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4) Nutrition Through Life > 5) Fat, Carbohydrate, Water, Mineral, Electrolyte, and Vitamin Requirements in Adulthood (Part I) > Flashcards

5) Fat, Carbohydrate, Water, Mineral, Electrolyte, and Vitamin Requirements in Adulthood (Part I) Flashcards

1
Q

What do omega-3 and omega-6 fatty acids compete for?

A

They compete for the same desaturase enzymes used in the elongation and desaturation of these fatty acids

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2
Q

What occurs if there is an excess of linoleic acid (omega-6) as compared to linolenic acid (omega-3)?

A
  • Exhausts the desaturase enzymes to the detriment of a-linolenic acid
  • Results in a greater production of arachidonic acid than DHA (pro-inflammatory effects)
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3
Q

What type of fatty acid does a high ratio of omega-6 to omega-3 fatty acids produce?

A

Arachidonic acid

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4
Q

What type of fatty acid does a low ratio of omega-6 to omega-3 fatty acids produce?

A

DHA

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5
Q

What DRI is used to estimate the requirement for omega-6 and omega-3 fatty acids? How is it established?

A
  • Adequate Intake (AI)

- Based on the median intake by US and Canadian adults, in which there is a lack of evidence for deficiency

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6
Q

How does the AI for omega-6 fatty acids fluctuate based on sex and age? Why?

A
  • Omega-6 fatty acids are readily used for energy
  • AI is higher in men
  • AI is lower for people above the age of 50
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7
Q

Which fatty acids contribute to the requirement of omega-3 fatty acids, aiding in the reversal of omega-3 fatty acid deficiency?

A

EPA and DHA

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8
Q

In a post-absorptive state, which pathways produce glucose?

A
  • 50% glycogenolysis in the liver

- 50% gluconeogenesis in the liver

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9
Q

In subjects adapted to starvation, what produces the brain’s energy rquirement?

A

Keto acid oxidation produces around 80% of the brain’s energy requirement

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10
Q

What two factors determine the EAR for carbohydrates? (2)

A

An adequate supply of glucose to provide the brain:

1) Without additional glucose production from protein or TGs
2) Without an increased quantity of ketones greater than observed after an overnight fast

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11
Q

What two factors does the EAR of carbohydrates assume? (2)

A

1) An energy-sufficient diet with AMDR of carbohydrates equal to 45 to 65%
2) Glucose is not limiting to the brain

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12
Q

What are the carbohydrate-dependent organs?

A

The ONLY carbohydrate-dependent organ is the brain

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13
Q

What are consequences of low-carbohydrate diets, observed in urbanized societies?

A

An increase in keto acids

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14
Q

What are the effects of a high concentration of keto acids?

A

May lead to bone mineral loss, high blood cholesterol, increased risks of kidney stones, urinary tract deposits

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15
Q

Define fiber.

A
  • Non-digestible carbohydrates and lignin that are intrinsic and intact in plants
  • Not digested and absorbed in the small intestine
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16
Q

Define functional fiber.

A

Isolated, non-digestible carbohydrate shown to have beneficial physiological effects in humans

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17
Q

What are examples of functional fiber?

A
  • Pectins
  • Gums
  • Chitin
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18
Q

What does total fiber refer to?

A

Functional fiber and dietary fiber

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19
Q

There is a strong negative correlation between the intake of cereal fiber, and the risk of ________________.

A

cardiovascular diseases

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20
Q

How do fruits and vegetable fibers contribute to decreasing the risk of cardiovascular diseases?

A
  • They do not (weak or non-existent correlation)

- Cereal fibers confer resistance to cardiovascular diseases

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21
Q

What are the four benefits of fiber? (4)

A

1) Amelioration of constipation and diverticular disease
2) Fuel for colonic cells
3) Decrease in blood glucose and lipids
4) Acting as a source of nutrient-rich low-energy foods (increases satiety and decreases obesity)

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22
Q

What makes determining an EAR for fiber difficult?

A
  • The benefit of an increased total fiber intake is continuous across a range of intakes
  • Defining a cut-off point is difficult
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23
Q

What DRI is used to estimate the requirement for fiber? How is it established?

A
  • Adequate Intake (AI)

- Based on the intake of the population demonstrating a lower risk of cardiovascular diseases

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24
Q

Which types of fiber provide the greatest reduction in cardiovascular risk?

A
  • Cereal fiber

- Proven functional fibers (psyllium and pectin)

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25
Q

How does fiber decrease cardiovascular risk?

A

Certain types of fiber bind cholesterol and prevent their absorption, decreasing cardiovascular risk and cholesterol

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26
Q

How does the requirement for fiber vary throughout the life cycle?

A
  • There is no indication that fiber intake as a function of energy differs during the life cycle
  • Thus, 14 grams of fiber per 1000 calories is applied to ALL life stages
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27
Q

What dictates fluid intake?

A

Behaviour, and NOT thirst

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28
Q

What mechanisms allow for the detection of thirst?

A
  • Decrease in body water (detected by a low blood volume)

- Primarily sensed by an increase in sodium (detected by osmoreceptors in the brain)

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29
Q

What is the primary indicator of water status?

A

Plasma or serum osmolality

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30
Q

What is osmolality?

A

Measure of the osmoles per kilogram of solvent

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31
Q

What is osmolarity? Why is it not used to measure hydration status?

A
  • Osmolarity is a measure of the osmoles per liter of solvent
  • An addition of solutes may change the volume of a solution
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32
Q

What creates an osmotic load?

A

Metabolizing dietary protein and organic compounds, and varying intakes of electrolytes

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33
Q

What must the osmotic load be accommodated for?

A

Adequate water consumption

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34
Q

How does the inadequate replacement of fluids during exercise place strain on the cardiovascular system?

A
  • Leads to dehydration and heat dissipation

- Elevates core body temperature

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35
Q

Why is there not a single level of water intake that would ensure adequate hydration and optimal health for half of the population of healthy individuals?

A

Given the extreme variability in water needs based on metabolism, environmental conditions, and activity

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36
Q

What DRI is used to estimate the requirement for water? How is it established?

A
  • AI (Adequate Intake)

- Based on the median total water intake from survey data

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37
Q

What factor is used to set the AI for water?

A

To prevent deleterious effects of dehydration, which include metabolic and functional abnormalities

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38
Q

How is the intake of water related to chronic disease?

A
  • It is not

- There is insufficient evidence to set an EAR for water-based reduction of chronic disease

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39
Q

What study provides a link between hydration status and type II diabetes?

A
  • Elevated ADH (in a state of dehydration) leads to a higher fasting glycaemia in rats
  • Hydration decreases adiposity
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40
Q

In physically-active adults, what does the requirement for water depend on?

A
  • Sweat loss

- Can exceed 10 liters per day

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41
Q

What is the UL for water?

A
  • There is NO established UL for water because excessive fluid consumption is extremely rare
  • Results in exertional hyponatremia
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42
Q

What DRI is used to estimate the requirement for calcium? How is it established?

A
  • RDA
  • Calcium balance studies to determine the recommendation necessary to achieve small gains of bone mineral content
  • Based on clinical trial data showing bone mineral density
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43
Q

How does the RDA for calcium differ between males and females?

A

The requirement is the same for all sexes

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44
Q

What form of phosphorus is found primarily? Where is it largely contained?

A
  • Phosphate (PO4-)

- Bones and teeth

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45
Q

What are the four functions of phosphorus? (4)

A

1) Aids in the maintenance of pH by acting as a buffer
2) Acts as a temporary energy source (e.g. ATP)
3) Required for phosphorylation
4) Structural component (e.g. phospholipids, nucleotides, nucleic acids)

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46
Q

What DRI is used to estimate the requirement for phosphorus? How is it established?

A
  • RDA

- Based on studies of serum inorganic phosphate concentrations (including the absorption efficiency of phosphorus)

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47
Q

What is the absorption efficiency of phosphorus?

A

60 to 65%

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48
Q

Where is magnesium largely contained?

A

50 to 60% of magnesium is found in bone

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49
Q

What are the functions of magnesium? (2)

A

1) Bone magnesium serves as a reservoir for maintaining normal extracellular magnesium
2) Required as a cofactor for over 300 enzymes

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50
Q

What DRI is used to estimate the requirement for magnesium? How is it established?

A
  • RDA

- Based on total body magnesium, assessed using balance studies

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51
Q

How does the RDA for magnesium vary between age groups?

A

The requirement for magnesium is higher in older individuals

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52
Q

What factors explain why the RDA for magnesium is higher in older subject?

A

1) The consumption of high-fiber diets increase with age, and magnesium is poorly absorbed
2) Renal function declines with age, and it is critical in the maintenance of magnesium status

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53
Q

Factorial modelling is used for the the requirement of which nutrient?

A

Iron

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54
Q

What are the four factors used in factorial modelling for the determination of the EAR of iron?

A

1) Basal iron losses
2) Menstrual iron losses
3) Fetal requirements in pregnancy
4) Growth

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55
Q

How does the percentage absorption vary with serum ferritin concentrations?

A

The percentage of absorption is inversely proportional to serum ferritin concentrations

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56
Q

What DRI is used to estimate the requirement for iron? How is it established?

A
  • RDA

- Based on the need to maintain a normal, functional iron status, while maintaining a minimal iron store

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57
Q

Differentiate heme and non-heme iron.

A
  • Heme (meat, poultry, fish): always well absorbed, and is only slightly influenced by dietary factors
  • Non-heme iron (all foods): strongly influenced by solubility as well as through interactions with other meal components
58
Q

In a typical mixed diet, children over a year old, adolescents, and non-pregnant adults are assumed to possess a bioavailability of __% for iron.

A

18

59
Q

How does the determination of the EAR for iron differ in men and women?

A
  • Men: based on basal iron losses

- Women: based on basal iron losses and menstrual losses

60
Q

How does the requirement in iron for men differ from the requirement for pre-menopausal women? How does it differ after menopause?

A
  • Requirement for iron is LOWER in men than in pre-menopausal women
  • Requirement between men and post-menopausal women are SIMILAR
61
Q

What DRI is used to estimate the requirement for potassium? How is it established?

A
  • Adequate Intake (AI)

- Based on the physiological functions of an adequate intake of potassium

62
Q

What are the four physiological functions of an adequate intake of potassium? (4)

A

1) Lowering blood pressure
2) Blunting the adverse blood-pressure effects of salt intake
3) Reduce the risk of kidney stones
4) Potentially reducing bone loss

63
Q

What characterizes a moderate potassium deficiency?

A
  • High blood pressure
  • Increased risk of kidney stones
  • Cardiovascular diseases
64
Q

How does hypokalemia affect sodium excretion?

A
  • May result in decreased sodium excretion

- Hypokalemia may result in cardiac arrhythmias, muscle weakness, and glucose intolerance

65
Q

What is dietary potassium derived from fruits and vegetables normally associated with? What form is it?

A
  • Organic anions (e.g. citrate)

- Potassium citrate

66
Q

What is the importance of organic anions that are associated with potassium?

A
  • They are converted to bicarbonate after absorption

- Bicarbonate may act as a buffer to neutralize acids from the diet

67
Q

What occurs if there is a deficiency in bicarbonate precursors?

A

The body must use another type of buffer, which is normally drawn from the bone matrix, leading to increased bone turnover

68
Q

Where is potassium largely contained?

A

Intracellularly

69
Q

Are athletes recommended to increase their potassium intake? Why or why not?

A
  • Sweat potassium represents a very small percentage of the available potassium
  • However, profuse sweating may nonetheless increase potassium requirement
  • The AI for potassium is the same for sedentary and physically active adults
70
Q

What is the UL for potassium?

A
  • There is NO UL for potassium, as there is no evidence that a high level of potassium from foods has any adverse effects
  • However, the ingestion of too much potassium may result in hyperkalemia or arrhythmias
71
Q

There is a wide variation in daily sodium requirements, particularly in which individuals?

A

Athletes, workers, and soldiers (i.e. individuals that sweat profusely)

72
Q

What is the primary route of sodium loss in sedentary individuals?

A

Urine

73
Q

Where is sulfur primarily contained?

A
  • Certain amino acids (methionine, cysteine, cystine)

- Component of essential compounds (e.g. glutathione)

74
Q

What DRI is used to estimate the requirement for sulfur? How is it established?

A
  • There is no intake requirement established because sulfate intake typically exceeds needs, as they are largely contained in amino acids
  • If an individual is consuming an adequate quantity of protein, they are likely to exceed their sulfate requirement as well
75
Q

What indicates that sulfur is not limiting when protein requirement is reached?

A

Urinary excretion of sulfate is adequate when an individual is consuming a sufficient quantity of protein

76
Q

What is vitamin B1?

A

Thiamine

77
Q

What is the major function of thiamine?

A

Functions as a coenzyme in the metabolism of carbohydrates and branched-chain amino acids

78
Q

Which derivative of thiamine is required for carbohydrate metabolism?

A

Thiamine pyrophosphate (TPP)

79
Q

Which enzyme is dependent on thiamine?

A

Transketolase, which requires TPP

80
Q

What two factors determine the requirement for thiamine? (2)

A

1) The quantity required to achieve and maintain transketolase activity within RBCs
2) Without excessive thiamine excretion

81
Q

What is the function of transketolase?

A
  • Enzyme of the pentose phosphate pathway

- The PPP generates NADPH, which functions as a reducing agent

82
Q

Biochemical changes in which vitamins occur before the appearance of overt signs of deficiency?

A
  • Thiamine (vitamin B1)

- Riboflavin (vitamin B2)

83
Q

What is thiamine deficiency? What does it affect?

A
  • Beriberi

- Affects the heart and circulatory system, and occurs solely when there is an extreme thiamine deficiency

84
Q

What are three methods to analyze thiamine status? (3)

A

1) Erythrocyte transketolase activity
2) Thiamine and thiamine-phosphorylated ester concentrations in blood
3) Urinary thiamine excretion under basal loading and after thiamine loading

85
Q

How does the requirement for thiamine vary between men and women?

A

The requirement for men is higher than women given differences in terms of energy utilization and body size

86
Q

How does the requirement for thiamine vary with age?

A
  • Thiamine requirements may be elevated in the elderly

- But, there is a decrease in energy utilization, which results in a decreased need for thiamine

87
Q

How does the median intake of thiamine compare to the requirement?

A

The median intake is superior to the requirement

88
Q

What is vitamin B2?

A

Riboflavin

89
Q

What is the major function of riboflavin?

A

Functions as a coenzyme in various oxidation-reduction reactions, involved in several metabolic pathways and energy production

90
Q

What three factors determine the requirement for riboflavin? (3)

A

1) Erythrocyte glutathione reductase activity coefficient
2) Concentration of riboflavin in RBCs
3) Urinary riboflavin excretion

91
Q

The EAR of riboflavin for adults is derived from which three methods?

A

1) Studies of occurrence of signs and clinical deficiency
2) Biochemical values
3) Urinary excretion in relation to dietary intake

92
Q

How does the requirement for riboflavin vary between men and women?

A

The requirement for men is higher than women given differences in terms of energy utilization and body size

93
Q

How does the median intake of riboflavin compare to the requirement?

A

The median intake is superior to the requirement

94
Q

Deficiencies for riboflavin are unlikely. When would they be observed?

A

In the case of severe alcohol consumption

95
Q

What is vitamin B3?

A

Niacin

96
Q

What is the major function of niacin?

A
  • Functions as a co-substrate or coenzyme for the transfer of H- by dehydrogenase enzymes
  • Used in oxidation and reduction reactions (intracellular respiration, fatty acid synthesis)
97
Q

What determines the requirement for niacin?

A

Urinary excretion of niacin metabolites, as an excess of niacin is methylated in the liver for excretion in urine

98
Q

What adjustments are made for niacin in terms of bioavailability?

A

There are no adjustments made, but the requirement is expressed as niacin equivalents (NEs)

99
Q

What are the two sources of niacin? (2)

A
  • Conversion of tryptophan to niacin

- Acquisition of niacin from the diet

100
Q

What is the efficiency of conversion of tryptophan to niacin?

A

60:1 (tryptophan to niacin)

101
Q

A deficiency in which nutrients may decrease the conversion of tryptophan to niacin, increasing the requirements of exogenous niacin?

A
  • Iron
  • Riboflavin
  • Pyridoxine
102
Q

Which nutrients possess a large coefficient of variation?

A
  • Niacin (15%)

- Vitamin A (20%)

103
Q

Why is the coefficient of variation of niacin large?

A

Due to the individual variability in terms of the conversion efficiency of tryptophan to niacin

104
Q

How does the median intake of niacin compare to the requirement?

A

The median intake is much superior to the requirement

105
Q

What is vitamin B6?

A

Pyridoxine and related compounds

106
Q

What is the major function of pyridoxine?

A

Serves as a coenzyme in the metabolism of amino acids, glycogen, and sphingoid bases

107
Q

What determines the requirement for pyridoxine?

A

The maintenance of adequate blood 5’-pyridoxal phosphate levels, which is the active form of vitamin B5

108
Q

What is vitamin B9?

A

Folate

109
Q

What is the major function of folate?

A

Functions as a coenzyme in single-carbon transfers in the metabolism of nucleic and amino acids

110
Q

What two factors determine the requirement for folate? (2)

A

1) Erythrocyte folate

2) Blood homocysteine and folate concentrations

111
Q

Why are dietary folate equivalents (DFEs) required?

A

To adjust for the fact that folate from food is 50% less bioavailable than folic acid from supplements or fortified foods

112
Q

What is 1ug of DFE equivalent to in terms of food folate, folic acid, and a supplement taken on an empty stomach?

A
  • Food folate: 1 ug
  • Folic acid: 0.6 ug
  • Supplement taken on an empty stomach: 0.5 ug
113
Q

What is the major function of vitamin B12?

A
  • Coenzyme for methyl transfer reactions
  • Homocysteine to methionine
  • L-methylmalonyl-coenzyme A to succinyl-CoA
114
Q

What two factors determine the requirement for vitamin B12? (2)

A

1) The maintenance of hematological status

2) Normal blood vitamin B12 values

115
Q

What is vitamin B7?

A

Biotin

116
Q

What is the major function of vitamin B7?

A

Functions as a coenzyme in bicarbonate-dependent carboxylation reactions

117
Q

Which B-vitamins possess an AI?

A
  • Biotin (vitamin B7)

- Pantothenic acid (vitamin B5)

118
Q

What is the major function of choline?

A

Precursor for acetylcholine, phospholipids, and the methyl donor betaine

119
Q

What DRI is used to estimate the requirement for choline? How is it established? What factor does it take into consideration?

A
  • AI
  • Assessed by serum alanine aminotransferase levels
  • The prevention of liver damage
120
Q

What does a deficiency in choline cause? What may that lead to?

A
  • Muscle damage and abnormal fat deposition in the liver

- Non-alcoholic fatty liver disease (NAFLD)

121
Q

What does the assembly and exportation of VLDLs require? What occurs if it is deficient?

A
  • Phosphatidylcholine
  • If choline is deficient, phosphatidylcholine may not be synthesize, which causes lipids to accumulate, leading to NAFLD
122
Q

How does phosphatidylcholine play a role in lowering blood cholesterol?

A

Phosphatidylcholine is required by LCAT, which converts cholesterol into inactive cholesteryl esters

123
Q

How is phosphatidylcholine generated?

A

Phosphatidylethanolamine is trimethylated from SAM by phosphatidylethanolamine methyltransferase, producing phosphatidylcholine

124
Q

How is choline generated through de novo synthesis?

A

Phosphatidylcholine is catabolized by phospholipases, which generates choline

125
Q

The demand for dietary choline is modified by metabolic methyl-exchange relationships between which nutrients?

A

Choline and methionine, folate, and vitamin B12

126
Q

Which study demonstrates that de novo synthesis of choline is NOT sufficient?

A

Healthy men with normal folate and vitamin B12 status fed a choline-deficient diet demonstrated decreased plasma choline and liver damage

127
Q

What DRI is used to estimate the requirement for choline? What is particular about the requirement for choline and certain life stages?

A
  • Adequate Intake (AI)

- The requirement for choline may be met through de novo synthesis at certain life stages

128
Q

What two factors determine the requirement for choline?

A

1) Methionine and folate availability

2) Gender, pregnancy, lactation, and stage of development

129
Q

How does the requirement for choline vary between men and women?

A

The requirement is higher for men than in women

130
Q

How does the requirement for choline vary between age groups?

A

Choline transport across the BBB may decrease, but there is no adjustment

131
Q

What is vitamin B5?

A

Pantothenic acid

132
Q

What is the major function of pantothenic acid?

A

Component of coenzyme A and phosphopantetheine, implicated in fatty acid metabolism

133
Q

Why is a deficiency in pantothenic acid rare? When would it occur?

A
  • Because vitamin B5 is widely distributed in food
  • May occur from a semi-synthetic diet (e.g. elemental diet), or as a result of the ingestion of an antagonist to the vitamin
134
Q

What DRI is used to estimate the requirement for pantothenic acid? What factor is it based on?

A
  • Adequate Intake (AI)

- Intake to replace urinary excretion of pantothenic acid

135
Q

How is the AI of pantothenic acid determined?

A
  • The midpoint of the usual intake of vitamin B5

- There is no evidence that suggests that this intake is inadequate

136
Q

What is the major function of vitamin C?

A
  • Functions as a water-soluble antioxidant

- Cofactor for enzymes involved in the biosynthesis of collagen, carnitine, and neurotransmitters

137
Q

What two factors determine the RDA for vitamin C? (2)

A

1) To maintain near-maximal neutrophilic concentration

2) Minimal urinary excretion of vitamin C

138
Q

What four factors explain why the RDA for vitamin C is lower in women than in men? (4)

A

1) Smaller lean body mass
2) Lower total body water
3) Smaller body size
4) Ability to maintain higher plasma ascorbate than men at a given concentration

139
Q

How does blood vitamin C vary for the elderly population? Why?

A
  • Blood vitamin C is lower in the elderly

- Due to poor dietary intakes, or chronic disease

140
Q

Which population group requires a higher requirement of vitamin C? Why?

A
  • Smokers

- Due to an elevated pro-oxidant environment

4) Nutrition Through Life (19 decks)

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