Chapter 11: Fat Soluble Vitamins

How are fat soluble vitamins different to water soluble vitamins?

1. require bile for digestion and absorption

2. travel through the lymphatic system

3. excesses are stored in the liver and adipose tissues

3. they are not readily excreted (increases risk of toxicity)

How many vitamins use letters in the alphabet?

A, B, C, D, E, and K

(F,G,H were dropped)

Classification of a vitamin is based on what?

solubility

fat soluble = A,D,E, and K

What is provitamin A?

preformed vitamin A is called provitamin A

- biologically active

What is the precursor name for vitamin A?

previtamin

- beta carotene

- needs to be transformed to be active

What are the three types of provitamin A?

- retinol (alcohol group = OH)

- retinal (aldehyde group = COH)

- retinoic acid (acid group = COOH)

True or false? A cell in the body can convert retinol and retinal to the other active forms of vitamin A.

true

Can retinoic acid be converted more than once?

no

- one way track

Where is provitamin A found?

only animal products

- liver, egg yolk, milk, and milk products

Where are previtamin A carotenoid forms found?

plants

- orange and dark green vegetables

- carrots, squash, spinach, and broccoli)

How is vitamin A and carotenoids digested/absorbed?

intestine --> liver

- carried by lipoproteins called chylomicrons

What is the name of the transport protein that moved Vitamin A through the blood from the liver?

Retinol-binding protein (RBP)

Functions of Vitamin A

1. helps with vision

2. protein synthesis in epithelial tissue

3. supports reproduction

Function of retinol

- supports reproduction

- major transport and storage form of vitamin A

Function of retinal

- active in vision

- an intermediate in conversion of retinol --> retinoic acid

Function of retinoic acid

- act like a hormone

- regulates cell differentiation

- growth and embryonic development

What are the two roles of vitamin A in the eye?

1. helps maintain clearness of the cornea

2. helps with conversion of light energy into nerve impulses of the retina

What happens if vitamin A is missing from the cornea?

cornea becomes dull and dry

- appearance of the conjunctiva with slight wrinkling

What is a dull cornea and dry appearance caused by?

loss of goblet cells and insufficient mucin secretion

- conjunctival xerosis

What cells are in the eye?

photosensitive cells

- contain rhodopsin

What is the role of vitamin A in the eye?

helps convert light energy to nerve impulses in the retina

What is the role of vitamin A in the skin?

protect the skin against damage

- maintains the integrity of tissues

- promotes differentiation of epithelial & goblet cells

What is the role of vitamin A in reproduction and growth?

- sperm development

- normal fetal development

- growth of children

How does vitamin A remodel bones?

renews bone tissue by helping to dismantle old bone

What are the two primary roles of beta-carotene?

- vitamin A precursor

- acts as an antioxidant capable of defending against disease

What does vitamin A status depend on?

- adequacy of where it's stored (the liver)

- protein status

What organ is the main place that vitamin A is stored?

the liver

What are some consequences of vitamin A deficiency?

- risk of infectious diseases

- night blindness and blindness

- death

What is hyperkeratinization?

keratin accumulates around hair follicles

- general keratin over accumulation, makes the skin rough

What happens in the GI tract with a vitamin A deficiency?

-goblet cells diminish

- digestion and absorption are impeded

- worsens already present malnutrition

Keratinization increases the risk of infection is what places?

-respiratory tract

-GI tract

-urinary tract

-vagina

-inner ear

Vitamin A supports the immune system function and inhibits the replication of what virus?

measles

What infections other than measles is vitamin A good at inhibiting?

- malaria

- lung disease

- HIV

What are some signs that someone is vitamin A deficient when you look at their eyes?

- night blindness

- xerophthalmia

- bitot spots

What are bitot spots?

buildup of keratin located superficially in the conjunctiva

What is bright blindness?

- losing the ability to recover promptly from bright flashing lights in the dark

- due to lack of vitamin A in the eye

What is xeophthalbia (blindness)?

- total failure to see at night

- lack of vitamin A at FRONT of eye

Describe the two stages of blindness development

1. cornea becomes dry and hard due to lack of mucus

2. xerosis progresses- softening of cornea (keratomalacia) leading to irreversible blindess

Where can vitamin A toxicity come from?

- preformed vitamin A from animal sources

- fortified foods

- supplements

Who are most vulnerable to vitamin A toxicity?

children

What are some symptoms of vitamin A toxicity?

- bone defects

- birth defects

Excess intake of vitamin A is most damaging when during a pregnancy?

early stages (before 7th week)

What is the tolerable upper limit for vitamin A?

3000 micrograms/day

What is the Recommended Dietary Allowance for vitamin A?

man: 900 micrograms RAE/day

woman: 700 micrograms RAE/day

What is the retinol activity equivalents for vitamin A and beta carotene?

vitamin A = 1 microgram: 1 RAE

beta carotene = 12 micrograms = 1 RAE

What is vitamin D also known as?

calciferol

What are the two isoforms of vitamin D?

- ergocalciferol (D2); from plant derived foods

- cholecalciferol (D3); from animal derived foods

How does vitamin D differ from other vitamins?

the body can synthesize vitamin D

- does this via exposure to sunlight

- from a precursor the body makes from cholesterol

What needs to happen to vitamin D before it is fully functional?

vitamin D from the skin and diet must be activated before fully functiona;

Where do the (OH+) reactions that activate vitamin D occur?

first in the liver, then in the kidneys

How does the active form of vitamin D act like a hormone?

produced in one part of the body and travels in the blood to act on other parts

What important role does vitamin D have in the bones?

assists in the absorption of calcium and phosphorus

What are the main functions of vitamin D?

- bone growth

- cognitive action (brain and nerve function)

- regulate adipose tissue cells

- immune system

What vitamins, hormones, protein, and minerals assist vitamin D in bone making?

- vitamin A

- vitamin K

- parathyroid hormone

- calcitonin hormone

- collagen protein

- calcium, phosphorus, magnesium. and fluoride

In what 3 ways does vitamin D raise bone making minerals?

1. raises mineral absorption from the GI

2. reabsorption of mineral by the kidneys

3. mobilization of minerals from the bone

(actions 2 and 3 if diet is low in minerals)

How does vitamin D function in the brain and nerve cells?

- protects against cognitive decline

- slows the progression of Parkinsons disease

How does vitamin D function in muscle cells?

- helps children grow

- preserves strength in adults

How does vitamin D function in the immune system?

promotes signal cells of the immune system to defend against infectious disease

How does vitamin D function in adipose tissue?

influence obesity development

How does vitamin D regulate the expression of genes?

has a role in some chronic diseases, metabolic disease, and cancer

Almost __% of Americans are vitamin D deficient

10%

A vitamin D deficiency subsequently causes a _______ deficiency

calcium

List 4 factors that could contribute to Vitamin D deficiency

1. lack of sunlight

2. dark skin

3. breastfeeding without supplementation

4. not consuming fortified milk

What protein is reduced when vitamin D deficiency occurs?

calbindin

- protein that binds calcium

- absorption of calcium is insufficient even if diet is adequate

Vitamin D deficiency is adolescents may prevent reaching peak ____ mass

bone

What are some symptoms of vitamin D deficiency?

- rickets/bowed legs

- failure of bone calcification

What is it called in rickets, when a series of "beads" develop where cartilage and bone attach?

beaded ribs

- poorly formed attachment

Define osteomalacia

affects adults

- poor mineralization

- causes soft, brittle, and deformed bones

Define osteoporosis

loss of calcium

- form bones which results in fractures

- often result from calcium loss from bones

Why are the elderly at high risk of vitamin D deficiency?

- skin, liver, and kidneys lose their ability to make and activate vitamin D as people age

- reduced milk consumption

- less exposure to the sun

What are foods that can be sources of vitamin D?

oily fish, egg yolks, and fortified milk

What is the recommended dietary allowance (RDA) for vitamin D?

adults- 15 micrograms /day or 600 IU/day

elderly- 20 micrograms/day or 800 IU/day

vitamin D is among the ____ likely of the vitamins to have toxic effects

most

What happens to the body when vitamin D toxicity takes place?

- raises blood calcium concentrations

- precipitates and forms stones in kidneys

- may harden blood vessels

- can cause death

What are the two subgroups of vitamin E

tocopherols and tocotrienols

- only alpha tocopherol is maintained in the body

the two subgroups of vitamin E contain what four compounds?

alpha, beta, gamma, and delta

What is the natural form of vitamin E?

alpha-D form

ex. plant oils, wheat germ, some fruits/vegetables, meat/fish

What is the DRI for vitamin E?

15mg/day

What is the most potent form of vitamin E?

a-tocopherol

Supplements that are made from entirely natural sources contain what type of alpha-tocopherol?

d-alpha-tocopherol

What is the synthetic supplement of vitamin E?

dL-tocopherol

- isomer of d-alpha-tocopherol

- less active than natural vitamin E

What is the most bioavailable form of alpha-tocopherol?

alpha-tocopherol

- the type that is preferred for use by you body

- better absorbed and utilized than other forms

what is chronic inflammation a symptom of?

many chronic diseases

- obesity

- diabetes

- cancer

- arthritis

- alzheimers disease

- cardiovascular disease

because vitamin E is an antioxidant and can reduce inflammation it is believed that...

it protects against chronic diseases

How does vitamin E prevent diabetes?

can improve insulin activity

- increase glucose assimilation in tissues

Primary deficiency of vitamin E is ____ (from the diet)

rare

Secondary deficiency of vitamin E effects

- fat malabsorption

- red blood cells break open

- erythrocyte hemolysis

- neuromuscular dysfunction

Extremely high doses of vitamin E may cause...

- interference with vitamin K activity

- hemorrhage

What does vitamin K get its name from?

danish word "koagulation"

- primary role of vitamin K is promoting blood clotting

What are the three sources of vitamin K?

- plant derived foods

- intestinal bacteria

- synthetic form

Describe the primary action of vitamin K?

its required in the cascade of events leading to blood clotting

How does primary deficiency of vitamin K happen?

inadequate dietary intake

- rare

How does secondary deficiency of vitamin K happen?

malabsorption

- if digestion or absorption disrupted: low bile production

- low production from intestinal bacteria: antibiotics kill off vitamin K producing bacteria

Where/what is vitamin K produced in the body?

intestinal bacteria

Which of the fat soluble vitamins has an uncommon chance of being toxic?

vitamin K

- no adverse effects with high intakes

What is an adequate intake for vitamin K?

-120 micrograms/day

-90 micrograms/day

- no UL

- high doses can reduce effectiveness of anticoagulant drugs

What are some dietary sources of vitamin K?

- leafy greens like kale and spinach

- fruits like avocado and kiwi

- vegetable oils

What is a free radical?

any atom or molecule that has an unpaired electron

- unstable and highly reactive

What are the water soluble vitamins?

B and C

What do excess free radicals in the body cause?

oxidative stress