Transcript
Water and Minerals
By weight, the human body is 50-70% water by weight Muscle tissue is about 73% water Fat tissue is about 20% water
Where is water found in the body? Intracellular fluid (inside cells) Extracellular fluid (outside cells)
Plasma (fluid of blood) Interstitial fluid (between and surrounding cells)
Water in the Body
Fig. 9.1
Solvent to host the body’s chemical reactions Temperature regulation
Water has a high heat capacity (resists change in temperature)
Cooling = perspiration 600 kcal of energy “lost” in 1 quart of sweat!
Body fluids Urine, joint lubricants, saliva, bile, amniotic fluid
Functions of Water
Sources and Loss of Water
Fig. 9.4
The AI for water (from food and beverage sources): Men: 15 cups/day Women: 11 cups/day
Fluid replacement critical during illness with fever, vomiting, diarrhea, sweating
During/after exercise, 2-3 cups of water for every pound lost
Hydration
Fig. 9.5
Basic metal elements that are essential to human health are minerals
Major minerals – need more of these Examples: calcium, sodium, potassium
Trace minerals – less required Examples: iron, zinc, fluoride
Minerals
What makes minerals more readily absorbed by the body: Growing conditions of crops impact the
amount of minerals in produce Fiber Oxalate (spinach, rhubarb) and phytate (whole
grains) Personal nutrient status Single mineral supplementation
Mineral Bioavailability
Electrolyte – influences fluid balance and water distribution in the body
40% of salt is sodium The numbers for sodium:
AI = 1500 mg/day UL = 2300 mg/day Average intake in the U.S. = 3000-6000 mg/day 1 tsp salt = 2000 mg
Sodium
Fig. 9.7
Fig 9.8
Sodium
Deficiency Caused by excessive
sweating, vomiting, diarrhea Illness Endurance sports
Toxicity Hypertension May lead to
dehydration May encourage
calcium loss in urine
Normal blood pressure: 120/80 mm Hg High blood pressure: 140/90 or above Many times, no specific cause Nearly ¼ of adults have hypertension, even
higher percentage of older adults Arteries become scarred and narrowed
More likely to develop atherosclerotic plaque
Hypertension
Therapy: Diet lower in sodium, low in fat, high in fruits
and vegetables, rich in calcium and potassium (DASH diet)
Control weight Regular exercise Reduce alcohol
Hypertension
Fig. 9.26
Electrolyte Other functions:
Muscle contraction Nerve transmission Control of blood pressure, heartbeat
Sources: Found in many foods, particularly fruits and
vegetables
Potassium
Potassium
Deficiency: May be caused by
vomiting, diarrhea May contribute to
high blood pressure Can cause some bone
loss, kidney stones Disrupted heartbeat Muscle cramps
Toxicity: May be caused by
kidney disease if kidneys do not filter out excess potassium
Rare from foods Can slow or stop
heart
Electrolyte Part of stomach acid (hydrochloric acid) Source: primarily salt added to foods
Chloride
99% of body calcium found in bones and teeth 1% in blood calcium
Crucial role in muscle contraction, nerve impulse transmission, blood clotting, blood pressure regulation
Blood calcium concentration tightly controlled at the expense of bone calcium
Blood tests may not indicate low calcium while bones may have significant calcium loss
Calcium
Bone remodeling occurs constantly Osteoblasts construct mineral crystals in bones Osteoclasts break down mineral crystals to be
released from bones When bones are stressed, they become more
dense (weight-bearing exercise)
Calcium
AI = 1000 mg/day for adults AI = 1200 mg/day if over 51 years old AI = 1300 mg/day if 9 to 18 years old Average intake: women 650 mg/day, men 900 mg/day Peak bone mass develops around age 30 Sources: dairy products, dark green leafy vegetables,
fish with bones (sardines), fortified soy and fruit juices and breakfast cereals
Lifestyle factors that increase urinary calcium excretion: Smoking and excess caffeine, protein, alcohol, sodium
Calcium
“Porous bone” Bones lose calcium, become
weak and brittle, may break with little pressure or a gentle fall
Older females at highest risk Adequate calcium intake during
teen years and twenties, along with weight-bearing exercise throughout the lifespan crucial to protect bone density
Osteoporosis
Essential oxygen-carrying part of hemoglobin Used by hundreds of enzymes as a cofactor Factors that affect iron absorption:
Heme sources – animal sources only (hemoglobin and myoglobin), best absorbed
Non-heme sources – plant, some animal sources Legumes, green leafy vegetables, whole
grains/enriched grains Vegetarians need to consume more iron to make up
for lower bioavailability Phytic acid and oxalic acid decrease iron absorption
Iron
Recommendations: Men and post-menopausal women: 8 mg/day Women of child-bearing age: 18 mg/day Pregnant women: 27 mg/day Average intakes: 17 mg/day for men, only 12
mg/day for women
Iron
One of the most common nutrient deficiencies worldwide
At risk: Children – may cause stunted growth, apathy,
irritability, learning disabilities Menstruating and pregnant women Vegetarians
Iron Deficiency
Iron-deficiency anemia – normal red blood cell production inhibited, leading to less oxygen-carrying capacity Other symptoms: fatigue, pale
appearance, poor tolerance to cool weather, immune system impairment, decreased ability to think and work
Iron Deficiency
Iron poisoning – most common cause poisoning death in children under 6 years old
Hemochomatosis – causes iron overload Genetic defect allows continued absorption of
iron past the body’s ability to store it safely Iron accumulates in tissues, leading to severe
organ damage High risk for heart disease, diabetes, liver
cirrhosis and cancer
Iron Toxicity
Cofactor for about 100 enzymes Helps “turn on” genes in DNA, leading to
protein production for growth Immune system function
Food sources: protein-rich foods, whole grains, peanuts, beans
Zinc
Deficiency: Rash, diarrhea, reduced sense of taste and
smell, hair loss, hindered growth in children Does zinc help prevent colds?
No strong evidence that colds are prevented by zinc if adequately nourished
Megadosing on zinc has a depressing effect on the immune system!
Zinc
70-80% is used in the thyroid gland to produce thyroid hormone Important in regulating metabolic rate,
promoting growth and development Deficiency:
Goiter – enlarged thyroid gland Cretinism
Source: most important is iodized salt
Iodine
Fluoride inhibits bacterial damage to tooth enamel, inhibiting tooth decay
Particularly important in infancy and childhood Sources: some natural or fluoridated water, tea,
seaweed Toothpaste, mouthwash
40-60% fewer dental caries Exposure to higher fluoride may lead to tooth
mottling
Fluoride
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