Y khoa, dược - Chapter 8: Water & minerals: the ocean within

Chapter 8 Water & Minerals: The Ocean WithinWater: Crucial to LifeWater is the most essential nutrient45–75% body weightBody water2/3 Intracellular1/3 ExtracellularWater: Crucial to LifeElectrolytes and waterWhen minerals or salts dissolve in water  form ions:CationAnionsOsmosisIntake RecommendationsHow much water is enough?Men = 3.7 liters/day AIWomen = 2.7 liters/day AIPregnancy = 3.0 liters/day AILactation = 3.8 liters/dayIncreased needs for activity and sweatingIntake RecommendationsSources75-80% from Beverages20-25% from FoodsSmall amount from metabolic reactions (250-350mL/day)Water Excretion: Where Does the Water Go?Insensible water losses: the continuous loss of body water by evaporation from the lungs and diffusion through skin.¼- ½ of daily fluid lossUrine (~1-2 liters per day)Illness External factors that contribute to water losses:Low humidityHigh altitude High protein/salt foodsIntake RecommendationsWater BalanceBodies carefully maintain water balanceHormonal effects Antidiuretic hormone (ADH)AldosteroneThirstAlcohol, caffeine, and common medications affect fluid balanceWater Balance – How do kidneys know how to conserve water?Spinal cells in brain sense rising sodium levels in the body  signals pituitary gland to release ADH  signals kidneys to conserve water  water reabsorption dilutes sodium levelsSensors in the kidneys detect a drop in blood pressure  adrenal glands release aldosterone  kidneys retain sodium  water follows sodium  water reabsorptionWater BalanceAlcohol, caffeine, and common medications are usually diureticsAlcohol and caffeine are able to inhibit the release of ADH (by the pituitary gland)Too much alcohol/caffeine can lead to dehydrationIntake RecommendationsDehydrationEarly signs: Fatigue, headache, and dark urine with strong odorWater loss of 20% can cause coma and deathSeniors and infants especially vulnerableTreatment: water consumption (with electrolytes) or IV (moderate to severe cases)Water IntoxicationWater intoxication: Can occur in people who drink too much waterOver-hydration can also occur in people with untreated glandular disorders that cause excessive water retentionDeionized water (without minerals/electrolytes)Causes low blood sodium  headaches  seizures  coma  deathUnderstanding MineralsMineralsInorganicNot destroyed by heat, light, acidity, alkalinityMicronutrients (needed in small amounts)Grouped as:Major minerals (>100 mg/day)Trace minerals (<100 mg/day)Minerals in FoodsFound in plant (soil) and animal (diet) foodsFound in drinking water: sodium, magnesium, fluorideMineral absorption limited by several factors: GI tract Competing minerals (ex. megadose)High-fiber diet contain phytates (iron, zinc, manganese, calcium)Oxalate (calcium)Major Minerals and HealthMineral status significantly affects healthPlay critical parts in hypertension and osteoporosisSodiumFunctions:Fluid balance, blood pressure, and pHNerve impulse transmissionFood sourcesProcessed and convenience foodsAdded (table) saltSodiumDietary RecommendationsDaily intake less than 2,400 mg/dayDaily intake less than 1,500 mg/day desirableDealing with Excess SodiumCan contribute to hypertensionCan worsen dehydrationPotassiumFunctions:Muscle contractionNerve impulse transmissionRegulates blood pressure and heartbeatFood sources:People who eat low-sodium, high potassium diets often have lower blood pressureVegetables and fruits such as potatoes, spinach, melons, bananasMeat, poultry, fish, dairy products PotassiumDietary RecommendationsAI: 4,700 mg/dayDeficiencyLikely factor in hypertension riskCan disrupt acid-base balanceToxicityRareHigh levels can slow heartChlorideFunctions:Fluid balance (blood, sweat, tears)Hydrochloric Acid (stomach acid)Food sources:Table salt (NaCl – sodium chloride)Deficiency:Excessive vomiting (ex. Bulimia nervosa) CalciumFunctionsBone structureHydroxyapatiteBone cellsOsteoblastsOsteoclastsReserve of calcium and phosphorusCalciumFunctionsMuscles and metabolismFlow of calcium causes muscles to contract or relaxOther functionsBlood clottingNerve impulse transmissionCalciumRegulation of blood calcium levelsCalcitriol/Vitamin DParathyroid hormoneCalcitoninDietary RecommendationsRDA: 1,300 mg/day (children 9-18)RDA: 1,000 mg/day (men 19-70; women 19-50)RDA: 1,200 mg/day (men 70+; women 51+)CalciumRegulation of blood calcium levels by three hormones:To prevent dips in blood calcium levels, your body will demineralize boneIf low blood calcium levels  calcitriol increases intestinal absorption of calcium, and parathyroid hormone (PTH) activates osteoclasts to release bone calciumIf high blood calcium levels  thyroid glands release calcitonin to reduce blood calciumRegulation of Blood CalciumCalciumFood SourcesDairy products, green vegetables, processed and fortified foodsOxalate—binds calcium Calcium supplementation will not interfere with absorption of other minerals, but can interfere with absorption of some medicationsCalciumCalcium AbsorptionRelatively inefficientCalcium BalanceBone calcium used to maintain normal blood calcium levelsUL: 2,500 mg/day (adults 19-50)PhosphorusFunctionsBone structureComponent of ATP, DNA, RNA, and phospholipidsFood sourcesMeat, milk, and eggsProcessed foodsPhosphate balanceToo much phosphorus and too little calcium = increased bone lossMagnesiumFunctionParticipates in more than 300 types of enzyme-driven reactionsFood sourcesWhole grains, vegetables, legumes, tofu, seafood, and chocolateMagnesiumDeficiencyAssociated with alcoholismAlso associated with chronic illnessesRarely occurs on its ownSulfurFunctionPrimarily a component of organic nutrientsFood sourcesTypical diets contain ample sulfurDeficiency unknown in humansTrace MineralsCofactors for enzymesComponents of hormonesParticipate in many chemical reactionsEssential for growthEssential to the immune systemIronFunctionsOxygen transport as part of hemoglobin and myoglobinCofactor for enzymes, immune function, and normal brain functionIronIron AbsorptionEffect of Iron StatusAbsorption variesEffect of GI FunctionDepends on stomach acidEffect of the Amount and Form of Iron in FoodConserve ironHeme ironNon-heme ironIronIron absorptionDietary Factors Enhancing Iron AbsorptionVitamin CDietary Factors Inhibiting Iron AbsorptionPhytate, polyphenols, oxalates, high-fiber foods, calcium, and zincIronIron Transport and Storage Transferrin ferries iron through bloodMost iron stored as ferritin in bodySmaller amounts stored as hemosiderinIronIron Turnover and LossesRoutine destruction of old red blood cells releases ironRecycled iron used to build new red blood cellsDietary iron especially important in times of rapid growth and blood expansionLose iron in feces, sweat, skin cells, and menstruationDigestive disorders increase iron lossesIronFood sourcesRed meat, clam, oyster, liver, poultry, fish, pork, lamb, tofu, legumes, enriched and whole grains, fortified cerealIronDeficiencyMost common nutrient deficiencyMost severe stage: Iron-deficiency anemiaLack of iron inhibits red blood cell productionSymptoms include fatigue and pale skinIronToxicityAccidental iron overdose leading cause of poisoning deaths in young children in USGenetic defect: Hereditary hemochromatosisCauses excessive iron absorptionCauses chronic iron overloadCan lead to severe organ damage and chronic diseaseZincFunctionsServes as cofactor for major enzymes Helps fold proteins into functional shapesHelps control diverse functions, including gene expression, cell death, and nerve transmissionZincEnzymesHelps provide structural integrity or activate catalytic abilityGene regulation Enables proteins to fold into a special form that interacts with DNAImmune systemVital to fighting infectionZincRegulation of Zinc in the BodyAbsorptionSimilar to ironOnly about 10-35% of zinc absorbedPhytate inhibits absorptionTransport, distribution, and excretionCirculates bound to proteinZincFood sourcesRed meats, seafoodZincDeficiencyUncommon but may occur in people with illnesses that impair absorptionPoor growth and delayed developmentToxicityChronic doses may induce copper deficiencySeleniumFunctionsPart of antioxidant enzymeThyroid metabolism and immune functionAbsorption and ExcretionBound to AAVitamins A, C, E enhancePhytates inhibitSeleniumFood sourcesOrgan meats, fish, seafood, meats, Brazil nutsDeficiencyIncreases susceptibility to some infectionsToxicityBrittle hair and nailsIodineFunctionsThyroid hormone productionFood sourcesIodized salt, fish, seafood, dairy productsIodineDeficiencyGoiter: enlarged thyroid glandCretinism: mental retardationOccurs in fetus when pregnant woman is deficientToxicityGoiterCopperFunctionsMelanin, collagen, and elastin productionImmune functionAntioxidant enzyme systemsAbsorption and StorageVaries from 20% to 50%CopperFood SourcesOrgan meats, shellfish, nuts, and legumesDeficiencyCauses anemia and poor immune functionToxicityRelatively nontoxicManganeseFunctionsCartilage productionAntioxidant enzyme systemsFood SourcesTea, nuts, cerealsManganeseDeficiencySome illnesses may cause suboptimal Mg statusToxicityIncidents due to air pollutantsFluorideFunctions Bone and tooth structureFood sourcesFluoridated waterBalanceExcess can cause fluorosisThe fluoridation debateChromiumFunctions Glucose metabolismFood sourcesMushrooms, dark chocolate, nuts, whole grainsDeficiency and toxicityDifficult to determine deficiencyNo ULMolybdenumFunctionsEnzyme cofactorFood sourcesPeas, beans, some breakfast cereals, and organ meatsOther Trace Minerals and Ultratrace MineralsArsenicBoronNickelSiliconVanadium