Exam 3: Chapter 13 Flashcards
What vitamins are considered water-soluble?
- B-vitamins
- Thiamin
- Riboflavin
- Niacin
- Pantothenic acid
- Biotin
- Vitamin B-6
- Folate
- Vitamin B-12
- Vitamin C
- Choline*
Generally speaking, is the risk of toxicity from water-soluble vitamins high or low?
- Generally low
- Risk of toxicity less than fat-soluble
What cooking methods are best to keep vitamins in foods?
Why do we enrich food and what vitamins and minerals are added to foods for enrichment?
Grains are important source of B-Vitamins, but during milling the germ, bran and husk layers are removed leaving the starchy endosperm
To counteract nutrient loss from milling, nearly all bread and cereal products are enriched with 4 B-vitamins:
- Thiamin
- Riboflavin
- Niacin
- Folic Acid
- Iron (a mineral)
When did enrichment begin and why?
Enrichment began in the 1940’s to protect against deficiency diseases.
Thiamin (B1) Deficiency
- Beriberi
- Sinhalese (I can’t, I can’t)
- Impairs
- Peripheral neuropathy
- Two types—wet and dry
- Congestive heart failure
- Wernicke-Korsakoff Syndrome
- Alcohol
- 1) decrease absorption
- 2) increases excretion
- 3) poor diet
- Alcohol
Thiamin Toxicity
No UL
Riboflavin (B2) Toxicity
No UL
Riboflavin (B2) Deficiency
Ariboflavinosis
Niacin (B3) Toxicity
- UL: 35 mg
- applies only to supplements and fortification
Niacin (B3) Deficiency
- Pellagra
- 4 D’s
- Dermatitis, Diarrhea, Dementia– if not treated
- Death
Pantothenic Acid Toxicity
•No UL—no known toxicity
Pantothenic Acid Deficiency
Very rare
Biotin Toxicity
No UL
Biotin Deficiency
- Biotinase enzyme deficiency
- Excessive consumption of raw eggs (avidin)
Vitamin B-6 (pyridoxine) Toxicity
- UL: 100mg
- Irreversible nerve damage
Vitamin B-6 (pyridoxine) Deficiency
Microcytic hypochromic anemia
Folate Toxicity
- UL: 1 mg—synthetic folic acid
- May mask B-12 deficiency
Folate Deficiency
- Megaloblastic (macrocytic) anemia
- Neural Tube Defects
- Maternal deficiency of folate plus genetic predisposition
- All women capable of getting pregnant urged to take in 400 micrograms of folic acid
- Current fortification yields about 200 micrograms of folic acid daily
Vitamin B-12 (cobalamin) Toxicity
No UL
Vitamin B-12 (cobalamin) Deficiency
-
Pernicious Anemia
- Inadequate production of the intrinsic factor
- Macrocytic Anemia (megaloblastic anemia)
-
Neurological changes
- Sensroy disturbances in the legs (burning, tingling, numbness)
- Loss of concentration and memory
- Disorientation and dememtia
-
Elevated plasma Homocysteine concentrations
- Lead to heart attacks and strokes
Vitamin C Toxicity
UL: 2 g
Vitamin C Deficiency
- Scurvy
- Cancer and heart disease
Why do smokers need additional Vitamin C? How much more do they need?
Smokers need several times more vitamin C than non-smokers because the effectiveness of that vitamin is decreased by nicotine.
Smokers need an additional 35 mg/day.
What individuals are at risk of Vitamin B-12 Deficiency?
- Atrophic gastritis
- Malabsorption
- Treatment
- Monthly injections
- Nasal gel
- Very high oral doses (1-2mg)
- Passive diffusion
- Treatment
- Vegans
What is the difference between the terms “folate” and “folic acid”, and where do each of these come from?
Folate is the generic name while Folic Acid is the synthetic form (ie from supplements). Folate can be found in foods such as orange juice, life cereal, and lentils.
In terms of exposure to heat, is Niacin more or less stable compared to the other water soluble vitamins?
Niacin is more heat stable in comparison to other water soluble vitamins.
What are the two forms of Niacin?
- Nicotinic acid
- Nicotinamide
What amino acid can Niacin be synthesized from?
tryptophan
What happens when riboflavin is exposed to light?
riboflavin is destroyed by exposure to light
Functions of Thiamin
•Coenzyme form:
•thiamin pyrophosphate (TPP)
•Required for carbohydrate and branched chain amino acid metabolism
- Decarboxylation reactions –removal of carbon dioxide
- Glucose→Pyruvate→Acetyle-CoA
- CAC
- Alpha-ketoglutarate→succinyl-CoA
- Additional B-vitamins needed for these reactions
•Pentose phosphate pathway
- Coenzyme for transketolase
- Converts the 6-carbon glucose to 5-carbon pentose
Riboflavin (B2) Functions
- Coenzymes: flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)
-
Energy metabolism
- Citric acid cycle
- Succinate→Fumerate
- Beta-oxidation
- Fatty acids to acetyl-CoA—the enzyme fatty acyl dehydrogenase requires FAD
- Citric acid cycle
- Other B vitamin functions
- Antioxidant function (glutathione synthesis)
Niacin Functions
- Coenzymes: NAD+ and NADPH
- Oxidation-reduction reactions
- Required in at least 200 reactions especially ATP production
- NAD+ is required for catabolism of carbohydrate, fat and protein
- The Coenzyme Form of Niacin, NAD+ is required for Glycolysis and the Citric Acid Cycle
Pantothenic Acid functions
- Coenzyme A (acetyl-CoA)
- Acyl carrier protein
Biotin Functions
- Coenzyme in carboxylase reactions (adds CO2)
- Pyruvate→oxaloacetate
- Breakdown of some AA to use as energy
- Carboxylation of acetyl-CoA to form malonyl-CoA so fatty acids can be synthesized
Vitamin B-6 Functions
- In metabolism
- PLP coenzyme involved in amino acid metabolism
- Glycogenolysis
- In immunity
- Supports normal function and regulates gene expression
- Synthesis of compounds
- In the red blood cell, heme is made, neurotransmitters also made like serotonin, DOPA, GABA
Functions of Folate
- Central coenzyme form: tetrahydrofolic acid (THFA)
- DNA synthesis
- Amino acid metabolism
- Neurotransmitter synthesis
- Dopamine, norepinephrine
Vitamin B-12 Functions
- Functions
- Cofactor in 2 enzymatic reactions
- Formation of methionine from homocysteine
- Enzyme methylmalonyl mutase needed for fatty acid metabolism
- Cofactor in 2 enzymatic reactions
Vitamin C Functions
- Reduction-oxidation reactions (electron donor)
- Cofactor for metalloenzymes
- Ferrous (fe 2+) reduced form coverted to oxidized form (ferric, Fe3+) during enzymatic activity.
- Cofactor for metalloenzymes
- Collagen synthesis
- Connective tissues
- Synthesis of other vital compounds
- Cholesterol to bile acids
- Hormones—keeps metalloenzyme in the reduced state
- Antioxidant activity
- Iron absorption
- Immune function
Food Sources of Thiamin
Food Sources of Riboflavin
Food Sources of Niacin
Food Sources of Pantothenic Acid
Food Sources of Biotin
Food Sources of Vitamin B-6
Food Sources of Folate
Food Sources of Vitamin B12
Food Sources of Vitamin C
Absorption, transport, storage, and excretion of Vitamin B12
- Free vitamin binds to R-protein
- Released by pancreatic lipases
- Free vitamin then binds with intrinsic factor
Digestion and Absorption of Vitamin B12, in detail
What is intrinsic factor and why do we need this? Where is it produced?
Intrinsic factor (IF), also known as gastric intrinsic factor (GIF), is a glycoprotein produced by the parietal cells of the stomach. It is necessary for the absorption of vitamin B12 (cobalamin) later on in the small intestine.
