Fat,CHO, water and micronutrients for adults Flashcards
(136 cards)
1
Q
Why omega 6 to omega 3 is very important
A
Eicosanoid products derived from omega-6 PUFAs (such as prostaglandin (PG) E2 and leukotriene (LT) B4 synthesized from arachidonic acid (AA)) are more potent mediators of thrombosis and inflammation than similar products derived from omega-3 PUFAs
omega 3 and omega 6 compete for the same enzyme desaturase
2
Q
Requirements for omega 6 and omega 3 are set based on
A
-AI for C18:2n-6 and C18:3n-3 established based on highest median intakes in US populations where no evidence of deficiency
3
Q
Why fatty acids requirements go down with age (in elderly)
A
As body weight goes down, then the requirement goes down
And their intake is lower ( caloric intake)
4
Q
What is the rate fo glucose production in overnight fasted adults
A
2.8-3.6 g/kg/day from glycogen and gluconeogenesis
- ~ 210 to 270 g/d in a 70 kg man (without using ketoacids)
- ~50% from glycogenolysis & 50% from gluconeogenesis
5
Q
Min CHO determined by
A
- by the brain’s requirement
- Uses glucose almost exclusively for its energy needs
- ~110-140 g/d in adults
6
Q
What happens in subject with CHO metabolism in starvation
A
- In subjects fully adapted to starvation
- Ketoacid oxidation: ~ 80% of brain’s energy requirements
à only 22 to 28 g/d of glucose required
7
Q
CHO EAR is based on and what assumptions it makes
A
- EAR based on amount that would provide the brain with adequate supply of glucose
- Without additional glucose production from protein or TG
- Without ↑ketones greater than observed after o/n fast
- This assumes:
- Energy sufficient diet with AMDR of CHO (45 – 65%)
- à glucose not limiting to the brain (no use of ketoacids)
8
Q
Is there difference in oxidation between age and sex in CHO?
A
There is no proof
9
Q
Amount of dietary CHO to decrease risk of chronic disease
A
Unknown
10
Q
Definitions of fiber
A
•Nondigestible CHOs & lignin intrinsic & intact in plants
11
Q
What is functional fiber and what is total fiber
A
- Functional fiber = isolated, nondigestible CHOs shown to have beneficial physiological effects in humans
- Total fiber = Dietary Fiber + Functional Fiber
12
Q
What is resistant starch
A
Resistant starch- CHO rich source ( like pasta) part of the pasta is not broken down in upper digestion and it is the source of fermentation for bacteria in the colon
13
Q
How can you cook potatoes ,so there will be more resistant starch
A
Cooked and then cooled
14
Q
Benefits of fiber
A
Fiber- satiety, protection from obesity and weight gain (especially from cereal), in part because of satiety and in addition because they have a probiotic effect -> the greater the diversity, greater the protection
Cereal fiber increases bacterial diversity which is associated with a variety of health benefits and conversely a low bacterial diversity leading to unwanted weight gain or increased disease risk
- Ameliorate constipation & diverticular disease
- Fuel for colonic cells
- ↓ blood [glucose] and [lipids]
- Source of nutrient-rich low-energy foods à satiety & ↓risk of obesity
15
Q
What is the best food to romote bacterial diversity
A
Wheat bran
A simple dietary modification to consume a daily bowl of a high fiber breakfast appears to have a positive impact on the gut microbiota for health adults which can be measured within the first 3 weeks
As little as 6 g of wheat fiber was shown to produce significant positive benefits to the gut microbiota,
16
Q
How fiber can help with diverticulosis
A
Provide bulk and decrease the transition time
17
Q
How fiber can be fuel for colonic cells if fiber is not digested
A
SCFAs from fermentation can be used as a fuel (butyrate) and it has been linked with decreased risk of colonic cancer
18
Q
Why fiber requirements go down with age?
A
Due to decrease in caloric requirements
19
Q
what kind of fiber has the greatest effect on CHD risk
A
Cereal fiber & proven Functional Fibers, including psyllium & pectin
-Certain kinds of fiber bind cholesterol & prevent absorption -> ↓CHD risk
20
Q
Why there is a recommendation for fiber, but no EAR
A
- Strong data on relationship between dietary fiber intake and CHD risk -> use to set intake recommendation.
- Benefit of ↑Total Fiber intake: continuous across range of intakes à EAR cannot be made.
21
Q
What nutrient is the largest constituent of the human body
A
Water
22
Q
Water is essential for and what are the components for total water intake
A
- Essential for cellular homeostasis and life
- Total water intake = drinking water + water in beverages (80%) + water that is part of food (20%)
23
Q
What happens if you take too much water and what happns to elderly with too little intake and what adivce can be given to avoid it
A
- Elderly population is less sensitive to thirst and thus can become dehydrated and pose risk to heart attack and platelet aggregation to blood clots
- A glass of water before bedtime can decrease the chance of stroke
- If too much: risk of edema and oxygen cannot rich the tissues
- With dehydration you have more risk of falling due to low pressure
24
Q
Do we drink by thrist or something else and do we drink enough
A
Most healthy adults consume enough water and behavior daily fluid intake , not thirst
25
When you have thirst signals
* Thirst:
* ↓Body water (sensed as a low blood volume)
* ↑ [Na] (primarily sensed by cells of the brain)
26
What hormone plays a role in water levels in the body? what are the risks for chronic dehydration? How water, ADH and insulin resistance are connected
ADH plays a role in keeping water inside the body
One risks for chronic dehydration is decreased metabolic response to dehydration ( when high CHO intake-\>chronic water dehydration-\> not enough vasopressin secreted -\> insulin resistance
ADH acts on insulin receptors blunting the action
27
How water status is assessed
* Hydration status (assessed by plasma or serum osmolality) = primary indicator of water status
* Physical activity, environmental and dietary conditions: substantial influences on water needs
28
How dietary factors can influence water requirements
* Dietary factors also influence water requirements
* Osmotic load created by
* Metabolizing dietary protein & organic compounds
* Varying intakes of electrolytes
29
Is there a definite daily water requirenment for a given person?
No, single requirement
30
Dehydration will lead to
- \>Impaired heat dissipation
- \>↑Body core temperature
- \>↑ strain on CV system
31
Is there an evidence of water intake and chronic diseases
Decreased intake might have an association, but no sufficient evidence
32
Is there an UL for water and what can happen if you drink more than needed
- XS fluid consumption -\> hyponatremia. Rare occurrence -\> no UL
- Acute water toxicity: fluid consumption \> kidney’s max excretion rate (0.7-1.0 L/h)
33
Is Ca a risk nutrient for elderly?
Most elderly do not consume 100% of the recommendation.
-↑ risk of osteoporosis, HTN, colon cancer
34
What is an RDA for calcium and how it was determined
* Relies on Ca balance studies
* -\> Intakes to achieve small gains in BMC
* RDA = 1000 mg (25 mmol)/day in adult males and females ages 19 – 50 years
* Based on clinical trial data showing an ↑ in bone mineral density in women provided with intakes of 1000 mg/d
35
Why phosphorus is important and how it is found in our body
* Occurs as PO4
* Essential constituent
* 85% of adult body P is in bone
* Occurs as phospholipids, nucleotides & nucleic acids
* Buffers acid or alkali XS to maintain normal pH
* Temporary storage & transfer of energy derived from metabolic fuels
* Required for phosphorylation, the activation of many catalytic proteins
36
Requirements for P is set according to and do we consume enough
* EAR based on the lower end of the normal adult [Pi] range
* 0.87 mmol/liter [2.7 mg/dl]
* -\> ingested intake value of ~580 mg (~19 mmol/d)
37
Absorption efficiency of phosphorus
60-65% on mixed diets
38
What are dashed lines and curves
## Footnote
- Dashed horizontal lines = upper & lower limits of the normal range
- Dashed curves = relationship between serum Pi and ingested intake for absorption efficiencies ~15% higher and lower than average
39
why do we need magnesium
* 50 – 60 % in bone
* 1/3 skeletal Mg exchangeable as reservoir for maintaining normal extracellular [Mg]
* Required cofactor for over 300 enzyme systems
40
EAR for Mg is based on
Balance studies, maintenance of total body Mg
41
Why requirement for Mg rise with age
- With age, ↑ diets high in fiber (interactions with phytates)
- Renal function declines with age -\> ↑EAR
42
Where we cna find iron in the body and why it is important
* Component of a number of proteins (e.g. enzymes, Hb)
* Almost 2/3 in Hb (erythrocytes)
* 15% in myoglobin in muscle
* Variety of enzymes necessary for oxidative metabolism and many other critical functions
43
How requirement for iron was set
* The components of Fe requirement used as factors include
* Basal iron losses (obligatory loss in feces, urine, sweat, skin cells)
* Menstrual losses
* Fetal requirements in pregnancy
* Growth: expansion of blood volume, and/or ↑ tissue and storage iron
44
EAR for iron is based on
-Body Fe store regulates absorption (% absorbed inversely proportional to serum [ferritin])
•Based on the need to maintain a normal, functional [Fe]
-Maintenance of minimal Fe store (serum [ferritin] cutoff = 15 ug/L)
* EAR: set by modeling the components of Fe requirements,-\> because iron requirements are skew, so not normally distributed, simple addition cannot be done-\> factorial modelling
* Estimating req’t for absorbed Fe at 50th percentile,
* Upper limit of 18% absorption
45
Major factor for iron asbsorption is
Bioavailability
46
Where you can find heme and nonheme iron and how they are absorbed
* Heme iron
* Meat, poultry, and fish
* Always well absorbed, slightly influenced by dietary factors
* Nonheme iron
* Present in all foods
* Strongly influenced by solubility & interaction with other meal components
47
What is the typical mixed diet and what iron bioavailability their
18%
2/3 heme, 1/3 non heme
48
For men and women EAR is based on
* Men: Basal Fe losses
* Women: Basal iron losses + menstrual losses
49
Why K intake is important
* Adequate potassium intake important in:
* Lowering blood pressure
* Blunting the adverse blood-pressure effects of salt intake
* Reducing the risk of kidney stones
* Potentially reducing bone loss
50
Is K AI or EAR
The committee concludes that none of the reviewed indicators for potassium requirements offer sufficient evidence to establish Estimated Average Requirement (EAR) and Recommended Dietary Allowance (RDA) values. Given the lack of evidence of potassium deficiency in the population, median intakes observed in an apparently healthy group of people are appropriate for establishing the potassium Adequate Intake (AI) values.
51
Is there a UL for K
No
52
How much sodium usual det provide, where usually Na is excreted
* Diet providing an average of ~1.5 g/day
* Can meet recommended intakes for other nutrients in a Western-type diet.
* Allows for XS Na loss in sweat by unacclimatized persons exposed to high temperatures or who are moderately physically active
- Wide variation in daily Na needs
- Especially athletes, workers, soldiers
- Sedentary individuals: primary route of loss = urine
- Kidneys can conserve or excrete Na as needed
53
1.5 g/day is how much salt? and is there an UL? and special recommendations for physically active adults
Sedentary : UL- 2.3g/day
1.5 g/day-3.8 g of salt
Athletes excrete more due to sweat loss, no UL
54
How Ul and AI is set for Na
In the absence of a specific indicator of sodium adequacy, the sodium AI for adults is based on the lowest levels of sodium intakes evaluated in randomized controlled trials for which there was no evidence of deficiency and also drew on evidence from the best-designed balance study.
There is sufficient evidence to characterize the relationship between sodium intake and risk of chronic disease. The CDRR is established using evidence of the beneficial effect of reducing sodium intake on cardiovascular disease risk
55
How AI for Na for children and infants are derived
The sodium AIs for children are extrapolated from the adult values based on Estimated Energy Requirements. For infants, the AIs are derived from estimates of sodium intakes in breastfed infants
56
Function of sulfur in the body
* Present in a.a.’s (Methionine, Cysteine, Cystine) in proteins
* Component of essential compounds
* E.g. glutathione
57
Sources of sulfur in the diet, is there a requirement
* Sources: S-containing a.a. from protein digestion
* No intake requirement established
- North American diet: adequate-to-excessive protein à no need to set sulfate RDA
- No EAR or AI, when sulfur AAs requirements are met
58
Thiamin function
•Functions as a coenzyme in the metabolism of CHO & branched-chain a.a.
59
Thiamin status is assessed by
- Erythrocyte transketolase activity
- [Thiamin] & its phosphorylated esters in blood
- Urinary thiamin excretion under basal conditions or after thiamin loading
60
Thiamine requirement are set by
Recommended Dietary Allowance (RDA) for thiamin combines erythrocyte transketolase activity, urinary thiamin excretion, and other findings.
61
are there any biochemical changes before ouvert signs of deficiency
-Biochemical changes in thiamin status occur before overt signs of deficiency.
62
Is there an UL for thiamine?
Data concerning adverse effects are not sufficient to set a Tolerable Upper Intake Level (UL) for thiamin.
63
If activity of RBC transketolase was increased by \_\_\_%, then there was thiamine deficiency
20%
64
RBC transketolase needs to be ___ in order to be active
phosphorylated
65
Why there is difference in thiamin requirement between men and women
* -\>Small (10%) adjustment to estimated req. for men vs. women
* ≠ energy utilization
* ≠ size
66
Do american population consume enough thiamine?
Yes
67
Riboflavin functions
• coenzyme in numerous oxidation-reduction reactions
68
Requirement and EAR for riboflavin are based on
* Erythrocyte glutathione reductase activity coefficient
* RBC [riboflavin]
* Urinary riboflavin excretion
EAR for adults derived from:
* Studies of occurrence of signs of clinical deficiency
* Biochemical values
* Urinary excretion in relation to dietary intake
69
Can you find out about riboflavin defiiency in advance?
•Biochemical changes in riboflavin status occur before appearance of overt signs of deficiency.
70
Do people consume enough riboflavin? is there a UL
Consume enough, no UL
71
Riboflavin and thiamine deficiencies can lead to what disease
Thiamine - beriberi
riboflaviin- fatigue, swollen throat, blurred vision, and depression.
72
Functions of niacin
•cosubstrate or coenzyme for H- transfer (dehydrogenases)
73
on what bases RDA for niacin is set? is there UL?
The Tolerable Upper Intake Level (UL) for niacin for adults is 35 mg/day, which was based on flushing as the critical adverse effect.
The primary criterion used to estimate the Recommended Dietary Allowance (RDA) for niacin is the urinary excretion of niacin metabolites.
74
In what units niacin requirement is set and why
No adjustment is made for bioavailability, but the requirement is expressed in niacin equivalents (NEs), allowing for some conversion of the amino acid tryptophan to niacin.
75
in canada do we consume enough niacin?
Yes
76
function of B6
Vitamin B6 (pyridoxine & related compounds): coenzyme in metabolism of a.a.’s, glycogen, & sphingoid bases
77
Primary criterion to estimate RDA for B6
maintenance of adequate blood 5'-pyridoxal phosphate levels
78
Is there a UL for pyrodixine
yes, 100 mg/day
79
Niacin deficiency will cause
Pellagra is a disease caused by a lack of the vitamin niacin (vitamin B3). Symptoms include inflamed skin, diarrhea, dementia, and sores in the mouth.
DEMENTIA-\>ELDERLY
80
Functions of folate
a coenzyme in single-carbon transfers in the metabolism of nucleic and amino acids.
81
Indicator to set RDA for folate
•Erythrocyte folate,
Blood [homocysteine] and [folate]
82
What units are ised for folate requirement and why
* RDA based on dietary folate equivalents (DFEs)
* DFEs adjust for ~ 50% lower bioavailability of food folate vs. folic acid
83
•1 μg of DFE=
= \_\_of food folate
= ___ μg folic acid (fortified food or supplement with meals)
= ___ μg of supplement taken on an empty stomach
= 1 μg of food folate
= 0.6 μg folic acid (fortified food or supplement with meals)
= 0.5 μg of supplement taken on an empty stomach
84
Folate is a cofactor for
Methionine synthase
85
The most bioavailable form we can get from
supplement on empty stomach
86
Why requirement for folate \>19 years is at 400 micrograms
if unplanned prgnancy to prevent neural tube defect
87
Vitamin B12: functions
•Coenzyme for methyl transfer rx: homocysteine à methionine
And L-methylmalonyl-coenzyme A (CoA) à succinyl-CoA
88
RDA based on for vitamin b12
* Maintenance of hematological status
* & normal blood vitamin B12 values
89
ow can you find out that you are b12 deficient?
L-methylmalonic acid in the urine
90
Why it is important to have both nomal b12 and folate
If you have high folic acid intake, then you will not see the effect on reduction of RBCs if deficient in B12, so more hard to diagnose B12 deficiency
91
Functions of biotin
Functions: coenzyme in bicarbonate-dependent carboxylation rxs
92
Biotin requirement
Values extrapolated from the data for infants and limited estimates of intake are used to set the Adequate Intake (AI) for biotin because of limited data on adult requirements.
No UL , of more than needed-\>excreted
93
Function of choline
Precursor for acetylcholine, phospholipids, and the methyl donor betaine
94
Primary criterion used to estimate the requirement for choline
The primary criterion used to estimate the Adequate Intake (AI) for choline is the prevention of liver damage as assessed by measuring serum alanine aminotransferase levels
95
Why there is a UL for choline
The critical adverse effect from high intake of choline is hypotension, with corroborative evidence on cholinergic side effects (e.g., sweating and diarrhea) and fishy body odor.
96
How choline is present in the diet
* Free choline
* Bound as esters (phosphocholine, glycerophosphocholine, sphingomyelin, phosphatidylcholine)
97
How Phosphatidylcholine (lecithin) plays a role in lowering cholesterol and homocysteine
- Phosphatidylcholine (lecithin) – can lower blood cholesterol.
- Lecithin-cholesterol acyltransferase: role in removal of cholesterol from tissues.
- Choline or betaine have been used to lower plasma [homocysteine]
98
Choline can be synthesized de novo, what nutrients are needed for that
methionine, folate, and vitamin B12
99
Is choline de novo synthesize is enough?
de novo synthesis rates are not adequate to meet the demand for the nutrient when the other nutrients are available in amounts sufficient to sustain normal growth and function. Healthy men with normal folate and vitamin B12 status fed a choline-deficient diet have diminished plasma choline and phosphatidylcholine concentrations and develop liver damage
100
So, the requirement for choline is set by which criteria (AI, EAR, etc.)
•Only 2 published studies in healthy humans; male subjects only & 1 level of intake tested
-\> Insufficient data for EAR
Choline requirement is influenced by
* Methionine and folate availability
* Gender, pregnancy, lactation, stage of development
-\>AIs are set for choline, but requirement could be met by endogenous synthesis at some life stages
101
What is the problem with AI for choline for different ages and genders
- Intake of 500 mg/d (4.8 mmol/d; ~ 7 mg/kg/d) prevented alanine aminotransferase abnormalities in healthy men.
- AI estimate based on a single study à uncertain
- Women: assumed that data from men can be used
- Elderly: no adjustment; although transport across the BBB may ↓
102
Why pathothenic acid is important
Component of coenzyme A & phosphopantetheine, (fatty acid metabolism)
103
When can you become deficient in pathothenic acid
•Widely distributed in foods
Deficiency: semisynthetic diets or antagonist to the vitamin
104
Recommendations for pantothenic acid are based on
The primary criterion used to estimate the Adequate Intake (AI) for pantothenic acid is intake adequate to replace urinary excretion.
There is not sufficient scientific evidence on which to base a Tolerable Upper Intake Level (UL) for pantothenic acid.
105
Functions of vitamin C
* Water-soluble antioxidant
* Cofactor for enzymes involved in biosynthesis of collagen, carnitine, & neurotransmitters
106
RDA for vitamin C is set based on
* Maintain near-maximal neutrophil concentration
* Minimal urinary excretion of ascorbate
107
Why vitamin C requirement are lower for women vs men, why smokers higher
Women:
- Smaller lean body mass
- Less total body water
- Smaller body size
- Women maintain higher plasma [ascorbate] then men at a given intake
Because smoking increases oxidative stress and metabolic turnover of vitamin C, smoking produced more free radicals
108
Difference between adults and elderly in vitamin C absorption
- Aging: no consistent differences in absorption or metabolism
- Low blood [vit.C] in elderly may be due to poor dietary intakes, chronic diseases, etc
109
Vitamin A is important for
* Normal vision
* Gene expression
* Reproduction
* Embryonic development
* Growth
* Immune function
110
In what forms you can find vitamin A and in what units requirements are set
* Preformed vitamin A: some animal-derived foods
* Provitamin A carotenoids: darkly colored fruits & vegetables, oily fruits & red palm oil
* -\> Retinol activity equivalents (RAE) used for setting vitamin A requirements
111
What is the leading cause of mortality and morbidity in children in developing countries
Lack of vitamin A
112
Forms of carotenoids that are convertable to vitamin A and not
The most prevalent carotenoids in North American diets include the following: α-carotene, β-carotene, lycopene, lutein, zeaxanthin, and β-cryptoxanthin. The structures of these carotenoids are shown in Figure 8-1. Three of these carotenoids, namely α-carotene, β-carotene, and β-cryptoxanthin, can be converted into retinol and are thus referred to as provitamin A carotenoids. Lycopene, lutein, and zeaxanthin have no vitamin A activity and are thus referred to as nonprovitamin A carotenoids.
* Dietary provitamin A carotenoids
* β-carotene RAE = 12 μg
* α-carotene RAE = 24 μg
* β-cryptoxanthin RAE = 24 μg
113
Is there requriements for carotenoids ( not vitamin A)
Although no DRIs are proposed for β-carotene or other carotenoids at the present time, existing recommendations for increased consumption of carotenoid-rich fruits and vegetables are supported.
There are lycopene receptors in the eye, so might be helpful to set recommendation for those as well, though not converted to vitamin A
114
EAR for vitamin A is based on
* EAR based on amount of dietary vitamin A required to maintain a given body-pool size in well-nourished subjects
* -\> Assure vitamin A reserves to cover increased needs during periods of stress and low vitamin A intake
115
Why men have higher vitamin A requirements
Because of higher body size
116
Vitamin D is importnat for absorption of what nutrients
Calcium and phosphate
117
Other than Ca and p roles of vitamin D
Potent antiproliferative (anticancer) and prodifferentiation effects in a variety of tissues (brain health)
but data is controversial
118
2 major physiological relevant forms of vitamin D
* Vitamin D2 (ergocalciferol; yeast & plant sterols)
* Vitamin D3 (cholecalciferol; from 7-dehydrocholesterol)
* Found naturally in very few foods but is synthesized in the skin
119
AIs for babies for vitamin D are based on
Breast milk and some other dietary sources
120
DO people only in northern altitudes suffer from insufficient vitamin D from the skin?
No , in the south people tend to stay in doors because of the heat
121
What is the biomarker of vitamin D status?
serum 25-hydroxyvitamin D
122
insufficint vitamin D will lead to
Rickets
overcame in canada because of food fortification
123
what is RDA basis for vitamin D and is there UL?
on maintaining skeletal health and have been set using the assumption that sun exposure is minimal. Available data were used to link specified serum levels of 25OHD with total intakes of vitamin D under conditions of minimal sun exposure in order to estimate DRIs.
Total vitamin D intake should remain below the level of the new UL to avoid possible adverse effects. Long-term intakes above the UL increase the risk of adverse health effects.
124
Vitamin E functions
•non-specific chain-breaking antioxidant preventing the propagation of lipid peroxidation, non specific reducers
inserts in membrane
125
what are forms that have vitamin E antioxidant activity and what s there general structure
- α-tocopherol, trimethyl
- β- or γ-tocopherols, dimethyl
- δ-tocopherol, monomethyl
- Substituted, hydroxylated ring system (chromanol ring) with a long saturated (phytyl) side chain.
126
What is the other form of tocopherols
tocotrienols
## Footnote
- 4 tocotrienols (α-tocotrienol, trimethyl; β- or γ-tocotrienols, dimethyl; and δ-tocotrienol, monomethyl)
- Unsaturated side chain
127
Based on what chemical recommendation for vitamin e is set
alpha tocopherol most bioactive, inserts itself more quickly in the membrane
saturated phytyl chain, 3R, ring has 3 methyl groups
128
What alpha tocopherol apart from natural is ok for substituting
occuring form (RRR-) and the other three synthetic 2R-stereoisomer forms (RSR-, RRS-, and RSS-) of α-tocopherol for purposes of establishing the human requirement for vitamin E.
other forms are not converted to alpha tocopherol
129
what vitamin E form is added to foods
-Synthetic forms in fortified foods & supplements
Esters of either RRR- or synthetic mixture (all rac-) forms
130
how RRR alpha tocopherol can be synthesized
-RRR-α-Tocopherol can be derived by methylating γ-tocopherol isolated from vegetable oil.
131
what is all ra-alpha tacopherol and what is it activity
mixture of half 2-R and 2-s forms
## Footnote
-\>all rac-α-tocopherol: ½ the activity of RRR-α-tocopherol (foods)
½ the activity of other 2R forms
•RDA = 15 mg/d of α-tocopherol
= 15 mg/d of RRR-α-tocopherol
= 15 mg/d of the 2R-stereoisomeric
= 30 mg/d of all rac-α-tocopherol
132
Why other forms other than 2-R stereoisomeric forms cannot estimate the requirement
* Plasma [vit. E] forms: dependent on the affinity of hepatic α-tocopherol transfer protein (α-TTP)
* Not true for either synthetic SRR-α-tocopherol or natural γ-tocopherol
Efficiently absorbed (chylomicrons) à liver
BUT poorly packaged into lipoproteins for delivery to peripheral tissues
* 2S-stereoisomeric forms, other tocopherols (β-, γ-,and δ-tocopherol) and tocotrienols fail to bind with α-TTP
* -\>Not used to estimate the requirement
133
Vitamin K role in the body
Coenzyme during synthesis of the biologically active form of a number of proteins involved in blood coagulation and bone metabolism
134
AI for vitamin K is set based on
the highest median intake data
135
forms of vitamin K
* Phylloquinone: major form of vitamin K in the diet
* Menaquinones produced by bacteria in the lower bowel
136
How vitamin K is involved in bone formation
Osteocalcin originates from osteoblastic synthesis and is deposited into bone or released into circulation, where it correlates with histological measures of bone formation. The presence of 3 vitamin K-dependent γ carboxyglutamic acid residues is critical for osteocalcin’s structure, which appears to regulate the maturation of bone mineral.
without vitamin K-\> no methylation of osteocalcin
