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Re: [SANET-MG] there's gold in them thar spuds
Hi Dale,
Before I reply to your main query, I wish to mention that there are two
considerations. One vitamin A and beta carotene toxicity and the other
is vitamin A enhancement , such as that in golden rice, that is too low
to have any significant impact on the deficiency. There seems to be an
active superstition that a GM supplement that fills a small fraction
of the required impact is more than good enough for the poor. The
public relation activity should take care of all of their needs!
In the case of the golden potatoes it was indicated that the
requirement might be completely fulfilled. however, those same potatoes
might impact the normal western diet adversely. That remains to be seen.
The conversion of beta carotene to retinol (vitA) was suggested to be
around 2 carotene for one retinol in the potato paper , which indicated
that there is some variability among individuals in the conversion. That
disagrees with your comment that a "huge" amount of carotene was
converted to a little retinol, even though huge like squat is hard to
measure?
Turning to your main point the following paper showed vitamin A toxicity
related to a diet rich in pumpkin and some other beta carotene sources:
Vitamin A toxicity secondary to excessive intake of yellow-green
vegetables, liver and laver.
Nagai K, Hosaka H, Kubo S, Nakabayashi T, Amagasaki Y, Nakamura N.
Department of Internal Medicine, Saiseikai Yokohama-shi Nanbu Hospital,
Yokohama, Kanagawa, Japan.
J.Hepatol. 1999 Jul;31(1):142-8.
I will also list a number of other papers discussing the enhancing
effect of beta carotene on cancer in smokers and related topics:These
are articles that give you a good idiea of the problem:
Teratology. 1996 Aug;54(2):103-7.
Clinical teratology counseling and consultation report: high dose
beta-carotene use during early pregnancy.
Polifka JE, Dolan CR, Donlan MA, Friedman JM.
Fundam Appl Toxicol. 1997 Dec;40(2):163-74. Related Articles
beta-carotene: friend or foe?
Omaye ST, Krinsky NI, Kagan VE, Mayne ST, Liebler DC, Bidlack WR.
J Biol Chem. 2000 Jan 21;275(3):2003-8. Related Articles
Oxidative DNA damage by vitamin A and its derivative via superoxide
generation.
Murata M, Kawanishi S.
"Recent intervention studies revealed that beta-carotene supplement to
smokers resulted in a higher incidence of lung cancer"
Am J Clin Nutr. 1999 Jun;69(6):1071-85.
Alcohol, vitamin A, and beta-carotene: adverse interactions, including
hepatotoxicity and carcinogenicity.
Leo MA, Lieber CS.
Nature. 1999 Apr 29;398(6730):760-1.
Co-carcinogenic effect of beta-carotene.
Paolini M, Cantelli-Forti G, Perocco P, Pedulli GF, Abdel-Rahman SZ,
Legator MS.
Finally, you may think that carrots are harmless, but I have sen the
impact of carrot craving and over consumption. The skin gets yellow as
do the whites of the eyes and the effeect is accompanied by anemia. I am
not putting down carrots, but too much of a good thing may be harmful.
The main point is that genetic modification should be done with care.
Food crops have been around for at least 14,000 years and these crops
were selected from a mass of species toxic to man and other animals. GM
meddling may undo much of the careful screening and selection of our
ancestors.
hope this helps!
sincerely,joe
Dale Wilson wrote:
Joe,
I was simply pointing out that beta carotene (vitamin A precursor)
and vitamin D are associated with birth defects. Of these vitamin A
is most clearly associated with birth defects in humans.
I have repeatedly circulated those studies showing that beta carotene
ingestion has caused vitamin A poisoning in humans.
I have poked around in the literature but have missed that. Could you
re-send the reference? What is clear from the literature is that
carotene has a very wide margin of safety, much wider than actual
vitamin A.
However, consuming supplements and at the same time beta carotene
rich
veggies like pumpkin is probably unwise for women of child bearing
age and that advise has been given by others.
I think we agree that there is no reason to take supplements if one is
eating a diet that includes a generous amount of green and yellow
vegetables. Yet, across poorer countries, people are given potentially
dangerous once-a-year mega-dose supplements of Vitamins D and A,
because the population is so chronically deficient.
In the instance of the golden potatoes phytoene a precursor
of beta carotene and vitamin A, the authors expressed the fact that
there was no way ,at present, to tell as to how much beta carotene
would be produced in the potatoes in the field.
All this is highly theoretical at this point. When the gene is placed
in an actual variety, they will find out. You know as well as I do
that carrots are absolutely loaded eith B-carotene, far more than these
potatoes or rice ever will be. If those poor people would just eat
carrots, their vitamin A deficiency would be gone. I'll bet you are
not anti-carrot!
Alas, many cannot afford carrots. And while we might agree or disagree
about the socioeconomic determinants of this state, people are dying
for want of a little B-carotene.
Many public health advisors have warned pregnant women of consuming
vitamin A supplements and to be careful of excess beta carotene.
From what I have seen in the literature, dietary beta carotene is very,
very low risk for pregnant women (as opposed to actual Vitamin A), and
in fact, is abundant in what we would consider a normal, healthy diet
that includes lots of vegetables.
If over enthusiastic developers release patented crops that cause
birth defects in humans they will be liable for the damage I believe.
In this case, the conservative thing to do (the precautionary principle
if you will) is to somehow get more B-carotene into the diets of poor
people, rather than depending on risky emergency supplementation with
much more dangerous vitamin A pills. The modest amounts of B-carotene
that can be engineered into potatoes or rice, is only a partial
solution.
I am sure you were a whizz bang technician at Pioneer,
but to be an authority you seem to need to look at the literature of
science studies, please take that criticism to heart.
Okay. Let's slowly examine the literature on this subject.
Dale
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