Sunday, 19 June 2011

Zinc

My previous post on calcium led me into some interesting reading on the various vitamins and minerals required for optimal health. I say 'optimal health' but really I believe less and less there is such a concept, given the huge heterogeneity present among the human race and the myriad of environmental and genetic influences constantly tugging at our health and well-being. Probably a better way of describing it would be 'get-through-the-day health' which, whilst not being so catchy in title, is better reflective of our changing nutritional requirements dependent on so many different factors.

One particular area of interest that I came across relates to zinc.

I have to say that I have a new found appreciation for zinc after reading about its various biological uses. After iron, zinc is one of the most common metals used in various enzymatic reactions around the body. Thinking about going out for a few drinks on a Friday or Saturday night? Well make sure that you have packed your zinc, which is an important co-factor for alcohol dehydrogenase, the primary pathway for breaking down alcohol (God knows here in the UK, we need it). Zinc has also found some favour with helping some of us get over the common cold more quickly (bearing in mind there is more than one virus that can cause a cold). There are lots of other uses for zinc throughout the body and certainly I would recommend spending some time looking at them if you are so inclined.

When it comes to autism spectrum and related developmental conditions there are some interesting studies and ideas on zinc which are worthy of discussion. One of the earliest references to zinc and autism that I found was this one from 1978. In it the authors reported that plasma levels of zinc and a few other things were within normal ranges in autism, and that their results indicate that "..autism cannot simply be attributed to a disorder of zinc metabolism". I was wondering quite a bit about this last statement and the implied suggestion that autism was due to disordered zinc metabolism. Has autism ever been described in such a way, if so by who? There is also some suggestion that zinc might also show some involvement in cases of pica - the eating of non-edible material - a co-morbidity for various developmental conditions including autism. Evidence of pica being associated with low zinc levels in both the learning disability population and in the general pediatric population has been presented. I have yet to find anything in the research literature that explicitly links pica in autism as being related to zinc deficiency but there are some interesting personal and second-person accounts suggestive of a possible link. As with everything however, zinc may not be an entirely positive thing. A few papers have reported an excess of zinc as being present in autism. This paper for example, suggested that high levels of zinc in autism (measured by hair analysis and our old friend ICP Mass spectrometry) perhaps showed some connection with  low muscle tone. I am not in any way suggesting that zinc caused the hypotonia - low muscle tone (which is itself a feature of quite a few cases of autism) but the association is an interesting one.

Outside of core autism and perhaps moving into the realm of autism co-morbidities, there is also some interesting data on zinc and a few potentially relevant conditions. ADHD and zinc seems to have forged some connection. Studies like this one and this one have suggested that where low levels of zinc are presented, there may be some tie in to the presentation of certain symptoms such as inattention, anxiety and conduct problems.  Where supplementation has been assessed by clinical trial the results have also suggested some promise in ameliorating symptoms (although not universally and potentially also tied into other components of the supplement).

Inflammatory bowel disease (IBD) has also been associated with zinc. Several reports have correlated the presence of various IBDs and low levels of zinc, including in pediatric populations (see here). There is still quite a lot of speculation as to why such an association should be present, but certainly calprotectin, a marker of inflammation, may show some effect in the presence of zinc; as indeed, zinc has quite a role to play in normal immune function. Supplementation with zinc in cases of IBDs also seems to show some promising effects on various markers of disease and severity.

I am mindful that I have extolled the virtues of zinc in this post and paid only lip service to the more potentially negative effects, particularly the relationship with cadmium and its onwards toxicity and the possible interactions with various medications and other nutritional supplements. Going back to my original assertion of 'get-through-the-day health', I would perhaps forward the view that zinc, in the right amounts, plays a very important role in maintaining a healthy body.