Trust your guts! Why a billion Chinese drinking milk is not the nightmare some predict
In 2006, Chinese premier Wen Jiabao shared his dream. It was a future in which every Chinese person would have a pint of milk each day. Wen’s proposal met with skepticism from some quarters. Quartz, for instance, declared the plan crazy. Ninety percent of all Chinese, the author wrote, are “lactose malabsorbers.” It thus follows that they should avoid milk or risk turning China into the land of a billion farts.
Recent studies, however, suggest that Premier Wen may actually be on to something. Most people in China can probably safely drink milk.
To be fair, Quartz is right about one thing. Most Chinese are lactose malabsorbers. But the journalist should have asked: What is lactose malabsorption, and how is it different from lactose intolerant?
In layman’s terms, a lactose mal-absorber is someone who has flunked a hydrogen breath test. The test measures not how well you digest actual milk, but whether your small intestine can absorb an enormous amount of lactose, the complex sugars in milk. To assess this, people in a study will typically fast overnight. The next morning, they gulp down 50 milliliters of a lactose solution. Then someone measures the hydrogen in their breath at regular intervals over several hours. If there is a lot of hydrogen in your breath, this means that you don’t produce enough lactase to break down the milk sugars. The undigested sugars sit in your colon, attracting carbohydrate-greedy bacteria. Once bacteria devour sugars, they give off hydrogen.
Like the S.A.T., the hydrogen breath test can only tell you so much. It doesn’t predict how well someone handles a normal amount of milk in the real world. The average American currently drinks 200 ml of milk a day, or less than a cup. The lactose solution in a typical breath test, however, supplies the amount of lactose in four cups of milk. Think of the last time you had a quart of milk on an empty stomach – and in the space of ten minutes. Now remember the S.A.T. vocabulary section. How often do you use ‘somnambulist’?
Plenty of people pass the hydrogen breath test with flying colors, but have tummy troubles after drinking milk. The reverse is also true. According to the National Institute of Health, most mal-absorbers can tolerate a cup of milk each day without symptoms.
A more recent study of Chinese adds grist to the mill. The researchers were careful to distinguish between lactose malabsorption and actual symptoms of lactose intolerance, such as diarrhea, cramping, and flatulence. They also experimented with giving their subjects different amounts of lactose. They found that 97% of healthy Chinese tolerated 10 grams of lactose (a cup of milk has about 12 grams). Seventy-eight percent had no issues with 20 grams. When they gave 40 grams to the subjects, though, the picture changed. Sixty-eight percent experienced symptoms.
Researchers have also discovered that people tolerate milk better than lactose solutions. In fact, Quartz cited a study of school children in Mainland China, which showed exactly this. After swallowing the lactose solution, many youngsters had cramps and flatulence. A few got the runs. When the children received the same dose of lactose as powdered milk, however, the symptoms decreased sharply. A team of researchers working in Hong Kong noticed the same thing in 1992. They suggested ditching the lactose solutions.
There is admittedly a lot we don’t know about lactose intolerance in China. Maybe one day we will know how many people in China can’t drink milk. Until then, Chinese will just have to trust their guts.