What is lactase persistence?
It’s the ability to continue producing the enzyme, lactase after infancy, allowing adults to digest lactose in milk in adulthood
What is lactase and what does it do?
Lactose is an enzyme that breaks down lactose (milk sugar) into glucose and galactose, which can be absorbed into the bloodstream for energy
Why does blood glucose increase after milk consumption in a lactase persistent adult?
Because lactase breaks lactose into glucose and galactose, and the glucose enters the bloodstream showing active lactase function
Do all lactase persistent people have the same mutation?
No different mutations near the lactase gene evolved independently in European and African population (Maasai), an example of convergent evolution
Why did Europeans and Africans independently develop lactase persistence?
Because both groups domesticated dairy animals. Being able to digest milk offered a survival advantage when other food sources were scarce
What archeological evidence supports early milk consumption?
Fat residues found in ancient pottery fragments across Europe and Africa
How did dairy farming drive the spread of the lactase persistence mutation?
Dairy farming provided constant nutrition, individuals who could digest milk, survived, and reproduced more successfully spreading the trait
Why was consuming dairy a selective advantage?
Milk is calorie dense, rich in protein, fat, calcium, and other nutrients. In times of famine or food scarcity milk provided reliable sustenance and survival benefits
What is lactose intolerance?
It’s the inability to fully digest lactose due to low lactase enzyme levels. Un digested lactose is fermented by gut bacteria, causing gas, bloating, cramps, and diarrhea.
Why does lactose intolerance cause diarrhea?
Undigested lactose draws water into the intestines (osmotic effect) causing osmotic diarrhoea
Where does lactose come from?
Only from dairy products after weaning, most mammals stop producing lactase because they no longer consume milk
What is lactase non-persistent (LNP)
The ancestral human condition where lactase production drops after childhood leading to lactose intolerance in adults
What is lactase persistence (LP)?
A genetic mutation that keeps the lactase gene switched on into adulthood, allowing lifelong milk digestion
What causes lactase persistence genetically?
A mutation in a regulatory DNA region near the lactase gene that prevents it from turning off after weaning
Which is older, lactase, persistence, or non-persistence?
Lactase non-persistence is the original ancestral condition, lactase, persistence, evolved later
When and why did lactate persistence evolve?
Around 10,000 years ago after humans domesticated animals and began consuming milk regularly
Why didn’t all dairy herding populations develop lactase persistent
Some reduced lactose content in milk by processing it into yoghurt or cheese, making them mutation less necessary
What evolutionary benefits helped lactase persistence?
- Nutrient Access: milk provided calories proteins and fat
- Hydration: liable water source in hot, dry climates.
- Calcium + Vitamin D: improved bone health in low sunlight regions
- Growth boost: Milk raised IGF-1 levels, aiding growth & reproduction
What concept explains how lactase persistence evolved in separate regions?
Convergent evolution- the same trait evolved independently due to similar selective pressures
Is lactose intolerance a disease?
No lactase non-persistence is the normal biological condition for humans. Lactase persistence is the mutation.
Why should doctors use the term LNP instead of deficiency?
Because it’s not a disorder it’s the natural human state not a lack or disease
What common assumption in modern diets does lactase genetics challenge?
The idea that milk is essential for everyone; many populations evolved perfectly healthy without adult milk consumption
What is the difference between lactase persistence and lactose intolerance?
Lactase persistence: continued lactase production = digest milk = no symptoms
Lactose intolerance: decreased lactase = lactose undigested = fermentation = gas, cramps, diarrhoea
