NDD30503: NUTRITION FOR SPORTS AND EXERCISE

NUTRITION FOR SPORT
AND EXERCISE
NDD30503
ASSOC PROF. DR. SHARIFAH WAJIHAH WAFA BTE SST WAFA
EC22
SUNDAY
1100-1300

Learning Objectives
1. Classify minerals and describe their general
roles.
2. Explain how mineral inadequacies and
excesses can occur and why each might be
detrimental to performance and health.
3. Describe the factors that increase, maintain,
and decrease bone mineral density,
including a discussion of the minerals
associated with bone formation and their
effects on performance and health.

Learning Objectives
4. Describe the role of iron in red blood cell
formation and the impact of low iron intake
on performance and health.
5. Describe the roles of minerals in the immune
system.
6. Compare and contrast minerals based on their
source—naturally occurring in food, added to
foods during processing, and found in
supplements—including safety and
effectiveness..

Introduction
 Minerals differ from vitamins in
many ways
 Inorganic, not well absorbed, not
easily excreted

Classification of minerals
 There are 21 essential minerals.
 A RNI and UL have been established for
most minerals.
 Moderate to rigorous exercise may
increase the loss of some minerals,
which typically can be replaced with
properly chosen foods.

 Amount found in the body
1. Macrominerals
a. Found in relatively large amounts
b. Calcium, phosphorous, magnesium
c. Sodium, potassium, chloride, sulfur
2. Microminerals (trace minerals)
a. Iron, zinc, copper, selenium
b. Others such as manganese and
molybdenum

 Functionality
1. Proper bone formation
a. Calcium, phosphorus, magnesium,
fluoride
2. Electrolytes
a. Sodium, potassium, chloride
3. Enzyme-related functions
a. Iron, zinc, selenium, copper

 Moderate to rigorous exercise
increases the loss of some minerals
1. Mineral loss in sweat and urine may
be greater in athletes
2. Adaptation to conserve some
minerals as athletes acclimate to heat

 Moderate to rigorous exercise increases
the loss of some minerals
3. Small to moderate losses can be offset by
dietary intake
4. Larger losses may need supplementation
5. Zinc moves from muscle cells into the
ECF and might be excreted in urine

 Poor food choices by athletes and sedentary
people often lead to low mineral intake:
1. Athletes likely low in dietary calcium, iron,
zinc, selenium, magnesium, copper
2. Energy-restricted athletes at the most risk
3. Nutrient-dense foods are important to meet
overall needs
4. The best approach for determining mineral
intake is personalised dietary assessment for
each athlete

Mineral deficiencies and toxicities
 Mineral homeostasis
1. Generally maintained by adjusting
absorption and excretion
a. If storage is high, absorption decreases
b. If storage is low, absorption increases
2. Hormonal and other mechanisms are also
influential

1. Factors that increase mineral absorption
Presence of a growth state
Presence of a deficiency state
Larger (vs. smaller) amounts consumed in food
Presence of food in the GI tract
Certain compounds in food (e.g., vitamin C, soluble fiber,
MFP factor)
Certain chemical forms

2. Factors that decrease mineral absorption
Increasing age
Poor health or GI disease
Presence of competing minerals
Certain compounds found in food (e.g., phytic acid, insoluble fiber)
Excessive supplementation of individual minerals
Presence of food in the GI tract
pH of the GI tract
GI transit time

 It is important to guard against mineral
deficiencies
1. General characteristics
a. Deficiencies develop over time
b. No signs or symptoms initially
c. Signs or symptoms are non-specific when they
first occur
d. Specific symptoms associated with severe
deficiencies

 It is important to guard against mineral
deficiencies
2. Prevalence of subclinical mineral deficiencies
a. Iron deficiency without anemia
i. Prevalence may be higher in female
endurance athletes and vegetarians
ii. Effect on performance not known but it is
prudent to avoid this condition
b. Osteopenia
i. Low bone mineral density
ii. May be as high as 11-22% of athletes

c. It is reasonable to assume some athletes could
have subclinical deficiencies of iron, calcium,
zinc, selenium, and magnesium
d. Subclinical deficiencies of other minerals not well
documented

3. Prevalence of clinical mineral deficiencies
a. Iron-deficiency anemia
i. Prevalence in female athletes estimated to be 3% or
more
ii. Prevalence in male athletes very low but not zero
iii. Results in fatigue and impaired performance

b. Osteoporosis
i. Bone loss exacerbated
with low estrogen
(associated with
inadequate dietary
intake, low caloric intake,
and low body fat)
ii. 10-13% female distance
runners
iii. Small % of amenorrheic
female distance runners
< age 30
c. Clinical deficiencies
negatively affect
performance and health

 Bone-forming minerals
1. 90% is calcium and phosphorus, used to form
hydroxyapatite
2. Small amount of fluoride
3. Several minerals have indirect roles
4. Vitamin D is critical to bone development
The roles of minerals in bone formation

 Bones have both structural and metabolic
functions
1. Bone growth, modeling, and remodeling
Increased length and thickness during childhood and adolescence
Growth is longitudinal (length) and radial (thickness)
Modeling is the process in which bones are formed and shaped
Mechanical stress strengthens bones
Increased mineral content until approximately age 35
Slow mineral loss after approximately age 35
Accelerated mineral loss in females when estrogen production declines

2. Bone remodeling
a. Bone turnover is constant
b. Site of bone remodeling
i. Cortical bone
• approximately 80% of skeleton
• Shafts of the long bones and on the surface

ii. Trabecular bone
• approximately 20% of skeleton
• Ends of the long bones and under the surface
• Honeycomb-like structure
• Greater surface volume, metabolic activity, and turnover

c. Rate and time of bone remodeling
i. Rate
• 1-2% of entire skeleton but approximately 20% of
trabecular bone
• approximately 1 million active sites each day
ii. Length of time
• In children, weeks
• In young adults, approximately 3 months
• In older adults, approximately 6 to 18 months
• Over a ten-year timeframe an adult’s skeleton will
be completely remodeled

d. Osteoclasts resorb bone
i. Stimulated by physical activity and
microfractures
ii. Stimulated by hormones—PTH and calcitriol
e. Osteoclast/osteoblast balance
i. In children and adolescents, deposition is
favored
ii. In young adults, balance generally exists
iii. In middle-aged to older adults, resorption is
favored (more osteoclastic activity)

 Achieving peak bone mineral density is critical to
long-term health
1. Highest lifetime bone mineral density
a. Trabecular bone by approximately age 30
b. Cortical bone by approximately age 35
2. Approximately 60% is genetically determined
3. Important influences
a. Adequate calcium, vitamin D, and protein intakes
b. Weight-bearing exercise or activity or high-
impact exercise (jumping, strength training)
c. Hormones

4. Nutritional factors affecting peak bone density
a. Calcium
i. Greatest amount needed for ages 9 to 18
(1,300 mg/day)
ii. Substantial need throughout adulthood
(1,000 to 1,200 mg/day)
b. Vitamin D
i. 5 mcg/day until age 50
ii. Need increases with age
• 10 mcg ages 51 to 69; 15 mcg age 70 and above
• Conversion to active form declines
• Exposure to UV light declines

c. Protein
i. Adequate protein in children is associated
with bone growth
ii. Necessary for secretion of IGF-1
5. Mechanical factors affecting peak bone density
a. Weight-bearing exercise
b. High-impact activities
c. Excess body weight

5. Bone loss associated with aging
In women, 0.25 to 1.0% yearly until age 50
With estrogen deficiency, 1-2% yearly (mainly from vertebrae)
In the decade after menopause, 20-30% of bone density from trabecular bone
and 5-10% from cortical bone
In older men, approximately 1% yearly
Bone loss associated with low calcium availability for functional use and to
maintain calcium homeostasis
Under hormonal regulation
Normal calcium excretion is approximately300 mg between GI secretions and
urine losses

6. Calcium may be taken
from bone to maintain
calcium homeostasis
a. Hormonally controlled
i. Parathyroid hormone
(PTH)
ii. Calcitriol (form of vitamin
D)

b. Calcium homeostasis
i. Regulation of calcium in
the blood and extracellular
fluid
ii. Primarily controlled by PTH
iii. Critical for proper nerve
and muscle function
iv. Fast calcium exchange
• PTH activates calcium
pumps in membranes
surrounding bone fluid
• Calcium is mobilized
from bone fluid not
mineralized bone
• PTH stimulates calcium
resorption in kidney and
increased GI absorption

3. Calcium balance
a. Total absorption, distribution, and excretion
b. Different from calcium homeostasis but related
c. Increased or decreased absorption and excretion
as needed
d. Bone turnover is balanced under normal
conditions

4. Long-term low calcium intake
a. Bone turnover is not balanced
b. Slow calcium exchange
i. PTH stimulates dissolution of bone
ii. Increases osteoclastic activity; decreases
osteoblastic activity
iii. Calcium (and phosphate) released from bone
iv. Over time, integrity of bone is decreased

 Bone loss is associated with lack of estrogen
Powerful influence on osteoclast number and activity
Generally associated with menopause
Also present in some young female athletes
Distance runners, ballerinas, and gymnasts are at greater risk
Focus on research: Does the Disruption of the Menstrual Cycle That
Occurs in Some Athletes Have Health Implications?

 The roles of calcium and exercise in preventing
or reducing bone loss associated with aging
have not been fully established
1. Diet-related
a. In women after age 70, calcium supplementation
is beneficial
b. Calcium supplementation after age 35 may be
prudent to slow calcium losses from bones
c. Calcium supplementation in this group will not
offset all of the factors that affect a decline in
BMD

d. In women under 50 and most men, adequate
calcium and vitamin D intakes slow the loss of
bone calcium
e. In the first 10 years after menopause, calcium
supplementation has a small, positive effect
2. Exercise-related
a. High-intensity weight-bearing activities
b. Resistance training
c. Mechanical stress increases bone density
d. Other types of exercise are beneficial but do not
slow bone loss

 There are numerous strategies for increasing
dietary calcium consumption
1. Calcium sources
a. Milk and milk products
b. Reduced-lactose or lactase-treated milk products
c. Fermented milk products
d. Calcium-containing vegetables such as cabbage,
broccoli, and green leafy vegetables
e. Calcium-fortified foods
f. Calcium supplements

2. Many people consume an inadequate amount
of calcium daily
3. Over-consumption of calcium supplements (UL
2500 mg/day) can lead to kidney stones and
displacement of other nutrients
 Phosphorus, fluoride, and magnesium are also
involved with bone health
1. Phosphorus is abundant in food
2. Fluoride is added to supplements or water
3. Magnesium is found in vegetables, nuts, beans,
and legumes

The roles of minerals in blood formation
 Iron is an integral part of hemoglobin
1. Hemoglobin
a. Iron-containing protein
b. Necessary for oxygen, carbon dioxide, and nitric
oxide transport
c. Normal: 12.1 to 15.1 g/dl in females; 13.8 to 17.2
g/dl in males
2. Hematocrit
a. Measure of oxygen-carrying capacity
b. Expressed as % of total blood plasma volume
c. Normal: approximately 42% in females;
approximately 45% in males

3. Iron deficiency anemia
a. Most common nutrition-related anemia
b. Low iron stores may be due to:
i. Poor intake
ii. Poor absorption
iii. Excessive blood loss

 Blood tests can help detect iron deficiency
1. Common measures are hemoglobin, hematocrit,
and ferritin
2. Iron status declines over time
a. As iron stores are being depleted, hemoglobin
and hematocrit do not decline initially
b. Serum ferritin concentration declines
3. False (runner’s) anemia

 Iron-deficiency anemia negatively affects
performance
1. Iron-deficiency anemia impairs performance
a. VO2max (aerobic capacity) declines
b. Endurance capacity declines
c. A decrease in iron-containing compounds
decreases oxygen utilization
2. Effect of iron deficiency without anemia on
performance is unclear

 The prevalence of iron deficiency and iron-deficiency
anemia in female athletes is likely higher than in the
general population
Unlikely in most males (<2% in males under 70 years old)
Infrequently seen in adolescent males or male endurance
athletes (5%)
Some medications induce bleeding and loss of iron
Greatest risk is for menstruating females
Athletes with low caloric intake are at greater risk
Sweat loss
Iron loss in feces and urine in times of intensive training

 Athletes should consume a variety of iron-
containing foods
1. Adequate energy intake
2. Variety of iron-dense foods
3. Heme (animal) sources are better absorbed than
nonheme (plant) sources
4. Vitamin C increases iron absorption

The roles of minerals in the immune
system
 The immune system protects the body from
disease
1. Immunity
a. Non-specific immunity (skin, respiratory system,
and GI tract)
b. Specific antibodies
c. Cytokines regulate the immune system

system
2. Zinc
a. Widely found in cellular enzymes
b. Involved in various immune functions
c. Most endurance athletes (approximately90%) do
not meet the RNI
d. Overtraining and zinc deficiency can result in
repeated URTI
e. Supplementation (low dose) is appropriate when
RNI isn’t met through the diet
f. supplemental zinc can interfere with iron and
copper absorption and decrease lymphocyte
response

system
3. Selenium
a. Involved in cellular and immune system function
b. Found in meat, fish, poultry, whole grains, and
nuts
c. Depressed immunity is associated with
deficiency
4. Iron
a. Plays important role in immune system functions
b. Excess iron impairs immune function

The adequate intake of all minerals
 The key to obtaining all the minerals needed
from food is to consume a nutrient-dense,
whole-foods diet
A varied, nutrient-
dense diet can
provide adequate
amounts of minerals
High-sugar/high-fat
diets often do not
meet daily mineral
requirements
Consume an
adequate amount of
calcium and iron
from food

 The dose and potency of a mineral supplement
can vary substantially from brand to brand
1. Mineral-fortified foods
a. Some foods have many minerals added
b. Degree of absorption is unknown
2. Multimineral supplements
a. Dosages may exceed the RNI or UL for some
nutrients
b. Degree of absorption is not known

3. Supplementing with individual minerals
a. Calcium and iron are most common
b. Should be physician prescribed, not self
prescribed
c. Likely to affect absorption of other minerals
d. High bioavailability may not be desirable

4. Spotlight on supplements:
How Beneficial is Chromium
Supplementation for
Athletes?
a. Some may contain highly
absorbable form
b. Enhances insulin sensitivity
c. Effectiveness for increasing
muscle mass and decreasing
body fat unclear

 4 minerals critical for bone formation:
 3 major electrolytes:
 3 trace elements that may be lost in sweat or
urine:
 4 food components that inhibit mineral
absorption:
 2 types of cells involved in skeletal growth:
 2 hormones that regulate calcium balance:
 3 serum values used to evaluate iron status:
 3 rich food sources of copper:

NDD30503: NUTRITION FOR SPORTS AND EXERCISE

NDD30503: NUTRITION FOR SPORTS AND EXERCISE

NDD30503: NUTRITION FOR SPORTS AND EXERCISE

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