Water

Water’s Functions

• Carries nutrients and waste products

• Actively participates in chemical reactions

• Serves as a solvent for minerals, vitamins, amino acids glucose, and other small molecules

Water’s Functions

• Serves as a lubricant and cushion around joints

• Acts as a shock absorber(eyes, spinal column, amniotic sac)

• Aids in maintaining body’s temperature

Body’s Water Balance

• Water makes up about 60 % of the body’s weight

• A change in the body’s water can bring a change in the body weight– Sweating: water loss during exercise– Edema: water retention during

pregnancy

Water Balance

• Water loss necessitates water intake– Urine, sweat, exhalation, feces

• Dehydration can have serious consequences

RECOMMENDATIONS - 2004• No rule of thumb regarding # of

glasses– AI - 91 oz for women, 125 oz for men – Water, juice, milk, coffee, tea, soda,

fruits, vegetables and other foods and beverages

• Let thirst be your guide– Physical activity– Heat exposure

Figure 10.6  The consequence of a difference in osmotic pressure(a) A solute such as NaCl is more concentrated outside the cell than inside. (b) Water flows by osmosis out of the cell until the concentrations are equal. Neurons in certain brain areas detect their own dehydration and trigger thirst.

Water Recommendations and Sources• Hard water is high in calcium and

magnesium• Soft water is high in sodium

– It also dissolves cadmium and lead from pipes• If a person has lead pipes, this can be a

problem with long term use

Electrolytes

• Electrolytes (sodium, potassium, chloride) help keep fluids in the proper compartments– Intracellular water– Extracellular water

Electrolytes

•Enable nerves to respond•Signal muscles to contract

Primary electrolytes-major minerals• More than 0.1 grams (or 100 mg)

required per day in the diet• These include:

– Chloride– Phosphorus– Potassium– Sodium

Sodium: + ion of table salt (NaCl)• No known human diet lacks sodium• Minimum requirement about 500

mg/day– estimated safe and adequate Daily

intake

• Average intake in US for men = 3300 mg/day(equal to 8 grams of salt/day)

Calcium

• Roles:– 99% in bones and teeth– 1 %

• Cell membranes: regulates transport of ions into and out of cells

– Nerve to nerve transmission» Nerve to muscle transmission

• Helps hold cells together• Blood Clotting• Co-factor for several enzymes

Calcium: Blood Levels Highly Regulated: 4 ways• 1. Protein-bound Ca released to

become available for use by cells• 2. Increased Calcium absorption from

gut through activation of Vitamin D• 3.Increased Calcium released from

the bone through parathyroid hormone activation of Vitamin D

• 4. Kidneys conserve Calcium

Calcium RDA 1000-1200 mg/day for Adults• Foods rich in Calcium:

– 1 cup milk: 300 mg– 1 oz cheese: 200 mg– 1/2 cup spinach: 106 mg– 1 orange 52 mg– 1 cup Yogurt 350-400mg

(fat free or low fat)

Calcium Deficiency

• Rickets: in children. Same as Vitamin D deficiency– Bow legs, poor bone formation

• Osteomalacia: in adults. Same as Vitamin D deficiency– poor bone formation

• Osteoporosis: Multiple causes

Calcium and Osteoporosis

• Low Calcium intake• Poor Vitamin D status• female family history• small skeleton menopause• smoking high animal protein• drinking alcohol bed rest• white/Asian• Vitamin D improves symptoms of knee osteoarthritis

Trace Minerals: Micro minerals• One definition: less than 0.1

gram(100 mg/day) need in the diet– Some trace minerals:

• Iron (Fe)• Iodine(I)• Zinc(Zn)• Fluoride(F)

Iron

• Component of hemoglobin and myoglobin– hemoglobin carries oxygen in blood– myoglobin stores oxygen in muscle cells

• Deficiency:– RDA set at 18 mg/day for females and 8

mg/day for males– If iron stores exhausted, iron deficiency anemia

• microcytic, hypochromic anemia• reduced Hemoglobin synthesis, RBCs are small and

pink

Megaloblastic anemia

Iron Absorption

• Most iron we eat doesn’t get absorbed– What helps?

• vitamin C• MFP factor: some factor in meat, fish and

poultry helps absorb iron• need for iron

– What hurts absorption?• tea coffee• Calcium and Phosphorus• phytates and fiber and oxalates

Factors Affecting Iron Absorption• Increase• Gastric Acid• Heme iron• Demand• Low body stores• MPF• Vitamin C

• Decrease• Phytic Acid• Oxalic Acid• Polyphenols• Full body stores• Excess of other

min.• Reduced gastric

acid• Some antacids

Iron: Method of Absorption

• Iron in food– Absorbed into cells that line GI tract– If blood levels of iron are low

• iron picked up from cells by the blood and carried to places where RBCs are made

– If blood levels of iron are ok• iron stays in cells lining the GI tract

– In 3 to 5 days the cells are worn out and fall into the lumen of the GI tract and mix with the remains of digestion

Iron Overload

• 2 Types of Overload– 1. Hereditary Defect: Hemochromatosis

• Very efficient absorption• High circulating Fe which is laid down in

tissues of liver, heart and causes damage

– 2. High Iron ingestion: Hemosiderosis• Even with control of absorption, high intake

can result in toxic side effects• We don’t have a good mechanism of getting

rid of absorbed iron

Iron Sources

• 4 oz of lean roast = 3 mg• 4 oz liver = 7 mg• 1/2 cup beans = 4.15 mg• 1 cup broccoli = 1.12 mg• 1 slice mixed grain bread = 0.8 mg• 1 cup raisins = 3.12 mg

IronIron

Zinc

• Part of nearly 100 enzymes• Role in immune function• Absorption affected by zinc status,

phytates, iron• Hinders absorption of copper and

iron• Sources: red meats, eggs,

vegetables

Zinc Deficiency

• Growth delay• Altered digestive function• Impairs immune response• Vitamin deficiencies• Loss of appetite• Slow wound healing

Iron and Zinc Deficiency in School-age Children

0

20

40

60

80

Fe Zn Fe Zn Fe Zn Fe Znmales 6-11 males 12-19 females 6-11 females 12-19

%

Zinc

Selenium• Functions

– Antioxidant system– Thyroxine and immune function

• Deficiency– Keshan disease– Impaired immune response, cognitive

function, muscle pain, wasting– The Link between Selenium and

Chemoprevention: A Case for Selenoproteins -- Diwadkar-Navsariwala and Diamond 134 (11): 2899 -- Journal of Nutrition

Selenium – RDA 55 mg/day• Sources• Nuts• Seafood• Pasta

Fluoride

• Becomes part of crystalline deposits in bones and teeth– In teeth, resistant to tooth decay (dental

caries)– 1 part per million in water supply optimum

resistance– Higher than that can result in tooth mottling

• Brown coloration on teeth

– Much higher (18 ppm) can result in fluoridosis• Bone malformation

Copper

•Coenzyme–Part of ceruloplasmin

•Deficiency•Toxicity