vitamin a and vitamin c presentation
TRANSCRIPT
Vitamin A and Vitamin C
Theresa Camardo
Intro
Both Vitamin A and Vitamin C are necessary for proper immune system function.
Vitamin A
Fat-soluble “Vitamin A” is actually a term that refers to a
group of substances that include retinol (preformed Vitamin A), retinal, retinoic acid, retinyl esters.
“Vitamin A” can also refer to precursor compounds known as carotenoids.
Absorbed in the small intestine (70-90%); more than 90% located in liver
Structure of Vitamin A
Source: http://www.bio-pro.de/en/region/stern/magazin/00403/index.html
Vitamin A: Functions
Growth (production of HGH, normal functioning of osteoblasts and osteoclasts)
Reproduction Embryonic development (retinoic acid influences cell
differentiation) Vision (eye uses retinal to transduce light into neural signals and
retinoic acid to maintain cornea/conjuctival membrane differentiation which prevents xerophthalmia)
Gene expression (retinioic acid regulates expression of encoding genes for structural proteins, enzymes, extracellular matrix proteins, and retinol binding proteins and receptors)
Immune function (retinol regulates lymphocyte physiology) Glycoprotein synthesis
Carotenoids
Plant pigments – deep colors alpha-carotene, beta-carotene, lycopene,
lutein, xeaxanthin, beta-cryptoxanthin alpha-carotene, beta-carotene, and beta-
cryptoxanthin can be converted in Vitamin A (provitamin A)
Fat-soluble Absorbed in the intestine and stored in
tissues
Vitamin A: Food Sources
Preformed Vitamin A (retinol) is found in animal-based foods such as liver, dairy, and fish. Also prevalent in fortified grains
Carotenoids as provitamin A are found in darkly pigmented plant products such as spinach, broccoli, cantaloupe, carrots, and vegetable-beef/chicken soup.
All are also found in supplement form
Vitamin A: Biochemical Indicators Serum retinol and serum binding protein
Vitamin A Deficiency:Causes Absorption is enhanced by fat, and
diminished by diarrhea, intestinal infections, and infestations.
Deficiency is rare in developed nations, but common in developing countries
Vitamin A Deficiency:Consequences Most common condition is xerophthalmia
(irreversible drying of conjunctiva and cornea) Affects 3-10 million children/year Starts with night blindness, then continues into
conjuntival xerosis, Bitot’s spots, corneal xerosis, corneal ulceration, and scarring)
Decreased immune function/increased risk of infectious morbidity/mortality
No known deficiency effects from underconsumption of carotenoids.
Vitamin A Toxicity:Causes >=30,000 mcg/day for months-years is
chronic toxicity >= 150,000 mcg in single or short-term doses
is acute toxicity (less in children) Excludes beta-carotene
Vitamin A Toxicity:Consequences Acute Toxicity:
Effects are transient and include: Nausea Vomiting Headache Increased cerebrospinal fluid pressure Vertigo Blurred vision Loss of muscular coordination Bulging fontanel in infants
Chronic Toxicity: Less specific and more varied symptoms including:
Birth defects Liver abnormality Reduced bone mineral density CNS disorders Possible teratogenicity
Infants and children can also experience bone tenderness/pain, increased intracrancial pressure, desquamation, brittle nails, mouth fissures, alopecia, fever, headache, lethargy, irritability, weight loss, vomiting, and hepatomegaly.
Vitamin A DRI’s
Vitamin A DRI’s
Vitamin A DRI’s were based on assurance of adequate liver stores for age 19 – 70 YO For 1-18 YO, the adult EAR was extrapolated For 0-6 MO, average Vitamin A intake from human milk
was used For 7-12 MO, the infant EAR was extrapolated Pregnancy and lactation
Lack of evidence to determine DRI for provitamin A forms
UL was determined using risk of liver abnormalities or teratogenocity
RAE = Retinol Activity Equivalent
RAEs
Vitamin A Summary
Vitamin A is a fat-soluble vitamin important for immune function, growth, embryonic development, immunity, and vision.
Vitamin A can come as a preformed version (retinol), or as provitamin A (carotenoids).
Vitamin A DRIs are represented as Retinol Activity Equivalents (RAEs)
Vitamin A DRIs were determined using assurance of adequate liver stores
The RDA for adult males and females for Vitamin A is 900 mcg and 700 mcg, respectively.
Vitamin C
Also known as ascorbic acid Water-soluble Absorbed in intestine by an Na+ dependent
active transport (high concentrations use passive transport)
Also regulated by the kidneys (conservation and excretion)
Stored in pools throughout the body
Vitamin C
Source: http://biology.clc.uc.edu/courses/bio105/vitamin.htm
Vitamin C: Functions
Antioxidant (high reducing power) Scavenger of free radicals Cofactor for enzymes in the biosynthesis of
carnitine, collagen, NTs, and in vitro processes Reducing agent Scavenging of reactive oxidants in leukocytes,
lung mucosa, gastric mucosa Diminished lipid peroxidation
Vitamin C: Sources
Fruits and Vegetables such as citrus fruits, tomatoes, tomato juice, potatoes, brussel sprouts, cauliflower, strawberries, cabbage, spinach
Fortification Supplements 70-90% bioavailability (50% at high intakes)
Vitamin C: Biochemical Indicators Plasma and leukocyte ascorbic acid levels
Vitamin C Deficiency:Causes Rare in developed countries, although is
seen in diets that lack fruits and vegetables, older men, and lower socioeconomic status
Vitamin C Deficiency:Consequences Scurvy, which includes symptoms such as
follicular hyperkeratosis, petechiae, ecchymoses, coiled hairs, inflamed and bleeding gums, perifollicular hemorrhages, join effusions, arthralgia, impaired wound healing, dyspnea, edema, dry eyes and mouth, weakness, fatigue, depression
Infantile scurvy includes bone abnormalities, hemorrhagic symptoms, and anemia
Vitamin C Toxicity
Large doses (> 3,000 mg/day) Diarrhea and other GI disturbances
No other adverse effects
Vitamin C DRIs
Vitamin C DRIs
DRIs were determined by estimates of body pool or tissue Vitamin C levels that were considered adequate for antioxidant protection and minimal urinary loss Women have higher blood levels Smokers have a higher requirement
UL determined by occurrence of osmotic diarrhea and GI disturbances
Vitamin C Summary
Vitamin C is an important antioxidant. Vitamin C is water-soluble. Vitamin C is found in many fruits and vegetables,
especially citrus fruits. Vitamin C deficiency results in scurvy and its
associated symptoms. Extremely high amounts of more than 3,000 mg/day
of Vitamin C can result in diarrhea and GI disturbances
The RDA for adult males and females for Vitamin C is 90 mg/day and 75 mg/day, respectively.