Fat-Soluble Vitamins Update (PDF)

The Fat-Soluble Vitamins A, D, E, and K 1  Vitamins: essential nutrients needed in tiny amounts in the diet to prevent deficiency diseases and to support health. Bioavailability is the rate and extent that a nutrient is absorbed and used. Precursors, also known as provitamin...

The Fat-Soluble Vitamins A, D, E, and K 1  Vitamins: essential nutrients needed in tiny amounts in the diet to prevent deficiency diseases and to support health. Bioavailability is the rate and extent that a nutrient is absorbed and used. 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. Solubility and Storage Toxicity 3  Vitamin A Vitamin A is found in the body in compounds known as retinoids: retinol, retinal, and retinoic acid. Functional roles: – Promoting Vision 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 that bonded to retinal. 4  – Protein Synthesis and Cell Differentiation Epithelial tissues on the outside (skin) and inside (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 5  Vitamin A Deficiency Vitamin A – Infectious Diseases Impaired immunity correlates with Vitamin A deficiency in children. – Night Blindness First detectable sign of Vitamin A deficiency Inability to see in dim light Blindness – Xerophthalmia is blindness due to Vitamin A deficiency. – Keratinization Epithelial cells secrete a protein called keratin (hard, inflexible protein of hair and nails). Rough, dry and scaly skin is called keratinization. 6  Vitamin A Vitamin A Toxicity can occur with concentrated amounts of Vitamin A from foods, fortified foods, or supplements – Bone Defects – Birth Defects – Chronic toxicity symptoms are liver abnormalities – Acute toxicity symptoms include blurred vision, nausea, vomiting, vertigo, headaches, and pressure in the skull. 7  Vitamin A Vitamin A Recommendations Expressed as retinal activity equivalents (RAE) based on preformed retinol and beta-carotene in food. RDA Men: 900g RAE/day RDA Women: 700g RAE/day Food Sources: Beef liver, sweet potatoes, carrots. 8 9  Vitamin D Other names – Calciferol – 1,25-dihyroxy vitamin D (calcitriol) Animal version: vitamin D3 or cholecalciferol Plant version: vitamin D2 or ergocalciferol Precursor : cholesterol 10 11  Vitamin D Chief functions Maintain blood concentrations of calcium and phosphorus by: 1- enhance their reabsorption from digestive tract 2- enhance their mobilization from bones 3- stimulating their retention by kidneys) 12  Vitamin D Deficiency – Factors that contribute to deficiency » Dark skin » Breastfeeding without supplementation » Lack of sunlight » Use of nonfortified milk 13  Vitamin D Deficiency diseases – Rickets – Osteomalacia 14  Vitamin D Deficiency symptoms: rickets in children 1- Inadequate calcification, resulting in bowing of legs 2- Enlargement of ends of long bones 3- Deformities of ribs (bowed, with beads or knobs) 15  Vitamin D 4- Delayed closing of fontanel, resulting in rapid enlargement of head 16  Vitamin D Deficiency symptoms:osteomalacia in adults – Loss of calcium, resulting in soft, flexible, brittle, and deformed bones. – Progressive weakness – Pain in pelvis, lower back, and legs 17  Vitamin D Toxicity disease: hypervitaminosis D Toxicity symptoms – Elevated blood calcium – Calcification of soft tissues (blood vessels, kidneys, heart, lungs, tissues around joints 18  Vitamin D adequate intake (AI) – 19-50 years: 5 g/day – 51-70 years: 10 g/day – more than 70 years: 15 g/day 19  Vitamin D Significant sources – Synthesized in the body with the help of sunlight – Fortified milk, margarine, butter, cereals, and chocolate mixes – beef, egg yolks, liver, fatty fish (salmon, sardines) and their oils 20  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 21  Vitamin E Vitamin E Deficiency Primary deficiency is rare Erythrocyte hemolysis – Occurs in premature infants – Hemolytic anemia can be treated with Vitamin E treatment Symptoms – Loss of muscle coordination and reflexes – Impaired vision and speech – Nerve damage Vitamin E Toxicity Rare and the least toxic of the fat-soluble vitamins Upper level for adults: 1000 mg/day 22 May enhance the effects of anti-clotting medication  Vitamin E 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 23  Vitamin K Chief functions in the body – Synthesis of blood-clotting proteins and bone proteins that regulate blood calcium 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 24  Vitamin K Vitamin K Recommendations 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 25