Fat Soluble Vits

8/3/2019 Fat Soluble Vits

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Fat Soluble Vitamins

Barnali Deori

M.Sc.1st yr

Deptt. of Food and Nutrition


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Fat Soluble Vitamins (A, D, E, K)

Soluble in lipids and solvents

Found in the fats and oils of food.

Excess stored and not excreted.

Absorbed into the lymph and carried in blood with protein

transporters - chylomicrons.

Stored in liver and body fat and can become toxic if large amountsare consumed.


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Vitamin A

3 forms: retinol ( transport and storage form of vitamin A ),

retinal (essential for vision), retinoic acid (acts like a hormone)

precursor beta carotene

Roles in body:

Regulation of gene expression

Part of the visual pigment rhodopsin, maintains clarity of

cornea.

Required for cell growth and division - epithelial cells, bones

and teeth

Promotes development of immune cells, especially

Natural Killer Cells

Antioxidant


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Vitamin A- Structure


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Metabolism

Absorption and Bioavailability

Seventy to ninety percent of vitamin A from the diet is absorbed in

the intestine

Greater than 90% of the retinol store within the body enters as

retinyl esters that are subsequently found within the lipid portion of

the chylomicron

Absorption of vitamin A is very rapid, with maximum absorption

occurring two to six hours after digestion.


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Within the intestinal lumen the vitamin is incorporated

into a micelle and absorbed across the brush border intothe enterocytes.

Within the enterocyte, precursors of vitamin A

(carotenoids) are converted to active forms of the

vitamin.

The newly formed products and additional precursors

are then packaged into chylomicrons and readied for

transport throughout the body.


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Transport

After leaving the enterocytes, chylomicrons, which carry retinyl

esters, carotenoids, and unesterfired retinol along with triglycerides,

are circulated first through the lymphatic system and then through

the general circulation.

The vitamin A is then incorporated into a chylomicron remnant. The

chylomicron remnant then travels back to the liver where it is taken

up and further metabolized or stored.

Retinol-binding protein (RBP) is the specific carrier used to transportall-trans retinol in the plasma. This specific carrier is manufactured

and secreted by the parenchymal cells of the liver.


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Each mole of retinol released binds with RBP to form

holo-RBP. This compound then binds with a molecule of

transthyretin (TTR), formerly known as prealbumin.

This newly formed retinol-RBP-TTR complex is notfiltered by the glomerulus, but instead freely circulates

throughout the plasma.

Tissues are then able to take the retinol up as needed

via cellular retinoid-binding protein.


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Storage

Approximately 50 to 85% of the total body retinol are stored in the liverwhen vitamin A status is adequate.

Retinol returning to the liver is re-esterfied before storage. Because of

this, over 90% of the retinol is stored in the form of retinyl esters.

The retinol is stored in hepatic stellate (star-shaped) cells along with

droplets of lipid.

The size of stellate cells increase linearly with increasing retinol levels.

Once hepatic stellate cells are saturated with all the retinol they can

hold, hypervitaminosis can result.

The precursor to vitamin A, beta-carotene, can be stored in

adipose cells of fat depots throughout the body.


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Vitamin A is very important for immune system of

the human body.

Skin, lining the digestive and urinary tracks, contains Retinol. This

lining restricts the entrance of various infectious microbes and other

harmful materials.

Retinoic acid and vitamin A are also essential for the formation of

white blood cells, which are very important for fighting different

infectious materials, hence strengthening the immune system.

Different studies suggest that Vitamin A is helpful in reducing growthof cancer in different parts of human body for example liver, breast,

colon and skin.


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Deficiencies cause: Night blindness, xerophthalmia (keratin deposits in cornea),

macular degeneration.

Skin and mucous membrane dryness and infection, keratindeposits.

Anemia

Developmental defects bones, teeth, immune system,vision.

Toxicities (single large doses of supplements, eatingexcessive amounts of liver) cause:

Fragile RBCs, hemorrhage

Bone pain, fractures

Abdominal pain and diarrhea

Blurred vision

Dry skin, hair loss

Liver enlargement


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Vitamin D

There are two main forms of dietary Vitamin D, those are

D2 (ergocalciferol) and

D3 (cholecalciferol).

D2 is mainly produced by plants, and is not as bioactive inhumans as the D3 form.

There are three forms of vitamin D that function in the body.

Cholecalciferol (vitamin D3). This is the form of the vitaminmade in the skin.

Calcidiol (25-hydroxyvitamin D). The storage form of thevitamin in human tissues.

Calcitriol (1,25-hydroxyvitamin D). The active, steroid form,of vitamin D

precursor is cholesterol,

It is the only fat soluble vitamin that we can make- in the presenceof sunlight.


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Vitamin D- Structure

Vitamin D3 (Cholecalciferol)Vitamin D2 (Ergocalciferol)


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Absorption of Vitamin D

80% of vitamin D consumed is incorporated into

micelles.

Bile salts are essential for its absorption.

After combining with bile salts, it passes into the lacteal

system through the intestinal epithelial cells.

Absorption occurs from duodenum and jejunum through

the lymphatic system and transported via

chylomicrons and passes into the blood

stream.


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Vitamin D3 derived from dietary sources is transported by a specific

vitamin D-binding protein, to liver where it is further metabolised to

25-hydroxy vitamin D3.

25-hydroxy vitamin D3 is further metabolised to 1,25 dihydroxy

vitamin D3 in the kidney.

1,25 dihydroxy vitamin D3 is the active hormonal form of vitamin D

which brings about all the biological functions of the body.

EXCRETION

Excreted in bile

Metabolized to water soluble metabolites and then

excreted in urine as well.


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Vitamin D- A Vitamin or a Hormone

Vitamin D is not really a vitamin at all - it is a pre-

hormone that's produced in the skin in response to

sunlight exposure. As such, it is an integral part of

human health and longevity.

It functions as a steroid hormone. What steroid

hormones do is go in to the nucleus of cells, and alter

gene expression, that is turning genes on or off, or

simply giving them a nudge in either direction.


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FUNCTIONS

Immunity

The inactive form of vitamin D aids in the formation of activevitamin D which enhances immunity and inhibits the development

of autoimmune disease.

Calcium balance

With decreased dietary calcium, PTH is secreted and causes

increased production of calcitriol, a hormone

Calcitriol restores normal calcium levels by increased absorption

of dietary calcium, increased mobilization of calcium from bone,

and increased reabsorption from kidneys

Heart disease

Renin, important in regulation of blood pressure

and heart health, is associated with vitamin D levels.


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Vitamin D: Deficiency Rickets (children)

bone deformities in children

Osteomalacia (adults)

weak bones due to low calcium content

Vitamin D deficiency

Calcium deficiency multiple pregnancies

Toxicities Loss of calcium from bone and deposition in soft

tissues.

Loss of appetite, nausea and vomiting,

psychological depression.


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Vitamin E

The name Vitamin E covers a collection of eight fat soluble

compounds, tocopherols and tocotrienols:

alpha-Tocopherol - the most common and biologically active

beta-Tocopherol

gamma-Tocopherol

delta-Tocopherol

alpha-Tocotrienol

beta-Tocotrienol

gamma-Tocotrienol

delta-Tocotrienol
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All have a 6-chromonal ring structure and a side chain.

The tocopherols have a completely saturated hydrocarbon chain,

whereas the tocotrienols are characterized by a partly unsaturatedhydrocarbon chain.

Other tocopherol and tocotrienol compounds differ in the number

and position of methyl groups attached to the chromanol ring.

The hexagonal component on the left side of each structure holdsthe antioxidant activity of the vitamin E structure.

The human genome has selected alpha-tocopherol among these 8

compounds and has evolved a number of specific proteins to protect

it and distribute it throughout the body. The major distinction

between them and alpha-tocopherol, however, is the speed with

which they are cleared from your system.


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Vitamin E- Structure


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Metabolism

Absorption and Bioavaliability

Absorption of vitamin E is highly dependent upon the same

processes that are utilized during fatty acid digestion and

metabolism.

Bile acids are considered essential for vitamin E absorption andmicelle formation.

Once formed, the micelle is then able to cross the unstirred water

layer and release its contents into the enterocyte.

After passing through the enterocyte the vitamin E is

packaged into a chylomicron and readied for circulation.


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Transport

The vitamin E in the chylomicron equilibrates with both High-Density

Lipoproteins (HDL) and Low-Density Lipoproteins (LDL). From the

HDL all circulating lipoproteians eventually receive vitamin E.

The vitamin E remaining in the chylomicron becomes a chylomicron

remnant and travels back to the liver for re-uptake.

Once in the liver, the vitamin E is packaged into Very Low Density

Lipoproteins (VLDL) and excreted back into the circulation. The

predominant transfer of the alpha vitamin is performed by alpha

tocopherol transfer protein (ATTP).


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As the VLDL are broken down by lipoprotein lipase, LowDensity Lipoproteins (LDL) are formed and from these

lipoproteins the vitamin E is transferred to HDL and

eventually incorporated into peripheral tissue.

A final mechanism for vitamin E is uptake by the

peripheral tissue from the chylomicron via lipoprotein

lipase activity.


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Storage

Vitamin E is a lipid soluble vitamin and therefore over

90% of total body vitamin E is found in the adiposetissue.

Excretion Vitamin E is excreted mainly via bile, urine, feces, and

the skin.

Because of the poor intestinal absorption of vitamin E,

fecal excretion is the main route of vitamin E

elimination.


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How do other nutrients interact with vitamin E?

The recycling of vitamin E in the body is intricately connected to four

other nutrients: vitamin C, glutathione, selenium, and vitamin B3.

Vitamin C is required to keep vitamin E in its metabolically active

form;

glutathione (a very small protein molecule called a tripeptide and

consisting of three amino acid building blocks) is required to keepvitamin C in its active form;

selenium (a micromineral) and vitamin B3 are required to keep

glutathione in its active form.

The fact that vitamin E is so heavily dependent on vitamin C,

vitamin B3, selenium, and glutathione means that a diet

high in vitamin E cannot have its optimal effect unless it

is also rich in foods that provide these other nutrients.
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What are Free Radicals?

It is ironic that oxygen, which is an indispensable

element for life can have severe deleterious effects on

the human body under certain situations.

Most of the potentially harmful effects of the oxygen aredue to the formation and activity of number of chemical

compounds, known as reactive oxygen species (ROS),

which have tendency to donate oxygen to othersubstances.


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Many such reactive species are free radicals.

When the mitochondria of the cells produce energy, they throw off

molecules called free radicals in the process.

Free radicals are those molecules which have a surplus of one or

more free floating electrons in its outer ring rather then having

matched pairs and are therefore, unstable and highly reactive.

Types of free radicals

Hydroperoxyl radical

Superoxide radical

Hydrogen peroxide

Triplet oxygen

Singlet oxygen


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Sources of free radical

Free radicals and other reactive species are derived either from

normal essential metabolic processes like enzymatic reactions

(those involved in the respiratory chain, in phagocytosis, in

prostaglandin synthesis, etc.) or from external sources, such as

exposure to x-rays, ozone, cigarette smoking, air pollutants,

industrial chemicals etc.

Mental status like stress, emotion etc. and disease conditions are

also responsible for the formation of free radicals.


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How are free radicals formed in the humanbody?

Free radicals are produced in most cells of the body as a byproduct

of metabolism, although some cell types manufacture larger

quantities for specific purposes.

These free radicals are always in search of stabilizing themselves

by undergoing chemical reaction with other atoms and molecules.

They rob other atoms of their electrons in order to stabilize

themselves and in this way oxidation reaction takes place

and thus cause cell death and injury.


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When free radicals steal an electron from a surrounding compound

or molecule a new free radical is formed in its place. In turn, the

newly formed radical then looks to return to its ground state by

stealing electrons from cellular structures or molecules. Thus the

chain reaction continues and can be "thousand of events long."

If free radicals are not inactivated, their chemical reactivity can

damage all cellular macromolecules including proteins,

carbohydrates, lipids and nucleic acids.


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Mechanism for the formation of freeradicals


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Vitamin E and heart disease -

Vitamin E helps protect against heart disease by limiting the

oxidation of LDL-cholesterol.

Vitamin E also keeps arteries flexible and elastic, allowing blood to

flow freely.

Vitamin E helps prevent arteries from clogging by blocking the

conversion of cholesterol into the waxy fat deposits called plaque

that stick to blood vessel walls.

Vitamin E also thins the blood, allowing for blood to flow more easily

through arteries even when plaque is present.

Vitamin E also may help prevent the formation of blood clots, which

could lead to a heart attack.

Vitamin C and vitamin E, taken in combination, help to

stabilise LDL cholesterol in the body. This may help

to reduce the risk of atherosclerosis


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Vitamin E and cancer -

Some cancers are believed to result from oxidative damage to DNA

caused by free radicals. Free radicals can damage DNA, leading tomutations in cells that may cause cancer.

Antioxidants such as vitamin E help protect against the damaging

effects of free radicals. Vitamin E may protect against the

development of cancers by enhancing immune function.

Some evidence associates higher intake of vitamin E with a

decreased incidence of prostate cancer and breast cancer.

Cigarette smokers have a higher risk of developing cancers of the

mouth, upper airways and lungs, and vitamin E may help

protect smokers against these cancers through

its antioxidant properties.


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Vitamin E and alzheimer's disease -

Alzheimer's disease is a wasting disease of the brain.

Oxidative stress is believed to contribute to the development of

Alzheimer's disease. Vitamin E is an antioxidant that prevents free

radical damage in biological membranes.

Vitamin E supplementation improves cognitive performance in

healthy individuals.

In addition, vitamin E, together with vitamin C may prevent thedevelopment of Alzheimer's disease.


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Recommended daily allowance (RDA)

The recommended dietary allowance (RDA) for vitamin E is

10 mg/day for the adult man,

8 mg/day for the adult woman, and

3 mg/day for the infant.

In April 2000 the Food and Nutrition Board raised the RDA for men

by 50 percent and nearly doubled the RDA for women. The new

RDA is 15 milligrams for both sexes, including pregnant women. For

lactating mothers it is 19 milligrams.


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Sources of vitamin E

Vitamin E is found in the germ of a seed or grain.

The best sources of vitamin E are vegetable oils such

as sunflower, canola, corn, soybean and olive oil and

products made from these oils (such as margarine).

Nuts, sunflower seeds and wheat germ are also good

sources.

Other sources of vitamin E are whole grains, fish, peanut

butter, and green, leafy vegetables.

In these oils, approximately 50 percent of the tocopherol

content is in the form of alpha-tocopherol.


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Deficiencies

Vitamin E deficiency affects the central nervous system and

may result in progressive neuromuscular disease

characterized by loss of reflexes, muscle weakness, loss ofbalance and impaired ability to coordinate voluntary

movements (ataxia).

Vitamin E deficiency may also contribute to cardiovascular

diseases, including atherosclerosis, as well as an increased

risk of certain cancers.

Premature infants may be at risk for vitamin E deficiency

because they may be born with low tissue levels of the

vitamin, and because they have a poorly developed capacity

for absorbing dietary fats.

Toxicities (more than 1000 milligrams/day)

Interfere with the body's ability to clot blood.


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Vitamin K3 forms:

Phylloquinone (K1, which naturally occurs in plants ),

menaquinones (K2, which is produced by the bacteria that lines

gastrointestinal tract ) and

menadion (K3, a synthetic form of vitamin K, which is converted tovitamin K2 in the intestine ).

The Menaquinones differ from Phylloquinones in the number of

isoprene units in the side chain.

Vit i K St t


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Vitamin K- Structure


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Metabolism

Absorption and transport Dietary vitamin K, mainly as phylloquinone, is absorbed in the small

intestine and the process is facilitated by bile salts and pancreatic

juices.

Within the intestinal mucosa the vitamin is incorporated intochylomicrons, is secreted into the lymph, and enters the blood via

the lacteals.

Phylloquinone is the major circulating form of vitamin K but

menaquinone is present in plasma at lower concentrations and has

a lipoprotein distribution similar to phylloquinone.

Menaquinones are synthesized by the bacteria in

the colon and are absorbed.


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Tissue stores and distribution

Human liver stores normally comprise about 90 percentmenaquinones and 10 percent phylloquinone.

Other sites of storage may be adipose tissue and bone; both are

known to be sites where vitamin K-bearing chylomicrons and

chylomicron remnants may be taken up.

Excretion

Vitamin K is extensively metabolised in the liver and excreted in the

urine and bile.


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Functions of vitamin K

Promotes healthy blood clotting

Vitamin K is used by the liver to form at least four different kinds of

proteins that are necessary for blood to properly clot. These factors

include prothrombin, proconvertin, thromboplastin component, and

Stuart factor.

Other clotting factors that depend on vitamin K are protein C, protein

S, and protein Z.

Deficiency of vitamin K or disturbances of liver function may lead to

deficiencies of clotting factors and excess bleeding. Vitamin K1 is the preferred form used in the liver to

carboxylate clotting factors.


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Protects bones from weakening or fracture

Vitamin K is responsible for assisting in the formation of three

important proteins produced outside the liver. These proteins are

osteocalcin, matrix Gla protein, and protein S.

Osteocalcin is involved in the mineralization of bone. Adequate

vitamin K intake and vitamin K body levels are linked to bone

mineral density.

Research found that patients who suffered fractures caused by

osteoporosis had vitamin K levels 70% lower than age-matched

controls.

Vitamin K2 also works with vitamin D3 to increase the production of

Gla-proteins, including osteocalcin in osteoblasts (the cells that buildbone), while also inhibiting the production of osteoclasts

(the cells that break down bone).


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Prevents calcification of blood vessels

or heart valves

One common problem in many forms of cardiovascular disease

is unwanted calcification, the build-up of calcium inside a

tissue that is normally soft. This build-up of calcium causes the

tissue to harden and stop functioning properly

One direct way to inhibit the build-up of calcium along thearteries is to maintain ample supplies of a special protein called

MGP in the body.

MGP, or matrix Gla protein, directly blocks the formation of

calcium crystals inside the blood vessels. For MGP to function in this way, it must first be present in its

carboxylated form; vitamin K is required for this

carboxylation process.


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Deficiencies

Deficiencies are rare but seen in infants, after prolonged antibiotic

therapy, and in patients with decreased bile production.

Infants are at higher risk for hemorrhagic disease of newborn,

caused by a lack of Vitamin K reaching the fetus across the

placenta, the low level of Vitamin K in breast milk, and low colonicbacterial synthesis.

In adults, Vitamin K deficiency is uncommon due to the intake of a

wide variety of vegetables and other foods; the recycling ability of

Vitamin K , which helps to conserve the body's supply; and

adequate gut flora to produce Vitamin K.

F d Th C i Vi i K


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Foods That Contain Vitamin K

Green leafy vegetables as the richest sources of vitamin K.

Examples include kale, spinach, turnip greens, parsley, mustardgreens, broccoli and leaf, lettuces. Other vegetable sources for

vitamin K include cauliflower, green beans, coriander and okra.

Fruits like kiwi, blackberries, blueberries and red grapes are also

good sources of vitamin K. Some meats contain vitamin K, including dark turkey meat, chicken

meat and cow liver. Egg yolks and mayonnaise, which contains

eggs, also contain vitamin K. Dairy sources of vitamin K include

yogurt, butter and some cheeses. Oats, wheat and rye contain vitamin K.

Similar food sources of vitamin K include safflower oil, olive oil,

canola oil, soybeans, soybean oil and fermented soybean products.


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Recommended Dietary Allowances

RDA for adult males: 80 mcg

RDA for adult females: 65 mcg

RDA for children 7 to 10 years: 30 mcg

RDA for infants: 10 mcg

RDA for pregnant and lactating women 65 mcg


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Fat Soluble Vits

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