Part I: in shortVitamin D, as we are learning, is not a true vitamin. Ideally, we synthesize our own from natural sunlight, but that is not possible or practical for most of us these days. It seems that almost everyone who has their blood tested latelyis diagnosed with a Vitamin D deficiency, and they often receive a prescription for a high dose supplement. It is a little known fact, though it is briefly introduced in Lecture 6,that Vitamin D works best with the form of Vitamin K (menaquinone or K2) that we synthesize if our gut bacteria is in balance. K2 is also present in a very few foods and as a supplement. Choose either Vitamin D or K2 to kick-off your main post. Discuss risks/benefits of supplementation and deficiency issues. If you choose K2, you might want to mention how it differs from K1 (phylloquinone),but keep the focus on K2 Although you are choosing only one of the two vitamins to focus on first, it is appropriate to mention how your vitamin of choice interacts with the other.Part II:reply to the following posts(about 50 words each)
I'll post it once you finish part I.
Bio 125 Spring 2016 Lecture 6 Janine Grant FAT SOLUBLE VITAMINS 1 Bio 125 Distance Learning Lecture 6Janine Grant Fat Soluble Vitamins Learning Objectives: Distinguish between the 4 fat (lipid) soluble vitamins (A, D, E, K) Understand the how they are different from the water soluble vitamins. Review absorption of fat soluble nutrients. Important basic functions for each of the 4 vitamins. Deficiency and toxicity symptoms. 2 VITAMIN A Vitamin A is family of related compounds referred to as retinoids. They are named after one of vitamin A’s functions, which occurs in the eye. 90% of the body’s vitamin A is found in the liver. The biologically active forms of vitamin A known as retinoids include retinol (alcohol), retinal (aldehyde), and retinoic acid. Retinol can be converted in the body to retinal. Retinal can be converted to retinoic acid. The retinoids are found only in animal products. Retinol and retinoic acid function as hormones. Retinal functions in the visual cycle. The carotenoids, on the other hand, are found in fruits and vegetables. Beta carotene is thought to be the most active as vitamin A precursor. Provitamin A, or carotenoids, are converted into Vitamin A - - retinal and retinol, in the intestine when there is a need. Carotenoids that are not converted to Vitamin A have antioxidant activity on their own in the body. 3 Absorption and Metabolism Vitamin A is absorbed along with dietary fat via micelles. Preformed vitamin A, found in animal foods occurs as retinol (the alcohol form), and as retinyl esters (retinol bound to a fatty acid). Vitamin A and carotenoids combine with bile acids and are absorbed along with dietary fat and transported to the liver as chylomicrons. From the liver, stored retinol is transported, bound to a protein. in the blood to target tissues as needed. In the body, retinol can be converted to retinal (reversible) and retinoic acid (non-reversible). Dietary beta-carotene and the many other carotenoids, found in plants, are the original sources of vitamin A. A molecule of beta-carotene can be split in two to form two molecules of vitamin A. However, this conversion does not occur efficiently with food sources of carotenoids so overdose won’t occur. About 70 – 90% of preformed vitamin A (retinoids) is absorbed. Carotenoids are absorbed less efficiently. The % of absorption decreases as dietary intake increases. Dietary fat enhances the absorption of carotenoids. Functions of Retinoids Visual Cycle - Night vision, and color vision; requires retinal, the aldehyde form of vitamin A Gene expression and cell differentiation require retinoic acid. Retinoic acid is involved in protein synthesis and the differentiation of bone cells and tooth enamel. Epithelial tissue (skin, mucous membranes, linings of body cavities) require retinoic acid for normal growth and differentiation The mucous secreting cells of the eyes are particularly vulnerable to deficiency of vitamin A. These cells replace themselves continuously and without vitamin A, they do not differentiate and instead become cells that produce keratin, the hard protein found in hair and nails. The deficiency disease known as xeropthalmia results. Immune system - requires retinioic acid: For maintaining integrity of the mucous membranes. The differentiation of different types of immune cells. Reproduction Retinol is involved in the synthesis of steroid hormones. Retinoic acid is involved with differentiation of cells during embryonic development. 4 5 Carotenoids: In addition to being precursors to Vitamin A, can also function as lipid soluble antioxidants. RDAs for Adults Males: 900 micrograms (900 Retinol Equivalents) or 2,970 International Units) Females: 700 micrograms (700 Retinol Equivalents) or 2,333 IU UL for adults – 3,000 micrograms Optional Info: Retinol Activity Equivalencies (RAE) For Beta-carotene: 2 micrograms supplemental beta-carotene = 1 RE or 1 microgram 12 micrograms beta carotene from food = 1 RE or 1 microgram 6 Deficiency Occurs with chronic deficiency, up to a year’s supply of vitamin A can be stored in the liver. Zinc is needed for mobilization of Vitamin A from the liver. Cessation of bone growth, bone and tooth malformations Anemia Eyes Night blindness is one of the first signs of deficiency. Hyperkeratination of tissue in the eyes Xerosis (dry eyes) followed by Bitot’s spots on the eye Irreversible blindness caused by severe drying and degeneration of the cornea (xerophthalmia) Lowered immunity (see functions above) Skin Hyperkeratosis – plugging of hair follicle Also, changes in linings of digestive and urogenital tract (because those cells replace themselves often), infections due to deficiency in mucous. 7 Xerophthalmia: Long term Vitamin A Deficiency 8 Toxicity Hypervitaminosis A: Serious. Symptoms of acute toxicity include headaches, dry skin and hair, nausea/vomiting/diarrhea, blurred vision. Symptoms of chronic toxicity (intakes of 10 times the RDA) include weight loss, muscle and joint pain, liver damage, bone abnormalities, visual defects, skin and mucous membrane abnormalities. High intakes of preformed vitamin A) (retinoids) are linked to osteoporosis. Hypervitaminosis A during pregnancy causes birth defects. Hypercarotenemia – from high intakes of carotenoids: Harmless. Carotenoids (composed of 2 molecules of Vitamin A, are less efficiently absorbed, especially at high intakes, than the retinoids, and are antioxidants. Good Food Sources Vitamin A: Eggs, liver, full fat milk, butter Beta carotene and other carotenoids: Plant foods 9 VITAMIN D It is different from the other vitamins in that the body can synthesize it from sunlight from cholesterol in the skin. It becomes essential when exposure to sunlight is limited, or synthesis is reduced. It more like a hormone than a vitamin. It attained vitamin status when it was discovered that rickets and osteomalacia could be prevented by adequate Vitamin D intake. Absorption and Metabolism Self-synthesis A derivative of cholesterol found in the skin) is exposed to UV light and transformed to cholecalciferol, a precursor to Vitamin D, or prohormone also known as vitamin D3. Dietary vitamin D3 is absorbed along with dietary fat. From animal sources (cholecalciferol) or D3 Plant derived (ergocalciferol) or D2 is not an appropriate source of vitamin D, and should not be taken as supplement. Vitamin D3 (cholecalciferol) from self synthesis and from diet combine and travels to the liver, where it is converted to 25-hydroxy vitamin D Further metabolism in the kidney yields 1,25 dihydroxy cholecalciferol (1,25-dihidroxy vitamin D), also known as calcitriol, the active form of vitamin D. Parathyroid hormone increases Vitamin D synthesis. Parathyroid glands are located on the thyroid gland. Functions Calcitriol (active vitamin D) is involved in the following: Regulation of blood calcium and phosphorus. Increases absorption of calcium and phosphorus from the small intestine When blood calcium drops too low, parathyroid hormone is released. Vitamin D and parathyroid hormone increases resorption (breakdown) of bone calcium to release calcium and phosphorus into the blood. Reduces excretion of calcium by the kidneys Blood calcium is required for proper neuromuscular functioning Mineralization of bones (calcitonin from the thyroid gland also plays a role) The above functions also indirectly result in increased deposition of calcium/phosphorus in the bones, by saturating blood with calcium and phosphorus. Vitamin D plays a role in immunity and preventing cancer. RDAs for Adults Adequate Intake (AI) - 10 micrograms, or 400 I.U. This recommendation is now thought to be too low, studies in progress. 10 10 11 Deficiency Rickets – a malformation of the bones occurring in young children Skull malformations in infants Tooth decay Osteomalacia in adults Bone fractures Neuromuscular malfunction due to low blood calcium levels. Toxicity Hypervitaminosis D Abnormally high calcium levels in blood – heart damage Breakdown of bone calcium into the blood, leading to kidney stones Calcification of blood vessels Can occur at supplementation and food fortification as low as about 5 times the RDA, however, more research is needed at this time to determine toxic levels Toxicity does not result from exposure to sunlight. Good Food Sources Fortified milk, cod liver oil, fatty fish, shrimp, egg yolks (not always) 12 Rickets 13 VITAMIN E Occurs in 8 forms in the natural d-isomer: 4 tocopherols – alpha, beta, delta and gamma 4 tocotrienols – alpha, beta, delta and gamma The d-isomer occurs naturally in foods. The l-isomer is synthesized in the lab and does not have as much bio-activity. D-alpha tocopherol is the one we are gong to focus on. It functions as a fat soluble antioxidant. It is regenerated at the cell membrane by vitamin C Absorption and Metabolism Like vitamins A and D, absorbed along with dietary fat. D-alpha tocopherol has been thought to have the most biological activity, at least as a fat soluble antioxidant, according to the textbook. More research is being conducted into the other forms, which also are likely to be important. (not in textbook) Major storage sites – liver and adipose tissue. It travels in blood via lipoproteins. 14 Functions As d-alpha tocopherol: Antioxidant, especially in the cell membranes (cell membranes contain lipids and are vulnerable to oxidative attack). Important antioxidant in the cell membranes of the lung, which are exposed to a large amount of oxygen. Protects red blood cells from oxidation and cell membrane breakdown. Protects LDL cholesterol from oxidation. Protects nervous tissue and myelin. Protects polyunsaturated fatty acids in the body from damage resulting from oxidation. Protects vitamin A from oxidative damage. RDAs for Adults d-alpha tocopherol: 15 mg/day (75 I.U.) Therapeutic doses – 200 to 400 I.U. per day (open to question as other forms of vitamin E also have important functions) 15 Deficiency of d-alpha tocopherol Red blood cell breakage, anemia Hemolytic anemia in premature infants Degeneration of nervous system Leg cramps and weakness Oxidative damage to the body’s cells Toxicity Unlikely, however at high doses can reduce blood clotting and is contraindicated for people undergoing blood thinning therapy. Also, megadoses of individual antioxidants can eventually become pro-oxidants. Good Food Sources Nuts, seeds, wheat germ, plant oils 16 VITAMIN K The coagulation vitamin. Occurs in three forms: K1 – phytonadione or phylloquinone, from plant foods. K2 – menaquinone, synthesized by bacteria in the intestines, provided by certain fermented foods. K3 – menadione – synthesized in the lab – Toxic Absorption and Metabolism Absorbed with dietary fat. Some vitamin K2 is synthesized by bacteria in the large intestine. Functions Coenzyme required for the