Extraordinary Dairy: What you Might Not Have Known About Lactose Intolerance


Alexandra-Sasha Giedd

Photo by Stefan Kühn, via Wikimedia Commons

Photo by Stefan Kühn, via Wikimedia Commons

Got milk?

Do you know anyone who is lactose intolerant? Chances are, you probably do! That’s because most people are at least slightly lactose intolerant, or may become so with age. But what exactly is lactose intolerance, and why does it seem to affect everyone differently? To find the answer, we can take a look into our genetic makeup and evolutionary history. But first, lets learn a little more about what lactose is and how it interacts with out body.

So, what exactly is lactose intolerance?

Lactose intolerance is characterized by the inability to digest lactose; a complex sugar found in most milk-based dairy products. If someone is lactose intolerant, it means they have a deficiency of an enzyme called lactase. This digestive enzyme functions in breaking down lactose into simpler sugars that the body can metabolize. Without the enzyme lactase, our bodies cannot fully digest all of the lactose we consume, which can result in symptoms very similar to food poisoning.

Lactose intolerance however, is not a disorder. It is simply a polygenic heritable trait, with a range of phenotypic variations; sort of like freckle count. For example, some people have many freckles, some have none, and some have a range of intermediate physicalities. Lactose intolerance is expressed much in the same way. Like freckles, lactose intolerance can also increase with age.

Interestingly enough, we are all born lactose tolerant. Infants are able to digest lactose, until about the age of three of four, when they are weaned and their first set of teeth manifest– a sign from their bodies that they are ready to rely on nourishment from solid foods. Throughout much of human history, after this stage, our intestines reduced the production of lactase, until the enzyme (along with our ability to digest milk without feeling sick) significantly diminished or even disappeared during adolescence.

 

Photo by Christian Bauer, via Wikimedia Commons.

Photo by Christian Bauer, via Wikimedia Commons.

The little gene that could

Around 10,000 years ago, something spectacular occurred. In the region of modern-day Turkey, a genetic mutation arose, switching the lactase producing gene permanently in the “on” position. Similar mutations appeared independently in the eastern regions of Africa and in the mediterranean. This meant that people carrying the “LAC-on” gene could drink milk their entire lives. These mutations spread through most of Europe, eastern Africa, and the Middle East, but never reached populations in the far East, Indonesia, southern Europe, western Africa, or the Americas. In fact, even today, the vast majority (about 65%) of the worlds population experiences some sort of reduced lactose tolerance throughout adulthood (although only 20% of people suffer from severe lactose intolerance).

What is most remarkable about this gene however, is the speed at which it spread through the human race. In just 10,000 years of evolutionary history, the proportion of humans carrying full lactose tolerance went from 0% to 35%, with an additional 45% of people expressing partial tolerance. One hypothesis as to why the “LAC-on” gene was able to spread so quickly was because in the eras before steady agriculture was established, milk provided an important year-round source of nutrition to those who could metabolize it. In fact, if you think about it, that’s just what milk is– a liquid multivitamin– created by all species of mammals to help nurture their young during the most essential stages of development. No wonder humans loved it too! Evolutionary biologists believe that our ancestors who were able to tap into this nutrition source may have had higher fitness than those who could not. Of course, this selective advantage would be most palpable in populations far away from the equator, where dynamic seasonal changes would make it challenging to eat a diverse year-round diet.

Photo by instant-ocean.deviantart.com, via Wikimedia Commons

Photo by instant-ocean.deviantart.com, via Wikimedia Commons

Milk Matters- Or Does it?

The good news however is that that long before 10,000 years ago, our bodies developed ways to get all the vitamins and nutrients that we need from other sources. For example, fish, nuts, seeds, and soybeans contain high amounts of Calcium, Vitamin D, and protein– the three main nutrients that milk has to offer. The largest nutritional concern that lactose intolerant people may face is meeting daily riboflavin requirements. However, this B-vitamin can be found in many leafy-green vegetables such as spinach, broccoli, bok choy, asparagus, rhubarb, and kale. Drinking milk is much more of a cultural convention than a necessity!

Furthermore, while many people may not be able to drink pure milk, most can eat dairy products further up the fermentation ladder – such as yogurt, butter, and cheese. This is because as milk ferments, the lactose becomes naturally broken down. Interestingly enough, historical evidence has shown that postheards from Africa and Eurasia were already fermenting milks, long before they became staple foods in Scandinavia and western Europe. Fermenting milks is not only a way to make dairy more palatable and easy to digest, it is also an important method of preserving it. In fact, most cultures around the world use dairy for traditional dishes, whether in the form of cheeses, yogurts, creams, or cooking oils. Some of the most widespread are Indian paneer (a cheese with a dense bread-like consistency, often used in dishes as a high-protein meat substitute), Ayib (a cheese-yogurt intermediate used as a cooling flavor for many spicy east-african dishes), and Paskha (a cheese-cake like dish served on Easter in Russia, Ukraine, Poland, and Lithuania).

Today, lactose intolerance is hardly a hindrance. There are so many milk-alternatives on the market, that anyone from moderately to severely lactose intolerant to vegan can enjoy an abundance of traditionally milk-based products. These options include soymilk, almond milk, rice milk, and many yogurt and cheese derivatives made from legumes. Scientists have even found ways to artificially add the lactase enzyme to milk, making some brands drinkable to all on the lactose intolerance spectrum!

So, next time you pour yourself a glass of milk or soymilk, or eat a scoop of ice cream or dairy-free sorbet (Have you tried it? It’s great!), just think back to your ancestors and thank them for being brave enough to milk that first cow. Without them, dairy products would certainly not be a part of our culinary culture the way they are today.

……….
Alexandra-Sasha Giedd is a student Duke University studying Biology and Cultural Anthropology.

So, what exactly is lactose intolerance?

Lactose intolerance is characterized by the inability to digest lactose; a complex sugar found in most milk-based dairy products. If someone is lactose intolerant, it means they have a deficiency of an enzyme called lactase. This digestive enzyme functions in breaking down lactose into simpler sugars that the body can metabolize. Without the enzyme lactase, our bodies cannot fully digest all of the lactose we consume, which can result in symptoms very similar to food poisoning.

Lactose intolerance however, is not a disorder. It is simply a polygenic heritable trait, with a range of phenotypic variations; sort of like freckle count. For example, some people have many freckles, some have none, and some have a range of intermediate physicalities. Lactose intolerance is expressed much in the same way. Like freckles, lactose intolerance can also increase with age.

Interestingly enough, we are all born lactose tolerant. Infants are able to digest lactose, until about the age of three of four, when they are weaned and their first set of teeth manifest– a sign from their bodies that they are ready to rely on nourishment from solid foods. Throughout much of human history, after this stage, our intestines reduced the production of lactase, until the enzyme (along with our ability to digest milk without feeling sick) significantly diminished or even disappeared during adolescence.

The little gene that could

Around 10,000 years ago, something spectacular occurred. In the region of modern-day Turkey, a genetic mutation arose, switching the lactase producing gene permanently in the “on” position. Similar mutations appeared independently in the eastern regions of Africa and in the mediterranean. This meant that people carrying the “LAC-on” gene could drink milk their entire lives. These mutations spread through most of Europe, eastern Africa, and the Middle East, but never reached populations in the far East, Indonesia, southern Europe, western Africa, or the Americas. In fact, even today, the vast majority (about 65%) of the worlds population experiences some sort of reduced lactose tolerance throughout adulthood (although only 20% of people suffer from severe lactose intolerance).

What is most remarkable about this gene however, is the speed at which it spread through the human race. In just 10,000 years of evolutionary history, the proportion of humans carrying full lactose tolerance went from 0% to 35%, with an additional 45% of people expressing partial tolerance. One hypothesis as to why the “LAC-on” gene was able to spread so quickly was because in the eras before steady agriculture was established, milk provided an important year-round source of nutrition to those who could metabolize it. In fact, if you think about it, that’s just what milk is– a liquid multivitamin– created by all species of mammals to help nurture their young during the most essential stages of development. No wonder humans loved it too! Evolutionary biologists believe that our ancestors who were able to tap into this nutrition source may have had higher fitness than those who could not. Of course, this selective advantage would be most palpable in populations far away from the equator, where dynamic seasonal changes would make it challenging to eat a diverse year-round diet.

Milk Matters- Or Does it?

The good news however is that that long before 10,000 years ago, our bodies developed ways to get all the vitamins and nutrients that we need from other sources. For example, fish, nuts, seeds, and soybeans contain high amounts of Calcium, Vitamin D, and protein– the three main nutrients that milk has to offer. The largest nutritional concern that lactose intolerant people may face is meeting daily riboflavin requirements. However, this B-vitamin can be found in many leafy-green vegetables such as spinach, broccoli, bok choy, asparagus, rhubarb, and kale. Drinking milk is much more of a cultural convention than a necessity!

Furthermore, while many people may not be able to drink pure milk, most can eat dairy products further up the fermentation ladder – such as yogurt, butter, and cheese. This is because as milk ferments, the lactose becomes naturally broken down. Interestingly enough, historical evidence has shown that postheards from Africa and Eurasia were already fermenting milks, long before they became staple foods in Scandinavia and western Europe. Fermenting milks is not only a way to make dairy more palatable and easy to digest, it is also an important method of preserving it. In fact, most cultures around the world use dairy for traditional dishes, whether in the form of cheeses, yogurts, creams, or cooking oils. Some of the most widespread are Indian paneer (a cheese with a dense bread-like consistency, often used in dishes as a high-protein meat substitute), Ayib (a cheese-yogurt intermediate used as a cooling flavor for many spicy east-african dishes), and Paskha (a cheese-cake like dish served on Easter in Russia, Ukraine, Poland, and Lithuania).

Today, lactose intolerance is hardly a hindrance. There are so many milk-alternatives on the market, that anyone from moderately to severely lactose intolerant to vegan can enjoy an abundance of traditionally milk-based products. These options include soymilk, almond milk, rice milk, and many yogurt and cheese derivatives made from legumes. Scientists have even found ways to artificially add the lactase enzyme to milk, making some brands drinkable to all on the lactose intolerance spectrum!

So, next time you pour yourself a glass of milk or soymilk, or eat a scoop of ice cream or dairy-free sorbet (Have you tried it? It’s great!), just think back to your ancestors and thank them for being brave enough to milk that first cow. Without them, dairy products would certainly not be a part of our culinary culture the way they are today.

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