Would you like to eat cod every day for four weeks? No beef but cod. No poultry but cod. No veal but cod. No milk and no cheese but cod. No breakfast eggs but cod. I would like to see your face at the end of the four weeks. I would like to ask you if you know this Monty Python sketch «Spam, spam, spam... ».
Exactly this sort of diet has been tested in a diabetes trial: Nineteen persons suffering from insulin resistance, a stage of pre-diabetes, have been divided in two groups. One group ate the cod diet for four weeks, the other group ate lean beef, pork, veal, eggs, milk and milk products. Both diets were designed to differ only in protein source but not in the amount of total protein, saturated and unsaturated fats. After four weeks, both groups switched to the other diet for another four weeks. In both periods, the reaction to insulin has been monitored in all persons. During the cod diet period, this reaction (sensitivity) has been better than in the control period. The study authors conclude: «Dietary cod protein improves insulin sensitivity in insulin-resistant individuals, and thus could contribute to prevent type 2 diabetes by reducing the metabolic complications related to insulin resistance.»
I have a problem with such diet trials. They always have to be extreme in order to get a statistical significance. Yes, cod will reduce the danger of diabetes if you eat cod and no other animal protein every day. But what if you decide, like me, that diets suck and that cod is fine, from time to time? Will it still be helpful against diabetes? I guess it still would, but I guess also that this contribution would be so tiny that it would no longer be detectable in a trial.
There is more than diabetes ...
All the same I see some value in such studies. The reason is simple. Diabetes is not the only disease that must be prevented. There are hundreds of other diseases, and against some of them cod may also be beneficial. Let me guess that against six more diseases a preventive cod effect of similar size may be found. If you add these effects, you may get a notable overall advantage with one or two cod servings a week.
... and there is more than cod
A second reason may be even more important. Diet studies are undertaken with dozens of food components. You find studies on the preventive effect of apples, garlic, milk, cheese, strawberries, chocolate, coffee, green tea, black tea, wine, nuts, fish oil, olive oil, whole grain, mineral water - if I would dig my memory and do some searches, I could cite many more here.
My advice is simple. Most important is what you like. But you may not know all foods that you will possibly enjoy. If you never eat cod and find a study that favours cod, just take it as a hint. No cod diet, beware. But give it a try and see if you like it. I guess that there is also a placebo effect in food: If you know it does good and if you like it, you will enjoy it even more.
Photo credit: flickr.com/photos/ulteriorepicure/119369217/