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19 - Vitamins Flashcards

1
Q

How was the RDI/amount of vitamins we need established initially?

A

Unethically. Early studies on the amount of an individual vitamin an individual needed was done in concentration camps during the 2nd world war. Individuals were starved of specific groups of food, they would see the consequences/symptoms of this, and then investigate what nutrients these foods had, and then supplement the individuals with these specific nutrients

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2
Q

Why is it had to determine how much of an individual vitamin individuals need?

A

Vitamins are found in a complex matrix (food) - we don’t consume singular nutrients so it is hard to get a single diet WITHOUT a single nutrient to see its affect and how much of it we need

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3
Q

Are RDIs/nutrient reference values accurate?

A

No they are arbituary but we use the best information we have.

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4
Q

How are RDIs for nutrients/vitamins determined?

A

Nutrient requirements for individuals form a bell shaped curve i.e. there is a range of nutrient requirements depending on the individual and there is an assumption that for a population an individual will follow that curve. The RDIs are set at the high point of the bell curve so that it will cover 98% of that population requirements and for most will be much more than they need - as it is so high, some ones intake is often instead compared to the average daily intake of that population (middle of bell curve)

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5
Q

Distinguish between macro and micronutrients?

A

macronutrients give us energy micro don’t

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6
Q

If we fall below the RDI are we in danger of deficiency, and if we go above is it beneficial for our health?

A

Naive view
In reality, for a margin above and below the RDI/Adequate Intake there is a safety intake of nutrients. At the border of the safety areas is marginal,, and above/below this there is a danger of deficiency and toxicity.

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7
Q

Why are vitamins toxic in large quantities above RDI?

A

They are powerful chemicals and become toxic

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8
Q

Do we often see nutrient deficiencies in NZ?

A

Don’t often see single nutrient deficiencies caused by inadequate diets (primary deficiencies) but we DO see nutrient deficiencies in patients caused by other conditions (secondary deficiencies)
> may see scurvy in homeless

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9
Q

What is an example of a condition that will cause secondary nutrient deficiency?

A

Malabsorption

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10
Q

What are the water soluble vitamins and where do they come from?

A

The B vitamins (including folate and B12/cobalamin) and vitamin C

  • thiamin
  • riboflavin
  • niacin etc.

Come from a VARIETY of souces

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11
Q

What are the fat soluble vitamin and where do they come from?

A

Vitamin A - retinol, carotenes
Vitamin D - cholecalciferol
Vitamin E - tocopherols, tocotrienes
Vitamin K -

Come from foods that contain FAT

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12
Q

Where does vit A come from?

A

Animal and dairy fats

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13
Q

Where does vit D come from?

A

Fish oils and the sun

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14
Q

Where does vit E come from?

A

Plant based sources

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15
Q

Where does vit K come from?

A

Bacteria in the large bowel synthesise most of the vitamin K we absorb but also comes form leafy greens

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16
Q

Compare the absorption of water and fat soluble vitamins

A

fat - need to first be transported WITH fat into the LYMPH, and then into the venous blood system.
water - are directly absorbed and travel freely in the blood at the SI

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17
Q

Who are at risk of not getting enough fat soluble vitamins?

A

People with fat malabsorption because they absorbed with fats into the lymph
And people with fat digestion problems (only smaller FA molecules CAN get absorbed) for example people with not enough bile/liver synthesis or a blocked bile duct or pancreatic duct or pancreatic enzymes affected

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18
Q

Compare transport of fat and water soluble vitamins?

A

fat - require protein carriers

water - travel freely in the blood

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19
Q

compare storage of fat and water soluble vitamins?

A

fat - GOOD at storing fat soluble vitamins as are stored with fat in the LIVER (don’t have to consume as regularly)
water - water soluble vitamins are not stored. They travel freely around the body and have a short half life/ and we excrete them rapidly through the urine. Means we have to consume them regularly

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20
Q

Where are fat soluble vitamins stored?

A

With fat in the liver

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21
Q

Compare the toxicity of fat and water soluble vitamins?

A

fat - as they are stored well it is LIKELY that when consumed as supplements they can reach toxicity levels
water - LESS LIKELY to become toxic with supplements

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22
Q

Which type of vitamin is more likely to become toxic when consumed via supplements

A

Fat soluble - do not readily excrete and already have a good store in the body

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23
Q

Do borocca and vitamin C supplements contain the RDI of vitamin C?

A

They contain MUCH more and RDI is already at the extreme end of the bell shaped distribution for the populations needs. Over a short period of time this will do no harm as it is readily excreted but high doses of vit C MAY cause damage long term

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24
Q

Compare the requirements of of fat and water soluble vitamins?

A

water - need in frequent doses i.e. every 1-3 days

fat - need in less frequent but periodic doses (weeks or months)

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25
Compare the excretion of fat and water soluble vitamins?
water - kidneys detect and excrete excess in urine | fat - less rapidly excreted and tend to remain with fat in fat storage sites
26
What does knowing the site of absorption help us with?
Means if a patient has had surgery to part of the GI tract, injury, or damage then we know what nutrients they may be at risk of deficiency/malabsorption of as they can't absorb them adequately
27
Where is B12 absorbed?
terminal ileum along with bile salts
28
What is absorbed at the stomach?
Ethanol and water
29
What 5 things affect the bioavailability of nutrients?
1. The efficiency of digestion and transit time 2. Previous intake and an individuals nutrition status can affect the bio-availability of nutrients 3. The other foods consumed simultaneously 4. The food preparation method 5. Source of the nutrient i.e. synthetic vs natural
30
Give an example of how efficiency of digestion and transit time may affect the bioavailability of nutrients
Efficiency of digestion - malabsorption syndromes (i.e. not enough bile salts or pancreatic enzymes to breakdown fats) or part of the gut removed Transit time - during rapid peristalsis i.e. during diarrhoea the gut may not have enough time to absorb nutrients
31
How does the food consumed simultaneously affect the bio-availability of nutrients?
Some food structures can BIND certain nutrients and stop them being absorbed, and some foods have anti-enzymes that stop nutrients being digested and absorbed
32
How does the food preparation method affect the bioavailability of nutrients?
WATER soluble vitamins are easily OXIDISED and destroyed - this means you should not cook them for a long time and in not a lot of water as the nutrients, including folate will leave the food into the water
33
How does the source of the vitamin affect the bioavailability of nutrients?
Synthetic (supplements and cereals) or natural (food) have different bioavailabilities of nutrients, absorb differently and have different structures
34
What are the majority of B vitamins involved in?
Energy production Metabolism of energy yielding intermediates Act as co-factors for redox reactions Also act as transaminases and in methylation
35
What is thiamine (B1) essential for?
Like all B vitamins it is essential for energy production and metabolism. Thiamine is needed to act as a co-factor to convert pyruvate to acetyl-coA and again IN the krebs cycle as a co-factor for redox reactions to occur to drive the metabolic pathway and produce energy
36
What does thiamine deficiency affect?
As it is important for metabolism and energy production a deficiency of thiamine affects MANY systems
37
What happens if you treat a starving, malnourished patient with FOOD but not thiamine?
Re-Feeding Syndrome (example of a primary nutrient deficiency) It can drive further thiamine deficiency because you have increased the fuels for energy production/metabolism but don't have enough to thiamine to meet the demand.
38
Does primary thiamine deficiency occur in NZ?
Rare in NZ but in countries where carbs is their food staple and so they are used to eating more wholegrains > famine > have to consume refined grains i.e. white rice, then they can become thiamine deficient
39
How does thiamine deficiency present?
Wet (due to congestive heart failure) OR dry beriberi
40
What is wet beriberi?
- primary thiamine deficiency can cause congestive cardiac failure - heart doesn't function as well and so blood doesn't flow around the body as efficiently - blood stasis in lower limbs/accumulates/increases hydrostatic pressure in the lower limbs - fluid exudes out of vessels into surrounding tissue (odema) - results in pitting/impressions left on skin that doesn't bounce back due to the fluid under the skin
41
What is dry beriberi?
- no heart issues - causes muscle wasting - affects eyes - affects NERVOUS system so can't control muscles properly (can get foot drop) - metabolically important so often affects metabolically demanding organs (brain/muscles)
42
Why may a dry beriberi occur rather than a wet beriberi?
not sure - may be chronic vs long term deficiency or older vs young
43
What is the main cause of thiamine deficiency in the western world?
Alcoholism and re-feeding syndrome
44
How does alcohol cause thiamine deficiency?
- causes some malabsorption which causes most alcoholics to be thiamine deficient - alcohol causes metabolic breakdown of the liver and stresses the liver - alcohol results in the conversion of thiamine to its active form (TPP) to be reduced
45
What is Wernicke Encephalopathy?
- the alcohol and thiamine deficiency damage nerves - results in alcohol related brain damage causing language problems, walking difficulty and unusual eye movements - reversible with thiamine supplementation
46
Is Wernicke Encephalopathy or Korsakoff Syndrome reversible?
Wernicke Encephalopathy is reversible but if it progresses untreated into Korsakoff Syndrome, then it becomes irreversible
47
What can untreated Wernicke Encephalopathy progress into?
Korsakoff syndrome - causes amnesia - inability to learn and decline in cognitive function - confabulation/babbling - irreversible
48
What is folate found in?
Leafy greens and some fruits
49
What is the food form of folate and what is the fortified/supplement form?
``` Polyglutamate = foods Monoglutamate = fortified foods/supplements (absorbed better) ```
50
How is folate digested?
In the SI glutamates are removed from folate and a methyl group added (hence why fortified monoglutamate forms of folate are absorbed better as already have most glutamates removed) - means damage to the enterocyte can cause folate malabsorption
51
Relationship between B12 and folate?
Inter-related and co-exist. Act as co-factors and methyl donors
52
How can folate mask B12 deficiency?
Because they are inter-dependent in the methylation cycle, with a deficiency in B12 part of the cycle, folate alone can drive part of the cycle, though less efficiently, to produce DNA
53
What are 6 causes of folate deficiency?
1. Low dietary intake (primary deficiency isn't common) 2. Reduced absorption in the SI (damaged enterocytes i.e. Celiacs) 3. Anti-seizure drugs 4. Folate antagonists - i.e. cancer drugs block folate as needed for new cell proliferation 5. Alcohol - increased breakdown, decreased absorption and often accompanied by poor diet 6. Pregnancy as folate requirements increase
54
3 consequences of folate deficiency?
1. Megaloblastic anaemia/macrocytic anaemia (same as B12) 2. Neural tube defects during fetal development i.e. spina bifida (protrusion of spinal cord as not covered in development) 3. May be an increased risk of cancer and heart disease and mental abnormalities due to folates role in the production of homocysteine
55
Why does megaloblastic anaemia occur?
Large mishapen RBCs due to reduction in methylation and so DNA production
56
Why does a folate deficiency cause an increased risk of cancer, heart disease and mental abnormalities
Due to its role in the production of homocysteine
57
Why is folate important in NZ?
NZ has a high rate of NTDs | In countries with mandatory fortification of folic acid rates are considerably lower.
58
Why are people suggesting fortifying foods with folic acid rather than supplements during pregnancy? (fortification is currently voluntary in NZ)
Half of pregnancies are unplanned and then don't know until 12 weeks and by then it is too late the damage of folate deficiency would have already occurred.
59
When is prescription of folic acid (and iodine supplement) free and recommended to take
4 weeks prior to pregnancy and in the first 12 weeks of pregnancy i.e. when there is critical development of the CNS, heart, etc so when the embryo is metabolically active and folate is needed for methylation to form new dna and cells
60
When is the folate dose increased?
When there is previous history of NTD
61
What form of vit a is in animal and plant foods?
animal - retinyl esters | plant - B - carotene
62
What forms of vit a are in the body and what do they do?
Retinol - reproduction Retinal - vision Retinoic acid - growth regulation
63
Vitamin A roles in the body?
Vision including health of the cornea and avoiding night blindness Protein synthesis and cell differentiation i.e. maintaining mucus membrane cells important for immune function
64
Who do vitamin A problems often occur in and how to prevent it?
Children - need animal fat in diets to provide retinyl esters or some areas do mass dosing of vitamin A when kids get immunisations
65
How does deficiency of vitamin A present and do we see it in New Zealand?
See as keratinisation of the skin (chicken skin). Do see in NZ - adolescents often present asking about acne problems and found to have marginal vitamin A deficiencies (acne products often have high vit A)
66
Is overconsumption of B-carotene likely to be toxic?
B-carotene is found in many fruits and vegetables. Has inefficient conversion to vitamin A so cannot over-consume vitamin A to the point of toxicity from FOOD (go orange due to pigment)
67
Is over-consumption of retinol likely to be toxic?
Vitamin A is a fat soluble vitamin so can get over-consumption and toxicity from supplements
68
What are other names for vitamin D
- calciferol - cholecalciferol (animal version of vitamin D - ergocalciferol (plant version) - calcitriol
69
Where do most NZers get most of their vitamin D from?
sun
70
How do we form vitamin D?
The UV light from the sun coverts the precursor 7 - dehydrocholesterol into active vitamin D - without the sun we aren't able to do this conversion to form vitamin D - elderly and adolescents
71
Who is at risk of vit D deficiency?
- all in winter as less sun - elderly and housebound - vit D precursors also have to be hydroxylated by both the liver and kidney so people with liver and kidney disease won;t be able to form metabolically active vitamin D
72
What is the active form of vit D called?
1, 25 - hydroxyvitamin D
73
Do we see vit D deficiency in NZ, if so what is the treatment?
Yes - both primary and secondary (due to liver or kidney problems) Need to give the ACTIVE vit D supplement/form of the vitamin
74
Consequences of vit D deficiency?
- rickets in kids - osteomalacia in adults - insufficient bone mineralisation leading to bow legged when start to hold weight - retirement homes (esp bed bound) are supplemented - especially see in refugees
75
What groups of people need vitamin and mineral supplementation? People with ...
- poor nutrient intake - increased nutrient requirements - increased metabolic demands (surgery/trauma) - maldigestion/malabsorption (liver disease/diarrhoea) - drug-nutrient interactions - medical treatments (chemo) - need for pharmalogical doses > HEALTHY people do NOT as long as have a varied diet
76
Why do you need to check with patient's supplement use?
- toxicity | - drug-nutrient interactions

Digestive (24 decks)

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