Milk discrimination

Recently I was having breakfast with a friend in Friendly’s, a restaurant chain of 380 restaurants in the north east of the USA that is especially proud of its 22 ice-cream flavors. I asked the waitress if I could please have lactose-free milk for my coffee. She looked surprised and said they didn’t have any. I said that a lot of Americans needed lactose-free milk and that therefore this might affect business.

Lactose is a dimer sugar; composed of two parts – glucose and galactose, stuck together to form this sugar unique to milk. Table sugar, sucrose, is a dimer of glucose and fructose. A specific enzyme is needed to break up these dimers so that the component sugars can then be absorbed and metabolized. For some reason, as early mammals developed mammary glands secreting milk to feed their babies, the sugar in the milk was lactose. An enzyme, lactase, had to have co-evolved to break up this unique dimer sugar. In wild creatures, energy conservation is of primary importance. So once the baby mammal is weaned it will no longer need the lactase enzyme and so the gene to make it is switched off.  Many thousands of years ago when all humans lived by hunting and gathering, babies were breast fed until about age three. They would then not encounter milk again and the lactase gene would have been switched off. 

Starting about eight thousand years ago, humans in some parts of the world domesticated cows or goats and developed dairy farming which often included drinking milk as adults. Once a dimer sugar is broken into the smaller components they can be quickly absorbed into the blood stream giving us our source of energy. But the dimer is too big to be absorbed and then as it carries down into the intestine it feeds excessive bacterial growth which leads to bloating, discomfort and in some cases more serious intestinal problems.

Mutations, that is changes in a gene, occur randomly and would also have occurred in the lactase gene. Only following adult consumption of milk would that mutation have been selected for, i.e. expand in the population.

For Europeans, this mutation for lactase persistence has been traced to 7,500 years ago, spreading amongst European milk drinkers ever since. A major study has been carried out around the world which found that lactose persistence correlates with people who originate from areas of a dairy tradition, e.g. Europe, the Middle East, India and East Africa. So called lactose intolerance correlates with people from areas of the world with no long history of dairy culture, e.g. West Africa, China and the Americas. 

The United States is a melting-pot of the world. It should not be a surprise therefore that recent estimates reckon that at least 30% of Americans are lactose intolerant. That’s about 90 million people. Grocery stores are waking up to this fact and lactose-free milk is now commonly available. I’ve often watched African Americans reaching for it on the supermarket shelf. In addition to the many Americans who originate from non-dairy cultures, the lactase gene can also switch off with advancing age as in my case. 

Back to the Friendly’s restaurant. I was settling into my black coffee when I looked up to find John Maguire the CEO of the entire Friendly’s chain, who I recognized from the company’s TV ads, standing in front of me. By extraordinary coincidence he just happened to be visiting this particular restaurant at that time and he wanted to understand my problem. I gave him a quickie version of what I’ve written above and we parted amicably. It wasn’t long before a jug of lactose-free milk was brought to the table, followed by the restaurant manager. He said that he wanted to understand it for himself. Explaining that I had done my PhD studying sugar metabolism and the switching on and off the genes involved, I told him of the different ethnicities that might well be lactose-intolerant. The manager’s face was a picture. He said that Friendly’s had recently concluded a major survey and could not understand why so few African Americans bought their ice-cream. I said : “Now you know”. 

 It is time that the majority white population of America became more understanding and sensitive on this issue. Leaving aside the simple idea of caring for the other, it could be financially important for restaurants, grocery stores, supermarkets and the makers and purveyors of ice-cream. Remember, you white Americans who are more often than not in decision-making positions: you are the mutants.