10 replies to this topic

[woly]

Fat Transforms Vitamin C From 'Good Cop' Into 'Bad Cop'

Science Daily - Fat in the stomach may cause vitamin C to promote,
rather than prevent, the formation of certain cancer causing
chemicals, reveals research published ahead of print in the journal
Gut.

The researchers analysed the impact of both fat (lipid) and vitamin C
(ascorbic acid) on nitrite chemistry in the upper (proximal) stomach,
which is especially vulnerable to pre-cancerous changes and tumour
growth.

Nitrites, which are present in human saliva, and in certain preserved
foodstuffs, may be converted to cancer causing compounds called
nitrosamines. Nitrosamines are formed in acidic conditions, such as
those afforded by stomach acid, but vitamin C inhibits their
formation, by converting nitrite to nitric oxide.

The researchers replicated the chemical conditions of the proximal
stomach and measured the formation of nitrosamines, oxygen, and nitric
oxide.

Without fat, vitamin C curbed the levels of two nitrosamines by a
factor of between five and 1000. And it completely eliminated the
production of the other two.

But when 10% fat was added, vitamin C actually boosted the production
of nitrosamines between 8 and 140-fold. Fat remains in the proximal
stomach for some time after a meal and also makes up a substantial
amount of the cells lining the stomach, say the authors.

Nitric oxide is formed when vitamin C reacts with nitrite in acid.
However, the nitric oxide can diffuse into fat and then react with
oxygen to form nitrosoamine generating chemicals.

The findings may be relevant to the recent observations that vitamin C
supplements fail to reduce cancer risk, say the authors.

Reference: Fat transforms ascorbic acid from inhibiting to promoting
acid-catlysed N-nitrosation Online First Gut 2007; doi: 10.1136/gut.
2007.12857

Note: This story has been adapted from a news release issued by BMJ
Specialty Journals.

will this change anyones vitamin c supplementation routine? maybe sublingual vitamin c is better?

[scottl]

"Nitrites, which are present in human saliva, and in certain preserved
foodstuffs, "

How about avoiding nitrites?

[Grail]

"Nitrites, which are present in human saliva, and in certain preserved
foodstuffs, "

How about avoiding nitrites?

Have you ever tried to not swallow your saliva? (it's messy...) [tung]

[darwinsdog]

Reminds me of one of Linus Pauling's few failings in scientific thought - the massive doses of vitamin c he took, after all, had little effect in preventing the prostate cancer that killed him.

Also, in response to the point above, nitrites come from nitrates processed by the body . . . spend few minutes flipping through a high school bio textbook and look up the "nitrogen cycle" to see how easy it would be to eat a nitrate-free diet (all you would have to do is avoid anything that grows in the earth). And after achieving this feat you'd die pretty quickly because nitrites are pretty important for a whole mess of processes in your body.

[brainengineer]

The thing you need to remember with Pauling though is that he died in his 90's, and I believe is father died in his 30's and his mother in her 40's. I would say living longer than both of your parents combined is a pretty good trick...

--
BrainEngineer

[scottl]

Heh. Serves me right for not reading the whole abstract, and forgetting the nitrate/nitrite thing (I assure you I've had more than my share of basic science courses)

The fact remains that if one reads an abstract showing that some supplement might be helpful we would not all run out and start downing the stuff (least I hope we would not). We would want to know that the study had been confirmed, was done by some unbiased people, and made sense. On the other hand I notice that people react very differently to even one abstract showing something might be harmful. This might be reasonable dependign the context e.g. taking one supps with little research on it, but makes less sense in the context of a vitamin which the body needs. The risk to benefit ratio is key. In any case there is a large body of evidence both research (search mind and muscle.net forum) and clinical (my experience and others) showing that there is good reason to take vitamin C in doses above the RDA. So the risk benefit of taking vitamin C is still heavily weighted towards taking it IMHO. One could look into sublingual as woly asked, but I'm not sure it is worth the bother.

Edited by scottl, 06 September 2007 - 02:54 PM.

[chipdouglas]

"Nitrites, which are present in human saliva, and in certain preserved
foodstuffs, "

How about avoiding nitrites?

I think it'd be relatively easy to avoid them indeed.

[chipdouglas]

Reminds me of one of Linus Pauling's few failings in scientific thought - the massive doses of vitamin c he took, after all, had little effect in preventing the prostate cancer that killed him.

Also, in response to the point above, nitrites come from nitrates processed by the body . . . spend few minutes flipping through a high school bio textbook and look up the "nitrogen cycle" to see how easy it would be to eat a nitrate-free diet (all you would have to do is avoid anything that grows in the earth).  And after achieving this feat you'd die pretty quickly because nitrites are pretty important for a whole mess of processes in your body.

Um, I wasn't aware of that, or at least didn't recall that--this means I take back my word that it would be easy to avoid nitrites in the first place.

[chipdouglas]

The thing you need to remember with Pauling though is that he died in his 90's, and I believe is father died in his 30's and his mother in her 40's.  I would say living longer than both of your parents combined is a pretty good trick...

--
BrainEngineer

Very good point indeed.

[chipdouglas]

Heh.  Serves me right for not reading the whole abstract, and forgetting the nitrate/nitrite thing (I assure you I've had more than my share of basic science courses)

The fact remains that if one read an abstract showing that some supplement might be helpful we would not all run out and start downing the stuff (least I hope we would not).  We would want to know that the study had been confirmed, was done by some unbiased people, and made sense. On the other hand I notice that people react very differently to even one abstract showing something might be harmful.  In any case vitamin C is a vitamin which means that the body needs it.  In addition there is a large body of evidence both research (search mind and muscle.net forum) and clinical (my experience and others) showing that there is good reason to take vitamin C in doses above the RDA.  So the risk benefit of taking vitamin C is still heavily weighted towards taking it IMHO.  One could look into sublingual as woly asked, but I'm not sure it is worth the bother.

You're right, most of the time when one negative study out of a bunch of positive evidence, often we (myself included) tend to suddenly seriously reconsider the taking of that particular supplement.

The website of Dr. Sendfor Levy, if some have browsed has a number of studies posted on the benefits of various vitamins, minerals, lifestyle etc..on various disease risk, such CHD and cancer. It's very interesting.

I do believe in taking certain supplements, no doubt, but one has to know a heck of a lot and keep abreast on new developments, just as in any other fields out there.

I keep thinking that if supplements (the ones with good science behind) were that bad, Paul & Kitty Wakfer would long be dead or very sick--after all they have the most extensive supplement regimen that I've seen. I've often wondered about the consequence of taking all of those together--my point is that synergism we know is sometimes bent the right way, but I'd imagine the reverse can happen too, can't it ?

That being said I respect Paul, as he knows far more than I on this topic.

I'm here to learn Scottl, and your opinion to me and others is very important. I'm always eager to learn.

[krillin]

Here's some results from actual people, not beakers.

Dietary nitrosodimethylamine (NDMA) has no effect on cancer risk.

During the second half of the last century, reductions in the use of nitrates and nitrites for curing meat and the modifications of malting techniques in the brewing industry have resulted in significant reductions in the levels of NDMA in foods. Therefore, it may be possible that current NDMA exposure in our population is below the biological level required to increase the risk of cancer

The limiting reagent for endogenous formation of nitroso compounds (ENOC) appears to me to be heme, not nitric oxide, nitrite, and/or nitrate. The ENOC vs meat iron graph is as linear as you can expect in a biology paper and shows no sign of plateauing at high iron intakes.

ENOC increases cancer risk, but only in those with low plasma vitamin C AND H. pylori infection.

Thus, vitamin C is good for you, and it's heme and H. pylori that we need to worry about.

Edit: That ENOC vs meat iron graph is a line graph, not an xy graph. Furthermore, it doesn't look like the y-intercept is zero. So heme is probably just the most important factor in ENOC, not the only important factor.

Edited by krillin, 06 September 2007 - 09:40 PM.