Lactose Intolerance and 2010

Happy New Year, Everyone.

Today is January 1, 2010. Somewhere in the United States, some cable station is playing the movie 2010 right now. I know because I bumped into it while flipping channels a while ago. That movie was made back in 1984, when 2010 seemed like a future so distant that space travel seemed like the easiest prediction to make.

Nobody's that sure about the future today. (I mean, 2009? Even looking backward that year isn't the least bit plausible.) We can't even agree whether we're starting a new decade or not. (Yes, 2009 meant the end of the Aughts. But 2010 will be the end of the first decade of the 21st century. And every year is the end of some decade. Every minute. Every second. Of course, when something happens 31,536,000 times a calendar year, people get bored and latch on to fun stuff with more meaning, like having a zero at the end. You have to be very bored to read meaning into that, but it's all reruns on television this week, isn't it?)

So here's what I know for sure.

Lactose intolerance. It's a simple thing that we make very complicated. All mammals are genetically programmed to produce milk to feed their live young. And all mammals manufacture a unique sugar, lactose, to use as one of the energy sources in that milk. (Except for the monotremes, the most primitive mammals that evolved before lactose did, and the pinnipedia, sea mammals that use extra fat rather than lactose.) To digest lactose, that is, to break it down into simpler sugars so that it can be absorbed into the small intestine, all the lactose-producing mammals also manufacture an enzyme called lactase. Nobody really understands why the mammals went to the trouble of having to build up a complex sugar found nowhere else in nature just so that they would also have to make a special enzyme just to break it down. Somewhere along the line evolution thought this was a good idea. It works. Mammals are extremely successful animals.

It works, but it takes effort, in the form of extra energy to do this double manufacturing process. Mammals only do it for as long as is absolutely necessary, for the length of time they would normally be dependent on their mother's milk. At about the time of weaning, all mammals lose the ability to manufacture lactase. After that age, all mammals are lactose intolerant.

Humans are mammals. Humans have lactose in mother's milk, the most lactose of any species, about seven percent worth. All humans manufacture lactase, except for the tiniest handful who never do. These babies, who have what is called congenital lactose intolerance, used to die of starvation within a week of birth. They couldn't survive until nondairy milk substitutes were found early last century.

And all humans naturally stop manufacturing lactase at about the age of weaning, which is around three years. That means we are all naturally lactose intolerant.

Except some are not. Some humans are mutants. Well, all humans are mutants. Every single one of us have some mutations on some genes, which is why every one of us is different from all the others. One particular mutation, found on chromosome 2, either never sends out the signal that turns off lactase production or doesn't send it out until after the normal age of weaning. Around 30% of humanity has this mutation.

That's where it gets complicated. How do we define lactose intolerance? Is it by the form of the gene we have? Some people use this definition. That's how scientists estimate numbers and percentages like "Around 30% of humanity has this mutation."

The problem with that definition is that some people who currently manufacture lactase and who can drink milk just fine get classified as lactose intolerant. This confuses everyone. Wouldn't it be better to define lactose intolerance as those people who get symptoms from drinking milk (even if they don't have another disease or genetic condition)? That is better, and it's the definition that most researchers writing about the subject use. Unless they're genetic researchers who care more about genes than about symptoms.

I care about symptoms. That's because I'm lactose intolerant either way you define it. I'm pretty sure that most of you reading this care about symptoms too. Whatever's happening on my chromosome 2 is less interesting to me than what happens in my large intestine after drinking milk.

I can predict one piece of the future, therefore. For the rest of 2010 I'll be spending a lot of time writing about nondairy products, lactase pills, lactose-free cookbooks, and anything else that might help people who want to avoid the lactose in milk. I'll also write regularly about ways of avoiding milk altogether for those of you with dairy allergies or dietary needs that make you want to cut milk either temporarily or permanently out of your diet. And I'll spend the rest of my time correcting the misinformation on these subjects I find on the great unwashed intrawebs out there. It's all good.

Thank you for reading. Now, and in the future.