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FOOD20003 > 6.2 Water and the Major Minerals > Flashcards

6.2 Water and the Major Minerals Flashcards

1
Q

What does the body’s fluid environment consist of?

A
  • The bodies fluid environment actually consists of several distinct regions or compartments
  • Intracellular fluid within cells (high in potassium and phosphate), making up 2/3 of body water
  • Extracellular fluid makes up 1/3 of body water
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2
Q

What does extracellular fluid consist of?

A
  • Interstitial or intercellular fluid – fluid between the cells that is high in sodium and chloride. Provides cells with required nutrients
  • intravascular fluid – fluid within blood vessels ie. plasma
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3
Q

What are the roles of water in the body?

A
  • Carries nutrients and waste products.
  • Participates in metabolic reactions.
  • Solvent for minerals, vitamins, amino acids, glucose and others.
  • Lubricant and cushion around joints, inside the eyes, the spinal cord and in amniotic fluid during pregnancy.
  • Regulation of body temperature. • Maintains blood volume.
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4
Q

What are the sources of water in the body?

A
  • Water and other beverages PLUS foods such as: Fruit and vegetables.
  • By-product of metabolism (ETC particularly) [metabolic water]
  • A daily intake of 1450 - 2800 millilitres of water is usually represented by:
    • Liquids 550 to 1500 mL.
    • Foods 700 to 1000 ml
    • Metabolic water 200 to 300 mL
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5
Q

What are the normal water intake and loss levels?

A

Normal water intake and loss levels for the average person per day, approximately 500 ml is a minimum urinary daily excretion level to remove dissolved waste materials

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6
Q

How does dehydration of water occur?

A
  • Intake from liquids, foods and metabolism equals losses from the kidneys, skin, lungs and faeces.
  • Dehydration occurs when water output exceeds input due to an inadequate intake or excessive losses.
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7
Q

What are the different magnitudes of water loss from the body?

A
  • 1–2 per cent loss of body water weight results in thirst, fatigue, weakness, vague discomfort and loss of appetite.
  • 3–4 per cent loss of body water weight results in impaired physical performance, dry mouth, reduction in urine, flushed skin, apathy etc.
  • 5–6 per cent loss of body water weight results in difficulty in concentrating, headache, irritability, sleepiness, impaired temperature regulation, and increased respiratory rate.
  • 7–10 per cent loss of body water weight results in dizziness, muscle spasms, loss of balance, delirium, exhaustion, and collapse, followed by death if not treated quickly.
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8
Q

What is the relationship between blood volume and blood pressure?

A

Blood volume correlates with blood pressure (BP)

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9
Q

How does antidiuretic hormone (ADH) control blood volume and pressure?

A
  • ADH is released from the pituitary gland in response to concentrated blood, (low blood volume or low BP)
  • ADH stimulates kidneys to reabsorb more water from that which it has just filtered into urine, and decrease excretion of urine
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10
Q

How does the renin-angiotensis system control blood volume and pressure?

A
  • Juxtaglomerular apparatus of the kidney nephrons detect low BP and releases the enzyme renin into the circulatory system. Renin then:
  • activates the hormone angiotensin(ogen) which causes vascular constriction
  • Angiotensin then induces aldosterone release from adrenal glands, that cause the kidneys to reabsorb sodium (hence water reabsorbed by osmosis).
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11
Q
A
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12
Q

What are electrolytes?

A
  • Electrolytes are products of the salts that dissolve in water and dissociate to produce ions, either positive (cations) or negative (anions).
  • eg Sodium chloride (NaCl) dissociates to give Na+ and Cl- (ions)
  • One of the principle functions of electrolytes is to control movement of water into and out of cells, by the actions of osmosis
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13
Q

How is charge distributed for electrolyte solutions in the body?

A
  • Electrolyte solutions in the body usually have equal total positive and negative charges (mEq), not equal numbers of individual ions
  • Charge density and ion type outside a cell is different to inside the cell, and is measured in millequivalents (mEq). ie; there may be a higher concentration of positive ions outside a cell than inside.
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14
Q

Why is water a polar molecule?

A
  • The water molecule is polar (partly positive and partly negative) due to the ability of the oxygen atom to attract the pairs of electrons making up the covalent bonds, more strongly than the hydrogen atom.
  • The negative electrons spend a greater amount of time in the vicinity of the oxygen on their constant movement between the oxygen and hydrogen atoms
  • So oxygen has partial negative charge and hydrogen has partial charge
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15
Q

How does the polarity of water result in osmosis movement?

A
  • Due to this polarity, the water molecule is attracted to and attaches to ions which have complete positive and negative charges
  • Water tends to follow these ions (electrolytes), and in fact clusters around them
  • Water will move to the area with the greatest concentration of ions , ie; a diluting effect to reach equilibrium.
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16
Q

What is osmosis?

A

Osmosis is the movement of water from an area of low solute concentration to an area of high solute concentration. The force that causes this movement is termed osmotic pressure.

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17
Q

How is electrolyte balance maintained by body mechanisms?

A
  • As with water, the amount of electrolytes in the body must remain constant. This involves a balance between intake and excretion.
  • It is controlled by the excretory side of the process by the GI tract and kidneys.
  • Excretion via the sweat glands is an obligatory loss that is not controlled.
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18
Q

How do membrane transport proteins regulate ion movement?

A
  • Transport proteins (cell membrane) regulate positive ion movement into and out of cells, negative ions then follow positive ions by attraction and water then flows toward the more concentrated side of the membrane by osmosis.
  • The sodium potassium pump is an example of a membrane transport protein.
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19
Q

What are the major minerals?

A
  • Major minerals are those that exist in the body in quantities above 5g.
  • Calcium
  • Potassium
  • Sodium
  • Chloride
  • Magnesium
  • Phosphorous (exists mainly in phosphate form or in phospholipids)
  • Sulphur (exists mainly in sulfate form or in proteins)
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20
Q

What is the role of sodium in the body?

A
  • Sodium has a critical role as an extracellular cation.
  • Essential for nerve impulse transmission and muscle contraction
  • Highly soluble and readily absorbed by intestines and travels easily in the blood
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21
Q

What is the source of sodium in the body?

A
  • Salt has been primary source of dietary sodium.
  • Due to its fundamental role for survival, the development of a favourable taste perception is not surprising.
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22
Q

How is sodium removed from the body?

A
  • Removed via glomerular filtration in kidneys and the correct amount is added back into the blood via kidney tubule reabsorption
  • As more sodium is ingested, the person becomes thirsty, causing drinking, allowing more water to be excreted (removing sodium) until levels return to normal
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23
Q

What are the health considerations for sodium intake?

A
  • Excess salt/sodium can cause hypertension
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24
Q

Which food sources are high in sodium?

A
  • Fresh fruit and vegetables and meats are low in salt and sodium
  • Processed foods are high in sodium (and low in potassium)
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25
Q

Is sodium deficiency possible?

A

Sodium deficiency is very rare (possible in extreme dysentry)

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26
Q

What happens when there is sodium toxicty?

A

Acute sodium toxicity results in oedema and raised blood pressure (hypertension).

27
Q

How does processing of food change sodium and potassium levels?

A
28
Q

Where is chloride found in the body?

A
  • Chloride is the major anion of extracellular fluid (outside the cell).
  • Chloride ions can move freely across cell membranes
  • Chloride is critical in maintenance of fluid and electrolyte balance and is an essential component of stomach hydrochloric acid.
29
Q

What happens if there is chloride deficiency?

A
  • Rare but will lead to death.
  • Can occur temporarily in vomiting and diarrhoea and during heavy sweating
30
Q

What is potassium involved in in the body?

A
  • Potassium is a cation, like sodium (but predominates inside cells)
  • It is essential for fluid and electrolyte balance and maintaining cell integrity
  • With sodium and calcium it is involved in nerve impulse transmission, muscle cell contraction and heart beat regulation
31
Q

What are the food sources of potassium?

A
  • Potassium exists in all intact animal and plant cells
  • Fruit and vegetables contain a high potassium : sodium balance.
  • Processing of foods leads to cell breakdown and loss of potassium
  • Our hunter-gatherer ancestors consumed an estimated 10,500 mg K per day compared to the current US intake of 2500 mg / day
32
Q

Which foods are good in potassium?

A
33
Q

What is the role of potassium in the body?

A
  • Maintains normal fluid and electrolyte balance.
  • Facilitates many reactions.
  • Supports cell integrity.
  • Assists in nerve impulse transmission and muscle contractions.
  • Maintains the heartbeat.
34
Q

What happens when there is potassium deficiency?

A
  • Symptoms include muscular weakness, paralysis, confusion, increased blood pressure, salt sensitivity, kidney stones and bone turnover.
  • Later signs include irregular heartbeats, muscle weakness and glucose intolerance.
35
Q

What happens when there is potassium toxicity?

A
  • Results from supplements or overconsumption of potassium salts or medical conditions.
  • Symptoms include muscular weakness and vomiting.
  • If given into a vein, potassium can cause the heart to stop.
36
Q

Where is calcium found in the body?

A
  • Most abundant mineral in the body, mainly in bones and teeth (99%)
  • Bones are a calcium store, releasing calcium into the blood as blood levels fall, blood calcium levels are kept constant while bones are constantly formed and dissolved
37
Q

How is bone and blood calcium kept in balance?

A
  • Bone and blood calcium are kept in balance with a system of hormones and vitamin D.
  • Bone formation involves hydroxyapatite forming on a collagen protein matrix.
38
Q

What are the levels of blood calcium in the blood?

A
  • Approximately 1% of body calcium circulates as Ca2+ ions in the blood.
  • A blood test for calcium status is useless as the blood level is kept constant
39
Q

What are the roles of calcium in the body?

A
  • Regulation of muscle contraction
  • Blood clotting
  • Transmission of nerve impulses
  • Hormone secretion
  • Activation of some enzyme reactions
  • Cofactor for calmodulin (membrane protein which convey messages to cell interior)
  • Low levels of calcium are associated with elevated BP
40
Q

How is blood calcium balance controlled by?

A
  • Controlled by thyroid hormone (calcitonin), parathyroid hormone, vitamin D through their effects on GI tract, kidneys, bones
41
Q
A
42
Q

How much of ingested calcium is absorbed?

A
  • Approx 20-30% of ingested calcium is absorbed, remainder passes through the GI tract bound to other substances
  • Acidity keeps calcium in a soluble form. Best absorbed with meals due to secretion of stomach acid generated by foods.
  • Vitamin D, milk lactose and dietary phosphorus aid calcium absorption
43
Q

How is degree of calcium absorption regulated?

A
  • Degree of absorption is regulated by production of calcium binding protein (CBP - Vitamin D affected) required to bind calcium in the GI tract mucosal cells and subsequent transport into the blood
  • Absorption is higher in children and pregnant women (50-60% absorption)
  • Absorption is hindered by high levels of: fibre, phytates (grains) and oxalates (vegetables) and high protein intakes.
44
Q

What happens when there is calcium deficiency?

A
  • Main condition of deficiency is osteoporosis
  • No early warning signs or symptoms of osteoporosis, as blood calcium levels are usually normal due to calcium loss from bones maintaining the constant blood level.
  • Development of osteoporosis is usually due to poor calcium intake and or absorption and poor bone building in the critical bone development period
45
Q

When does osteoporosis occur?

A
  • From 30 years onward everyone loses bone mass with age and even with a high peak bone mass
  • There are rare cases where low blood calcium occurs, not due to poor intake but a metabolic defect.
46
Q

How can bone mass be maximised?

A
  • Children and adolescents need to consume enough calcium and vitamin D to create denser bones.
  • With a higher initial bone mass, the normal losses of bone density that occur with age will have less detrimental effects
47
Q

How can bone loss be minimised?

A
  • Ensure adequate intakes of vitamin D and calcium are consumed.
  • Adequate physical activity
  • Hormonal changes can increase calcium losses
48
Q

Why is osteoporosis more common in women than men?

A
  • Hormones change very important in osteoporosis
  • Menopause affect oestrogen
  • Helps reach the dangerous critical zone
  • No sharp middle age decrease for men
49
Q

Why is loss of height seen due to loss of bone density over time?

A
  • Loss of height seen particularly in women as they age, due to bone loss involved with osteoporosis
  • Men would also suffer osteoporosis (and some do), but because men in “general” eat more food (hence calcium) and do more physical work than most women, thus they tend to build up high bone mass in younger years.
50
Q

What are the signs of calcium toxicity?

A
  • Signs include: constipation, kidney stones and interference with absorption of other minerals.
  • High blood calcium (not caused by diet) results in a condition known as calcium rigor in which muscles contract and cannot relax
51
Q

What happens when you have low blood caclium?

A
  • Low blood calcium (may be diet related in rare cases) results in a condition known as tetany, an involuntary contraction of muscles
  • Tetany or rigor generally result from lack of vitamin D or abnormal hormone secretion not calcium intake per se.
52
Q

What are the risk factors for osteoporosis?

A
53
Q

What are the protective factors for osteoporosis?

A
54
Q

In what forms is phosphorus found in the body?

A
  • Second most abundant mineral in the body, approx 85% is in hydroxyapetite crystals ( Ca5(PO4)3(OH) )which make up approx 70% of the weight of bones and teeth.
  • Small but critical amounts are found in all cells as part of the energy metabolism process mainly as ATP, ADP and AMP , in the phospholipids of cell membranes also in DNA and RNA.
55
Q

What is the function of phosphorus in the body?

A
  • In all body cells as part of a buffer system involving phosphate (PO43-)
  • Part of DNA and RNA as phosphate groups hence involved in growth
  • Involved in energy transfer on ATP, ADP and AMP
  • Also many enzymes and B vitamins require a phosphate group to become active
  • Lipid structure: eg phospholipids which are needed in cell membrane structure and to transport other lipids in the blood (lipoproteins)
  • Some proteins also contain phosphorus (eg casein)
56
Q

What are the food sources of phosphorus?

A
  • Diets with adequate energy and protein would normally contain adequate phosphorus as it is found in all animal tissue, milk and most plant tissue, particularly legumes.
  • Yoghurt, cheese, sunflower seeds and liver are particularly rich sources.
57
Q

What is the deficiency and toxicity of phosphorus?

A
  • Dietary deficiency is unknown. Some drugs however bind to phosphorous making it unavailable leading to bone loss, weakness and pain.
  • Rare but can lead to lowered calcium levels
58
Q

Where is magnesium found in the body?

A
  • There is only approx 25g magnesium in the body, over half of which is in the bones, the remainder being predominantly in soft tissues.
  • Less than 1% is found extracellular fluids.
  • As with calcium and phosphorous, bone magnesium acts as a reservoir to ensure constant blood magnesium level.
59
Q

What is the function of magnesium in the body?

A
  • Involved in energy metabolism, particularly as a catalyst for the addition of a phosphate group to ADP to produce ATP and in the body’s use of glucose
  • Assists over 300 enzymes acting as a cofactor in the production of proteins, fats and nucleic acids in cells
  • Involved in blood clotting and muscle contraction. Holds calcium in tooth enamel preventing dental caries.
  • Supports the normal functioning of immune system and is involved in nerve impulse transmission
  • Protects against heart disease and hypertension
  • (Low magnesium restricts walls of arteries and capillaries)
60
Q

What is the source of magnesium?

A
  • Magnesium is part of chlorophyll, therefore is rich in green leafy vegetables
  • Rich in some water supplies. May be an important contributor in some areas.
61
Q

What happens in magnesium deficiency?

A

Deficiencies are rare, but symptoms include:

  • Weakness and confusion.
  • Convulsions in extreme deficiency.
  • Bizarre muscle movements of the eye and face.
  • Hallucinations.
  • Difficulties in swallowing.
  • Growth failure in children.

Develops from alcohol abuse, protein malnutrition, kidney disorders and prolonged vomiting and diarrhoea.

62
Q

What are the symptoms of magnesium toxicity?

A

Symptoms from non-food magnesium are diarrhoea, alkalosis and dehydration.

63
Q

Where is sulfur found in the body?

A
  • Sulphur is important as part of thiamin, biotin, insulin and the amino acids methionine and cysteine.
  • Cysteine controls the 3D shape of proteins by forming a link with another cysteine in a different part of the chain by a ‘disulphide bridge’
  • NoRDI or deficiency states known
  • Most sulfur in the body is in proteins

FOOD20003 (14 decks)

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