Unlike water-soluble vitamins that need regular replacement, the fat-soluble vitamins,
vitamins A, D, E, and K, are stored and persist for long periods of time in the
body’s liver and fat and are only slowly eliminated from the body. Diseases caused
by a lack of fat-soluble vitamins are unusual in the U.S., and very few people need
to supplement their diet with these vitamins.
Because they are not readily excreted in urine, excessive consumption of fat-soluble
vitamins generally poses a greater risk for toxicity than water-soluble vitamins.
Fat-soluble vitamins are not destroyed by cooking and eating a normal, well-balanced
diet will not lead to toxicity. However, supplements that contain mega doses
of vitamins A, D, E, and K may lead to toxicity and should be avoided. Rarely,
health problems decrease the absorption of fat, and in turn, decrease the absorption
of vitamins A, D, E, and K.
Vitamin A (retinol, retinoic acid) is a vitamin with antioxidant properties that is
important to support vision, growth, cell division, reproduction, and immunity. The
healthiest source of vitamin A is from plant-based foods that contain beta-carotene,
which the body converts to vitamin A. Beta-carotene is found in fruits and vegetables,
especially those that are orange or dark green in color. The retinol, retinal, and
retinoic acid forms of vitamin A are supplied primarily by foods of animal origin
such as dairy products, fish, and liver.
Vitamin A toxicity is unlikely when it is obtained from food. But excess vitamin
A from high potency multivitamin supplements can be toxic when consumed at a
level over the Tolerable Upper Intake Level (UL) for adults of 3,000 μg/day of preformed
vitamin A (also known as retinol). The Recommended Dietary Allowance
(RDA) for men and women is 900 and 700 μg retinol activity equivalents (RAE)/
Symptoms of vitamin A toxicity include dry, itchy skin, headache,
nausea, and loss of appetite. Signs of severe overuse over a short period of
time include dizziness and blurred vision. Vitamin A toxicity also can cause liver
disease, slowed growth, severe congenital disabilities, reduced bone strength, and
may increase the risk for hip fractures.
Beta-carotene is a carotenoid and called a provitamin A because the body converts it into vitamin A. Unlike preformed vitamin
A (retinol), carotenoids in food are safe. When taking a vitamin A supplement,
look for those containing provitamin A and avoid those with more than 2000 IU of
preformed vitamin A (retinol).
This blog presents opinions and ideas and is intended to provide helpful general information. I am not engaged in rendering advice or services to the individual reader. The ideas, procedures and suggestions in that are presented are not in any way a substitute for the advice and care of the reader’s own physician or other medical professional based on the reader’s own individual conditions, symptoms or concerns. If the reader needs personal medical, health, dietary, exercise or other assistance or advice the reader should consult a physician and/or other qualified health professionals. The author specifically disclaims all responsibility for any injury, damage or loss that the reader may incur as a direct or indirect consequence of following any directions or suggestions given in this blog or participating in any programs described in this blog or in the book, The Building Blocks of Health––How to Optimize Your Health with a Lifestyle Checklist (available in print or downloaded at Amazon, Apple, Barnes and Noble and elsewhere). Copyright 2021 by J. Joseph Speidel