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Understanding Fat-Soluble Vitamins A, D, E, and K

Learn about the structure, function, and food sources of fat-soluble vitamins A, D, E, and K. Explore the factors affecting bioavailability, toxicity risks, deficiency symptoms, and recommended daily intakes. Discover the vital roles these vitamins play in your health.

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Understanding Fat-Soluble Vitamins A, D, E, and K

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  1. The Fat-Soluble Vitamins A, D, E, and K

  2. The Vitamins • Vitamins differ from carbohydrate, fat and protein in structure, function and food contents. Vitamins are similar to the energy-yielding nutrients in that they are vital to life, organic and available from foods. • Bioavailability is the rate and extent that a nutrient is absorbed and used.

  3. The Vitamins–An Overview (cont’d.) • Factors affecting the bioavailability of a vitamin • Digestion efficiency and GI tract transit time • Previous nutrient intake and nutrition status • Other foods consumed at the same time • Method of food preparation • Nutrient source

  4. Precursors, also known as provitamins, are consumed in an inactive form and become active vitamins in the body. • The organic nature of vitamins means they can be destroyed in cooking and storage. There are methods used to minimize nutrient losses. Refrigerate fruits and vegetables. • Solubility and Storage • Toxicity • Requirements

  5. Vitamin A • Vitamin A is found in the body in compounds known as retinoids: retinol, retinal, and retinoic acid. • Functional roles: • Promoting Vision • Helps to maintain the cornea • Conversion of light energy into nerve impulses at the retina • Rhodopsin is a light-sensitive pigment of the retina that contains opsin. • Protein Synthesis and Cell Differentiation • Epithelial cells • Epithelial tissue on the outside is skin. • Epithelial tissues on the inside are mucous membranes. • Reproduction and Growth • Sperm development in men • Normal fetal development in women • Growth in children • Bone growth called remodeling • Beta-carotene as an antioxidant

  6. Vitamin A • Vitamin A Deficiency • Infectious Diseases • Impaired immunity correlates with Vitamin A deficiency in children. • The goals of worldwide health organizations include Vitamin A supplementation. • Night Blindness • First detectable sign of Vitamin A deficiency • Inability to see in dim light • Blindness • Xerosis is the first stage where the cornea becomes dry and hard. • Keratomalacia is the softening of the cornea. • Xerophthalmia is blindness due to Vitamin A deficiency.

  7. Vitamin A

  8. Keratinization • Epithelial cells secrete a protein called keratin—the hard, inflexible protein of hair and nails. • Rough, dry and scaly skin is called keratinization. • Deficiency disease is called hypovitaminosis A

  9. Vitamin A • Vitamin A Toxicity can occur with concentrated amounts of the preformed Vitamin A from foods, fortified foods, or supplements • Bone Defects • Birth Defects • Toxicity disease is called hypervutanubisus A • Chronic toxicity symptoms are liver abnormalities • Acute toxicity symptoms include blurred vision, nausea, vomiting, vertigo, headaches, and pressure in the skull.

  10. Vitamin A • Vitamin A Recommendations (2001 RDA) • Expressed as retinal activity equivalents (RAE) because of preformed retinol and beta-carotene • RDA Men: 900g RAE/day • RDA Women: 700g RAE/day • Upper level for adults: 3000 g/day • Food Sources

  11. Vitamin D • Other names • Calciferol • 1,25-dihyroxy vitamin D (calcitriol) • Animal version: vitamin D3 or cholecalciferol • Plant version: vitamin D2 or ergocalciferol • Precursor is the body’s own cholesterol

  12. Vitamin D • 1997 adequate intake (AI) • 19-50 years: 5 g/day • 51-70 years: 10 g/day • more than 70 years: 15 g/day • Upper level for adults: 50 g/day

  13. Vitamin D • Chief functions in the body • Mineralization of bones (raises blood calcium and phosphorus by increasing absorption from digestive tract, withdrawing calcium from bones, stimulating retention by kidneys)

  14. Vitamin D • Significant sources • Synthesized in the body with the help of sunlight • Fortified milk, margarine, butter, cereals, and chocolate mixes • Veal, beef, egg yolks, liver, fatty fish (herring, salmon, sardines) and their oils

  15. Vitamin D • Deficiency • Factors that contribute to deficiency • Dark skin • Breastfeeding without supplementation • Lack of sunlight • Use of nonfortified milk

  16. Vitamin D • Deficiency diseases • Rickets • Osteomalacia

  17. Vitamin D • Deficiency symptoms: rickets in children • Inadequate calcification, resulting in misshapen bones (bowing of legs) • Enlargement of ends of long bones (knees, wrists) • Deformities of ribs (bowed, with beads or knobs)

  18. Vitamin D • Deficiency symptoms: rickets in children (continued) • Delayed closing of fontanel, resulting in rapid enlargement of head

  19. Vitamin D • Deficiency symptoms: rickets in children (continued) • Lax muscles resulting in protrusion of abdomen • Muscle spasms • Deficiency symptoms: osteomalacia in adults • Loss of calcium, resulting in soft, flexible, brittle, and deformed bones

  20. Vitamin D • Deficiency symptoms: osteomalacia in adults (cont.) • Progressive weakness • Pain in pelvis, lower back, and legs • Toxicity disease: hypervitaminosis D

  21. Vitamin D • Toxicity symptoms • Elevated blood calcium • Calcification of soft tissues (blood vessels, kidneys, heart, lungs, tissues around joints) • Frequent urination

  22. Vitamin E • There are four different tocopherol compounds, but only the alpha-tocopherol has Vitamin E activity in human beings. • Chief function in the body • Vitamin E as an Antioxidant • Stops the chain reaction of free radicals • Protects the oxidation of LDLs • Protection of polyunsaturated fatty acids and Vitamin A

  23. Vitamin E • Vitamin E Deficiency • Primary deficiency is rare • Erythrocyte hemolysis • Occursin premature infants • Hemolytic anemia can be treated with Vitamin E treatment • Symptoms • Loss of muscle coordination and reflexes • Impaired vision and speech • Nerve damage

  24. Vitamin E Toxicity • Rare and the least toxic of the fat-soluble vitamins • Upper level for adults: 1000 mg/day • May augment the effects of anti-clotting medication

  25. Vitamin E • 2000 RDA • Adults: 15 mg/day • Upper level for adults: 1000 mg/day • Significant sources • Polyunsaturated plant oils (margarine, salad dressings, shortenings) • Leafy green vegetables, wheat germ, whole grains, liver, egg yolks, nuts, seeds • Easily destroyed by heat and oxygen

  26. Vitamin E

  27. Vitamin K • Other names • Phylloquinone • Manaquinone • Menadione • Naphthoquinone • Chief functions in the body • Synthesis of blood-clotting proteins and bone proteins that regulate blood calcium

  28. Vitamin K • Vitamin K Deficiency • Symptoms include hemorrhaging • Hemorrhagic Disease • Secondary deficiencies may occur with use of antibiotics. • Newborn infants receive a single dose of Vitamin K at birth because of a sterile intestinal tract. • Vitamin K Toxicity • Uncommon • No known toxicities

  29. Vitamin K • Vitamin K Recommendations (2001 AI) • AI Men: 120 g/day • AI Women: 90 g/day • Vitamin K Sources • Bacterial synthesis in the digestive tract • Significant Food Sources • Liver • Leafy green vegetables and cabbage-type vegetables • Milk

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