In Asia, where many people drink no milk whatsoever, breast cancer tends to be rare. In rural China, for example, among women aged 35 to 64, Campbell found that breast cancer deaths averaged 8.7 per 100,000, as opposed to 44 per 100,000 in the United States. In India, where people eat more dairy in the form of yogurt, other researchers have documented higher rates of breast cancer but still lower than those of Western nations. The same pattern holds true, Campbell says, when you narrow the focus to the West alone. A comparative study published in 1989 showed that even in Europe, two areas with higher milk consumption—Scandinavia and the Netherlands—also had higher breast cancer rates.
Worldwide, men seem far more likely to die of prostate cancer in countries where dairy consumption is high than in countries where it is low. A study published in 1977 revealed that 10 men die of prostate cancer in Western Europe for every one who dies in Asia.
Such cross-cultural studies are provocative, but they are by no means definitive proof because they often contain hidden variables. More precise results come from careful single-country studies that track individuals and their food choices for several years.
Recently, two large, lengthy studies in the United States linked dairy consumption to prostate cancer. In the Physicians’ Health Study, researchers tracked 20,885 male doctors over 10 years. Those who consumed at least 2 1/2, servings of dairy food per day were 30 percent more likely to develop prostate cancer than doctors who consumed less than half a serving. A 1999 study of nearly 50,000 subjects, called the Health Professionals Follow-Up Study, had found that men who consumed a lot of dairy products had a 70 percent higher risk of prostate cancer. If they also took calcium supplements, their risk jumped dramatically: Those who consumed a total of more than 2,000 milligrams of calcium per day raised their risk of metastatic prostate cancer more than fourfold.
Miller, of the Dairy Council, says, “Statistical correlations don’t prove cause and effect. And moreover, not all the studies say the same thing. . . .There is more evidence overall that dairy has anti-carcinogenic properties.”
Edward Giovannucci, an associate professor of nutrition and epidemiology at Harvard and a coauthor of both studies, believes that calcium itself, at high levels of consumption, promotes this kind of cancer by depleting protective levels of Vitamin D. Many years of research, not just two studies, have convinced him. “For prostate,” he says, “the data are generally consistent, and the high relative risk in the Health Professionals Study is quite worrisome,” given the push for very high calcium intakes in the United States.
In the United States, 10 million men and women suffer from osteoporosis, a chronic bone-wasting disease. One in two women and one in eight men over age 50 breaks a bone because of osteoporosis. After a hip fracture, many never recover their mobility, and one in five dies within a year. Among women, that makes osteoporosis a larger killer than breast cancer.
Many experts argue that Americans of all ages can stave off the onset of osteoporosis by adding more calcium to their diets. Bess Dawson-Hughes, chief scientist of the Calcium and Bone Metabolism Laboratory at Tufts University and president-elect of the National Osteoporosis Foundation, says the vast majority of U.S. teenagers and adults—70 percent of men, 90 percent of women—don’t get enough calcium from their diets. “We’re talking about a major deficiency,” roughly half the recommended amount, she says. And milk has lots of calcium.
Some nutritionists, however, see the problem and the solution differently. Walter Willett, a professor at the Harvard School of Public Health and chairman of the nutrition department, says, “There is no evidence that we have a calcium emergency, as the dairy industry would have us believe. We have one of the highest calcium intakes in the world.” Marion Nestle, chair of the nutrition and food studies department at New York University and a member of the Food and Drug Administration’s science advisory board, was surprised when the Institute of Medicine recently suggested that teenagers and adults over 50 increase their calcium intake to 1,300 and 1,200 milligrams, respectively, a day. “I think it’s amazing to have set the calcium requirements so high,” she says. The World Health Organization recommends 500 milligrams for children and 800 milligrams for adults.
To support the U.S. recommendations, researchers like Dawson-Hughes cite a consistent body of evidence. Many dozens of controlled clinical studies show, without a doubt, that increasing calcium intake adds bone mass. Therefore, they insist, dairy foods can fight osteoporosis. Milk, after all, is a package of nutrients that nature concocted to foster rapid growth in calves. But a growth spurt may not ensure the lifelong strength of bones. “The studies of bone mineral density can be highly misleading,” says Willett. “What is clear is that an increase in calcium intake causes a onetime small increase in density (about 2 percent). However, this does not continue to accrue and disappears when stopping the extra calcium.” Such a small rise in bone mass is probably not enough to protect against fractures.
Campbell stumbled across statistics about osteoporosis in the 1980s when he took a break from his animal studies to direct the China-Oxford-Cornell project, a massive investigation of diet and disease based on data gathered from 6,500 rural Chinese families. In general, the Chinese ate a nearly vegetarian diet. Another pronounced difference between China and the West caught Campbell by surprise: the contrasting levels of osteoporosis. Most Chinese were getting their calcium from vegetables and fruits alone. Although they got less than half the calcium recommended by the USDA, their bones seemed healthy. Among women over 50, the hip fracture rate appeared to be one fifth as high as in Western nations.
Were the Chinese absorbing calcium more efficiently from vegetables than Westerners were from dairy foods? Or might the rural Chinese, with their hard labor outdoors, make up for low amounts of calcium in their diet with exercise-induced bone growth? Campbell wondered if their milk-free diet could be part of the answer. Although milk’s calcium and other nutrients do promote bone growth, other substances in dairy foods—certain proteins and especially sodium—actually leach calcium from bone. The Chinese were evidently getting sufficient calcium from dark green vegetables, legumes, and some fruits. And because those foods don’t also promote calcium loss, the Chinese might not need to take in as much calcium overall. Campbell later learned that disparities between calcium intake and bone health can be seen worldwide. By the 1990s, nutrition researchers had gathered data from different parts of the world and found another surprising correlation: The more calcium people consumed, the more susceptible they seemed to be to hip fractures. People in those countries that consume the highest levels of dairy foods (North American and northern European nations) take in two or three times more calcium yet break two or three times more bones than people with the lowest calcium intake (Asians and Africans). “Osteoporosis,” Campbell notes, “is not yet fully explained.”
In 1997, results from a massive research project—the 12-year Harvard Nurses’ Health Study involving 78,000 nurses—added more evidence. At the beginning of the study, nurses reported on dairy foods in their diets, then updated the information every few years. The updates included reporting arm and hip fractures. (Researchers felt that if they collected data the other way around, nurses who had broken bones might retrospectively blame their diets and not remember dairy consumption as accurately.) The analysis corrected for variables affecting bone strength, such as age, vitamin and mineral consumption, caffeine, smoking, alcohol consumption, hours per week of vigorous physical activity, and birth control and hormone supplements known to stimulate bone growth. At the conclusion of the study, Diane Feskanich, Walter Willett, and colleagues at Harvard noted a correlation: Nurses who drank the most milk—two or more glasses per day—broke more bones than the others. They had a slightly higher risk of arm fracture (1.05 times) and significantly higher risk of hip fracture (1.45 times).
Miller does not put much credence in epidemiological population studies. “Many of those women may have known that they were at risk for a fracture and may not have drunk milk during development when it mattered, and then when they became aware of it later, drank milk,” he says. “It doesn’t necessarily prove anything.”
Thanks to Congress, dairy producers enjoy price supports and government purchase of surplus production. They plow some of their profits into promotional industry groups that fund research studies, they make alliances with medical organizations to educate the public about milk, and they provide free materials to schools suggesting that milk is vital to good nutrition. The Physicians Committee for Responsible Medicine alleges the dairy industry is so powerful that it dictates high calcium requirements in federal dietary guidelines. But Miller says, “The bottom line is that the current recommendations for dairy and calcium intake are based on available science. The people who formulated the recommendations are sound scientists that are at the top of their field, well respected. To suggest that they made those recommendations based on politics rather than science is just plain wrong.”
U.S. Department of Agriculture deputy undersecretary Eileen Kennedy notes that consumer preferences—not dairy promoters—shape federal nutrition policies. Americans get three fourths of their calcium from milk and other dairy products, says Kennedy. Given that, what would happen if the government removed dairy as a recommended food group? Would people fill the gap by eating more calcium-rich vegetables and legumes? Kennedy thinks not. They’d continue to follow current trends—shirking exercise that builds bone, consuming more foods such as caffeinated sodas, salted snacks, and meats that actually leach calcium from bones—and they’d be worse off than ever with less milk. “You can’t simply lop off the milk section and say the rest works,” she says. And no one can deny that the consumption of milk per capita has been slowly dropping for decades. Americans now drink more soda than milk, more coffee than milk, more beer than milk.
In the National School Lunch Program, however, milk is the only beverage available. One part of the Physicians Committee lawsuit alleges that milk’s unique status in school lunches amounts to racial discrimination. Studies suggest that 70 percent of African-Americans, 50 percent of Hispanics, and 90 percent of Asians have trouble digesting lactose, while only 15 percent of Caucasians do. Lactose-intolerant children could get enough calcium by drinking alternatives such as soy milk or calcium-fortified juices, but the federally funded program, which provides free meals to needy children, won’t reimburse schools for a lunch if they substitute nondairy alternatives for milk. Schools can decide to make substitutions anywhere else on the menu; the only specific food that the program requires is milk.
Dairy proponents insist that most people who think they are lactose intolerant can actually digest small amounts of milk—the trick is to train them. Indeed, pilot studies funded by the dairy industry have shown that when such children consume milk slowly, in sips throughout the day and with meals, they can often tolerate one or even two glasses daily. “What’s really racist is telling them they can’t consume a food that’s nutritious, affordable, and convenient,” says Miller.
Meanwhile, Campbell cannot forget the children he set out to help in the Philippines long ago. He raised all five of his own children, who range in age from 22 to 36, on nearly milk-free diets. And his five grandchildren seldom touch dairy foods. When they come by to visit, Campbell’s wife, Karen, is always ready to prepare a special treat for them. “She freezes bananas, puts them in a blender with rice milk,” he says. “These shakes are delicious, fantastic.”
Outside the family, Campbell faces more resistance to his diet ideas, but that hasn’t shaken his conviction that anyone can get all the calcium and protein they need from nondairy and plant sources. Antonia Demas, a former Cornell colleague of Campbell’s now working in the school system in Miami, Florida, has demonstrated with her award-winning school lunch programs that kids will eat and enjoy nutritious meals without meat or dairy foods. But she admits that kids still like the diet they’re used to. Donna Hurlock, a gynecologist involved with the Physicians Committee, says: “I’ve never given my daughter a glass of milk. My child is everything to me, and I don’t want to give her anything that would hurt her.” But they do have pizza once a week—with cheese. And so it goes, too, with Campbell and his grandkids. “They’re almost strictly vegetarian,” he says, “except a couple who cheat a little on cheese once in a while.”