Chapter 11 - Fat Soluble Vitamins

what was the first vitamin to be recognized

Vitamin A

what is the precursor to vitamin A

beta-carotene

three active forms of vitamin A in the body

retinol, retinal, and retinoic acid

the three active forms of vitamin A are collectively known as:

retinoids

retinoids are commonly found in foods derived from…

animals

foods derived from plants provide _____, some of which can be converted to vitamin A

carotenoids

beta-carotene can be split to form _______ in the intestine and liver

retinol

this special transport protein can pick up vitamin A from the liver and carry it in the blood

retinol-binding protein (RBP)

retinoic acid can _____ cell growth in the skin

stimulate

retinoic acid can ____ cell growth in tumors

inhibit

major roles of vitamin A

promoting vision; participating in protein synthesis and cell differentiation; supporting reproduction and regulating growth

___- supports reproduction and is the major transport and storage form of vitamin A

retinol

_____ is active in vision and is also an intermediate in the conversion of retinol to retinoic acid

retinal

________ acts like a hormone, regulating cell differentiation, growth, and embryonic development

retinoic acid

two indispensable roles of vitamin A in the eye:

helps maintain a crystal-clear outer window, the cornea, and it participates in the conversion of light energy into nerve impulses at the retina

pigment molecules contained within the photosensitive cells of the retina

rhodopsin

each rhodopsin molecule is composed of a protein called _____ bonded to a molecule of retinal, which plays a central role in vision

opsin

what happens when light passes through the cornea of the eye and strikes the retina

opsin is released and retinal shifts from a cis to a trans configuration

how is rhodopsin regenerated

retinal is converted back to its active cis form and recombined with opsin

what is cell differentiation

the process by which each type of cell develops to perform a specific function

all body surfaces, both inside and out, are covered by layers of cells known as:

epithelial cells

epithelial tissue on the outside of the body

skin

epithelial tissues that line the inside of the body

mucous membranes

what are goblet cells

one-celled glands that synthesize and secrete mucus

vitamin A promotes differentiation of _____

epithelial cells and goblet cells

mucus coats and protects the epithelial cells from what

invasive microorganisms and other potentially damaging substances such as gastric juices

in men, retinol participates in….

sperm production

in women, vitamin A supports…

normal fetal development during pregnancy

beta-carotene plays two primary roles in the body:

serves as a vitamin A precursor; acts as an antioxidant capable of protecting the body against metabolic syndrome and related diseases

90% of vitamin A is stored where

liver

vitamin A status depends on….

adequacy of vitamin A stores; a person’s protein status

when would a healthy adult begin to show vitamin A deficiency symptoms

1-2 years after stores were depleted

Vitamin A supports immune function and inhibits replication of the ___ virus

measles

what is recommended for children with measles (in relation to vitamin A)

two doses of vitamin A supplements, given 24 hours apart

one of the first detectable signs of vitamin A deficiency

night blindness

what happens with night blindness

a person loses the ability to recover promptly from the temporary blinding that follows a flash of bright light at night or to see after dark

night blindness is caused by a lack of vitamin A at this part of the eye

the back

total blindness is caused by a lack of vitamin A at this part of the eye

the front (cornea)

what is the official term for blindness

xerophthalmia

what is the first stage of blindness due to a vitamin A deficiency

xerosis

what is xerosis

cornea becomes dry and hard because of inadequate mucus production

xerosis quickly progress into…

keratomalacia

what is keratomalacia

the softening of the cornea that leads to irreversible blindness

keratinization

the epithelial cells of the skin change shape and begin to secrete keratin (vitamin A deficiency condition)

keratin

hard, inflexible protein that is also commonly found in hair and nails

can beta-carotene contribute to a vitamin A toxicity

no

what could happen if you eat too much beta-carotene

could turn skin yellow, but not harmful

high levels of vitamin A may…

weaken the bones and contribute to fractures and osteoporosis

excessive vitamin A during pregnancy increases the risk of birth defects such as…

spina bifida and cleft palate

retinol activity equivalents (RAE)

a measure of vitamin A activity; the amount of retinol that the body will derive from a food containing preformed retinol or its precursor, beta-carotene

one microgram of retinol counts as _ RAE

1

_______ micrograms of dietary beta-carotene counts as 1 RAE

12

the richest sources of the retinoids are foods derived from animals:

liver, fish liver oils, milk and milk products, butter, and eggs

beets and corn derive their colors from the red and yellow _______, which have no vitamin A activity

xanthophylls

how does vitamin D differ from other nutrients

the body can synthesize it, with the help of sunlight, from the body’s precursor (cholesterol)

is vitamin D essential or nonessential

nonessential

another word for vitamin D

calciferol

two major forms of vitamin D:

vitamin D2 (plants), vitamin D3 (animals)

ultraviolet rays from the sun strike a precursor in the skin and convert it to previtamin ______

D3

how is vitamin D activated

hydroxylation reactions: liver adds and OH group, then the kidneys add another OH group to produce the active vitamin

although called a vitamin, the active form of vitamin D is actually…

a hormone

vitamin’s specific role in bone health is to…

assist in the absorption of calcium and phosphorus, thus helping to maintain blood concentrations of these minerals

adequate nutrition and regular exercise are essential to achieving _____ before age 30

peak bone mass

when diet is sufficient, vitamin D does what

enhances mineral absorption from the GI tract

when diet is insufficient, vitamin D does what

provides the needed minerals from other sources

in the brain and nerve cells, vitamin D may….

protect against cognitive decline and slow progression of Parkinson’s disease

vitamin D in muscle cells does what

facilitates growth in children and preserves strength in adults

Vitamin D signals cells of the immune system to…

defend against infectious diseases

vitamin D seems to reduce ______ and may prove valuable in _______

inflammation, treating diseases

most vulnerable for vitamin D insufficiency:

older adults, especially women and those who are Black, obese, physically inactive, or smokers

what happens to the production of calbindin in vitamin D deficiency

slows

what is calbindin

protein that binds calcium in the intestinal cells

a vitamin D deficiency creates a ____ deficiency and increases risk of chronic diseases and osteoporosis

calcium

what happens in rickets

the bones fail to calcify normally, causing growth impairments and skeletal abnormalities; bones become so weak they bend

besides bowed legs, this can be a sign of rickets

beaded ribs

in adults, the poor mineralization of bones results in…

osteomalacia

why is vitamin D deficiency especially likely for elders

• skin, liver, and kidneys lose capacity to make and activate vitamin D

• older adults typically drink little or no milk

• older adults typically spend much of the day indoors

excess blood calcium tends to precipitate in….

the soft tissue, forming stones, especially in the kidneys, which concentrate calcium in an effort to excrete it

For most people, exposing hands, face, and arms on a clear summer day for ____ minutes two or three times a week should be sufficient to maintain vitamin D nutrition

5-10

_____ people require longer sunlight exposure than light-skinned people

dark-skinned

Food sources of vitamin D

fortified milk, egg yolks, and oily fish (salmon, mackerel, and sardines)

the vitamin E family consists of two subgroups:

tocopherols, tocotrienols

of all the members of the vitamin E family, only ____ can meet the body’s ongoing needs for the vitamin

alpha-tocopherol

vitamin E is a fat-soluble ______

antioxidant

vitamin E protects the oxidation of…

polyunsaturated fatty acids and other lipids

This kind of vitamin E deficiency is rare

primary

Vitamin E deficiency is usually associated with…

disease of fat malabsorption such as cystic fibrosis

erythrocyte hemolysis

classic sign of vitamin E deficiency; red blood cells break and spill their contents as the polyunsaturated fatty acids in their membranes become oxidized

prolonged vitamin E deficiency can cause…

neuromuscular dysfunction

major vitamin E deficiency condition

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UL for vitamin E

1000 milligrams

extremely high doses of vitamin E may interfere with…

blood-clotting action of vitamin K

food sources of vitamin E

vegetable oils, wheat germ oil, seeds, nuts

vitamin E is readily destroyed by…

heat and oxidation

primary action of vitamin K

blood clotting

vitamin K activates ____, which is made by the liver as a precursor of the protein thrombin

prothrombin

vitamin K deficiency

hemorrhagic disease

genetic disorder that results in hemorrhaging and is not affected by vitamin K

hemophilia

Vitamin K participates in the metabolism of bone proteins, most notably ______

osteocalcin

how are bones affected by vitamin K deficiency

osteocalcin cannot bind with the minerals that normally form bones, and therefore results in low bone density