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Water makes up ≈60% of an adult’s body weight Water is found in ◦ Blood vessels ◦ Cells ◦ Chemical structure of cells, tissues, organs Water participates in many chemical reactions Delivers nutrients and removes waste from cells Water is a, nearly, universal solvent Water is the body’s cleansing agent Water’s incompressibility Water plays a role in thermoregulation Water balance ◦ Water intake needs to equal water loss Dehydration ◦ Water loss ◦ Progression of symptoms: thirst weakness exhaustion and delirium death Water intoxication ◦ Dangerous dilution of body fluids resulting from excessive water ingestion ◦ Symptoms: headache, muscular weakness, lack of concentration, poor memory, loss of appetite A disturbed fluid balance can cause a severe illness ◦ In vomiting or diarrhea Result: fluid and electrolyte imbalance Life-threatening disruption of heartbeat ◦ Minerals also play a role in acid-base balance In pure water H+ and OH- ions exist in equilibrium When dissolved in water The maintenance of a nearly constant pH is critical to life ◦ Slight changes in pH can change the structure and function of most biologically important molecules 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 consumed foods ◦ Body produces water from the breakdown of energy-yielding nutrients Minerals ◦ ◦ ◦ ◦ Naturally occurring Inorganic Homogenous Chemical elements Major minerals ◦ Essential nutrients ◦ Found in the body in amounts exceeding 5 grams Trace minerals ◦ Essential nutrients ◦ Found in the body in amounts less than 5 grams Role: Most abundant mineral in the body ◦ ≈99% stored in bone and teeth ◦ Calcium & phosphorous for bone formation Calcium phosphate salt forms hydroxyapatite crystals to add rigidity to bone Integral part of bone structure & building Bone serves as a calcium reserve, releasing or removing calcium from the blood ◦ Essential for muscle contraction and therefore heartbeat ◦ Allows secretion of hormones, digestive enzymes, and neurotransmitters ◦ Activates cellular enzymes that regulate many processes Despite adjustments, some bone loss in an inevitable consequence of aging ◦ By the late 20s, or 10 years after adult height is reached, skeleton no longer adds to bone density ◦ After ≈40 years of age, regardless of calcium intake, bones begin to reduce density Loss can be slowed by a diet high in calcium along with sufficient physical activity Low intakes of calcium are associated with an increased risk of colon and rectal cancer as compared to higher calcium intakes To protect against bone loss, high calcium intakes early in life are recommended ◦ A calcium-poor diet during the growing years may prevent a person from achieving peak bone mass ◦ Insufficient bone calcium increases the risk of osteoporosis (adult bone loss) How Much Calcium Do I Need? ◦ Setting recommended intakes is difficult ◦ Absorption varies with: age, vitamin D status, dietary calcium intake Recommended intakes are high for children and adolescents along with Vitamin D ◦ People develop their peak bone mass during their growing years ◦ Average intakes among growing individuals are too low to meet recommendations © 2006 Thomson-Wadsworth Calcium consumption Average woman consumes 1/3 of RDA Average man consumes ~3/4 of RDA Deficiency ◦ Associated with all sorts of major illnesses including Adult bone loss High blood pressure Kidney stones ◦ Consumption of milk, one of the best sources of calcium, has declined While the consumption of beverages such as soft drinks has dramatically increased Milk, Yogurt, and Cheese Group ◦ Children who don’t drink milk often have lower calcium intakes and poorer bone health than those who drink milk regularly ◦ People with lactose intolerance, dislike, or allergy can obtain calcium from other sources Other non-milk choices Yogurt Kefir Buttermilk Cheese--Especially low-fat or fat-free varieties Vegetables: Dark greens of all kinds ◦ Superb sources of riboflavin ◦ Indispensable for the vegan or anyone else who does not drink milk ◦ Good sources of calcium Rutabaga, Broccoli, Beet and collard greens, Turnip greens, Bok Choy & Kale EXCEPTIONS: Spinach, Swiss chard, rhubarb ◦ Equal to milk in calcium content ◦ Provide little to the body because they contain binders that prevent calcium absorption Causes of Osteoporosis Gender Advanced age Genetics Environmental factors Environmental factors Poor nutrition Involving calcium and vitamin D Estrogen deficiency in women Lack of physical activity Being underweight Use of tobacco and alcohol Possibly: excess protein, sodium, caffeine, soft drinks Inadequate vitamin K intake © 2006 Thomson-Wadsworth Second most abundant mineral in the body Role ≈85% in the crystals of the bone and teeth Maintain the acid-base balance of cellular fluids Part of DNA and RNA Phosphorus compounds carry, store, and release energy in the metabolism of energy nutrients ◦ Phosphorous compounds assist many enzymes and vitamins extracting the energy from nutrients ◦ Forms part of phospholipids ◦ Present in some proteins ◦ ◦ ◦ ◦ Barely qualifies as a major mineral ◦ Only ≈1 ounce in the body of a 135-pound person Over half in the bones The rest in muscles, heart, liver, other soft tissues Only 1% in body fluids Critical to many cell functions: 300+ enzymes Release and use of energy from nutrients Directly affects the metabolism of K+, Ca++ & Vit D Acts in the cells of all soft tissue Needed for the proper functioning of muscles Promotes resistance to tooth decay by holding calcium in tooth enamel Needs and deficiency ◦ Needs are easily met by almost any diet Therefore, deficiencies are unknown Source ◦ Animal protein is the best source Deficiency ◦ May occur as a result of Inadequate intake Vomiting & Diarrhea Alcoholism & Protein malnutrition Diuretic use Deficiency symptoms ◦ Causes hallucinations ◦ Overt deficiency symptoms are rare in normal, healthy people Low intake is common ◦ Most Americans receive only ≈75% of the recommended magnesium from their diets Sources Easily washed and peeled away from foods during processing In some parts of the country, water contributes significantly to magnesium intake Toxicity Rare but can be fatal Only occurs with high intakes from: Supplements or magnesium salts Accidental poisonings Toxicity symptoms Severe diarrhea Acid-base imbalance Dehydration Positive ion in sodium chloride (table salt) ◦ 40% of the weight of sodium chloride Role ◦ ◦ ◦ ◦ ◦ ◦ Fluid balance Electrolyte balance Maintenance of extracellular fluid balance Acid-base balance Muscle contraction Nerve transmission Deficiency ◦ No known human diets lack sodium Most foods include more salt than is needed ◦ Body absorbs sodium freely ◦ Kidneys filter excess sodium out of the blood into the urine ◦ Kidneys will also conserve sodium ◦ Small sodium losses occur in sweat ◦ The amount of sodium excreted in a day equals the amount ingested that day © 2006 Thomson-Wadsworth Sodium Intakes ◦ Adults in the U.S. exceed the Tolerable Upper Intake Level by more than a third ◦ Asian peoples, whose staple sauces and flavorings are based on soy sauce and MSG, may consume the equivalent of 30 to 40 grams of salt per day A dietary that may help salt-sensitive and non-salt-sensitive people is the DASH diet ◦ This diet often achieves a lower blood pressure than restriction of sodium alone DASH diet ◦ Greatly increased intake of fruits and vegetables ◦ Adequate amounts of nuts, fish, whole grains, low-fat dairy products ◦ Occasional small portions of red meat, butter, and other high-fat foods and sweets ◦ Import role of potassium as a sodium antagonist Other reasons for reducing salt intake ◦ Older people without clinical hypertension often die of stroke Reducing dietary sodium may lower their blood pressure enough to reduce stroke risks ◦ Excess dietary sodium increases calcium excretion This may compromise the integrity of the bones ◦ Excessive salt may stress a weakened heart, aggravate kidney problems, may be a cause of stomach cancer The principal positively charged ion inside the body’s cells Role ◦ ◦ ◦ ◦ Maintenance Maintenance Maintenance Maintenance of of of of fluid balance electrolyte balance cell integrity heartbeat Deficiency ◦ Sudden deaths occur during fasting or severe diarrhea due to heart failure caused by potassium loss ◦ Dehydration leads to a loss of potassium from inside cells When cells of the brain lose potassium, the brain loses the ability to notice the need for water With low potassium intake ◦ ◦ ◦ ◦ ◦ Salt-sensitive hypertension becomes worse Glucose tolerance is impaired Metabolic acidity increases Calcium losses from bones accelerates Kidney stone risk increases ◦ **In healthy people, any reasonable diet provides enough potassium to prevent dangerously low blood potassium Toxicity ◦ Potassium from food is safe ◦ Potassium injected into a vein can stop the heart ◦ Over-the-counter potassium chloride pills should not be used except on a physician’s advice Even though they are sold without a warning label Major negative ion in the body Role ◦ ◦ ◦ ◦ Accompanies sodium in fluids outside cells Acid-base balance Electrolyte balance Component of hydrochloric acid Source ◦ Salt Both added and naturally occurring Deficiency ◦ No known diet lacks chloride Role ◦ Required for the synthesis of many important sulfur-containing compounds Certain antioxidants Thiamin Sulfur-containing amino acids Deficiencies ◦ Unknown Toxicity ◦ From too much sulfate in water, either naturally occurring or from contamination ◦ Diarrhea ◦ Colon damage Difficult to determine the precise roles of trace elements Intake recommendations have been established for nine trace minerals Role ◦ Component of thyroxine Manufactured by the thyroid gland that is responsible for the regulation of basal metabolic rate Sources ◦ Amount in food varies with amount in soil in which plants are grown or on which animals graze ◦ Seafood Iodine is plentiful in the ocean; sea salt, very little ◦ Iodized salt: <half-teaspoon meets RDA ◦ Use of iodized salt in fast-food andrestaurant ◦ Bakery products & Milk Deficiency ◦ Enlarged thyroid (goiter) ◦ Sluggishness ◦ Weight gain © 2006 Thomson-Wadsworth Severe deficiency during pregnancy ◦ Cretinism Extreme irreversible mental and physical retardation Can be averted if the woman’s deficiency can be detected and treated within the first six months of pregnancy ◦ Iodine deficiency is one of the most treatable and preventable causes of mental retardation Potassium iodide ◦ Effectively blocks damage to the thyroid gland caused by radioactive iodine from nuclear emergencies ◦ Given at the right time and at the right dosage potassium iodide will greatly reduce the risk of thyroid cancer ◦ Given at the wrong dosage or at the wrong time, potassium iodide is useless or toxic Most of the iron in the body is a component of either hemoglobin or myoglobin ◦ Hemoglobin is the oxygen-carrying protein RBCs ◦ Myoglobin is the oxygen-holding muscle protein Body cells combine oxygen with the carbon and hydrogen they release as they break down nutrients ◦ Therefore, the body needs a continuous supply of oxygen Red blood cells supply this oxygen Additional roles of iron ◦ Helps many enzymes use oxygen ◦ Needed to make New cells Amino acids Hormones Neurotransmitters What Happens to a Person Who Lacks Iron? ◦ Iron deficiency Result of absorption not compensating for losses or low dietary intakes Iron deficiency anemia ◦ Often occurs with iron deficiency ◦ A person can be iron deficient without being anemic ◦ Anemia refers to depletion of iron stores resulting in low blood hemoglobin Severe iron deprivation insufficient hemoglobin production to fill new blood cells anemia (cells are smaller and lighter red than normal) ◦ Cells contain too little hemoglobin and thus deliver too little oxygen limits cell’s energy metabolism tiredness, apathy, a tendency to feel cold Fatigue and can impair physical work capacity and productivity Causes of Iron Deficiency and Anemia ◦ Women are at greater risk of an iron deficiency than men Need more iron On average, eat less food ◦ Infants over 6 months of age, young children, adolescents, menstruating and pregnant women have increased iron needs To support growth of new tissue and/or to replace iron loss Most common nutrient deficiency(1.2B people) Parasitic infections cause people to lose blood daily In digestive tract, ulcers, sores, and inflammation can cause sufficient blood loss to cause anemia In developing countries, ~1/2 of preschool children & pregnant women suffer iron-deficiency anemia In the US ~10% of toddlers, adolescent girls & women of childbearing age ◦ The iron status of U.S. infants and young children has improved over the last decade Increased breastfeeding, which promotes iron absorption & iron-fortified infant formula /cereals WIC provides coupons redeemable for foods high in iron © 2006 Thomson-Wadsworth Can a Person Take In Too Much Iron? ◦ Iron is toxic in large amounts ◦ Once absorbed it is difficult to excrete ◦ The body defends against iron overload (hemochromatosis) by controlling its entry Intestinal cells trap some of the iron and hold it within their boundaries; when these cells are shed the excess iron they collected is lost from the body When iron stores fill up, less iron is absorbed ◦ The danger of iron overload is an argument against high-level iron fortification of foods Iron supplements can reverse iron-deficiency anemia from dietary causes ◦ May create oxidative reaction in the digestive tract that may damage its linings Especially in those suffering with inflammation of these tissues ◦ Iron supplements are a leading cause of fatal accidental poisonings among U.S. children under 6 years old © 2006 Thomson-Wadsworth © 2006 Thomson-Wadsworth Iron Recommendations and Sources ◦ Adult men rarely experience iron-deficiency anemia If a man has a low hemoglobin concentration, his health-care provider should examine him for a bloodloss site Iron Recommendations and Sources ◦ Vegetarians, because the iron in their foods is not well absorbed and because their diets lack factors from meat that enhance iron absorption, are advised to obtain 1.8 times the normal requirement ◦ To meet iron needs, is best to rely on foods Iron from supplements is much less well absorbed than iron from food The usual Western diet provides only about 5 to 6 mg iron/1,000 calories ◦ For an adult male this does not pose a problem ◦ A female who eats fewer calories and needs more iron needs to select high-iron, low-calorie foods from each food group ◦ Pregnant women need an iron supplement ◦ Iron supplements should only be taken when recommended by a physician Absorbing Iron ◦ Iron occurs in two forms in foods Some is bound into heme The iron-containing part of hemoglobin and myoglobin in meat, poultry and fish Some is nonheme iron Found in foods from plants and in nonheme iron of meats Absorbing Iron ◦ Heme iron is more reliably absorbed than nonheme iron Healthy people with adequate iron stores absorb heme iron at a rate of ≈23% People absorb nonheme iron at rates of 2%-20% Depending on dietary factors and iron stores Absorbing Iron (continued) ◦ MFP factor Found in meat, fish and poultry Promotes the absorption of nonheme iron from other foods eaten at the same time ◦ Vitamin C can triple absorption of nonheme iron from foods eaten in the same meal Impairment of iron absorption Tannins Found in tea and coffee Calcium and phosphorus Milk Phytates Found in the fiber of lightly processed legumes and wholegrain cereals Impairment of iron absorption (continued) ◦ Black tea is exceptional in reducing iron absorption ◦ Clinical dieticians advise people with iron overload to drink it with their meals The amount of iron absorbed from a meal depends partly on the interaction between promoters and inhibitors of iron absorption Cooking in an iron pan adds iron to food ◦ This iron is in the form of iron salts somewhat like those in supplements ◦ The iron content of 100 grams of spaghetti sauce Simmered in a glass dish = 3mg Cooked in a black iron skillet = 87mg Role ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ ◦ Helps nearly 100 enzymes Regulation of gene expression in protein synthesis Affects behavior and learning Assists in immune function Wound healing Sperm production Taste perception Fetal development Growth and development in children Produces the active form of vitamin A Even a mild deficiency can result in: ◦ Impaired immunity ◦ Abnormal taste ◦ Abnormal vision in the dark Problem: Too Little Zinc ◦ First reported in the 1960s from studies of growing and adolescent boys in the Middle East Diets were low in animal protein and high in whole grains and beans The breads were not leavened In leavened bread, yeast breaks down phytates as the bread rises Deficiency symptoms ◦ Adverse affects on growth ◦ Profoundly alters digestive function And causes diarrhea, which worsens the malnutrition already present with regard to all nutrients ◦ Drastically impairs the immune response Making infections likely ◦ Infections of the intestinal tract worsen malnutrition Including zinc malnutrition ◦ Zinc deficiency disturbs thyroid function Symptoms are so pervasive that when confronted with zinc deficiency, a physician is more likely to diagnose it as general malnutrition and sickness Severe zinc deficiencies are not widespread in developed countries ◦ At risk: Pregnant women Young children Elderly Poor Problem: Too Much Zinc ◦ Toxic in large quantities In high enough doses, supplements can cause serious illness or death Over time, regular doses a few milligrams above the recommended intake can block copper absorption and lower the body’s copper content ◦ In animal studies, this has lead to degeneration of heart muscle In high doses ◦ May reduce blood concentrations of HDLs High doses can also inhibit iron absorption A protein that carries iron from the digestive tract to tissues also carries zinc ◦ If there is excess zinc, there is little room left for this protein to pick up iron from the digestive tract ◦ If there is too much iron, there is little room for this protein to pick up zinc from the digestive tract Thus impairing zinc absorption Zinc and iron are are often found together in foods ◦ Food sources never cause imbalances in the body ◦ Zinc from lozenges and spray, sold for the treatment of the common cold, may or may not provide the intended relief But contributes supplemental zinc to the body ◦ Unlike iron, excess zinc has a normal escape route from the body Food Sources of Zinc ◦ Major sources Meats Shellfish Poultry ◦ Plant sources of zinc are not absorbed as well as animal sources Some legumes Whole grains Most people meet the recommended intake levels ◦ Men: 11 mg/day ◦ Women: 8 mg/day Vegetarians are advised to eat a varied diet that includes whole-grain breads well leavened with yeast ◦ Leavening helps make the zinc available for absorption Role ◦ Protects vulnerable body chemicals against oxidative destruction Assists a group of enzymes that, in concert with vitamin E, work to prevent the formation of free radicals and prevent oxidative harm to cells and tissues ◦ Plays roles in activating thyroid hormone ◦ Low blood selenium correlates with the development of some forms of cancer Especially prostate cancer Low intake and Deficiency Prostate cancer ◦ 4th leading cancer in men worldwide Black men in the U.S. suffer the highest rates of all ◦ Men with adequate selenium in their blood have a lower incidence of prostate cancer than men whose blood measures are low Heart disease ◦ A type first identified in China among people from areas with selenium-deficient soils Sources ◦ No need to worry about a selenium deficiency if you eat a normal diet composed of unprocessed foods ◦ Widely distributed in foods such as Meats Shellfish Vegetables and grains grown in selenium-rich soils Toxicity ◦ Long-term supplementation ◦ UL: 400 micrograms/day Not essential: only trace amounts in human body Role ◦ Crystalline deposits in bone and teeth Forms more decay-resistant fluorapatite in developing teeth ◦ Helps prevent dental caries Sources ◦ Primary source: fluoridated drinking water 65+% of U.S. population has access to water with optimal fluoride concentration Such water typically delivers ≈1 mg/day (≈1 part per million) Rarely present in bottled water Unless it was added at the source As in bottled municipal tap water Deficiency ◦ Where fluoride is missing, the incidence of dental decay is very high Fluoridation of water is recommended for public dental health ◦ Fluoridation is a practical, safe, and cost-effective way to help prevent dental caries in the young ◦ Sufficient fluoride during the tooth-forming years of infancy and childhood gives lifetime protection against tooth decay Percent of population in each state with access to fluoridated water © 2006 Thomson-Wadsworth Toxicity ◦ Discoloration of teeth (fluorosis) may occur Occurs only during tooth development, never after teeth have formed. Irreversible ◦ Widespread availability of fluoridated toothpaste and mouthwash, foods made with fluoridated water, and fluoride-containing supplements Mildest form of fluorosis Characteristic white spots form in the tooth enamel ◦ No evidence connecting fluoridation of with cancer Role ◦ Works closely with insulin to regulate and release energy from glucose Deficiency ◦ Impaired insulin action Resulting a a diabetes-like condition of high blood glucose Resolves with chromium supplementation ◦ Supplements cannot cure the common forms of diabetes Chromium supplements ◦ Will not build extra muscle mass or melt off fat ◦ Does not lower blood cholesterol ◦ Diets high in simple sugars and low in whole, nutrient-dense foods deplete the body’s supply of chromium ◦ Becomes more common as people become more dependent on heavily refined foods Toxicity ◦ Chromium compounds used in various industrial processes are known carcinogens The form found in foods and supplements is nontoxic by comparison Amount up to 200 micrograms/day seems to be safe ◦ Supplementation may cause skin eruptions Source ◦ Widely distributed in the food supply Especially in unrefined foods and whole grains Lost during food processing ◦ Exists in foods in complexes with other compounds that make it easily controlled and used by the body These chromium-containing compounds are termed biologically active chromium or glucose tolerance factor Source ◦ Widely distributed in the food supply Especially in unrefined foods and whole grains Lost during food processing Best chromium sources ◦ ◦ ◦ ◦ Liver Whole grains Nuts Cheeses