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Transcript
Water soluble Vitamins Chapter 8 1 Water Soluble Vitamins Objectives List the major functions and deficiency symptoms for each water soluble vitamin Lit three important food sources for each water soluble vitamin Describe toxicity symptoms for excess consumption of certain water soluble vitamins Describe some cancer causing mechanisms, and describe how diet and nutrition are related to their minimization 2 Water Soluble Vitamins Excess readily excreted from the body Large amounts can be lost in food processing and preparation focus on regular intake of water soluble vitamins, which are; Stir fry, steam best for retaining vitamin content Eight B vitamins and Vitamin C Table 8-3 Summary B vitamins often found together in foods lack of one, may indicate others are low function as coenzymes fig 8-1 key roles in metabolism breakdown and synthesis of energy containing nutrients 3 B vitamins Many B vitamins are interdependant in metabolism (Fig 86) after ingestion, broken down into free vitamins in stomach and SI absorbed in SI 50-90% reformed into coenzymes in cells as needed Intake is plentiful in our society Due to fortification and availability other areas of world - health concern elderly / alcoholics also a concern long term deficiency - not clear short term - fatigue, other physical symptoms related to slowing of metabolic processes 4 B vitamins Grains and seeds modified by processing - milling crushed - germ, bran and husk removed leaving starch containing endosperm flour, bread and cereals enrich flour with thiamin, riboflavin, niacin folate and iron still lack B-6, E, zinc and magnesium, and fiber choose whole grains Brown rice, whole wheat breads, whole wheat or brown rice pasta 5 Thiamin (B1) Used to release energy from carbohydrates (fig 8.6) deficiency - beriberi (‘I cant I cant’) weakness, loss of appetite, irritability occurs when rice (white) is staple glucose poorly metabolized primary fuel for brain and nerve cells occurs after only 10 days on thiamin free diet Thiamin in Food pork, whole grains, soy milk, fortified cereals, enriched flour (fig 8.7) RDA 1.1-1.2 mg / day average 150% (M) 100% (F) poor and elderly at risk supplements non toxic - lost in urine No upper limit set for intake - no extra benefit 6 Riboflavin (B-2) Used in many energy yielding pathways as coenzymes (fig 8.6) Also in vitamin and mineral metabolism and as an antioxidant Deficiency inflammation of mouth and tongue dermatitis, cracking of skin around mouth develop after 2 months occurs with niacin, thiamin and B-6 deficiency as these nutrients often occur in the same foods Riboflavin in food (p 256) milk, enriched grains, fortified cereal, RDA 1.1-1.3 mg / day alcoholics at risk no toxic indications for megadoses 7 Niacin (B-3) Is a pair of related compounds pellagra - deficiency syndrome rough or painful skin early symptoms - poor appetite, weakness and weight loss Symptoms - dementia, diarrhea and dermatitis (skin exposed to sun) Niacin in foods Co-enzyme in energy utilization and in synthetic pathways for fatty acids Fig 8.6 broad use - widespread symptoms tuna, poultry, fortified cereal, wheat bran, asparagus, peanuts (p 265) niacin is heat stable RDA 14 - 16 mg / day risk with alcoholism and disorders of tryptophan metabolism toxic > 35 mg/day - headache, itchy 8 Pantothenic Acid Co enzyme for energy release from carbohydrate, fat and protein -fig 8.6 forms coenzyme A deficiency - rare burning/tingling in feet or hands Pantothenic acid in foods present in all food sunflower seeds, mushrooms, peanuts, eggs Adequate Intake 5 mg/day alcoholism - poor diet symptoms are likely to be masked by other B vitamin deficiencies No toxicity in known 9 Biotin 2 forms - active in fat and carbohydrate metabolism synthesis of glucose, Fatty acids, DNA breakdown of Amino Acids deficiency - scaly inflammation of skin decreased appetite, nausea, anemia, depression, muscle pain and weakness Biotin in food cauliflower, egg yolk, peanuts, cheese intestinal bacteria synthesize biotin Antibiotics reduce absorption raw egg whites - have the protein avidin - binds biotin so that it is not absorbed Adequate intake 30 ug/day - avg 2X relatively non toxic 10 B-6 Family of three compounds coenzyme for metabolism Carbohydrate, fat and protein deficiency - widespread symptoms depression, vomiting, skin disorders, nerve irritation, impaired immunity metabolism of AA - needs B-6 split Nitrogen from AA - synthesis of non-essential AA synthesis of neurotransmitterscommunication 1950’s infant formula - heat destroyed B-6 - deficiency resulted in convulsions synthesis of hemoglobin (O2) and white blood cells (immunity) role in recycling homocysteine along with B12 and folate - elevated levels of homocysteine associated with CVD 11 risk B-6 in foods Fig 8-8 Animal products, fortified cereal, potatoes, milk, banana, avocado animal sources are more absorbable measurement in food is difficult RDA 1.3 - 1.7 mg/day set high due to high protein intake high protein breakdown Athletes - may need slightly more increased glycogen and AA use as fuel higher protein intake Usually sufficient from increased food and protein intake in athletes 12 B-6 (continued) Alcoholism -metabolites formed in ethanol - increase destruction of B6 dec. absorption, and synthesis of coenzyme as well liver disabled (cirrhosis and hepatitis) B-6 toxicity 2 - 6 g/day for 2 months irreversible nerve damage also with long term 200 mg/day abuse in bodybuilders symptoms - difficulty walking, hand and foot numbness upper limit 100 mg/day B-6 tablets can be up to 500mg, taking a toxic dose is quite easy 13 Folate Helps in formation of DNA Metabolism of AA (homocysteine) deficiency - early phases of red blood cell synthesis - immature cells can not divide - because DNA is not formed Form megaloblasts - enlarged cells macrocytic anemia - dec O2 carrying after 7-16 weeks on folate free diet Maternal deficiency - neural tube defects in fetus - fig 8-9 Spina bifida and anencephaly Cancer therapy - methotrexate hampers folate metabolism affects rapid cell division of cancer cells as well as intestinal and skin cells hair loss, Diarrhea, vomiting 14 Folate in foods Green leafy veg., organ meats, sprouts, orange juice food processing and preparation destroys 50-90% of folate in food (heat) RDA 400 ug/day DFE-(Dietary Folate Equivalent) synthetic folate absorbs a lot better than natural folate multiply intake by 1.7 for dietary folate equivalent - DFE Many have inadequate intake - this has gotten a lot better since mandatory enrichment of grain products in 1998 Folate enrichment now mandatory Women of child bearing age of concern Pregnant women - 600 ug / day As are the elderly and alcoholics 15 B - 12 Family of compounds that contain mineral cobalt complex means of absorption synthesized by bacteria and fungi B-12 released by digestion - food interacting with stomach acid free B-12 binds with intrinsic factor B-12 / intrinsic factor complex absorbed in Small Intestine 30-70% of dietary B-12 absorbed without I Factor only 1-2% absorbed 95 % of deficiencies due to absorption problems decline in intrinsic factor and absorption with age Require monthly injections of B-12 16 B-12 functions Variety of cellular processes conversion of folate to active form maintenance of myelin sheaths that insulate nerve fibers patchy degeneration paralysis...death Pernicious Anemia - weakness, sore tongue, back pain, apathy, tingling in extremities 3 years for nerve destruction which is irreversible Generally starts after middle age • 10-20 % of older adults infants breast feeding from vegan mothers that are B12 deficient long term nervous system problems brain growth, spinal cord, intellectual development 17 B - 12 in food Meat, milk, eggs, seafood Fortified soy milk RDA 2.4 ug/day Average intake 2-3 times RDA Provides enough for 2-3 years storage in liver takes 20 years without B-12 absorption to exhibit nerve destruction Vegans, elderly at risk Supplementation non toxic 18 Vitamin C Most animals make vitamin C from glucose absorbed in SI - 70-90% 50 % absorbed with mega dose Role in synthesizing collagen (protein) connective tissue, bone, teeth, tendons, blood vessels, wound healing water soluble antioxidant Reduces formation of nitrosamines (cause cancer) Maintain folate and vit. E function Enhances iron absorption toxicity of vitamin C due to over absorption of iron vital for function of immune system 19 Vitamin C Dr. Linus Pauling - 1g common cold - may decrease duration but not incidence Large dose eliminated in urine absorption saturated at 200mg/day Vit C in Food - fig 8-11 Red and green peppers, cauliflower, brocolli, cabbage, fruits lost in processing • heat, iron, copper, O2 exposure RDA 75-90 mg/day (smokers -add 35 mg a day to RDA) Average intake twice the RDA deficiency - scurvy 20- 40 days without vit C Weakness, opening of healing wounds, bleeding gums, pinpoint hemorrage 20 Toxicity of Vitamin C Probably not toxic below 1g regular consumption of high doses Hemochromatosis over storage of iron mega-dose - alert physician stomach inflammation, diarrhea, iron toxicity can alter medical test results for diabetes Fig 8-12,13 review- vitamins in foods functions, deficiency, toxicity, absorption Table 8-3 21 Choline Latest addition to the list of essential nutrients - not yet classified as a vitamin Choline is part of acetylcholine a neurotransmitter Choline is also part of phospholipids (lecithin) and participates in some aspects of homocysteine metabolism Found in milk, liver, eggs and peanuts Average intake twice the RDA of 425-550 mg/day Vitamin like compounds carnitine, inositol, taurine and lipoic acid are required for proper metabolism but are not essential in the diet, as they can be manufactured in the body 22