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) Potassium (K) Chloride (Cl) Calcium (Ca) Phosphorus (P) Magnesium (Mg) Sulfur (S) Minor or Trace minerals: typical adult requires < 100 mg/d; usually < 5 g in body Iron (Fe) Zinc (Zn) Copper (Cu) Selenium (Se) Iodide (I) Fluoride (F) Chromium (Cr) Manganese (Mn) Molybdenum (Mo) Cobalt (Co) and more. 1
Sodium 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 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 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... 2
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: Part of some amino acids & vitamins Protein structure Some detoxification reactions in the body Part of antioxidant glutathione Calcium 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 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 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) 3
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 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 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? 4
Copper & Iodide Copper 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 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 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: - 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.. - Some special cases: interference with other nutrients or drugs..; high-dose toxicity. 5