Nutrition Mt 2 Fat Soluble Vitamins

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Vitamins:

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non-caloric organic molecules, but required for metabolism

the body cannot synthesize vitamins (or synthesize them in sufficient quantities) so we must get them in minute amounts in our food... our bodies tend to conserve and recycle vitamins, partly why we only need them in minute amounts

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What 3 vitamins can be synthesized by the body?

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D, K, and biotin (a B vitamin)

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what are provitamins?

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they are precursors to vitamins.. they transform into one or more active vitamin forms

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Fat soluble vs. Water soluble vitamins:

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Fat soluble vitamins are A, D, E, K
-require bile for absorption
-generally absorbed into the lymph
-travel in blood associated with protein carriers
-stored in the liver or with other lipids in fatty tissues (can build up to toxic concentrations)

Water Soluble Vitamins: vitamin C and the B complex vitamins.
-absorbed directly into the blood stream
-travel freely in the blood stream
-most aren't stored to any great extent (excess excreted in the urine)
-lower risk of toxicity than fat-soluble vitamins

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how is vitamin C different from the other water soluble vitamins in terms of functioning within the body?

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unlike the other water soluble vitamins, vitamin C does not need to be modified in the body in order to function

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Which two fat-soluble vitamins are especially easy to reach toxic levels (especially with supplementation)

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Vitamins A and D

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Deficiency of Fat Soluble Vitamins

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deficiency is rare since we can store fat soluble vitamins (we just need to reach requirements over weeks, not day to day)

however, people with fat malabsorption diseases and an extremely low-fat diet can become deficient.

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Vitamin A (3 active forms in the body)

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1. Retinol (stored in the liver.. it can be converted to other active forms when needed).

2. Retinal

3. Retinoic Acid

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What is the plant-derived precursor of vitamin A?

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beta-carotene

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Functions of Vitamin A

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1. eye health (day vision and night vision.... an early symptom of vitamin A deficiency is poor adaptation to dim light)

2. maintenance of body linings and skin

3. immune defenses

4. growth of bones and the body

5. normal cell development

6. reproduction

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Two roles of vitamin A in vision:

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1. maintains clarity of cornea

2. participates in transportation of light energy into nerve impulses at retina

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Vitamin A deficiency:

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if deficient in vitamin A, keratin can accumulate (keratinization) on the cornea..
this can lead to xerosis (drying) and to thickening and to permanent blindness (xerophthalmia)

if found early enough, it can be reversed with vitamin A supplementation

mild vitamin A deficiency will be seen as permanent goose bumps and dry, rough, scaly skin (from keratin)

deficiency also effects mucus-producing goblet cells which leads to risk of infection in respiratory, vaginal, and gastrointestinal tissue.

consume fruits and vegetables to avoid deficiency

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How does vitamin A participate in transportation of nerve impulses in the retina?

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light bleaches the vitamin A-containing pigment, "rhodopsin".. this breaks off the vitamin initiating an impulse to the optic center of the brain. The vitamin reunites with the pigment and there is little vitamin A destruction.

*if vitamin A supply is low, a lag occurs before the eye can see again after a flash of bright light (night-blindness)

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Vitamin A and control of gene expression

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retinoic acid activates or deactivates certain genes (affecting protein production)

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Vitamin A and immunity

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vitamin A plays a role in the regulation of genes that produce the immune system proteins.

a vitamin A deficient person has a weakened immune system

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Vitamin A toxicity

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often pregnant women overuse supplements. ~3-4X recommended for pregnancy can cause fetal malformation (a single large dose (~100X recommendation) can cause malformation as well)

young children can mistake supplements for candy and be at risk

adolescents who incorrectly take supplements in an attempt to correct acne (although accutane is derived from vitamin A, it is NOT vitamin A)

with the exception of liver, we are not at risk for toxic intake of vitamin A from food consumption (liver is contraindicated for pregnant women due to vit. A content)

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RAE

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retinol activity equivalent.. the unit that vit. A is measured in

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macular degeneration:

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a common, progressive loss of function of the part of the retina that is most crucial to focused vision (degeneration often leads to blindness)

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vitamin A recommendations:

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RDA:
men = 900 mg
women = 700 mg (higher when lactating)

Tolerable Upper Intake Level = 3,000 mg

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Food Sources of vitamin A:

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mostly from animal origin (liver, fish oil, milk and milk products). Also in butter and eggs. Although fruits and vegetables don't contain active vitamin A, they have the active precursor beta-carotene.

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danger to excessive beta carotene intake?

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excessive beta-carotene intake does not lead to vitamin A toxicity. However, it can cause people to turn bright orange. (in fact increased levels of beta-carotene's in blood FROM FOOD are associated with a lower risk for cancer.. doesn't apply to supplements though)

beta-carotene supplements have a negative effect on smokers though... smokers are discouraged from taking beta-carotene supplements

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most potent antioxidant:

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Lycopene (found in tomatoes and tomato-based foods)

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vitamin D.. is it essential to consume in foods? why?

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no vitamin D is not necessary in food because if we are exposed to enough sunlight our bodies can make enough vitamin D.

vitamin D3 is produced in the skin by the irradiation of a cholesterol-derived metabolite (from sunlight). It is then hydroxylated in the liver and then hydroxylated yet again in the kidneys to its active form.

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Role of vitamin D

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*Regulation of blood calcium and phosphorus (promotes the synthesis of proteins that facilitate transport of calcium and phosphate ions)

functions as a hormone

plays a role in the brain, heart, stomach, pancreas, skin, reproductive organs, some cancer cells, stimulates cell maturation (including immune system cells)

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Vitamin D deficit promotes (diseases):

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high blood pressure, some cancers, type 1 diabetes, heart disease, rheumatoid arthritis, multiple sclerosis

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vitamin D deficiency and its effect on bone:

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Rickets (in the young).. deformation of bones, bow-legs, knock-knees, rib deformities

Osteomalacia (older adults).. overabundance of unmineralized bone protein (most often in women w/ low calcium intake and little exposure to sun and who go through multiple pregnancies and periods of lactation).

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Vitamin D toxicity:

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*most potentially toxic of all vitamins

toxic to bones, kidneys, brain, nerves, heart, and arteries

symptoms include: appetite loss, nausea, vomiting, increased urination, increased thirst, severe form of psychological depression due to effects on the central nervous system

if overdoses continue it leads to dangerously high blood calcium levels, forcing calcium to be deposited in soft tissues (heart, kidney, blood vessels, lung, pulp cavity of teeth)

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can vitamin D reach toxic levels through skin synthesis (from the sun)?

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no. The sun itself begins breaking down excess vitamin D made in the skin. However, sunbathers are at risk for skin cancer and other damage. Sunscreen with SPF levels of 8 or higher can reduce these risks but they also prevent vitamin D synthesis

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Recommendations for vitamin D

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increases with age:
19-50 = 5 ug/day
51-70 = 10ug/day
70+ = 15 ug/day

UL = 100 ug/day

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Food sources of vitamin D

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fortified milk, sunlight

small amounts from: butter, cream, fortified margarine

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Primary function of vitamin E

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antioxidant in body lipids. it is an essential component of all cell membranes where it performs this vital function

vitamin E quenches free radicals (produced from smoking, sunlight, pollution, etc.)

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Vitamin E is also known as....

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tocopherol

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Vitamin E deficiency (3 reasons why its hard to get, people susceptible to it, and symptoms they have)

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1. vitamin E is so widespread in foods it is almost impossible to create a vitamin E deficient diet

2. Also, the body stores so much vitamin E in its fatty tissues that its difficult to not consume food containing vit. E long enough to deplete these stores.

3. Thirdly, cells recycle their supply of vit. E

People who malabsorb fat could possibly get it (i.e. pancreatic disease)

Also infants who are born before the transfer of vit. E from the mother to the infant... this leads to erythrocyte hemolysis, resulting in anemia

symptoms in adults: loss of muscular coordination and reflexes with impaired movement, vision, and speech

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Vitamin E and its effect on the lungs:

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vitamin E's antioxidant properties are especially important in the lungs, where cells are exposed to high concentrations of oxygen.. (also protects red blood cells, white blood cells... plays a role in immunity and nerve development)

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Vitamin E toxicity:

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no toxicity from food sources

ordinary supplemental doses over a period of months does not seem to induce toxicity

large doses may increase the effects of anticoagulant medications (do not take vit. E before surgery or with anticoagulant meds)

brain hemorrhages may occur in smokers taking 50 mg/day for over 6 years.

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Food Sources of Vitamin E

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widespread in most foods
most raw oils
20% of dietary vit. E comes from vegetable oils
20% from fruits and vegetables
15% from fortified cereals and other grain products

smaller amts from meat, poultry, fish, eggs, milk, nuts, seeds

wheat germ is a good source

animal fats have almost no vitamin E

*vitamin E is destroyed by food processing, heat, and oxidation

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vitamin E and PUFA:

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as you eat more PUFA, you need to increase vitamin E consumption

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functions of vitamin K

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1. synthesis of blood clotting proteins (does not increase clotting in those with hemophilia).. interferes with function of blood thinners

2. synthesis of normal form of bone proteins that bind minerals to bone (adequate intake may reduce risk of hip fracture)

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vitamin K1 vs. vitamin K2

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vitamin K is found naturally is K1 in green vegetables, and K2, which is synthesized by intestinal bacteria

The body is also able to convert synthetically prepared vitamin K (menadione) to biologically active K1

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vitamin K deficiency

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not very common (intestinal bacteria produce it)

those at risk:
1. newborns.. a newborn's colon is sterile.. it is common practice to give a newborn a shot of vitamin K
2. those on antibiotics (that kill intestinal bacteria)
3. those with low bile production

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Best dietary sources of vitamin K

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canola oil, cruciferous vegetables, soybean oil

other good sources: beef, liver, bran, and olive oil

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vitamin K toxicity

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rare

no UL set.

infants and pregnant women: toxicity can result from oversupplementation

symptoms:
1. red blood cell breakage: colors skin yellow
2. liver release of bilirubin in the blood (leads to jaundice).. jaundice in infants can cause brain damage or death