The Power Of Milk
We know milk is good for our teeth. Milk and other dairy products are our primary dietary source of essential calcium. Calcium is the key ingredient in a mineral, known as hydroxyapatite, that strengthens tooth enamel as well as bones.
Dairy products—especially cheese—also contain casein, a type of protein. Research suggests that caseins, along with calcium, play an important role in stabilizing and repairing tooth enamel.
But how did we as humans figure out that milk was good for our teeth? How did we go from hunter/gatherers to dairy drinkers?
A Different Kind of Calculus?
Archaeologists and geneticists have been puzzling this question since it was revealed that the mutations which enable adults to drink milk are under the strongest selection of any in the human genome.
These mutations cause the intestinal enzyme lactase — which digests lactose milk sugar during infancy — to continue to be produced long after weaning. This lactase persistence is prevalent only in some populations around the world such as in Northern Europe. In most other people of the world, the lactose cannot be properly digested and the result is lactose intolerance.
Some dairy products such as yoghurt and cheese have had their lactose content reduced or removed through processing. If it is so easy to remove milk sugars, and the mutation is only required for drinking raw milk or whey — why is it under such strong selection?
An international team of researchers involving the Universities of York, Oklahoma and Copenhagen, and University College London (UCL) has shed new light on this puzzling question through an unusual source — investigations of calcified dental plaque on ancient human teeth.
The international team, reported in the journal Scientific Reports, provides the first direct evidence of milk drinking from an increasingly important archaeological reservoir — human dental calculus, you may know it as that hard stuff that builds up on your teeth if you don’t get to a dentist.
And while it may be a little gross, it has staying power.
A Favorable Mutation?
Using the latest mass spectrometry-based techniques, the team detected a milk protein, beta-lactoglobulin in ancient remains.
Lead author Jessica Hendy, from the University of York said: “It seemed too good to be true; beta-lactoglobulin is the dominant whey protein — the one used by bodybuilders to build muscle mass — and therefore the ideal marker for milk consumption. We kept finding sequences of beta-lactoglobulin and at first we thought it could be modern contamination. But we repeated the analysis several times, at three different laboratories in three different countries, each time finding the same results.”
Professor Dallas Swallow, from the Research Department of Genetics, Evolution and Environment at UCL, adds: “It is only within the last several thousand years that genetic mutations arose in Europe, East Africa, and the Arabian Peninsula that allowed lactase to persist into adulthood, a genetic trait that enables lifelong milk consumption.”
The new research provides direct protein evidence that cattle, sheep, and goat whey has been consumed by human populations for at least 5,000 years. Until now it has been difficult to investigate both human genetic milk adaptations and direct evidence of milk consumption at the same time, in part because milk preserves so poorly in the archaeological record.
“The discovery of milk proteins in human dental calculus will allow scientists to unite these lines of evidence and compare the genetic traits and cultural behaviors of specific individuals who lived thousands of years ago.
Professor Matthew Collins, of York’s Department of Archaeology, said: “Some of the findings were as we expected. For example, we did not find any evidence of milk protein in 19th century West African individuals from regions where dairying was uncommon. But we found widespread evidence for milk consumption at European sites spanning a period of 5,000 years.”
So, if you enjoy a cold glass of milk, thank your ancestors and their genetic adaptability, and drink up. Your teeth will thank you for it!