Notes on Lactose Intolerance

Lactose Intolerance

• Lactose intolerance is suspected in Amy due to dairy-related sickness.
• It's caused by a deficiency in the lactase enzyme.
• Lactase's role: cleaving lactose into digestible sugars.

Lactase Enzyme

• Infants and young children usually express lactase in their small intestines.
• This is critical for infant nutrition since lactose is the main sugar in breast milk.
• Lactase levels often decrease with age in many people due to developmental changes.

Mechanism of Lactose Intolerance

• Reduced lactase allows lactose to pass uncleaved into the large intestine.
• Gut microbes ferment the lactose, producing acids and gases.
• This fermentation causes gastrointestinal distress.

Treatment

• Lactose intolerance can be treated with over-the-counter lactase supplements.
• These supplements temporarily increase enzyme levels in the gut before consuming lactose.
• Example: Amy takes a lactase supplement before eating ice cream and experiences no side effects.

Genetic Component

• Amy learns of a SNP associated with adult-onset lactose intolerance.
• The SNP is located upstream of the LCT gene.
• LCT gene encodes the lactase enzyme.
• This SNP is genotyped in many direct-to-consumer genetic testing kits.

Genetic Testing

• Amy gets tested to determine if her lactose intolerance has a genetic factor.
• She sends off her sample and awaits the results.