fat-soluble vitamins

CHAPTER 12

FAT-SOLUBLE VITAMINS

LEARNING OUTCOMES

• Define the word vitamin and list 3 characteristics of vitamins as a group• Classify the vitamins according to whether they

are fat or water-soluble• List 3 important food sources for each fat- soluble

vitamin• List the major functions for each fat-soluble

vitamin

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LEARNING OUTCOMES

• Describe the deficiency symptoms for each fat-soluble vitamin and state the conditions in which deficiencies are likely to occur• Describe the toxicity symptoms caused by

excess consumption of certain fat-soluble vitamins• Evaluate the use of vitamin and mineral

supplements with respect to their potential benefits and risks to health

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VITAMINS: ESSENTIAL DIETARY COMPONENTS

• Two categories• Fat-soluble: Vitamins A, D, E and K• Water-soluble: Vitamin B complex (8) and C

• Compare and Contrast• Absorption of vitamins • Malabsorption of vitamins• Transport of vitamins• Storage of vitamins in the body

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VITAMIN A

• Retinoids• Active form:

preformed Vitamin A• Retinal, retinol and

retinoic acid• Dietary sources:

liver, fish oils, fortified dairy products and eggs

• Caroteinoids• Provitamins-can be

converted to Vitamin A• Dietary sources:

dark green and yellow orange vegetables and fruits

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EQUIVALENTS

• Used for some vitamins when there are multiple forms of the vitamin so there is one common unit

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VITAMIN A NEEDS

• RDA• Men• 900 micrograms retinol activity equivalent (RAE)

• Women• 700 micrograms RAE

• Daily Value (used on packaging)• Approximately 1,000 micrograms

• Average current intake meets DRI

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Which are vitamin A and which are beta

carotene?

ABSORPTION, TRANSPORT AND EXCRETION OF VITAMIN A

• Absorption• Packaged with chylomicrons and transported via the

lymphatic system

• Transport• Retinoids-bound to retinol binding protein• Carotenoids-carried by VLDL

• Excretion• Small amount in urine

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FUNCTIONS OF VITAMIN A (RETINOIDS)

• Growth and Development• Embryonic development• Epithelial cells and mucus production in lungs, trachea,

skin, GI tract

• Immune Function• Maintains the ephithelium• Increased infections w/vit A deficiency

• Dermatology• Topical and oral medications

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FUNCTIONS OF VITAMIN A (RETINOIDS)

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FUNCTIONS OF VITAMIN A (RETINOIDS)

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FUNCTIONS OF CAROTENOIDS

• Provitamin A activity • Beta carotene (most Vitamin A activity of the

carotenoids)• NOT toxic

• Other health benefits• Cataracts• Lung cancer• Macular degeneration

• Other carotenoids• Lutein and zeaxanthin• Lycopene

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VITAMIN A DISEASES

• Deficiencies• Night blindness• Xerophthalmia (permanent blindness)• Follicular hyperkeratosis• Impaired growth• Increased infections• Increased transmission of maternal/fetal HIV

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VITAMIN A DISEASES

• Toxicities• Hypervitaminosis A• Upper limit-3000 micrograms/day retinol (not

carotenoids)• Appears w/ chronic supplement use at 5-10x the RDA• Acute (100x RDA for a few days)• GI upset, headache, poor muscle coordination

• Chronic (chronic use of 10x RDA)• Joint pain, liver damage, coma, death

• Teratogenic

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VITAMIN D

• “Conditional” or prohormone• Requirement-sunlight 2-3 times a week for 10-15

minutes• Skin formation:• In skin, sunlight (UV light) changes 7-dehydrocholesterol

(made from cholesterol) to vitamin D3• Whether it is made in the skin or ingested, D3 is

converted to form 25-hydroxycholecalciferol or 25(OH)D) in the liver. Once made, the product is released into the plasma, where it binds to vitamin D binding protein.

• 25(OH)D travels to liver and kidney and converted to bio active form-1,25(OH)2D (ligand for VDR, responsible for most actions of vitamin D)

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Table 2: Recommended Dietary Allowances (RDAs) for Vitamin D [1]

Age Male Female Pregnancy Lactation

0–12 months*

400 IU(10 mcg)

400 IU(10 mcg)

1–13 years 600 IU(15 mcg)

600 IU(15 mcg)

14–18 years 600 IU(15 mcg)

600 IU(15 mcg)

600 IU(15 mcg)

600 IU(15 mcg)

19–50 years 600 IU(15 mcg)

600 IU(15 mcg)

600 IU(15 mcg)

600 IU(15 mcg)

51–70 years 600 IU(15 mcg)

600 IU(15 mcg)

>70 years 800 IU(20 mcg)

800 IU(20 mcg)

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VITAMIN D NEEDS

• The new reference intakes (RDA) for vitamin D are based on amount need to maintain serum 25-hydroxyvitamin D level of 20 ng/mL (for optimal bone and overall health):• 1–70 years of age: 600 IU/day (15 μg equivalent)• 71+ years of age: 800 IU/day

• Recommendations assumes no skin synthesis of vitamin D and refers to total intake from food, beverages and supplements.

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ABSORPTION, TRANSPORT AND EXCRETION OF VITAMIN D

• Absorption and Transportation• Absorbed via micelles and transported

via chylomicrons in the lymphatic system• Bound to a protein• Synthesis of the active form is regulated

by parathyroid hormone and kidneys

• Excretion• Small amount in urine and bile

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FUNCTIONS OF VITAMIN D

• Calcium and Phosphorus Homeostasis• Aid in increasing absorption of calcium• Aid in releasing calcium from bone, if

necessary

• Bone Health• Immune Function (cold and flu)• Cancer (breast, colon, prostrate)• Heart disease• Type 1 diabetes

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VITAMIN D DISEASES

•Deficiencies• Children-rickets• Adults-osteomalacia• Toxicities• Does not occur from sunlight or

dietary sources• Does occur with supplementation• Upper limit• 4000 IU daily

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VITAMIN E

•8 compounds• 4 tocopherols• 4 tocotrienols

•Dietary sources:• Plant oils, wheat germ, asparagus, almonds, peanuts and sunflower seeds

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VITAMIN E NEEDS

•RDA• 15 mg daily of alpha-tocopherol

•Daily Value• 30 IU (approximately 20 mg)

•Adults consume approximately 2/3 the RDA

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ABSORPTION, TRANSPORT AND EXCRETION OF VITAMIN E

• Absorption and Transportation• Micelles into chylomicrons• Transported via lipoproteins• Stored in adipose tissue

• Excretion• Bile, urine and skin

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VITAMIN E FUNCTIONS

• Antioxidant• Reduces oxidative stress•Other antioxidant compounds• Glutathione peroxidase• Selenium

• Superoxide dismutase• Copper, Zinc and Manganese

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VITAMIN E DISEASES

•Deficiencies• Hemolytic anemia-rare in humans

• Toxicities• Interfere with Vitamin K and cause

hemorrhaging• Upper limit: • 1000 mg natural sources• 1100 IU synthetic sources

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VITAMIN K

•Menaquinones• Synthesized by gut bacteria• Fish oils and meats•Phylloquinones• Plants: green leafy vegetables, broccoli, peas and green beans•Most biologically active

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VITAMIN K NEEDS

•AI•Women• 90 micrograms daily

•Men• 120 micrograms daily

•Daily Value• 80 micrograms

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ABSORPTION, TRANSPORT AND EXCRETION OF VITAMIN K

• Absorption and Transportation• Absorbed in small intestine, via

chylomicrons in lymphatic system.• Transported via lipoproteins and stored

in the liver

• Excretion• Primarily bile, small amount urine

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VITAMIN K

• Functions• Blood clotting factors• Bone health• May protect the body from inflammation

• Deficiency• Rare: long term antibiotic use or fat

malabsorption

• Toxicity• No UL

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DIETARY SUPPLEMENTS

•Dietary Supplement Health and Education Act of 1994 (DSHEA)• A mineral• A vitamin• An amino acid• A herb, a botanical, or a plant extract• A combination of any of the above

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VITAMIN/MINERAL SUPPLEMENTATION

• Individuals that may benefit• Things to look for:• No more than 100% Daily Value• USP certification• Diet and supplement shouldn’t exceed ULs• Check for superfluous ingredients

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