NUTR 2105 Lecture 8: Chapter 9 Fat-Soluble Vitamins
1 May 2018
School
Department
Course
Professor
Vitamins
Tasteless, organic compounds
○
Required in small amounts (remember micronutrient)
○
Functions:
Regulate metabolism
§
Help convert energy in fat, carb, and protein to ATP
§
Promote growth and reproduction
§
○
Deficiencies can result in potentially serious symptoms
Deficiencies will be on test*
§
○
-
Vitamins Were Discovered about One Hundred Years Ago
Diseases caused by vitamin deficiency and the foods that helped them
were recognized long before vitamins were discovered
○
In the 18th century, acid in citrus fruit was noted to cure the symptoms of
scurvy in British sailors
○
In early 1900s, scientists discovered that thiamin cured beriberi and
vitamin D cured rickets
○
Scientists are now focusing on prevention of disease w/ vitamin research
(instead of curing)
○
Each new vitamin was given a temporary name when it was discovered
○
The naming of the vitamins follows the letters of the alphabet starting w/
A, now we're on K
A, B, C, D, E, and K
§
Vitamins F, G, and H were dropped
§
○
Nomenclature changed when vitamin B was found to have several
functions
Subscripts were added for each new isolated role
§
○
-
There Are Criteria for Designating Vitamins
Cannot be synthesized in ample amounts in body
○
Chronic deficiency is likely to cause physical symptoms
○
Symptoms will disappear once the vitamin level in the body is restored
Deficiency can cause permanent damage
§
○
13 compounds meet the above criteria
○
Vitamins are classified based on solubility
9 water-soluble:
B vitamin complex□
Vitamin C□
§
4 fat-soluble:
Vitamin A□
Vitamin D □
Vitamin E□
Vitamin K□
§
Solubility influences a vitamin's:
Digestion □
Absorption □
Transportation□
Storage □
Excretion □
§
○
-
All Vitamins Are Organic, but Differ in Structure and Function
All vitamins have C, H and O
Some vitamins contain N and S
§
○
Chemical structure of each vitamin is unique
○
Each vitamin is a singular unit
○
Vitamins are absorbed intact
○
Vitamins perform numerous essential functions
○
Some vitamins have more than one role in metabolism
○
-
Provitamins Can Be Converted to Active Vitamins by the Body
Provitamins
Substances found in foods that are not directly usable by the body
§
Converted to an active form once absorbed
§
Ex. Beta-carotene to vitamin A
§
○
Preformed vitamins
Found in foods in their active form
She will refer to preformed vitamins as active vitamins*□
§
Do not need to be converted
§
○
-
Overconsumption of Some Vitamins Can Be Toxic
Vitamin toxicity (hypervitaminosis):
Rare
§
Results from ingesting excess vitamins, which leads to tissue
saturation
§
Can damage cells, sometimes permanently
§
Results from supplementing w/ megadoses of vitamins, does not
occur from eating foods*
§
Not documented well
§
○
The Dietary Reference Intakes includes a UL for most vitamins
○
-
How Do Vitamins Differ in Their Absorption and Storage?
All absorption happens in the small intestine
○
Fat-soluble and water-soluble vitamins differ in:
Absorption
§
Bioavailability: degree at which vitamin is absorbed and
subsequently used by the body
§
○
Vitamins Differ in Bioavailability
Varies based on
Amount in food□
Preparation□
Efficiency of digestion and absorption of food□
Individual nutrition status (if deficient, for ex. Fe in females
typically, bioavailability will be higher [body will help you out
and absorb more])
□
Natural or synthetic (normally natural is more bioavailable but
sometimes supplements more bioavailable)
□
§
Fat-soluble vitamins are generally less bioavailable than water-
soluble vitamins
§
Vitamins from plant foods are generally less bioavailable than those
in animal foods
§
○
Fat-Soluble Vitamins are stored after they are absorbed
Absorption
Attached to proteins in food, released in the stomach□
Are absorbed in the duodenum□
Packaged in chylomicrons --> lymph --> bloodstream□
Lack of fat can lead to deficiency □
§
Storage
The liver is the main storage site for vitamin A; to a lesser
extent for vitamins K and E
□
Vitamin D is mainly stored in the fat and muscle tissue□
Can build up in the body to the point of toxicity □
§
○
Water-Soluble Vitamins are not stored after absorption
Absorption
Absorbed w/ water and enter directly into the bloodstream □
Most absorbed in the duodenum and jejunum □
§
Excretion
Not stored in the body□
Excess intake excreted through the urine □
§
Important to consume adequate amounts daily
§
Dietary excesses can be harmful
§
○
-
What Are Antioxidants?
Group of compounds that neutralize free radicals, helping to counteract
the oxidation that takes place in cells
○
Antioxidant-rich foods also contain other protective compounds
○
These sources also act as antioxidants, stimulate the immune system, and
interact w/ hormones to prevent cancers
Phytochemicals are naturally occurring plant compounds
Carotenoids□
Flavonoids □
§
Antioxidants and phytochemicals from the diet have more health
benefits than those from supplements (the way they are arranged
and stuff)
§
○
Includes:
Vitamin E
§
Vitamin C
§
Selenium
§
Flavonoids
§
Carotenoids
§
○
Free radicals
By-products of body's metabolic reactions
§
Molecules w/ unpaired e-, which makes them unstable
§
Factors that increase free radical production:
UV light□
Exposure to toxins from smoking□
Exposure to environmental pollutants□
§
Oxidative stress occurs when free radicals accumulate faster than
the body can metabolize them
Damages DNA and body proteins, and alters cell structure□
Excess free radicals contribute to chronic diseases
Heart disease
®
Cancer
®
Aging
®
Diabetes
®
Parkinson's disease
®
Alzheimer's disease
®
□
§
○
Age-related macular degeneration (AMD)
Free radical damage to the macula in the eye
§
Most common cause of vision impairment in Americans over 60
years
§
AMD risk and loss of vision may be reduced w/ supplementation
Vitamin C, vitamin E, beta-carotene□
Zinc and Copper□
§
○
Cataracts
Lens of eye becomes cloudy; common eye disorder in older adults
§
○
-
What Are the Best Sources of Vitamins?
Whole foods
Fruits, vegetables, and whole grains
§
Rich in vitamins, phytochemicals, antioxidants, and fiber
§
○
Dietary Guidelines for Americans recommends:
Eat a wide variety of foods from each food group, w/ ample
amounts of vitamin-rich fruits, vegetables, whole grains, and dairy
foods
§
Most people do not needs supplements
§
○
Vitamins Can Be Destroyed during Cooking or Storage
Exposure to oxygen
Water-soluble vitamins □
Vitamins A, E, and K□
§
Exposure to ultraviolet light
Riboflavin □
Beta-carotene and vitamin C□
§
Water
Most water-soluble vitamins□
§
Changes in pH
Thiamin and vitamin C□
§
Heat
Most water-soluble vitamins, especially vitamin C□
§
Vegetables and fruits begin to lose vitamins almost immediately
after being harvested and some preparation and storage methods
can accelerate vitamin loss
§
Fat-soluble vitamins tend to be more stable than water-soluble
vitamins
§
○
Some foods are fortified w/ vitamins
Voluntary addition of nutrients by manufacturers in order to:
To enhance nutrient quality of food□
Prevent or correct dietary deficiencies□
Ensure adequate intake for some individuals□
§
Enrichment is a form of fortification
Can contribute to health risks
Lead to vitamin excess
®
Displace nutrient-rich foods
®
□
§
○
-
Vitamin A
What is it?
A family of fat-soluble retinoids (retinol, retinal, retinoic acid)
§
Performed vitamin A (retinyl ester) is found primarily in animal
foods
§
Some plants contain provitamin A compounds, which are converted
to retinol in your body
Beta-carotene is split into 2 molecules of retinal□
Carotenoids, including beta-carotene, are pigments that give
color to carrots, butternut squash, and cantaloupe
□
§
○
Absorption and Transport
All forms of vitamin A are absorbed by active transport w/ bile salts
and micelles
§
Beta-carotene (don't have to really know for test) is absorbed by
passive diffusion
Reduced w/ high fiber intake□
Improved in cooked foods□
§
Most forms of vitamin A are packaged into chylomicrons enter
lymph
§
Retinoic acid is attached to albumin and transported to the liver via
portal vein
§
Stored in liver
§
○
Metabolic Functions
Participates in:
Vision (retinol in blood converted to retinal to replenish once
light bleaches rod)
□
Protein synthesis and cell differentiation (for healthy
epithelial cells which is skin and line inside of all organs)
□
Reproduction□
Bone health□
A healthy immune system□
§
May help fight cancer
Carotenoids are antioxidants□
§
○
Daily Needs
Don't need to know the numbers for the test
§
○
Food Sources
Orange foods: carrots, butternut squash, cantaloupe, etc.
§
○
Vitamin A Toxicity
Excessive amounts of preformed vitamin A can accumulate to toxic
levels
Again via supplementation, not food intake□
>15,000 micrograms can cause symptoms of toxicity□
Hypervitaminosis A can lead to liver damage and even death□
§
Overconsumption
During pregnancy can cause birth defects in face, skull, and
CNS of child
□
Can potentially result in osteoporosis and bone fractures in
adults
□
§
Carotenoids in food are not toxic
Do not pose serious health problems□
Excess carotenoids can cause carotenodermia □
§
Overconsuming beta-carotene supplements
May increase a smoker's lung cancer risk□
§
○
Vitamin A Deficiency
Chronic vitamin A deficiency causes night blindness (can't see in
dark)
§
Prolonged vitamin A deficiency leads to xerophthalmia
Leading cause of preventable blindness in children, mostly in
developing countries
□
§
Deficiency can lead to keratinization of epithelial tissues
Epithelial cells don't secrete mucus□
Cells are unable to function properly, promoting infection□
§
○
-
Vitamin D
What is it?
"sunshine vitamin"
§
Derived from a reaction b/w UV rays and a form of cholesterol in
the skin
Exposure to sunlight can synthesize all of the body's vitamin D
needs
Considered a conditionally essential nutrient
®
□
§
Considered a prohormone
§
Found in two forms (won't ask about)
Cholecalciferol (vitamin D3): produced in the skin and found
in animal foods
When looking at supplements, this is better
®
□
Ergocalciferol (vitamin D2): found in plants and dietary
supplements
□
§
○
Metabolism of Vitamin D
○
Metabolic Functions of Vitamin D
Bone growth
Calcitriol stimulates intestinal Ca and phosphorous absorption□
Maintains healthy ratio of Ca and phosphorous in the blood□
Controls interaction b/w osteoblasts (bone building cells) and
osteoclasts (break cells down to release Ca to keep blood
levels at homeostasis)
□
§
May prevent some cancers
Incidence of breast, colon, and prostate cancer is higher in
individuals living in sun-poor areas of the world
□
§
Potentially helps reduce risk of some autoimmune disorders
§
May prevent diabetes (big area of research)
May reduce type 1 diabetes risk by 50% in adults□
Type 2 diabetes is associated w/ low blood vitamin D levels□
§
May regulate blood pressure
§
○
Daily Needs of Vitamin D
Sun exposure cannot meet everyone's vitamin D needs
The skin pigment melanin (this is what gives you color, so if
you tan really easy then don't make as much vitamin D) and
use of sunscreens reduce vitamin D production
□
Sunlight intensity during winter in some locations is not
sufficient to make enough vitamin D
□
§
Vitamin D needs based on dietary sources
§
○
Food Sources of Vitamin D
Not a lot but fatty fish is a source, also eggs and mushrooms have a
little bit
§
○
Vitamin D Toxicity
A high intake can cause loss of appetite, nausea, vomiting, and
constipation
§
Overuse of supplements may lead to hypervitaminosis D
§
Hypercalcemia
Can cause damaging Ca deposits in kidneys, lungs, blood
vessels, and heart
□
Can affect the NS and cause severe depression□
§
Too high levels are rarely caused by food intake (again only via
supplementation) or overexposure to the sun (can get skin cancer
but there's a shut off mechanism for making vitamin D)
§
○
Vitamin D Deficiency
Rickets: vitamin D deficiency disease in children
Bones aren't adequately mineralized w/ Ca and P, causing
them to weaken, leading them to have bowed legs
□
On the rise in U.S. due to decreased milk consumption, fear of
skin cancer from sun exposure, and air pollution
□
§
Other vitamin D deficiency disorders
Osteomalacia: adult equivalent of rickets□
Osteoporosis: condition where bones don't mineralize
properly
□
Muscle and bone weakness and pain□
§
○
-
Vitamin E
What is Vitamin E?
Alpha-tocopherol is the most active form in the body
§
The synthetic form in supplements is only half as active as the
natural form
§
○
Vitamin E Absorption and Transport
Absorbed w/ bile salts and micelles
§
Packaged in chylomicrons --> lymph --> circulation --> liver
§
90% of vitamin E is stored in adipose tissue
§
○
Metabolic Functions of Vitamin E
Acts as powerful antioxidant
Protects cell membranes□
Prevents oxidation of LDL cholesterol (bad cholesterol)□
§
Acts as an anticoagulant, inhibiting formation of harmful clots inside
bloodstream
§
No evidence supporting a role in prevention of cancer or other
diseases has been conclusively identified
§
○
Daily Needs of Vitamin E
○
Food Sources of Vitamin E
Vegetable oils, wheat germ (where the fat lives), nuts and seeds
§
○
Vitamin E Toxicity
No known risk of consuming too much vitamin E from natural food
sources
Overconsumption of supplements and fortified foods can
increase risk of a hemorrhage
□
§
○
Vitamin E Deficiency
Rare
§
Chronic deficiency of vitamin E can cause nerve problems, muscle
weakness, and free radical damage to cell membranes
§
○
-
Vitamin K
What is vitamin K?
3 forms of vitamin K
Phylloquinone is found in green plants□
Menaquinone is synthesized by intestinal bacteria□
Menadione is the synthetic form□
§
○
Vitamin K Absorption and Transport
Most vitamin K is absorbed in the jejunum
§
10% of vitamin K is produced by bacteria in the colon
§
Vitamin K is incorporated into chylomicrons and transported to the
liver
§
When a diet is deficient in vitamin K
Storage forms are transported by VLDL, LDL, and HDL□
§
Stored mostly in the liver
§
○
Metabolic Functions of Vitamin K
Promotes blood clotting
Involved in synthesizing four blood-clotting factors
Don't need to know
®
□
§
Promotes strong bones
Assists w/ the carboxylation of other proteins□
Interacts w/ proteins osteocalcin and matrix Gla protein,
which is essential for the formation of a strong bone matrix
□
§
○
Daily Needs of Vitamin K
Recommendations are based on current consumption, b/c the
amount contributed by intestinal synthesis is unknown
§
○
Food Sources of Vitamin K
○
Vitamin K Toxicity
No known adverse effects
§
Individuals taking anticoagulant medications should keep
Changes in intake can increase or decrease drug effectiveness□
§
○
Vitamin K Deficiency
Infants are born w/ too little vitamin K
§
Deficiency severe enough to affect blood clotting is extremely rare
§
May cause hip fracture in older men and women
§
○
-
Are Vitamin Supplements Necessary for Good Health?
Supplements
No evidence supports the use of supplements preventing chronic
diseases or cognitive decline
§
Not a substitute for healthy eating
§
Can cause adverse side effects
§
Are not regulated like drugs and do not require FDA approval to be
put on the market
Supplements can't be removed unless they have been shown
to be unsafe or cause harm
□
§
○
How to choose a supplement
Choose supplements w/ U.S. Pharmacopeial Convention seal (USP)
§
Read the label carefully
§
○
May be helpful for some individuals (LOOK AT THIS FOR MASTERING
Pregnant and lactating women
§
Older individuals who need vitamin B12
§
Individuals who lack dietary vitamin D or sun exposure
§
Individuals on low-cal diets
§
Strict vegetarians
§
Individuals w/ food allergies or lactose intolerance
§
Individuals who abuse alcohol
§
Individuals who are food insecure
§
Breast-fed infants
§
○
-
Chpt. 9 Fat-Soluble Vitamins
Monday, February 26, 2018
2:02 PM
Vitamins
Tasteless, organic compounds
○
Required in small amounts (remember micronutrient)
○
Functions:
Regulate metabolism
§
Help convert energy in fat, carb, and protein to ATP
§
Promote growth and reproduction
§
○
Deficiencies can result in potentially serious symptoms
Deficiencies will be on test*
§
○
-
Vitamins Were Discovered about One Hundred Years Ago
Diseases caused by vitamin deficiency and the foods that helped them
were recognized long before vitamins were discovered
○
In the 18th century, acid in citrus fruit was noted to cure the symptoms of
scurvy in British sailors
○
In early 1900s, scientists discovered that thiamin cured beriberi and
vitamin D cured rickets
○
Scientists are now focusing on prevention of disease w/ vitamin research
(instead of curing)
○
Each new vitamin was given a temporary name when it was discovered
○
The naming of the vitamins follows the letters of the alphabet starting w/
A, now we're on K
A, B, C, D, E, and K
§
Vitamins F, G, and H were dropped
§
○
Nomenclature changed when vitamin B was found to have several
functions
Subscripts were added for each new isolated role
§
○
-
There Are Criteria for Designating Vitamins
Cannot be synthesized in ample amounts in body
○
Chronic deficiency is likely to cause physical symptoms
○
Symptoms will disappear once the vitamin level in the body is restored
Deficiency can cause permanent damage
§
○
13 compounds meet the above criteria
○
Vitamins are classified based on solubility
9 water-soluble:
B vitamin complex
□
Vitamin C
□
§
4 fat-soluble:
Vitamin A
□
Vitamin D
□
Vitamin E
□
Vitamin K
□
§
Solubility influences a vitamin's:
Digestion
□
Absorption
□
Transportation
□
Storage
□
Excretion
□
§
○
-
All Vitamins Are Organic, but Differ in Structure and Function
All vitamins have C, H and O
Some vitamins contain N and S
§
○
Chemical structure of each vitamin is unique
○
Each vitamin is a singular unit
○
Vitamins are absorbed intact
○
Vitamins perform numerous essential functions
○
Some vitamins have more than one role in metabolism
○
-
Provitamins Can Be Converted to Active Vitamins by the Body
Provitamins
Substances found in foods that are not directly usable by the body
§
Converted to an active form once absorbed
§
Ex. Beta-carotene to vitamin A
§
○
Preformed vitamins
Found in foods in their active form
She will refer to preformed vitamins as active vitamins*
□
§
Do not need to be converted
§
○
-
Overconsumption of Some Vitamins Can Be Toxic
Vitamin toxicity (hypervitaminosis):
Rare
§
Results from ingesting excess vitamins, which leads to tissue
saturation
§
Can damage cells, sometimes permanently
§
Results from supplementing w/ megadoses of vitamins, does not
occur from eating foods*
§
Not documented well
§
○
The Dietary Reference Intakes includes a UL for most vitamins
○
-
How Do Vitamins Differ in Their Absorption and Storage?
All absorption happens in the small intestine
○
Fat-soluble and water-soluble vitamins differ in:
Absorption
§
Bioavailability: degree at which vitamin is absorbed and
subsequently used by the body
§
○
Vitamins Differ in Bioavailability
Varies based on
Amount in food□
Preparation□
Efficiency of digestion and absorption of food□
Individual nutrition status (if deficient, for ex. Fe in females
typically, bioavailability will be higher [body will help you out
and absorb more])
□
Natural or synthetic (normally natural is more bioavailable but
sometimes supplements more bioavailable)
□
§
Fat-soluble vitamins are generally less bioavailable than water-
soluble vitamins
§
Vitamins from plant foods are generally less bioavailable than those
in animal foods
§
○
Fat-Soluble Vitamins are stored after they are absorbed
Absorption
Attached to proteins in food, released in the stomach□
Are absorbed in the duodenum□
Packaged in chylomicrons --> lymph --> bloodstream□
Lack of fat can lead to deficiency □
§
Storage
The liver is the main storage site for vitamin A; to a lesser
extent for vitamins K and E
□
Vitamin D is mainly stored in the fat and muscle tissue□
Can build up in the body to the point of toxicity □
§
○
Water-Soluble Vitamins are not stored after absorption
Absorption
Absorbed w/ water and enter directly into the bloodstream □
Most absorbed in the duodenum and jejunum □
§
Excretion
Not stored in the body□
Excess intake excreted through the urine □
§
Important to consume adequate amounts daily
§
Dietary excesses can be harmful
§
○
-
What Are Antioxidants?
Group of compounds that neutralize free radicals, helping to counteract
the oxidation that takes place in cells
○
Antioxidant-rich foods also contain other protective compounds
○
These sources also act as antioxidants, stimulate the immune system, and
interact w/ hormones to prevent cancers
Phytochemicals are naturally occurring plant compounds
Carotenoids□
Flavonoids □
§
Antioxidants and phytochemicals from the diet have more health
benefits than those from supplements (the way they are arranged
and stuff)
§
○
Includes:
Vitamin E
§
Vitamin C
§
Selenium
§
Flavonoids
§
Carotenoids
§
○
Free radicals
By-products of body's metabolic reactions
§
Molecules w/ unpaired e-, which makes them unstable
§
Factors that increase free radical production:
UV light□
Exposure to toxins from smoking□
Exposure to environmental pollutants□
§
Oxidative stress occurs when free radicals accumulate faster than
the body can metabolize them
Damages DNA and body proteins, and alters cell structure□
Excess free radicals contribute to chronic diseases
Heart disease
®
Cancer
®
Aging
®
Diabetes
®
Parkinson's disease
®
Alzheimer's disease
®
□
§
○
Age-related macular degeneration (AMD)
Free radical damage to the macula in the eye
§
Most common cause of vision impairment in Americans over 60
years
§
AMD risk and loss of vision may be reduced w/ supplementation
Vitamin C, vitamin E, beta-carotene□
Zinc and Copper□
§
○
Cataracts
Lens of eye becomes cloudy; common eye disorder in older adults
§
○
-
What Are the Best Sources of Vitamins?
Whole foods
Fruits, vegetables, and whole grains
§
Rich in vitamins, phytochemicals, antioxidants, and fiber
§
○
Dietary Guidelines for Americans recommends:
Eat a wide variety of foods from each food group, w/ ample
amounts of vitamin-rich fruits, vegetables, whole grains, and dairy
foods
§
Most people do not needs supplements
§
○
Vitamins Can Be Destroyed during Cooking or Storage
Exposure to oxygen
Water-soluble vitamins □
Vitamins A, E, and K□
§
Exposure to ultraviolet light
Riboflavin □
Beta-carotene and vitamin C□
§
Water
Most water-soluble vitamins□
§
Changes in pH
Thiamin and vitamin C□
§
Heat
Most water-soluble vitamins, especially vitamin C□
§
Vegetables and fruits begin to lose vitamins almost immediately
after being harvested and some preparation and storage methods
can accelerate vitamin loss
§
Fat-soluble vitamins tend to be more stable than water-soluble
vitamins
§
○
Some foods are fortified w/ vitamins
Voluntary addition of nutrients by manufacturers in order to:
To enhance nutrient quality of food□
Prevent or correct dietary deficiencies□
Ensure adequate intake for some individuals□
§
Enrichment is a form of fortification
Can contribute to health risks
Lead to vitamin excess
®
Displace nutrient-rich foods
®
□
§
○
-
Vitamin A
What is it?
A family of fat-soluble retinoids (retinol, retinal, retinoic acid)
§
Performed vitamin A (retinyl ester) is found primarily in animal
foods
§
Some plants contain provitamin A compounds, which are converted
to retinol in your body
Beta-carotene is split into 2 molecules of retinal□
Carotenoids, including beta-carotene, are pigments that give
color to carrots, butternut squash, and cantaloupe
□
§
○
Absorption and Transport
All forms of vitamin A are absorbed by active transport w/ bile salts
and micelles
§
Beta-carotene (don't have to really know for test) is absorbed by
passive diffusion
Reduced w/ high fiber intake□
Improved in cooked foods□
§
Most forms of vitamin A are packaged into chylomicrons enter
lymph
§
Retinoic acid is attached to albumin and transported to the liver via
portal vein
§
Stored in liver
§
○
Metabolic Functions
Participates in:
Vision (retinol in blood converted to retinal to replenish once
light bleaches rod)
□
Protein synthesis and cell differentiation (for healthy
epithelial cells which is skin and line inside of all organs)
□
Reproduction□
Bone health□
A healthy immune system□
§
May help fight cancer
Carotenoids are antioxidants□
§
○
Daily Needs
Don't need to know the numbers for the test
§
○
Food Sources
Orange foods: carrots, butternut squash, cantaloupe, etc.
§
○
Vitamin A Toxicity
Excessive amounts of preformed vitamin A can accumulate to toxic
levels
Again via supplementation, not food intake□
>15,000 micrograms can cause symptoms of toxicity□
Hypervitaminosis A can lead to liver damage and even death□
§
Overconsumption
During pregnancy can cause birth defects in face, skull, and
CNS of child
□
Can potentially result in osteoporosis and bone fractures in
adults
□
§
Carotenoids in food are not toxic
Do not pose serious health problems□
Excess carotenoids can cause carotenodermia □
§
Overconsuming beta-carotene supplements
May increase a smoker's lung cancer risk□
§
○
Vitamin A Deficiency
Chronic vitamin A deficiency causes night blindness (can't see in
dark)
§
Prolonged vitamin A deficiency leads to xerophthalmia
Leading cause of preventable blindness in children, mostly in
developing countries
□
§
Deficiency can lead to keratinization of epithelial tissues
Epithelial cells don't secrete mucus□
Cells are unable to function properly, promoting infection□
§
○
-
Vitamin D
What is it?
"sunshine vitamin"
§
Derived from a reaction b/w UV rays and a form of cholesterol in
the skin
Exposure to sunlight can synthesize all of the body's vitamin D
needs
Considered a conditionally essential nutrient
®
□
§
Considered a prohormone
§
Found in two forms (won't ask about)
Cholecalciferol (vitamin D3): produced in the skin and found
in animal foods
When looking at supplements, this is better
®
□
Ergocalciferol (vitamin D2): found in plants and dietary
supplements
□
§
○
Metabolism of Vitamin D
○
Metabolic Functions of Vitamin D
Bone growth
Calcitriol stimulates intestinal Ca and phosphorous absorption□
Maintains healthy ratio of Ca and phosphorous in the blood□
Controls interaction b/w osteoblasts (bone building cells) and
osteoclasts (break cells down to release Ca to keep blood
levels at homeostasis)
□
§
May prevent some cancers
Incidence of breast, colon, and prostate cancer is higher in
individuals living in sun-poor areas of the world
□
§
Potentially helps reduce risk of some autoimmune disorders
§
May prevent diabetes (big area of research)
May reduce type 1 diabetes risk by 50% in adults□
Type 2 diabetes is associated w/ low blood vitamin D levels□
§
May regulate blood pressure
§
○
Daily Needs of Vitamin D
Sun exposure cannot meet everyone's vitamin D needs
The skin pigment melanin (this is what gives you color, so if
you tan really easy then don't make as much vitamin D) and
use of sunscreens reduce vitamin D production
□
Sunlight intensity during winter in some locations is not
sufficient to make enough vitamin D
□
§
Vitamin D needs based on dietary sources
§
○
Food Sources of Vitamin D
Not a lot but fatty fish is a source, also eggs and mushrooms have a
little bit
§
○
Vitamin D Toxicity
A high intake can cause loss of appetite, nausea, vomiting, and
constipation
§
Overuse of supplements may lead to hypervitaminosis D
§
Hypercalcemia
Can cause damaging Ca deposits in kidneys, lungs, blood
vessels, and heart
□
Can affect the NS and cause severe depression□
§
Too high levels are rarely caused by food intake (again only via
supplementation) or overexposure to the sun (can get skin cancer
but there's a shut off mechanism for making vitamin D)
§
○
Vitamin D Deficiency
Rickets: vitamin D deficiency disease in children
Bones aren't adequately mineralized w/ Ca and P, causing
them to weaken, leading them to have bowed legs
□
On the rise in U.S. due to decreased milk consumption, fear of
skin cancer from sun exposure, and air pollution
□
§
Other vitamin D deficiency disorders
Osteomalacia: adult equivalent of rickets□
Osteoporosis: condition where bones don't mineralize
properly
□
Muscle and bone weakness and pain□
§
○
-
Vitamin E
What is Vitamin E?
Alpha-tocopherol is the most active form in the body
§
The synthetic form in supplements is only half as active as the
natural form
§
○
Vitamin E Absorption and Transport
Absorbed w/ bile salts and micelles
§
Packaged in chylomicrons --> lymph --> circulation --> liver
§
90% of vitamin E is stored in adipose tissue
§
○
Metabolic Functions of Vitamin E
Acts as powerful antioxidant
Protects cell membranes□
Prevents oxidation of LDL cholesterol (bad cholesterol)□
§
Acts as an anticoagulant, inhibiting formation of harmful clots inside
bloodstream
§
No evidence supporting a role in prevention of cancer or other
diseases has been conclusively identified
§
○
Daily Needs of Vitamin E
○
Food Sources of Vitamin E
Vegetable oils, wheat germ (where the fat lives), nuts and seeds
§
○
Vitamin E Toxicity
No known risk of consuming too much vitamin E from natural food
sources
Overconsumption of supplements and fortified foods can
increase risk of a hemorrhage
□
§
○
Vitamin E Deficiency
Rare
§
Chronic deficiency of vitamin E can cause nerve problems, muscle
weakness, and free radical damage to cell membranes
§
○
-
Vitamin K
What is vitamin K?
3 forms of vitamin K
Phylloquinone is found in green plants□
Menaquinone is synthesized by intestinal bacteria□
Menadione is the synthetic form□
§
○
Vitamin K Absorption and Transport
Most vitamin K is absorbed in the jejunum
§
10% of vitamin K is produced by bacteria in the colon
§
Vitamin K is incorporated into chylomicrons and transported to the
liver
§
When a diet is deficient in vitamin K
Storage forms are transported by VLDL, LDL, and HDL□
§
Stored mostly in the liver
§
○
Metabolic Functions of Vitamin K
Promotes blood clotting
Involved in synthesizing four blood-clotting factors
Don't need to know
®
□
§
Promotes strong bones
Assists w/ the carboxylation of other proteins□
Interacts w/ proteins osteocalcin and matrix Gla protein,
which is essential for the formation of a strong bone matrix
□
§
○
Daily Needs of Vitamin K
Recommendations are based on current consumption, b/c the
amount contributed by intestinal synthesis is unknown
§
○
Food Sources of Vitamin K
○
Vitamin K Toxicity
No known adverse effects
§
Individuals taking anticoagulant medications should keep
Changes in intake can increase or decrease drug effectiveness□
§
○
Vitamin K Deficiency
Infants are born w/ too little vitamin K
§
Deficiency severe enough to affect blood clotting is extremely rare
§
May cause hip fracture in older men and women
§
○
-
Are Vitamin Supplements Necessary for Good Health?
Supplements
No evidence supports the use of supplements preventing chronic
diseases or cognitive decline
§
Not a substitute for healthy eating
§
Can cause adverse side effects
§
Are not regulated like drugs and do not require FDA approval to be
put on the market
Supplements can't be removed unless they have been shown
to be unsafe or cause harm
□
§
○
How to choose a supplement
Choose supplements w/ U.S. Pharmacopeial Convention seal (USP)
§
Read the label carefully
§
○
May be helpful for some individuals (LOOK AT THIS FOR MASTERING
Pregnant and lactating women
§
Older individuals who need vitamin B12
§
Individuals who lack dietary vitamin D or sun exposure
§
Individuals on low-cal diets
§
Strict vegetarians
§
Individuals w/ food allergies or lactose intolerance
§
Individuals who abuse alcohol
§
Individuals who are food insecure
§
Breast-fed infants
§
○
-
Chpt. 9 Fat-Soluble Vitamins
Monday, February 26, 2018 2:02 PM
Vitamins
Tasteless, organic compounds
○
Required in small amounts (remember micronutrient)
○
Functions:
Regulate metabolism
§
Help convert energy in fat, carb, and protein to ATP
§
Promote growth and reproduction
§
○
Deficiencies can result in potentially serious symptoms
Deficiencies will be on test*
§
○
-
Vitamins Were Discovered about One Hundred Years Ago
Diseases caused by vitamin deficiency and the foods that helped them
were recognized long before vitamins were discovered
○
In the 18th century, acid in citrus fruit was noted to cure the symptoms of
scurvy in British sailors
○
In early 1900s, scientists discovered that thiamin cured beriberi and
vitamin D cured rickets
○
Scientists are now focusing on prevention of disease w/ vitamin research
(instead of curing)
○
Each new vitamin was given a temporary name when it was discovered
○
The naming of the vitamins follows the letters of the alphabet starting w/
A, now we're on K
A, B, C, D, E, and K
§
Vitamins F, G, and H were dropped
§
○
Nomenclature changed when vitamin B was found to have several
functions
Subscripts were added for each new isolated role
§
○
-
There Are Criteria for Designating Vitamins
Cannot be synthesized in ample amounts in body
○
Chronic deficiency is likely to cause physical symptoms
○
Symptoms will disappear once the vitamin level in the body is restored
Deficiency can cause permanent damage
§
○
13 compounds meet the above criteria
○
Vitamins are classified based on solubility
9 water-soluble:
B vitamin complex□
Vitamin C□
§
4 fat-soluble:
Vitamin A□
Vitamin D □
Vitamin E□
Vitamin K□
§
Solubility influences a vitamin's:
Digestion □
Absorption □
Transportation□
Storage □
Excretion □
§
○
-
All Vitamins Are Organic, but Differ in Structure and Function
All vitamins have C, H and O
Some vitamins contain N and S
§
○
Chemical structure of each vitamin is unique
○
Each vitamin is a singular unit
○
Vitamins are absorbed intact
○
Vitamins perform numerous essential functions
○
Some vitamins have more than one role in metabolism
○
-
Provitamins Can Be Converted to Active Vitamins by the Body
Provitamins
Substances found in foods that are not directly usable by the body
§
Converted to an active form once absorbed
§
Ex. Beta-carotene to vitamin A
§
○
Preformed vitamins
Found in foods in their active form
She will refer to preformed vitamins as active vitamins*□
§
Do not need to be converted
§
○
-
Overconsumption of Some Vitamins Can Be Toxic
Vitamin toxicity (hypervitaminosis):
Rare
§
Results from ingesting excess vitamins, which leads to tissue
saturation
§
Can damage cells, sometimes permanently
§
Results from supplementing w/ megadoses of vitamins, does not
occur from eating foods*
§
Not documented well
§
○
The Dietary Reference Intakes includes a UL for most vitamins
○
-
How Do Vitamins Differ in Their Absorption and Storage?
All absorption happens in the small intestine
○
Fat-soluble and water-soluble vitamins differ in:
Absorption
§
Bioavailability: degree at which vitamin is absorbed and
subsequently used by the body
§
○
Vitamins Differ in Bioavailability
Varies based on
Amount in food
□
Preparation
□
Efficiency of digestion and absorption of food
□
Individual nutrition status (if deficient, for ex. Fe in females
typically, bioavailability will be higher [body will help you out
and absorb more])
□
Natural or synthetic (normally natural is more bioavailable but
sometimes supplements more bioavailable)
□
§
Fat-soluble vitamins are generally less bioavailable than water-
soluble vitamins
§
Vitamins from plant foods are generally less bioavailable than those
in animal foods
§
○
Fat-Soluble Vitamins are stored after they are absorbed
Absorption
Attached to proteins in food, released in the stomach
□
Are absorbed in the duodenum
□
Packaged in chylomicrons --> lymph --> bloodstream
□
Lack of fat can lead to deficiency
□
§
Storage
The liver is the main storage site for vitamin A; to a lesser
extent for vitamins K and E
□
Vitamin D is mainly stored in the fat and muscle tissue
□
Can build up in the body to the point of toxicity
□
§
○
Water-Soluble Vitamins are not stored after absorption
Absorption
Absorbed w/ water and enter directly into the bloodstream
□
Most absorbed in the duodenum and jejunum
□
§
Excretion
Not stored in the body□
Excess intake excreted through the urine □
§
Important to consume adequate amounts daily
§
Dietary excesses can be harmful
§
○
-
What Are Antioxidants?
Group of compounds that neutralize free radicals, helping to counteract
the oxidation that takes place in cells
○
Antioxidant-rich foods also contain other protective compounds
○
These sources also act as antioxidants, stimulate the immune system, and
interact w/ hormones to prevent cancers
Phytochemicals are naturally occurring plant compounds
Carotenoids□
Flavonoids □
§
Antioxidants and phytochemicals from the diet have more health
benefits than those from supplements (the way they are arranged
and stuff)
§
○
Includes:
Vitamin E
§
Vitamin C
§
Selenium
§
Flavonoids
§
Carotenoids
§
○
Free radicals
By-products of body's metabolic reactions
§
Molecules w/ unpaired e-, which makes them unstable
§
Factors that increase free radical production:
UV light□
Exposure to toxins from smoking□
Exposure to environmental pollutants□
§
Oxidative stress occurs when free radicals accumulate faster than
the body can metabolize them
Damages DNA and body proteins, and alters cell structure□
Excess free radicals contribute to chronic diseases
Heart disease
®
Cancer
®
Aging
®
Diabetes
®
Parkinson's disease
®
Alzheimer's disease
®
□
§
○
Age-related macular degeneration (AMD)
Free radical damage to the macula in the eye
§
Most common cause of vision impairment in Americans over 60
years
§
AMD risk and loss of vision may be reduced w/ supplementation
Vitamin C, vitamin E, beta-carotene□
Zinc and Copper□
§
○
Cataracts
Lens of eye becomes cloudy; common eye disorder in older adults
§
○
-
What Are the Best Sources of Vitamins?
Whole foods
Fruits, vegetables, and whole grains
§
Rich in vitamins, phytochemicals, antioxidants, and fiber
§
○
Dietary Guidelines for Americans recommends:
Eat a wide variety of foods from each food group, w/ ample
amounts of vitamin-rich fruits, vegetables, whole grains, and dairy
foods
§
Most people do not needs supplements
§
○
Vitamins Can Be Destroyed during Cooking or Storage
Exposure to oxygen
Water-soluble vitamins □
Vitamins A, E, and K□
§
Exposure to ultraviolet light
Riboflavin □
Beta-carotene and vitamin C□
§
Water
Most water-soluble vitamins□
§
Changes in pH
Thiamin and vitamin C□
§
Heat
Most water-soluble vitamins, especially vitamin C□
§
Vegetables and fruits begin to lose vitamins almost immediately
after being harvested and some preparation and storage methods
can accelerate vitamin loss
§
Fat-soluble vitamins tend to be more stable than water-soluble
vitamins
§
○
Some foods are fortified w/ vitamins
Voluntary addition of nutrients by manufacturers in order to:
To enhance nutrient quality of food□
Prevent or correct dietary deficiencies□
Ensure adequate intake for some individuals□
§
Enrichment is a form of fortification
Can contribute to health risks
Lead to vitamin excess
®
Displace nutrient-rich foods
®
□
§
○
-
Vitamin A
What is it?
A family of fat-soluble retinoids (retinol, retinal, retinoic acid)
§
Performed vitamin A (retinyl ester) is found primarily in animal
foods
§
Some plants contain provitamin A compounds, which are converted
to retinol in your body
Beta-carotene is split into 2 molecules of retinal□
Carotenoids, including beta-carotene, are pigments that give
color to carrots, butternut squash, and cantaloupe
□
§
○
Absorption and Transport
All forms of vitamin A are absorbed by active transport w/ bile salts
and micelles
§
Beta-carotene (don't have to really know for test) is absorbed by
passive diffusion
Reduced w/ high fiber intake□
Improved in cooked foods□
§
Most forms of vitamin A are packaged into chylomicrons enter
lymph
§
Retinoic acid is attached to albumin and transported to the liver via
portal vein
§
Stored in liver
§
○
Metabolic Functions
Participates in:
Vision (retinol in blood converted to retinal to replenish once
light bleaches rod)
□
Protein synthesis and cell differentiation (for healthy
epithelial cells which is skin and line inside of all organs)
□
Reproduction□
Bone health□
A healthy immune system□
§
May help fight cancer
Carotenoids are antioxidants□
§
○
Daily Needs
Don't need to know the numbers for the test
§
○
Food Sources
Orange foods: carrots, butternut squash, cantaloupe, etc.
§
○
Vitamin A Toxicity
Excessive amounts of preformed vitamin A can accumulate to toxic
levels
Again via supplementation, not food intake□
>15,000 micrograms can cause symptoms of toxicity□
Hypervitaminosis A can lead to liver damage and even death□
§
Overconsumption
During pregnancy can cause birth defects in face, skull, and
CNS of child
□
Can potentially result in osteoporosis and bone fractures in
adults
□
§
Carotenoids in food are not toxic
Do not pose serious health problems□
Excess carotenoids can cause carotenodermia □
§
Overconsuming beta-carotene supplements
May increase a smoker's lung cancer risk□
§
○
Vitamin A Deficiency
Chronic vitamin A deficiency causes night blindness (can't see in
dark)
§
Prolonged vitamin A deficiency leads to xerophthalmia
Leading cause of preventable blindness in children, mostly in
developing countries
□
§
Deficiency can lead to keratinization of epithelial tissues
Epithelial cells don't secrete mucus□
Cells are unable to function properly, promoting infection□
§
○
-
Vitamin D
What is it?
"sunshine vitamin"
§
Derived from a reaction b/w UV rays and a form of cholesterol in
the skin
Exposure to sunlight can synthesize all of the body's vitamin D
needs
Considered a conditionally essential nutrient
®
□
§
Considered a prohormone
§
Found in two forms (won't ask about)
Cholecalciferol (vitamin D3): produced in the skin and found
in animal foods
When looking at supplements, this is better
®
□
Ergocalciferol (vitamin D2): found in plants and dietary
supplements
□
§
○
Metabolism of Vitamin D
○
Metabolic Functions of Vitamin D
Bone growth
Calcitriol stimulates intestinal Ca and phosphorous absorption□
Maintains healthy ratio of Ca and phosphorous in the blood□
Controls interaction b/w osteoblasts (bone building cells) and
osteoclasts (break cells down to release Ca to keep blood
levels at homeostasis)
□
§
May prevent some cancers
Incidence of breast, colon, and prostate cancer is higher in
individuals living in sun-poor areas of the world
□
§
Potentially helps reduce risk of some autoimmune disorders
§
May prevent diabetes (big area of research)
May reduce type 1 diabetes risk by 50% in adults□
Type 2 diabetes is associated w/ low blood vitamin D levels□
§
May regulate blood pressure
§
○
Daily Needs of Vitamin D
Sun exposure cannot meet everyone's vitamin D needs
The skin pigment melanin (this is what gives you color, so if
you tan really easy then don't make as much vitamin D) and
use of sunscreens reduce vitamin D production
□
Sunlight intensity during winter in some locations is not
sufficient to make enough vitamin D
□
§
Vitamin D needs based on dietary sources
§
○
Food Sources of Vitamin D
Not a lot but fatty fish is a source, also eggs and mushrooms have a
little bit
§
○
Vitamin D Toxicity
A high intake can cause loss of appetite, nausea, vomiting, and
constipation
§
Overuse of supplements may lead to hypervitaminosis D
§
Hypercalcemia
Can cause damaging Ca deposits in kidneys, lungs, blood
vessels, and heart
□
Can affect the NS and cause severe depression□
§
Too high levels are rarely caused by food intake (again only via
supplementation) or overexposure to the sun (can get skin cancer
but there's a shut off mechanism for making vitamin D)
§
○
Vitamin D Deficiency
Rickets: vitamin D deficiency disease in children
Bones aren't adequately mineralized w/ Ca and P, causing
them to weaken, leading them to have bowed legs
□
On the rise in U.S. due to decreased milk consumption, fear of
skin cancer from sun exposure, and air pollution
□
§
Other vitamin D deficiency disorders
Osteomalacia: adult equivalent of rickets□
Osteoporosis: condition where bones don't mineralize
properly
□
Muscle and bone weakness and pain□
§
○
-
Vitamin E
What is Vitamin E?
Alpha-tocopherol is the most active form in the body
§
The synthetic form in supplements is only half as active as the
natural form
§
○
Vitamin E Absorption and Transport
Absorbed w/ bile salts and micelles
§
Packaged in chylomicrons --> lymph --> circulation --> liver
§
90% of vitamin E is stored in adipose tissue
§
○
Metabolic Functions of Vitamin E
Acts as powerful antioxidant
Protects cell membranes□
Prevents oxidation of LDL cholesterol (bad cholesterol)□
§
Acts as an anticoagulant, inhibiting formation of harmful clots inside
bloodstream
§
No evidence supporting a role in prevention of cancer or other
diseases has been conclusively identified
§
○
Daily Needs of Vitamin E
○
Food Sources of Vitamin E
Vegetable oils, wheat germ (where the fat lives), nuts and seeds
§
○
Vitamin E Toxicity
No known risk of consuming too much vitamin E from natural food
sources
Overconsumption of supplements and fortified foods can
increase risk of a hemorrhage
□
§
○
Vitamin E Deficiency
Rare
§
Chronic deficiency of vitamin E can cause nerve problems, muscle
weakness, and free radical damage to cell membranes
§
○
-
Vitamin K
What is vitamin K?
3 forms of vitamin K
Phylloquinone is found in green plants□
Menaquinone is synthesized by intestinal bacteria□
Menadione is the synthetic form□
§
○
Vitamin K Absorption and Transport
Most vitamin K is absorbed in the jejunum
§
10% of vitamin K is produced by bacteria in the colon
§
Vitamin K is incorporated into chylomicrons and transported to the
liver
§
When a diet is deficient in vitamin K
Storage forms are transported by VLDL, LDL, and HDL□
§
Stored mostly in the liver
§
○
Metabolic Functions of Vitamin K
Promotes blood clotting
Involved in synthesizing four blood-clotting factors
Don't need to know
®
□
§
Promotes strong bones
Assists w/ the carboxylation of other proteins□
Interacts w/ proteins osteocalcin and matrix Gla protein,
which is essential for the formation of a strong bone matrix
□
§
○
Daily Needs of Vitamin K
Recommendations are based on current consumption, b/c the
amount contributed by intestinal synthesis is unknown
§
○
Food Sources of Vitamin K
○
Vitamin K Toxicity
No known adverse effects
§
Individuals taking anticoagulant medications should keep
Changes in intake can increase or decrease drug effectiveness□
§
○
Vitamin K Deficiency
Infants are born w/ too little vitamin K
§
Deficiency severe enough to affect blood clotting is extremely rare
§
May cause hip fracture in older men and women
§
○
-
Are Vitamin Supplements Necessary for Good Health?
Supplements
No evidence supports the use of supplements preventing chronic
diseases or cognitive decline
§
Not a substitute for healthy eating
§
Can cause adverse side effects
§
Are not regulated like drugs and do not require FDA approval to be
put on the market
Supplements can't be removed unless they have been shown
to be unsafe or cause harm
□
§
○
How to choose a supplement
Choose supplements w/ U.S. Pharmacopeial Convention seal (USP)
§
Read the label carefully
§
○
May be helpful for some individuals (LOOK AT THIS FOR MASTERING
Pregnant and lactating women
§
Older individuals who need vitamin B12
§
Individuals who lack dietary vitamin D or sun exposure
§
Individuals on low-cal diets
§
Strict vegetarians
§
Individuals w/ food allergies or lactose intolerance
§
Individuals who abuse alcohol
§
Individuals who are food insecure
§
Breast-fed infants
§
○
-
Chpt. 9 Fat-Soluble Vitamins
Monday, February 26, 2018 2:02 PM
Document Summary
Help convert energy in fat, carb, and protein to atp. Vitamins were discovered about one hundred years ago. Diseases caused by vitamin deficiency and the foods that helped them were recognized long before vitamins were discovered. In the 18th century, acid in citrus fruit was noted to cure the symptoms of scurvy in british sailors. In early 1900s, scientists discovered that thiamin cured beriberi and vitamin d cured rickets. Scientists are now focusing on prevention of disease w/ vitamin research (instead of curing) Each new vitamin was given a temporary name when it was discovered. The naming of the vitamins follows the letters of the alphabet starting w/ Nomenclature changed when vitamin b was found to have several functions. Subscripts were added for each new isolated role. Cannot be synthesized in ample amounts in body. Chronic deficiency is likely to cause physical symptoms. Symptoms will disappear once the vitamin level in the body is restored.
