Vitamin A (Retinol)
Requirements:
- RDA:
5,000 I.U. for males
4,000 I.U. for females
5,000
I.U. for pregnancy
Daily Optimal Intake:
10,000 - 50,000 I.U. for males and
females
Supplement Forms:
- Palmitate is the synthetic form and water soluble. This may be
best for patients with fat absorption problems.
- Usually contains beta carotene also
Labs:
- Plasma retinol - 15 - 60 mcg. / dl.
Food Sources:
- Apricots 10 med. halves (6,000 I.U.)
- Beef liver 3 oz. (45,000 I.U.)
- Broccoli 1 med. stalk (4,500 I.U.)
- Cantaloupe 1/2 med. (9,000 I.U.)
- Carrot raw 1 med. (11,000 I.U.)
- Chicken liver 3 oz. (27,000 I.U.)
- Mango 1 med. (8,000 I.U.)
- Papaya 1 med. (6,100 I.U.)
- Pumpkin cooked 1/2 cup (8,000 I.U.)
- Pork liver 3 oz. (12,000 I.U.)
- Spinach 1/2 cup (7,3000 I.U.)
- Sweet potato 1 med. (12,000 I.U.)
- Winter squash 1/2 cup (4,300 I.U.)
Signs and Symptoms of Deficiency:
- Bitot's spots--->xerosis
conjunctiva--->xeropthalmia
- Diarrhea
- Dry eyes
- Follicular hyperkeratosis - common areas: anterior thighs and
posterior arms
- Keratinization
- Loss of bone
- Loss of both taste and smell
- Loss of tooth enamel
- Night blindness
- Opacity
- Reduced immunity
- Respiratory infections
- Sloughing of epithelial cells of cornea
Causes of Deficiency:
- Absorption problems
- Deficiency of protein or zinc can reduce the amount of vitamin
A released from the liver
- Interference with conversion of beta carotene to retinol
- Low intake
- Vitamin A storage problems
Adverse Reactions and Toxicity:
- 100,000 - 200,000 I.U. for 6-8 months may show signs of
toxicity:
All these signs and symptoms are reversible when vitamin A is
stopped
Alopecia
Bone pain
Brittle nails
Cheilosis
Drowsiness
Dry scaly skin
Fatigue
Headaches
Hepatosplenomegaly
Irritability
Muscle incoordination
Vertigo
Visual disturbances
Vomiting
- Early pregnancy - >50,000 I.U. may increase risk of birth
defects
- Palmitate, the synthetic form, is most toxic
- Patients with liver dysfunctions, i.e. from alcohol, drugs,
hepatic diseases, elderly, protein calorie malnutrition, have
increased susceptibility to vitamin A toxicity
Drug/Nutrient Interaction:
- Promotes healing suppressed by supraphysiologic doses of
corticosteroids
- Isotreninoin and vitamin A together can have a toxic accumulate effect
- Mineral oil long term can cause fat soluble vitamin deficiency, including vitamon A
- Cholestyramine causes malabsorption of vitamin A
- Oral contraceptives increase plasma vitamin A levels
- Neomycin decreases vitamin A absorption
- Colestipol decreases vitamin A absorption
Biochemical Functions:
- Immunity (vitamin A is necessary for maintaining the integrity
of the mucus membranes)
- Necessary for differentiation of basal cells into mucus
epithelial cells
- Necessary for growth and development of enamel forming
epithelial cells
- Necessary for growth and development of skeletal tissues
- Necessary for growth and development of soft tissues
- Necessary for humoral and cell-mediated immunity
- Necessary for normal reproduction and lactation
- Retinyl esters from the diet are converted to retinal (11 cis
isomer) in the eye. Retinal is then combined with the protein
opsin to form rhodopsin in the rods of the retina and iodopsin in
the cones.
- Steroid hormone synthesis and cell differentiation
Clinical Indications:
Copyright 1998 - 2008 by L. Vicky Crouse, ND and James S. Reiley, ND. All rights reserved (ISSN 1527-0661).