Health

Lactose intolerant when you shouldn't be

Gene ExpressionBy Razib KhanDec 18, 2011 3:40 PM

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Milk, it does a body good (or not):

I’ve discussed this before earlier this year, when we got our results back (my husband, children, in-laws, parents, siblings… etc have all done genomic scans), two results came back that surprised us but proved true. My mother-in-law and husband were likely lactose intolerant. When I pointed that out to my mother-in-law she said “no I’m not.” But then she went on to explain that she never drinks more than a glass of milk because it gives her an upset stomach. Bingo. She learned over the decades that she was indeed lactose intolerant, and shifted behavior because of it, but just didn’t put a name to it. Later, when I looked at my husband’s profile, sure enough “likely lactose intolerant.” His answer was the same as his mother’s, “no I’m not.” Thing was, in the 15 years I’ve known him he’s had regular stomach problems with no solution. ... He probably didn’t make the connection earlier because his mother is of Danish descent (really? Danes aren’t lactose intolerant?) and often dairy in small amounts wouldn’t do a thing, or some products (like yogurt) would have little effect. The problems seemed ‘sporadic’ but frequent. His doctors never suggested lactose intolerance. We could have done a food elimination test, but that was time consuming and very inconvenient. In hindsight we should have done the slog of eliminating foods from the diet…but you know what they say about hindsight? (Or at least the Phantom Tollbooth). He’s the

This is interesting, because I know several people who went through something similar. The vast majority of Northern Europeans are lactose tolerant, at least judging by phenotype and that particular SNP. But, at least ~5% are not. That's not a small number in absolute terms, and even proportionally it is common enough that if you know 13 random Northern Europeans, there's a 50% probability that at least one of them is lactose intolerant. Note: There are other SNPs which likely confer lactose tolerance. And, it seems likely that environmental factors, such as adaptation of your gut flora, also matter in the final phenotype.

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