Chapter 7: Vitamins
Chapter 7: Vitamins NTR 213-05
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This 22 page Class Notes was uploaded by Elizabeth Weathers on Thursday March 3, 2016. The Class Notes belongs to NTR 213-05 at University of North Carolina - Greensboro taught by Laurie H. Allen in Winter 2016. Since its upload, it has received 47 views. For similar materials see Introductory Nutrition in Environmental Science at University of North Carolina - Greensboro.
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Date Created: 03/03/16
Vitamins Organic: contain carbon Micronutrients: essential in small amounts Functions: promote and regulate body processes necessary for growth, reproduction, and the maintenance of health Ex: making hemoglobin, helping harvest energy, assisting with immunity, promoting bone health, helping remove pollutants (oxidants) from the body NOTE: fat soluble vitamins are more likely to be toxic vs. water soluble vitamins because the body stores them while excess water soluble vitamins are excreted Vitamins Water soluble Fat soluble B Vitamins Vitamin C Vitamin A Thiamin Pantothenic acid Vitamin B Vitamin D Riboflavin 6 Vitamin E Niacin Folate Biotin Vitamin B 12 Vitamin K Vitamin Fortification Adds nutrients to foods Government mandated and voluntary Prevents deficiencies leading to diseases but may also cause toxicity Tips for Preserving Vitamins Vitamin Bioavailability Affected by: Absorption Fat-soluble vitamins: need dietary fat Transport in blood Water-soluble vitamins: blood proteins Fat-soluble vitamins: chylomicrons Conversion of inactive provitamins or vitamin precursors into active vitamins Vitamin Absorption Coenzymes Bind enzymes to promote their activity Carriers of electrons, atoms, or chemical groups that participate in the reactions Organic non-protein molecules Ex: B vitamins NOTE: all B Vitamins are coenzymes, but not all coenzymes are B Vitamins Free Radicals & Antioxidants Reactive oxygen molecules: cause oxidative damage by stealing electrons from other compounds, causing changes in their structure and function Examples: Free radicals – generated by the body or from exposure to the environment Antioxidants: destroy reactive oxygen molecules Ex: Vitamin C, vitamin E, and selenium Meeting Vitamin Needs DRIs include RDA, AI, and UL Vitamin A and C (Iron,Calcium) amounts are required on food labels as %DV This would change with proposed new food label: Vitamin A&C could be removed, while Vitamin D could be added Water-Soluble Vitamins B vitamins: involved in converting the energy in carbohydrate, fat, and protein into ATP Vitamin C: needed to make connective tissue and as an antioxidant Choline: vitamin? (will not be on our exam) Not stored - need to be consumed regularly Excreted in urine Thiamin (Vitamin B) Coenzyme needed for glucose breakdown of glucose to provide energy Needed for metabolism of other sugars, certain amino acids and synthesis of ribose (in RNA) Important for nerve function because: Glucose is nerve cell energy source Needed for synthesis of neurotransmitters (chemical signals from neurons) RDA: men = 1.2 mg/day; women = 1.1 mg/day Sources: bran layer of whole grain, enriched grains, pork, legumes, and seeds Deficiency: Beriberi: weakness, nerve degeneration, heart changes Wernicke-Korsakoff syndrome in alcoholics: mental confusion, psychosis, memory disturbances, coma Excess: no reported effects Riboflavin Functions Forms two active coenzymes that act as electron carriers functioning in reactions needed to produce ATP from carbohydrate, fat, and protein Involved in converting folate, niacin, vitami6 B and vitamin K into their active forms. RDA: men = 1.3 mg/day; women = 1.1 mg/day Sources: Animal: dairy products, liver, red meat, poultry, fish Plant: whole grains, enriched grains, asparagus, broccoli, mushrooms, leafy greens Deficiency: injuries heal poorly cracking of lips and corners of mouth sensitivity to light eye burning, tearing, itching skin flaking around nose, eyebrows, earlobes Excess: no reported effects but turns urine bright fluorescent yellow Niacin Role: Coenzyme in glucose metabolism and synthesis of fatty acids and cholesterol RDA: men = 16 mg NE/day ; women = 14 mg NE/day Sources: Animal: meats, fish Plant: peanuts, whole and enriched grains, legumes, wheat bran, synthesized from the essential amino acid tryptophan Deficiency: Pellagra: fatigue, decreased appetite, indigestion, 4Ds = dermatitis, diarrhea, dementia, death Excess: no reported effects from food but supplements can be toxic causing skin flushing and rash, tingling in hands and feet, nausea, vomiting, diarrhea, high blood sugar levels, liver function abnormalities, blurred vision Vitamin B6 Important for: amino acid and protein metabolism synthesis of nonessential amino acids, neurotransmitters (myelin sheath), hemoglobin conversion of tryptophan into niacin glycogen breakdown 3 forms: pyridoxal, pyridoxine, pyridoxamine converted into active coenzyme pyridoxal phosphate needed for the activity of >100 enzymes in carbohydrate, fat, and protein metabolism RDA: men and women ages 19 to 50 = 1.3 mg/day Sources: chicken, fish, pork, organ meats, whole grains, legumes, sunflower seeds, bananas, broccoli, spinach, some fortified cereals (refined grains are not good sources) Deficiency: poor growth, skin lesions, decreased immunity, anemia, neurological symptoms Excess: no reported effects from food but supplements can be toxic causing severe nerve impairment Folate (folic acid) functions Folate coenzymes needed for DNA synthesis (especially needed in rapidly-dividing tissues) and some amino acid metabolism Important in early pregnancy for neural tube formation, which develops into the brain and spinal cord Prevent homocysteine levels from rising to prevent heart disease NOTE: synthetic folate (folic acid) is absorbed better than natural folate; excess folate can mask a Vitamin B12 deficiency RDA: men and women = 400 µg/day Sources: enriched grains, leafy greens, asparagus, legumes, nuts, oranges, liver, yeast Deficiency: neural tube defects including spina bifida and anencephaly, macrocytic or megaloblastic anemia, poor growth, nerve development and function problems, diarrhea, tongue inflammation, increased risk of heart disease and some cancers Excess: concerns that excess will prevent folate deficiency symptoms and ma12 B deficiencies Vitamin B12 (cobalamin) functions Important for: ATP production from certain fatty acids Conversion of homocysteine to methionine Maintenance of myelin coating on nerves Amino acid and protein metabolism RDA: men and women = 2.4 µg/day Sources: found naturally only in animal products, also in fortified products Deficiency: pernicious anemia, increased homocysteine, decreased folate activation, numbness and tingling, gait abnormalities, memory loss, disorientation, paralysis, death Excess: no reported effects from intakes of up to 100 µg/day from food or supplements Folate & Vitamin B12 Needed for synthesis of neurotransmitters, hormones, bile acids, and carnitine (needed for fatty acid breakdown) Antioxidant in blood and body fluids Helps maintain the immune system Regenerates active antioxidant form of vitamin E Enhances iron absorption Vitamin C (ascorbic acid) Synthesis and maintenance of collagen, the base of all connective tissue Needed for synthesis of neurotransmitters, hormones, bile acids, and carnitine (needed for fatty acid breakdown) Antioxidant in blood and body fluids Helps maintain the immune system Regenerates active antioxidant form of vitamin E Enhances iron absorption RDA: men = 90 mg/day, women = 75 mg/day Sources: citrus fruits, strawberries, kiwis, cantaloupe, cabbage-family and dark-green vegetables, green and red peppers, okra, tomatoes, potatoes Deficiency: scurvy (gum and tooth problems, joint pain, bleeding, poor wound healing, bone fractures, fatigue, depression, hysteria) Excess: excessive vitamin C supplementation can cause diarrhea, nausea, abdominal cramps, possible increased kidney stone formation Water-soluble Vitamins B vitamins: involved in converting the energy in carbohydrate, fat, and protein into ATP Vitamin C: needed to make connective tissue and as an antioxidant Choline: vitamin? Not stored - need to be consumed regularly Excreted in urine Fat-soluble Vitamins Vitamins A, D, E, & K Found with fats in foods Require special handling for absorption, transport and excretion Excretion limitations increases the risk of toxicity Stored in the liver and fatty tissues Intakes can vary without a risk of deficiency if average intake over weeks/months meets needs Vitamin A Retinoidschemical forms of preformed vitamin A Retinol, retinal, retinoic acid Carotenoids: yellow-orange pigments synthesized by plants and many microorganisms Some are vitamin A precursors converted to retinoids Example: beta-carotene, provitamin converted into vitamin A Cell differentiation Immature cells change in structure and function to become specialized by changing gene expression (turning genes on and off) Necessary for maintenance of epithelial tissue Part of rhodopsin, a visual pigment in the eye When light strikes rhodopsin, it initiates a series of events that result in a nerve signal being sent to the brain, which allows us to see Carotenoids may function as antioxidants RDA: men = 900 µg/day, women = 700 µg/day Sources: vitamin A in animal products (eggs, dairy), provitamin A in fruits and vegetables, beta-carotene in orange, yellow, and dark green vegetables Deficiency: xerophthalmia (night blindness progressing to permanent blindness), abnormal jaw bone growth in children, increased infections Excess: nausea, vomiting, headache, dizziness, blurred vision, lack of muscle coordination, birth defects, liver damage, bone fractures; excess carotene can cause hypercarotenemia Vitamin D Made in skin with exposure to ultraviolet (UV) light Inactive until modified in liver and kidneys Essential in the diet only when exposure to sunlight is limited or the body’s ability to synthesize it is reduced Vitamin D Activation Vitamin D Functions Maintains normal levels of the minerals calcium and phosphorus in the blood Calcium is needed for bone health and functioning of nerves, muscles, glands, and other tissues Low blood calcium stimulates parathyroid hormone (PTH) release which stimulates vitamin D activation Changes gene expression Intestines: turns on genes for calcium absorption Bone: turns on genes bone breakdown RDA: adults 70 and under = 600 IU (15g)/ day Sources: not widespread in diet, liver, egg yolks, oily fish (for example, salmon), fortified foods Deficiency: low calcium absorption leading to rickets in children (pigeon breast and bowed legs) and osteomalacia, which can lead to osteoporosis in adults Excess: causes high calcium concentrations in blood and urine, deposition of calcium in soft tissues such as the blood vessels and kidneys, and cardiovascular damage Barriers to Meeting Vitamin D Needs Age Geographical Location Use of sunscreen/ cultural body coverings: block skin’s exposure to the sun Skin color: the amount of melanin in your skin can bock some UV rays Vitamin E Antioxidant Protects lipids including those in membranes of red blood cells, white blood cells, nerve cells, lung cells Defends cells against damage caused by heavy metals (lead and mercury) Reduced risk of heart disease, cancer, Alzheimer’s disease, macular degeneration, other chronic diseases Possible anti-inflammatory functions, modulation of immunity, regulation of cell growth and death genes, detoxification of harmful substances RDA: adults = 15 mg alpha-tocopherol/day Sources: seeds, nuts, plant oils, leafy-green vegetables, wheat germ, fortified cereals Deficiency: hemolytic anemia in infants; rare in adults causing poor muscle coordination, weakness, impaired vision Excess: no reported effects from food but large doses can interfere with blood clotting Vitamin K Functions Needed for: production of clotting factors synthesis of proteins involved in bone formation and breakdown ANTICOAGULANT S Supplements Contain vitamins and minerals, herbs and other plant-derived substances, and/or body compounds not essential in the diet Help obtain adequate amounts of specific nutrients but do not provide all the benefits of foods Herbal Supplements Herb: nonwoody, seed-producing plant that dies at the end of the growing season Also refers to any botanical or plant-derived substance Ex: garlic, ginko, saw palmetto, St. John’s wort Regulation of Supplements Dietary Supplement Health and Education Act (DSHEA) of 1994 defined the term dietary supplement and created labeling standards FDA established “current Good Manufacturing Practice” (cGMP) regulations Requires manufacturers to test their products to ensure identity, purity, strength, and composition FDA pre-market review required if ingredient not sold in the US before October 15, 1994 Choosing Supplements Do not exceed 100% of Daily Values Consider why you want it Compare product costs Read the label Check the expiration date Consider your medical history Approach herbal supplements with caution Report harmful effects What Should you do? Focus on foliage for folate, vitamin A, and vitamin K B (vitamin) sure Get your antioxidants Try for 5 colors of fruits and veggies each day Soak up some D Get outside to stay fit and make some vitamin Have three servings of dairy per day boost intake