“Dairy has gotten so controversial—do we need it or not? The fact that so many people have a problem digesting lactose is just plain weird. Thoughts?”
It’s no surprise that passions run high when it comes to dairy products. After all, a mother’s milk, the first food of newborn mammals the world over, is as primal as it gets.
And these days the discussion can veer off in all sorts of directions. Is milk, for instance, a “perfect food,” as the dairy cartel—er, industry—would have you believe, or is it toxic and the cause of cancer and other illnesses? Should you buy organic dairy products or those from conventional cows, which are given recombinant bovine growth hormone (rBGH) and subtherapeutic antibiotics? Then there’s the pasteurized versus raw debate, and the unfortunate effects of industrial dairying on the animals’ health, our health, and the environment. On the up side, there is an ever-growing number of small-scale dairies that are making superb artisanal products based on fresh, flavorful milk and cream and utillizing techniques from ancient milking regions. Good-quality dairy, if you choose to eat and drink it, has never been more widely available.
But to the matter at hand: Do we need dairy?
Well, for humans and other mammals past the age of weaning, the answer is no. A generations-old marketing blitz to the contrary, milk is not a nutrient, but simply a food—one you can choose to eat (in many delicious incarnations) or not. I’m paraphrasing Marion Nestle here; she’s a New York University nutrition and food studies professor (who, for the record, is unrelated to the global foods company). Dairy contributes about 70 percent of the calcium in American diets, she states on one of POV25’s Food, Inc. pages. But, she continues, “if you eat plenty of fruits, vegetables, and whole grains, you can have healthy bones without having to consume dairy foods.” I would add to that a few of my favorite nondairy sources of calcium—collards, kale, and arugula.
Okay, now onto the controversial and absolutely fascinating subject of dairy allergies and intolerance. Although both are genetically based, they are very different. A milk allergy is an immune response to milk proteins. It is relatively rare, affecting two to three percent of babies and toddlers. Some of them grow out of it, and I happened to be there when one mother I know put a bowl of vanilla ice cream before her previously limited teenager. He took a bite, and involuntarily closed his eyes. “Oh, mom,” he said.
Lactose intolerance, on the other hand, is a reaction to—yep—lactose, which is not a protein but a milk sugar. Digesting lactose requires an enzyme called lactase (gotta pay attention to the vowels), which is produced in mammals at birth. After weaning, lactase output in all mammals, including most humans, slows down, then disappears. Why it does so is a question that evolutionary biologist Marlene Zuk thinks has received too little attention. In the just-published Paleofantasy: What Evolution Really Tells Us About Sex, Diet, and How We Live, she makes the point that “saying ‘it’s not needed anymore’ isn’t really satisfying, since of course organisms retain many characteristics that aren’t necessary...” She cites the human appendix, of course, as well as the vestigial legs in whale skeletons.
Whatever the reason for the gradual disappearance of lactase production, it’s fair to say that dairy consumption in someone who is deficient in the enzyme causes no end of unpleasant digestive consequences. If I’m talking about you, take heart: You are not alone. In fact, you are in the majority. And since most adults in the world are lactose intolerant (with symptoms that range from mild to severe), scientists would like us all to stop using the term, which implies an abnormal condition. Instead, they would prefer the more-accurate term lactase persistent to describe the approximately 35 percent of those in the world who carry the trait. Since it is dominant, not recessive, the number of people who can enjoy a glass of milk with chocolate chip cookies or pile the whipped cream onto strawberry shortcake will increase.
And this, Dear Readers, is evolution in action, according to Zuk. In fact, milk as a food source is the subject of a chapter in Paleofantasy, and it turns out to be an elegant example of how, through natural selection, our genome and culture have influenced each other in an evolutionary blink of an eye. The custom of drinking milk, after all, presumably arose after cattle were domesticated 8,000 to 9,000 years ago in the Middle East (and spread across northern Europe) and, independently, in Africa just over 3,000 years ago. In both places, it was a source of untainted liquid on the hoof, so to speak, and so it makes sense that those whose ancestors herded cattle and other milk-yielding animals are better able to tolerate lactose.
The answers to Zuk’s many intriguing questions (which begin with what came first: milk drinking or the change in the lactase gene) lie in the data revealed by some of the most sophisticated genetic and archaeological findings of our day. And the research continues.
“The analysis of our internal microbiome,” Zuks writes, “the diverse array of microscopic organisms living on and inside of us, is one of the most exciting emerging sciences. It may help us understand how the Somali ... and the Finns evolved convergent digestive abilities, despite their wide geographic separation .... Our ancestors had different diets, and almost certainly different gut flora, than we have. We continue to evolve with our internal menagerie of microorganisms just as we did with our cattle, and they with us.”
In other words, change is change.
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