It is also surprising how little of knowledgeable people are here, regarding this very important topic, perhaps these metabolic pathways are just too complicated for Imminst
Or perhaps, just perhaps, people here are actually knowledgeable enough to know about such fundamental issues as
dose-response relationships and therefore don't waste their time with such exaggerated concerns?
I agree with everything niner wrote in his response. Moreover, I think the whole "natural" (good) vs. "synthetic" (evil) dichotomy has been blown way out of any evidence-based proportion by certain supplement companies, who are using it as a sales pitch for their "all-natural mixed tocopherol and tocotrienol" supplements.
The first thing to note is that as of yet we just don't know whether the observed ill-effects of high-dose alpha-tocopherol supplementation is due to to the fact that those trials used isolated alpha-tocopherol, or just because high doses of vitamin E (in whatever form) interfere with hormesis. There are good arguments and some animal studies to support both hypothesis, but there is a complete lack of RCTs done with mixed tocopherols, so we have
no positive evidence whatsoever for the safety of mixed tocopherols compared to isolated alpha-tocopherol.
Second, a
dose-response meta-analysis of RCTs with alpha-tocopherol found that while high doses (>=400 IU) were associated with increased all-cause mortality, doses below 150 IU were actually associated with a
slightly decreased risk. The
Centrum multivitamin used in the PHSII, which significantly reduced
cancer risk (HR: 0.92, P=0.04) and showed a trend towards decreased
all-cause mortality (HR: 0.94, P=0.13) notably contained 45 IU all-rac-alpha-tocopherol. Given the findings from those studies I see absolutely no reason to avoid low-dose alpha-tocopherol, particularly not the doses used as an antioxidant in fish oil supplements (i.e. 5-10 IU/g).
Regarding tocotrienols: they do indeed have some interesting properties but it seems ridiculous to suggest that they are an essential part of a "natural" vitamin E mixture. There are, in fact, very few dietary sources of tocotrienols, the most significant ones being palm fruit and rice bran, minor amounts are found in oat and barley. Any dietary pattern lacking red palm oil or brown rice, or large amounts of whole grain cereals, is probably completely devoid of tocotrienols (save some trace amounts). Note that there are equally large variations in the ratios of tocopherols between different dietary patterns. Ironically, the SAD with its fried, vegetable-oil-ladden junk-food has a very low alpha-to-gamma-tocopherol ratio, because soy and corn oil happen to be excellent sources of gamma-tocopherol, while many healthy whole foods (e.g. most nuts) provide predominantly alpha-tocopherol.
Edited by timar, 24 March 2014 - 10:57 AM.
