Nutrients for food & electrolyte balance & antioxidant function Flashcards
Fluid Facts
-Body fluids comprised of
*Water (solvent)
*Dissolved substances (solutes)
~Electrolytes: sodium, potassium, chloride, phosphorus
-Our bodies contain more water than anything else
-50-70% of body weight is fluid
*95% of blood is fluid
*>70% of muscle is fluid
*25% of bone is fluid
*10-20% of fat is fluid
Where Is The Fluid Located?
- Found in blood, lymph, cells, between cells, tears, GI mucus/saliva, spinal column, joints
- 2/3 fluid is intracellular
- 1/3 extracellular
- Interstitial- between cells or
- Intravascular- inside blood vessels & lymph
- ↑ intracellular fluid → cells burst
- ↓ intracellular fluid → cells collapse
Fluid Composition: Water
-Water: the most important nutrient on a daily basis (no reserve), death after 3-4 days without water
Functions:
- Dissolves solutes
- Transports substances
- Blood volume & blood pressure
- Lubricant and protection
- Regulates body temperature
- Chemical reactions
External Factors That Influence Water Balance
- Illness: fever, cough, vomit, diarrhea
- Injury with blood loss
- ↑ exercise
- Variations in temperature, humidity and altitude
- Pregnancy & breastfeeding
- Diuretics – alcohol (blocks ADH), medications
- Caffeine- mild diuretic, 500 mg/d do NOT cause dehydration (4.5 c of coffee/day)
- High fiber, protein & sodium diet
Regulation of Body Water
-↓ body water = increase blood solutes and decrease blood volume and decrease blood pressure
*Due to: vomiting, diarrhea, sweating, low fluid intake
-This signals
*Hypothalamus to trigger sensation of thirst
*GI to absorb more water- constipation
*Hormonal control of urinary losses
~Antidiuretic hormone (ADH): reabsorb water (in response to ↑ solutes)
~Renin-angiotensin-aldosterone system: reabsorb Na and Cl and water (in response to ↓ BV) & vasoconstriction
Water Needs
- Depends on body size, health status, physical activity, environment, diet
- DRI (beverages & food sources)
- Men: 3.7 L/day
- Women: 2.7 L/day
- Hard to know how much you get in food
- General guideline: ~ 8 c (~2 L) water daily
What Should Most People Be Drinking?
- Water!
- Milk
-Exceptions: excessive sweating, vomiting, diarrhea, prolonged activity (exercise >1 hr at 60% maximal effort), physical work in high heat… electrolyte replacement drinks
Dehydration
- Who is at risk? excessive sweating, elderly, babies, diarrhea, excessive heat
- Measured as % body weight loss (weigh before & after)
- 1-2% strong thirst sensation, athletic performance can decline
- 3-5% dry mouth, reduced urine output
- 6-8% muscle weakness, dizziness, exhaustion, increased body temperature, increased heart rate
- 9-11% ↓ blood volume & pressure, delirium
- 20% coma and death
Prevention of Dehydration
-Assess your needs, consider what?
-Use water fountains
-Carry water
-Exercise
< 1 hr: water
> 1 hr: CHO & electrolytes
Athletes: Pre-hydrate & Re-hydrate
Fluid Composition: Electrolytes
- Body fluids = water + dissolved solutes
- Electrolytes: mineral salts separate in solution into ions (carry electrical current)
NaCl → Na+ & Cl-
- Extracellular electrolytes: Na+ & Cl-
- Intracellular electrolytes: K+ & H2PO4-
The Function of Electrolytes: Fluid Balance
- Electrolytes regulate intra & extracellular fluid balance
- Cell permeable to water, not electrolytes
- Osmosis: water moves from a low to a high concentration of solutes
The Function of Electrolytes: Fluid Balance (active transport)
- Electrolytes moveacross membranesto maintain theappropriate electrolyteconcentration (& fluid)via active transport (proteincarrier & ATP)
- Sodium-potassiumpump- 20-40% of REE
The Function of Electrolytes: Nerve & Muscle Response
- Nerve conduction
- Nerve impulse created by a change in the electrical charge across the nerve cell membrane due to an influx of Na resulting in a change in electrolyte concentrations
- Ca is involved when the nerve impulse reaches its target site
- Muscle contraction
- Similar change in electrolyte concentrations but with the addition of calcium allowing muscle fibers to slide and contract
Regulation of Electrolytes
- Blood levels of electrolytes tightly controlled
- Largely regulated by the kidneys
- Reabsorb or filter depending on blood levels
- Reabsorb sodium & chloride as a means to reabsorb water (fluid balance)
- Salt-sensitive people do not filter as well, retain more water and have increased BV and BP
Sodium
- Principle extracellular cation
- Functions: fluid balance, nerve transmission, muscle contractions
- Kidneys regulate levels well
- filter excess
- reabsorbed if low BV
- 30-50% may not filter well
- When ↑ Na+ intake, thirst signals to dilute with water
- Toxicity: high blood pressure, fluid accumulation
- Deficiency: rare, hyponatremia in athletes that replace fluids w/o electrolytes (headache, dizzy, nausea, muscle cramps, coma, death)
Sodium Sources & Needs
-Estimated requirement: 200-500 mg
-AI: 1,500 mg/d (19-50 y.o.)
-UL: 2,300 mg/d (1 tsp salt)
-Dietary Guidelines:
↓ sodium to 2,3oo mg and to 51 year old, or any age African American, or have hypertension, DM, kidney disease
- Average intake: 3,000-6,000 mg daily
- Sources: salt, processed foods
Potassium
-Principle intracellular cation
-Functions: fluid balance, nerve transmission, muscle contraction (heartbeat regulation), help lower BP (suppresses renin-angiotensin system)
-Deficiency: rare not d/t food (diuretics, GI losses, anorexia); irregular heart beats, hypertension
Toxicity: not unless kidney disease, could lead to possible heart attack
Potassium Sources
- Abundant in fresh foods & fruits & vegetables
- Lost in processing
Hypertension
- ↑ BP → ↑ risk of CVD, stroke, kidney disease
- Systolic: pressure when heart contracts
- Diastolic: pressure between contractions
- Optimal: 140/90 mm Hg
- ↓ BP: exercise, weight loss, ↓ alcohol, ↓ sodium, ↑ potassium, ↑ F/V & whole grain, DASH diet
Antioxidants: Against Oxidation
- Oxidation: chemical reaction where an atom loses an electron
- Reduction: atom gains an electron
Free Radicals: The Bad Guys
- If a stable atom loses an electron during oxidation –> unstable atom now called a free radical
- Free radicals are very reactive
- React with other molecules to become stable
- In the process they can form more free radicals, can lead to a chain reaction
- Free radicals form from metabolism, pollution, tobacco smoke, sunlight exposure
Free Radical Damage
- Free Radicals can damage
- Unsaturated fatty acids in cell membranes, damaged membranes change cell functioning & cell death
- LDL, cell proteins & DNA
- Associated : cancer, heart disease, diabetes, macular degeneration (leading cause of blindness in older adults)
Antioxidants: The Good Guys
- Vitamins A, C, E , beta-carotene & phytochemicals : stabilize free radicals by donating a H or their electrons
- Minerals: components of antioxidant enzymes that help remove free radicals such as
- Superoxide dismutase (contains Cu, Zn, Mn) converts free radicals to less damaging molecules (hydrogen peroxide)
- Catalase (contains Fe) converts hydrogen peroxide to water & oxygen
- Glutathione peroxidase (contains Se) removes hydrogen peroxide from the body, stops production of free radicals in lipids
Vitamin E
- Fat soluble vitamin- 90% are stored in our adipose tissue, the rest in cell membranes
- Functions: fat soluble antioxidant that prevents oxidation of
- Fatty acids & PUFA in cell membranes
- LDL
- RBC membranes
- Lung cells
- Added to oils and products to reduce rancidity
Vitamin E Deficiency & Toxicity
Deficiency:
- Rare
- Results from diseases causing fat malabsorption
- Membrane damage
- RBC rupturingresulting in anemia
Toxicity:
- Uncommon via food
- Supplemental doses (400 IU) may ↑ risk of heart failure, stroke and death
- Supplements contraindicated with some anticoagulant drugs (aspirin, Coumadin)- interferes with forming prothrombin- ↑ bleeding
Vitamin C (Ascorbic Acid)
-Water soluble vitamin, excess is disposed of in the urine (take daily)
-Functions
*Antioxidant (water-soluble), important in extracellular fluid
~Protects WBC from oxidation enhances immune function, ↓ cold duration if taken regularly at doses ↑ RDA
~Protects lung cells from oxidation
~Regenerates vitamin E
*Iron absorption
*Collagen formation
Vitamin C: Additional Functions
Collagen synthesis
-Connective tissueprotein found inskin, teeth, bone,tendons, blood vessels
Vitamin C Deficiency & Toxicity
Deficiency:
- Scurvy: bleeding gums
- Weakened blood vessels
- Pinpoint hemorrhages
- Bruising
- Bone & joint aches
- Bone fractures
- Poor wound healing
Toxicity: unlikely- excreted in urine
Vitamin C: RDA
-Men: 90 mg/day -women: 75 mg/day
- Smokers require more: RDA + 35 mg/day
- Smokers & people around second-hand smoke have lower blood levels
- More for wound healing (surgery, burns) but amount not known
-UL: 2,000 mg- side effects can occur
Vitamin C: In the Diet
- Citrus fruits excellent source
- Other fruits & vegetables good source
- Unstable and destroyed by oxygen, light, and heat
Vitamin E: In The Diet
- Cooking oils
- Nuts & seeds
- Fortified cereals
- Very easily destroyed byheat, light, oxygen
-RDA: 15 mg alpha tocopherol/day (22.5 IU)
Vitamin A & Beta-Carotene
Vitamin A refers to
-Preformed vitamin A: the active form of the vitamin your body will use
- Provitamin A carotenoids
- Carotenoid: orange, red, yellow plant pigments
- Provitamin: inactive form of a vitamin that the body can convert to an active form
- Three provitamin A carotnoids: alpha & beta carotene and beta-cryptoxanthin
- Lutein, Lycopene, zeaxanthin
Beta-Carotene: Provitamin A Carotenoid
- Beta-carotene –> retinal (active vitamin A) in SI
- Functions: Provitamin A, fat-soluble antioxidant (LDL, skin, eyes)
- Deficiency: none, does not play an essential role in our body
- Excess consumption: carotenosis (yellowing of skin), supplements ↑ risk of death
Preformed Vitamin A
- Fat soluble vitamin, 90% stored in liver
- Three active forms in body: retinol, retinal, retinoic acid
- Functions
- Fat-soluble antioxidant
- Cell differentiation, reproduction and growth
- Eyesight- light/dark & color
Retinol
- vision
- sexual reproduction
- bone health
- immune function
Retinal
- vision
- sexual reproduction
- bone health
- immune function
Retinoic acid
- Cell differentiation
- bone health
- immune function
Vitamin A: Deficiency & Toxicity
Deficiency:
- Worldwide leading cause of blindness
- Night blindness
- Color blindness
- Xeropthalmia (blindness due to hardening of the cornea , mucus forming cells deteriorate)
Toxicity:
- Rarely from food
- From 5-10 x RDA via supplements:
- Liver & bone damage
- Teratogenic: causing birth defects & abortion
- Increased risk of death
Why Deficiency in Developing Countries?
-Africa, South America, India, Asia
-Insufficient intake of
*Animal
*Low-fat/Low-protein/High starch diets
~Need fat for absorption
~Need protein to make retinol-binding protein that transports vitamin
~High starch foods not high in carotenoids
Beta-Carotene and Vitamin A in the Diet
- Preformed vitamin A: animal foods (liver), fortified milk
- Provitamin A: plants (orange)
Selenium
- Trace mineral
- Part of glutathione peroxidase
- Helps produce thyroid hormone
- Sources: animal foods
- Deficiency: rare
- Toxicity: not from food
