ANTB15H3 Lecture Notes - Wild Type, Rickets, Osteomalacia

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8 Dec 2013
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Lactose- December 2, 2013- Lecture 11
Milk
Food Value: Lactose aspect of fresh milk valuable source of nutrition
Calcium for growth
Water Content: Milk provides extra fluid and is a water source
(particularly important in arid regions, e.g., desert nomads
Dietary Variation via the Animal Milked: Not Directly Interchangeable
All are MAMMALS; all have LACTOSE component, but in varying quantities
Unusual about human’s source of milk: high lactose
Calcium & Bone
20th century: the problem addressed through diet supplementation -
vitamin D added to milk
(OK as long as you are lactose tolerant…
-Vitamin D facilitates the absorption of calcium
- This supplement was added in the 1900s
Lactase Activity: Genetic Polymorphism
Suspected result of:
Single dominant mutation with high penetrance (high proportion of those
with the mutation showing signs/symptoms of lactase persistence)
Penetrance: You have the gene, but you don’t express it
What is Lactose Intolerance?
Inability to break down LACTOSE, the sugar found in dairy products (milk)
Inability stems from lack of LACTASE an enzyme produced by cells in the
small intestine
What does lactase do?
LACTASE breaks down milk sugar lactose into simpler forms of sugar
(glucose and galactose) which can then be absorbed into the bloodstream
Lactose Intolerance Symptoms
Considerable individual variation in lactose intolerance
Symptoms of abdominal pain, bloating gas (flatulence) and cramps, nausea,
diarrhea arise because:
Lactose Intolerance Symptoms
Lactose is not being broken down (into glucose) & is left unabsorbed
In the small intestines: lactose stimulates osmotic transport of water into the
small intestine (watery stool), and
When further passed along to COLON:
Lactose is fermented by action of colon bacteria
Leads to formation of gases methane and carbon dioxide
Cause the intestines to inflate & result = pain (cramps) and flatulence
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