Food, Genes, and Culture

Eating Right for Your Origins

ISLAND PRESS

Contents

Discerning the Histories Encoded in Our Bodies

AS WE INITIATE our journey together, I want to take you to a place in the desert that forced me to embark on this journey to begin with. It was there that I first saw for myself how the inexorable loss of ethnic food traditions could send, as Pima Indian elder had prophesied to me, the health of an entire people down the drain.

It was another Pima Indian friend, a fellow gardener named Gabriel, who first made me see that various ethnicities respond in dramatically different ways to the very same foods and drinks. Only later did I understand the degree to which these responses are curious outcomes of interactions among genes, environments, and cultures, some of them tragic, some protective, and others downright funny. While Gabriel was the first friend I lost to the darker side of these interactions, he was also the first to let me see the lighter side. He did so in a way that was patterned after the behavior of that old-time trickster, Coyote.

"Hey, White Guy, can you take some time out from your busy schedule to help me drive some commodity foods out to some bro's of mine out at Ak-Chiñ village?"

"Sure, I'll be your delivery boy. What are we going to deliver? Italian pizza or Indian fry bread?"

"Powdered milk. A bunch of it. Help me put it in the back of your pickup."

The powdered milk came from the federal government surplus commodity foods program, which typically provided such foods to low-income families on the reservation on a monthly basis. The foods were also stockpiled in a warehouse where families had to come with their vouchers to obtain them, but because Gabriel worked for the tribe's nutrition program, he had a little of every commodity stashed away in a storage closet in his office. On occasion, we would share the hidden stash with his friends out in remote villages who did not come into town very often; sometimes we would even sneak the cans and boxes of government commodities into Mexico for Indian friends living south of the border. I did not particularly like the cans of greasy beef, the white flour, and the Velveeta-like cheese the government offered, not merely because none of these foods were part of the traditional Indian diet, but because many were fatty, sugary, or fiber depleted ; in short, the kiss of death for Native American communities already suffering from nutrition-related diseases. In this case, powdered milk seemed like the least of the evils the commodities program had to offer, so I reluctantly helped Gabriel place several big cardboard boxes of white powder in the pickup truck. Then we were off; driving down winding dirt roads through fields of desert wildflowers on a lovely spring morning.

As we arrived at Ak-Chiñ village, Gabriel directed me over to a baseball field where a number of young men and teenage boys appeared to be practicing for an upcoming game against another village's team. He got out, walked over and talked to one of the men in his native tongue, then came back to the truck.

"C'mon, White Guy, this is where we can leave the boxes. Gonna help me?"

I didn't get it. "You mean we're gonna distribute the milk here so that these guys can take it home to their families? Why don't we just drive around and drop the boxes off at their homes?"

Gabriel laughed wildly. "Noooo. They've had more of this crap at home than they know what to do with. It just sits there and goes bad. They stopped picking it up at the warehouse, but now they need some for the baseball game tonight."

"They're serving milk at a baseball game?"

"No, White Guy. They need it to lay down the baselines so the players will know where the infield is among all them wildflowers! Serve the stuff? You're kiddin', 'enit? We can't drink milk, even when it's mixed up from powder! Give me milk, and I bloat up like the Pillsbury Doughboy. Don't you know squat about us? All of us Indians got lactose intolerance."

Ah, lactose intolerance. Sure, I had heard that some Indians suffered from it, but could not recall any of them talking about it in front of me. It was years later before I understood that lactose intolerance is not just a dietary constraint for Pima Indians; more than 30 million Americans—including many of recent African and Asian descent—cannot digest the principal sugar in milk very long after they have been weaned from their own mothers' breasts. In fact, the weaning of most breast-fed children in the world may be precipitated by a gradual decline in the activity of lactase, an enzyme that breaks down the lactose into easily digestible glucose and galactose. Without sufficient lactase to digest it, lactose simply sits in the child's gut, absorbing water through osmosis and expanding until it forms a substrate for gas-producing microbes.

I realized that I was perhaps in the minority of Arizona residents whose tolerance to lactose extended into adulthood. Among Gabriel's Pima and Papago (O'odham) Indian kin, such lactose malabsorption affects 40 percent of all four-year-olds, 71 percent of all five-year-olds, 92 percent of all seven-year-olds, and 100 percent of the population eight years or older. If exposed to as little as four ounces of raw milk, both weaned children and adults suffer bloating, indigestion, and in severe cases, intestinal cramping and diarrhea.

Three decades ago, a cultural geographer named Frederick Simoons noticed that the global distribution of extended lactose tolerance was strongly correlated with the distribution of ancient herding peoples in Europe, Asia Minor, and northern Africa; teenage and adult residents in most of the rest of the world were lactase deficient. Around 10,000 years ago, a mutation occurred in the DNA of an isolated population of northern Europeans that allowed them to tolerate milk as a nutrient-rich resource. This adapted tolerance to milk gradually spread through intermarriage with other groups but may have independently emerged as a mutation in the DNA of other peoples as well. In any case, certain ethnic populations that carried this gene in low frequencies—and then subsequently adopted a pastoral lifestyle and cultured-milk consumption—found that their lactase activity gradually extended into adulthood. It is assumed that most of these people first used small quantities of raw milk in a ritualistic manner or initially consumed only fermented products such as yogurt and cheese, for which bacteria have already converted lactose into digestible sugars. The small percentage of lactose-tolerant individuals in any population was rapidly favored when these rich nutritional resources arrived, so that within just fifteen generations of eating cheese and yogurt, the frequency of lactose tolerance increased dramatically.

It appears that two single-unit DNA changes occurred that extended lactase enzyme production into adulthood among herding peoples. From an evolutionary perspective, it seems that lactose intolerance—which formerly regulated the time of weaning among nonagricultural societies—was suddenly relaxed. Keep in mind that among hunter-gatherers who had never kept livestock, children were typically weaned earlier than they were among herding societies. In wildland habitats where the supply of foods was seasonally variable, early onset of lactose intolerance would curb the child's desire to nurse and might keep mothers from depleting their reserves. This would also allow maternal fertility to resume earlier, since it is otherwise depressed by lactation. In short, childbirths in hunter-gatherer families were more closely spaced, with a higher probability of infant mortality.

In contrast, cultures that adopted livestock production gained the means to provide enough milk to ensure the survival of nearly every child, as long as they kept their rangeland forages from being depleted. Whether or not you are genetically predisposed to lactase deficiency depends upon how recently your ancestors adopted livestock and adapted to a novel set of nutritional opportunities associated with milk cows, goats, sheep, or water buffalo.

I once exchanged perspectives on this issue with food psychologist Paul Rozin, discussing his pioneering work on the significance of cultural selection for lactase tolerance. I found Rozin in New York City, where he was taking time off from teaching at the University of Pennsylvania to devote a full year to research at the Russell Sage Foundation. A man of modest build but commanding presence, Rozin had studied cultural culinary practices on several continents and had helped his former wife, Elisabeth Rozin, articulate a popular theory of "ethnic flavor principles" that underpin the world's major cuisines. But what Rozin and I spoke about that day was the peculiar manner in which cultural selection of ethnic diets has at times overridden innate biological tolerances to trigger genetic adaptation to new foods. In most cases, we think of biology dictating the path that cultural food preferences follow; that is, the natural selection of certain genetic traits tends to override cultural behaviors that do not always have immediate survival value. But, as Rozin has convincingly argued, "The biology-to-culture arrow can be reversed. Although we do not know the [historic] details of the pathway, the end product—lactose tolerance under genetic control—suggests that cultural practices of drinking raw milk and dairying provided the selection pressure for genetic change. Therefore, it is possible to go from culture to biology" (P. Rozin 1982).

The revolutionary significance of Rozin's evolutionary interpretation seems paradoxical at first, but its ultimate significance has not been lost on others. In his best-selling exploration, Genome, science writer Matt Ridley explained it this way: "The evidence suggests that such people took up a pastoral way of life first, and developed milk-digesting ability later in response to it.... This is a significant discovery. It provides an example of a cultural change leading to an evolutionary, biological change. The genes can be induced to change by [several generations of] voluntary, free-willed conscious action. By taking up the sensible lifestyle of dairy herdsmen, human beings created their own evolutionary pressures" (Ridley 2000; emphasis added).

Those ethnic populations that created their own evolutionary pressures, in this case, had to possess in low frequencies the gene for lactase production to begin with. But as long as this gene could be found among them, a relatively rapid rise in the frequency of this gene would occur as long as cheese or yogurt eaters gained nutritional and reproductive benefits from adding milk products to their diets.

The ultimate reasons that Gabriel and the Ak-Chiñ baseball team were inclined to used powdered milk for marking infields rather than drinking it are buried deep in the genetic and cultural history of their people. Until very recently, their bodies were shaped by hunting and gathering in an unpredictable desert environment rather than by herding cattle or sheep on the open range. Lactose intolerance is one of the ghosts of evolution encoded (then hidden) in their bodies.

~ Another ghost, a scarier one, is also present among the Pima, and Gabriel was also the person who taught me about the dark side of this dance between genes and drink. Until I was shaken by Gabriel's untimely death, I had not thought very much about how food and drink differentially influenced individuals of ancestry other than my own. Because Gabriel was the first Native American I had ever worked with side by side, day in and day out, I have deeply grieved his loss from this world. Ever since his death, it has been hard for me to drink or eat the things we once shared without his image appearing before me: long, straight, thick, raven-black hair; a mischievous, rounded face; thick forearms; and a barrel chest. Even if I had not known his ancestry, I still would have loved his riotous sense of humor, his throaty laughter, his unflagging allegiance to family and friends, and the heartfelt ways he shared his homeland with newcomers.

Gabriel was from a family of Pima Indians and grew up in the same Gila River Indian community as the Iwo Jima hero, Ira Hayes, who died drunk in an irrigation ditch a few years after World War II. Like Ira Hayes, the interaction between Gabriel's genes and his cultural and physical environment made him unusually susceptible to alcohol and to adult-onset diabetes, the latter affliction being prevalent among half the adults living in the Gila River Indian community today.

And yet, I had hardly noticed these vulnerabilities while Gabriel and I were busy building fences, shoveling manure, and planting vegetable crops for elderly Native Americans living on a desert Indian reservation near the one on which he grew up. Remembering those days, I wonder how much he or I were even aware of differences among people back then. After all, both of us were in our twenties, at the peak of our capacity for physical endurance, and so we behaved as if we were equally invincible. We worked hard renovating fields and gardens all day long and played hard in the evenings, going out to all-night "chicken-scratch dances" where Indian bands played endless polkas, cumbias, waltzes, and boleros while we swirled around the dance floor with our partners. Before dawn, we would devour bowls of chile colorado con carne, piles of pinto beans, huge flour tortillas or fry bread, and then wash it all down with a beer or two.

We justified our enormous appetites by talking about all the backbreaking labor we had been doing, for as it approached the harvest, we would have been working double time. Although both of us were already somewhat overweight, we stayed so physically active that we assumed we were leading healthy lives. Because we occasionally helped the reservation's nutritionists with village workshops on growing native foods to prevent diabetes, I knew that Gabriel was familiar with the nutritious foods that formed the basis for his people's traditional diet. Even though they were being abandoned by many of his kin, I knew that he still had access to them. During those first couple years of working with one another, I certainly did not worry that Gabriel would become a diabetic or an alcoholic.

What became belatedly apparent to me was that Gabriel's good personal intentions and family-oriented instincts were ones that could be easily derailed. A few of our mutual friends on the rez were prone to binge drinking, and sometimes Gabriel would join them, disappearing for several days. I would try to listen quietly, nonjudgmentally, whenever he returned to work hungover and disheartened, having to deal with the problems that the binge had created for him at home and in the office. Once, when he had avoided such perils for several months running, I invited him to a celebration at my home. He came early to help me set up tables, chairs, and coolers. When we about had it all ready to go, he pulled me aside so he could say something before the others began to arrive.

"Hey, buddy, ... I ... I hope you don't mind watching out for me tonight."

"Watch you? Watch you what? Watch you dance your way into cumbia heaven?"

"No, man, I mean watch me if I start drinking too much or wolfing down the food.... I get hooked before I know it, you know, so watch out.... Hell, I don't even know how to explain it to you. Well, what I mean is, even though you hang out with all of us Indians, I don't think you know how different it is for us." He grew sad, his voice tapering off, "Sure, you stay up with us all night, but I just don't think it hits you the same way."

I was suddenly aware of some palpable distance that had edged between him and me, a distance I had also felt between friends I had back in town and the rez gang to whom Gabriel had introduced me. "You mean the way alcohol hits you?"

"It's not like getting a little buzz off a beer, you know.... For us, it's like going into an entirely different space ... we're in there by ourselves, not ever wanting to come out. Hey, I'm not trying scare you—as if I'm gonna to get drunk and rowdy tonight—but just keep an eye on me, OK? I mean, it's hard for me to even talk about.... Look, you need anything else done? You know, before all our buddies show up?"