Download Nutrition and Micronutrients in Pregnancy

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)
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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 (βcarotene)
􀂄 status determined by blood retinol concentration
􀂄 lower levels indicate lower stores
􀂄 primarily liver storage
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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
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􀂄 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
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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)
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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
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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
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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
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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
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Vitamin E: 15 mg/d RDA
􀂄 Food sources:
􀂄 plant foods e.g. grains
􀂄 associated with linoleic content in vegetable oils
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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
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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
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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
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The B Vitamins (8)
􀂄 Involved in energy metabolism
􀂄 thiamin, riboflavin, niacin
􀂄 biotin, pantothenic acid
􀂄 B6, folate, B12 (& red blood cell function)
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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
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Thiamin: Beriberi
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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
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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)
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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
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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
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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
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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
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Biotin: 30 ug/d AI
􀂄 Produced by bacteria in colon
􀂄 Food sources: widespread
􀂄 No increased needs or toxicity described
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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
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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
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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?
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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)
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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
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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
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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
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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
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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)
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Scurvy symptoms: gums and skin
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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
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Summary
􀂄 Water soluble vitamins
􀂄 dissolve in water
􀂄 are easily absorbed & excreted
􀂄 are not stored extensively in tissues
􀂄 seldom reach toxic levels
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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
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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
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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
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