By Stephen Byrnes, PhD,
RNCP
This article is one part of a series
of articles, which is a revision of an older article that we had previously
posted on our site. You can find the original article here.
Additionally, please see the rebuttal
to this article, by Dr. Michael Janson.
Part 4 of 15 (Previous)
Myth #4: The body's needs
for vitamin A can be entirely obtained from plant foods.
Vitamin A, or retinol and its
associated esters, is only found in animal fats and organs like liver
(26). Plants do contain beta-carotene, a substance that the body can convert
into vitamin A if certain conditions are present (see below).
Beta-carotene, however, is
not vitamin A. It is typical for vegans and vegetarians (as well as most
popular nutrition writers) to say that plant foods like carrots and spinach
contain vitamin A and that beta-carotene is just as good as vitamin A.
These things are not true even though beta-carotene is an important nutritional
factor for humans.
The conversion from carotene
to vitamin A in the intestines can only take place in the presence of
bile salts. This means that fat must be eaten with the carotenes to stimulate
bile secretion. Additionally, infants and people with hypothyroidism,
gall bladder problems or diabetes (altogether, a significant portion of
the population) either cannot make the conversion, or do so very poorly.
Lastly, the body's conversion
from carotene to vitamin A is not very efficient: it takes roughly 6 units
of carotene to make one unit of vitamin A. What this means is that a sweet
potato (containing about 25,000 units of beta-carotene) will only convert
into about 4,000 units of vitamin A (assuming you ate it with fat, are
not diabetic, are not an infant, and do not have a thyroid or gall bladder
problem) [27].
Relying on plant sources for
vitamin A, then, is not a very wise idea. This provides yet another reason
to include animal foods and fats in our diets. Butter and full-fat dairy
foods, especially from pastured cows, are good vitamin A sources, as is
cod liver oil.
Vitamin A earned its name from
the fact that it was the first vitamin discovered. Researchers in the
1930s described vitamin A as the "anti-infective vitamin" as
it is intimately involved in the health of the mucous membranes and in
fighting off infections.
Since its discovery, vitamin
A has been shown to be pivotal in several bodily functions: formation
of "visual purple" which allows us to see partially in low light;
maintenance of healthy vision and proper eye function; repair and maintenance
of epithelial tissues, especially those of the skin and mucous membranes;
maintenance of the endocrine system, espeically the thyroid gland; proper
utilization of dietary proteins; and stimulation of the thymus gland,
a major part of the immune system.
Supplementation, then, of vitamin
A could be of great help to someone who is facing vision problems, poor
thyroid function, weakened immunity, and assorted infections, particularly
those of the respiratory and urinary tract (these areas are lined with
mucous membranes). When approaching supplementation, a couple of things
need to be kept in mind:
1. Supplements of beta-carotene
(or foods containing it such as orange and yellow plant foods) are NOT
the same as those with vitamin A.
2. Beta-carotene is the metabolic
precursor of vitamin A; it must be converted into real vitamin A in
the intestines along with the help of bile salts, thyroid hormone, and
dietary fat. Infants, and those with diabetes, alcoholism, hypothyroidism,
and/or liver or gall bladder problems cannot make this conversion.
3. Additionally, the body's
conversion of beta-carotene to active vitamin A is very poor: it takes
roughly 6 units of beta-carotene to make just one unit of vitamin A.
Be sure, then, that you pruchase supplements that very clearly state
that they are REAL vitamin A and not beta-carotene.
4. Consumers are often warned
that vitamin A can be toxic if taken to excess. Pregnant women are also
warned that too much vitamin A can cause birth defects. Such warnings
are overblown.
5. Though vitamin A can produce
toxicity symptoms if taken to excess, it takes a huge and massive amount
to generate them. There have been studies done of people who have taken
300,000 units of vitamin A a day for over a year with NO adverse effects.
6. One has little to fear
of overdosing on this nutrient. Additionally, the toxicity symptoms
of excess vitamin A disappear quickly once supplementation is stopped.Studies
done on pregnant women with vitamin A were actually done with an acne
medicine made from a synthetic derivative of synthetic vitamin A --
in other words, a drug, not real vitamin A.
Native peoples the world over
take special care to feed vitamin A-rich foods to pregnant women: liver,
fish roe, eggs, butter, and cream. One does not see birth defects in these
people. As far as the amount to take, this is a matter of debate.
Obviously, children need to
take less than adults. Also, the right amount for one person may not be
the same as another. Consulting with a clinical nutritionist or orthomolecular
physician would be a wise choice in determining the right amount for you.
A safe amount I've used with
my adult HIV/AIDS clients is 25,000 IU's a day. In case of respiratory
or urinary infections, I'll increase it to as much as 200,000 IU's a day
for 5-10 days (along with other substances needed by the body to oversome
the infection). Supplementing with vitamin A could be a wise choice for
those facing immune system weakness, in combination with a nutrient-dense
diet that eliminates refined sugars, vegetable oils, processed foods,
and drugs. (28).
As with vitamin D, Dr. Price
found that the diets of healthy primitive peoples supplied substantial
amounts of vitamin A, again emphasizing the great need humans have for
this nutrient in maintaining optimal health now and for future generations.
Please see the next
issue of the newsletter for our continuation of this article. To read
the rebuttal of the above article, please click here.
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