Harvard nutritionists David Ludwig and Walter Willett argue that milk should be a dietary choice, not a nutritional requirement.
For years, the government and various medical bodies have recommended that all Americans consume milk daily as part of a healthy diet. In fact, according to Harvard pediatrics professor David Ludwig, MD, PhD, this recommendation is “perhaps the most prevailing advice given to the American public about diet in the last half century.”
As it turns out, though, the advice may be misleading. At least that’s what Ludwig, director of the New Balance Foundation Obesity Prevention Center, and Walter Willett, MD, DrPH, Harvard School of Public Health nutrition department chair, argue. Last summer, the two published a joint commentary in JAMA Pediatrics calling on their peers to “reconsider the role of cow’s milk in human nutrition.”
That these two prominent nutritionists would take aim and fire at a beverage as sacrosanct as milk was a shock. Even more so when you consider that Willett is the grandson of a dairy farmer and the single-most-cited nutritionist in the world, according to the Boston Globe.
Ludwig is equally formidable as the founding director of the Optimal Weight for Life program at Boston Children’s Hospital, one of the country’s oldest and largest clinics for the treatment of obese kids.
Together, the Harvard heavyweights chastised the U.S. Department of Agriculture (USDA) and the American Academy of Pediatrics for encouraging people to consume up to 3 cups of milk daily. “Humans have no nutritional requirement for animal milk,” they write.
Even more concerning, they say, is that the USDA pushes low-fat milk on school kids under the guise of preventing childhood obesity. There is no proof that switching from whole to low-fat milk helps people lose weight, says Ludwig: “In fact, there is evidence to the contrary.”
Neither expert is saying that milk lovers need to go on the wagon. They do argue, though, that milk should be recast as a dietary choice, not a requirement. “Whether or not a person chooses to drink milk should be a personal preference,” says Ludwig, “not a government recommendation.”
Joe Keon, PhD, a nutrition expert and author of Whitewash: The Disturbing Truth About Cow’s Milk and Your Health, agrees. We’ve taken the recommendation to drink milk as gospel for so long that few of us “stop to consider how unnatural the milk-drinking habit is,” he says.
To find out whether you’ve been misled by the prevailing milk advice, and to learn more about the beverage’s pros and cons, take the milk quiz below.
Take the Milk Quiz
1. True or False: Milk is an essential part of a healthy diet. (False)
If you said “true,” you may be conflating milk with calcium, which is easy to do thanks to advertising, but in reality the two are very different. Milk is a beverage. There is an industry behind it, and it’s a commodity. Calcium is a nutrient, and it is an essential part of a healthy diet. Milk has calcium but it’s hardly the only source — and some would argue it’s far from the best source.
Plants are abundant in calcium, especially dark, leafy greens. Calcium-rich foods include seaweed, arugula, collards, spinach, and mustard greens. And don’t forget that the body needs additional nutrients to move calcium into bone, such as vitamins C and K, potassium, and magnesium. A healthy mix of plant foods can handily deliver all of the above.
Plants are by far the best source of calcium for the whopping 25 percent of Americans with lactose maldigestion, meaning their bodies lack the ability to digest the milk sugar lactose. It’s important to remember that humans met their nutritional needs for calcium for millennia before dairy entered the dietary picture. (For a list of calcium-rich foods, see “Calcium Does a Body Good” below. For information on milk substitutes, see “The New Moo: Milk Alternatives“.)
2. True or False: You need lots and lots of calcium. (False)
The USDA’s calcium recommendations likely are distorted by the industry, according to Ludwig and Willett. The 2010 Dietary Guidelines recommend 2 cups of milk daily for children age 2 to 3 years old, 2.5 for those from 4 to 8 years, and 3 for Americans older than 8. For most of us, that’s three servings of milk (or dairy) a day, all in service of hitting daily calcium intakes: 1,300 mg for teens, 1,000 mg for adults 50 and under, and 1,200 mg for those older than 50.
As far as Willett and Ludwig can tell, those numbers, which most nutritionists treat as gospel, are based on outdated studies that inflated the figures. “In an ideal world, the Dietary Guidelines would be the best summary of scientific evidence on diet and health,” says Willett. But unfortunately, he says, there are powerful forces in the meat and dairy industry that distort the truth.
If you consume a Western-style diet high in animal protein, you should increase the amount of calcium you consume because — in sharp contrast to advertising’s promises of milk’s bone-building power — animal protein can sap calcium from bone. The United States, which has one of the world’s highest calcium intakes, also has one of the world’s highest bone-fracture rates.
Keeping bones vital is one of the key reasons to choose calcium-rich plant foods. Calcium from plants sidesteps the animal-protein issue, freeing your bones to absorb as much of the mineral as possible. “The notion that everyone needs 3 cups of milk a day to keep their bones from crumbling is just not true,” Ludwig says.
3. True or False: If you drink milk, you won’t get osteoporosis. (False)
Osteoporosis has nothing to do with milk. It’s actually a bone-thinning disease tied to calcium depletion. The condition affects 10 million Americans, and another 40 million have its precursor, osteopenia. As mentioned, even though the United States is one of the top dairy consumers in the world, it still has one of the highest rates of bone fractures. And bone breakage is actually lowest in countries that consume small amounts of milk.
Ample research shows osteoporosis is about genetics and lifestyle, not milk consumption. In one of the most rigorous studies, researchers tracked nearly 78,000 women for 12 years and found that those who drank two or more glasses of milk daily broke more bones than women who rarely consumed milk.
The list of factors that steal calcium from bones reads like a description of the standard American diet: excess sodium, alcohol, animal protein, and caffeine.
The best way to prevent osteoporosis is to get plenty of weight-bearing exercise, like walking and yoga, and to eat a nutrient-dense, plant-rich diet. In 2003, when researchers from Brigham and Women’s Hospital and Harvard Medical School looked at what more than 72,000 postmenopausal women ate over almost two decades, they didn’t find a significant link between milk and bone health. Instead, they discovered that those who ate the most vitamin D–rich fish (like salmon and sardines) lowered their hip-fracture risk by 33 percent.
4. True or False: All children need milk. (False)
Some children need milk. Which ones? Those with a poor diet. “For these kids, milk may be the highest-quality food they consume in a day,” says Ludwig.
But Ludwig and Willett question the USDA’s scientific rationale for encouraging schools to replace whole milk with flavored and sweetened low-fat milk. A serving of whole milk has about 12 grams of sugar; a serving of flavored milk can contain some 25 grams.
Trading fat for sugar makes zero sense, says Ludwig. Data shows cutting fat doesn’t lead to weight loss, especially when it comes to milk. Specifically, a 2005 study published in the Archives of Pediatrics & Adolescent Medicine found that the more low-fat and skim milk children drank, the more likely they were to gain weight.
The reason, says Ludwig, is that fat is more filling than sugar. People on a low-fat diet feel hungry and, more often than not, snack on refined carbs. He uses the example of a kid who habitually comes home from school and has a glass of whole milk and two cookies. If low-fat milk is swapped into the picture, the child is less likely to feel full and more likely to reach for an extra cookie. At the end of the day, that third cookie is a greater health problem than the fat found in whole milk. “We know sugar and refined grains cause weight gain,” says Ludwig. “Low-fat milk sweetened with 3 or more teaspoons of sugar is a lose-lose.”
5. True or False: Organic milk is healthier than conventional milk. (True)
Organic milk is healthier than conventional milk because organic farmers do not use antibiotics, feed laden with synthetic pesticides, and growth hormones. Plus, by law, organic cows must get some nourishment from grass, which is high in omega-3 fatty acids and CLA, an immune-enhancing fatty acid. Those nutrients end up in the milk. But all organic milk is not created equal.
Soaring demand has created industrial-size organic dairies where the line between conventional and organic practices gets blurred, explains Mark Kastel, director of the Organic Integrity Project at the Cornucopia Institute, a Wisconsin-based nonprofit promoting economic justice for family-scale farms. If you want to know whether the dairy that produces your milk is on the up-and-up, check out the Cornucopia Institute’s website (www.cornucopia.org) and click on the link marked “Dairy Scorecard.” The institute has rated the nation’s dairies using metrics like health and longevity of the cows and ratio of cows to acres of pasture. Look to see how well your dairy scores. Simply buying organic is not enough, says Kastel: “You want to buy milk from cows with names, not numbers.”
The answer depends on your diet. If your idea of breakfast, lunch, and dinner is a Cronut, potato chips, and frozen pizza, the answer to the question is “true.” Milk is better for you than junk food.
If your diet contains plenty of vegetables, nuts, seeds, and fish, you may not need — or want — milk in your diet. Ludwig doesn’t mince words: “For people who eat a high-quality diet, following the USDA’s guidelines for milk could increase their risk of disease and possibly some types of cancer.”
The link between milk and cancer is well established and multifaceted. For starters, cow’s milk is high in insulin-like growth factor 1 (IGF-1), a hormone similar to insulin that plays a big role in helping kids grow, because milk is designed to help calves grow. In humans, particularly children, IGF-1 encourages cell growth and discourages cell death. Studies show adults with high levels of IGF-1 are at increased risk of prostate, breast, and colon cancers. Some of this risk may be incurred during childhood.
Complicating matters is the fact that the industry breeds cows to have higher IGF-1 levels because those cows produce more milk. Even worse, milk from cows given recombinant bovine growth hormone (rbGH) has significantly higher levels of IGF-1 than milk from cows not treated with rbGH.
Another factor that increases the risk of cancer is estrogen. Milk has 60 different naturally occurring hormones; estrogen is predominant. That’s problematic for people with estrogen-sensitive disease, like breast, uterus, or ovarian cancer. Much of a woman’s risk of developing these cancers hinges on her lifetime exposure to estrogen. “Considering the fact that lifetime estrogen exposure is one of the primary risk factors for breast cancer,” says nutrition expert Keon, “the influence of dairy is no small thing.”
Part of the problem seems to be modern dairy practices. Dairy cows — both conventionally and organically raised — are now commonly milked as many as 305 days a year; for much of that time they are pregnant. Milk from a cow in late-stage pregnancy has up to 33 times more estrogen than milk from a cow that’s not pregnant. And cow estrogen is 100,000 times more potent than environmental estrogens, according to Ganmaa -Davaasambuu, PhD, a Harvard School of Public Health scientist. In other words, your daily latte could harbor much more danger than your plastic water bottle.
In sum, Willett says, “The hormones in milk do raise concerns. So far, the evidence of increased risk is substantial for prostate cancer, but we need more data on other cancers, particularly in relationship to dairy intake during childhood.”