Transcript continued
chapter Nutritional 9 Factors in Health and Performance Basic Nutrition Factors in Health Marie Spano, MS, RD Chapter Objectives • Know when to refer an athlete to the appropriate resource, a medical doctor, or a sport dietitian • Identify the protein, carbohydrate, and fat recommendations for athletes. (continued) Chapter Objectives (continued) • List the dietary recommendations for disease prevention and overall health • List hydration and electrolyte guidelines for different age groups and scenarios and help athletes develop an individualized hydration plan Role of Sports Nutrition Professionals • Varying degrees of nutrition knowledge • Athletes with complex nutrition issues should be referred to a team physician or sports dietitian • A sports dietitian is a registered dietitian with specific education and experience in sports nutrition • Board Certified Specialist in Sports Dietetics (CSSD) (continued) Role of Sports Nutrition Professionals (continued) • Responsibilities of the registered dietitian include the following: – Translate the latest scientific evidence into practical sports nutrition recommendations – Assess and analyze dietary practices, body composition, and energy balance of athletes – Provide personalized meal and snack plans to promote achieving short- and long-term goals for athletic performance and good health Key Point • Experienced sports dietitians help athletes make the connection between plate and performance. They have advanced knowledge, skills, and expertise in sports nutrition. Standard Nutrition Guidelines • MyPlate is a food guidance system to help consumers make better food choices. • Suggestions may need to be adjusted to accommodate those who are physically active more than for 30 minutes most days. Table 9.2 Standard Nutrition Guidelines • Dietary Reference Intakes (DRIs) – The DRI for each nutrient includes the following: • • • • Recommended Dietary Allowance (RDA) Adequate Intake (AI) Tolerable Upper Level Intake (UL) Estimated Average Requirement (EAR) Key Terms • Recommended Dietary Allowance (RDA): The average daily nutrient requirement adequate for meeting the needs of most healthy people within each life stage and sex. • Adequate Intake (AI): The average daily nutrient intake level recommended when a RDA cannot be established. (continued) Key Terms (continued) • Tolerable Upper Level Intake (UL): The maximum average daily nutrient level not associated with any adverse health effects. Intakes above the UL increase potential risk of adverse effects. • Estimated Average Requirement (EAR): The average daily nutrient intake level considered sufficient to meet the needs of half of the healthy population within each life stage and sex. Macronutrients • A macronutrient is a nutrient that is required in significant amounts in the diet. • Three important classes of macronutrients: – Protein – Carbohydrate – Fat (continued) Macronutrients (continued) • Protein – Four of the amino acids can be synthesized by the human body and are commonly called “nonessential” amino acids because they do not need to be consumed in the diet. – Nine of the amino acids are “essential” because the body cannot manufacture them and therefore they must be obtained through the diet. – Eight are considered conditionally essential. Table 9.3 Macronutrients • Protein digestibility – Calculated by how much of the protein’s nitrogen is absorbed during digestion and its ability to provide the amino acids necessary for growth, maintenance, and repair. • Protein requirements – The RDA for protein for adults is 0.8 g/kg (0.36 g/pound) of body weight for both men and women. (continued) Macronutrients (continued) • Protein requirements – The AMDR for protein in adult men and women is 10% to 35% of total calories. – Concerns about RDA for protein: • For bone health, adults may need more than the RDA. • Consistently high protein intakes may compromise carbohydrate and fat intake. Key Point • Athletes require more than the RDA for protein to build and repair muscle. Depending on the sport and the training program, 1.0 to 1.7 g per kilogram body weight of protein is recommended. Macronutrients • Carbohydrate – The primary role of carbohydrate in human physiology is to serve as an energy source. – Monosaccharides (glucose, fructose, and galactose) are single-sugar molecules. – Disaccharides (sucrose, lactose, and maltose) are composed of two simple sugar units joined together. – Polysaccharides, also known as complex carbohydrates, contain up to thousands of glucose units. (continued) Macronutrients (continued) • Carbohydrate – Glycemic index • The GI classifies a food by how high and for how long it raises blood glucose. • Foods that are digested quickly and raise blood glucose (and insulin) rapidly have a high GI. • Foods that take longer to digest and thus slowly increase blood glucose (and therefore stimulate less insulin) have a low GI. Table 9.5 Adapted, by permission, from Foster-Powell, Holt, and Brand-Miller, 2002. Macronutrients • Carbohydrate – Fiber • The DRI for fiber is 21 to 29 g/day and 30 to 38 g/day for young women and men, respectively. • This level of fiber may be excessive for some aerobic endurance athletes. (continued) Macronutrients (continued) • Carbohydrate – Carbohydrate requirements for athletes • Aerobic endurance athletes who train for long durations (90 minutes or more daily) should replenish glycogen levels by consuming maximal levels of carbohydrate, approximately 8 to 10 g/kg of body weight. • Carbohydrates provide 4 kcal/g. Key Point • Athletes adapt to dietary changes in carbohydrate intake. Though athletes who regularly consume carbohydrates will use them as a primary source of energy during aerobic exercise, consistent intake of a lowcarbohydrate diet will lead to a greater reliance on fat as a source of fuel. Macronutrients • Fat – Structure and function of lipids • Fatty acids containing no double bonds are saturated. • Fatty acids containing one double bond are monounsaturated. • Fatty acids containing two or more double bonds are polyunsaturated. • Fats provide approximately 9 kcal/g. (continued) Macronutrients (continued) • Fat – Relationship with cholesterol • High levels of total cholesterol, low-density lipoproteins (LDL), and triglycerides are associated with increased risk of heart disease. • High levels of HDLs protect against heart disease. • HDLs can be increased by exercise and weight loss. (continued) Macronutrients (continued) • Fat – It is recommended that 10% or less of calories consumed come from saturated fats (one-third of total fat intake). (continued) Macronutrients (continued) • Fat – Performance • Intramuscular and circulating fatty acids are potential energy sources during exercise. • Fat stores are large and represent a vast fuel source. • Consistent aerobic training increases the muscle’s capacity to use fatty acids as fuel. • When the intensity of exercise increases, there is a gradual shift from fat to carbohydrate as the preferred source of fuel. Key Point • The human body has a sufficient amount of fat to fuel long training sessions or competition. Vitamins • Vitamins are organic substances (i.e., containing carbon atoms) that cannot be synthesized by the body. • They are needed in very small amounts and perform specific metabolic functions. Minerals • Minerals are required for a wide variety of metabolic functions. • For athletes, minerals are important for bone health, oxygen-carrying capacity, and fluid and electrolyte balance. Minerals • Iron – Is a constituent of hemoglobin and myoglobin; plays a role in oxygen transport and utilization of energy – Iron deficiency is the most prevalent nutrition deficiency in the world – Increased risk of iron deficiency • • • • Women of childbearing age Teenage girls Pregnant women Infants and toddlers (continued) Minerals (continued) • Calcium – Athletes who consume low-calcium diets may be at risk for osteopenia and osteoporosis (deterioration of bone tissue leading to increased bone fragility and risk of fracture). Fluid and Electrolytes • Fluid balance – Water is the largest component of the body, representing from 45% to 75% of a person’s body weight. – The AI for water is 3.7 and 2.7 L/day for men and women, respectively. (continued) Fluid and Electrolytes (continued) • Preventing dehydration – Athletes should try to prevent water weight losses exceeding 2% of body weight. – Each pound lost during practice represents 16 ounces of fluid. Key Point • A very wide range of fluid losses, in the form of sweat, exists among athletes. Therefore, each athlete should develop an individualized hydration plan. Fluid and Electrolytes • Electrolytes – The major electrolytes lost in sweat are sodium chloride, and, to a lesser extent, potassium. – Hyponatremia can develop in those who exercise intensely and hydrate with only water, causing blood sodium levels to become diluted (<125 mmol/L). Key Point • Athletes who exercise intensely or for hours and hydrate excessively with only water or a no- or low-sodium beverage may dilute their blood sodium to dangerously low levels. Fluid and Electrolytes • Fluid intake guidelines – Start exercise in a hydrated state: • Prehydrate, if necessary, several hours before exercise to allow for fluid absorption and urine output. (continued) Fluid and Electrolytes (continued) • Fluid intake guidelines – Avoid dehydration during exercise: • Children: Drink 5 ounces of cold water or a flavored, salted beverage every 20 minutes. • Adolescents: Drink 9 ounces of cold water or a flavored, salted beverage every 20 minutes. • Adults: Follow an individualized hydration program. During prolonged hot weather activity, consume a sports drink with 20 to 30 mEq of sodium/L, 2 to 5 mEq of potassium/L, and 5% to 10% carbohydrate. (continued) Fluid and Electrolytes (continued) • Fluid intake guidelines – Rehydrate before the next training session: • Athletes should consume 1.5 L of water for every kilogram of body weight lost.