Nutrition Exam 3 (FINAL exam)

vitamins

• complex organic compounds that regulate certain metabolic processes

• they are essential nutrients 

How do vitamins differ from macronutrients?

• they are not metabolized for energy

• they are present in foods in smaller amounts

• recommended amounts to consume are smaller, mg (milligrams) or mcg (micrograms)

Classifying of vitamins

vitamins are divided into 2 groups based on their solubility in either water OR fat

Fat-soluble vitamins

vitamins A, D, E, & K

Characteristics of fat-soluble vitamins 

digested and absorbed with fats; stored primarily in the liver and adipose tissue and over time they can accumulate and cause a toxicity disorder that can damage cells

Water- soluble vitamins

• ALL B vitamins (8 of them: riboflavin(B2), niacin (B3), biotin, pantothenic acid, vitamin B6, folic acid, & vitamin B12)

• Vitamin C

Characteristics of water- soluble vitamins

dissolve in watery components of body; stored in limited amounts (except B12); the kidneys filter excess and eliminate them in urine; they are less likely to be toxic

How do we obtain the needed vitamins?

• by eating foods from the “5” food groups and oils

• also from fortification and enrichment 

Which food groups lack B12?

fruits, vegetables, and grains

Which food groups are low in vitamin C?

grains, proteins, and dairy

Government mandated enrichment of vitamins in milk and grains:

• milk: lower fat versions are required to be enriched with vitamin A. vitamin D is voluntarily added to most milk.

• refined grains/ grain products: required to be enriched with iron and certain B vitamins (thiamin, riboflavin, niacin, & folic acid)

• NOTE: enrichment does NOT replace all vitamins and minerals lost in the refining process of grains.

Voluntary fortification (not mandatory) concern

risk of exceeding the tolerable intake levels (ULs), can lead to possible nutrient toxicities and adverse health effects

Another source of vitamins

• supplementation of certain vitamins may be needed, for example during certain life stages and for certain population groups

• bacteria in the lower intestinal tract can produce certain vitamins for absorption 

• the body can synthesize certain vitamins 

if an individual is healthy and follows a nutritionally adequate diet..

then it is not necessary to consume 100% of every vitamin each day

What cause nutrient losses?

heat, light, oxygen, passage of time, food processing, food preparation, cooking, and storage

where does vitamin absorption occur?

mainly in the small intestine

mechanical and chemical digestion of vitamins

mechanical- chewing and happens in the mouth

chemical- pancreatic digestive enzymes in the small intestine

absorption of fat-soluble vitamins

• incorporated into micelles

• absorption of fat- soluble vitamins via simple diffusion- unassisted movement across the cell membrane

• once absorbed, they’re incorporated into chylomicrons to transport fats and fat soluble vitamins out of the absorptive cells

• they leave the absorptive cels via lacteals (lymph vessels)

absorption of water-soluble vitamins 

• assitance is needed with absorption to transport proteins (enery may or may not be needed) OR they bind to a specific molecule

• once absorbed into absorptive cells they go directly into bloodstream, most are bound to blood proteins for transport to cells. 

what happens in the large intestine regarding vitamins?

certain vitamins can be made by the bacteria living there

bioavailability

amount of a nutrient that can be effectively digested, absorbed, and used by the body

what is vitamin bioavailability influenced by?

composition of the diet, source of the nutrient, nutrient status, health of the GI tract, and overall health of the body

examples of impaired absorption of vitamins

• diet very low in fat→ impaired fat-soluble vitamin absorption

• low concentration of blood proteins→ impaired water-soluble vitamin absorption

Provitamin or vitamin precursor 

• Vitamins absorbed in an “inactive” form but transform to the vitamins “active” form once inside the body

• this conversion enables the vitamin to fulfill biological functions in the body

vitamins functions generalization

• vitamins regulate a variety of body processes, including those involved in cell division and development as well as growth and maintenance of tissues

• vitamins participate in chemical reactions that release energy from glucose, fatty acids, and certain amino acids

coenzymes

• they are organic compounds that assist enzymes with chemical reactions; they bind to an enzyme to promote the activity of the enzyme which it is bound

• enzymes that require them are “incomplete” (inactive). coenzyme binds with the enzyme to make it active

• ALL B vitamins serve as a coenzyme or are components of coenzymes in metabolic reactions

antioxidant

• a substance that gives up electrons to free radicals to protect cells

• they protect oxidative damage 

oxidative damage

damage caused by highly reactive oxygen molecules that steal electrons

free radical

is a substance with an unpaired electron and it is a highly reactive atom or molecule that causes oxidative damage

What do antioxidants donate and what’s the significance?

they donate electrons, which stabilize the free radical. Thus, making them no longer “reactive” = no longer destructive 

which vitamins are antioxidants?

vitamin E, provitamin A (inactive form), & vitamin C

vitamin needs can be met by…

• meeting calorie needs

• consuming nutrient dense foods

• eating a diet pattern suggested by MyPlate and DGA

tolerable upper intake level (UL)

set at an amount to help avoid the risk for toxicity 

chronic disease risk reduction intake (CDRR)

reducing intake at or below the CDRR is expected to lower chronic disease risk. currently NO CDRRs have been set for any vitamins.

Food labels are regard to list the amount of what vitamin?

vitamin D as a % of the daily value

koagulation (“K”)

means blood clotting 

formation of a blood clot

• vitamin K is needed to make four blood-clotting factors

• K is needed to convert prothrombin to thrombin and thrombin is needed to convert fibrinogen to fibrin.

fibrin

insoluble, fibrous protein that forms the solid clot; traps blood cells and platelets

other functions of vitamin K

• needed for the synthesis of vitamin K-dependent proteins

• the proteins are involved in: formation of bone (enables the minerals to bond) & breakdown of bone, inhibition of blood vessel calcification (help w preventing atherosclerosis), & regulation of cell growth

Relationship between vitamin K and bone formation

• without vitamin K-dependent proteins bone density would be low

• vitamin K may have a role in prevention/treatment of osteoporosis

meeting the AI for vitamin K

• it is used more rapidly in the body than other fat-soluble vitamins, so constant supply is needed

• the body can make it. bacteria (in large intestine) can make about 10% of what is needed

those at risk for a deficiency in vitamin K

• newborns→ do not possess bacteria to make vitamin K because their intestines are sterile, they are given an oral dose of vitamin K at birth

• long term antibiotic usage→ can kill the good bacteria

• taking of anticoagulant meds→ vitamin K interferes with the blood thinner

• disease that impair fat absorption, such as liver diseases & cystic fibrosis, inherited respiratory disease caused by a defective gene that leads to overproduction of thick and sticky mucus

AI for vitamin K

120 micrograms/day for men and 90 micrograms/day for women. no UL for vitamin K

dietary sources for vitamin K

liver, dark green leafy vegetables (spinach, collard greens, kale), broccoli, brussels sprouts, cabbage, kiwi, and canola oil

What are the two classifying forms of vitamin A?

retinoids and carotenoids

Retinoids

• performed (active) vitamin A

• 3 retinoids in the body: retinol, retinal, & retinoic acid

• retinol is stored as retinyl esters

• found naturally in some foods of animal origin

• added to foods via enrichment and fortification

carotenoids

• precursor (provitamin) form of vitamin A

• 600+ forms exist; found naturally in foods of plant origin

• natural pigments made by plants; give certain fruits and vegetables their yellow, orange, or red color

beta carotene 

• it is an example of a carotenoid

• food sources: yellow & orange vegetables & fruits as well as dark green vegetables. also in red veggies and fruits but in lesser amounts

• can be converted into an “active” retinoid, and is the most potent vitamin A precursor (converted to retinoids more efficiently than the other 2 carotenoids) 

what is the function of beta-carotene & other carotenoids that are NOT converted into active vitamin A?

serve as antioxidants, which may have a protective role against cancer and heart disease

food proteins

• vitamin A are bound to these in food

• they are released by the enzymatic actions of pepsin and pancreatic proteases

how is vitamin A absorbed?

by being incorporated into micelles

a diet deficient in fats…

could lead to a deficiency in vitamin A

of the two forms of vitamin A which is more readily absorbed?

retinoids

Retinol activity equivalents (RAE)

some carotenoids are not converted to the active form of vitamin A, so there is less functional vitamin A available. Therefore the recommendations are expressed as RAE

storage of vitamin A

• most of it is stored in the liver

• it is able to leave site by being bound to retinol binding proteins 

• zinc is needed to make these proteins

• a deficiency in protein and zinc could lead to a vitamin A deficiency bc it is unable to leave the liver 

gene expression function of active vitamin A

• role in gene expression: info coded in genes are used to make proteins

• role of vitamin A in gene expression is to regulate the genes involved in protein synthesis

• deficiency in vitamin A hinders protein synthesis

Vitamin A role in cell differentiation

• cell differentiation is a process where immature cells are stimulated to mature. as a result cells have the ability to carry out their specific functions, i.e. they mature into specialized cells

• failure to mature→ cells die and accumulate; tissue is vulnerable to infection

Vitamin A role in processing light

• retina contains the rods and cones, specialized never cells essential for vision

• both need retinol to function properly

• rods convert retinol to retinal that binds to opsin, and forms rhodopsin, a vitamin A containing protein that is needed for vision in dim light.

night blindness

the inability to see clearly in dim light, can occur if retinol is not present in the bloodstream. this condition is an early sign of a vitamin A deficiency 

Vitamin A helps to keep cornea health by…

• the cornea enables light to enter the eye

• a vitamin A deficiency could lead to a condition called xerophthalmia

• there’s an accumulation of keratin in mucus secreting epithelial cells. cells harden and stop producing mucus which is needed to keep the cornea moist and clean

• lack of mucus can cause the cornea to become damaged easily by bacteria and dirt

• as the deficiency progresses with damage there is an increased risk of infection

• if left untreated, can lead to blindness

vitamin A has a key role in the body’s immune system..

by playing a role in the making and activity of white blood cells, some of which produce antibodies

why is vitamin A important for reproduction?

for males it is needed for sperm production. for females, it is needed for normal menstrual cycles, and normal fetal development in pregnant women.

How does vitamin A assist in the growth of bone and teeth?

• remodeling→ dismantling the old bone structure and replacing it with new bone

• the 1st sign of a vitamin A deficiency in children is the failure to grow 

• deficiency in vitamin A also plays a role in tooth decay because the enamel doesn’t develop properly 

how is vitamin D made?

• ultraviolet light (sun) shines on a cholesterol compound in the skin, creating a vitamin D precursor

• 1 and ½ days later the liver and kidneys donate hydroxyl groups and it becomes active vitamin D

what are factors that affect the synthesis of vitamin D?

• color of the skin- darker pigmented skin hinders the making of vitamin D bc UV light is less likely to penetrate into skin

• age: older adults get limited sun exposure and no as efficient at activating vitamin D

• where someone lives: geography and climate affect how often someone gets outside

• time of year: decreased exposure during winter

• concealing clothes worn for religious purpose or cold weather prevents sunlight from striking skin

• use of sunscreen: SPF 15 decreases synthesis by 99%

main function of vitamin D

• regulation of calcium and phosphorus in bones and teeth

• controls the amount of calcium absorbed across the GI tract

• controls the amount that goes in/out of bones

• works w kidneys in regulating amount of calcium secreted in urine

what is the role of the parathyroid hormone (PTH) & increasing blood calcium levels?

• made and secreted from the parathyroid glands

• when blood calcium levels are low it stimulates the release of PTH, which stimulates the activation of vitamin D

• active vitamin D, by itself,  increases the absorption of calcium in the small intestine 

• active vitamin D with PTH increase the breakdown of bone to release Ca and Phosphorus and reduces the excretion of Ca by the kidneys

what happens when there’s a deficiency of vitamin D?

only about 10 to 15% of calcium in the diet is absorbed

rickets

a vitamin D deficiency in children where they’re unable to mineralize newly formed bone. legs become bowed because of not being able to support the body weight.

osteomalacia 

a vitamin D deficiency in adults. it is softening of the bones because of inadequate vitamin D status in adults. the bones contain lower than normal amounts of calcium. muscle weakness is another symptom. 

osteoporosis

chronic disease characterized by bones with low bone mass and reduced structure.

supplements

these are the reason vitamin D is potentially the most toxic of all the vitamins with a UL of 100 micrograms per day

what are early symptoms of toxicity with vitamin D?

pain, chills, loss of appetite, increased urination, and thirst 

continued overdoses

calcium if forced to be deposited in places where it is not normally found such as the heart, lungs, kidneys, and blood vessels. this can cause damage and disrupt normal function. this can have serious health/life consequences. the teeth are affected by toxicity as well→ pulp hardens (nutrients cannot be supplied to the tooth) and the enamel becomes thin.

which vitamins classified as being antioxidants ?

vitamins A, C, and E

Which tocopherol (offspring) compound is the basis for the RDA for vitamin E and why?

alpha- tocopherol because it is the only form that can be used by the body

vitamin E as an antioxidant

• protects the body against oxidative damage

• donates 1 electron to neutralize highly reactive free radicals

• its antioxidant functions can be restored

• vitamin C gives an electron back to vitamin E

what are some molecules and cells that vitamin E helps to protect and how?

• lipids in cell membranes, DNA, proteins, red & white blood cells, nerve cells, & cells of the lungs (exposed to high levels of oxygen)

• helps protect cells from heavy metals (lead and mercury), toxins, and an assortment of drugs

How does vitamin E reduce the risk of developing heart disease and cancer?

• through its role as an antioxidant 

• may help reduce heart disease bc of its anti-inflammatory functions and immune response 

why is a deficiency in vitamin E rare?

because it is found in many foods and the body recycles it

what groups are at risk of deficiency in vitamin E?

• premature infants→ risk of developing hemolytic anemia (insuffiencet # of RBCs bc many may burst) RBCs may burst do to lack of vitamin E, cell membranes are unprotected and break down

• adults with diseases that interfere w absorption of fat

• those who consume too little fat

• those who consume large amounts of processed food

what are premature infants given at birth to prevent RBCs from rupturing?

supplemental vitamin E is given to them

how is vitamin E absorbed and stored?

• absorbed: incorporated into micelles→ absorptive cells

• stored: fatty tissue, liver and muscles

bioavailability of vitamin E (naturally occurring vs supplemental)

• naturally occurring is more readily available

• supplemental vitamin e only provides ½ as much as the vitamin E activity as in the natural form

what concerns are there about taking anticoagulant meds and exceeding the UL for vitamin E?

• the role of these meds is to prevent blood from coagulating (forming a clot)

• vitamin E can intensify the effects. possible result is uncontrollable bleeding