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
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)
3
Q
What type of fatty acid does a high ratio of omega-6 to omega-3 fatty acids produce?
A
Arachidonic acid
4
Q
What type of fatty acid does a low ratio of omega-6 to omega-3 fatty acids produce?
A
DHA
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
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
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
8
Q
In a post-absorptive state, which pathways produce glucose?
A
- 50% glycogenolysis in the liver
- 50% gluconeogenesis in the liver
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
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
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
12
Q
What are the carbohydrate-dependent organs?
A
The ONLY carbohydrate-dependent organ is the brain
13
Q
What are consequences of low-carbohydrate diets, observed in urbanized societies?
A
An increase in keto acids
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
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
16
Q
Define functional fiber.
A
Isolated, non-digestible carbohydrate shown to have beneficial physiological effects in humans
17
Q
What are examples of functional fiber?
A
- Pectins
- Gums
- Chitin
18
Q
What does total fiber refer to?
A
Functional fiber and dietary fiber
19
Q
There is a strong negative correlation between the intake of cereal fiber, and the risk of ________________.
A
cardiovascular diseases
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
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)
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
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
24
Q
Which types of fiber provide the greatest reduction in cardiovascular risk?
A
- Cereal fiber
- Proven functional fibers (psyllium and pectin)
25
How does fiber decrease cardiovascular risk?
Certain types of fiber bind cholesterol and prevent their absorption, decreasing cardiovascular risk and cholesterol
26
How does the requirement for fiber vary throughout the life cycle?
- 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
27
What dictates fluid intake?
Behaviour, and NOT thirst
28
What mechanisms allow for the detection of thirst?
- Decrease in body water (detected by a low blood volume)
| - Primarily sensed by an increase in sodium (detected by osmoreceptors in the brain)
29
What is the primary indicator of water status?
Plasma or serum osmolality
30
What is osmolality?
Measure of the osmoles per kilogram of solvent
31
What is osmolarity? Why is it not used to measure hydration status?
- Osmolarity is a measure of the osmoles per liter of solvent
- An addition of solutes may change the volume of a solution
32
What creates an osmotic load?
Metabolizing dietary protein and organic compounds, and varying intakes of electrolytes
33
What must the osmotic load be accommodated for?
Adequate water consumption
34
How does the inadequate replacement of fluids during exercise place strain on the cardiovascular system?
- Leads to dehydration and heat dissipation
| - Elevates core body temperature
35
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?
Given the extreme variability in water needs based on metabolism, environmental conditions, and activity
36
What DRI is used to estimate the requirement for water? How is it established?
- AI (Adequate Intake)
| - Based on the median total water intake from survey data
37
What factor is used to set the AI for water?
To prevent deleterious effects of dehydration, which include metabolic and functional abnormalities
38
How is the intake of water related to chronic disease?
- It is not
| - There is insufficient evidence to set an EAR for water-based reduction of chronic disease
39
What study provides a link between hydration status and type II diabetes?
- Elevated ADH (in a state of dehydration) leads to a higher fasting glycaemia in rats
- Hydration decreases adiposity
40
In physically-active adults, what does the requirement for water depend on?
- Sweat loss
| - Can exceed 10 liters per day
41
What is the UL for water?
- There is NO established UL for water because excessive fluid consumption is extremely rare
- Results in exertional hyponatremia
42
What DRI is used to estimate the requirement for calcium? How is it established?
- 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
43
How does the RDA for calcium differ between males and females?
The requirement is the same for all sexes
44
What form of phosphorus is found primarily? Where is it largely contained?
- Phosphate (PO4-)
| - Bones and teeth
45
What are the four functions of phosphorus? (4)
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)
46
What DRI is used to estimate the requirement for phosphorus? How is it established?
- RDA
| - Based on studies of serum inorganic phosphate concentrations (including the absorption efficiency of phosphorus)
47
What is the absorption efficiency of phosphorus?
60 to 65%
48
Where is magnesium largely contained?
50 to 60% of magnesium is found in bone
49
What are the functions of magnesium? (2)
1) Bone magnesium serves as a reservoir for maintaining normal extracellular magnesium
2) Required as a cofactor for over 300 enzymes
50
What DRI is used to estimate the requirement for magnesium? How is it established?
- RDA
| - Based on total body magnesium, assessed using balance studies
51
How does the RDA for magnesium vary between age groups?
The requirement for magnesium is higher in older individuals
52
What factors explain why the RDA for magnesium is higher in older subject?
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
53
Factorial modelling is used for the the requirement of which nutrient?
Iron
54
What are the four factors used in factorial modelling for the determination of the EAR of iron?
1) Basal iron losses
2) Menstrual iron losses
3) Fetal requirements in pregnancy
4) Growth
55
How does the percentage absorption vary with serum ferritin concentrations?
The percentage of absorption is inversely proportional to serum ferritin concentrations
56
What DRI is used to estimate the requirement for iron? How is it established?
- RDA
| - Based on the need to maintain a normal, functional iron status, while maintaining a minimal iron store
57
Differentiate heme and non-heme iron.
- 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
In a typical mixed diet, children over a year old, adolescents, and non-pregnant adults are assumed to possess a bioavailability of __% for iron.
18
59
How does the determination of the EAR for iron differ in men and women?
- Men: based on basal iron losses
| - Women: based on basal iron losses and menstrual losses
60
How does the requirement in iron for men differ from the requirement for pre-menopausal women? How does it differ after menopause?
- Requirement for iron is LOWER in men than in pre-menopausal women
- Requirement between men and post-menopausal women are SIMILAR
61
What DRI is used to estimate the requirement for potassium? How is it established?
- Adequate Intake (AI)
| - Based on the physiological functions of an adequate intake of potassium
62
What are the four physiological functions of an adequate intake of potassium? (4)
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
What characterizes a moderate potassium deficiency?
- High blood pressure
- Increased risk of kidney stones
- Cardiovascular diseases
64
How does hypokalemia affect sodium excretion?
- May result in decreased sodium excretion
| - Hypokalemia may result in cardiac arrhythmias, muscle weakness, and glucose intolerance
65
What is dietary potassium derived from fruits and vegetables normally associated with? What form is it?
- Organic anions (e.g. citrate)
| - Potassium citrate
66
What is the importance of organic anions that are associated with potassium?
- They are converted to bicarbonate after absorption
| - Bicarbonate may act as a buffer to neutralize acids from the diet
67
What occurs if there is a deficiency in bicarbonate precursors?
The body must use another type of buffer, which is normally drawn from the bone matrix, leading to increased bone turnover
68
Where is potassium largely contained?
Intracellularly
69
Are athletes recommended to increase their potassium intake? Why or why not?
- 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
What is the UL for potassium?
- 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
There is a wide variation in daily sodium requirements, particularly in which individuals?
Athletes, workers, and soldiers (i.e. individuals that sweat profusely)
72
What is the primary route of sodium loss in sedentary individuals?
Urine
73
Where is sulfur primarily contained?
- Certain amino acids (methionine, cysteine, cystine)
| - Component of essential compounds (e.g. glutathione)
74
What DRI is used to estimate the requirement for sulfur? How is it established?
- 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
What indicates that sulfur is not limiting when protein requirement is reached?
Urinary excretion of sulfate is adequate when an individual is consuming a sufficient quantity of protein
76
What is vitamin B1?
Thiamine
77
What is the major function of thiamine?
Functions as a coenzyme in the metabolism of carbohydrates and branched-chain amino acids
78
Which derivative of thiamine is required for carbohydrate metabolism?
Thiamine pyrophosphate (TPP)
79
Which enzyme is dependent on thiamine?
Transketolase, which requires TPP
80
What two factors determine the requirement for thiamine? (2)
1) The quantity required to achieve and maintain transketolase activity within RBCs
2) Without excessive thiamine excretion
81
What is the function of transketolase?
- Enzyme of the pentose phosphate pathway
| - The PPP generates NADPH, which functions as a reducing agent
82
Biochemical changes in which vitamins occur before the appearance of overt signs of deficiency?
- Thiamine (vitamin B1)
| - Riboflavin (vitamin B2)
83
What is thiamine deficiency? What does it affect?
- Beriberi
| - Affects the heart and circulatory system, and occurs solely when there is an extreme thiamine deficiency
84
What are three methods to analyze thiamine status? (3)
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
How does the requirement for thiamine vary between men and women?
The requirement for men is higher than women given differences in terms of energy utilization and body size
86
How does the requirement for thiamine vary with age?
- 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
How does the median intake of thiamine compare to the requirement?
The median intake is superior to the requirement
88
What is vitamin B2?
Riboflavin
89
What is the major function of riboflavin?
Functions as a coenzyme in various oxidation-reduction reactions, involved in several metabolic pathways and energy production
90
What three factors determine the requirement for riboflavin? (3)
1) Erythrocyte glutathione reductase activity coefficient
2) Concentration of riboflavin in RBCs
3) Urinary riboflavin excretion
91
The EAR of riboflavin for adults is derived from which three methods?
1) Studies of occurrence of signs and clinical deficiency
2) Biochemical values
3) Urinary excretion in relation to dietary intake
92
How does the requirement for riboflavin vary between men and women?
The requirement for men is higher than women given differences in terms of energy utilization and body size
93
How does the median intake of riboflavin compare to the requirement?
The median intake is superior to the requirement
94
Deficiencies for riboflavin are unlikely. When would they be observed?
In the case of severe alcohol consumption
95
What is vitamin B3?
Niacin
96
What is the major function of niacin?
- 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
What determines the requirement for niacin?
Urinary excretion of niacin metabolites, as an excess of niacin is methylated in the liver for excretion in urine
98
What adjustments are made for niacin in terms of bioavailability?
There are no adjustments made, but the requirement is expressed as niacin equivalents (NEs)
99
What are the two sources of niacin? (2)
- Conversion of tryptophan to niacin
| - Acquisition of niacin from the diet
100
What is the efficiency of conversion of tryptophan to niacin?
60:1 (tryptophan to niacin)
101
A deficiency in which nutrients may decrease the conversion of tryptophan to niacin, increasing the requirements of exogenous niacin?
- Iron
- Riboflavin
- Pyridoxine
102
Which nutrients possess a large coefficient of variation?
- Niacin (15%)
| - Vitamin A (20%)
103
Why is the coefficient of variation of niacin large?
Due to the individual variability in terms of the conversion efficiency of tryptophan to niacin
104
How does the median intake of niacin compare to the requirement?
The median intake is much superior to the requirement
105
What is vitamin B6?
Pyridoxine and related compounds
106
What is the major function of pyridoxine?
Serves as a coenzyme in the metabolism of amino acids, glycogen, and sphingoid bases
107
What determines the requirement for pyridoxine?
The maintenance of adequate blood 5'-pyridoxal phosphate levels, which is the active form of vitamin B5
108
What is vitamin B9?
Folate
109
What is the major function of folate?
Functions as a coenzyme in single-carbon transfers in the metabolism of nucleic and amino acids
110
What two factors determine the requirement for folate? (2)
1) Erythrocyte folate
| 2) Blood homocysteine and folate concentrations
111
Why are dietary folate equivalents (DFEs) required?
To adjust for the fact that folate from food is 50% less bioavailable than folic acid from supplements or fortified foods
112
What is 1ug of DFE equivalent to in terms of food folate, folic acid, and a supplement taken on an empty stomach?
- Food folate: 1 ug
- Folic acid: 0.6 ug
- Supplement taken on an empty stomach: 0.5 ug
113
What is the major function of vitamin B12?
- Coenzyme for methyl transfer reactions
- Homocysteine to methionine
- L-methylmalonyl-coenzyme A to succinyl-CoA
114
What two factors determine the requirement for vitamin B12? (2)
1) The maintenance of hematological status
| 2) Normal blood vitamin B12 values
115
What is vitamin B7?
Biotin
116
What is the major function of vitamin B7?
Functions as a coenzyme in bicarbonate-dependent carboxylation reactions
117
Which B-vitamins possess an AI?
- Biotin (vitamin B7)
| - Pantothenic acid (vitamin B5)
118
What is the major function of choline?
Precursor for acetylcholine, phospholipids, and the methyl donor betaine
119
What DRI is used to estimate the requirement for choline? How is it established? What factor does it take into consideration?
- AI
- Assessed by serum alanine aminotransferase levels
- The prevention of liver damage
120
What does a deficiency in choline cause? What may that lead to?
- Muscle damage and abnormal fat deposition in the liver
| - Non-alcoholic fatty liver disease (NAFLD)
121
What does the assembly and exportation of VLDLs require? What occurs if it is deficient?
- Phosphatidylcholine
- If choline is deficient, phosphatidylcholine may not be synthesize, which causes lipids to accumulate, leading to NAFLD
122
How does phosphatidylcholine play a role in lowering blood cholesterol?
Phosphatidylcholine is required by LCAT, which converts cholesterol into inactive cholesteryl esters
123
How is phosphatidylcholine generated?
Phosphatidylethanolamine is trimethylated from SAM by phosphatidylethanolamine methyltransferase, producing phosphatidylcholine
124
How is choline generated through de novo synthesis?
Phosphatidylcholine is catabolized by phospholipases, which generates choline
125
The demand for dietary choline is modified by metabolic methyl-exchange relationships between which nutrients?
Choline and methionine, folate, and vitamin B12
126
Which study demonstrates that de novo synthesis of choline is NOT sufficient?
Healthy men with normal folate and vitamin B12 status fed a choline-deficient diet demonstrated decreased plasma choline and liver damage
127
What DRI is used to estimate the requirement for choline? What is particular about the requirement for choline and certain life stages?
- Adequate Intake (AI)
| - The requirement for choline may be met through de novo synthesis at certain life stages
128
What two factors determine the requirement for choline?
1) Methionine and folate availability
| 2) Gender, pregnancy, lactation, and stage of development
129
How does the requirement for choline vary between men and women?
The requirement is higher for men than in women
130
How does the requirement for choline vary between age groups?
Choline transport across the BBB may decrease, but there is no adjustment
131
What is vitamin B5?
Pantothenic acid
132
What is the major function of pantothenic acid?
Component of coenzyme A and phosphopantetheine, implicated in fatty acid metabolism
133
Why is a deficiency in pantothenic acid rare? When would it occur?
- 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
What DRI is used to estimate the requirement for pantothenic acid? What factor is it based on?
- Adequate Intake (AI)
| - Intake to replace urinary excretion of pantothenic acid
135
How is the AI of pantothenic acid determined?
- The midpoint of the usual intake of vitamin B5
| - There is no evidence that suggests that this intake is inadequate
136
What is the major function of vitamin C?
- Functions as a water-soluble antioxidant
| - Cofactor for enzymes involved in the biosynthesis of collagen, carnitine, and neurotransmitters
137
What two factors determine the RDA for vitamin C? (2)
1) To maintain near-maximal neutrophilic concentration
| 2) Minimal urinary excretion of vitamin C
138
What four factors explain why the RDA for vitamin C is lower in women than in men? (4)
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
How does blood vitamin C vary for the elderly population? Why?
- Blood vitamin C is lower in the elderly
| - Due to poor dietary intakes, or chronic disease
140
Which population group requires a higher requirement of vitamin C? Why?
- Smokers
| - Due to an elevated pro-oxidant environment
