proof or get out. im not even gonna bother tearing that statement apart untill you show some proof.
You reminded me of this awesome book.
You Want Proof? I'll Give You ProofAnd some synthetic vitamins are dangerous in large doses (look at beta carotene, for instance).
I think that any form of beta carotene is harmful in excess. The vitamin companies' response to the beta carotene trial failures said that the synthetic was uniquely harmful because it was all-trans, while it occurs naturally as a mixture of cis and trans. "Buy our Betatene! It has the natural mix." But the body seems to efficiently convert cis to trans.
http://www.thorne.co...ext/5/6/530.pdfA group at Cornell University [PMID: 8694017, abstract below] gave three healthy adults a 1 mg (1666 IU) single dose of 99-percent cis beta-carotene labeled with a radioactive tracer (13C) and found over 95 percent of the cis isomers had been isomerized to trans beta-carotene or transformed into retinol prior to entering the bloodstream. Using calculations the authors admit “may be underestimates” they speculated that 14-52 percent of the cis beta-carotene had been isomerized to the all-trans form.
Am J Clin Nutr. 1996 Aug;64(2):177-83.
Evidence of cis-trans isomerization of 9-cis-beta-carotene during absorption in humans.
You CS, Parker RS, Goodman KJ, Swanson JE, Corso TN.
Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853, USA.
Absorption and metabolism of [13C]9-cis-beta-carotene ([13C]9c beta C) was studied in three subjects after a single oral dose. Subjects given 1.0 mg [13C]beta-carotene (mean: 99.4% 9-cis-beta-carotene, 0.6% all-trans-beta-carotene; dose A) had substantial concentrations of [13C]all-trans-beta-carotene ([13C]tr beta C) and [13C]all-trans retinol ([13C]retinol) but very low concentrations of [13C]cis-beta-carotene ([13C]cis beta C) in saponified plasma 5 h after dosing, as determined by HPLC and isotope-ratio mass spectrometry. There was no evidence of appreciable absorption of [13C]9-cis retinol. To determine the proportion of [13C]tr beta C and [13C]retinol derived from [13C]9c beta C, a second set of studies in the same subjects was performed with the same isomeric composition except with 13C labeling only in all-trans-beta-carotene (dose B). The results indicated that > 95% of plasma [13C]tr beta C and [13C]retinol observed after dose A was derived from [13C]9c beta C. The concentrations of [13C]tr beta C observed, in excess of that derived from the trace amounts of [13C]tr beta C in the dose, indicated that a significant proportion of the [13C]9c beta C dose was isomerized to [13C]tr beta C before entering the bloodstream. Although precise quantitative estimates of the extent of isomerization of 9-cis-beta-carotene could not be made, it is apparent that cis-trans isomerization of 9-cis-beta-carotene to all-trans-beta-carotene contributed to the near absence of postprandial plasma 9-cis-beta-carotene after its oral administration in humans. The observation of different ratios of beta-carotene to retinol between the two dosing protocols suggests that isomerization did not occur exclusively before uptake by the intestinal mucosa. These results indicate that isomerization of ingested 9-cis-beta-carotene before its secretion into the bloodstream limits the potential supply of 9-cis retinoids to tissues, and increases the vitamin A value of 9-cis-beta-carotene.
PMID: 8694017