Transcript Chapter 2 part 2

The Micronutrients and Water
Part 2
Chapter 2
Content in Body
The Minerals An Overview
• Inorganic elements
– Maintain their structure; hard to destroy
– Not changed in body; remain their until excreted
• The body’s handling of minerals
– Some need to be complexed with proteins (e.g. iron)
– Some can be toxic
• Variable bioavailability
– Binders; bind minerals and lower their availability
• Phytates: legumes and grains
• Oxalates: spinach
• Nutrient interactions:
– High sodium causes excretion of Na+ and Ca2+
– Phosphorous bnds magnesium, limits it’s absorption
• Varied roles
Copyright 2005 Wadsworth Group, a division of Thomson Learning
Minerals
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Consist of 22 mostly metallic elements
Minerals essential to life
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7 major minerals (required in amounts >100 mg
daily)
14 minor or trace minerals (required in amounts
<100 mg daily)
A balanced diet generally provides
adequate mineral intake, except in some
geographic locations lacking specific
minerals.
Roles of Minerals
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Provide structure in the formation of
bones and teeth
Help to maintain normal heart rhythm,
muscle contractility, neural
conductivity, and acid-base balance
Regulate metabolism by becoming
constituents of enzymes and
hormones that modulate cellular
activity
Mineral Bioavailability
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Factors that affect the bioavailability of
minerals in food
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Type of food
Mineral–mineral interaction
Vitamin–mineral interaction
Fiber–mineral interaction
Bioavailability
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Mineral-mineral competition
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Similar size
Similar electrical charges
Ex: magnesium, calcium, iron, copper
Competition for absorption
Vitamins-mineral competition
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Vitamin C improves iron absorption
Vitamin D improves calcium absorption
Calcium
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Most abundant mineral in body
Most is found in the bones (99%)
Blood calcium (1%)
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Kept in balance with hormones and
vitamin D.
Blood calcium maintained at the
expense of bone calcium.
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ECF levels of calcium decrease
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Kidneys reabsorb Ca
Calcium
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Peak bone mass
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Bone’s fullest potential in size and density
Developed in the first three decades of life.
Osteoporosis
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Chronic condition
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Porous bones
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Osteopenia
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Reduced bone density
Weakened bones
These are progressive diseases
Calcium is leeched from bones to meet
body’s needs
Osteoporosis
Risk of Osteoporosis
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Advanced age
White or Asian female
Slight build or tendency to
be underweight
Anorexia nervosa or
bulimia nervosa
Sedentary lifestyle
Postmenopause, including
early or surgically induced
menopause
Low testosterone levels in
men
High protein intake
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Excess sodium intake
Cigarette smoking
Excessive alcohol use
Abnormal absence of
menstrual periods
Calcium-deficient diet in
years before and after
menopause
Family history of
osteoporosis
High caffeine intake
(possible)
Vitamin D deficiency
Prevention
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Diet
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Exercise
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Weight bearing
Wolff’s law
Estrogen supplementation
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Prime defense: adequate calcium in diet
Post-menopause
Increases GI absorption, reduces renal excretion,
facilitates absorption into bone
Appropriate age of Menarche
The Female Triad
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The Triad usually begins with
disordered eating and leads to
amenorrhea and then osteoporosis.
Women who train intensely and cut
calories below energy requirements
may adversely affect menstruation.
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Oligomenorrhea – irregular cycles
Amenorrhea – cessation of menstruation
The Female Triad
Calcium
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Calcium Roles in the Body
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Calcium in Bones
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Mineralization - minerals crystallize,
hardening of the bone.
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Remodeling constantly taking place.
 Bone destroying cells (osteoclasts) – resorption
 Bone forming cells (osteoblasts) – synthesize
Calcium Balance
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Works with vitamin D
Works with parathyroid hormone and
calcitonin
Calcium
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Calcium Roles in the Body
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Calcium Absorption
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Absorption rate for adults is 25% of calcium
consumed.
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50% during pregnancy
50-60% during growth
Calcium
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Factors that inhibit absorption
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Lack of stomach acid
Vitamin D deficiency
High phosphorus intake
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Need to increase Ca intake for balance
High-fiber diet
Calcium
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Calcium Recommendations
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AI Adolescents: 1300 mg/day
AI Adults: 1000 mg/day if 19-50 years of
age
AI Adults: 1200 mg/day if greater than 50
years of age
Upper level for adults: 2500 mg/day
Calcium
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Toxicity symptoms
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Constipation,
Increased risk of urinary stone formation,
Kidney dysfunction,
Interference with the absorption of other
minerals.
Calcium
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Calcium Sources
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Calcium in Milk Products
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Drink milk.
Eat yogurt and cheese.
Add dry milk during food preparation.
Phosphorus
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Phosphorus Roles in the Body
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Mineralization of bones and teeth (85%)
Part of every cell (buffer)
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Buffer systems that maintain acid-base
balance
An essential component of AMP, PCr,
and ATP
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Adenosine triphosphate (ATP)
Phosphocreatine (PCr)
Phosphorus
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Phosphorus Roles in the Body
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Ph + calcium forms hydroxyapatite and
calcium phosphate
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During mineralization – crystals become
denser
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Provide strength and rigidity - Bones and teeth
Combines with lipids to form
phospholipids
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Part of the cell membrane – lipid bilayer
Phosphorus
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Phosphate enzymes regulate cellular
metabolism
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Thiamin pyrophosphatase
Glucose-6-phosphatase
Phosphorus
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Phosphorus Recommendations
RDA Adults: 700 mg/day for ages 1970 years
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Upper intake level for those 19-70 years
of age is 4,000 mg/day.
Phosphorus
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Sources
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Animal foods including meat, fish and
poultry
Milk
Eggs
Toxicity
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Calcification of nonskeletal tissues,
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Kidneys.
Magnesium
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Helps to regulate metabolism-400
enzymes (including all involved in
ATP, RNA and DNA synthesis)
ATP exists in cells as mg2ATP
Acts as cofactor in glucose, protein
and fat metabolism
Lipid and protein synthesis
Magnesium
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Allows the neurologic system to
function properly
Supports bone mineralization
Regulates cell growth, reproduction
Magnesium
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Magnesium Intakes (1997 RDA)
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RDA Adult Men: 400 mg/day for 19-30
years of age
RDA Adult Women: 310 mg/day for 19-30
years of age
Upper level for adults: 350 mg nonfood
magnesium/day
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Supplements
Magnesium
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Sources
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Nuts and legumes, whole grains, dark
green vegetables, seafood, chocolate
and cocoa
Hard water and some mineral waters
Magnesium
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Deficiency
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Deficiencies are rare.
Symptoms
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Weakness and confusion
Convulsions in extreme deficiency
Bizarre muscle movements of the eye and face
Hallucinations
Difficulties in swallowing
Growth failure in children
Magnesium
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Magnesium Toxicity
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Rare, potentially fatal
Symptoms
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Diarrhea, alkalosis, and dehydration.
Iron
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Most is combined with hemoglobin in
red blood cells.
A structural component:
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Myoglobin
Cytochrome
Iron
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Some does not combine in functionally
active compounds
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hemosiderin and ferritin
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Storage form of iron in the liver, spleen, and
bone marrow.
Transferrin
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Transports iron
Iron
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About 40% of American women of
childbearing age suffer from dietary
iron insufficiency
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Could lead to iron-deficiency anemia.
Symptoms
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Sluggishness,
Loss of appetite
A decreased ability to sustain even mild
activity
Sources of Iron
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Nonheme iron
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Primarily found in plant products
2-10% absorption by the intestines
Heme iron
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Primarily found in animal products
10-35% absorption by the intestines
Vegetarian Diets
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Nonheme iron
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Low bioavailability.
Women on vegetarian-type diets
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Greater risk for developing iron
insufficiency.
Vegetarian Diets
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To increase intestinal absorption of
nonheme iron.
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Vitamin C
Moderate physical activity
Iron-Deficiency
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Most at risk:
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Infant, toddler, chronic blood loss,
vegans, runners, and women of
childbearing years
Signs:
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Paleness, brittle nails, fatigue, poor
temperature control, poor growth
Iron Toxicity
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Serious, especially for children
Signs:
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Diarrhea, constipation, nausea, abdominal pain
Causes death due to respiratory collapse (shock)