chapter 12: water and the major minerals - nutrition

water functions

• carries nutrients and waste

• maintains structure of large molecules

• metabolic reactions

• solvent

• lubricant and cushion

• regulate body temp

• blood volume

fluid functions

• maintain BV and pressure

• regulated by the kidneys: adjust urine volume and concentration

• ADH: water conservation — released when hypothalamus stims pituitary gland

raa system

low BV and bp → kidneys release renin → reaction with angiotensinogen → angiotensin I → ACE → angiotensin II → increase BV and bp

angiotensin II

• → constricts blood vessels

• → ADH: retains water and Na, excretes K

• → aldosterone: retains water and Na, excretes K

• occurs across kidneys, liver, lungs, and adrenal glands

water balance

sources: beverages, foods (up to 1000 mL), metabolism

losses: kidneys (urine, up to 1400 mL), skin (sweat, up to 900 mL), lungs (breath), GI tract (feces)

• 7-10% of body weight lost due to dehydration causes collapse

adequate intake: 2-3 L (8-12 cups)

• who needs it more: exercise, hot env, men, pregnant women

sodium and chloride

extracellular electrolytes essential for maintaining fluid balance and nerve conduction

• primary regulator of volume: NA outside of cell, water follows sodium, increasing Na and increasing BV/bp

• works with K for action potentials and muscle function

• aldosterone and ADH

• chloride is part of HCl in stomach: to breakdown food and activate digestive enzymes

• high Na → increase Ca2+ LOST in urine → bone loss/kidney stones

  • K helps reduce calcium lost

• food sources: NOT processed foods — high in Na, low in K (ex: fast food, frozen meals) — contrast with fresh fruits and veggies

  • DASH diet: mostly fruits, veggies, and grains to decrease Na

  • americans consume 2-3x the RDA (2300 mg/day)

potassium

intracellular mineral that helps maintain a healthy blood pressure by promoting vasodilation (decreasing bp)

• aids in nerve impulse and muscle contraction — exits and repolarizes

• high intake = protective — for kidneys to dump Na and increase local blood flow

• food sources: potatoes, leafy greens, beans, bananas, whole foods

• adequate intake: 4700 mg/day

calcium

most abundant mineral, making up 99% in bones and teeth, and remaining 1% in blood

• early life needs (teens): build peak bone mass

• later life: prevent bone loss (osteoporosis) - low intake — body pulls from bones and they weaken

• bone “bank”: decrease levels in blood causes bone breakdown to release it

• regulate bp

• extracellular: blood clotting — contracting and relaxing smooth muscle

• intracellular: signaling for muscle contraction, nerve transmission, hormone secretion, enzyme activation

• recommendations set high to retain in bones (1000-1300 mg depending on age)

• supplements are not better than foods and can be contaminated and increase HD

• smaller dose supplements better than large

• food sources: dairy, leafy greens, sardines with bones

low calcium

PTH + vitamin D increases Ca2+

• thyroid gland/parathyroid gland: signals PTH to be released

• bones: increase osteoclast activity to release Ca2+

• kidneys: increase calcium reabsorption so less is lost in urine, also activate vitamin D to increase absorption

• intestines: increase calcium absorption from food

• high levels: calcitonin secretion from thyroid gland

osteoporosis

low bone mass, making bones weak and prone to fracture

• nonmodifiable factors: females, older age, small frame, family/personal history, estrogen/testosterone deficiency

• modifiable factors: sedentary, excessive protein/Na/caffeine, inadequate of Ca2+ and vitamin D, alc abuse, cigarette smoking, low BW, certain meds

• active growth: age 10

• peak bone mass: age 20

• bone loss: age 35+

phosphorus

second most abundant mineral, big role in mineralization (making bones stronger) aka hydroxyapatite

• not easy to become deficient because Americans overconsume it compared to Ca2+, want the opposite

• phytic acid: storage form — (legumes)

• roles: major buffer system (maintain pH), DNA/RNA, energy met, transport lipids, cell membranes

• food sources: dairy, meat, seafood, nuts, seeds, legumes

magnesium

mineral that serves enzyme functions, bone health, muscle function and relaxation, nerve function, heart health, bp regulation, blood sugar regulation

• relaxation: ex- pregnant

• enzyme function: therapeutic treatment to relax uterus for childbirth

• most adults come in short bc food sources are healthy

• food sources: banana, avocado, leafy greens, nuts, halibut (fish)