Saturday, September 22, 2007

Yipe, Yoghurt

A couple of weeks ago I got it into my head that I ought to eat a small carton of zero fat yoghurt every day. I decided to mix it with fruit, usually mango from our mango tree, and consume it when I got home from work about 4.30pm. Intermittent pains and rumblings in my intestines followed but I didn't make any connection between this discomfort and my yoghurt consumption. Even worse was a chronic fatigue that seemed to be always with me. I was nodding off at work and crashing out when I got home. As usual, it was Desy who alerted me to the fact that maybe the yoghurt was causing the problems.

At first I was dismissive of the idea but then I accepted it after I returned to my normal self after not eating it anymore. I couldn't really understand why yoghurt had had that effect on me. A little Internet searching however, soon threw up an answer in the form of lactose intolerance. To digest lactose, you need an enzyme called lactase. Humans stop producing this enzyme about 4 or 5 years of age and thereafter don't easily tolerate milk or milk products in their diet. This is true of about 70% of the world's population, including most Asians. Due to a genetic mutation about 4,500 years BCE however, most Europeans still produce lactase into adulthood.

Even in Europeans however, the production of lactase falls off as they get older. It seems that zero fat Yoghurts are especially high in lactose and so my daily dose of yoghurt was putting my digestive system under continuous stress. There wasn't any mention made of fatigue as a symptom of lactose intolerance but that was certainly one of the effects it had on me. So I'm back to normal and wiser for having learned about the source of my problem.

It seems that lactose intolerance develops naturally in most animals shortly after weaning. In certain situations, it is genetically advantageous to maintain lactose tolerance into adulthood. For example, while most Chinese are lactose intolerant, the Mongol tribesmen on the border of China are not. These tribesmen are heavily reliant on horse milk. A similar thing seems to have happened with Europeans and cows milk. There is some evidence that the European genetic mutation originated in Sweden.

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