•Water and Minerals
Chapter 6
•Water
•Functions of water
–Occupies essentially every space within and between body cells
–Involved in virtually every body function
–Largest single constituent of the human body, averaging 60% of total body weight
–Provides shape and structure to cells
–Regulates body temperature
–Aids in the digestion and absorption of nutrients
•Water (cont’d)
•Functions of water (cont’d)
–Transports nutrients and oxygen to cells
–Serves as a solvent for vitamins, minerals, glucose, and amino acids
–Participates in metabolic reactions
–Eliminates waste products
–Is a major component of mucus and other lubricating fluids
•Water (cont’d)
•Water balance
–Total body water balance is tightly regulated within +/- 0.2% of body weight
–Sensation of thirst and the action of the hormone vasopressin control our daily fluid balance
oWater output
Adults lose approximately 1,750 to 3,000 mL of water daily
Insensible water losses
–Water (cont’d)
•Water balance (cont’d)
•Water output (cont’d)
–Sensible water losses
•Water intake
– Drinking water
–Other beverages
–Solid foods
•Water (cont’d)
•Water recommendations
–Body cannot produce as much water as it needs
–For men ages 19 to over 70, the adequate intake (AI) is 3.7 L/day
–For women of the same age, the AI is 2.7 L/day
–Daily intakes below the AI may not be harmful to healthy people
–Water (cont’d)
•Water recommendations (cont’d)
–Osmoregulatory system
–Fluid intake is assumed to be adequate when the color of urine produced is pale yellow
–Elderly and children
oDrinking fluids should not be delayed until the sensation of thirst occurs
–Water (cont’d)
•Water recommendations (cont’d)
–Increases in water loss
oVomiting, diarrhea, and fever
oThermal injuries, fistulas, uncontrolled diabetes, hemorrhage, and certain renal disorders
oUse of drainage tubes contributes to increased water losses
oIntake and output records are used to assess adequacy of intake
•Water (cont’d)
•Alterations in intake
–Dehydration is characterized by:
oImpaired mental function
oImpaired motor control
oIncreased body temperature during exercise
oIncreased resting heart rate when standing or lying down
oIncreased risk of life-threatening heat stroke
oWater (cont’d)
•Alterations in intake (cont’d)
–A net water loss of as little as 1% of body weight increases plasma osmolality
–A loss of 20% can be life-threatening
•Hyponatremia
–At risk patients include infants; psychiatric patients with excessive thirst; women who have undergone surgery using a uterine distention medium; and athletes in endurance events who drink too much water or fail to replace lost sodium, or both
•Water (cont’d)
•Hyponatremia (cont’d)
–Symptoms
oLung congestion, muscle weakness, lethargy, and confusion
oCan progress to convulsions, prolonged coma, and death
•Question
•Insensible water losses are those that cannot be measured. Insensible water losses occur through what?
a. Urine
b. Feces
c. Respirations
d. Diaphoresis
•Answer
c. Respirations
Rationale: Extreme environmental temperatures (very hot or very cold), high altitude, low humidity, and strenuous exercise increase insensible water losses from respirations and the skin.
•Keys to Understanding Minerals
•Major minerals are present in the body in amounts greater than 5 g
•Calcium, phosphorus, magnesium, sulfur, sodium, potassium, and chloride are major minerals
•Iron, iodine, zinc, selenium, copper, manganese, fluoride, chromium, and molybdenum are classified as trace minerals or trace elements
•Both groups are essential for life
•Keys to Understanding Minerals (cont’d)
•General chemistry
–Minerals are inorganic elements that originate from the earth’s crust, not from plants or animals
–Minerals do not undergo digestion, nor are they broken down or rearranged during metabolism
–Minerals are not destroyed by light, air, heat, or acids during food preparation
•Keys to Understanding Minerals (cont’d)
•General functions
–Minerals function to provide structure to body tissues and to regulate body processes
•Mineral balance
–Maintained by:
oReleasing minerals from storage for redistribution
oAltering rate of absorption
oAltering rate of excretion
•Keys to Understanding Minerals (cont’d)
•Mineral toxicities
–Stored minerals can produce toxicity symptoms
–Toxicity related to excessive use of mineral supplements, environmental or industrial exposure, human errors in commercial food processing, or alterations in metabolism
•Mineral interactions
–Mineral status must be viewed as a function of the total diet
•Keys to Understanding Minerals (cont’d)
•Sources of minerals
–Unrefined or unprocessed foods have more minerals than refined foods
•Major electrolytes
–Sodium
oSalt (sodium chloride) is approximately 40% sodium
oWide variations in sodium intake exist between cultures and between individuals within a culture
–Keys to Understanding Minerals (cont’d)
•Major electrolytes (cont’d)
–Sodium (cont.)
oMajor extracellular cation
oLargely responsible for regulating fluid balance
oAlmost 98% of all sodium consumed is absorbed
oAdequate intake for sodium is set at 1,500 mg/ day
o100% of adult men and women exceed the AI of 1,500 mg of sodium/day
–Keys to Understanding Minerals (cont’d)
–Potassium
oMajor cation of the intracellular fluid
oWhen potassium excretion is impaired, such as secondary to diabetes, chronic renal insufficiency, end- stage renal disease, severe heart failure, and adrenal insufficiency, high potassium intakes can lead to hyperkalemia and life-threatening cardiac arrhythmias
–Chloride
oMajor anion in the extracellular fluid
oAI for younger adults is 2.3 g/day
•Question
•Is the following statement true or false?
Potassium is the major extracellular cation.
•Answer
False.
Rationale: Most of the body’s potassium is located in the cells as the major cation of the intracellular fluid.
•Major Minerals
•Calcium
–Most plentiful mineral in the body
–Probably protects against colorectal cancer
–Calcium balance in the blood is achieved through the action of vitamin D and hormones
–3 daily servings of milk, yogurt, or cheese plus nondairy sources of calcium are needed to ensure an adequate calcium intake
–An adequate calcium intake throughout the first 3 decades of life is needed to attain peak bone mass as determined by genetics
•Major Minerals (cont’d)
•Phosphorus
–After calcium, the most abundant mineral in the body is phosphorus
–About 60% of natural phosphorus from food sources is absorbed
–Dietary deficiencies of phosphorus do not occur
•Magnesium
–4th most abundant mineral in the body
–Mean magnesium intake among American adults is approximately 80% of the RDA
•Major Minerals (cont’d)
•Sulfur
–Does not function independently as a nutrient but is a component of biotin, thiamin, and the amino acids methionine and cysteine
–There is no RDA or AI for sulfur
•Trace Minerals
•Impact on health is significant
•Too little of a trace mineral can be just as deadly as too much
•Iron
–Approximately two-thirds of the body’s 3 to 5 g of iron is contained in the heme portion of hemoglobin
–Iron in foods exists in two forms: heme iron found in meat, fish, and poultry, and nonheme iron found in plants such as grains, vegetables, legumes, and nuts
–Overall rate of iron absorption is only 10% to 15% of total intake
•Trace Minerals (cont’d)
•Iron (cont’d)
–Only 1% to 7% of nonheme iron is absorbed from plant foods when they are consumed as a single food
–RDA for iron is set at 8 mg for men and postmenopausal women, and at 18 mg for premenopausal women
–Iron deficiency anemia
oMicrocytic, hypochromic anemia
oPica
•Trace Minerals (cont’d)
•Iron (cont’d)
–Potential for toxicity is moderate to high
–Hemochromatosis
–Acute iron toxicity
•Zinc
–A regular and sufficient intake is necessary
–Plays important roles in immune system functioning and in wound healing
•Trace Minerals (cont’d)
•Iodine
–Essential component of thyroxine (T4) and triiodothyronine (T3)
–Approximately 50% of the population uses iodized salt
–Goitrogens
•Selenium
–A component of a group of enzymes that function as antioxidants
–Selenium deficiency is rare in the United States
•Trace Minerals (cont’d)
•Copper
–Distributed in muscles, liver, brain, bones, kidneys, and blood
–Involved in hemoglobin synthesis, collagen formation, wound healing, and maintenance of nerve fibers
•Manganese
–Dietary deficiencies have not been noted
–High manganese intake from drinking water also produces neuromotor deficits similar to Parkinson’s disease
•Trace Minerals (cont’d)
•Fluoride
–Promotes the mineralization of developing tooth enamel prior to tooth eruption and the remineralization of surface enamel in erupted teeth
–Fluoridation of municipal water
•Chromium
–Enhances the action of the hormone insulin to help regulate blood glucose levels
–Appears that average intake is adequate
•Trace Minerals (cont’d)
•Molybdenum
–Plays a role in red blood cell synthesis
–Dietary deficiencies and toxicities are unknown
•Other trace elements
–Evidence is difficult to obtain and quantifying human need is even more formidable
•Question
•Which major mineral is the most abundant in the human body?
a. Manganese
b. Selenium
c. Calcium
d. Sodium
•Answer
c. Calcium
Rationale: Calcium is the most plentiful mineral in the body, making up about half of the body’s total mineral content.
•Water and Minerals in Health Promotion
•Water
–Recommended that thirst be the guide to consuming adequate fluid; specific amounts or types of beverages to satisfy fluid need are not suggested
–For healthy people, hydration is unconsciously maintained with ad libitum access to water
•Sodium and potassium
–Recommendations:
oLess sodium
oMore potassium