Fat-Soluble Vitamins Overview

Fat-Soluble Vitamins

• Vitamins A, D, E, and K are fat-soluble
• Vitamins are essential nutrients needed in small amounts for health and to prevent deficiency diseases.
• Bioavailability is the rate and extent a nutrient is absorbed and used.
• Precursors (provitamins) are inactive forms that become active vitamins in the body.
• Vitamins are organic, meaning they can be destroyed by cooking and storage.
• Fat-soluble vitamins are absorbed into the lymphatic system, then the bloodstream, requiring protein carriers to transport them.
• They're stored in fat-soluble cells, making them less readily excreted and potentially toxic.
• Often needed in periodic doses (weeks or even months)
• This differs from water-soluble vitamins, which are absorbed directly into the blood, travel freely, and are readily excreted.

Vitamin A

• Retinoids include retinol, retinal, and retinoic acid.
• Beta-carotene is a precursor of vitamin A
• Retinol is important for reproduction.
• Retinal helps with vision.
• Retinoic acid has roles in growth.
• Vitamin A promotes vision, maintaining the cornea, and converts energy to nerve impulses by rhodopsin.

Vitamin A Functions

• Protein synthesis and cell differentiation, crucial for epithelial tissues (skin and mucous membranes).
• Essential for sperm development in men and normal fetal development in women.
• Critical for growth in children, and bone remodeling.
• Beta-carotene is also an antioxidant.

Vitamin A Deficiency

• Impaired immunity in children is correlated with vitamin A deficiency.
• Night blindness is an initial indicator of deficiency.
• Xerophthalmia is a type of blindness resulting from the deficiency.
• Keratinization, where epithelial cells secrete keratin, causes rough, dry, scaly skin.

Vitamin A Toxicity

• Can occur with large amounts from fortified foods, supplements or concentrated food sources
• Symptoms include bone defects, birth defects and abnormal liver function.
• Acute toxicity symptoms can include blurred vision, nausea, vomiting, vertigo, headaches, and pressure in the skull.

Vitamin A Recommendations

• Measured in retinal activity equivalents (RAE).
• RDA (Recommended Dietary Allowances) for men is 900 µg RAE/day, for women 700 µg RAE/day.

Vitamin D

• Other names include Calciferol, 1,25-dihydroxy vitamin D (calcitriol)
• Animal form is vitamin D3 (cholecalciferol)
• Plant form is vitamin D2 (ergocalciferol)
• Precursor is cholesterol
• Made in the body with the help of sunlight
• Active form of vitamin D is made by the liver and kidneys from a precursor in the skin, 7-dehydrocholesterol
• Critical for calcium and phosphorus absorption.

Vitamin D Functions

• Maintains blood concentrations of calcium and phosphorus by enhancing their absorption from the digestive tract, mobilization from bones, and kidneys retention.

Vitamin D Deficiency

• Factors that contribute include dark skin, exclusive breastfeeding without supplementation, lack of sunlight, and use of nonfortified milk.
• Symptoms in children lead to rickets: Bowed legs, an enlarged cranium, thickened wrists and ankles, and delayed fontanelle closure.
• Symptoms in adults: osteomalacia, loss of calcium, resulting in soft, brittle, deformed bones; progressive weakness; pain in the pelvis, lower back, and legs.

Vitamin D Toxicity

• Hypervitaminosis D
• Symptoms include elevated blood calcium and calcification of soft tissues (blood vessels, kidneys, heart, lungs, tissues around joints).

Vitamin D Adequate Intake

• AI for 19-50-year-olds is 5 µg/day
• AI for 51-70-year-olds is 10 µg/day
• AI for those over 70 is 15 µg/day

Vitamin D Significant Sources

• Synthesized in the body with sunlight.
• Fortified milk, margarine, butter, cereals, and chocolate mixes.
• Beef, egg yolks, liver, fatty fish (salmon, sardines), and their oils.

Vitamin E

• Only alpha-tocopherol has vitamin E activity.
• Chief function is an antioxidant.
• Stops free radical chain reaction.
• Protects oxidation of LDLs (low-density lipoproteins) and vitamin A.

Vitamin E Deficiency

• Rare primary deficiency.
• Observed in premature infants.
• Hemolytic anemia can be treated with vitamin E.
• Symptoms include muscle coordination and reflex loss; impaired vision and speech; nerve damage.

Vitamin E Recommendations

• RDA for adults is 15 mg/day.
• Upper level for adults is 1000 mg/day.

Vitamin E Significant Sources

• Polyunsaturated plant oils (margarine, salad dressings).
• Leafy green vegetables, wheat germ, whole grains, liver, egg yolks, nuts, and seeds.
• Easily destroyed by heat and oxygen.

Vitamin K

• Chief functions include synthesis of blood-clotting proteins and bone proteins that regulate calcium.
• Deficiency can cause hemorrhage.
• Newborn infants often receive a single dose at birth for a sterile intestinal tract due to bacterial deficiency risk.
• Secondary deficiencies can result from antibiotic use.

Vitamin K Recommendations

• AL (Adequate Level) for men is 120 mcg/day.
• AL for women is 90 mcg/day.

Vitamin K Sources

• Bacterial synthesis in the digestive tract
• Liver, leafy green vegetables, cabbage type vegetables, and milk.

This quiz covers essential information about fat-soluble vitamins A, D, E, and K. Learn about their functions, absorption, storage, and the importance of precursors in human health. Test your understanding of these vital nutrients and their roles in preventing deficiency diseases.