4/20/2017 Vitamins

Vitamins 􀂄 Vitamins: definition/classification 􀂄 essential, non-caloric organic nutrients 􀂄 needed in very small amounts 􀂄 cofactors (helpers) in cell functions 􀂄 fat soluble: Vitamins A, D, E, K 􀂄 water soluble: B Vitamins, Vitamin C 􀂄 Note: you do not need to memorize the RDA, AI or UL amounts (adult ranges given)

Vitamin A 􀂄 RDA: 700-900 ug/d; UL: 3000 ug/d 􀂄 chemical forms: retinol, β-carotene (can be converted to Vit. A but need 6x amount) 􀂄 food sources: liver, milk (fortified), vegetables (β- carotene) 􀂄 status determined by blood retinol concentration 􀂄 lower levels indicate lower stores 􀂄 primarily liver storage

Functions (essential for): 􀂄 1. vision 2. epithelial tissue 3. growth of bone 4. reproduction 􀂄 Deficiency is prevalent in developing countries: 􀂄 blindness, sickness (􀃈 immune function), death 􀂄 provide Vit. A supplementation, develop rice with higher Vit. A

􀂄 Overdose (chronic 4x, acute 100xRDA) 􀂄 headaches, edema, fatigue, anorexia, skin disorders 􀂄 Retinoic acid as a drug, directly applied to the skin results in rapid turnover of skin cells 􀂄 Retin-A: acne; Renova: antiwrinkle 􀂄 highly toxic: serious birth defects if taken during pregnancy 􀂄 supplementing Vit. A does not help acne

β-carotene 􀂄 Vitamin A precursor 􀂄 Plant sources: brightly coloured e.g. deep orange, dark green 􀂄 effective antioxidant 􀂄 may reduce risk of chronic diseases 􀂄atherosclerosis 􀂄cancers 􀂄macular degeneration (blindness in elderly)

chemical name: cholecalciferol 􀂄 function: regulation of calcium and phosphorus, including bone formation and maintenance 􀂄 status by blood concentration 􀂄 deficiency: rickets and osteomalacia (bone disease in children and adults, respectively) 􀂄 very toxic: calcium deposits in heart & kidneys 􀃆death; UL: 50 ug/d (10x RDA) 􀂄 Enjoying a resurgence in interest especially as rickets is making a comeback

Vitamin D: 5 ug/d AI 􀂄 Food sources: liver, eggs, butter, fish, fortified milk and margarine 􀂄 Sunlight: UV radiation converts precursor molecule (cholesterol backbone) in skin 􀂄 duration specific to race: facial area for 15 min 3-7 x/week 􀃆3 h for dark-skinned 􀂄 Manitoba latitude: April to Oct; use liver stores in winter 􀂄 risk of skin cancer, not Vit. D toxicity

Chemical name: tocopherol 􀂄 Function: antioxidant in cell membranes, integrity of cells (lung, RBC, WBC) exposed to high oxygen concentrations 􀂄 Status: blood concentrations and breakability of RBC

Deficiency is rare 􀂄 hemolytic anemia (premature infants) 􀂄 weakness, impaired reflexes (muscle & nerve function) 􀂄 fat absorption and storage problems 􀂄 Toxicity is rare 􀂄 Latest evidence is that is does not protect against heart disease

Vitamin E: 15 mg/d RDA 􀂄 Food sources: 􀂄 plant foods e.g. grains 􀂄 associated with linoleic content in vegetable oils

Vitamin K 􀂄 Danish “koagulation” 􀂄 Function: blood clotting & bone synthesis 􀂄 Status: by blood clotting test 􀂄 dicumarol (drug) interferes with Vit. K and blood clotting: test before surgery 􀂄 Deficiency: rare except newborns (easy bruising) 􀂄 Toxic in excess (infants, pregnancy): sold as single vitamin by prescription

Vitamin K: 90-120 ug/d AI 􀂄 Bacterial production in colon (~1/2 required) 􀂄 affected by absorption problems/illness 􀂄 antibiotics decrease production 􀂄 Food sources (~1/2 required) 􀂄 green leafy vegetables, cabbage, family 􀂄 liver, eggs, milk 􀂄 beans

Summary Fat soluble vitamins 􀂄 dissolve in lipid 􀂄 require bile for absorption 􀂄 stored in tissues e.g. liver, adipose 􀂄 may be toxic in excess 􀂄caution with supplements

The B Vitamins (8) 􀂄 Involved in energy metabolism 􀂄 thiamin, riboflavin, niacin 􀂄 biotin, pantothenic acid 􀂄 B6, folate, B12 (& red blood cell function)

Thiamin 􀂄 Deficiency disease: beriberi (polished rice) 􀂄 depression, weakness, polyneuropathy 􀂄 Functions: 􀂄 coenzyme (TPP) reactions involving CO2 􀂄releasing energy from glucose & fat 􀂄 synthesis of acetylcholine (neurotransmitter) 􀂄 synthesis of ribose (RNA component) 􀂄 alcohol metabolism

Thiamin: Beriberi

Riboflavin 􀂄 Deficiency disease: ariboflavinosis 􀂄 2 months to evolve, may exist with other B vitamin deficiencies (same food sources) 􀂄 affects skin, eyes, mouth, tongue 􀂄 Functions: 􀂄 coenzyme (FMN, FAD) in energy production: releasing energy from glucose and fat

Niacin 􀂄 Deficiency disease: pellagra (4 D’s) 􀂄 dermatitis, diarrhea, dementia, death 􀂄 diet: cornmeal, salted fat pork, molasses 􀂄 Functions: 􀂄 coenzyme (NAD, NADP) in energy production: releasing energy from glucose and fat 􀂄 synthesis of fatty acids & steroids (cholesterol)

Thiamin, Riboflavin, Niacin 􀂄 DRIs: based on energy requirements 􀂄 higher in growth, pregnancy, lactation, high physical activity, athletes 􀂄 NE (niacin equivalents): niacin (1 mg) synthesized from tryptophan (60 mg) 􀂄priority: protein/neurotransmitter function 􀂄 Supplements do not stimulate energy production unless one is deficient in one of these vitamins

Thiamin, Riboflavin, Niacin 􀂄 Food sources (*also sources of tryptophan): 􀂄 enriched (added back to the natural level) & whole grains; cereals and baked products 􀂄 *legumes 􀂄 leafy green vegetables, mushrooms 􀂄 *meat, fish, eggs 􀂄 *milk & milk products (especially riboflavin) 􀂋 corn tortillas: lime water increases bioavailability of niacin from corn

Thiamin, Riboflavin, Niacin 􀂄 Toxicity of thiamin & riboflavin is rare 􀂄 Niacin is used as a drug for lowering blood cholesterol and treating schizophrenia 􀂄 Niacin toxcity (supplement linked): 􀂄flushing of skin, red skin rash 􀂄tingling sensation in hands/feet 􀂄stomach pain, nausea, diarrhea 􀂄 Body adapts to high doses, but monitor for liver damage

Biotin 􀂄 Deficiency: feeding raw egg white protein (contains avidin) to rats resulted in hair loss, dermatitis and neuromuscular dysfunction 􀂄 avidin binds biotin & denatured by cooking 􀂄 rare in humans (malnutrition) 􀂄 Function: cofactor in 􀂄 energy production from glucose and fat 􀂄 gluconeogenesis 􀂄 amino acid metabolism

Biotin: 30 ug/d AI 􀂄 Produced by bacteria in colon 􀂄 Food sources: widespread 􀂄 No increased needs or toxicity described

Pantothenic Acid 􀂄 Deficiency: rare, general failure of body 􀂄 Functions (100+ steps) 􀂄 cofactor (CoA) in energy metabolism, & synthesis of fatty acids, cholesterol, steroid hormones, neurotransmitters, hemoglobin 􀂄 AI: 5 mg/d, linked to energy needs 􀂄 Food sources: widespread

Vitamin B6 (Pyridoxine) 􀂄 Deficiency: weakness, irritability, convulsions, microcytic anemia, greasy dermatitis 􀂄 e.g. heating infant formula & destruction of B6 􀂄 Functions (coenzyme = PLP): 􀂄 NB. amino acid & protein metabolism, and neurotransmitter synthesis 􀂄 50+ steps in energy metabolism 􀂄 synthesis of hemoglobin 􀂄 synthesis of niacin from tryptophan

Vitamin B6 􀂄 RDA: 1.3 mg/d; linked to protein intake 􀂄 Food sources: green leafy vegetables, meat, fish, poultry, legumes, fruits, whole grains 􀂄 Toxicity from supplements: >1000 mg/d, numbness due to nerve damage, reversed when quit supplements 􀂄 Supplements: may be some benefit in carpal tunnel syndrome?

Folate (Folic Acid) 􀂄 Deficiency: affects rapidly dividing cells; 􀂄 macrocytic anemia 􀂄 nerve function & neural tube defects (NTDs) 􀂄1/1000 births, 2nd most common birth defect 􀁎At risk: 􀁎 pregnant women, premature infants 􀁎 elderly (folate interacts with medications) 􀁎 alcoholics (􀃈 folate absorption) 􀁎smoking (folate inactivation in lungs)

Folate 􀂄 Functions: 􀂄 coenzyme for synthesis of DNA, RNA, amino acids 􀂄NB. Growth, early embryonic life and tissue turnover (intestine, skin, RBC) 􀂄 Low folate status may contribute to hyperhomocyteinemia, a risk factor for cardiovascular disease

Folate (“foliage”) 􀂄 RDA: 400 ug/day 􀂄 additional 200 ug/day during pregnancy 􀂄 recommendations for folate supplementation before pregnancy 􀂄 Food sources: leafy green vegetables, asparagus, fruit, legumes, seeds, liver 􀂄 Folate fortification of flour 􀂄 Potential problem: masking Vitamin B12 deficiency

Vitamin B12 (cobalamin) 􀂄 Deficiency: pernicious anemia (macrocytic), neuromuscular dysfunction 􀂄 Functions: 􀂄 myelin in nerve fibers (nerve transmission) 􀂄 coenzymes in energy & amino acid metabolism 􀂄 B12 binds intrinsic factor (IF) in stomach & facilitates absorption in small intestine 􀃈 B12 absorption in elderly

Vitamin B12 (RDA: 2.4 ug/day) 􀂄 If no intrinsic factor, injections of B12 􀂄 Food sources: animal origin, fermented products, fungi, algae, fortified soymilk 􀂄 Risk of deficiency: breastfed infants of vegan mothers (Adults have body stores for 5 yrs) 􀂄 Folate supplementation masks B12 deficiency i.e. improves anemia but progressive malfunctioning of nerves and muscles; creeping paralysis

Vitamin C (Ascorbic Acid) 􀂄 Deficiency: scurvy 􀂄 Function: 􀂄 collagen/connective tissue (bones, teeth, skin, tendons) 􀂄 antioxidant protection 􀂄 promotes iron absorption 􀂄 enhances immune function 􀂄 synthesis of thyroxine (regulates basal metabolic rate and body temperature)

Scurvy symptoms: gums and skin

Vitamin C 􀂄 RDA: 75-90 mg/d (old RNI: 20-40 mg/day) 􀂄 additional 35 mg/d for smokers (and passive smoke) 􀂄 Food sources: citrus, vegetables 􀂄 Low toxicity but problems if >2 g/day ; e.g. Altered insulin response to carbohydrate 􀂄 Vit. C supplements & common cold: ?? Placebo effect

Summary 􀂄 Water soluble vitamins 􀂄 dissolve in water 􀂄 are easily absorbed & excreted 􀂄 are not stored extensively in tissues 􀂄 seldom reach toxic levels

Controversy 􀂄 Dietary Antioxidants: Food or Pills? 􀂄 Epidemiological studies show protective effects of food sources (diets high in fruits and vegetables) 􀂄 Foods contain many protective chemicals in addition to vitamins e.g. phytochemicals 􀂄 The theory of free radicals, antioxidants and disease

Research on supplementation: 􀂄 Positive outcome (last year-now debateable): supplementation of Vitamin E may provide additional antioxidant protection and decrease chronic disease risk e.g. heart disease or may increase mortality in some susceptible Individuals 􀂄 Negative outcome: supplementation of β-carotene increased incidence of lung cancer in smokers →research study stopped

Who needs a supplement? 􀂄 Those who routinely fail to obtain recommended amounts of vitamins and minerals from the diet 􀂄 Those with special needs e.g. Pregnant, elderly