Diet, Food, Nutrition, and Exercise in Cystic Fibrosis

C H A P T E R

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Diet, Food, Nutrition, and Exercise in Cystic Fibrosis Andrea Kench1, Hiran Selvadurai2 1Department

of Nutrition & Dietetics and Respiratory Medicine, The Children’s Hospital Westmead, Westmead, NSW, Australia; 2Respiratory Medicine, The Children’s Hospital Westmead, Westmead, NSW, Australia

36.1  NUTRITION CONSIDERATIONS FOR EXERCISE Optimizing nutrition status is an important part of therapy for the cystic fibrosis (CF) patient and can significantly affect patient outcomes. The link between body mass index (BMI) and lung function forced expiratory volume in 1 s (FEV1) is well documented [1–4], and since the introduction of pancreatic enzyme replacement therapy, a high-fat diet has been the backbone of the CF diet. With advances in therapies and improved life expectancy, nutrition advice is becoming increasingly tailored to individual needs. There is now evidence to support dietary modification for the management of multiple comorbidities, including cystic fibrosis related diabetes (CFRD), liver disease (CFLD), and transplantation. Although less common, weight management strategies for the overweight CF individual with raised lipid profiles are also becoming an issue and a consideration once thought unlikely. The role of nutrition in exercise for CF is an area of growing interest. It has been shown that declining nutrition status is associated with reduced activity levels and exercise capacity [5–8]. Optimizing nutrition from a young age and throughout childhood will not only affect overall CF outcomes but may also offset the decline in physical activity with age. Despite this, evidence to support nutrition recommendations for exercise in CF is limited. Further research is still required to first fully understand metabolism and substrate utilization for this population. This chapter will present the current evidence and best available recommendations for optimizing nutrition for CF patients when exercising.

Diet and Exercise in Cystic Fibrosis http://dx.doi.org/10.1016/B978-0-12-800051-9.00036-5

36.1.1  Energy Requirements with Exercise Determining energy requirements for exercise in healthy individuals can be difficult. In the practical setting, health professionals usually rely on predictive equations to give a rough estimate of total energy expenditure (EE). Multiple factors including the duration, frequency, and intensity of exercise as well as an individual’s age, body size, genetics, and fat-free mass can affect metabolism, substrate utilization, and total EE [9]. An imbalance in energy intake (EI) vs. expenditure can result in altered substrate utilization. A poor EI is usually associated with a lack of available carbohydrate, the initial fuel source for aerobic exercise. This results in the preferential metabolism of fat and lean tissue. The breakdown of lean tissue and muscle mass not only has detrimental effects on exercise and performance but can also compromise immune, endocrine, and m ­ usculoskeletal function [10]. EE in CF has been studied with often conflicting results. Some studies have found resting energy expenditure (REE) to not be elevated in the CF population [11–13], but most report REE to be elevated [14–18]. Despite this, there is strong evidence to support that a rise in REE is correlated with worsening lung disease [19]. In the practical setting, EE is difficult to calculate for the CF individual because the predictive equations used for the healthy population are not validated in CF. In the past, an estimate of 120–150% of the recommended daily intake for age and gender was recognized as a starting point to account for increased expenditure and losses via malabsorption [20–22]. It has now been recognized that individual variation in estimated energy requirements (EERs) is larger than

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36.  DIET, FOOD, NUTRITION, AND EXERCISE IN CYSTIC FIBROSIS

first thought. As per the 2005 Cystic Fibrosis Foundation Clinical Practice Recommendations, EI ranging from 110% to 200% of that for the healthy population is shown to result in weight gain for children and adults with CF [23]. Regardless of the method used to estimate EER in CF, health professionals are encouraged to recognize these figures as crude estimates only. A thorough nutritional assessment combined with experience and clinical judgment remains an important consideration. The literature describing the effect of exercise on EE in CF is similar to that of REE in that the results are varied. Some studies have found EE to be elevated during exercise with CF [17,24], but most report EE to be unchanged when compared with the healthy population [11,16,18,25]. Postexercise, EE has been shown to be elevated in CF [11,18]. This is thought to be a compensatory response to the ventilation-perfusion disparity in which higher ventilatory requirements result in an increased work of breathing postexercise [18]. As with the healthy population, it is difficult to endorse a one-size-fits-all recommendation for EI with exercise in CF. The effect of the type of exercise and individual characteristics (e.g., age, body size, genetics, and fat-free mass) as well as disease-specific genotype and phenotype considerations may all affect total EE with exercise.

36.1.2  Protein Requirements with Exercise Protein requirements are also difficult to estimate, especially for the active individual. A person’s age, sex, EI, and carbohydrate availability as well as the duration, intensity, and type of exercise will all affect an individual’s protein metabolism [9]. In practice, it is often recommended that protein requirements exceed the current recommended daily allowance of 0.8 g/kg body weight and 10–35% of total EI for healthy individuals over the age of 18 years [9]. This is especially the case for those participating in endurance or resistance training. Despite this, there is limited evidence to support the theory that protein intake should be increased with any form of exercise. Protein metabolism in CF has been found to be altered [26]. Malabsorption, increased nitrogen losses via feces and sputum, and altered protein metabolism all contribute to increased protein requirements for CF individuals. Protein catabolism in CF also increases with significant systemic inflammation, pulmonary disease, and nutrient deficits [26]. This is particularly the case with protein and energy deficits or in severe cases in which protein energy malnutrition is present. The result of protein and energy deficits and a catabolic state will ultimately affect growth for the CF individual and likely have a negative effect on lean body mass. In addition to this, it has been found that deficits in protein intake and EI result in reduced exercise tolerance and pulmonary muscle function [27].

Protein intake in the CF population generally exceeds the recommended daily intake for the healthy population that is based on age and gender. The intake of protein has also been found to increase as total daily EI increases [28,29]. Despite the lack of evidence to support specific protein recommendations for the CF population, it has been generally accepted that protein should contribute to approximately 15% of total EI for the CF individual [26]. As with most areas of CF sports nutrition, protein-specific requirements for exercise are yet to be determined. This does not take away from the importance of encouraging adequate nutrition and optimal body composition, specifically lean body mass, for the CF person participating in regular exercise.

36.1.3  Substrate Utilization with Exercise Substrate utilization during exercise has been studied extensively in the healthy population with a focus on athletes, training, and performance. Although the results of these studies are beyond the scope of this chapter, the summary of specific macronutrient recommendations for exercise, as outlined in Table 36.1, was developed with the underlying knowledge of substrate utilization during exercise. Substrate utilization in CF is an area of growing interest and research. To date, studies looking at substrate utilization focus on aerobic exercise and most use respiratory quotient (RQ) data to determine carbohydrate and fat utilization. The results of early studies indicate that during and after maximal and submaximal exercise, there is no difference in the RQ between CF patients and their matched controls [11,18]. This is suggestive that carbohydrate and therefore fat metabolism is unchanged during exercise for the CF individual. Spicher et al. [16], by analyzing the RQ, demonstrated that substrate utilization may be altered in CF. In this study, the RQ was elevated at rest and during exercise, suggesting that carbohydrate oxidation contributed to a greater percentage of EE in CF versus the controls [16]. Recently, Nguyen et al. studied whole-body oxidation rates of fat and carbohydrate during prolonged submaximal exercise in CF children [25]. To date, the results of this study provide the most comprehensive insight into substrate utilization in the CF population. Whole-body fat and carbohydrate oxidation and blood plasma fatty acid levels were analyzed for six CF boys and matched controls during two 30-min bouts of submaximal exercise at regular intervals. Substrate utilization was determined using gas exchange and oxidation calculations. Similar to Spicher, Nguyen found that substrate utilization is altered in CF [25]. The main results are summarized in the following subsections [25]. The rate (Figure 36.1) and total amount of fat oxidized were significantly lower in CF.

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36.1  Nutrition Considerations for Exercise

TABLE 36.1 Summary of the American College of Sports Medicine, American Dietetic Association, and Dietitians of Canada’s Joint Position Statement for Nutrition and Athletic Performance [9] Recommended Dietary Allowance Carbohydrate

6–10 g/kg

Protein

0.8 g/kg

Fat

Acceptable Macronutrient Density Range

Role and Considerations Blood glucose maintenance with exercise Muscle glycogen replacement Mid-exercise recommendations: • 30–60 g/h for blood glucose maintenance Postexercise recommendations: • 1–1.5 g/kg in the first 30 min and every 2 h for 4–6 h to replace glycogen stores Inconclusive evidence to support the recommendation of low glycemic index carbohydrates

10–35% energy intake

Limited evidence to support that athletes require greater than the recommended dietary allowance; however, in practice, athletes are being recommended the following: • Endurance training: 1.2–1.4 g/kg • Strength training: 1.2–1.7 g/kg It is important to recommend that adequate energy from carbohydrate is provided to ensure that additional protein and amino acids are reserved for protein synthesis and are not oxidized as a fuel source. When possible, natural protein sources from diet alone are encouraged over protein supplements.

20–30% energy intake

A breakdown of 10% saturated, 10% polyunsaturated, and 10% monounsaturated fat is recommended to ensure an adequate intake of all essential fatty acids.

FIGURE 36.1  Fat and carbohydrate oxidation in cystic fibrosis (CF)

35 Oxidation rate (mg/kg body weight/min)

patients vs. controls adapted from Nguyen et al. [25]. Each time point represents 6 min of exercise. Points 1 and 3 were taken between the 12th and 18th minutes and points 2 and 4 were taken between the 23rd and 29th minutes of each 30-min bout of exercise.

30 25 20 15 10 5 0

1

2

3

4

Set time points

Fat as a substrate contributing to total EE was also ­significantly lower (Figure 36.2). Carbohydrate oxidation rates remained unchanged in CF when compared with the controls that experienced the expected decline in carbohydrate oxidation over time (Figure 36.1). There was also no significant difference between the average rate and total carbohydrate oxidation between the two groups. Carbohydrate as a substrate contributing to total EE was significantly higher in CF (Figure 36.2). The CF cohort exhibited lower plasma free fatty acid (FFA) concentrations during exercise. Nguyen et al. concluded that CF children have altered fat metabolism that may be affected by the inability to

Fat oxidation CF

Fat oxidation control

Carbohydrate oxidation CF

Carbohydrate oxidation control

readily mobilize FFA. To date, there are no other published studies investigating the pathophysiology of altered substrate utilization in CF. Given the relative paucity of good evidence, it is difficult to provide the specific recommendations for exercise and sports nutrition for subjects with CF. However, with what we know to date, the strongest argument would be to support what is already recommended around carbohydrate consumption and exercise in the healthy population: Adequate carbohydrate should be consumed before and during exercise to ensure blood glucose maintenance, muscle glycogen replacement, and adequate substrate for fuel metabolism and amino acid preservation [9]. This is particularly important in CF, in which it is has been

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36.  DIET, FOOD, NUTRITION, AND EXERCISE IN CYSTIC FIBROSIS

FIGURE 36.2  Percentage of energy expenditure contribution of

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fat and carbohydrates in children with cystic fibrosis (CF) vs. controls. Adapted from Ref. [25]. WĞƌĐĞŶƚĞŶĞƌŐLJĐŽŶƚƌŝďƵƟŽŶ

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TABLE 36.2 Summary of the Micronutrient Considerations for Nutrition and Athletic Performance as per the American College of Sports Medicine Position Stand: Nutrition and Athletic Performance [9] Role and Considerations B vitamins

Thiamin, riboflavin, niacin, pyridoxine, pantothenic acid, and biotin: • Play an important role in energy production with exercise Folate and B12: • Involved in red blood cell production and tissue repair These vitamins can be at increased risk for the vegetarian or female athlete, especially those with disordered eating.

Antioxidants • Vitamin C and E • β-carotene • Selenium

Assist in the prevention of oxidative damage to cell membranes. These vitamins and trace elements are at greatest risk for people following a low-fat diet and those that have a poor intake of fruit, vegetables, and whole grains or have a restricted energy intake (EI).

Vitamin D

Plays an important role in bone health because it is involved in calcium absorption and the regulation of serum calcium and phosphorus levels.

Calcium

Involved primarily in the maintenance of blood calcium levels and bone health. It is also plays a role in the regulation of muscle contraction, nerve conduction, and blood clotting. Vitamin D and calcium together play a role in the maintenance of bone mineral density. Low bone mineral density is of particular concern for the female athlete. This is especially the case if EI is low and there is an inadequate intake of calcium-rich foods.

Iron

Primarily involved in the production of hemoglobin and myoglobin and the oxygen-carrying capacity of red blood cells. Deficiencies can result in anemia, impaired muscle function, and reduced work capacity. Iron deficiency in the athlete is most often a result of inadequate EI. The vegetarian diet; periods of rapid growth; and increased losses with donation, menstruation, sweat, urine, and feces should also be considered.

Zinc

Involved primarily in the growth, building, and repair of muscle, but it also plays a role in energy production and immune function. Deficiency is most commonly associated with vegetarian diets low in animal protein.

Magnesium

Plays a role in cellular metabolism. This includes glycolysis and fat and protein metabolism. It has also been linked to the regulation of membrane stability as well as neuromuscular, cardiovascular, immune, and hormonal functions.

shown that carbohydrate, as a substrate, contributes to a greater percentage of total EE and that postexercise energy requirements are elevated [16,25].

36.1.4  Micronutrient Considerations Vitamins and minerals play an important role in several of the body’s physiological processes. These include

energy production, hemoglobin synthesis, immune function, prevention against oxidative damage, and the maintenance of bone health [9]. Regular exercise has been shown to increase the body’s turnover and loss of some micronutrients [9]. As a result, micronutrient requirements for the repair, building, and maintenance of lean body tissue may be elevated [9]. The most common nutrients at risk for athletes are summarized in Table 36.2 [9].

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36.1  Nutrition Considerations for Exercise

When adequate EI and dietary variety is unable to be sustained, a m ­ ultivitamin is recommended [9]. The effect of exercise on micronutrient status in CF has not been studied. Fat-soluble vitamin (FSV) supplementation is the most common form of micronutrient supplementation in CF, especially for pancreatic-insufficient patients. Malabsorption, inadequate intake, liver disease, progressive lung disease, poor compliance with pancreatic enzyme replacement therapy, and vitamin supplementation as well as previous bowel resections can all affect the level of supplementation required to maintain FSV serum levels within the normal range [22]. Other nutrients of increasing interest in CF, as with exercise, include iron, calcium, zinc, and magnesium. Further information regarding these nutrients in CF is available in national CF nutrition guidelines and consensus documents [21–23].

36.1.5  Dietary Sports Supplements The use of dietary supplements and ergogenic aids in exercise performance is an ever evolving and often lucrative market. To date, very few ergogenic aids have been shown to significantly improve performance [30]. The most commonly used and available dietary supplements and ergogenic aids are listed in Table 36.3. The A–D grouping is according to the Australian Institute of Sport (AIS) group classification system [31]. More detailed information regarding each supplement, including supporting literature, can be found at www.ausport.gov.au/ais/nutrition/ supplements/classification_test. At present, there are no studies looking at the effect of ergogenic aids on exercise performance in CF. As a result, the use of any supplement and ergogenic aid in CF should be done with caution and after consultation with the treating physician. Considerations for use of these products in CF, as per the AIS grouping, are listed in Table 36.4.

36.1.6  Protein Supplements The effects of protein supplementation on the maintenance, repair, and synthesis of skeletal muscle remain an area of interest in sports nutrition. Studies looking at the effects of protein supplements originally focused on the use of specific amino acids [9]. Today the focus has shifted to recommending higher quality proteins, including whey, casein, and soy, with food sources being recommended over commercial protein powders [9]. Regardless of the protein source, for maximal skeletal muscle benefits, it is recommended that protein be consumed with adequate carbohydrate and around the time of training [32].

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Protein powders and amino acid supplements should be used with caution in CF because they are a potential source of contamination with illegal and banned substances. Patients with CFLD should first discuss any significant increase in protein intake with the treating gastroenterologist.

36.1.7  Key Recommendations and Practical Considerations With limited research specific to nutrition in exercise and CF, it is likely to be some time before evidence-based guidelines for this area will be possible. Until then, it would be reasonable to recommend that advice remains in line with the available pediatric and adult evidence-based general CF nutrition guidelines. Aspects of sports nutrition can then be applied after careful consideration. The following key recommendations include practical advice for how nutrition and exercise considerations can be applied to the CF population. 36.1.7.1  The Nutrition Assessment Always complete a thorough nutrition assessment before advising the CF patient on dietary modifications for exercise. Special considerations include   

• T  he effect of CF-related comorbidities (see chapter on CFRD) • Hydration (See Section 36.3) 36.1.7.2  Energy Requirements Consider the effect of exercise and disease severity when estimating energy requirements.   

1. C  hoose a predictive equation to calculate the resting metabolic rate (RMR).   The Harris–Benedict equation [33] (Table 36.5) is most often used for the healthy adult population when considering exercise requirements [9]. Most recently, the Institute of Medicine (IOM) has released the IOM equation [34] (Table 36.6) to replace the Harris–Benedict equation. Its use in the clinical and sporting environment is likely to increase; however, weight and height must be available for this calculation.   The Schofield equation [35] (Table 36.7) is often used in CF. 2. Include a physical activity level factor   Harris–Benedict [33] (Table 36.5), IOM [34] (Table 36.6), or Schofield [35] (Table 36.7). 3. Include a disease factor   Multiply the RMR by 1.1–2.0 depending on disease severity to account for the 110–200% increased losses and expenditure in CF [23].

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TABLE 36.3  Australian Institute of Sport Supplement Group Classification System [31] Group A Supported for Use in Specific Situations Sports drinks

Refer to section on hydration for more details

Sports confectionary and gels

A concentrated, compact, and convenient source of carbohydrate (65–70% in gels and 75–90% in confectionary) that may contain “active ingredients” including caffeine. They provide an excellent source of fuel and are easily digested.

Liquid meals

Usually powders that can be dissolved in water or milk, but ready-to-drink varieties are also available. They are typically high in carbohydrate, low in fat, and contain moderate amounts of protein as well as being fortified with vitamins and minerals.

Whey protein Sports bars

Primarily used as a concentrated form of carbohydrate to fuel athletes before, during, or after exercise. Also contain variable amounts of protein (5–30 g/serving) and micronutrients.

Calcium supplement

Refer to micronutrient considerations (Table 36.2).

Iron supplement

Refer to micronutrient considerations (Table 36.2).

Probiotics

Lactobacillus acidophilis and Bifidobacterium bifidum are the most commonly used and commercially available strains. An area of emerging sports nutrition research, but the general benefits include improved gastrointestinal and immune health and allergy prevention.

Multivitamin mineral

These are not found to be performance enhancing unless used to correct an existing deficiency. It is recommended that supplementation is considered if a deficiency exists or dietary quality is poor.

Vitamin D

Emerging evidence to support that strength, power, reaction time, and balance may be enhanced if provided with vitamin D supplementation to correct deficiency.

Electrolyte replacement

Used to replace losses via sweat during exercise and are a good alternative to sports drinks.

Caffeine

Has been shown to primarily affect the central nervous system (fatigue perception) but is also linked to adrenaline stimulation, fat mobilization, and muscle contractility. The diuretic effect of caffeine-containing beverages is minimal. Inconsistent evidence to support use as a performance enhancer and is no longer banned by the World ­ Anti-Doping Agency.

Creatine

Plays a role in the ATP-creatine phosphate pathway, in which ATP is the primary fuel source for high-intensity exercise of up to 10-s duration. Most beneficial for resistance and high-intensity interval training.

Bicarbonate

Most commonly used to act as a buffer in the blood because it plays a role in the maintenance of pH and electrolyte gradients between intracellular and extracellular environments. Used for anaerobic, high-intensity exercise to prevent muscle fatigue.

Group B Deserving of Further Research

Group C No Meaningful Proof of Beneficial Effects

Group D Banned or at High Risk of Contamination

β-alanine Beetroot juice/nitrate Antioxidants C and E Carnitine HMB Fish oils Probiotics for immune support Other polyphenols as antioxidants and anti-inflammatories

Ribose Coenzyme Q10 Vitamins outside of Group A use Ginseng Other herbals (coryceps, rhodiola, and rosea) Glucosamine Chromium picolinate Oxygenated waters MCT oils ZMA Inosine Pyruvate

Stimulants Ephedrine Strychnine Sibutramine Methylhexanamine Other herbal stimulants Prohormones/hormone boosters Androstenedione 19-norandrostenione/Ol Other prohormones Tribulus terrestris and other testosterone boosters DHEA

More information regarding each product can be found at http://www.ausport.gov.au/ais/nutrition/supplements/group_a. ATP, adenosine triphosphate; HMB, hydroxymethylbutyrate; MCT, medium-chain triglycerides; ZMA, zinc monomethionine aspartate and magnesium aspartate; DHEA, dehydroepiandrosterone.

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36.1  Nutrition Considerations for Exercise

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TABLE 36.4  Australian Institute of Sport Supplement Group Classification System [31] with Potential Considerations for People with CF

Considerations

Group A

Groups B–D

Known to be safe for use and appropriate for recommendation in CF: • Sports drinks and electrolyte replacement • Sports bars • Calcium, iron, vitamin D, and multivitamin supplements • Probiotics

The potential risk of using these products for the exercising CF patient include, but may not be limited to, medication interactions and harmful effects to the liver.

Should be used with caution in CF: • Sports gels and confectionary–CFRD considerations • Caffeine—not advisable for use in children • Creatine—no studies to support use in CF • Bicarbonate

Different regulatory laws regarding health and therapeutic claims exist among countries. With most products being available online, the ease of accessing dietary supplements and ergogenic aids has increased. Consumers need to be aware that not all packaging claims are scientifically proven. Several of these substances are banned by the World Anti-Doping Agency and are not permitted for use in competitive sport. There is significant risk that these products may be contaminated with other products not listed as active ingredients. This is again of particular concern for patients with CFLD. Some patients may not be forthcoming and willing to disclose their use. Adolescent and young adult males who regularly train in the gym setting are most likely to show interest in these products. Although most protein powders are usually safe, preworkouts are of particular concern because they often contain multiple supplements listed in these categories.

CF, cystic fibrosis; CFRD, cystic fibrosis related diabetes; CFLD, cystic fibrosis related liver disease.

TABLE 36.5  Harris–Benedict Equation and Physical Activity Levels [33] HARRIS BENEDICT EQUATION Males: RMR = 66.47 + (13.75 × wt) + (5 × ht) – (6.76 × age) Females: RMR = 65.51 + (9.56 × wt) + (1.85 × ht) − (4.68 × age) HARRIS PHYSICAL ACTIVITY LEVELS Activity Level

Activity Factor

Definition

Sedentary

1.2

No exercise—inactive.

Mild activity

1.375

Minimum of 20 min exercise 1–3 days each week or the maintenance of a busy lifestyle including walking for long periods of time.

Moderate activity

1.55

Minimum of 30–60 min of intense exercise 3–4 times each week. This also includes labor intense occupations.

Heavy activity

1.7

≥60 min of intense exercise 5–7 times per week. This also includes those working in labor-intensive jobs.

Strenuous or very heavy exercise

1.9

Extremely active. This is most often athletes with demanding training schedules (multiple sessions daily). Some demanding jobs including shovel coal would also fall in this category.

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TABLE 36.6 Institute of Medicine Equation and Activity Levels [34] IOM EQUATION 0–2 years

EER = (89 × wt) − 100

Boys 3–18 years

EER = (88.5 − (61.9 × age) + PA × [(26.7 × wt) + (903 × ht)]

Girls 3–18 years

EER = (135.3 − (30.8 × age) + PA × [(10 × wt) + (934 × ht)]

Men >18 years

EER = (662 − (9.53 × age) + PA × [(15.91 × wt) + (539.6 × ht)]

Women >18 years

EER = (354 − (6.91 × age) + PA × [(9.36 × wt) + (726 × ht)]

IOM PHYSICAL ACTIVITY LEVELS Activity Level

Male Children

Female Children

Male Adults

Female Adults

Definition

Sedentary

1.0

1.0

1.0

1.0

Light physical activity required for independent living.

Low active

1.13

1.16

1.11

1.12

30 min of moderate— vigorous exercise daily.

Active

1.26

1.31

1.25

1.27

60 min of moderate— vigorous exercise daily.

Very active

1.42

1.56

1.48

1.45

≥60 min of moderate— vigorous exercise daily.

TABLE 36.7 Schofield Equation and Activity Levels [35] SCHOFIELD EQUATION Male 0–3 years

(0.249 × wt) − 0.127

Female 0–3 years

(0.244 × wt) − 0.130

Male 3–10 years

(0.095 × wt) + 2.11

Female 3–10 years

(0.085 × wt) + 2.033

Male 10–18 years

(0.074 × wt) + 2.754

Female 10–18 years

(0.056 × wt) + 2.898

Male 18–30 years

(0.063 × wt) + 2.896

Female 18–30 years

(0.062 × wt) + 2.036

Male 30–60 years

(0.048 × wt) + 3.653

Female 30–60 years

(0.034 × wt) + 3.538

Male 60+

(0.049 × wt) + 2.459

Female 60+

(0.038 × wt) + 2.75

SCHOFIELD ACTIVITY FACTORS Activity Level

Males

Females

Bed rest

1.2

1.2

Inactive.

Sedentary

1.3

1.3

Very physically inactive both at work and in leisure. Little to no exercise.

Lightly active

1.6

1.5

20 min of intense exercise 1–2 times per week or the daily routine includes some walking.

Moderately active

1.7

1.6

20–45 min of intense exercise 3–4 times per week or a job that contains a significant amount of walking or intensity.

Very active

2.1

1.9

≥60 min of intense exercise 5–7 times per week. This also includes those working in labor-intensive jobs.

Extremely active

2.4

2.2

Very-high intensity exercise on most days of the week. This usually applies to athletes with multiple daily training sessions.

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36.1  Nutrition Considerations for Exercise

36.1.7.3  Protein Requirements 1. Calculate protein requirements on the basis of the following recommendations for the healthy population [36]: Infants: 1.5 g/kg/day 1–3 years: 0.95 g/kg/day 4–14 years: 0.85 g/kg/day Adults: 0.8 g/kg/day 2. Determine if the calculated protein requirements fall within the acceptable macronutrient density range: Healthy population: 10–35% EI [36] CF population: minimum 15% EI [26]   

Given the importance of adequate protein with exercise, it would not be unreasonable to advise 15–35% EI from protein for all CF people engaging in regular exercise. 36.1.7.4  Energy Balance • Discourage patients and parents from limiting participation in sports and exercise because of the fear of burning too much energy. Parents often hesitate at the idea of encouraging too much physical activity for their child with CF because, if not balanced with the appropriate diet, it can result in energy deficits and weight loss. • From a young age, a team approach to promote the health benefits of exercise in CF as well as the role of nutrition may help reduce parental anxiety. 36.1.7.5  Macronutrient Recommendations • Further research on substrate utilization during exercise in CF is required before providing set macronutrient targets. • Table 36.8 provides practical considerations regarding macronutrient distribution and meal/ snack ideas for exercise and CF. 36.1.7.6  Micronutrient Recommendations • Many of the same micronutrients of concern with exercise are also at risk in the CF population, and it would be advisable to ensure adequate monitoring is completed for the CF patient involved in regular exercise. • Aim to monitor micronutrients at risk at a minimum of each year. • Supplementation should be according to biochemical profile and clinical status. • Consider the following when interpreting biochemical results: • Adherence to vitamin supplementation • Clinical status—acute illness and inflammation can affect some serum biochemical markers. This

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is particularly relevant for vitamin A and iron studies. • Seasonal variation—particularly with vitamin D • As per the healthy population, a multivitamin should only be required if a balanced diet with adequate energy is not able to be maintained. 36.1.7.7  The Type of Exercise • Consider the effect of different types of exercise on body composition. • Resistance (strength) training has been shown to improve total and fat-free mass when compared with aerobic training in CF [38]. 36.1.7.8  Dietary Supplements and Ergogenic Aids • Most dietary supplements and ergogenic aids should be used with caution and in consultation with the medical team. 36.1.7.9  Children and Sport 36.1.7.9.1 ENERGY

• A  im to maintain a positive energy balance to allow for periods of rapid growth during childhood and adolescence. • The effects of chronic negative energy balance include short stature, delayed puberty, irregular menstrual cycle, poor bone health, and an increased injury risk [30]. 36.1.7.9.2  MEALS AND SNACKS

• E  ncourage regular meals and snacks with good dietary variety. Fussy eating strategies should be discussed and used from a young age. • Encourage a protein food source with each meal and snack because children and adolescents have increased protein requirements for growth [30]. • Carbohydrates remain an important fuel source for children and should not be limited, but it is important to encourage good dental hygiene for the prevention of dental caries. 36.1.7.9.3  VITAMINS AND MINERALS

• C  alcium, iron, and zinc intake is often inadequate for children and adolescents, especially girls [30], and should be monitored closely in the pediatric CF population. 36.1.7.9.4  PERFORMANCE-ENHANCING SUBSTANCES

• T  here is no evidence to support the use of performance-enhancing substances in the pediatric population (<18 years of age) [30].

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TABLE 36.8  Practical Macronutrient and Food Considerations for People in CF Who Engage in Regular Exercise Considerations MACRONUTRIENTS Carbohydrate

General CF recommendations: • Relatively high intake is required to help meet energy requirements [22] (see chapter on CFRD for more details). During times of exercise: • Consider low glycemic index meal/snack options, especially for patients with CFRD (see chapter on CFRD for more details). • Avoid low-carbohydrate diets with exercise

Protein

Fat

General CF recommendations: • Requirements are thought to be elevated in CF because of increased losses with malabsorption, nitrogen losses in the feces and sputum, and a potential altered protein metabolism [22,26]. • Should account for ∼15% of total daily EI [26]. • In CF, protein intake usually increases as total daily EI increases [37]. During times of exercise: • Ensure adequate energy and carbohydrates are consumed with increased protein for best results. • Aim for natural protein food sources when possible. • Consider increasing protein intake up to 35% of total EI to align with the upper recommended range for adults. Note that 10–35% of energy from protein is recommended for healthy individuals over 18 years of age [9]. General CF recommendations: • Unrestricted intake (unless overweight). • Should account for ∼40% of total daily EI [22]. • Aim for >100 g/day for patients older than 5 years [22]. • Although not yet used by all CF centers, annual monitoring of lipid profiles is becoming increasingly common. During times of exercise: • A high-fat meal should only be discouraged immediately before exercise because it can slow gastric emptying and may consequently result in abdominal discomfort with exercise.

MEALS AND SNACKS Pre-exercise

As per advice for the general population, the pre-exercise meal should be as follows [9]: • Relatively low fat and fiber to promote gastric emptying • High in carbohydrate for blood glucose maintenance • Moderate in protein • A familiar food that is well tolerated • Combined with adequate fluid to maintain hydration Liquid meals would be an appropriate pre-exercise snack for the CF patient because they meet the pre-exercise meal recommendations and are food source familiar to many CF patients. Sports bars are another good option for use in CF.

During exercise

As per the general population, any exercise lasting longer than 1 h should include a carbohydrate fuel source [9]. There is no evidence to support that a CF patient requires carbohydrates for exercise <1 h duration; however, hydration is a priority (see Section 36.3). Sports drinks and oral rehydration solutions are highly recommended for use in CF, especially for the active patient.

Postexercise

As per advice for the general population, the postexercise meal should aim to replace all losses [9]: • High in energy with adequate carbohydrates to replace muscle glycogen stores • High protein to provide amino acids for muscle repair and growth • Adequate fluid and electrolytes to replace losses (see Section 36.3) Liquid meals are again a good and well-balanced postexercise snack for the busy CF patient. We are always aiming to replace losses without adding to the current burden of disease and expecting patients to eat a significantly larger quantity of food. Other options include sports bars and encouraging high-energy, high-fat fortification of familiar and preferred meals/snacks. For those patients interested in strength training to improve muscle bulk and therefore high-protein options, a protein shake would be appropriate for use in the postexercise period after discussion with the CF team.

CF, cystic fibrosis; CFRD, cystic fibrosis related diabetes; EI, energy intake.

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36.2  Hydration Considerations for Exercise

• M  uscle-building supplements are popular among adolescent males. When possible, natural protein food sources should be encouraged for use in CF, and any additional supplement should be discussed with the treating physician before use. 36.1.7.9.5  INFLUENCES ON FOOD CHOICES

• F  actors effecting food choices for adolescents should be considered before dietary changes. These include hunger, food cravings, timing of meals/ snacks, convenience, media, cost, body image, habits, mood, health benefits, parental effect, and the effect of peers [30]. 36.1.7.9.6 HYDRATION

• See Section 36.3.

36.2  HYDRATION CONSIDERATIONS FOR EXERCISE As with most areas of sports nutrition, evidence-based hydration guidelines for the exercising CF population are limited. With minimal research in the field, it is primarily the application of what we know in the healthy population that continues to drive recommendations for hydration in CF. Water is an essential part of the human body and significantly affects hydration because it is involved in the maintenance of blood volume and body temperature regulation and it allows muscle contractions to take place. The type of activity, environment, and clothing and the individual characteristics of size, genetics, heat acclimatization, training level, and age will also significantly influence hydration [39]. Dehydration is generally classified as more than 2% body mass loss from water [39], but signs and symptoms of dehydration have been reported with mild dehydration as low as 1% body mass loss [40]. These include physiological symptoms (increased heart rate and core body temperature) as well as impaired cognition and alertness [40]. Significant changes to an individual’s water intake can also alter cellular volume and affect the cellular functions of metabolism, hormone release, excitation, and cell proliferation or death [41]. Hydration and the effect of a person’s hydration status on exercise have been studied extensively in the healthy population. Many national and international sporting bodies including the International Olympic Committee [42], the American College of Sports Medicine (ACSM) [39], and AIS [43]

327

have released consensus documents and position statements highlighting specific hydration considerations and recommendations. Table 36.9 provides a brief summary of the ACSM hydration recommendations, including their evidence statement hierarchy. Fluid and electrolyte requirements during exercise largely depend on an individual’s sweat rate and sweat electrolyte losses. It is difficult to give a global recommendation for fluid and electrolyte replacement because the duration and intensity of exercise, environmental conditions, clothing, and individual characteristics of body weight, genetic predisposition, heat acclimatization, and metabolic efficiency all affect fluid and electrolyte losses [39]. In CF, it is postulated that dysregulation of the cystic fibrosis transmembrane conductance regulator (CFTR) alters the transport of sodium chloride across the cell membrane, which impairs hydration. Table 36.10 summarizes key points to consider when applying general hydration recommendations to the CF population. The risk and effect of dehydration during exercise for the CF individual has been highlighted in several case reports over the past two decades. In 1991, a ­24-year-old infantryman was diagnosed with CF after having collapsed with hyponatremia when training in warm climates [47]. He presented with exerciseassociated hyponatremia (EAH) and reported that in comparison to his colleagues, he would sweat more, consumed more water, and often noted salt crusts on his skin while training [47]. A similar case of a 48-yearold male who diagnosed with CF after a 30 year history of profuse sweating, muscle cramps, and salt crusts during exercise was published in 2007 [48]. Salt tablets were used to relieve muscle cramps and nausea before diagnosis for this individual [48]. Most recently, in 2012, a case of an adolescent with known CF presented with a case of hyponatremia-associated rhabdomyolysis after a summer football training session [49]. The authors of this case concluded that research is needed regarding the appropriate amount and composition of oral rehydration fluids in exercising individuals with CF because the physiology encountered in these patients provides a unique challenge to maintaining electrolyte balance and stimulation of thirst [49].

36.2.1  Key Recommendations Although more research is required in this area to establish evidence-based practice guidelines, it would not be unreasonable to recommend the following

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TABLE 36.9 Summary of the ACSM Position Stand for Exercise and Fluid Replacement ACSM Evidence Statementa [39] Fluid and electrolyte requirements during exercise

Evidence category A: Water and electrolyte losses differ considerably between individuals and are affected by the type of activity. Sustained exercise in warm weather can result in substantial water and electrolyte losses. If the losses are not replaced, then dehydration will occur.

Fluid and electrolyte requirements postexercise

Evidence category A: It is recommended that sweat electrolyte losses should be replaced fully.

Hydration assessment

Evidence category A: An individual’s fluid replacement requirements for a specific exercise and environmental condition can be determined by body weight changes pre- and postexercise because percentage change in body weight is reflective of sweat losses during exercise. Evidence category B: Urine and body weight measurements can be used by individuals to monitor their hydration status.

Hydration and performance

Evidence category A: Dehydration is classified as >2% body weight loss and can be associated with reduced aerobic exercise performance (especially in warm-hot weather).

Other health outcomes: 1. Hyponatremia 2. Muscle cramps

Evidence category A: Exercise-associated hyponatremia is rare but can occur if fluid consumption exceeds the rate of sweating. Evidence category B: Exercise-associated hyponatremia is more likely if sweat sodium losses are large and body mass (and total body water) is small. Evidence category C: Skeletal muscle cramps can be a result of dehydration, sodium depletion, and muscle fatigue. Muscle cramps are more likely in those individuals who sweat more and have large sweat sodium losses.

Dietary considerations

Evidence category A: The consumption of a meal (especially sodium-containing foods) before exercise can help retain water and promote euhydration. It is also important that all sweat electrolyte losses are fully replaced. Evidence category B: Caffeine has a limited effect on hydration status and daily urine output. The consumption of alcohol can hinder rehydration because it increases urine output.

ACSM, American College of Sports Medicine. aEvidence statement hierarchy: A, recommendation is based on consistent and good quality experimental evidence (morbidity, mortality, exercise and cognitive performance, ­physiologic responses); B, recommendation is based on inconsistent or limited quality experimental evidence; C, recommendation is based on consensus, usual practice, opinion, disease oriented evidence, case series or studies of diagnosis, treatment, prevention, or screening, or extrapolations from quasi experimental research.

to individuals with CF who participate in regular exercise:   

1. M  onitor hydration status: This is most important for CF individuals exercising for extended periods of time (especially in the heat). Urine color: a. A practical and convenient indicator of hydration (not scientifically validated) b. Aim for urine that is pale yellow in color (dark urine is indicative of dehydration) Weight change: a. Monitoring weight pre- and postexercise will give a rough estimation of lost fluids and provide a starting point for rehydration. One-kilogram weight loss approximately equates to a 1-l fluid deficit. b. Fluid and electrolyte losses continue postexercise via sweat and urine. Aim to replace 125–150% of the fluid deficit over a period of 2–6 h postexercise [64]. 2. Encourage sodium-containing fluids (and foods): Sports drinks and oral rehydration solutions are beneficial to the exercising CF population. Compares the sodium

content of sports drinks commonly consumed with exercise. Note that sugar-free alternatives may be considered for the CFRD population. 3. Do not rely on thirst: Significant fluid losses have occurred before the onset of the thirst mechanism. 4. Look out for signs of dehydration: Early signs of dehydration can include fatigue and lethargy, headache, nausea, muscle cramps, concentrated and dark urine, and flushed skin. If nauseous, then encourage frequent small volumes. 5. Special considerations for children: Children and particularly those with CF have an attenuated thirst drive and do not stop for fluids as regularly as adults. They should always be encouraged to drink regularly. a. Offer flavored, cooled, and sodium-containing drinks in an attempt to improve voluntary rehydration. b. When combined with sports drinks, salty snacks will help bring the sodium intake closer to more than 50 mmol/L and stimulate thirst. c. Allow children plenty of time to rest, stay cool, refuel, rehydrate, and ultimately prevent dehydration.

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TABLE 36.10  Hydration Considerations for the Healthy and CF Population [39] CF Population

Hydration assessment

Daily water balance depends on the net difference between water gain (liquid or food and the metabolic production of water) and loss (respiratory, gastrointestinal, renal, and sweat losses) [44]. Sweating is the main source of water loss during exercise [39]. There is no gold standard for hydration assessment of athletes. The most practical and commonly used protocols include the urine specific gravity assessment and fluid balance assessment [43].

No CF-specific recommendations exist. It is important to remember the considerable burden of disease that CF individuals already endure before implementing hydration assessment strategies. How would the commonly used protocols in the healthy population affect the quality of life of a CF individual?

Sweating rate, electrolyte losses, and EAH

Sweating rates: • Individual sweating rates are thought to vary from 0.5 to 2.0 l/h with sodium losses of 35 mEq/L (10–70 mEq/L) [39]. Electrolyte losses: • The loss of electrolytes in sweat depends on the volume of sweat lost and concentration of sweat electrolytes [39]. • As the rate of sweating increases, the concentration of sodium and chloride lost in sweat also increases [39]. EAH: • EAH is defined as a serum sodium concentration <135 mmol/L [45] and most commonly results from the overconsumption of fluids at a rate that exceeds the sweating rate [46].

Sweating rates: • CF individuals are reported to sweat more than their non-CF counterparts [47–49]. Electrolyte losses and EAH: • CFTR dysfunction results in the excessive loss of sodium and chloride via sweat gland ducts and places CF individuals at a greater risk of dehydration, hyponatremia, and hypochloridemia [50,51]. • The sodium concentration of sweat for CF individuals is usually 3–5 times that of the healthy population [52]. • The excretion of sweat that is nearly isotonic to plasma increases the CF individual’s risk of dehydration and hyponatremia during any prolonged exercise (especially in the heat) [47].

Fluid and electrolyte replacement

Fluid replacement: • Sufficient fluid should be consumed during exercise to limit dehydration to <2% of body mass loss [42]. •  Athletes should not drink so much that they gain weight during exercise [42]. If body mass loss has occurred, then water should be consumed in a quantity greater than those in the losses [53]. Evidence to support sodium supplementation with exercise: • Sodium should be included in fluids during exercise when sweat losses are high (3–4 g) and/or exercise is >2 h in duration [42,54]. • All fluid and electrolyte losses should be fully replaced for optimal rehydration [39,55]. • Sodium stores be replaced for euhydration to be restored and maintained [56]. There is no evidence to support sodium supplementation in the prevention of EAH in any athlete other than for CF individuals [57].

No evidence-based practice guidelines are available for fluid and salt supplementation in the CF population. With knowledge of the physiology behind hydration in the CF individual, it would not be unreasonable to recommend electrolyte replacement for all exercising CF individuals regardless of the environmental conditions, duration, or intensity of exercise [52,58]. Further research is required to determine optimal electrolyte replacement doses and strategies.

36.2  Hydration Considerations for Exercise

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Healthy Population

(Continued)

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TABLE 36.10  Hydration Considerations for the Healthy and CF Population [39]  Cont’d CF Population

Thirst drive

Thirst is a physiological response stimulated by the rise in blood osmolality with plasma water loss [59]. Stimulation of the thirst drive occurs in the healthy population at 1–2% body mass water loss [60]. Involuntary dehydration is largely based on perceived thirst and is common after strenuous exercise when ad libitum water intake is less than the sweat output [61].

CF children have been observed to drink less during exercise. This was originally hypothesized to be a result of a reduced hyperosmotic trigger attenuating the thirst drive [51,62]. More recently, it has been shown that despite high sweat sodium concentrations, perceived thirst is unchanged during exercise for CF participants. The greater plasma volume loss associated with ­ exercise-induced dehydration is thought to act as a compensatory response triggering thirst in the absence of a strong hyperosmotic signal [58,62].

The use of sports drinks

The use of sports drinks and their role in hydration with exercise remains controversial. Composition: • 4–8% carbohydrate, 10–30 mmol/L sodium, and 3–5 mmol/L potassium [9,39]. • Designed to provide a rapid delivery of fluid and fuel during and after exercise. • Some sports drinks containing protein (2%) are marketed to be superior; however, there is limited evidence to support their use for performance enhancement or recovery. Evidence to support use: • The sodium concentration increases the thirst drive and voluntary intake of fluid (when compared with water). It is also thought to improve fluid retention postexercise by reducing urine losses. • Carbohydrate content <8% increases gastric emptying and the rapid absorption via the small intestine. • A source of fuel (in addition to fluid). • Reduced immune stress. • Voluntary rehydration improves in children with beverages that are flavored, cooled, and have a sodium content >18 mmol/L [63]. Concerns associated with use: 1. Carbohydrate replacement has not been shown to improve performance in exercise <1 h in duration. 2. Dental decay and concerns regarding regular consumption of high-sugar drinks.

Children: • CF children drink less during exercise (most likely result of the decreased hyperosmotic trigger that would in most circumstances attenuate the thirst drive) [51]. • The sodium content of fluid must be >50 mmol/L to promote voluntary rehydration in the pediatric CF population. This is above the sodium content of most sports drinks [62]. Powdered supplements can be beneficial because concentrations can be altered.

CF, cystic fibrosis; EAH, exercise-associated hyponatraemia; CFTR, cystic fibrosis transmembrane conductance regulator.

36.  DIET, FOOD, NUTRITION, AND EXERCISE IN CYSTIC FIBROSIS

F.  EXERCISE AND BEHAVIOR IN MANAGEMENT OF CYSTIC FIBROSIS

Healthy Population

331

References

FIGURE 36.3  Practical rehydration guide for patients and their families. Adapted from Gatorade ©. ŝŵĨŽƌĂ ŵŝŶŝŵƵŵŽĨ ϲ±ϴĐƵƉƐĚĂŝůLJ ;ϭ͘ϱ±Ϯ>Žƌϰϴ±ϲϰŽnjͿ

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ŌĞƌĞdžĞƌĐŝƐĞ͗ ϯϮŐƵůƉƐƉĞƌϬ͘ϱŬŐ;ϭ͘ϭůďͿůŽƐƚ;ϱϬϬŵ>ŽƌϭϳŽnjͿ ϭĐŚŝůĚŐƵůƉуϭϱŵ>;ϭͬϮŽnjͿĂŶĚϭĂĚƵůƚŐƵůƉуϯϬŵ>;ϭŽnjͿ

6. M  ake a conscious effort to hydrate before, during, and after exercise: Figure 36.3 outlines a practical rehydration guide for patients and their families. 7. Consider the environmental effect: Hot and humid environments increase the risk of dehydration. If ambient temperatures exceed body temperature and the humidity is high, then it becomes difficult for the body to dissipate heat [9]. Dehydration can still occur in cold environments, especially if sweating with insulated clothing [9].

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F.  EXERCISE AND BEHAVIOR IN MANAGEMENT OF CYSTIC FIBROSIS