You may well be aware at just how often nutritional advice seems to blow in the wind. And this week brought an example of this in the form of a study which, it is claimed, found a link between the eating of oily fish and an increased risk of diabetes. Not surprisingly, this has led to some recommending caution with regard to our consumption of oily fish, with a spokesperson for the British Dietetic Association recommending that we consume no more than one portion a week. But does it really make sense for us limit our intake of a food which, traditionally, has a very healthy reputation?
The research in question was published in the journal Diabetes Care looked at the relationship between pesticide residues known as ‘persistent organic pesticides’ (POPs) and diabetes risk. POPs include chemicals known as ‘organochlorines’ and ‘polychlorinated biphenyls’ (PCBs). Because pesticides can tend to lodge in fat, POP residues can be found quite plentifully in ‘oily’ varieties of fish (e.g. salmon, trout).
The Diabetes Care study found that higher blood levels of POP were associated with an increased risk of ‘insulin resistance’ ” itself believed to be a ‘warning sign’ of Type 2 diabetes. The link between POPs and insulin resistance was highest for those with bigger waist sizes (increased waist circumference is itself associated with an increased risk of insulin resistance and Type 2 diabetes). Previous research has found that exposure to pesticide residues was associated with an increased risk of Type 2 diabetes.
The suggestion here is that pesticide residues somehow act to promote insulin resistance and Type 2 diabetes.
The authors of the Diabetes Care study published this week have been at pains to point out that their research does not prove that pesticide residues actually cause insulin resistance. They have also called for further research into how these chemicals might promote biochemical disruption in the body. This all sounds like good sensible stuff to me.
While definitive research is yet to be done, it may indeed turn out to have biochemically disruptive and health-harming effects in the body. The precautionary principle dictates, I think, that the less of these chemicals we are exposed to, the better.
But does that mean we should eschew oily fish? After all, this foodstuff is rich in, among other things, so-called ‘omega-3 fats’ that have been linked with, among other things, a reduced risk of cardiovascular disease and seem also to have benefits for the brain.
In some quite recently published research in the Journal of the American Medical Association the pros and cons of fish-eating were weighed up. The authors of this study concluded that even when contamination is taken into account, eating fish seems to do more good than harm . In the ideal World all our food would be free from extraneous chemical contaminants. However, the totality of the evidence supports the idea that eating a piece of somewhat contaminated oily fish is better for us than not eating it at all.
1. Lee D-H, et al. Association Between Serum Concentrations of Persistent Organic Pollutants and Insulin Resistance Among Nondiabetic Adults. Diabetes Care 30:622-628, 2007