100 Million Years of Food, page 12
Sumptuous meaty feasts like this are a rarity in China. When two of my students invite me to visit their homes, two-story concrete dwellings set in sparsely forested countryside, some gamey chicken and bits of pork are served, but the mainstays on the table are tofu, eggs, peas, tomatoes, peanuts, and greens, fried in lard or, increasingly, vegetable oils, and, of course, white rice, with green tea or rice wine. Due to the lack of red meat and dairy, this type of cuisine is likely to delay the onset of chronic diseases like breast and prostate cancer, but the oily sautéed greens and white rice are likely risk factors for obesity and diabetes, respectively. When my students ask me what I think of Chinese cuisine, I tell them I like traditional Chinese cuisine, when lard was used to lightly sauté vegetables, rice was hand-milled and accompanied by yams or grains like barley, and insects, fish, and frogs supplemented the meat. Unfortunately, such food is quickly becoming a distant memory. Now a bullet train thunders through the countryside around Bengbu, cars, tractors, and motorcycles have replaced walking, old-fashioned lard has been replaced with cheap vegetable oils like soybean and corn oil, rising incomes are used to purchase meat and milk, and the rice is white as snow. In a country obsessed with modernizing, it will take another generation before Chinese people realize how damaging to health these dietary and lifestyle changes have been. Then the Chinese will start to look back to the ways that their ancestors once lived and ate.
ELIXIRS
Many children are not consuming recommended servings of dairy foods.… Dairy foods provide essential nutrients needed for body maintenance and protection against major chronic diseases.
—GREGORY D. MILLER, JUDITH K. JARVIS, AND LOIS D. MCBEAN, Handbook of Dairy Foods and Nutrition
Cow’s milk consumption is a major health hazard and should be recognized as a promoter of most common chronic diseases of industrialized countries.
—BODO C. MELNIK, “Milk—The Promoter of Chronic Western Diseases”
Three liquids have had an enormous impact on human health over thousands of years: water, alcohol, and milk. Tea and coffee have also been important beverages in parts of the world, particularly in terms of their economic impact in recent centuries, but because scientists are still largely unclear about the long-term health effects of drinking tea or coffee, we won’t delve deeply into these beverages. I’ve had long discussions with friends about the mood swings associated with coffee/caffeine dependence, but given the extreme irritability such discussions engender (especially as the time since the last caffeine hit drags on), I’ve learned not to frown or roll my eyes as my friends fork over their cash to the coffeehouse giants. In any case, according to one recent large American survey (more than 250,000 men and more than 170,000 women between the ages of fifty and seventy-one), drinking six cups of coffee or more a day lowers the risk of dying by 10 percent (men) or 15 percent (women); so perhaps my coffee-addicted friends have justification for frowning and rolling their eyes at me. The most obvious explanation for why drinking coffee cuts the risk of death is that the alertness accompanying caffeine consumption decreases the chance of getting into a fatal accident, but coffee drinkers also seem to have better chances of avoiding heart disease, respiratory disease, stroke, diabetes, and infections, which suggests that some other compound in coffee besides caffeine (like polyphenol antioxidants) might confer health benefits. Similar reductions in mortality have been obtained in Japanese studies on coffee drinking. Scientists haven’t noted any similarly substantial health benefits from drinking tea so far.1
Compared to coffee or tea, to say nothing of milk or wine, water seems plain and uncool. The old adage of drinking eight glasses of water a day seems almost quaint now, but there is a lively debate around the merits of drinking water, or at least around drinking certain types of water. About fifty years ago, doctors and scientists first noticed that in regions where people drank water that was “harder” (i.e., water having less acidity, leading to more bathroom scum and less soapy water), people tended to suffer from less heart disease and live longer. The first candidate for a life-boosting, blood-pressure-lowering chemical element was calcium. However, as researchers accumulated more data, they began to realize that calcium was probably not the responsible element, and attention shifted toward magnesium. Inadequate levels of magnesium could make heart rhythms more irregular, worsen the lipid profile and insulin control, and lead to more plaque buildup in arteries, all of which could exacerbate the risk of heart disease. Normally, if one thinks of magnesium at all, it’s supposed to come from a diet rich in vegetables, fruits, and nuts, but magnesium ions in naturally hard water are likely more easily absorbed by the body than the magnesium found in food or vitamin supplements. The importance of magnesium in water is especially disconcerting for parts of the world where there is increasing reliance on water sources other than groundwater, such as recycled wastewater and desalinized seawater. When I have the money, I like to drink bottled waters from Italy that have a lot of dissolved minerals. Such water has a superb taste and a lot of magnesium, perhaps the way nature intended it, but I understand that from an environmental perspective, not to mention my poor wallet, it makes little sense to import drinking water from other continents.2
Drinking water straight from a lake, stream, or puddle—great for acquiring useful minerals but also bothersome parasites—was certainly the chief drink of our ancestors. However, other beverages were even more valuable, for their powers to make us bold and imbecilic, or strong and tall, like magic potions out of a fairy tale.
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Our distant ancestors from millions of years ago would have been familiar with the taste of alcohol in fermenting fruits, but the ability to manufacture any sizable quantities of alcohol had to await the development of agriculture. The earliest evidence so far of the use of alcohol has been found in China, dating to around seven thousand years ago. Alcohol doesn’t preserve well because it evaporates quickly (which is why leftover wine is discarded), so any evidence about the use of alcohol in ancient times is necessarily indirect, but clever archaeologists have put together the following scenario. The Chinese domesticated rice at least nine thousand years ago, and rice is a good start for making alcoholic brew. However, making alcohol requires yeast, and yeast doesn’t grow on rice. Nowadays, a common method of making alcoholic beverages in Asia is to grow mold on blocks of rice or other cereals; the mold is introduced by chance through insects or by parachuting down from old ceiling rafters. The ingenious solution the ancient Chinese seem to have hit upon to obtain their alcohol was to mix hawthorn fruit and honey (both of which harbor yeast) with rice (to provide the yeast with fuel for generating ethanol), a combination that would have begun fermenting in a few days in a warm climate.3 Researchers have found evidence of beer-making using fermented barley in the Zagros Mountains of Iran dating to more than five thousand years ago. Around the Mediterranean, the idea of using grapes to make wine, likely mixed with medicinal herbs, was present from at least 3,000 BC in Egypt.
While there is considerable evidence that humans started to make alcohol in impressive quantities after the advent of agriculture, why we enjoy drinking it is a surprisingly controversial topic. Some scientists believe that animals, including humans, have a deep instinct to seek out ethanol, as a marker of valuable energy-dense fruits and nectar. Indeed, alcoholic beverages were an extremely important source of energy in some preindustrial diets; the daily ale consumption of an Englishman in the sixteenth century could exceed one gallon. Ethanol is a calorie-dense product: One gram of it packs seven calories, instead of the usual four that come from sugar and almost as much as the eight calories that fat delivers.
However, when frugivores like birds and fruit bats are allowed to choose between ripe fruit and alcohol-soaked rotten fruit, or between foods with varying quantities of alcohol, they almost always settle for the nonalcoholic choice.4 My uncle introduced me to beer when I was a kid, and it tasted much as my older brother had described it: horse piss. Considered from the perspective of ethanol-spewing yeast, this makes sense. Yeast and other frugivores, like bacteria, birds, and humans, have conflicting interests: We all want the fruit. When I was in grade school in Ottawa, a common tactic wily children employed to defend their desirable snacks was to spit on them, which swiftly rendered the contested item personal property. Likewise, yeasts like Saccharomyces have a knack of transforming fruit sugars into ethanol, because ethanol is toxic to frugivorous bacteria and vertebrates. That suits the yeast fine, because it can then employ its alcohol enzymes to convert the ethanol into usable sugar for its own leisurely consumption.5
When cedar waxwing birds gorge on alcoholic berries and then slam into windows and telephone poles—“If You Drink, Don’t Fly,” quipped a scientific paper title—it is more likely they are famished at the end of winter and less likely they are looking for a last drink for the road.6 (Some shrews that feed on alcoholic nectar ingest great quantities of alcohol for their body weight but show no signs of intoxication, which may mean that they have evolved physiological mechanisms to process the high alcohol content of their customary diet.)
Paradoxically, among humans in modern times, study after study has found that moderate alcohol consumption helps fight coronary heart disease. The customary finding is that around two drinks (such as a glass of wine, a can of beer, or a shot of spirits) a day for men or one drink a day for women cuts the risk of coronary heart disease, ischemic stroke (when the blood supply to the brain is cut off), and sudden death. No one has discovered exactly why alcohol has this effect, but alcohol consumption results in higher levels of healthy HDL cholesterol and of a protein that shuttles cholesterol out of arteries (ApoA-I), and in lower levels of a protein (fibrinogen) that may exacerbate the risk of cardiovascular disease, possibly through increase in clotting. Many people swear by the rosy blessings of red wine, but the advantages of alcohol may apply to alcohol in general.7
That being said, the benefits of booze accrue principally to people at risk of coronary heart disease, which is to say people in industrialized countries over the age of forty. Among young people, the causes of death tend to be the kind of drama that alcohol consumption aggravates rather than ameliorates: accidents, suicides, and homicides. (In developing countries, infectious diseases are the main killers, and thus tipping back a few drinks a day has little or no protective effect on mortality.) Indeed, heavy alcohol consumption (especially binge-drinking) has well-documented health risks, such as an increased risk of cirrhosis of the liver, hemorrhagic stroke (leaking or burst blood vessel), cancers of the upper digestive tract, and metabolic syndrome, a cluster of health conditions including high blood pressure, diabetes, and obesity.
Ethanol is a carbohydrate, like glucose, and delivers energy to the body. However, there are crucial differences in the way that ethanol and glucose are metabolized. Glucose has a deep evolutionary history in humans and other forms of life and is therefore recognized and welcomed throughout the body’s tissues. By contrast, ethanol does not evoke an insulin response and stealthily penetrates the liver, potentially resulting in liver damage, insulin resistance, and metabolic syndrome, as noted above.8
Moreover, it is worth bearing in mind that the harmful effects of alcohol are much more pronounced in women than in men. For a given amount of alcohol consumed, blood concentrations of alcohol in women tend to be higher because of the smaller average body size of women compared to men. A higher proportion of body fat in women also reduces the water space in women’s bodies, again increasing the blood concentration of alcohol in women relative to men. Among people less than fifty years of age, women tend to have less gastric alcohol dehydrogenase (enzyme) activity than men; with less alcohol broken down in the stomach, a large amount of alcohol is able to enter the bloodstream. Liver injury is more frequent and progresses faster among women than among men with similar histories of alcohol abuse. When exposed to alcohol, women have higher toxic acetaldehyde levels than men. This is why around one drink per day is considered to be moderate alcohol consumption for women, versus two for men.
Since alcohol is so detrimental to human health, one might expect that humans have adapted genetically to handle exposure to alcohol. Indeed they have—but in surprising fashion. The alcohol dehydrogenase (ADH) gene helps us convert alcohol to acetaldehyde. Acetaldehyde is usually soon broken down by another enzyme (acetaldehyde dehydrogenase) and glutathione to harmless acetate, but if the body is overloaded with acetaldehyde, the liver cannot make enough glutathione to match the demand, and thus toxic acetaldehyde builds up. Around ten thousand to seven thousand years ago, a variant of the ADH gene began to appear in human populations and became especially prevalent in East Asia. Oddly, this gene variant leads to greater production of toxic acetaldehyde and consequently the flushed faces, headaches, and hangovers that commonly occur when East Asians drink booze. This type of reaction discourages the ADH gene bearers from overdrinking and hence protects them.
Incidentally, the drug disulfiram, used to treat alcoholism, results in headaches and vomiting after ingestion of alcohol, thereby strongly discouraging further drinking. In my own family, my dad and my younger brother both get flushed faces from drinking alcohol and avidly dislike wine and beer; my older brother and I do not get these symptoms and enjoy our liquor very much. Indeed, scientists have observed that people with the protective ADH gene variant are far less likely to become addicted to alcohol. Fittingly, this gene variant increased in frequency where rice cultivation first arose and where rice wine—and bouts of exaggerated human drama—came soon after. By contrast, in other parts of the world, the farther one travels from East Asia, the rarer this protective gene becomes (it is very rare among peoples of the United Kingdom and the New World), which suggests that alcohol drinking has had a shorter history in these places, as well as a potentially more devastating effect on health, given the lack of protective genes. That being said, beer, considerably watered down, was a common beverage in medieval Europe; the alcohol content may have acted as a useful disinfectant for unreliable water supplies.9
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Around eight thousand years ago, at the same time the Chinese were figuring out how to plant rice and get high by steeping it with honey and hawthorn fruit and letting it ferment, people in northern Europe came up with the brilliant idea of stealing milk from a cow’s teat and chugging it themselves. A few years ago, I had a chance to give a presentation at Umeå University in northern Sweden and travel around the country for a week. I was impressed by the dairy-rich cuisine, redolent in cheeses and cream, and the attractive, statuesque Swedes. The link between height and dairy consumption has long been touted, so the size of milk-loving northern Europeans is not that surprising. More unexpected, however, is that milk-drinking nations have the world’s highest rates of hip fractures.10 Since we’ve all been taught that calcium is the basis for strong bones, the subject of milk and calcium generates a lot of head-scratching, angry tirades, and rebuttals. Is dairy healthy for humans?
The first thing to bear in mind is that milk is the most complicated substance that humans consume. Compared to milk, alcohol is child’s play. Besides calcium, cow’s milk contains phosphorous, saturated fat, casein and whey proteins, amino acids, the potent insulin-like growth factor 1 (IGF-1), antibacterial defenses (such as lactoferrin, lysozyme, and lactoperoxidase), immune system boosters (such as T cells, B cells, and immunoglobulin A), and a mad scientist’s treasure trove of hormones, including gonadal hormones (estrogens, progesterone, and androgens), adrenal gland hormones, pituitary hormones (prolactin and growth hormone), hypothalamic hormones (gonadotropin-releasing hormone, luteinizing-hormone-releasing hormone, thyrotropin-releasing hormone, somatostatin), parathyroid hormone-related protein, insulin, calcitonin, and bombesin (influencing satiety, blood sugar, gut acidity, and gastrointestinal hormones).11 New hormones in cow’s milk are still being discovered, so the list will march on.
In the initial phase of experimentation, milk drinkers thousands of years ago must have suffered indigestion; however, if milk was consumed for a long enough time, adaptation in the colon took place, increasing fermentation of lactose and cutting back on the hydrogen gases. Once invented, products like cheese, butter, and yogurt lasted longer and contained less discomfiting lactose.12 People in Africa got the same idea of using dairy, probably independently, because the genetic adaptations that allowed northern Europeans and East African pastoralists to digest lactose in milk involved different genes. Meanwhile, goat’s milk was exploited in places like the Mediterranean and West Africa; Central Asian herders consumed horse milk (mare’s milk has a protein and salt composition more similar to a woman’s milk than cow’s milk), and Bedouins did the same with their camels. (Bedouins could subsist almost entirely on camel’s milk alone, a testament to the remarkable life-sustaining properties of milk.)13 Historically, milk has also been obtained from sheep, water buffalo (milked in South and Southeast Asia; the source of authentic Italian mozzarella cheese), yak, and reindeer.14
The llama and its close cousin the alpaca seem to have been suitable candidates for dairying but were never milked in traditional times by their handlers in the Andean mountains (a region encompassing present-day Colombia, Ecuador, Peru, Bolivia, and Chile). Llamas were used to carry burdens, while the smaller alpaca furnished beautiful wool. As the geographer Daniel W. Gade has pointed out, the llama and alpaca are sufficiently docile animals, comparable to goats or sheep, that they could have been milked. The Inca were sophisticated enough to breed white llamas, but for some reason they never thought to tip back a cup of milk from their llama or alpaca. There is no trace of dairying in Incan history, art, or language. One possible reason llama and alpaca milking never took off is that dairying was a cultural invention that diffused across the Old World but was unable to penetrate into the Andean mountain ranges until the Spaniards arrived; the same holds true for other late cultural imports to the region, such as the wheel, the arch, and writing. Another factor that could have delayed the incorporation of dairy into the Andean cuisine is that locals already had calcium in their diets from the use of lime in potato sauces and as an accompaniment to coca chewing, and from the consumption of quinoa.15
