Nutritional Factors in Health and Performance Marie Spano, MS, RD chapter 9 Basic Nutrition Factors in Health

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, approxi- mately 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 low- carbohydrate 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 mono- unsaturated. 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.