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By
Dr. Joseph Mercola
with Rachael Droege
Vitamin A is an important nutrient yet there is much confusion
surrounding its appropriate form, dosage and source. Many
people do not receive enough of this nutrient, particularly
those in developing countries, however, many people are afraid
of taking too much due to the commonly heard warnings that
too much vitamin A is toxic and can result in birth defects,
liver abnormalities, and reduced bone mineral density, which
could result in osteoporosis.
Unfortunately, what is rarely addressed along with these
warnings is the TYPE of vitamin A. There is a big difference
between synthetic vitamin A and vitamin A from natural sources.
Most cases of vitamin A toxicity result from an excess intake
of synthetic vitamin A in supplements, NOT the natural form
of retinol (vitamin A) found in liver or cod liver oil.
In fact, vitamin A, an anti-infective vitamin, is useful
for many conditions including vision problems, poor thyroid
function, a weakened immune system, and fighting off infections,
especially those that involve mucous membranes as vitamin
A is used to form the cells lining the digestive, respiratory,
reproductive and urinary tracts and all tissue linings of
the body. It is also required for the digestion of protein,
lactation, reproduction, healthy skin and eyes, and the formation
of steroid hormones. Vitamin A deficiency can result in a
number of problems including night blindness, dry eyes, eye
infections and skin problems.
There are no plant sources of vitamin A (carrots and other
yellow/orange vegetables and dark-green leafy vegetables such
as spinach and lettuce contain beta-carotene, not vitamin
A); it is only present in animal products. If you follow my
newsletter then you’ll know that I recommend cod
liver oil as the best source of vitamin D (other than
the sun, of course), but what you may not know is that it
is also one of the best sources of vitamin A.
There is no need to worry about vitamin A toxicity if you
take it in cod liver oil, and there are several reasons for
this. First of all, as I mentioned earlier the main toxicity
that can result from vitamin A is due to SYNTHETIC vitamin
A, NOT the natural form found in cod liver oil.
Secondly, cod liver oil has vitamin D in it, and it is virtually
impossible to become toxic on vitamin A if you take it along
with vitamin D. As you can see in a study published in the
December
2003 American Journal of Clinical Nutrition, vitamin D
is associated with reduced vitamin A toxicity, and the vitamin
D appears to protect against retinal toxicity.
This study also found that the safe upper single dose of
retinol IN OIL seems to be 12,000 to 18,000 units of vitamin
A per kilogram of body weight. The cod
liver oil that I recommend has 1,000 to 1,250 units in
a one-teaspoon serving, which means that you will be way under
this limit if you follow my recommended dose (one teaspoon
for every 50 pounds of body weight per day).
Relying on plant foods containing beta-carotene as your sole
source of vitamin A is not a wise choice, and vitamin A deficiency
is a major concern for people who choose to have a strictly
vegetarian diet. Beta-carotene is the metabolic precursor
of vitamin A, which means that it must be converted into vitamin
A in the body. However, it takes bile salts, thyroid hormone
and dietary fat to facilitate this conversion, and even then
the conversion of beta-carotene into vitamin A is poor (it
takes about six units of beta-carotene to make one unit of
vitamin A).
Further, people with liver or gall bladder problems, hypothyroidism,
alcoholism (heavy alcohol intake can impair storage of vitamin
A in the liver), or diabetes, and infants, cannot adequately
convert beta-carotene to vitamin A, so it is especially important
for this large group of the population to consume animal sources
of vitamin A like cod liver oil.
If you are consuming a healthy diet, there is no need to
supplement with vitamin A. Some excellent sources of natural
and beneficial vitamin A include:
Including these foods in your diet should give you adequate
vitamin A with no need for supplementation and little to no
risk of overdosing. Vitamin A is a fat-soluble vitamin, which
means that it needs to be eaten with fat in order to be optimally
absorbed. One of the great things about natural foods is that
they almost always account for these types of conditions.
You’ll notice that all of the foods above also contain
fats, so the environment is automatically right for the vitamin
A to be utilized by your body.
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Vitamin
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The Vegetarian
Debate Continues: You Can't Get Vitamin A From Plants
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