Download Minerals/water

7/13/2015
Minerals and water
MAIN QUESTIONS TO ANSWER:
• What are some major functions of water in the body?
• For each mineral,
– what are the best dietary sources?
– what are the physiological functions?
– what are the results of deficiency? Who is most at risk?
– what are the potential risks associated with excessive
intake?
Water
Water is the major constituent of the body; but its ‘stores’ in the body
are very limited. Water can be obtained from many food sources.
•Functions of Water in the body
–Temperature regulation
–Medium for chemical reactions and waste elimination
–Component of body fluids
•Thirst
–often, but not always, a reliable response to water loss…
–thirst is often sensed when < 2% of body water is lost
•Dehydration and Rehydration
–Water balance: input vs. output
–Some water loss cannot be prevented
–Different types of dehydrations
–Water & minerals typically required for rehydration
Minerals
Minerals have many regulatory & structural functions in body. Their
absorption depends on many dietary & other factors….
•Major minerals: typical adult requires > 100 mg/d; most abundant
in body, > 5g
Sodium (Na)
Chloride (Cl)
Phosphorus (P)
Potassium (K)
Calcium (Ca)
Magnesium (Mg)
Sulfur (S)
•Minor or Trace minerals: typical adult requires < 100 mg/d; usually
< 5 g in body
Iron (Fe)
Copper (Cu)
Iodide (I)
Chromium (Cr)
Molybdenum (Mo)
Zinc (Zn)
Selenium (Se)
Fluoride (F)
Manganese (Mn)
Cobalt (Co)
and more…….
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Sodium
• Recommended intake, major dietary sources, availability:
– AI, 1500 mg/d (adults < 50)
– processed foods; table salt
– easily absorbed…..excess in typical Canadian diet
• Some main functions of Na
– water balance in body (extracellular); nerve conduction
• Deficiency/depletion of Na
– can occur in some situations: e.g., vomiting & diarrhea; extreme perspiration
(exercise, heat); low sodium diet
– results: muscle cramps, dizziness, nausea……shock, death
• Excessive intake/toxicity of Na
– greater risk for infants….immature kidneys
– Rapid changes in blood Na can be dangerous
– Many people are Na-sensitive in terms of hypertension: ↓ intake can help
control hypertension
Potassium
• Recommended intake, major dietary sources, availability:
– AI, 4700 mg/d (adults)
– milk; fruits & vegetables, coffee/tea, whole grain cereals…..
• Functions of K
– Water balance in body (intracellular)
– Nerve conduction
– Normal cardiovascular function
• Deficiency/depletion of K
– Can usually occur in several ways: e.g., use of some diuretics; frequent
vomiting, diarrhea
– Can severely reduce heart function….death
• Excessive intake/toxicity of K
– Unlikely from foods esp. with normal adult kidney function; possible with
overuse of some (K-saving) diuretics
– Can severely affect heart function….death
Hypertension
• Incidence & associated problems: about 20% of Canadian adults
(higher with age); increases risk of heart disease and stroke, kidney
disease…..many other organs affected over time
• Risk factors
–
–
–
–
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obesity
lack of physical activity
high sodium intake
high alcohol intake
others... Smoking; Low potassium intake; Genetics….
• Prevention/control:
– Control risk factors, above (if possible)
• e.g., ↑ fruits & vegetables…often leads to ↑ potassium & ↓ sodium intakes & ↓ calories
– Pharmacological treatments...
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Chloride & Sulfur
Chloride
• AI, 2300 mg/d (adults, < 50y); major sources: table salt, most other
foods
• Functions of Cl:
– Water balance in body (extracellular)
– Nerve conduction
– Stomach acid (hydrochloric acid)
Sulfur/Sulphate
• Mostly obtained from dietary protein
• Functions of S:
–
–
–
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Part of some amino acids & vitamins
Protein structure
Some detoxification reactions in the body
Part of antioxidant glutathione
Calcium
• Recommended intake, major dietary sources, availability:
– AI, 1000 mg/d (adults, <50)
– Milk & dairy products; green leafy vegetables…
– absorption competed by several dietary factors…
• Functions of Ca
– Form & maintain bone structure
– Blood clotting; Muscle contraction; Nerve function
– Many other cell regulation functions
• Deficiency/depletion of Ca
– May occur with vitamin D deficiency
– Blood Ca level maintained at expense of bone
– Osteoporosis may result with long-term deficiency….critical periods
• Excessive intake/toxicity of Ca
– Not common... can lead to constipation, increased risk of kidney stones
Phosphorus & Magnesium
Phosphorus
• Recommended intake, major dietary sources, availability:
– RDA, 700 mg/d (adults, <50); many sources in diet (e.g., dairy products, meat)
• Functions of P
– Part of many biomolecules; Fluid balance (intracellular)
– Deposited with Ca in bones
Magnesium
• Recommended intake, major dietary sources, availability:
– RDA, 320-420 mg/d (adults, f-m); some sources: whole-grain cereals,
vegetables, dairy products, ‘hard’ water
• Functions of Mg
– Cofactor required by 100s of enzymes; Functional part of ATP
– Nerve & Heart function
• Excessive intake/toxicity of Mg: diarrhea……rarely: kidney problems (UL for
supplements)
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Osteoporosis
• Bone mass reduction….porous, fragile bones, most common in elderly;
Increased risk of fractures: wrist, hip, vertebrae…
• Some risk factors
– old age, underweight….genetics…Caucasian
– female, early menopause, low estrogen
– low Ca/Vitamin D intakes
– lack of physical activity, smoking
– high alcohol consumption
• Prevention/control
– Control risk factors, above (if possible)….
– others under study: avoid very high/very low protein intake? Avoid high sodium
intake? Ensure sufficiency of vitamin K?
– Pharmacological treatments/hormones for prevention...
(trace minerals)
Iron
• Recommended intake, major dietary sources, availability:
– RDA, 8-18 mg/d (adults, m-f, f before menopause); sources: meats & eggs,
cereals & vegetables/beans, fortified foods, iron cookware
– absorption depends on body’s Fe need; dietary factors can ↑ or↓ absorp.;
heme vs non-heme iron
• Transport & storage of Fe: Some stored in intestine, liver, bone marrow
(Fe-ferritin); Transferrin is a circulatory Fe carrier protein
• Functions of Fe: oxygen carrier (part of hemoglobin/myoglobin); component
of some enzymes; needed by all cells
• Deficiency/depletion of Fe:
– Low intake: e.g., prolonged milk diet in children; blood loss; some
vegetarians at increased risk
– Iron-deficient anemia: decrease oxygen-carrying capacity of blood
• Excessive intake/toxicity of Fe
– Example: ‘accidental’ intake of iron pills or iron-fortified vit/mineral suppl.
– Hemochromatosis—genetic defect
• Liver and heart damage.....oxidative damage....
Zinc
• Recommended intake, major dietary sources, availability:
– RDA, 8-11 mg/d (adults, f-m); sources: meats, nuts, whole grain cereals…
– up to ½ in diet is absorbed (↑ abs. from animal products)
– absorption can be decreased by other dietary factors…
• Functions of Zn
– Cofactor for 100s of enzymes
– Immune function; Reproductive development; Bone & body growth
• Deficiency/depletion of Zn
– Can occur in association with protein malnutrition
– Genetic defect……low absorption
– Deficiency affects growth, sexual maturation, hair, neurological and immune
systems, taste/smell
• Excessive intake/toxicity of Zn…excess can be toxic…
– decreased Cu/Fe absorption
– lower HDL levels?
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Copper & Iodide
Copper
• Recommended intake, major dietary sources, availability: RDA, 900
mcg/d (adults); sources: whole grain cereals, beans, nuts…; ~ ½ in diet is abs.
• Functions of Cu: Cofactor in several enzymes; collagen production; Iron
mobilization and utilization; Immune function
• Deficiency/depletion of Cu: Rare with normal diet and lack of genetic
defects (inherited diseases….); Anemia & poor growth
• Excessive intake/toxicity of Cu: Can be toxic; supplements (not foods) pose
greatest risk; ….↑oxidative stress; Wilson’s disease: Neural, liver toxicities
Iodine
• Recommended intake, major dietary sources, availability: RDA, 150 mcg/d
(adults): sources: marine foods, iodized table salt
• Storage & mobilization: over 80% in thyroid gland [thyroglobulin (TG)]; TG
broken down to release thyroid hormone (TH)
• Functions: TH, many regulatory functions: metabolic rate, protein synthesis,…
• Deficiency/depletion: thyroid gland grows to capture more I...goiter
• Excessive intake/toxicity: can inhibit I-TG formation….another type of goiter
Selenium
• Recommended intake, major dietary sources, availability:
– RDA, 55 mcg/d (adults): sources: animal products, plants from Se-rich soil
• Functions of Se
– antioxidant: part of antioxidant enzyme (GPX)
– activation of TH
• Deficiency/depletion of Se
– can occur in low-Se geographic areas
– muscle weakness
– Increased oxidative stress?
• Excessive intake/toxicity of Se
– hair loss, fatigue, GI irritation…
Nutrient Supplements
Who is most likely to need them? Some examples:
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Pregnancy……Folate & Iron
Very low calorie diets...micronutrients
Vegans...e.g., vitamin B12
Newborns...vitamin K
Elderly...vitamins D, B12…..
With some medications/diseases…
►Controversial question: should multi-vit/min supplements be widely
recommended for adults?
Some possible problems with reliance on supplements:
If pills taken instead of…….increasing fruit/vegetable consumption;
decreasing smoking/alcohol; regular physical activity…..
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Some special cases: interference with other nutrients or drugs…..;
high-dose toxicity.
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