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
