook and performance. The Mediterranean (Med) diet provides what may be a gold standard for general support of physical and mental performance (Sofi 2010, 2008). The basis of what is now referred to as the contemporary Med diet has been in place for some 10,000 years (Berry 2011), and although details are sparse, there is certainly evidence that various dietary protocols were part of the training schemes of ancient athletes in the region (Grivetti 1997). In the modern context, there are clear characteristics of adherence to a Med diet vs. those consuming standard North American fare (Box 1).
The benefits of high adherence to a Med diet have been well described, ranging from protection against cognitive decline to reduction in the risk of metabolic syndrome (Sofi 2013, 2010, 2008). However, its association with positive mental outlook and resiliency against depressive symptoms bears mention. In a 5-year prospective study, greater adherence to the Med diet was associated with a 25-30% reduction in the risk of depressive symptoms (Sánchez-Villegas 2009). Moreover, adherence to the Med diet has also been linked to physical performance (Milaneschi 2011). In a recent study, adherence to the Med diet was linked to better objective performance results (measured via selfselected pace and walking speed over a 20m distance) in community-dwelling older adults (Shahar 2012). A recent intervention trial found that a 10-day Med diet significantly increased vigor, alertness and contentment among participants vs. controls (McMillan 2011). These are precisely the mood changes that would work towards undoing the motivational barriers to exercise. Among the many mechanisms whereby the Med diet can influence mental outlook, however its ability to reduce inflammatory markers is likely key. Intentional elevation of inflammatory cytokines in healthy adults has been shown to causes low-grade anxiety, depressive symptoms and mental fatigue (DellaGioia 2013, Reichenberg 2001), while Med diet interventions are known to reduce systemic markers of inflammation (Richard 2013). The Med diet may in this way psychologically augment the experience of exercise.
Specific Med Diet Elements
Among the specific components of the Med diet, fish intake and carotenoid intake (an accepted marker of fruit and vegetable consumption), have been linked to muscle strength and physical performance (Cesari 2004, Robinson 2008, Semba 2007). Mechanistically, there is evidence, although not unequivocal, that omega-3 fatty acid-rich fish oil can limit red blood cell deformability, muscle damage and overall inflammation associated with exercise (Mickleborough 2013). Furthermore, omega-3 fatty acids, and eicosapentaenoic acid (EPA) specifically, can potentially influence mental outlook in ways conducive to motivation (Hegarty 2013). Carotenoids serve as a marker of fruit and vegetable consumption, and their associated array of plant-based antioxidants; there is evidence to suggest that antioxidants may provide benefit in reducing the perception of effort during exercise. For example, compared to controls, heart rate and perceived exertion were reduced, and general fatigue score was decreased, when overweight adults were given 500mg of vitamin C for four weeks (Huck 2013).
Supplementation with the carotenoid astaxanthin for 90 days has been shown to reduce objective markers of muscle cell damage (serum creatine kinase) in elite soccer players (Djordjevic 2012). In another study, 28 days of astaxanthin supplementation (vs. placebo) has been shown to significantly improve cycling performance time among competitive cyclists (Earnest 2011). Other colorful dietary components, cherries for example, have been shown to be helpful in reducing postexercise pain, markers of muscle cell damage and inflammation, as well as a more rapid restoration of muscle strength (Bowtell 2011, Connolly 2006, Howatson 2010).
In addition to omega-3 fatty acids and antioxidants, the Med diet is also very high in dietary nitrate, a compound found in green leafy vegetables and beetroot that can increase blood flow in support of exercise performance. Close to a dozen studies using beetroot juice, nitrate-depleted beetroot juice and/or supplemental nitrate (Lidder 2013) have shown that dietary nitrate can improve exercise performance by increasing the efficiency of oxygen utilization (O2 cost is reduced) and increasing ATP synthesis. Among athletes and recreationally fit adults, beetroot significantly increases time to exhaustion (15%), enhances running velocity and reduces perceived exertion over longdistance running, and improves performance in team-sport exercise (Lansley 2011, Murphy 2012, Wylie 2013). One cup of beetjuice contains 5.5 mmol of nitrate, the equivalent of about 350mg; studies have used supplemental dosage forms containing up to 1500mg nitrate in healthy volunteers (Kapil 2010). These findings, showing more efficient metabolic pathways and lowered perceived exertion in particular, clearly suggest potential benefit in those sedentary adults/children who might contemplate initiating an exercise protocol. Of course, leafy green vegetables also carry significant levels of magnesium (Mg) per serving. Mg plays an important role in enzymatic support of muscular function, and even mild deficiency may compromise muscle performance (Matias 2010). Among athletes, dietary Mg intake is positively associated with various isokinetic strength variables and jumping performance tests, independent of total energy intake (Santos 2011). Mg intake is notoriously low in the general population, and this includes athletes and those with depressive disorders (Santos 2011, Yary 2013). Indeed, low Mg levels have been associated with depressive symptoms, chronic fatigue, and muscular pain. Mg is a versatile nutrient, supporting both muscle and mood; it is one that can help mitigate inflammation and oxidative stress, as well as support normal neurotransmitter functioning (Barbagallo 2009). Again, the relevance of Mg on the continuum, from those struggling to break a sedentary lifestyle to those in which sports performance is part of their identity, seems obvious.
General Considerations – Protein, Carbohydrate, Hydration
Scientific investigations in the realm of sports nutrition, particularly related to performance outcomes, have made it increasingly clear that a needs-based, individualized approach is most appropriate (Maughan 2011). That said, there are general nutritional considerations in supporting the process of exercise adaptation. All forms of exercise increase the rate of protein oxidation relative to the resting state; this translates into an increase in dietary protein demands (Phillips 2012). Of course, increased protein does not imply excess protein – 20 to 25 grams of high-quality mixed protein, or 6g of essential amino acids, consumed before or soon after exercise, is typically more than adequate to support remodeling and adaptive processes in muscle tissue subsequent to exercise (Maughan 2012). Branch chain amino acids (BCAA) have an anabolic effect on human muscle tissue (Borgenvik 2012), and supplemented alone or together with taurine, the BCAAs have been shown to reduce post-exercise muscle soreness (Howatson 2012, Ra 2013). Although not a protein, creatine is a significant nitrogen source, and one that can have value in preventing muscular fatigue (Rawson 2011) and loss of skill under conditions of sleep deprivation at relatively small (2-5g) doses (Cook 2011, Rawson 2011). In keeping with our contention that what is good for the athlete may be good for the sedentary adult seeking motivation, consider that 5g creatine per day has been recently shown to augment the effectiveness of antidepressant medications (Lyoo 2012).
Carbohydrate provides critical fuel for the initiation and maintenance of physical activity, training and/or competition. At lower intensity exercise, the body can take advantage of fat oxidation, however, with increasing intensity (particularly endurance exercise) the demand for carbohydrate utilization grows. Endurance exercise in the fasted state is generally not well tolerated in humans (Maughan 2010), and the increase in perceived effort in those without adequate carbohydrate reserves (glycogen) would certainly not encourage adherence to exercise as medicine (Maughan 2012). For post-exercise recovery efforts, although the science is incomplete, the preponderance of evidence suggests that a 2:1 ratio of carbohydrate to protein supplementation is helpful to restore glycogen reserves (Spaccarotella 2011).
The maintenance of proper hydration is yet another top line consideration in sports nutrition. Progressive loss of water and electrolytes as a result of increasing exercise intensity and duration is itself a cause of fatigue. The initiation of exercise in a dehydrated state has been shown to compromise performance in endurance (Goulet 2012). Again, the cognitive angle of even the mildest forms of dehydration cannot be overlooked. Recent studies in schoolchildren and adults have shown diminished cognitive performance in association with mild dehydration, and cognitive restoration produced by correction to a normal hydrated state (Edmonds 2013, Fadda 2012). Perceived exertion is higher among athletes in states of relatively modest hypohydration (Barr 1999), therefore this is likely to be compounded among those who are sedentary. Maintenance of normal hydration (sodium, potassium, magnesium and calcium) before, during, and after physical activity may go a long way toward encouraging adherence to an exercise program.
Conclusion
Studies derived from the burgeoning area of sports nutrition are not simply of relevance to the very small percentage of North Americans who might be considered elite athletes. IHPs can take advantage of sports nutrition research as a means to support a wide variety of patients/clients, perhaps most importantly those sedentary adults who are struggling with the difficult task of initiating and maintaining an exercise program. Low motivation and high perceived exertion, associated with a lowered mental outlook, are primary obstacles to exercise adherence – the same nutritional variables that might allow an athlete to collect a medal or push an extra rep on a weight bar, are the very factors that might have broad public health implications.
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