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More evolution screw-ups - Arvind Narayanan's journal [entries|archive|friends|userinfo]

More evolution screw-ups [Jan. 30th, 2007|06:48 am]
Arvind Narayanan
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I've had a salt craving problem for a long time. I can't remember exactly how long, but definitely more than five years. It was never serious enough to make me seek medical attention, but it kind of bothered me; I was worried about hypertension in the distant, nebulous future that no one likes to think about. The craving got worse after I moved to America. The whole thing made no sense at all -- the taste of salt comes from sodium, and in our sodium-saturated food environment it is inconceivable that anyone could have a deficiency of it.

Then, about a week ago, the craving virtually disappeared. Pleasantly surprised, I tried to figure out what I'd been doing differently in the week before that. With a flash of insight, it all fell into place.

Our ancestors, both primate and otherwise, got their salt from salt licks. In addition to sodium, these also contain trace minerals -- calcium, iron, phosphorus and zinc, according to wikipedia. Instead of learning to taste these individually, and develop specific deficiency-cravings for each, evolution took a short-cut because these were usually found together in nature: we only taste sodium, and crave it in response to a deficiency of any trace mineral. Indeed, the thing I'd been doing differently was taking multivitamins regularly, which contains ample amounts of all the above trace minerals and many more.

[User Picture]From: paper_crystals
2007-01-30 04:00 pm (UTC)
When I went to boarding college I used to crave starch to the point where I literally couldn't do my homework if I didn't have it. The problem was I was in a rural college that served three discrete meals a day without much snacking in between--or at least high starch content in the snacking. So I learned to keep peanut butter and crackers in my dorm room which helped a lot.
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[User Picture]From: arvindn
2007-01-30 05:00 pm (UTC)
After I thought of trace minerals I found several websites confirming that it is one, if not the primary cause of salt craving. example.

More importantly, my argument does not require that the salt lick response be inherited. I'm merely saying since our only source of salt used to be salt licks, we can't differentiate trace mineral deficiency from sodium deficiency. I'm not postulating an adaptation, but in fact a lack of adaptation -- we can't taste iron, phorphorus etc.
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