Water and minerals ch 8 and 10 11

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