Re: Benefit of Higher doses of folic acid is limited

[Guest guest]

Hi folks:

This is not the only possible problem with larger doses of folic acid. The relationship between folic acid and vitamin B12 seems to be quite complicated. But 'excessive' intakes of folate can cause problems with vitamin B12, as is discussed in the following article:

http://www.medicalnewstoday.com/articles/92272.php

Now, of course, in many countries we are being subliminally dosed with folic acid by government edict.

In general, for the vast majority of micronutrients, it is probably not a good idea to supplement any of them in 'large' amounts with one's eyes shut. IMO, it may be a better idea, in most cases, to supplement so that total intake comes just up to the RDA.

Perhaps vitamin D is an exception to this general rule. It is the only micronutrient I take in what might be regarded as a 'large' amount, for the reasons that have been discussed here at some length in the past.

Rodney.

>> Higher doses of folic acid (vitamin B9) greater than 1 mg (U.S. daily value 0,4 mg) may not be usefull after a new study in the Proceedings of the National Academy of Science because the human liver can´t procese it in greater amounts in the form how it is used in the body and the surplus of the folic acid can be found unprocesed in the blood and in the urine > > http://www.pnas.org/content/early/2009/08/21/0902072106> > (complete study can be downloded there)> > Published online before print August 24, 2009, doi: 10.1073/pnas.0902072106 > > > The extremely slow and variable activity of dihydrofolate reductase in human liver and its implications for high folic acid intake> > 1. W. ,1 and> 2. June E. Ayling,1,2> > + Author Affiliations> > 1.> Department of Pharmacology, University of South Alabama, 307 North University Boulevard, Mobile, AL 36688> > 1.> > & #8629;1S.W.B. and J.E.A. contributed equally to this work.> 2.> > Edited by Bruce N. Ames, University of California, Berkeley, CA, and approved July 22, 2009 (received for review > > February 25, 2009)> > Abstract> > Numerous clinical trials using folic acid for prevention of cardiovascular disease, stroke, cognitive decline, and neural > tube defects have been completed or are underway. Yet, all functions of folate are performed by tetrahydrofolate and its one-carbon derivatives. Folic acid is a synthetic oxidized form not significantly found in fresh natural foods; to be used > it must be converted to tetrahydrofolate by dihydrofolate reductase (DHFR). Increasing evidence suggests that this process > may be slow in humans. Here we show, using a sensitive assay we developed, that the reduction of folic acid by DHFR per gram > of human liver (n = 6) obtained from organ donors or directly from surgery is, on average, less than 2% of that in rat liver > at physiological pH. Moreover, in contrast to rats, there was almost a 5-fold variation of DHFR activity among the human samples. This limited ability to activate the synthetic vitamer raises issues about clinical trials using high levels of folic acid. The extremely low rate of conversion of folic acid suggests that the benefit of its use in high doses will be limited by saturation of DHFR, especially in individuals possessing lower than average activity. These results are also consistent with the reports of unmetabolized folic acid in plasma and urine.>

[Guest guest]

Hi folks:

And this is interesting too:

http://grande.nal.usda.gov/ibids/index.php?mode2=detail & origin=ibids_references & therow=411129

"....... Hence, folate deficiency does not appear to induce a secondary B12 malabsorption in the absence of another etiologic factors ........"

But folate excess DOES, it seems.

Rodney.

-- In , "perspect1111" <perspect1111@...> wrote:>> > Hi folks:> > This is not the only possible problem with larger doses of folic acid. > The relationship between folic acid and vitamin B12 seems to be quite> complicated. But 'excessive' intakes of folate can cause problems with> vitamin B12, as is discussed in the following article:> > http://www.medicalnewstoday.com/articles/92272.php> <http://www.medicalnewstoday.com/articles/92272.php>> > Now, of course, in many countries we are being subliminally dosed with> folic acid by government edict.> > In general, for the vast majority of micronutrients, it is probably not> a good idea to supplement any of them in 'large' amounts with one's eyes> shut. IMO, it may be a better idea, in most cases, to supplement so> that total intake comes just up to the RDA.> > Perhaps vitamin D is an exception to this general rule. It is the only> micronutrient I take in what might be regarded as a 'large' amount, for> the reasons that have been discussed here at some length in the past.> > Rodney.> > > > > > > > > > >> > Higher doses of folic acid (vitamin B9) greater than 1 mg (U.S. daily> value 0,4 mg) may not be usefull after a new study in the Proceedings of> the National Academy of Science because the human liver can´t procese> it in greater amounts in the form how it is used in the body and the> surplus of the folic acid can be found unprocesed in the blood and in> the urine> >> > http://www.pnas.org/content/early/2009/08/21/0902072106> >> > (complete study can be downloded there)> >> > Published online before print August 24, 2009, doi:> 10.1073/pnas.0902072106> >> >> > The extremely slow and variable activity of dihydrofolate reductase in> human liver and its implications for high folic acid intake> >> > 1. W. ,1 and> > 2. June E. Ayling,1,2> >> > + Author Affiliations> >> > 1.> > Department of Pharmacology, University of South Alabama, 307 North> University Boulevard, Mobile, AL 36688> >> > 1.> >> > & #8629;1S.W.B. and J.E.A. contributed equally to this work.> > 2.> >> > Edited by Bruce N. Ames, University of California, Berkeley, CA, and> approved July 22, 2009 (received for review> >> > February 25, 2009)> >> > Abstract> >> > Numerous clinical trials using folic acid for prevention of> cardiovascular disease, stroke, cognitive decline, and neural> > tube defects have been completed or are underway. Yet, all functions> of folate are performed by tetrahydrofolate and its one-carbon> derivatives. Folic acid is a synthetic oxidized form not significantly> found in fresh natural foods; to be used> > it must be converted to tetrahydrofolate by dihydrofolate reductase> (DHFR). Increasing evidence suggests that this process> > may be slow in humans. Here we show, using a sensitive assay we> developed, that the reduction of folic acid by DHFR per gram> > of human liver (n = 6) obtained from organ donors or directly from> surgery is, on average, less than 2% of that in rat liver> > at physiological pH. Moreover, in contrast to rats, there was almost a> 5-fold variation of DHFR activity among the human samples. This limited> ability to activate the synthetic vitamer raises issues about clinical> trials using high levels of folic acid. The extremely low rate of> conversion of folic acid suggests that the benefit of its use in high> doses will be limited by saturation of DHFR, especially in individuals> possessing lower than average activity. These results are also> consistent with the reports of unmetabolized folic acid in plasma and> urine.> >>