Download Basic Nutrition Factors in Health

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9
Basic Nutrition
Factors in Health
Chapter Objectives
• Identify the protein, carbohydrate, and fat
recommendations for athletes.
• Know when to refer an athlete to the
appropriate resource, a medical doctor, or a
sport dietitian.
• 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.
Figure 10.1
Standard
Nutrition
Guidelines
www.mypyramid.gov
Key Point
• MyPyramid is an excellent starting point
from which to evaluate the adequacy of an
athlete’s diet. If a diet provides a variety of
foods from each group (grains, vegetables,
fruits, milk, meat & beans), it is likely
adequate for vitamins and minerals.
However, if the diet excludes an entire food
group, specific nutrients may be lacking.
Table 10.1
How to Evaluate the Adequacy of the Diet
• Dietary Reference Intakes (DRI)
– The DRI for each nutrient includes the following:
• Estimated average requirement (EAR)
– average daily nutrient intake level sufficient to meet the needs
of half of the healthy population within each age & sex.
• Recommended Dietary Allowance (RDA)
– average daily nutrient requirement adequate for meeting the
needs of most healthy people within each age and sex.
• Adequate intake (AI)
– average daily nutrient intake level recommended when a RDA
cannot be established.
• Tolerable upper level intake (UL)
– maximum average daily nutrient level not associated with any
adverse health effects. Intakes above the UL increase
potential risk of adverse effects.
Macronutrients
• A macronutrient is a nutrient that is
required in significant amounts in the diet.
• Three important classes of macronutrients
are
– Proteins
– Carbohydrates
– lipids
Macronutrients
• Protein
– Structure and Function of Proteins
• More than half 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.
Table 10.2
Macronutrients
• Protein Requirements
– Expressed as a percent of daily caloric intake, a common
protein intake recommendation is 10-15% for the general
adult & 15-20% for athletes.
– The RDA for protein for the general adult is 0.8 g/kg
(0.36 g/pound) of body weight for both men and women,
and 1.0-1.8 g/kg of body weight for athletes
• Protein intake for strength/power athletes: 1.5-1.8
g/kg (or rounded between 1.5 – 2.0 g/kg)
• Protein intake for endurance athletes (eg, events
lasting greater than 1.5 - 2 hrs): 1.0-1.4 g/kg (or
rounded between 1.0 – 1.5 g/kg)
– Proteins provide 4 kcal/1 g of protein
Getting Enough Protein can Also
Help Build Strong Muscles, But
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-45 mg cholesterol per serving - 15 %
daily value (%DV)
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14 Pounds of Steak:
-1625 g protein (25 g per 3-4 oz serving)
-1350 g fat (360 g saturated fat): 20 g fat
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-18,750 kcal (285 kcal per serving)
-90 mg cholesterol per serving - 30 %
daily value (%DV)
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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 1.8 g per kilogram body
weight of protein is recommended.
Macronutrients
• Protein
– Dietary Protein
• high-quality (complete) protein: contains all essential
amino acids in adequate quantities to support tissue
growth (anabolism) and maintenance. Usually of
animal origin (e.g., meat, fish, poultry, eggs, dairy
products).
• low-quality (incomplete) protein: deficient in one or
more essential amino acids (usually of plant origin,
such as grains, beans, vegetables) such that tissue
growth and maintenance is not supported.
Consuming a variety of incomplete proteins (e.g.,
vegetarian diet) provide complementary proteins,
which can result in a complete protein (e.g., combining
beans and rice).
Key Point
• Recommendations to increase or decrease
protein intake should be made on an individual basis after the normal diet has been
analyzed and caloric intake considered. A
mixed diet is the best source of high-quality
protein. Strict vegetarians must plan their
diet carefully to ensure an adequate intake
of all essential amino acids.
Macronutrients
• Carbohydrates
– The primary role of carbohydrate in human
physiology is to serve as an energy source.
– Structure and Sources of Carbohydrates
• 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.
Macronutrients
• Carbohydrates
– Dietary Carbohydrate
• All types of dietary carbohydrate—sugars as well as
starches—are effective in supplying the athlete with
glucose and glycogen.
• Consumption of a mix of sugars and starches is
desirable.
– Fiber
• The DRI for fiber is 30-38 g/day and 21-29 g/day for
young men and women, respectively (an easy
number to remember – 30 g/day).
• This level of fiber may be excessive for some aerobic
endurance athletes.
Macronutrients
• Carbohydrates
– 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 10.3 Table 10.3
Glycemic Index (GI)
of Various Foods
• The table uses white
bread (GI = 100) as a
standard.
• When variations
exist in a food item,
the mean is reported.
Adapted, by permission, from Foster-Powell, Holt, and BrandMiller, 2002.
Macronutrients
• Carbohydrates
– Carbohydrate Requirements
• The general recommendation is to consume 50 - 55%
of total daily calories as carbohydrate (many athletes
need a higher percentage, such as 60-70%, especially
during high intensity training).
• Aerobic endurance athletes who train for long durations
(90 minutes or more daily) should replenish glycogen
levels by consuming maximal levels of carbohydrate,
which is approximately 8 to 10 g/kg.
– Carbohydrates provide 4 kcal/1 g carbohydrate.
Calculation Problem
A CSCS prescribes a daily carbohydrate
intake of 10 g/kg for an 75 kg triathalon
athlete, who is currently training for the
ironman competition and has a daily caloric
intake of 4500 kcal. What percent of his daily
caloric intake is from carbohydrates?
A) 57%; B) 60%; C) 67%; D) 70%
Macronutrients
• CHO during exercise
– Unlike preexercise CHO, does not trigger
hypoglycemia
– Improved muscle permeability to glucose?
– Insulin-binding sites altered during exercise?
• CHO intake after exercise essential
– Glycogen resynthesis high <2 h after exercise
– Protein + CHO intake enhances glycogen stores
– Stimulates muscle tissue repair
Key Points
• Some aerobic endurance athletes have
maximal carbohydrate requirements, up to
10 g/kg per day. During high intensity
exercise muscle can use 2-3 g of glucose
per min.
• Most athletes do not deplete muscle
glycogen on a daily basis, and therefore
have lower carbohydrate requirements
(5-6 g/kg per day).
• Lipids
Macronutrients
– Structure and Function
• Saturated fatty acids (and trans fats), common in animal
fats, dairy products, hydrogenated shortenings, and tropical
oils (eg, palm & coconut oil), contain all the hydrogen they
can carry. These fats increase LDL “bad” cholesterol, and
increase the risk of heart disease and atherosclerosis,
especially trans fats but also saturated fats.
• Unsaturated fatty acids are missing hydrogen atoms, and
carbon atoms are joined together by double bonds. These
fats tend to lower LDL cholesterol, decreasing the risk of
heart disease.
• Mono-unsaturated fats, common in olive and canola oils,
contain one double bond.
• Poly-unsaturated fats, common in sunflower, soy, and
safflower oils, contain two or more double bond.
• Fats provide approximately 9 kcal/1 g fat.
• Fat, cholesterol, and
Table
Disease
– High levels of LDL’s and
cholesterol may contribute
to heart disease.
– High levels of HDL’s and
decreasing the ratio
between total cholesterol
and HDL’s protect against
heart disease.
– HDLs can be increased by
exercise, weight loss, and
a diet low in fats
(especially trans and
saturated fats) and
cholesterol.
10.4
Macronutrients
• Lipids
– Fat Requirements and Recommendations
• The recommendation for the general public from
health organizations such as the American Heart
Association is that fat should constitute 30% or less of
the total calories consumed.
• It is recommended that 20% of the total calories (or
two-thirds of the total fat intake) come from
monounsaturated or polyunsaturated sources and
10% from saturated fats (one-third of total fat intake).
• Cholesterol should not exceed 300 mg/day.
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.
• Cannot use fats efficiently when carbs are low ( fats
burn in the flame of carbs) given carbs are needed to
sustain proper function of neural tissue and RBC
Macronutrients
• When Should Athletes Decrease Dietary Fat?
– Need to increase carbohydrate intake to support
training type
• In this case, to ensure adequate protein provision, fat
is the nutrient of choice to decrease so that that caloric
intake can remain similar while carbohydrate is
increased.
– Need to reduce total kcal intake to achieve wt loss
• Because fat is dense in calories and is highly
palatable, decreasing dietary fat, if the diet has excess
fat, can help reduce caloric intake.
– Need to decrease elevated blood cholesterol
• Some young athletes are strongly predisposed to heart
disease, although this is uncommon.
Micronutrients
• A micronutrient is a nutrient that is required in small
amounts (typically measured in milligram or even smaller
quantities) in the diet.
• Two primary types of micronutrients are vitamins and
minerals.
• Diets deficient in vitamins and minerals may produce
decrements in physical performance.
• Taking a multi vitamin/mineral tablet may ensure that
adequate doses of vitamins and minerals are being met.
• There is no scientific data to support the use of mega doses
of vitamins and minerals in order to enhance performance
Table 10.5
(continued)
Table 10.5 (continued)
Table 10.6
• A Key Mineral for Athletes: 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).
Table 10.6 (continued)
• A Key Mineral for Athletes (especially women): Iron - a
constituent of hemoglobin & myoglobin; plays an
important role in oxygen transport & utilization of energy.
Fluid and Electrolytes
• Water
– Water is the largest component of the body,
representing from 50-70% of a person’s body weight.
– Total body water is determined largely by body
composition; muscle tissue is approximately 75%
water, whereas fat tissue is about 20% water.
– Fluid Balance
• The average fluid requirement for adults is estimated to
be 2 to 2.7 quarts (1.9-2.6 L) per day.
• Athletes sweating profusely for several hours per day
may need to consume an extra 3 to 4 gallons (11-15 L)
of fluid to replace losses.
Balance Between Water Gain and Loss
Dehydration & Exercise Performance
• Thirst
– Osmoreceptors (high blood osmolality)
– Baroreceptors (low blood volume)
– Thirst not well calibrated to hydration levels
– 24 to 48 h to completely rehydrate
• Benefits of fluids during exercise
– Minimize dehydration and water loss
– Performance and cardiovascular function
maintained
Fluid and Electrolytes
• Water
– Risks of Dehydration
• Fluid loss equal to as little as 1% of total body weight
can be associated with an elevation in core
temperature during exercise.
• Fluid loss of 2% or greater of body weight may result
in cardio-vascular strain, impaired ability to dissipate
heat, and possible a decrease in performance. At 7%
loss, collapse may occur.
• Dehydration will adversely affect endurance training
and performance to a greater extent than strength
training and performance. Strength will likely not
affected significantly until fluid loss exceeds 3-5% of
body weight.
Key Points
• Consuming adequate fluids before, during,
and after training and competition is
essential for optimal performance
• The ultimate goal is to start exercise in a
hydrated state, avoid dehydration during
exercise, and rehydrate before the next
training session.
Fluids
• Water
– Monitoring Hydration Status
• Each pound (0.45 kg) lost during practice
represents 1 pint (0.5 L) of fluid loss (16 ounces).
• Signs of dehydration include the following:
– Dark yellow, strong-smelling urine
– Decreased frequency of urination
– Rapid resting heart rate
– Prolonged muscle soreness
Electrolytes
• The major electrolytes lost in sweat are
sodium chloride, and to a lesser extent,
potassium.
• Hyponatremia can develop in those who
exercise and hydrate with only water, causing
blood sodium levels to become diluted (<125
mmol/L).
• Hyponatremia can be deadly, such as slow
marathon runners that drink water excessively
over several hours of low intensity running/walking
in a cool environment where sweating is minimal.
Key Point
• Athletes who exercise for hours (especially
in cool environments with little sweating)
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 Replacement Guidelines
– Before a Training Session
• Encourage athletes to hydrate properly before
prolonged exercise in a hot environment.
• Intake should be approximately 16-24 fluid ounces
(0.5 L) of a cool beverage 2 hours before a workout.
Fluid and Electrolytes
• Fluid Replacement Guidelines
– During a Training Session
• Provide cool beverages (about 50-70°F [10-21°C]).
• Have fluids readily available, since the thirst
mechanism does not function adequately when large
volumes of water are lost. Remind athletes to drink.
• Athletes should drink fluid frequently—for example,
4 to 8 fluid ounces (118-237 ml) every 15 minutes.
• For shorter duration exercise (< 1 hr), water is an
adequate fluid replacement, but for longer duration
exercise (> 1 hr) a carbohydrate drink is warranted
(20-30 mEq Na+ & Cl-/L; 2-5 mEq of potassium/L; and
6-8% carbohydrate)
Fluid and Electrolytes
• Fluid Replacement Guidelines
– After a Training Session
• Athletes should replenish fluids with at least 1 pint
(0.5 L) of fluid for every pound (0.45 kg) of body
weight lost.
• Weight should be regained before the next workout.
• Water is an ideal fluid replacement, although
flavored beverages may be more effective at
promoting drinking.
• The ideal fluid replacement beverage depends on
the duration and intensity of exercise, environmental
temperature, and the athlete.