Vitamin A toxicity

Vitamin A toxicity, hypervitaminosis A

1. Domina Petric, MD
Vitamin A toxicity

2. Introduction
•The hepatic storage of vitamin A tends to mitigate
against the development of intoxication due to
intakes in excess of physiological needs.
•Persistentlarge overdoses (more than 1000 times
thenutritionally required amount) can exceed the
capacity of the liver to store and catabolize and will
thusproduce intoxication.
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.
4/8/2018

3. Four aspects of vitamin A metabolism tend
to protect againsthypervitaminosis:
Relatively inefficient conversion of theprovitaminsA in the gut.
The unidirectional oxidation of the vitamin to aform (retinoic
acid) that is rapidly catabolizedand excreted.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

4. Four aspects of vitamin A metabolism tend
to protect againsthypervitaminosis:
The relative excess capacity of CRBP(II) to
bind retinol.
Accelerated vitamin A catabolism.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

5. Hypervitaminosis A
•HypervitaminosisArequires high exposures.
•It is manifestedafter single large doses:
>660,000 IU for adults, >330,000 IU for
children, orafter doses exceeding 100,000
IU/day have been takenfor several months.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

6. Children experiencing hypervitaminosisA
develop transient (one to two days) signs:
•Nausea
•Vomiting
•Signsdue to increased cerebrospinal fluid
pressure: headache, vertigo, blurred or
double vision
•Muscularincoordination
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

7. Chronic hypervitaminosis A
Occurs with recurrentexposures exceeding
12,500 IU in infants to 33,000 IUin adults.
It is manifestedmainly as changes in the
skin andmucous membranes.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

8. Chronic hypervitaminosis A
•Dry lips (cheilitis) is a common earlysign, often followed
by dryness and fragility ofthe nasal mucosa, leading to dry
eyes and conjunctivitis.
•Skin lesions include dryness, pruritis, erythema, scaling,
peeling of the palms and soles, hair loss (alopecia)
andnail fragility.
•Headache, nausea and vomiting (signs ofincreased
intracranial pressure) have also been reported.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

9. Cheilitis
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4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

10. Vitamin A and bones
HypervitaminosisA
can affect bone and
may increase risk for
bone fracture.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

11. Signs of hypervitaminosis A
General: muscle and
joint pain, headache.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

12. Signs of hypervitaminosis A
Skin: erythema,
desquamation, alopecia.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

13. Signs of hypervitaminosis A
Mucous membranes:
cheilitis, stomatitis,
conjunctivitis.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

14. Signs of hypervitaminosis A
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

15. Signs of hypervitaminosis A
Sceletal: thinning and
fracture of long bones.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

16. Embryotoxicpotentialof highlevels
of vitaminA
•Retinoidscan be toxic to maternally
exposedembryos.
•13-cis-retinoicacidis very effective in the treatment
of acne, but can cause severe disruption of cephalic
neuralcrest cell activity:birth defects characterized
by craniofacial, central nervous system,
cardiovascular and thymus malformations.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

17. Embryotoxicpotentialof highlevels
of vitaminA
The critical period for fetal exposure
to maternally derived retinoidsis the
time when organogenesis is occurring:
before many womensuspect they are
pregnant.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

18. Embryotoxicpotentialof highlevels
of vitaminA
•Fetal malformations of cranial–
neural crest origin have been
reported in cases of oral use of all
trans-retinoic acid in treating acne
vulgaris and ofregular prenatal
vitamin A supplements.
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

19. Carotenoid toxicity
β-carotene intakes of as much as
30 mg/day are without side effects other
than the accumulation of thecarotenoid
in the skin, with consequent yellowing of
the skin (carotenodermia).
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.

20. •Combs GF. The Vitamins. Fundamental Aspects in
Nutrition and Health. Elsevier Inc. 2008.
Literature
4/8/2018
Combs GF. The Vitamins. Fundamental Aspects
in Nutrition and Health. Elsevier Inc. 2008.