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Chapter 7 + notes

Professor: Snehil Dua...

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Chapter 8: Water and Minerals Water  Most indispensable of all nutrients •

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Can survive only a few days without water

Makes up 60% of adult body weigh •

Arteries, veins, capillaries, cells, tissues, organs

Water 

Functions: • • • • • •

Transport vehicle for nutrients and wastes Universal solvent Body’s cleansing agent Lubricant/cushion for joints Protection for sensitive tissue Maintenance of body temperature

Water Balance 

Lose water everyday – must consume at least the same amount (Fig 8.2)

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Thirst: Pituitary gland signaled to release hormone – kidney shift water back to bloodstream (urine output decreased) • When blood too concentrated, or blood volume/pressure too low, hypothalamus initiates nerve impulse • Lags behind lack of water •

Water Balance 

Dehydration: Loss of water • Symptoms: (Table 8.1) thirst → weakness → exhaustion → delirium → can lead to deat •

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Water intoxication: Dilution of body fluids due to excessive intake of plain water. • Symptoms: headache, muscular weakness, lack of concentration, poor memory, loss of appetite •

How much do we need? 

DRI meets ≈80% of day’s need for water Men: 13 cups of fluid from beverages and drinking water • Women: 9 cups of fluid from beverages and drinking water • Remaining water need is met from foods consumed • Body produces water from the breakdown of energy-yielding nutrients •

Just Water? 

Water Content of Various Foods: (p.276) 100% - water, diet soft drinks, plain tea, unflavoured seltzer • 99-95% - sugar-free gelatin dessert, clear broth, Chinese cabbage, celery, cucumber, lettuce, summer squash, decaf black coffee • 90-94% - Gatorade, grapefruit, fresh strawberries, broccoli, tomatoes • 80-89% - soft drinks, milk, yogurt, egg white, fruit juice, low-fat cottage cheese, carrot, fresh apple •

Increased Fluid Needs 

Sweating / physical activity can increase fluid requirements  Other factors: (Table 8.2)

Body Fluids and Minerals 

Most of body’s water inside the cells; some on outside •

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Major minerals for salts •

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Remainder fills blood vessels Water follows salt

Cells move salts across their membranes •

Prevents collapse / swelling

Body Fluids and Minerals 

Electrolytes: •

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Compounds that partly dissociate in water to form ions (electrically charged particles)

When electrolytes present in unequal concentrations on sides of permeable membranes water flows to more concentrated side (Fig 8.3)

Fluid and Electrolyte Balance 

Fluid and electrolyte balance: •

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Proper amount and kind of fluid in body compartments (Fig 8.4)

Imbalance: E.g. vomiting, diarrhea • Severe illness can develop quickly – medical emergency • Cause of death in eating disorders •

Minerals 

7 Major minerals (based on quantity, Fig. 81): •

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calcium (Ca), phosphorus (P), potassium (K), sulfur (S), sodium (Na), chloride (Cl), magnesium (Mg)

Trace minerals: iodine (I), iron (Fe), zinc (Zn) • copper (Cu), selenium (Se), fluoride (F), chromium (Cr), manganese (Mn), molybdenum (Mo) •

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Table 8.11: The Minerals – A Summary

Functions 

Electrolytes: Na, K, Cl maintain water balance in cells & blood • Na & K: used in muscle contractions & nerve transmission •

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Body structure: Ca, P, Mg, F, Zn •

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bones, teeth

Structure of DNA, RNA, phospholipids and ATP (energy molecule): P

Functions 

Protein structure: Fe, Zn, Ca, Se, I •

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Cell signaling & communication: Ca, Na •

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the protein and the element are bound to make a specific shape and thus function, e.g. Fe & hemoglobin, I & thyroid hormone Ca moves across cells as a messenger, stimulating proteins and cell activity

Antioxidant defense: Zn, Cu, Mn, Se, S •

components of defense enzymes

Calcium 

Functions: • 1% of Ca in fluids in and around cells:  transport of ions over cell membranes  nerve transmission  maintenance of normal blood pressure  muscle contraction – heartbeat  blood clotting  secretion of hormones, digestive enzymes and neurotransmitters  activation of cellular enzymes

Calcium •

99% in bones and teeth:  integral part of bone structure  storehouse of Ca for release when needed

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Recommendations: DRI: 1,000 mg/d, UL: 2,500 mg/d • Recommendations for children and adolescents higher – peak bone mass •

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Food Sources: (Snapshot 8.1 & Food Feature p.307) •

Milk products, some leafy green vegetables (Fig 8.11), calcium set tofu, canned sardines/salmon (with bones)

Calcium Regulation 

When blood Ca concentration decreases, body adapts by: mobilizing Ca from bone • increasing absorption of Ca by the small intestine •

 Children – 60%  Pregnant women – 50%  Healthy adults – 25% •

preventing loss of calcium from the kidneys

Calcium  Peak

bone mass: (Fig C8.3)

Highest attainable bone density – developed by late 20’s ~ early 30’s • After age 40, begin to lose bone mass, however loss can be minimized   sufficient calcium intake in children and adolescents very important •

 Deficiency: •

Osteoporosis: weak, brittle bones; fractures Controversy 8

Phosphorus 

Functions: • • • • • •

Maintenance of acid-base balance of cellular fluids Part of DNA & RNA - tissue growth & renewal Metabolism of energy containing nutrients Help enzymes and vitamins take energy from nutrients Structural part of phospholipids Present in some proteins

Phosphorus 

Most of the phosphorus in the body is stored in the bones and teeth  Recommendations: •

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Deficiency: very rare •

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DRI: 700 mg/d, UL: 4,000 mg/d muscular weakness, bone pain

Toxicity:

calcification of soft tissue (kidneys)  Food Sources: (Snapshot 8.2) • Milk products, canned salmon, lean beef •

Magnesium 

Functions: • • • • • •

Assists with operation of enzymes Release and use of energy from nutrients Affects the metabolism of other minerals: potassium, calcium and vitamin D Forms part of protein-making machinery in the body Proper functioning of muscles (Ca: contractions, Mg: relaxes muscles) Promotes resistance to tooth decay

Magnesium 

Over 50% stored in bones •

When intake low:  magnesium released from bone to maintain blood levels  kidneys conserve magnesium (less excretion)

•



Low intakes of Mg rich foods may increase risk of disease development

Recommendations: • •

DRI: men – 400mg/d, women – 310mg/d UL: 350mg/d (supplement / drugs only; not food magnesium)

Magnesium 

Deficiency: (low intake, vomiting, diarrhea)

Weakness, confusion; extreme: uncontrollable muscle contractions (heart), hallucinations, swallowing difficulties, growth failure  Toxicity: rare (non-food sources only) • Diarrhea, dehydration, Ph imbalance  Food Sources: (Snapshot 8.3) • Legumes, cooked spinach, bran cereals, oysters, yogurt, wheat bran • Easily washed and peeled away;  unprocessed foods better sources •

Sodium 

Functions: Chief ion used to maintain fluid volume outside cells • Maintenance of acid-base balance • Essential for muscle contractions • Essential for nerve transmission •

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Sodium is part of table salt (NaCl)

40% weight; 1g salt has 400mg sodium  Recommendations: (Table 8.5) (Fig 8.7) • DRI: 1,500 mg/d UL: 2,300 mg/d (5.6g salt) •

Sodium 

Deficiency: very rare •

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Toxicity: •

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Muscle cramps, mental apathy, loss of appetite Hypertension (high blood pressure)

Excess sodium in the diet: • • • •

Increases calcium excretion May directly stress a weakened heart May directly aggravate kidney problems ? Increased risk stomach cancer

Sodium and Body Fluids 

When high sodium foods taken in, thirst ensure that enough water in consumed to restore sodium-water ratio • kidneys filter out excess sodium in the urine •

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Hypertension: Population studies: as sodium intake increases, average BP increases (direct correlation) • As BP increases, risk of death from CVD ↑ •

Sodium 

Effect greater in salt sensitive people •

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Diabetes, HTN, kidney disease, African descent, family history, age (over 50)

Dietary Intervention: Reduce sodium intake & increase potassium intake • DASH Diet (Dietary Approaches to Stop Hypertension) [salt and sodium reduced] •

 increased intake of fruits and vegetables, moderate amounts of nuts, fish, whole-grains, low-fat dairy  Occasional red meat, butter, high-fat foods, sweets

Reducing Sodium Intake 

Table 8.6 and Fig 8.8  Control the salt shaker •

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Cut down on processed and fast foods •

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1 tsp salt = almost 2,400 mg sodium Unprocessed foods tend to be lower in sodium and higher in potassium

Watch condiments  Read labels!!!

Potassium 

Functions: Chief positive ion used to maintain fluid volume inside cells • Maintenance of fluid and electrolyte balance • Maintenance of cell integrity • Critical to maintaining heartbeat •

 Sudden deaths during fasting, eating disorders, severe diarrhea, kwashiorkor attributed to heart failure resulting from potassium loss

Potassium 

Dehydration causes potassium loss from inside cells When brain cells lose potassium, no longer notice need for water • Caution with diuretics important •

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Recommendations: DRI: 4,700 mg/d • Typical diet low in fruits and vegetables •

 Only ~ half of potassium requirements met in Canada

Potassium 

Deficiency: Muscle weakness, paralysis, confusion, heart failure • Low potassium intake can: •

 Worsen hypertension  Cause impaired glucose tolerance  Increase metabolic acidity  Accelerate Ca loss from the bones  Increase the likeliness of kidney stone formation

Potassium 

Toxicity:

Muscle weakness, vomiting, extreme: potassium in large doses can stop the heart • Potassium chloride pills should not be used unless doctors advice • Overdose of potassium via mouth – stomach triggers vomiting reflex (infants exception)  Food Sources: (Snapshot 8.4) • Best sources: fresh, whole foods • Fruits and vegetables, legumes •

Chloride 

Function: Helps sodium maintain fluid, electrolyte and acid-base balance • Part of hydrochloric acid – stomach acidity •

 Protein digestion 

Source:

Added and naturally occurring salt (sodium chloride) • No known diet lacks chloride  Recommendations: DRI – 2,300 mg/d, UL: 3,600mg/d •

Sulfate 

Functions: •

Synthesis of important sulfur containing compounds  E.g. the a.a’s that form the proteins in skin, hair and nails

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No recommended intake Deficiency not seen • Toxicity (often from drinking water) may cause diarrhea or damage to colon •

Trace Minerals: Iodine 

Function: •

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Recommendations: •

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Part of thyroxine (thyroid hormone, regulates BMR) 150 ug/d; UL: 1,100ug/d

Food Sources: seafood, foods grown in soil rich in iodine (varies) • additive: iodized salt, milk (iodine used to disinfect equipment), baked goods (iodine containing dough conditioner) •

Iodine 

Deficiency: thyroid gland enlarges – goiter (p.293) • sluggish, weight gain, in pregnancy – cretinism • one of most common and preventable causes of mental retardation •

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Toxicity: can also enlarge the thyroid gland • poisonous •

Iron 

Functions: Part of hemoglobin (RBC) & myoglobin (muscle) [oxygen-carrying proteins] • Needed for energy metabolism •

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Recommendations: (Table 8.9) DRI: men - 8mg/d, women - 18mg/d; UL - 45mg/d • Pregnancy: 27mg/d • Vegetarians: 1.8x DRI •

Iron 

Deficiency: •

•

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Iron-deficiency anemia: small, light-coloured RBC (microcytic),  delivery of oxygen to tissues, Figure 8-9 Symptoms (Table 8.8): weakness, headaches, pallor, intolerance to cold, inability to pay attention, sometimes pica

Causes: • •

low intake, parasitic infections, daily blood loss. lose small amount Fe in nail clipping, hair trimmings, shed skin cells

Iron 

Iron toxicity •

Protected by:  low absorption  Intestinal cells trap some Fe and shed in feces

Iron overload: hemochromatosis (genetic disease, intestine absorbs excess Fe) • Symptoms: fatigue, mental depression, abdominal pain, tissue damage, liver failure • Acute poisoning: #1 cause of fatal accidental poisonings for children...