Why Can Many Northern Europeans Drink Milk, While Many East Asians Cannot?

The answer comes from a combination of genetics, history, and culture.

It is one of the best examples of gene culture coevolution, where human culture influences which genes become more common over time.

Let's go back about 10,000 years.

Around 10,000 years ago

Most adults probably stopped producing large amounts of lactase after childhood.

In other words, adult lactose intolerance was likely the normal condition for almost everyone.

People who continued making lactase throughout life were very rare.

Europe, the rise of dairy farming

About 7,000 to 9,000 years ago, farming spread across Europe.

People began raising:

• Cows

• Goats

• Sheep

They also started drinking fresh milk more often.

Every now and then, a child was born with a genetic change that allowed them to keep producing lactase as an adult.

This gave them several advantages.

They could:

• Drink fresh milk.

• Get extra calories.

• Consume more protein.

• Obtain calcium and other minerals.

• Stay hydrated when clean water was limited.

If these advantages helped people survive and raise children, they were more likely to pass this genetic trait to the next generation.

Over thousands of years, the trait became much more common.

Today, some of the highest rates of lactase persistence are found in:

• Sweden

• Denmark

• Ireland

• The Netherlands

• The United Kingdom

East Asia, a different history

Agriculture developed differently in much of East Asia.

People relied mainly on:

• Rice

• Millet

• Soybeans

• Vegetables

• Fish

Cattle and other farm animals were present, but they were usually more valuable for:

• Plowing fields

• Transportation

• Producing manure

• Meat

Fresh milk was not a major part of the adult diet.

Because adults rarely depended on milk, there was little advantage to continuing lactase production after childhood.

As a result, the original pattern remained common.

Most adults naturally produced less lactase as they grew older.

Neither pattern is better

One genetic pattern is not better than the other.

They are simply different adaptations to different lifestyles.

Northern Europe

Diet:

• Frequent fresh milk

• Dairy farming

Result:

• High rates of lactase persistence

Much of East Asia

Diet:

• Rice based agriculture

• Limited fresh dairy

Result:

• Lactase naturally declines after childhood

What about yogurt and cheese?

Even in populations with low lactase production, dairy was not completely absent.

Many people ate fermented dairy foods such as:

• Yogurt

• Kefir

• Certain cheeses

These foods contain less lactose because bacteria break down some of the lactose during fermentation.

As a result, they are often easier to digest than fresh milk.

Today the picture is different

People now live all over the world.

Someone with East Asian ancestry may grow up in Europe.

Someone with Dutch ancestry may grow up in Japan.

Our diets have changed much faster than our genes.

That is why lactose intolerance is now found in every country.

Imagine two villages

Picture two villages 8,000 years ago.

Village A

The villagers keep large dairy herds.

Fresh milk is part of everyday life.

People who can digest milk have access to extra food.

Their children inherit that advantage.

Over many generations, the ability to digest lactose becomes common.

Village B

The villagers grow rice.

Fresh milk is rarely consumed.

Whether someone can digest lactose makes very little difference.

The genetic change never becomes common.

Thousands of years later, the two populations have different rates of lactase persistence because they adapted to different ways of life.

Lactase persistence around the world

Approximate percentage of adults who continue producing lactase:

Population	Lactase persistence
Sweden	90 to 95%
Denmark	90 to 95%
The Netherlands	80 to 90%
United Kingdom	80 to 90%
Northern Germany	80 to 90%
Southern Europe	40 to 70%
India, varies by region	20 to 70%
Middle East, varies by region	20 to 80%
East Asia	5 to 20%
Southeast Asia	5 to 20%

These are broad estimates. There is considerable variation within countries and among different ethnic groups.

Key takeaway

The difference between Northern Europeans and many East Asian populations comes from thousands of years of different farming practices and diets. In places where fresh milk became an important food source, genetic changes that allowed lifelong lactase production became more common. In places where fresh dairy was not an important part of the diet, there was little reason for those genetic changes to spread. As a result, many adults continued the ancestral pattern of producing less lactase after childhood.