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Chapter 8
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Minerals: The Inorganic Regulators
• Introduction
– More than 20 known essential minerals
– Classified as micronutrients
– Deficiencies
• May occur with some minerals
• Females and children at risk
– Supplementation
• Some groups of individuals may benefit
Basic Facts
What are minerals,
and what is their importance to humans?
• Minerals are elements found in nature
• In human nutrition, minerals are essential to life
Functions of minerals in humans
 Building blocks for body tissues
– Bones, teeth, organic compounds
 Metabolic regulation
– Metalloenzymes
– Electrolytes
 Not used as an energy source
Minerals: Roles in Human Nutrition and Sports
Performance
• Components of metalloenzymes and various compounds,
serve as metabolic activators, and form bone structure.
• Physiological roles
–
–
–
–
–
–
–
–
–
Muscle contraction
Oxygen transport
Oxidative phosphorylation
Enzyme activation
Immune functions
Antioxidant activity
Acid base balance
Water balance
Bone density
What minerals are essential in
human nutrition?
In general, how do deficiencies or excesses of minerals
influence health or physical performance?
• Preliminary stage
– Mineral bioavailability
• Low energy intake
• Biochemical deficiency stage
– Decrease body pool of a mineral
• Detected by various blood tests
• Physiologic deficiency stage
– Appearance of unspecified
symptoms
• Loss of appetite, weakness, fatigue
• Clinically manifest deficiency
– Clinical symptoms occur
• Anemia
Mineral nutrition
• Some concern with inadequate intake
– Calcium, iron, zinc
• Athletes
– Most, especially males, obtain adequate amounts
– Weight-control sports at risk
• Body may compensate for decreased dietary intake
– Increased absorption
– Decreased excretion
• Toxic minerals
– Mercury, lead
Essential Minerals
• Macrominerals
–
–
–
–
–
–
Calcium
Phosphorus
Magnesium
Sodium
Chloride
Potassium
• Trace minerals
–
–
–
–
–
–
–
–
–
Iron
Zinc
Copper
Chromium
Selenium
Vanadium
Boron
Fluoride
Iodine
Mineral Supplements:
Lausanne Consensus Conference
Of the minerals and trace elements
essential for health, particular attention
should be paid to iron and calcium status
in those individuals (athletes) who may
be at risk.
Calcium
• Symbol: Ca
• Dietary Reference Intakes (DRI):
–
–
–
–
–
AI = 1,000 mg (age 19-50)
AI = 1,300 mg (age 9-18)
AI = 1,200 (age 50+)
UL = 2,500 mg
DV = 1,000 mg
Mineral Format
•
•
•
•
•
Name; terms
DRI
Food sources
Major functions
Deficiency
– Health
– Performance
• Supplementation
– Health
– Performance
• Prudent recommendations
Calcium
• Good food sources:
– Dairy products (milk, yogurt); fish (sardines, salmon)
– Dark green leafy vegetables; legumes; fortified foods
• Absorbability
– Lactose and vitamin D in milk may facilitate absorption
– Phytates in legumes and oxalates in spinach may diminish
absorption somewhat
Food Labels - Minerals
• Calcium and iron listed
– % of Daily Value
• Other minerals may be
listed
Calcium: Food sources
Food
Calcium (mg)
Calories
Skim milk (8 oz)
306
90
Yogurt, low-fat, fruit (8 oz)
345
232
Swiss cheese (1.5 oz)
336
162
Salmon, canned (3 oz)
181
118
Sardines, canned (3 oz)
325
177
Spinach, cooked (0.5 cup)
146
30
Collards, cooked (0.5 cup)
178
31
Beans, navy (0.5 cup)
61
148
Soy milk, fortified (8 oz)
368
98
Orange juice, fortified (8 oz)
300-350
110
Cereal, breakfast, fortified (1 oz)
256-1,053
88-106
Calcium
• Major functions in humans:
– 99% Bone and teeth formation;
– 1% Enzyme activation
• muscle contraction;
• nerve impulse transmission
• cell membrane potential
Figure 8.1
Calcium
• Deficiency - Effects on health:
–
–
–
–
–
–
75% of women do not consume AI
50% of women consume < ½ AI
Losses in intense exercise: sweat and kidney losses
Increased risk for colon cancer?
Increased risk of high blood pressure?
Osteoporosis
• The major health problem of calcium deficiency
Osteoporosis
• Thinning and weakening of the bones related to loss
of calcium stores
• Various risk factors for osteoporosis
Figure 8.3
Figure 8.2
Osteoporosis
• Each year osteoporosis causes 1.5 million fractures
• More common in women, but 2 million American
men are at risk
– 80,000 men suffer a hip fracture each year
• Prevention is the key
Calcium
• Deficiency: Effects on physical performance:
– Low serum calcium levels are rare
• May impair muscle contraction
• May cause muscle cramps
– Low bone calcium may lead to fractures
Calcium
• Supplementation: Effects on health
–
–
–
–
Cancer
High blood pressure
Weight loss
Bone health
Calcium and cancer
• Most research has focused on colorectal cancer
• Research findings are equivocal
– Several epidemiological studies show reduced risk of
colorectal cancer with increased intake of calcium and
vitamin D
– Results of a 7-year experimental study has not shown any
beneficial effects of calcium and vitamin D, but the study is
ongoing
Calcium and cancer
• Recent American Institute of Cancer Research report
– Based on its worldwide review, the AICR concludes the
evidence is generally consistent, mechanism plausible, and
calcium probably protects against colorectal cancers
Calcium and high blood pressure
• Several studies have shown small reductions in blood
pressure with calcium supplementation
• Overall, major reviews conclude that the evidence
supporting a beneficial effect of calcium
supplementation in hypertensive individuals is weak
Calcium and weight loss
• Theory
– Low calcium levels stimulate an increase in calcitriol
(vitamin D hormone) which can cause an influx of calcium
into adipose cells, stimulating fat accumulation
• Research findings
– Studies from one laboratory has shown positive effects of
dairy products on weight loss
– Recent meta-analysis of 13 studies reports no benefits of
calcium supplementation on weight loss
• FTC halted advertising associating dairy products
with weight loss
Calcium and bone health
•
•
•
•
Calcium supplements
Exercise
Hormone replacement or nonhormonal drug therapy
Osteoporosis in sports
– The Female Athlete Triad
Calcium supplements
• Supplements come in different forms and amounts
–
–
–
–
200 mg in one-a-day; 200- 600 mg in calcium supplements
Carbonate, citrate
Little difference between forms
Chewable forms for people over age 50
• Advice for those who take calcium supplements
– 200 mg with meals three times a day
– May reduce the absorption of oxalates, which when
combined with calcium in the body may form kidney
stones
– Avoid exceeding the UL with supplements and fortified
foods ; no need to exceed 1.5 grams
Calcium supplementation
• Prevention of bone fractures
– Recent review and a meta-analysis of 29 studies indicate
calcium, either alone or in combination with vitamin D,
reduces risk of fractures of all types in the elderly
– NIH State-of-the-Science report indicate that calcium and
vitamin D supplements could protect and even improve
bone density in the elderly to help prevent bone fractures
Exercise and bone health
• Mechanical loading will add bone
– Dynamic exercise
– College-age females increased hip and spine bone mass
• 10 maximal vertical jumps 3 days a week for 6 months
• Engaging in physical activity during youth is more
osteogenic than during adulthood
– Adequate dietary calcium is an important factor
Exercise and bone health
• Whether or not exercise prevents bone loss after
menopause appears to be debatable
– Some contend resistance and weight-bearing
exercise will prevent bone loss and may add bone
– Others contend that there is little evidence that exercise,
even vigorous exercise, attenuates the menopause-related
loss of bone mineral in women
– Adequate calcium may be the key
Exercise and bone health
• ACSM Position stand on Exercise and osteoporosis
– Dynamic exercises, such as resistance training and highimpact weight-bearing aerobic exercise are effective
means to stimulate bone development
– Development of peak bone mass through exercise is best
achieved during the developmental years of youth
– Exercise may increase bone mass slightly in adulthood, but
the primary benefit of exercise at this time of life is to help
prevent bone loss associated with physical inactivity
Exercise and bone health
• ACSM Position stand on Exercise and osteoporosis
– The optimal program for older women would include
moderate- to high-impact activities to improve strength,
flexibility, and coordination that may help increase
postural stability and decrease the incidence of
osteoporotic fractures by lessening the likelihood of falling
– Exercise may stimulate bone development, but optimal
calcium intake approximating 1,000 milligrams or more
daily appears to be equally important
– Diet and exercise are the recommended therapy, but
pharmacologic therapy may be recommended for some
postmenopausal women even though they are physically
active
Hormone replacement or
nonhormonal drug therapy
• Given health risks associated with hormone
replacement, the FDA recommends postmenopausal
women consult with their healthcare provider
– A decrease in breast cancer incidence has been noted
following the drop in hormone replacement therapy
• Nonhormonal drug therapy
– Bisphosphonates (Fosamax, Boniva, Reclast)
– Raloxifene (Evista)
– Calcitonin
Osteoporosis in sports
• The Female Athlete Triad
– Disordered eating
• Creates an energy deficit
• Interferes with the hypothalamic-pituitary-gonadal axis
and hormone secretion
– Amenorrhea
– Osteoporosis
• Males are at less risk, but osteoporosis may
occur with poor diets and weight loss
Disordered Eating
• Female athletes, particularly those involved in endurance and
weight-control sports, may be susceptible to the female
athlete triad, with one of the end results being premature
osteoporosis
• Disordered eating
– Energy intake less than energy expenditure
– Decrease body fat levels
– Reduced production of estrogen
Main
problem
with low
Ca+
intake 
stress
fractures
Female
Athlete
Triad
Image from
http://nsca.hkeducationcenter.com/courses/OEC_Previews/hfft303_preview/images/fig_04.gif
Calcium
• Supplementation: Effect on physical performance
• Research is almost nonexistent
• One study with acute supplementation:
– 500 mg high-calcium or 80-mg low-calcium drink 60
minutes before 90-minute run followed by 10-kilometer
time trial
– No effect on energy metabolism
• May be beneficial to help maintain bone mass in
some female and male athletes
Calcium
Prudent Recommendations
• Start at a young age
– Dynamic exercise
– Calcium-rich diet
• Low-fat dairy products
• Inexpensive, high-calcium, high-protein, high-nutrient
density
• Postmenopausal women and older men
– Calcium and vitamin D supplements may be recommended
• Obtain a bone density test if at risk
Phosphorus
• Symbol: P
• Dietary reference intakes (DRI):
– RDA = 700 mg (age > 19); 1,250 mg (age 9-18)
– DV = 1,000 mg
– UL = 4,000 mg
Phosphorus
• Good food sources:
– Distributed widely in foods; seafood, meats, legumes, grain
products, vegetables
– Phosphorus is a common food additive
– Most Americans consume more than the RDA for
phosphorus
• Major functions in humans as phosphates:
– 80-90% in bones as calcium phosphate
– Organic roles: ATP, PCr, thiamin PP, 2,3-DPG
Phosphorus
• Deficiency: Effect on Health
– Deficiency states are rare: bone loss could occur in such
cases
• Deficiency – Effect on physical performance:
– Not studied; could induce muscular weakness
Phosphorus
• Supplementation: Effect on health:
– Beneficial: Not studied, but could improve bone health if
deficiency corrected
– Detrimental: Excess phosphates could impair calcium
balance over time
Phosphate Salts:
Possible Metabolic Roles In Sport Performance
• B vitamin cofactor
• Intracellular regulation
• High energy phosphagens (ATP, PCr)
• Acid-base balance
• Enhanced cardiovascular efficiency
• 2-3-DPG synthesis (2,3-BPG)
- Incorporated into hemoglobin
- Increased release of oxygen to muscle tissue
Phosphate Salts: Common Types
• Sodium phosphate
• Calcium phosphate
• Potassium phosphate
Phosphate Salt Supplementation
Early Research
Early research emanating from Germany in the 1920s
suggested phosphate salts possess ergogenic potential,
but methodological approaches were inadequate.
In 1939, Boje criticized the early research, but did note that
phosphates could increase physical performance if
consumed in quantities greater than found in the normal
diet.
Phosphate Salt Supplementation: Modern
Research
• Four well designed studies (1984-1992)
• Supplementation protocol involved 3,600 to 4,000
mg sodium phosphate for 3-5 days
• General results
–
–
–
–
–
Increased red blood cell 2,3 DPG
Increased VO2max 6-10 %
Increased treadmill run time to exhaustion
Increased cycle ergometer time to exhaustion
Improved 40K cycle ergometer time trial performance
Phosphate Salt Supplementation
“I wouldn’t say that sodium phosphate
represents a breakthrough. It won’t
make up for lack of training. But it
does produce an effect. It does allow
better performance.”
Robert Cade, MD. Quoted in Runner’s World, 1986.
Phosphate Salt Supplementation: Modern
Research
• Other studies conducted during this time frame revealed no
performance enhancement with phosphate salt
supplementation
• One reviewer noted that there were numerous
inconsistencies in research design among studies
–
–
–
–
Mode of exercise
Dietary intake not controlled
Type of supplement
Length of loading period and washout period
• More research is needed with sodium phosphate salt
supplementation to evaluate its ergogenic potential
Phosphorus
• Prudent recommendations
– Excess phosphate intake could lead to gastrointestinal
distress
– Long-term intake could lead to calcium imbalances
• For use as an ergogenic aid
– Practice in training ; 3-4 days supplementation
– Do not use long term
Magnesium
• Symbol: Mg
• Dietary Reference Intakes (DRI):
– RDA = 400-420 mg for males; 310-320 mg for females
– UL = 350 mg, but only pharmacological forms of
magnesium. No restrictions from food sources
– DV = 400 mg
Magnesium
• Good food sources:
– Widely distributed in foods: seafood, nuts, legumes,
whole-grain products
• Major functions in humans:
– 50-60 % stored in skeletal system; component of over 300
enzymes
– About 1% in the blood, rest in soft tissues such as muscle
– Part of ATPase; involved in cardiovascular and
neuromuscular functions; protein synthesis; 2,3-DPG
Magnesium
• Deficiency: Effect on health:
• Although 3 of 4 Americans do not obtain the RDA for
magnesium, deficiency is rare
• Symptoms could include apathy, muscle weakness;
muscle cramps; high blood pressure; heart rate
arrhythmias; deficiency may be a cardiovascular risk
factor
Magnesium
• Deficiency: Effects on physical performance:
– Many athletes, especially in weight-control sports, do not
obtain the RDA for magnesium
– Serum Mg levels decrease during exercise
– Some Mg may be lost in sweat and urine
• Deficiency theorized to
– Impair endurance performance
– Depress immune function and contribute to the chronic
fatigue syndrome, or overtraining
– However, there are few data to support these theories.
Magnesium
• Supplementation: Effect on health:
– Mg may help reduce blood pressure as part of a healthful
diet, such as the DASH diet, but comprehensive reviews
reveal a weak relationship between use of Mg
supplements and reduced blood pressure in wellnourished individuals
– Probably only helps if a deficiency is corrected
Magnesium
• Supplementation: Effect on exercise performance
– Most research suggests supplementation does not
enhance performance
– Recent meta-analysis revealed no ergogenic effect on
• Aerobic performance
• Anaerobic performance
• Strength performance
– May benefit an athlete if a deficiency is corrected
Magnesium
• Prudent recommendations
• Obtain adequate Mg through a balanced diet
• Obtaining magnesium from fortified foods or
supplements may be recommended for athletes,
particularly females, in weight-control sports
– Caveat: Do not exceed 350 milligrams/day
Trace Minerals
• Trace minerals are those for which quantities of 100
mg or less are needed daily
• Also known as microminerals
• The term utltratrace minerals is used for those
whose requirements are expressed in micrograms
(mcg or μg)
Iron
• Symbol: Fe
• Dietary Reference Intakes (DRI):
– RDA
•
•
•
•
•
8 mg men and postmenopausal women
11 mg males (age 14-18)
15 mg females (age 14-18)
18 mg females (age 19-50)
27 mg (Pregnancy)
– UL = 40-45 mg
– DV = 18 mg
Iron
• Good food sources:
– Heme iron: meat (beef), liver, dark chicken, oysters, clams,
fish (MPF factor)
• Greater bioavailability
– Nonheme iron: dried fruits, vegetables, legumes, wholegrain products
• 100% in plant foods
• 20-70% in animal foods
– Vitamin C helps absorb nonheme iron
– Adding meat to plant foods ↑ nonheme iron absorption
– Various factors (tannins, phytic acid, oxalic acid, calcium)
impair nonheme iron absorption
Food Labels - Minerals
• Calcium and iron listed
– % of Daily Value
• Other minerals may be
listed
Iron
• Major functions in humans
– Formation of hemoglobin, myoglobin, oxidative enzymes
– Iron stored in the body as ferritins
Figure 8.4
Iron
• Deficiency: Effect on health and physical performance
– Iron-deficiency anemia
– A leading worldwide risk factor for disability and death
• Estimated 2 billion people, mostly in developing countries
– Iron-deficiency anemia would impair aerobic endurance
– Food contains about 6 mg iron/1,000 Calories
– Main factor in Western world is inadequate dietary intake
• 3-5% of females in the United States and Canada
Deficiency stages
• Iron deficiency without anemia
– Depletion of bone marrow stores
– Decrease in serum ferritin and other markers of iron
storage
– Iron-deficiency erythropoiesis
– Hemoglobin still normal
• Iron-deficiency anemia
– Hemoglobin levels < 13 g (males) or 11 g (females)
Deficiency in athletes
• Studies and reviews are inconsistent, but generally
suggest female athletes, and some adolescent male
athletes, may be at risk
• One recommendation is to screen female athletes
twice a year for hemoglobin and hematocrit; tests of
iron status may also be recommended
Iron Status In Athletes
The prevalence of iron deficiency anemia is likely to be
higher in athletic populations and groups, especially in
younger female athletes than in healthy sedentary
individuals.
Cause of iron deficiency in athletes
• Inadequate dietary iron
– Vegetarian diets
• Iron loss in urine (hematuria)
– Foot contact in runners (hemolysis)
– Hand pressure in rowers
• Iron loss in feces
– Gastrointestinal bleeding
– Use of aspirin or NSAIDS
• Iron loss in sweat
• Athletes who train at altitude
Sports anemia
• Sports anemia is not a true anemia
• May occur during the early stages aerobic endurance
training
• Plasma volume expands, diluting RBC concentration
• Increased plasma volume is beneficial and helps
maintain optimal oxygen delivery
Iron deficiency without anemia
• Effects on physical performance are debatable
• Some scientists conclude iron deficiency without
anemia impairs muscle function and limits exercise
capacity
• Others indicate it is possible to maintain VO2max and
exercise capacity
Iron
• Supplementation: Effect on health
– Beneficial: Treat iron deficiency anemia
– Detrimental when taken in excess
• Hemochromatosis in susceptible individuals
• May decrease absorption of copper and zinc
• May be fatal to young children
– Neutral: No beneficial or adverse effects on CHD
Iron
•
Supplementation: Effect on physical performance
– Iron deficiency anemia – Supplementation will enhance
performance
– Iron deficiency without anemia – Research equivocal
• May improve iron status, but not likely to improve performance
– Iron saturated – No ergogenic effect
Iron Supplementation:
Training And Altitude
• Training and altitude stimulate erythropoiesis
• Increased hemoglobin may necessitate increased iron stores,
especially in females
• Check hemoglobin and iron responses in athletes during
altitude training
Live High, Train Low
• Live High - Reside in special low atmospheric
pressure home to simulate living high that will
increase production of natural erythropoietin and
increased production of red blood cells (RBC)
• Train low – Training at altitude may decrease training
intensity
• Technique used by elite endurance athletes, such as
Khalid Khannouchi, Paula Radcliffe, and Lance
Armstrong
• May need additional dietary iron for hemoglobin
saturation
Iron
• Prudent recommendations:
– Female and adolescent athletes focus on dietary iron
intake
– Iron supplements may be recommended for some athletes
• Typical One-a-Day contains 18 mg
• Injections may be advisable for some athletes
• Do not take iron supplements indiscriminately
– Adult males should avoid excessive intake
• May select One-a-Day without iron
Copper
• Symbol: Cu
• Dietary Reference Intakes (DRI):
– RDA = 900 mcg (0.9 mg) for adults (age 19-50)
– UL = 10 mg
– DV = 2 mg
Copper
• Good food sources:
– Meat, seafood, nuts, beans, whole-grain products
– Found in drinking water
• Major functions in humans:
– Functions as a metalloenzyme and works closely with iron
in oxygen metabolism
– Formation of hemoglobin; cytochromes; superoxide
dismutase
Copper
• Deficiency: Effects on health:
– Rare; anemia in malnourished individuals
• Deficiency: Effects on sport performance:
– Rare; no research indicates athletes are copper deficient
Copper
• Supplementation: Effects on health:
– No beneficial effects
– Excess, even 5-10 mg daily may be toxic
• Supplementation; Effects on sport:
– No research available
• Prudent recommendations:
– Consume foods rich in iron (key nutrient)
– Supplementation not recommended
Zinc
• Symbol: Zn
• Dietary Reference Intakes (DRI):
– RDA = 11 mg adult males and 8 mg adult females
– UL = 40 mg
– DV = 15 mg
Zinc
• Good food sources:
– Animal foods such as meat, seafood, oysters, milk, fortified
cereals
– 3 ounces of meat contain 30-50% of the RDA
– Phytates and fiber may ↓ bioavailability
• Major functions in humans:
– Involved in over 300 enzymes; protein synthesis; LDH
– Wound healing; immune functions; bone formation
Zinc
• Deficiency: Effects on health:
– May occur in populations that consume little meat
– One study with children reported impaired immune
systems, failure to grow properly
Zinc
• Deficiency: Effects on exercise performance:
– May occur in weight-control sports or diets low in protein
and high in carbohydrate
– Sweat losses may approximate 8-9% of the RDA
– Wrestlers who diet and sweat for weight control
– Some suggest suppression of growth
– Recent reviews indicate exercise does not cause a zinc
deficiency or that a marginal deficiency impairs
performance
Zinc
• Supplementation: Effects on health:
– Beneficial
• May improve growth and development of zinc-deficient children
• May be useful to help prevent ARMD
– Detrimental
• Excess supplement intake may impair other mineral absorption
• May increase LDL- and decrease HDL-cholesterol
– Neutral
• Appears to have little effect on immune functions and prevention
of the common cold
Zinc
• Supplementation: Effects on sport:
– Limited research; study with untrained women; mixed results
• Additional research merited
Zinc
• Prudent recommendations:
– Consume diet rich in protein foods
– Wrestlers, other weight-control athletes focus on zinc-rich
foods
– Supplementation not recommended
Chromium
• Symbol: Cr
• Dietary Reference Intakes (DRI):
– AI = 35 mg adult males, 25 mg adult females
– UL = None established
– DV = 120 mg
Chromium
• Good food sources:
– Whole grains, baked beans, nuts, cheese, asparagus, beer
– One slice of bread provides about 15% or the AI
• Major functions in humans:
– Component of the glucose-tolerance factor associated
with insulin
– May enhance insulin effect
Chromium
• Deficiency: Effects on health:
– Clinically manifest deficiencies are rare
– Role in development of diabetes being studied
Chromium
• Deficiency: Effects on sport performance:
– Possible losses or increased needs of chromium by
athletes
• Losses in sweat and urine with intense exercise
• A high-carbohydrate diet may increase Cr needs
• Weight loss for performance could decrease dietary Cr
intake
– Adverse effects on carbohydrate metabolism, if
any, could impair endurance
Chromium
• Supplementation: Effects on health:
– Research results are inconclusive
– Some studies show improved glucose control in diabetics,
but not in those without diabetes
– Some studies have found ↓ total and LDL-cholesterol and
↑ HDL-cholesterol
– Chromium may only work when correcting a deficiency
– Additional research needed before definitive claims about
Cr supplementation may be made
– Detrimental effects of long-term supplementation not
known. The Institute of Medicine recommends additional
research to help resolve any uncertainties
•
Chromium
• Supplementation: Effects on exercise performance
– Theories:
• Enhance carbohydrate metabolism
• Enhance anabolic effect of insulin
• Marketed as a means to lose fat and gain muscle
– Research findings:
• An early review of two studies suggested ergogenic
effects
• Numerous contemporary well-designed studies
reported no beneficial ergogenic effects
Chromium
• Prudent recommendations
– Diabetics – Consult your physician concerning
supplementation
– Supplements do not appear to be warranted for the
general population
– Take only 200 mcg at the most if you take supplements,
possibly best as part of a multivitamin/mineral tablet
Selenium
• Symbol: Se
• Dietary Reference Intakes (DRI):
– RDA = 55 mcg
– UL = 400 mcg
– DV = 70 mcg
Selenium
• Good food sources:
– Seafood, organ meats
– Grains grown in selenium-rich soil
– 3 ounces of meat or grains contain about 30 mcg
• Major functions in humans:
–
–
–
–
Selenoproteins, enzymes such as glutathione peroxidase
Works with vitamin E as an antioxidant
Involved in immune functions
Theorized to help prevent cancer
Selenium
• Deficiency: Effect on health:
– Cardiomyopathy – areas with low soil selenium
– Impaired immune function
– Epidemiological studies show link to cancer (prostate
cancer)
• Deficiency: Effect on sport performance:
– Theorized to impair antioxidant functions, leading to
muscle tissue damage
Selenium
• Supplementation: Effect on health:
– Heart disease
• May be effective to treat cardiomyopathy caused by Se
deficiency in China
• Some epidemiological data show an inverse
relationship between selenium levels and CHD, but the
validity of this association is questioned given recent
experimental studies with antioxidants and heart
disease
Selenium
• Supplementation: Effect on health:
– Cancer
• SELECT (Selenium and vitamin E cancer prevention trial)
was to end in 2012
• Study stopped prematurely late in 2008
• No effect of either Se or E alone or combined on
prostate cancer
• Small increase in type 2 diabetes in men taking Se
– Side effects of excess
• Nausea, vomiting, fatigue
• Thyroid hormone deficiency
Selenium
• Supplementation: Effect on sport:
–
–
–
–
Limited research with selenium by itself
Often combined with other antioxidants in a “cocktail”
No antioxidant effect on muscle tissue damage
No performance-enhancing effect
Selenium
• Prudent recommendations:
– Select selenium-rich foods
– Supplements not recommended to prevent cardiovascular
disease
– Supplements should not contain more than 100-200 mcg
Boron
• Symbol: B
• Dietary Reference Intakes (DRI):
– RDA or AI = None established
• One proposed safe intake is 1-13 mg
– UL = 20 mg
Boron
• Good food sources:
– Dried fruits, nuts, legumes, vegetables, milk, grape juice,
wine
– 5 servings of fruits and vegetables, along with some
legumes and nuts could provide 3 mg
• Major functions in humans:
– May affect cell membrane to influence mineral
metabolism
– May influence steroid hormones (estrogen, testosterone)
to affect bone metabolism
Boron
• Deficiency; Effect on health:
– Role in human metabolism is poorly understood
– May be involved in bone metabolism (estrogen related)
• Deficiency: Effect on physical performance:
– Theorized that reduced testosterone production could
impair muscle growth
Boron
• Supplementation - effects on health:
– Nielsen study created a boron deficiency in postmenopausal women over 4 months. Then, the diet was
supplemented with 3 mg boron for 4 months to correct
the boron deficiency
– Helped restore normal calcium metabolism
– Increased serum estrogen and testosterone
– The study evaluated the effects of a boron deficiency and
restoration to normal
– Newspaper headlines: Boron Builds Bones
– Within a few months boron supplements for bone health
were on the market
Boron
• Supplementation: Effect on physical performance
– Theory
• Based on the Nielsen study, boron supplements would
increase testosterone levels (anabolic effects)
• Example of purposeful misinterpretation of study data
– No ergogenic effects noted in subsequent studies with
resistance-trained males
• Prudent recommendations:
– A healthful diet should provide adequate amounts of
boron
Vanadium
• Symbol: V
• Dietary Reference Intakes (DRI):
– RDA or AI = None established
– 10 mcg has been postulated as adequate
– UL = 1.8 mg
Vanadium
• Good food sources:
– Shellfish, meat, whole grains, mushrooms, dairy foods
– Average American diet provides about 15-30 mcg daily
• Major functions in humans:
– Not known; possible insulin-like effect
Vanadium
• Deficiency: Effects on health:
– Not detected in humans
– Theorized to impair glucose metabolism
• Deficiency: Effects on sport performance:
– Not detected in humans
– Theorized to impair glucose metabolism during aerobic
exercise
Vanadium
• Supplementation: Effect on health:
– May improve insulin sensitivity in diabetics, but not nondiabetics
– In excess, may cause GI distress, diarrhea; liver and kidney
damage
• Supplementation: Effect on physical performance
– Limited research; evidence not supportive of an ergogenic
effect
Vanadium
• Prudent recommendations:
– Supplements not recommended for non-diabetics, athletes
– Diabetics should consult with their physicians prior to
supplementation
Other Trace Minerals
• Fluoride
– Helps in prevention of dental caries
• Iodine
– Iodized salt helps prevent goiters
• Others
Mineral Supplements:
Exercise and Health
• Mineral supplements are marketed for both health
and sport performance
• Mineral supplementation may enhance health or
exercise performance if a mineral deficiency is
corrected
• Mineral supplements do not appear to affect health
or exercise performance in individuals whose mineral
status is adequate
Does exercise increase
my need for minerals?
• Possible reasons for increased needs
–
–
–
–
–
–
–
Losses of some minerals in sweat
Losses of some minerals in urine
Losses of some minerals from the gastrointestinal tract
Losses of some minerals from excess menstrual flow
Increased need from effects of amenorrhea
Increased need for training at altitude
Increased need in weight-control sports
Can I obtain the minerals I need
through my diet?
• The key is to eat a wide variety of foods among and
within the various food groups or food exchanges
– Table 8.6 highlights the variability of minerals among the
various food groups
• Remember the “Key Nutrient” concept
– Eating foods rich in calcium and iron should provide
adequate amounts of other essential minerals
Foods rich in Key Minerals
Starches
and
Grains
Fruits,
Vegetables,
citrus and dark green
others
and others
Phosphorus Magnesium Calcium
Magnesium
Phosphorus
Iron
Magnesium
Zinc
Iron
Chromium
Zinc
Selenium
Selenium
Meat,
fish,
poultry
Milk and
dairy
products
Fats and
Oils
Iron
Calcium
Trace
Zinc
Magnesium amounts
Chromium Zinc
Selenium
Are mineral megadoses or some
nonessential minerals harmful?
• Excess amounts of minerals normally do not occur
from diets of natural, wholesome foods
• Consuming mineral supplements along with fortified
foods can lead to excess mineral intake
• All trace minerals appear to be toxic if consumed in
excess over long period of time
• Nonessential minerals may impair health
– Lead
– Mercury found in fish
Should physically active individuals take
mineral supplements?
• In general, no. You can get the minerals you need via your diet
• Mineral deficiencies to the point of adversely affecting
exercise performance are rare.
– However, some athletes may need iron
• Some athletes at risk for bone loss may benefit from calcium
supplements.
• Minerals in excess may be harmful over time
• Consult a health professional, sport nutritionist
• If you do not consult a health professional, try to stick with
the typical One-a-Day multivitamin/mineral.
Vitamin/mineral supplements
• Calcium
– Buy a supplement with calcium if you are female or elderly
and do not obtain adequate amounts in the diet
– Most supplements contain 200-300 mg
• Iron, copper, zinc
– Buy a supplement limited in these minerals, with no more
than 100 percent of the RDA for each
– Iron DV is 18 mg, but male and postmenopausal female
RDA is only 8 mg
Vitamin/mineral supplements
• Magnesium and phosphorus
– Buy a supplement containing no more than 100 mg of
magnesium and limited in phosphorus
• Chromium and selenium
– Buy a supplement containing 100 percent of the AI for
chromium and RDA for selenium
Vitamin and mineral supplementation
• Think food first!
• Foods contain numerous phytonutrients in addition
to vitamins and minerals