Gene-Culture Coevolution Lactase Persistence Flashcards
What is lactose?
‘milk sugar’ - the prime source of carbohydrates for all young mammals
Why can’t lactose itself be absorbed by humans
lactose is a disaccharide and it must be hydrolyzed into two monosaccharides.
How is lactose digested in the body
with digestive enzyme Lactase: hydrolyzed into galactose and glucose
Why is lactase non-persistence the ancestral state for humans?
in the Palaeolithic there were no herds kept, so no milk was drank at older ages
Why do people that can’t digest lactose get gastrointestinal discomfort
Lactose gets fermented by bacteria in the colon, producing gases resulting in abdominal distention and flatulence (farting).
Lactose osmotically attracts fluid into the bowel causing diarrhea.
What regions of the world have the most lactose intolerance
East and southeast Asia, Africa, south America and the Arctic
T/F people are born with lactose intolerance
false, it occurs after childhood
The most common food allergy in infants and young children
Cow milk protein allergy
What makes milk allergy different from milk intolerance?
milk allergy - an immune response to milk proteins
intolerance - inability to digest lactose
What is lactase persistence and what determines it
- continued production of lactase after childhood
- is a genetically determined dominant trait
Lactase non-persistent phenotype is
homozygous - receives two copies of the low lactase-activity allele (ancestral allele)
Lactase persistent phenotype only needs
one copy of the high lactase-activity allele from their parents
Lactase persistence likely only reached appreciable levels in some populations in the last
7,000 years
how do we know that different lactase persistence gene variants produce the same phenotype?
The european gene variant is different from the lactase persistence gene variant in African cattle herders.
Pastoralism is
a way of life centered around herding and raising livestock
Explain the likeliest scenario of lactase persistence and animal domestication in the Neolithic period
Domestication of milk-producing animals > increased frequency of lactase persistence alleles > expansion of dairy herds > increased milk consumption > lactase persistence
Where in the world is milk consumption the highest?
North America, Australia, North Asia, Europe - correlates to lactose non-persistance map.
Fermented milk products have been produced since
10,000 BCE (before common era)
Why do some individuals lack the LP allele but can still tolerate milk products like hard cheese and yogurt?
lactose in fermented milk products is broken down by the lactic acid fermentation process, making it easier to digest
Milk contains highly bioavailable vitamins and minerals such as
- Vitamins A, D, B12
- riboflavin, calcium and phosphorus
Calcium is an important mineral for
skeletal integrity
Over 99% of body calcium is
calcium hydroxyapatite in bones and teeth
amount of calcium, lactose and Vita D in 250mL full fat homogenized cow milk
- 300mg
- 12g
- 100 IU (fortified)
Amount of calcium, lactose and vit D in 250mL raw milk
- 300mg
- 12g
- trace amounts
