Tuesday, October 11, 2011

Iowa Study and why it shows no benefit in supplementation

 The Archives of Internal Medicine has just published a paper in which the authors look at the Iowa Women's study and analysis the results with respect to supplementation. The conclusion to this analysis was:
In older women, several commonly used dietary vitamin and mineral supplements may be associated with increased total mortality risk; this association is strongest with supplemental iron. In contrast to the findings of many studies, calcium is associated with decreased risk   
As the media doesn't thoughtfully critic such articles it is highly likely that you will seen in the health section of your media headlines that scream "supplementation increases risk of death in women" or other such sensationalist, emotion creating bylines.

So lets dig a bit deeper and see if this conclusion is valid. Some background. The Iowa study was a massive study which studied 41 836 post menopausal women. This study was started in 1986 and had five follow ups over the next two decades (last follow up was 2004). The initial and five follow ups consisted of quite extensive questionnaires around lifestyle. Therefore this data gets "mined" regularly by scientists who are looking for impact of a behavior on mortality risk.

So know we know a bit about the study, why do I think that the conclusion "supplement increase mortality" isn't a valid conclusion?

[I also must confess at this point I haven't read the whole article, just the abstract. I am not motivated to purchase said article at US$30, just to more robustly critic it. I would much prefer to put this into my organic orchard that I am setting up. However if you want a more detailed analysis of the paper feel free to purchase a copy and send it to me!]  

The following reasons leap out at me:
  • Three data points. The supplementation question was asked in 1986, 1997 and 2004. Even though the Iowa study sounds impressive, which to some degree it is, the supplementation question has approximately a ten year interval. What this means is that there are errors due to peoples memory and accuracy of reporting. For instance can you remember exactly what supplements you were taking five years ago? I can tell you what multi I took, but couldn't tell you anything else even though I now I took more than just a multi. I am rather brand loyal, but wonder if the "average" person like my mum, who is post menopausal she has taken at least three different general supplements in the last 6 years. Therefore you can see how errors in studies such as this creep in. Know due to the studies size errors such as these may "average out" so that data may be trustworthy.  
  • Take them as sick. I got interested in various supplements as I had health issues. There must be a section of society, like me and my mum, who started to take supplements as their health was no longer optimal. I wonder if this effected the results. Being elderly something goes wrong, they try some supplements. These might help, might not, but soon they pass away. Therefore supplementation could be correlated with trying to get better once ill (which is harder to do, better to take supplementation preventativly, instead of re-actively, to stop body getting to the point were clinical symptoms are detected)      
  • Self reporting. I take my vitamins every day, day in, day out. However many people who I have sold them to, or know take them (including my wonderful wife who I berate regularly for not taking them to schedule) don't religiously take them. Therefore if you are supplementing say once every few days, this is going to be different from twice daily.    
  • Differences in nutrient levels. You need high enough values of a nutrient to make a difference. An example off the top of my head is vitamin C. For shortening the length of cold you need to be taking at least 1 000 mg (I think) daily before you get the cold for it to have a shortened infection time. A lot of studies in vitamin C, don't give a high enough dose to be significant ie they look at supplementing 60 mg. At this level it isn't going to make a big difference in your health. The same goes for other vitamins and some minerals. Therefore to ask "are you taking zinc?" is very difference from "are you taking 5 mg or 50 mg of zinc?" You cannot group both zinc takers as being the same, yet this study does so.  
  • No break down of bio-availability. Classic issue. For those of you who have read my book will know that I give a couple of examples of this. Copper for instance is often not in multi's. When it is it is often in a bio unavailable form as a copper oxide. Therefore if you take copper supplement (which was one of the mineral supplements asked about) is it one that you can absorb? There is differences in bio available of nearly all minerals and some vitamins. The bio-available wasn't studied the data and hence conclusions will be suspect.        
  • Break down of individual supplements. Saved the best to last. This is a MASSIVE concept. Let me give you an example. For some time I took a zinc only supplement to help with depression. I found this helpful in my journey to wellness. However I would never every recommend zinc to someone with depression. Why? A high quality multi is the first thing to take for any health improvement. The biochemistry for serotonin/melatonin creation is complex. Sure zinc is part of the process but first you need a high quality multi to cover the bases, so to speak, before increasing specific nutrients. Therefore without a high value multi there is no point is recommending zinc to people with depression. Now when a media article comes out "zinc helps depression"  everyone runs down to the supermarket/health food shop, buys zinc. For the majority of people it doesn't really help..... from memory there is about 8 essential minerals/vitamins/ nutrients in serotonin production. So have about 1 in 8 odds of zinc helping. But anyone who is low on zinc is likely to be low in other minerals, so any improvement would be small compared to improvement with high nutrient. So breaking down supplements to individual minerals / vitamins defeats the purpose    
If you have further questions, feel free to ask in the comments.

Hat tip: Keith Lightfoot Hardwick Enterprises for the heads up

No comments:

Post a Comment