With popular opinion swinging against dairy products, Crave asks if we should be drinking the white stuff.
Text by Tiffany Chan, photo by clickphotos, illustrations by Yanny Cheng
Until fairly recently, dairy was not a regular part of the typical Hong Kong diet. Who’s ever heard of cheese with dan dan noodles or dim sum? But visit any supermarket today and the shelves are lined with a dizzying array of dairy products. The mainland milk market has also flourished since Chinese Premier Wen Jiabao joined the pro-dairy campaign during a 2006 visit to a Chongqing dairy farm, when he proclaimed: “I have a dream that every Chinese, especially children, could have 0.5 kilograms of dairy products every day.”
But is he right? While dairy products are foreign to much of Asia, Africa and South America, they have long been an important part of diets in the West. For decades, consumers in the US have been urged to drink three glasses of milk a day, backed by the ubiquitous “Got Milk” campaign featuring 300 or so celebrities from Taylor Swift to David Beckham wearing thick milk moustaches. Milk was said to provide the calcium needed for strong bones in children and to prevent fractures and osteoporosis in old age.
According to Dr Gregory Miller, vice-president of the US National Dairy Council, “Our ancestors identified cow’s milk as one of the most nutritious foods centuries ago. To this day, milk is still one of the most nutrient-rich, wholesome foods. Dairy products such as milk, cheese and yogurt are rich in nutrients that are essential for good bone health, including calcium, protein, vitamin D, potassium, phosphorus and other micronutrients and macronutrients.”
But it’s not for everybody. According to the US National Institute of Health, more than 65 per cent of the world’s population is lactose intolerant after infancy, meaning their bodies do not produce enough of a digestive enzyme called lactase to break down the lactose found in dairy products. In East Asia, this figure rises to a staggering 90 per cent of adults who haven’t “got milk”.
But are those who experience cramps, bloating and diarrhoea after eating dairy really more frail and susceptible to bone fractures? In recent years, a number of studies have challenged the importance of dairy when it comes to health. After all, what other species drinks milk produced by another animal? And how natural is it to consume dairy when most people are lactose intolerant?
One of the world’s most influential nutritionists is Dr Walter Willett, the head of nutrition at Harvard’s School of Public Health. Despite coming from a long line of dairy farmers, he argues the evidence for dairy consumption is weak.
“The evidence is minimal and we have known for a long time that fracture rates are actually highest in countries with the highest milk intake,” he says.
In 2013, Dr Willett and Dr David Ludwig, also a professor of nutrition at Harvard School of Public Health, published a detailed review questioning the necessity of dairy consumption.
“Humans have no nutritional requirement for animal milk, an evolutionarily recent addition to diet,” they write. “Anatomically modern humans presumably achieved adequate nutrition for millennia before domestication of dairy animals, and many populations throughout the world today consume little to no milk for biological reasons [lactase deficiency], lack of availability or cultural preferences. Adequate dietary calcium of bone health, often cited as the primary rationale for high intakes of milk, can be obtained from many other sources.”
Indeed, milk is designed to foster the growth of young grazing animals – of calves, not human babies – and only became part of the human diet with the advent of animal domestication about 9,000 years ago.
For those who do not, or functionally cannot, consume dairy, the nutritional benefits of milk can be found elsewhere.
“It is possible to have adequate intake of calcium without milk, although this does require a high-quality diet [including green leafy vegetables, legumes, nuts, seeds and adequate protein]; consultation with a paediatrician is desirable if no dairy products are consumed,” Willett says.
At the University of Hong Kong, Dr Wang Ming-fu, associate professor at the School of Biological Sciences, backs up this finding.
“Dairy products contain calcium, but it is not much higher than in other food products,” he says. “We still can get a good amount of calcium from our regular diets, such as from vegetables, even from drinking water. We also have plenty of health supplements in the form of pills or capsules containing high amount of calcium, which can be taken regularly.”
However, Miller argues that is it uncommon to find the same level of calcium in non-dairy products. “It’s difficult to find foods that naturally provide the same nutritional package as one glass of milk [vitamins A and D are the only added nutrients, everything else comes straight from Mother Nature]. For example, to get the same 300mg of calcium found in an 240ml glass of cow’s milk, you’d need to eat about 10 cups of raw spinach.”
His opinion is not fashionable. Predictably, the internet is rife with reports claiming to bust the “milk myth” as the online pendulum of popular opinion swings against dairy products. But milk is not all “bad”.
Willett explains that while we may not benefit from three glasses a day, dairy is by no means toxic. “Importantly, this is not an all-or-nothing issue: calcium is an essential nutrient and milk has a high content,” he says. “This also depends on age and the benefit of milk also depends on the quality of the rest of the diet. However, for adults, the evidence does not support that dairy consumption above one serving per day adds benefit, and even the benefit of one serving per day is not clear. Children do need extra calcium because they are growing, but dairy intake beyond one or two servings a day is not necessary.”
So the dairy story is complex and, of course, far from over. “Nutritional science is continually evolving and new mechanisms connecting diet and disease risk are discovered on an ongoing basis,” Miller says. “Conflicting reports can create confusion … it’s important to look at the big picture. The newest study of the day is often not enough to make sweeping changes to diet or lifestyle practices.”
Different breeds of dairy cattle produce milk of varied composition and fat content. Fat content in milk is usually three to five per cent, but Jersey and Guernsey breeds give milk of higher fat and protein content. The milk of Zebu cows can contain up to seven per cent fat.
Mastitis is an inflammation of one or more quarters of the udder usually caused by bacterial infection. In mastitic milk, yields are reduced and contaminated with antibiotics. Both fat and solids-not-fat content (SNF) – vitamins, minerals, protein, lactose contents that are not fat – are also reduced.
Naturally, the fat and SNF content of milk is reduced if the cows are underfed. But underfeeding affects SNF content more rapidly than fat; SNF content falls when cows are fed a low-energy diet. Fat content is more influenced by the cow’s fibre intake.
Fat content decreases by about 0.02 per cent per lactation and SNF content decreases much more rapidly as cows grow older.
Stage of lactation
Milk content varies with the cow’s stage of lactation. SNF content is typically highest in the first two to three weeks of lactation, then decreases slightly. Fat content is highest after calving then dips for 10 to 12 weeks, after which it may rise again until the end of lactation.
Yields are affected by the interval between milking. Twelve-hour intervals give the highest yields, however, for practical reasons most farms have intervals of eight hours during the day and 16 hours overnight. This may have minimal effect if the highest yielding cows are milked first in the morning and last in the afternoon.
While the first milk drawn from the udder is low in fat, the last milk, called strippings, is high in fat. To preserve the fat content, the residue milk from the last milking is picked up later. Milk must be mixed thoroughly for fat to be evenly distributed.