Nutritional Coaching Strategy to Modulate Training Efficiency

75th Nestlé Nutrition Institute Workshop, Mallorca, December 2011

K. D. Tipton, L. J. C. van Loon, K.D., Tipton, L.J.C., van Loon, K. D. Tipton, L. J. C. van Loon

• Publisher: S. Karger
• Year: 2013
• Print ISBN: 9783318023329
• eBook ISBN: 9783318023336
• Topic: Medicine
• Subtopic: Endocrinology & Metabolism

Regular training and adequate nutrition are key factors in modulating exercise performance: Optimal performance requires a healthy diet adapted to the specific demands of the individual athlete's training and competition. Research has shown an impact of dietary intervention on the modulation of the skeletal muscle adaptive response to prolonged exercise training. Proper nutritional coaching should therefore not be restricted to the competitive events, but needs to be applied throughout both training and competition, each with its specific requirements regarding nutrient provision. Proper nutritional counseling will thus improve exercise training efficiency and ultimately increase performance capacity. Moreover, dietary counseling to modulate training efficiency is also relevant to the general public and the more frail clinically compromised patient groups. This book provides a solid scientific basis to help the reader define key targets for future interventions and develop new insights into the complex interaction between nutrition and exercise.

Tipton KD, van Loon LJC (eds): Nutritional Coaching Strategy to Modulate Training Efficiency.
Nestlé Nutr Inst Workshop Ser, vol 75, pp 27–40, (DOI: 10.1159/000345815)
Nestec Ltd., Vevey/S. Karger AG., Basel, © 2013

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Influence of Dietary Nitrate Supplementation on Exercise Tolerance and Performance

Andrew M. Jones · Anni Vanhatalo · Stephen J. Bailey

Sport and Health Sciences, College of Life and Environmental Sciences, University of Exeter, Exeter, UK

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Abstract

Several recent studies indicate that supplementation of the diet with inorganic nitrate results in a significant reduction in pulmonary O₂ uptake during sub-maximal exercise, an effect that appears to be related to enhanced skeletal muscle efficiency. The physiological mechanisms responsible for this effect are not completely understood but are presumably linked to the bioconversion of ingested nitrate into nitrite and thence to nitric oxide. Nitrite and/or nitric oxide may influence muscle contractile efficiency perhaps via effects on sarcoplasmic reticulum calcium handling or actin-myosin interaction, and may also improve the efficiency of mitochondrial oxidative phosphorylation. A reduced O₂ cost of exercise can be observed within 3 h of the consumption of 5-6 mmol of nitrate, and this effect can be preserved for at least 15 days provided that the same ‘dose’ of nitrate is consumed daily. A reduced O₂ cost of exercise following nitrate supplementation has now been reported for several types of exercise including cycling, walking, running, and knee extension exercise. Dietary nitrate supplementation has been reported to extend the time to exhaustion during high-intensity constant work rate exercise by 16-25% and to enhance cycling performance over 4, 10, and 16.1 km by 1-2% in recreationally active and moderately trained subjects. Although nitrate appears to be a promising ‘new’ ergogenic aid, additional research is required to determine the scope of its effects in different populations and different types of exercise.

Copyright © 2013 Nestec Ltd., Vevey/S. Karger AG, Basel

The Nitrate-Nitrite-Nitric Oxide Pathway

Nitric oxide (NO) is an important physiological signaling molecule that can modulate skeletal muscle function through its role in the regulation of blood flow, contractility, glucose and calcium homeostasis, and mitochondrial respiration and biogenesis [1]. Until quite recently, it was considered that NO was generated solely through the oxidation of the amino acid L-arginine in a reaction catalyzed by NO synthase (NOS), and that nitrite (NO^-₂) and nitrate (NO^-₃) were inert by-products of this process [2]. However, it is now clear that these metabolites can be recycled back into bioactive NO under certain physiological conditions [3, 4]. The reduction of NO^-₃ to NO^-₂ and subsequently of NO^-₂ to NO may be important as a means to increase NO production when NO synthesis by the NOS enzymes is impaired [5] and in conditions of low oxygen availability, as may occur in skeletal muscle during exercise.

Table 1. Nitrate content (mg/100 g fresh weight) of selected vegetables

Nitrate content	Vegetable
Very high (>250)	beetroot, spinach, lettuce, rocket, celery, cress, chervil
High (100-250)	celeriac, fennel, leek, endive, parsley
Medium (50-100)	cabbage, savoy cabbage, turnip, dill
Low (20-50)	broccoli, carrot, cauliflower, cucumber, pumpkin
Very low (<20)	asparagus, aubergine, onion, mushroom, pea, pepper, potato, sweet potato, tomato

In addition to being created through the NOS-catalyzed production of NO from L-arginine, tissue concentrations of NO^-₃ and NO^-₂ can be increased by dietary means. Vegetables account for 60-80% of the daily NO^-₃ intake in a Western diet [6] with green leafy vegetables such as lettuce, spinach and beetroot being particularly rich in NO^-₃ [7] (table 1). Ingested inorganic NO^-₃ is rapidly absorbed from the gut and passes into the systemic circulation with peak plasma [NO^-₃] being observed approximately 60 min after ingestion [4]. While some 60% of the systemic NO^-₃ is excreted in the urine [4]), 25% passes into the enterosalivary circulation and becomes highly concentrated in the saliva [8]. In the mouth, facultative anaerobic bacteria on the surface of the tongue reduce NO^-₃ to NO^-₂ [9]. This NO^-₂ is swallowed and reduced to NO and other reactive nitrogen intermediates within the acidic environment of the stomach [10, 11]. However, some NO^-₂ is absorbed to increase circulating plasma [NO^-₂] with the peak concentration being attained 2-3 h following NO^-₃ ingestion [8, 12]. Therefore, dietary NO^-₃ supplementation represents a practical method to increase circulating plasma [NO^-₂] and thus NO bioavailability. This has been demonstrated after ingestion of sodium nitrate (NaNO^-₃) [8 and 13-15], potassium nitrate [16], as well as NO^-₃-rich beetroot juice [17-22]. Interestingly, the characteristic rise in plasma [NO^-₂] following an oral NO^-₃ bolus is largely abolished by the use of antibacterial mouthwash [23], indicating that the reduction of NO^-₃ to NO^-₂ in humans is critically dependent on the oral bacterial NO^-₃ reductases.

The final step in the NO^-₃-NO^-₂-NO pathway is the one electron reduction of NO^-₂ to NO. This reaction is potentiated in hypoxic [24] and acidic [25] environments such as those which may exist in skeletal muscle during exercise [26]. The existence of an alternative NO generation pathway is important as it promotes NO synthesis under conditions that would otherwise limit the production of NO from NOS, ensuring that NO synthesis can occur across a wide range of cellular O₂ tensions. It is important to note, however, that NO^-₂ may itself induce physiological effects independent of its reduction to NO [27].

The purpose of this paper is to provide a brief review of the available literature which supports a role for dietary nitrate supplementation in enhancing exercise performance in healthy humans. Given the importance of NO in vascular and metabolic control, there are sound theoretical reasons why augmenting NO bioavailability might be important in optimizing skeletal muscle function during exercise. Recent evidence indicates that elevating plasma [NO^-₂] through dietary nitrate supplementation is associated with enhanced muscle efficiency, fatigue resistance and performance. The mechanistic bases for this effect are considered and practical recommendations for nitrate supplementation by athletes are provided.

Nitrate and Exercise

In 2007, Larsen et al. [15] reported that 3 days of NaNO^-₃ supplementation increased plasma [NO^-₂] and reduced the O₂ cost of sub-ma...

Table of contents

• Cover Page
• Front Matter
• Nutritional Strategies to Modulate the Adaptive Response to Endurance Training
• Practical Considerations for Bicarbonate Loading and Sports Performance
• Influence of Dietary Nitrate Supplementation on Exercise Tolerance and Performance
• Nutritional Strategies to Support Adaptation to High-Intensity Interval Training in Team Sports
• Dietary Strategies to Attenuate Muscle Loss during Recovery from Injury
• The New Carbohydrate Intake Recommendations
• Role of Dietary Protein in Post-Exercise Muscle Reconditioning
• Nutritional Support to Maintain Proper Immune Status during Intense Training
• Use of β-Alanine as an Ergogenic Aid
• Vitamin D Supplementation in Athletes
• Weight Management in the Performance Athlete
• Concluding Remarks: Nutritional Strategies to Support the Adaptive Response to Prolonged Exercise Training
• Subject Index