Fat soluble vitamins

FACS 113

Susan Algert

Fat Soluble Vitamins

• Dissolve in organic solvents

• Not readily excreted and can cause toxicity

• Fat malabsorption can cause deficiency

• Transported like fat in chylomicrons, VLDL, LDL and other protein carriers

Vitamins

• Essential organic substances

• Yield no energy, but facilitate energy yielding reactions

• Will produce deficiency signs and symptoms if absent from the diet

• Fat soluble and water soluble

Forms of Vitamin A

• Preformed are retinyl esters

retinoids (retinal retinol, retinoic acid)

found in animal products

Provitamin A

• Carotenoids (beta carotene, alpha carotene, lutein, lycopene, zeaxanthin)

• Must be converted to retinoid form

• Found in plant products

• Most biologically active provitamin is beta carotene

Transport and Storage

• Liver stores 90% of vitamin A in the body• Reserve is adequate for several months• Transported from the liver as retinol via

retinol binding protein to target tissue• Caroteinoids can be transported via CM and

VLDL• Target cells contain intracellular retinol

binding proteins

Vitamin A roles in the body

• Promotes vision (retinol)

• Supports protein synthesis and cell differentiation (retinoic acid)

• Night and color vision (retinal)

Cartenoids roles in the body

• Antioxidant

• Vision

• Cancer

• Heart disease

The visual cycle

• Cones in the retina

Are responsible for vision under bright light

Translate objects to color vision

• Rods in the retina

responsible for vision in dim light

translate objects in black and white vision

Cell health and maintenance

• Retinoic acid influences how the epithelial cells differentiate and mature

• Without vitamin A cells will not differentiate

• Leads to follicular hyperkeratosis

Growth and development

• Retinoic acid is necessary for cellular differentiation

• Retinoic acid triggers specific nuclear receptors in the DNA for differentiation

• Important

Food Sources

• Preformed

• Liver, fish oils, fortified milk, eggs

• half of vitamin A intake

• Proformed

• Dark leafy green, yellow, orange veggies; also half of vitamin A intake

Retinol Activity Equivalents

• 1 RAE =

• 1 ug retinol

• 12 ug beta corotene

• 24 ug of other vitamin A

• Precursor carotenoids

IU of vitamin A

• 0.3 ug retinol

• 3.6 ug beta carotene

• 7.2 ug of other vitamin A precursors

RDA for vitamin A

• 1000 RE for men

• 800 RE for women

• Average intake meets RDA

• No separate RDA for caroteniods

Vitamin A deficiency

• Less than 500 ugms per day

• Growth failure

• Infectious disease (diarrhea, measels)

• Night blindness

• Xeropthalmia

• keratinization

Toxicity

• Results from long term supplement use (3-10 X RDA or 15,000 ug RE)

• Large intake of vitamin A over long period of time• bone./muscle pain, loss of appetite, skin disorders,

headache, dry skin, hair loss• Discontinue supplementation, possible permanent

damage• Hypercarotenemia from caroteinoids

Vitamin D

• Prohormone• Derived from cholesterol• Synthesis from sun exposure• Insufficient sun exposure makes this an

essential nutrient• Activated by enzymes in the liver• Deficiency can cause disease; rickets or

osteomalacia

Functions of Vitamin D

• Calcitrol influences differentiation of cells

• Increased protein synthesis

• Stimulates calcium binding protein in the intestine

• Enhances calcium absorption in the intestine

Vitamin D role in bone formation

• Decreases calcium excretion in the kidney

• Causes Ca and Phos to deposit in the bones

• Strengthens bones

• Mobilizes calcium from bones depending on blood calcium level

Food sources

• Fatty fish such as salmon and herring

• Fortified milk

• Other fortified foods

Adequate intake of vitamin D

• 5 ug/day (200 IU) for adults

• 10-15 ug/day (400-500 IU) for over age 51

• Casual sun exposure usually produces enough vitamin D

• Infants are born with sufficient D to last 9 months

Toxicity of vitamin D

• Regular intake of 5-10 x the AI can be toxic

• Results from excessive supplementation and not from sun exposure or milk consumption

• Overabsorption of calcium (hypercalcemia) and increased calcium excretion

Vitamin E

• Tocopherols and tocotrienols

• Tansported via chylomicrons

• Found concentrated in areas where fat is found

Antioxidant or redux agent

• Vitamin E is able to donate electron to oxidizing agent

• Protects the cells from attack by free radicals

production is normal result of cell metabolism

destructive to cell membrane

Functions of vitamin E

• Protects the double bonds in fat

• Role in iron metabolism

• Maintenance of nervous tissue and immune function

Food sources of vitamin E

• Plant oils and margarines

• Wheat germ

• Asparagus

• Dark green leafy vegetables

• Nuts and seeds

RDA for vitamin E

• 8 mg/day for women

• 10 mg/day for men

• Average intake meets RDA

• 1 mg vitamin E = 1.5 IU (from food source) = 1.0 IU (from synthetic source)

Deficiency

• Red blood cell fragility

• Neurological disorders affecting the spinal cord

• Anti aging vitamin?

Toxicity of vitamin E

• Supplements up to 800 IU is probably harmless

• TUL is 1 gm/day

• Inhibits vitamin K metabolism and anticoagulants

Vitamin K

• Phylloquinones and menaquinones are active forms

• Role in the coagulation process

• Calcium binding potential

• Formation of osteocalcin

ood sources of vitamin K

• Liver

• Green leafy vegetables

• Broccoli

• Peas

• Green beans

• Resistant to cooking losses

• Limited vitamin K stores in the body

Drug Interactions

• Anticoagluant

Lessen blood clotting process

Need to monitor vitamin K intake

• Antibiotics

destroy intestinal bacteria

inhibits vitamin K synthesis and absorption

potential for excessive bleeding

RDA for vitamin K

• 60-65 mg/day for women

• 65-80 mg/day for men

• RDA is met by most people

• Excess vitamin A and E interfere with K

• Newborns are injected with vitamin K

• Toxicity unlikely; readily excreted

• Deficiency leads to bleeding/ hemmorhage