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Foundations In Human Nutrition > Vitamins > Flashcards

Vitamins Flashcards

1
Q

What are vitamins?

A

Vitamins are organic compounds which are chemically unrelated .

They are required for the maintenance of normal health and metabolic integrity

They cannot be synthesised in the body but must be provided in the diet

They are found in minute quantities in food

They are required in very small amounts (µg or mg/day) and can thus be distinguished from essential macronutrients amino acids and fatty acids (g/day)

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2
Q

Name the vitamins that are essential for regulation of body processes and normal metabolic function

A

Vitamin A

B Vitamins - thiamine, riboflavin, niacin, B6, B12, biotin, pantothenic acid and folate

Vitamin C

Vitamin D

Vitamin E

Vitamin K

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3
Q

Name and explain the vitamins that can be synthesised by the body

A

Vitamin D: Synthesised in the skin upon exposure to the sun

Vitamin K and some B vitamins: synthesised by gut flora

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4
Q

Name and explain vitamins that occur in food in the form of precursors what are converted in the body to the active vitamin

A

Beta carotene converted to vitamin A

Tryptophan (converted to niacin B3)

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5
Q

Explain how the vitamins are named

A

Vitamins C, D and E follow logically

Vitamin F - found to be essential fatty acids

Vitamin G - found to be the same as B2

Vitamin H - same as Biotin

Vitamin K - discovered because of blood clotting studies in Denmark. Stands for Koagulation

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6
Q

What factors influence the solubility of vitamins?

A

Mode of action

Transport

Storage

Toxicity

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7
Q

Name the 2 categories that vitamins are divided into

A

Lipid soluble

Water soluble

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8
Q

Name the fat and water soluble vitamins

A

Fat soluble:

Vitamin A

Vitamin D

Vitamin E

Vitamin K

Water soluble vitamins:

Vitamin B’s

Vitamin C

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9
Q

Give some factors that influence the utilisation of vitamins

A

Availability

Anti-vitamins

Provitamins

Biosynthesis in the gut by bacterial flora

Intestinal disease

Interaction of other nutrients

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10
Q

Explain fat soluble vitamins

A

Found with fat in food

Specific mechanism for absorption and transport (sae as other fats/lipids)

Transported attached to protein

Often stored in the body - stored in liver or in fatty tissues, Vitamin A and D stored in the liver and may be toxic

Toxicity is more common as a result of excessive intake

Rarely act as coenzymes - except vitamin K

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11
Q

Explain the function and deficiency of the following vitamins and give names of each:

Vitamin A

Vitamin D

Vitamin E

Vitamin K

A

Vitamin A: retinol, retinal, retinoic acid

Function:
Visual pigments in the retina
Gene expression
Cell differentiation

Deficiency:
Night blindness
Keratinisation
Xerophthalmia

Vitamin D: calciferol

Function:
Maintenance of calcium balance
Intestinal absorption of calcium
Mobilisation of bone minerals

Deficiency:
Rickets (children) - poor mineralisation of bone
Osteomalacia (adults) Demineralization of bone

Vitamin E: tocopherols, tocotrienols

Function:
Antioxidants, especially in membranes

Deficiency:
Serious neurological dysfunction
(very rare)

Vitamin K: phyloquinones, menaquinones

Fucntion:
Coenzyme in formation of carboxy glutamic acid in the enzymes of the blood clotting cascade and bone matrix

Deficiency:
Impaired blood clotting Haemorrhagic disease

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12
Q

What are the functions of Vitamin A?

A

Helps our cells grow and develop

Supports vision

Supports our immune system

Supports the healthy development of the baby

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13
Q

Explain Vitamin A absorption and transport

A

Retinyl ester serves as the main storage form of retinol, acts as the primary transport form of newly arrived Vitamin A, and acts as the precursor for Vitamin A metabolites

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14
Q

Explain storage and excretion of vitamins

A

Most of the body’s vitamin A is sored in the liver in the form or retinyl esters

Retinol can be converted into retinoic acid and excreted into the bile and faeces. The elimination half-life of retinol may range from 2 to 9h; however; the half-life of Vitamin A is about 12 days

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15
Q

Name some foods that contain vitamin A

A

Vitamin A (retinol):

Dairy - milk, eggs, cheese, yoghurt

Meat - steak

Vitamin A (carotenoids):

Peppers

Melon

Spinach

Sweet potato

Carrot

Mango

Papaya

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16
Q

What is the DRV for Vitamin A?

A

Ages 1-6:

Males: 400 ug/day
Females: 400 ug/day

Ages 7-10:

Males: 500 ug/day
Females: 400 ug/day

Ages 11-14:

Males: 600 ug/day
Females: 600ug/day

Ages 15 - 18:

Males: 700 ug/day
Females: 600 ug/day

Age 19-64:

Males: 700 ug/day
Females: 600 ug/day

Ages 65 - 74:

Males: 700 ug/day
Females; 600 ug/day

Ages 75+

Males: 700 ug/day
Females: 600 ug/day

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17
Q

What is the RNI and SI for vitamin D

A

10 micrograms per day for adults (including pregnant and breastfeeding women) and children ages 4 yrs and older

Safe intake of 8.5 to 10 micrograms per day for infants up to 12 months

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17
Q

Explain Vitamin D

A

Vitamin D is a fat-soluble vitamin that is naturally present in a few foods, added to others, and available as a dietary supplement.

It is also produced endogenously when UV ryas from sunlight strike the skin and trigger Vitamin D synthesis

Vitamin D is obtained from sun exposure, foods, and supplements

17
Q

Explain Vitamin D deficiencies

A

Without sufficient Vitamin D, bones can become thin, brittle, or misshapen

Vitamin D sufficiency prevents rickets in children and Osteomalacia in adults

Together with calcium, Vitamin D also helps protect older adults from osteoporosis

Hypocalcaemia tetany (involuntary contraction of muscles, leading to cramps and spasms)

18
Q

Name food sources of Vitamin D

A

Eggs

Meat

Dairy

Fish

Leafy greens

18
Q

Explain Vitamin E

A

Vitamin E is the collective name for a group of fat-soluble compounds with distinctive antioxidant activities

Vitamin E exists in eight chemical forms (alpha-, beta-, gamma-, and delta-tocopherol and alpha-, beta-, gamma-, and delta-tocotrienol) that have varying levels of biological activity. Alpha- (or α-) tocopherol is the only form that is used in the human body.

19
Q

Explain the function of Vitamin E in the body

A

Protects cells from the damaging effects of free radicals, which are molecules that contain an unshared electron. Free radicals damage cells and might contribute to the development of cardiovascular disease and cancer.

Immune function, cell signalling, regulation of gene expression, and other metabolic processes.

Inhibits the activity of protein kinase C, an enzyme involved in cell proliferation and differentiation in smooth muscle cells, platelets, and monocyte

20
Q

Explain absorption and transport of Vitamin E

A

Vitamin E is absorbed in the small intestine in the same process as lipids and transported via the blood stream

21
Q

Explain storage and excretion of Vitamin E

A

Vitamin E is stored in the liver and fatty tissues.

Unabsorbed vitamin E is excreted via faeces.

Additionally, vitamin E is excreted by the liver via bile into the intestinal lumen, where it will either be reabsorbed or excreted via faeces, and all the vitamin E vitamers are metabolised and then excreted via urine.

22
Q

What is the DRV for Vitamin E?

A

4 mg a day for men

3 mg a day for women

23
Q

Explain Vitamin K

A

Vitamin K, the generic name for a family of compounds with a common chemical structure of 2-methyl-1,4-naphthoquinone, is a fat-soluble vitamin that is naturally present in some foods and is available as a dietary supplement

Includes phylloquinone (vitamin K1) and a series of menaquinones (vitamin K2). Menaquinones have unsaturated isoprenyl side chains and are designated as MK-4 through MK-13, based on the length of their side chain.

Almost all menaquinones, particularly the long-chain menaquinones, are also produced by bacteria in the human gut

24
Q

Explain the function of Vitamin K

A

Vitamin K functions as a coenzyme for vitamin K-dependent carboxylase, an enzyme required for the synthesis of proteins involved in haemostasis (blood clotting) and bone metabolism and other diverse physiological functions.

25
Q

Explain absorption and transport of Vitamin K

A

Like dietary lipids ingested vitamin K is incorporated into mixed micelles via the action of bile and pancreatic enzymes, and it is absorbed by enterocytes of the small intestine. From there, vitamin K is incorporated into chylomicrons, secreted into the lymphatic capillaries, transported to the liver, and repackaged into very low-density lipoprotein

26
Q

Explain storage and excretion of Vitamin K

A

Compared to the other fat-soluble vitamins, very small amounts of vitamin K circulate in the blood. Vitamin K is rapidly metabolised and excreted.

The body retains about 30-40% per oral physiological dose.

About 20% is excreted in the urine and 40% to 50% in the faeces via bile.

27
Q

Explain Vitamin K deficiencies

A

Bleeding and haemorrhage due to significant increases in prothrombin time (blood clotting).

Because vitamin K is required for the carboxylation of osteocalcin in bone, vitamin K deficiency could also reduce bone mineralisation and contribute to osteoporosis.

Vitamin K deficiency can occur during the first few weeks of infancy due to low placental transfer of phylloquinone, low clotting factor levels, and low vitamin K content of breast milk.

28
Q

Name food sources that contain Vitamin K

A

Tomatoes

Died fruits - apricots, raisins

Nuts - chestnuts, walnuts, almonds

Broccolis

Spinach

Courgette

29
Q

What is the DRV for Vitamin K

A

Adults needs approximately 1 microgram a day of Vitamin K for each Kg of they body weight

30
Q

Explain water soluble vitamins

A

Not stored (apart from B12)

Enter the body freely, absorbed directly into blood stream, dissolves in intra and extra cellular fluids and is therefore transported in free form

Higher turnover in the body with little storage

Excrete it easily in urine, generally not harmful but in high doses can be

Mainly coenzymes in energy metabolism

Prone to leaching from food, more sensitive to heat

31
Q

Explain the function and deficiency of the following water-soluble vitamins:

Vitamin B

Vitamin C

A

Vitamin B:

Function: Enzyme co-factor

Deficiency: Varies depending on the B vitamin

Vitamin C:

Function: Collagen synthesis, Enzyme co-factors, Antioxidant

Deficiency: Scurvy, Impaired wound healing, Subcutaneous haemorrhage

32
Q

Explain Vitamin C

A

Ascorbic acid
(L-ascorbic acid is a white, odourless and stable solid, slightly soluble in ethanol, insoluble in organic solvents and soluble in water)

It can be synthesised in plants and most animal species

From D-glucose and D-galactose

But cannot be synthesised by humans

Or primates, guinea pigs, fruit eating bats, certain birds and many fish since they lack the final enzyme in the synthesis of the Vitamin C

33
Q

Explain the structure of Vitamin C

A

Structure

Potent reducing agent

Antioxidant agent

Acidic forming

Exists in two isomers (mirror – image isomers L and D)

34
Q

Explain the function of Vitamin C

A

Plays a role in the regeneration of vitamin E

Enhances iron absorption

Vitamin C is required for collagen synthesis

Vitamin C is a cofactor for the enzymes (coenzyme) in the hydroxylation of proline and lysine in collagen synthesis

Hydroxylated proline and lysine are essential to produce normal collagen

Hydroxyproline forms the backbone for the triple helical structure of collagen molecules (tropocollagen)

Hydroxylysine is required for the cross linking of collagen (which increases the strength and elasticity of collagen)

35
Q

Explain Vitamin C absorption and transport

A

Readily absorbed in small intestine

Energy dependant absorption (ATP)

70 to 90% of average intake absorbed (30-200mg)

Absorption decreased to 20% with a single 5g dose and to 6% with a single 12g dose

Bioavailability from food and supplements is similar

Transported unbound in plasma

High concentrations found in intracellular fluid

Maintained by ATP driven uptake mechanism

36
Q

Explain Vitamin C metabolism

A

Studies show that the body is saturated with vitamin C at 20mg/kg body weight on average

Normal plasma levels of vitamin range from 4 -15mg per litre

This level can be maintained with a daily intake of between 60 and 100mg vitamin C by most people

At levels greater than 200mg/day virtually all excess vitamin C is excreted in urine within 24 hours

37
Q

Explain Vitamin C storage and excretion

A

Vitamin C is not stored in the body for long

When vitamin C free/low diet consumed there is a 3% loss per day (approximately)

On a usual intake about 50% of vitamin C is excreted in the urine as oxalic acid

Ascorbic acid, dehydroascorbic acid and other metabolites make up the remainder

When intake greatly exceeds requirement most of excess treated as unmetabolised vitamin C

38
Q

Name some conditions a that are caused by Vitamin C deficiency

A

Scurvy

Impaired wound healing

Loss of teeth die to damaged gums (bleeding gums)

Subcutaneous haemorrhage (bleeding from capillaries)

Failure or proper cartilage and bone formation

39
Q

Name some food source of vitamin C

A

Fruits - oranges, mango, lemon, strawberries

Vegetables - onion. spinach, coriander, tomato, parsley

40
Q

Give the DRV for Vitamin C

A

9–13 years:

Males: 45 mg
Females:45 mg

14–18 years

Males:75 mg
Females: 65 mg

19+ years
Males: 90 mg
Females: 75 mg

Foundations In Human Nutrition (17 decks)

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