Every once in a while it's nice to recognize correctness, though. When two correct halves of a large and more complete correct whole come together, well, that's news I can and should write about.
A few days ago I posted about a new computer model study looking at The Origins of Lactase Persistence in Europe. That study also got a nice write-up in USA Today, which started its article, by Elizabeth Weise, with an overview of lactose tolerance and intolerance.
First off, most people who have bad reactions to milk aren't actually allergic to it, in that it's not their immune system that's responding to the milk.
Instead, people who are lactose intolerant can't digest the main sugar —lactose— found in milk. In normal humans, the enzyme that does so —lactase— stops being produced when the person is between two and five years old. The undigested sugars end up in the colon, where they begin to ferment, producing gas that can cause cramping, bloating, nausea, flatulence and diarrhea.
If you're American or European it's hard to realize this, but being able to digest milk as an adult is one weird genetic adaptation.
It's not normal. Somewhat less than 40% of people in the world retain the ability to digest lactose after childhood. The numbers are often given as close to 0% of Native Americans, 5% of Asians, 25% of African and Caribbean peoples, 50% of Mediterranean peoples and 90% of northern Europeans. Sweden has one of the world's highest percentages of lactase tolerant people.
Being able to digest milk is so strange that scientists say we shouldn't really call lactose intolerance a disease, because that presumes it's abnormal. Instead, they call it lactase persistence, indicating what's really weird is the ability to continue to drink milk.
All true, and all things that I've said myself in the past.
But not the entire story, something difficult to pull off in the confines of a single article that's designed to lead to a particular point.
Skip the now 520[!] comments attached to the story, most of which will make you despair of the notion that intelligence is also an evolutionary result and turn to the letters to the editor page.
There we find a comment from a person who - unbelievable as it might seem - actually knows what she's talking about. Theresa Nicklas, professor, Children's Nutrition Research Center, Baylor College of Medicine - Houston, wrote:
It's important to recognize that the lack of the lactase gene does not mean people can't enjoy milk and milk products. The limited ability to digest lactose (lactose maldigestion) does not necessarily result in any symptoms (lactose intolerance).
Although different people can handle different amounts of lactose, your readers should understand that even people who have a limited ability to digest lactose can enjoy dairy foods, often without any symptoms.
This has significant public health implications because it is difficult to get the recommended calcium and potassium in the diet without including dairy. A large percentage of Americans 2 years old and older are not consuming adequate amounts of calcium and potassium.
One against 520. Those aren't good odds. I'm happy to back Dr. Nicklas, making it 520 to 2. That's still bad, but heck, it's twice as good as before. I'd like to think that two people who are knowledgeable and right beat out the 520 who are neither. It's my fantasy of the day.
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