Water soluble vitamins --review with handout Flashcards
Water soluble vitamins
Generally not “stored” in body (B12 = exception)
Chronic intakes DO alter tissues levels
Toxicity usually low (B6 = exception)
Absorption usually high
Excretion typically via urine (once tissue levels saturated)
Breast milk reflects maternal intake/status (folate = exception)
6 mo old breastfed infant, vomiting, ophthalmoplegia, congestive heart failure
thiamine def (beri-beri)(ophtalmoplegia and CHF)
5 yr old child only eats burgers (w/ bun) & milk, now limping & refusing to walk, ~ rash
Vit C def (scurvy)
-often presents w/ not walking
Alcoholic, “found down”, altered mental status, anemic
?B12, thiamine, folate
15 mo old breastfed infant, growth faltering, no longer walking; mom with dietary “limitations”
-B12 (mom w/ dietary limitations)
Obese adolescent, s/p bariatric surgery, can’t walk; falls down
B12
thiamine
Adult, low SES, chronic diarrhea/malabsorption, rash on arms, hands, neck
Pellagra
Thiamin (B1), Riboflavin (B2), Niacin (B3) (energy releasing B complex vit)
Functions:
- All involved in glycolysis/Krebs cycle
- TPP, FAD, NAD; decarboxylation, oxidation-reduction
Food sources: whole & enriched grains
Thiamin: pork, legumes; (decreased in polished rice)
Riboflavin: dairy, eggs, meats
Niacin: meat/poultry; tryptophan = precursor
Thiamin (B1) Deficiency
Beriberi - nervous & cardiovascular systems
-“Dry:” peripheral neuropathy; muscle tenderness (esp legs), weakness & atrophy; foot drop; eventual inability to walk w/o falling
-“Wet:” edema, circulatory collapse, congestive heart failure
Wernicke-Korsakoff (cerebral): confusion, ophthalmoplegia, ataxia, memory loss (complete correction 25%; partial 50%)
Risk for Thiamin Deficiency
Alcoholics
s/p bariatric surgery (esp 1st 6 mo post-op; associated w/ vomiting)
TPN (total parenteral nutrition), w/o thiamin(deficiency occurs w/in 2-3 wk)
Anorexia nervosa
Re-feeding
Endemic in So Asia (maternal & BF infant) – polished rice diet
Infantile beriberi
Infant formula w/o thiamin infants (2-12 mo) present w/: Infection Vomiting Lethargy/restlessness Ophthalmoplegia Low thiamine pyrophosphate, acidosis Prompt response to high dose (50 mg/d x 2 wk)
Riboflavin (B2) deficiency
- low dairy, animal products
- cheilosis (lips cracked, looks like sores)
- angular stomatitis (around mouth)
Niacin (B3) deficiency
-Pellagra
Predisposing factors:
Nutritional/dietary restriction
Cornmeal (w/o germ) based diet (esp historically)
Food faddism / restriction (eg, rice diet)
Breastfed infant of deficient mother
Malabsorption syndromes
Alcoholism
Metabolic “shunting” (carcinoid tumor –> ↑ serotonin –> decreased tryptophan)
Pellagra 4Ds
Diarrhea
Dermatitis:
symmetric, scaling w/ areas depigmentation & hyperpigmentation
aggravated by sun exposure (“Casal’s necklace”)
Dementia:
confusion, dizziness, hallucination
Death
B complex Vitamins: Hematopoietic
folate
B12
Folic Acid
Functions: single C transfers
nucleic acid synthesis
amino acid metabolism
DNA Methylation - epigenetics
Food sources: “foliage,” deep green veg orange juice whole grains (Grains enriched in US since 1998) (Easily destroyed in prolonged cooking)
Situations with Risk of folate deficiency
Inadequate intake or increased destruction in food
Alcoholics
Pregnancy – globally, high rates deficiency; WHO: routine supplementation, women of reproductive age
Hematopoietic conditions
Drug/nutrient interactions
Signs/sx of folate deficiency
*Macrocytic anemia
*Hypersegmented neutrophils
*Glossitis, irritability
*Homocysteinemia
Neural tube defects (occurrence/recurrence)
- Reversible with correction of deficiency
Folate intake for women
Women of child bearing age advised to have intake of 400-800 microgr/day* to prevent neural tube defects (spina bifida, anencephaly)
-Recurrence
-Occurrence
Neural tube closes by 4-6 wk gestation - before most women realize they are pregnant
(Currently ~30-50% of women in US consume enough from diet or take supplements)
NTD risk also increased with MTHFR gene variants
Vit B12 (cobalamin) function
Functions:
Reform tetrahydrafolate from methylfolate (synthesis of methionine)
Catabolism of odd chain length fatty acids
Catalyze isomerization of methylmalonyl Co-A to succinyl Co-A (lipid & CHO metabolism)
Metabolism intimately related to folate
One carbon transfers (methylation)
Interactions essential for homocysteine –> methionine, protein synthesis, nucleic acid syn
Vit B12 Absorption
Cleave vitamin from dietary protein in stomach
Requires Intrinsic Factor from stomach
Cobalamin-IF absorbed in distal ileum
Transport in circulation: Transcobalamin II
Vit B12: absorption, storage, excretion
Enterohepatic circulation
Large liver stores
Excretion: primarily via bile
Dietary sources and requirements of Vit B12
Food Sources: Synthesized by soil bacteria Found only in animal products Requirements: Long term storage & supply Increased requirements if decreased absorption/reabsorption Vegans should take a supplement
Vit B12 Deficiency
Risk factors/situations:
Inadequate IF secretion or antibodies to IF
Gastric atrophy/gastrectomy
Ileal resection
Breastfed infant of B12 deficient vegan mother
Effects:
Macrocytic anemia & hypersegmented neutrophils (just like with folate deficiency)
***Neurologic disturbances: depression, paresthesias, gait disturbances, burning tongue, dizziness
Hematological effects are reversible w/ B12 or folate Neurological effects eventually irreversible
Megaloblastic anemia should not be treated w/ folate unless have ruled out Vitamin B-12 deficiency
Vitamin C (ascorbic acid): func/role
Reversible antioxidant, Vitamin E sparing
Provides reducing equivalents to enzymes:
Reduction of iron –> increased absorption
Leukocyte function (increased [AA] wbc)
Co-substrate in hydroxylation:
Collagen synthesis: hydroxylation of proline & lysine; cross-links for tropocollagen
Hydroxylation of tryptophan –> serotonin
Conversion dopamine –> norepinephrine
Food Sources for Vit C
Fruits and vegetables Contributions by food group in U.S.: 39% fruits 15% potatoes 38% other vegetables
Not in: grains, meat, dairy
Absorption of Ascorbic acid
Active (saturable) process Low intake: ~ 100% Typical intakes (30-180 mg/d): 70-90% Megadoses: 1 - 1.5 g/d: ~ 50% > 10 g/d: 15%
If taking large doses, better absorption if take in divided doses (80 mg/d leads to increased urine excretion
Intakes of 400-500 mg leads to no increased plasma [AA]
Vit C Deficiency: Scurvy
Hemorrhagic signs:
Bleeding gums, ecchymoses, petechiae
Hyperkeratosis of hair follicles + perifollicular hemorrhages
Hypochondriasis: depression, weakness
Hematologic abnormalities
Anemia: iron &/or folate deficiencies, bleeding
Progression: weakness, aching joints/bones/muscles, hemorrhagic signs
When do you often see scurvy in kids?
-autistic kids on restricted diets (rash, gingival hypertrophy, bruises)
Benefits of “megadoses” of Vit C
Prevention/treatment of common cold?
antihistamine effects
neutrophil chemotaxis; duration symptoms
Prevention of CVD, Ca?
RCT do not support
Fruits & vegetables
Wound healing: inflammation, proliferation, maturation
