of Vitamin A
The use of acne
medicines (i.e. Acutane) has led to birth defects and even death
(11) in children born to mothers using these compounds (6). This
has helped make the public more aware of the toxic properties of
In adults a
condition known as hypervitaminosis exhibits itself after
chronic ingestion of the vitamin in doses that are ten times the
RDA (10 mg RE).
vitamin A toxicity include:
bone and muscle
slowly reside as vitamin A intake levels are reduced. To date
the only side effect of excess beta-carotene has been yellowing
of the skin, most commonly in the fatty areas of the hands and
palms. The yellowing disappears as beta-carotene intake
decreases. This commonly ingested dietary precursor to vitamin A
has yet to exhibit any signs of toxicity even at levels as high
as 180 mg per day. Researchers believe that the presentation of
unbound retinol to the cell is a major factor in toxicity.
Excessive intakes of vitamin A saturate RBP and instead of
retinol being transferred bound to RBP, it is transferred to the
tissue via plasma lipoproteins. When retinol reaches the tissue
by a carrier other than RBP it is hypothesized that the retinol
is released and causes toxic side effects.
If you don't get enough vitamin A, you are more susceptible to
infectious diseases and vision problems.
If you get too much vitamin A, you can become sick. Large doses
of vitamin A can also cause birth defects. Acute vitamin A
poisoning usually occurs when an adult takes several hundred
thousand IU. Symptoms of chronic vitamin A poisoning may
occur in adults who regularly take more than 25,000 IU a day.
Babies and children are more sensitive and can become sick after
taking smaller doses of vitamin A or vitamin A-containing
products such as retinol (found in skin creams).
Increased amounts of beta-carotene can turn the color of skin to
yellow or orange. The skin color returns to normal once the
increased intake of beta-carotene is reduced.