http://www.discover.com/aug_00/featmilk.html
Worrying About Milk
By Will Hivley

  T. Colin Campbell grew up on a small dairy farm of 210 acres, nestled
among glorious green pastures near the Shenandoah Valley in northern
Virginia. Almost from the moment he learned to walk, he dogged the footsteps
of his father, Tom Campbell, as he tended the farm's 20 to 30 milk cows.
Eventually, young Colin was given the chore of "stripping" by hand any milk
from the cows' udders that the milking machine left behind. He also learned
how to operate the family butter churn and, on special weekends, helped man
the hand-crank bucket used to make ice cream. The Campbells were a simple
family, without much money, but considered themselves blessed to have milk
straight from the cow. "We had the nectar of life," Campbell says. "I was
proud of the fact that somehow, every day, I could drink a gallon of milk,
or more."

  Campbell went on to devote his life to nutritional research.Two decades
ago he contributed to the first federally funded report on the relationship
of diet to cancer, an influential study that helped establish the
nutritional importance of grains, fruits, and vegetables. At age 66, he is
nearing retirement as a nutritional biochemist at Cornell University. He is
also president and CEO of Paracelsian, a company that promotes holistic
health and sells assays to measure dioxinlike chemicals and evaluate herbal
products. Campbell lives on a quiet residential street near the Cornell
campus, by all appearances like most of his neighbors. But these days not
one drop of milk touches the lips of anyone in his household, and his
refrigerator is stocked with soy cheeses, sorbet, and rice milk. "People
might think we're nuts," he says. "But nondairy beverages and foods are
pretty good once you adjust to the the taste."

  Like most Americans, Campbell once assumed that dairy products were not
only wholesome but also an essential part of the daily diet for anyone
desiring good teeth and strong bones. After years of scientific research,
however, he's now convinced that cow's milk is responsible for a share of
our nation's medical woes. The fact that fats in dairy products can
contribute to hardening of the arteries and heart disease has long been
common knowledge. But Campbell worries that stocking up on skim milk and
low-fat yogurt— or going organic because of concerns about cows exposed to
pesticides, antibiotics, and bovine growth hormones— may offer only limited
protection against the potential health hazards of milk. Unlike most
nutritionists, he questions even the much-touted health benefits of milk.
And he believes his research raises issues his colleagues have tended to
ignore.

  The bottom line for Campbell is simple: "It's unnatural to drink milk."
Most adults in Asia and Africa, along with many in southern Europe and Latin
America, have trouble digesting lactose, the main sugar in the milk of both
humans and cows. Some suffer from bloating, cramps, or diarrhea if they try.
A 1978 population survey, compiled by geographer Frederick J. Simoons of the
University of California at Davis, suggests that it was only because of a
genetic aberration that milk became a food staple in northern Europe and
North America. Nature normally programs the young for weaning before they
reach adulthood by turning down production in early childhood of the enzyme
that breaks down lactose. But a gene mutation inherited by people of
northern European descent prevents the production of this enzyme from being
turned down. As a result, the majority of Americans can drink milk all their
lives.

  Campbell argues that the ultimate problem with cow's milk is that nature
concocts different formulas of mother's milk for different species. What's
good for baby calves isn't necessarily good for human babies or adults.
"Isn't it strange that we're the only species that suckles from another
species?" he says. Campbell theorizes that cow's milk unnaturally stimulates
enzymes and growth hormones in the human body that increase the risk of
various diseases. Moreover, he has come to the conclusion that cow's milk
may not even do what it is supposed to do best— build strong bones. And
recent studies suggest that humans may need less calcium for strong bones
than was once believed and that other foods, including various vegetables
and legumes, may be better sources than cow's milk.

  "It would be hard to imagine a worse vehicle for delivering calcium to the
human body," says Neal Barnard, head of the Washington, D.C.-based
Physicians Committee for Responsible Medicine, a nonprofit advocacy
organization that promotes vegetarianism and is opposed to milk consumption.
Of the 100,000 or so members of the Physicians Committee, about 5,000 are
actually physicians. Both Barnard and Campbell, a science adviser for the
group, believe that government officials have turned a blind eye to the
potential health risks of milk. Last December, the Physicians Committee
filed a lawsuit against the U.S. Departments of Agriculture and Health and
Human Services claiming the agencies unfairly promote industry special
interests through official dietary guidelines. The USDA, the Physicians
Committee argues, has an inherent conflict of interest: a dual mission to
assist dairy farmers as well as to promote good nutrition. What if the
subsidized dairy foods that the government recommends aren't good choices
for healthy eating?

  Government health officials argue that evidence of health risks from milk
is circumstantial. Moreover, they contend that dietary guidelines that focus
on dairy products as a major source of calcium are based on a realistic
assessment of the food choices most Americans make. "There's nothing against
vegetable sources of calcium," says Eileen Kennedy, deputy undersecretary of
research, education, and economics at the Department of Agriculture. "But we
have to fashion healthful eating around current habits."

  In Campbell's view, such thinking is circular. The reason a lot of
Americans follow a dairy-rich diet, he argues, is that they assume it's the
healthy thing to do.

  Gregory Miller, vice president of nutrition research at the National Dairy
Council, dismisses the Physicians Committee as "essentially an animal rights
organization. If consumers want nutritional advice," he says, "they should
get it from mainstream health and medical health professional organizations.
. . . Here they are saying don't eat the food group that provides 75 percent
of calcium in the diet. With little kids who don't like vegetable sources
like broccoli and kale and brussels sprouts, it becomes especially
important."

  Campbell, who believes all animal protein is bad for human health, says he
is not an animal rights activist. He believes that animal experimentation is
essential for research.

  All through his undergraduate years at Penn State and then veterinary
school at the University of Georgia, Campbell spent his time happily milking
the family cows during summer vacations and drinking glass after glass of
fresh whole milk. When he transferred to Cornell in 1956, after landing a
full scholarship for doctoral studies in animal nutrition, he set out to
learn how to produce more animal protein "so we could eat more of it." But
his outlook changed after he headed overseas in 1965 to serve for 10 years
as coordinator of a U.S. AID project in the Philippines, where poverty-
stricken children were dying mysteriously from liver cancer believed to be
linked to malnutrition. For protein, the children depended largely on
peanuts, which in the tropics often contain relatively high amounts of
aflatoxin, a carcinogen produced by mold growth. To his surprise, Campbell
discovered during his tenure in the Philippines that the incidence of liver
cancer was especially high among some of the best nourished kids, whose
diets were supplemented with powdered milk provided through a U.S.-
subsidized program. He was completely baffled until he read about a 1968
research study conducted in India by Madhavan and Gopalan and published in
the Archives of Pathology. The study linked a milk protein to liver cancer
in lab rats. "That was a signal event for me," Campbell says.

  Left with the suspicion that feeding milk to the Filipino children may
have been a mistake, Campbell began studies to explore the question. During
the next three decades, he conducted a series of lab experiments at Cornell
and Virginia Tech and found that rats given a brief initial exposure to
aflatoxin tended to develop liver cancer when fed casein, the main protein
in milk. "We could turn on or turn off cancer growth," he says, by
increasing or decreasing the amount of casein.

  Are such animal studies relevant to humans? One common theory on cancer
development, first advanced in 1939 by Berenbloom and Shubik, is that tiny
precancerous lesions accumulate throughout the body because of random
mutations or exposure to small amounts of carcinogens. These lesions
normally remain dormant, but a steady dose of cancer promoters in the diet
may override natural defenses against the growth of tumors. In laboratory
experiments on animals, scientists try to re-create this two-stage process.
Aflatoxin, in Campbell's experimental model, stands in for any kind of
carcinogen to which a human might be exposed. In lab animals, the liver has
become a litmus test for cancer studies because of its sensitivity to
carcinogens and its rapid reproduction of cells. And among lab animals, rats
are considered particularly relevant to human cancer studies because they
need the same nutrients and proportion of protein for maximal growth as
humans. But lab rats often don't get cancer from suspected food carcinogens
unless they are given enormous doses. Since humans normally receive far less
exposure, it's not clear if the tests always reveal a significant danger.
Campbell chose to feed casein to rats in normal doses, with 15 to 20 percent
of their diet (by weight) coming from casein. The typical American diet is
roughly 17 percent protein, says Campbell, though the protein, of course, is
not all casein. He found that the threshold amount of casein required for
switching on tumor growth averaged around 10 percent of the diet.

  E. J. Hawrylewicz, a nutritional biochemist and research director at Mercy
Hospital and Medical Center in Chicago, performed a somewhat similar series
of experiments that revealed lab rats are more likely to develop breast
cancer tumors when fed casein than when fed soy protein. But he found that
the lab rats' diets had to be rich in casein, at least 20 percent, to
produce significantly more tumor growth, as opposed to Campbell's results of
10 percent. Because Americans consume a variety of proteins to reach 20
percent— mostly from animal foods like eggs and meat in addition to dairy—
Hawrylewicz argues that casein may not be harmful if consumed in modest
amounts: "I would definitely not say that it's anything alarming."
Nonetheless, Hawrylewicz agrees with Campbell that a good anticancer
strategy is to choose a diet rich in plant rather than animal proteins.

  But Miller, of the Dairy Council, contends that casein is a red herring.
He and other nutritionists cite evidence for the health benefits of dairy
products: studies linking milk consumption to bone growth, reduced blood
pressure, and reduced risk of colon cancer. And, he adds, "other milk
proteins have demonstrated anti-carcinogenic properties."

  In cancer research, pinpointing a singular mechanism that triggers tumor
growth is invariably an elusive quest. Each cell where cancer may develop
passes through several precancerous stages; some may have mechanisms in
common and yet have other pathways peculiar to one bodily organ— lymph
nodes, say, or brain cells. "There are likely many, many mechanisms,"
Campbell says. But epidemiological research adds a new line of evidence, and
in this case it suggests a correlation between milk consumption and at least
two kinds of cancer prevalent in Europe and North America: breast and
prostate.

  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 they are 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. While these
results hint at a link between milk and cancer, they are far from
conclusive.

  Still, Edward Giovannucci, an associate professor of nutrition and
epidemiology at Harvard and a coauthor of both studies, sees reason for
concern. He believes that calcium itself, at high levels of consumption,
promotes prostate 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 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.

  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." The
question is whether sustaining this slight increase will 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,
vegetarian diet could be part of the answer. Although milk's calcium and
other nutrients do promote bone growth, says Campbell, other substances in
dairy foods and other animal products— certain proteins and especially
sodiumÑactually leach some 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 epidemiological
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).

  Robert Heaney, a professor of medicine at Creighton University in Omaha
and a specialist in bone biology, questions the value of this study and
cites others that contradict its findings. Of 40 to 45 studies looking at
controlled calcium intake and bone loss, he says "all but two showed a
benefit from calcium. Eight to 10 of the studies used dairy products; every
one showed bone benefit." Even in some 80 studies that didn't control
calcium intake but simply relied on subjects' reported intake, he says 75 to
80 percent were positive, showing less bone loss, fewer fractures, or more
bone gain.

  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 educate health
professionals about milk, and they provide free materials to schools
suggesting that milk is vital to good nutrition. In its lawsuit, the
Physicians Committee for Responsible Medicine alleges that the federal
dietary guidelines are prepared by advisers with ties to the meat and dairy
industry. 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 who 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. Consider, Kennedy suggests, 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. They also drink more coffee than milk and more beer than milk.

  In the National School Lunch Program, however, milk is the only beverage
that must be offered to children. A section 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, according to the lawsuit, the program that
serves free meals to needy children won't reimburse schools for a nondairy
alternative to milk unless the substitution is requested by a doctor.

  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, ages 22 to 36,
on nearly milk-free diets. And his five grandchildren seldom touch dairy
foods.

  Outside the family, Campbell faces more resistance to his diet ideas, but
that hasn't shaken his conviction that people 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 created award-winning school lunch programs that don't include
meat or dairy foods. But she admits that kids still like the diet they're
used to. And even Campbell admits his grandkids slip every now and then.
"They're almost strictly vegetarian," he says, "except a couple who cheat a
little on cheese once in a while."

  RELATED WEB SITES:

  Visit the following Web sites for a variety of views on dairy, nutrition,
and osteoporosis: www.newcenturynutrition.com, site of T. Colin Campbell's
Web zine; www.nal.usda.gov/fnic/dga, official dietary guidelines from the
USDA; www.pcrm.org, Web site of the Physicians Committee for Responsible
Medicine; www.dairyinfo.com and www.whymilk.com, Web sites that include
scientific information, sponsored by the dairy industry; and www.nof.org,
Web site of the National Osteoporosis Foundation.