Vitamins Flashcards
What are vitamins
- a diverse group of organic molecules required in very small quantities for health, growth, and survival
- many vitamins act as co-enzymes; symptoms of deficiency arise from loss of enzyme activity
- vitamins expand the chemistry available in living systems
DRI
-dietary reference intakes- multiple tables that provide a global view of micronutrient requirements and toxic levels
RDA
- recommended daily allowance (one component of DRI)
- defined as the amount suffient to meet the nutrient requirement of 97-98% of healthy individuals in a given group
- varies for different populations (based on gender, age, etc)
- RDAs are reviewed and changed when research warrants it (relatively frequently)
Range of vitamins
- Deficiency symptoms
- Biochemical parameters of deficiency
- average dietary intake
- nutrient-nutrient or nutrient-drug interations
- toxicity symptoms
How do deficiencies arise?
- poor nutrition
- increased demand
- problem with absorption of one or more vitamins
- interactions with medications
Lipid Soluble Vitamins
- A,D, K, E
- structures resemble lipids
- generally are stored more efficiently than water-soluble
- deficiencies don’t arise as quickly
- toxicity may be a problem (Vit A and D)
Water Soluble Vitamins
- B and C
- more hydrophilic structures
- in general, deficiencies can arise more rapidly if vitamin is unavailable, since they are excreted efficiently
- less likely to be toxic
Vitamin A
-functions:
-visual cycle (rhodopsin and cone opsins)
-synthesis of certain glycoproteins and mucopolysaccharides
-etinoic acid- acts as a hormone
antioxidant
- deficiency: night blindness (early), xerophthalmia (advanced), follicular hyperkeratosis, anemia (despite normal iron intake), poor growth in children, increased susceptibility to infection and cancer
- susceptible groups: poor, malnourished, premature babies
- toxicity: accumulate in liver, usually from supplement overdose; nausea, diarrhea, bone pain, scaly skin, orange skin
- get carotenoids from plants
Vitamin D
- functions:
- maintaining bone
- calcium homeostasis
- acts as a hormone- receptors are present in many tissues, but full range of activity is unknown
deficiency:
- rickets in children
- osteomalacia in adults
- increased susceptibility to breast and other cancers, metabolic syndrome/diabetes, and infections
Susceptible groups: poor, elderly, alcholics
Sources: produced in skin by sunlight converting a cholesterol side-product to vitamin D3
-diet- salmon, liver, egg yolks, but milk, butter and other foods
Vitamin K
- function: localization of enzymes required for blood clotting
- helps catalyze addition of gamma- carboxyglutamate to clotting enzymes
Deficiency: results in easy bruising, bleeding, hemorrhage
Susceptible groups:
- newborn infants, patients on long term antibiotics, elderly and others with defects in fat absorption
- Vit K has a quinone ring
Vitamin E
- Function:
- antioxidant- scavenge free radicals
- protect membranes from damage (like from ROS)
- prevent oxidation of LDL
Deficiency: cardiovascular disease, neurological symptoms
Susceptible groups: patients with severe, prolonged defects in absorption (ex celiac disease) or genetic defects (uncommon)
- closely related compounds called tocopherols and tocotrienols
- dietary sources are oils (corn, sunflower, wheat germ, margarine)
Vitamin C (Ascorbic acid)
- Function:
- cofactor for oxidases involved in collagen formation
- required for synthesis of sterioids in stress response (response to trauma)
- aids absorption of iron
- has antioxidant activity
Defiency:
- mild: bruising, immunocompromise
- severe: scurvy (decreased wound healing, osteoporosis, hemorrhage and anemia, fatigue)
Susceptible groups: people with poor diet, smokers
long term treatment with aspirin, oral contraceptives, and corticosteroids
-critical cofactor for prolyl and lysyl hydroxylases required for collagen biosynthesis
-corkscrew hairs and pinpoint hemorrhages, periodontal disease
Food sources: citrus fruits, green vegetables, tomatoes etc
B-complex vitamins
- Energy releasing:
- Thiamine (B1)
- Riboflavin (B2)
- Niacin (B3)
- Biotin
- Pantothenic acid (B5)
- Pyridoxine (B6)
Hematopoietic:
Folate (B9)
Cobalamin (B12)
Common effects of deficiencies in energy-releasing B vitamins
-symptoms show up first in rapidly growing tissues: Skin- dermatitis, Swollen, red tongue- glossitis, GI- diarrhea
Nervous system also affected because of high energy demand:
- peripheral neuropathy- tingling of extremities
- depression, confusion, lack of coordination, malaise
-different vitamin deficiencies have overallaping symptoms, but also some distinct features
Thiamine (B1)
-function: required cofactor for several enzymes in cellular energy metabolism, particularly critical for nervous system
Deficiency: mild-GI symptoms, depression, fatigue (poor, elderly)
- Moderate- Wernicke-Korsakoff syndrome (alcoholics)
- Severe- Beriberi (people with diet dependent only with polished rice, sometimes alcholics)
- Thiamine is converted to a TPP which serves as a coenzyme for critical metabolic enzymes
Riboflavin (Vitamin B2)
-function: precursor of FAD and FMN, key coenzymes for redox reactions involved in energy metabolism
- deficiency: ariboflavinosis- rash around nose, inflammation of mouth and tongue, burning and itchy eyes, light sensitivity
- susceptible groups: alcholics, deficiency is quite uncommon
- good sources: milk, yogurt, cheese, meat, eggs, broccoli, asparagus, oranges, and whole grain foods
Niacin (Vitamin B3)
- Functions: precursor of NAD and NADP coenzymes important in redox reactions of energy metabolism
- given to patients with hyper-cholesterolemia or hypertriglyceridemia (high doses)
Deficiency: pellagra
-characterized by dermatitis, diarrhea, and mental symptoms (confusion, memory loss, mania)
Susceptible groups: people with corn or millet based diets
Sources: meat and other high protein foods (tryptophan which can be converted to nicotinamide), also cereal grains such as oats, wheat, and rice
Biotin
- function: coenzyme for several carboxylases
- deficiency: rare but can be caused by eating a lot of raw eggs: avidin in eggs protein binds biotin very tightly
Pantothenic Acid (Vitamin B5)
- Function: required for the synthesis of CoA, CoA is a coenzyme for up to 70 different enzymes
- required for TCA cycle and metabolism of all fats and proteins
- deficiency: very rare, symptoms are typical of B vitamins
Pyridoxine (B6)
- function: precursor of pyridoxyl phosphate (PLP) enzyme cofactor
- required for glycogen breakdown and synthesis of GABA and heme
- groups susceptible to deficiency: patients treated with certain drugs (isoniazid- TB)
deficiency: mild-irritability, nervousness, depression
severe- peripheral neuropathy, convulsions, decreased glucose tolerance, hyper-homocysteinemia (cardiovascular risk), anemia
- widespread in foods, with meat, egg yolk, vegetbles and whole grain
- may need to increase RDA
