Link Between Milk Consumption and Human Growth Explored
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Chapter 1: The Impact of Dairy on Human Development
Growing up, I had a babysitter who was lactose intolerant. Although I can’t recall her name or face, I vividly remember offering her a spoonful of my favorite ice cream, Rocky Road. She declined, explaining that she couldn’t eat it, a concept that baffled me at the time. The idea of living without ice cream seemed like a cruel fate.
Years later, I suspected I might be lactose intolerant as well. When I mentioned this to my mom, she agreed and reminded me how often she urged my siblings and me to drink milk for strong bones, despite my frequent complaints about stomach aches. This led me to ponder the connection between lactose and our bodies, especially as I realized how challenging it would be to eliminate dairy from my diet. Cheese, in particular, is a temptation I struggle to resist.
What exactly is the effect of lactose on our physiology, and why can some people digest it while others cannot? Additionally, why is dairy so integral to the diets of certain cultures, like those in the West, while it is less common in regions like Asia? Fortunately, researchers have sought to answer these questions.
The Research Findings
A recent study spearheaded by Jay Stock, a professor of biological anthropology at Western University, aimed to understand variations in human body size and composition through time and across geographical regions. Their findings were published in the journal PNAS on January 17, 2023.
The research team analyzed 3,507 skeletons from 366 archaeological sites spanning 25,000 years. They discovered that between 7,000 and 2,000 years ago, certain populations developed genetic adaptations that enabled them to continue digesting milk into adulthood, a phenomenon termed “lactose persistence.”
The Historical Context
Our ancient ancestors in Northeastern Africa and Eurasia began to experience a reduction in body size and mass around 15,000 to 10,000 years ago. This timeframe coincides with the agricultural revolution, during which farming practices emerged independently in various regions. As these migrating farmers moved, they introduced dairy livestock and crops to Eurasia.
However, the agricultural crops from western Asia struggled to thrive in the cooler northern European climates. The researchers suggest this shift may have prompted our ancestors to transition from yogurt and cheese production to consuming raw milk, which contains significantly higher lactose levels.
Higher lactose intake provided additional energy to those who could digest it effectively. The study indicated that skeletons displaying genetic markers for milk consumption also exhibited increased body mass and height. As Stock noted in an article by Phys.Org, “That process of evolution led to the pattern of lactose intolerance that we see today, where people in northern Europe are more often lactose tolerant than those in southern Europe.”
Interestingly, lactose tolerance has also evolved independently in populations in Asia and Africa, despite the predominance of European skeletons in this research due to the abundance of archaeological sites in that region.
Moreover, the research suggests that the decrease in body size and overall health may have occurred before and after the onset of the agricultural revolution. Stock posits that climate changes during the Last Glacial Maximum played a significant role in limiting food diversity and abundance, which may have catalyzed the shift toward agriculture.
A Shift in Perspective
I find Stock’s research compelling for two main reasons. First, I am intrigued by the distribution of the lactose tolerance gene. Despite thousands of years passing, many individuals still lack this ability or display sensitivity to lactose. While it is logical that the gene would proliferate in cultures with a strong dairy presence, I am curious why it hasn’t spread more widely over the millennia.
Secondly, it’s fascinating how a seemingly minor dietary change can have lasting repercussions over thousands of years. We often cannot foresee which small adjustments in habits or perspectives will significantly influence future generations. Changes in diet, for instance, can alter our physicality and behaviors in ways that persist long after we are gone.
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