No multivitamins exclude all the micronutrients I'm avoiding supplementing.
Well it all depends on the dose, doesn't it? I couldn't think of a single micronutrient I wouldn't take at all (after all, they are nutrients), but there are many I wouldn't take more than a RDAish dose of. The only exeption would be iron and copper, for which there is strong evidence of adverse effects even at normal dietary levels, so I try to generally limit my intake of them.
Of course, if one wants to bring up a case against supplementation, one can dig into PubMed and find a lot of studies supporting his position. Or the the exact opposite position (like that purported in the LEF Magazine articles
).
In the end, we either have to judge the evidence for every single micronutrient by ourselves, or rely on a trusted authority. As probably no one has the capacity to do this really comprehensively, I follow a mixed approach: I try to evaluate as many studies as I can by myself, but further rely on the reviews of such institutions as the Linus Pauling Insitute and the Harvard Medical School and to a lesser extend to the information given by semi-commercial authorities like Andrew Weil and the LEF, or by respected members of communities such as this.
In my opinion, some of the studies you have referenced give reason for real concern, others are highly speculative or stand against a larger contradictory body of evidence. The folic acid meta-analysis, for example, has ben superseded by larger and more recent analysis' which haven't shown an increased risk. Yet there lingers a shadow of concern on folic acid, so I would try to avoid it and take low-dose folate instead.
In general, I'm avoiding supplementing metals which catalyse ROS generation, and vitamins that act primarily as unregulated direct antioxidants. The endogenous antioxidant system is more potent and better regulated (to permit physiologically adequate levels of signalling ROS, while quenching deletorious spikes), and I do eat foods and take some non-vitamin supplements that appear to act primarily as indirect antioxidants, upregulating glutathione availability, SOD, catalase etc. I'll fully admit its a n=1 experiment, I'll let you know how it went in 60 years.
I'm the first to admit that there is some reason to that approach. However, I think that we are far away from fully understanding the health effects of hormesis and its optimum conditions in terms of ROS generation, especially considering very different individual health backgrounds and amounts of oxidative stress. The recent antioxidant meta-analysis may be a first and rather coarse step towars that understanding. We have to be careful, though, not to throw out the baby with the antioxidant bathwater.
Again, the 2005 meta-analysis of vitamin E, which I referenced, has shown a U-shaped curve with higher mortality at doses > 150 and slightly lower mortality at doses < 150. Considering the numbers you have posted - that 91% of all Americans don't achieve the EAR of vitamin E, this result becomes quite comprehensible. Therefore I think taking low-dose supplemental vitamin E, like most multivitamins provide, would provide benefit to most poeple, whereas high dose vitamin E may very well be dentrimental to health.
Multivitamins and most commonly consumed supplements don't have a great record on overall mortality. The notable exceptions appear to be D, magnesium, glucosamine-chondroitin (!), and calcium (despite mixed disease outcomes*). Long chain omega-3s (fish oil, algal DHA) likely helps too (particularly with cardiovascular risk), but studies on supplementation have been too inconsistent for statistical significance. *the American EAR for calcium is inflated due to dairy lobby influence (525 mg normalizes hip-fracture rates), and supplemental calcium appears to lower cancer (esp colon) while increasing CVD risk.
It's funny that of all things you exclude calcium. Have a look at these four recent studies (
http://www.ncbi.nlm....pubmed/23866097,
http://www.ncbi.nlm....pubmed/22626900,
http://www.ncbi.nlm....pubmed/23381719,
http://www.ncbi.nlm....pubmed/23403980) and you may reconsider your take on calcium.
If you think that the available literature on long chain omega-3s is inconsistent (which it is), than I wonder what you would call the literature on multivitamins. The data on omega-3s is neat and consistent compared with the completely messed-up way most epidemiological studies take record of multivitamins. Now what to do, when we have a host of widely inconsistent, low quality studies? We should watch out for at least a single well done, methodologically sound study with sufficient statistical power to draw meaningfull conclusions from that study alone. In this case, we do now have such a study. It is the multivitamin RCT arm of the Physicians' Health Study II. Here we have a large (n=14,641) and at the same time very homogenous population that (by its profession) is exceptionally health conscious and well nourished, physically active and largely abstinent from smoking and exessive alcohol use. Moreover, we have a unequalled medium follow-up of 11.2 years, in which the participants took the multivitamin formula vs placebo. The results: a
modest decrease in risk of cancer (HR: 0.92, P=0.04) and a
non-significant reduction in all-cause mortality risk (HR: 0.94, P=0.13) - despite that the
Centrum Silver formula used has been far from optimal, as it contained 4mg iron and 2mg copper.
If you add to that study the results of a
very well done epidemiological study, taking into account the "sick-user bias" which severely distorted previous epidemiological studies on supplements, and
this finding of increased telomere length in woman who took multivitamin supplements, I think we can make a pretty strong case for a comprehensive low to moderate dose multivitamin supplement.
Edited by timar, 07 November 2013 - 07:08 PM.
