8.0 Lactose intolerance

lactose intolerance

the inability to digest the sugar in milk and dairy products due to insufficient levels of the enzyme lactase causing bloating, diarrhoea, gas and stomach pain after consuming dairy products

lactose intolerance occurs when the body cant break down or digest lactose, the sugar present in milk/dairy

this condition stems from a deificiency of the enzyme lactase, responsible for breaking down lactose into glucose and galactose

lactose

a disaccharide that is a major carbohydrate in the milk of most mammals

the gene responsible for the production of lactase enzyme is expressed in the entercytes lining of the small intestins

Babies and young children have a lot of lactase enzyme. After weaning the expression of the gene that produces lactase is down-regulated resulting in less lactase production. 

this is population specific and some population groups tend to have continued elevated lactase activity throughout their life.

This can be linked to population groups that consume the milk of domesticated cows and other mammals.

lactase production is reduced,

resulting in lactose not being broken down into absorbable glucose and galactose then the lactose moves further down the GI tract and into the colon

At this site the gut flora ferments the lactose into a mixture of hydrogen gas, carbon dioxide and methane resulting in bloating.

The fermentation process also results in production of short chain fatty acids which cannot be absorbed.

The resultant mix of lactose and its fermentation products increases osmotic pressure

increasing water influx into the colon leading to diarrhoea.

Why there is normally a down-regulation of the gene responsible for lactase production at ages 3-5 and how this varies with different populations.

because at the start of your life milk is all you ingets

after weaning the production of lactase need not be so high

caucasians have resistant lactases production into adulthood

think group historyically domesticated cows n whv n natural selection thinks lactase persistence whv

How an excess of lactose in the colon can result in excess gas (bloating) and diarrhoea.

when theres an underproduction of lactase the majority of lactose is not split and absorbed, as much as 75%

lactose continues down the GI tract into the colon where the gut flora microbes ferment the lactose into H_{2 (g)} and CO_{2 (g)} and CH_4(g) 

these gases contribute to the symptoms of gas and bloating

short chain fatty acids are also produced from lactose fermentation which remain in the lumen of the gut, not absorbed

unabsorbed lactose + fatty acid chains raise osmotic pressure, making water move INTO the bowels → diarrhoea

What is temporary lactose intolerance and how does this arise?

a result of infection or inflammation of the small intestine where the micro villi are flattened/ damaged (this is site of lactase production)

causes of lactose intolerance, other than a lack of lactase

• IBD

• coeliac disease- the immune system attached your own tissue when you eat gluten damaging yout small intestine so yout body cant properly intake nutrients

• bowel infections

• bowel surgery

• injury to the  bowel

symptoms occurs within a few horus of consumption

• flatulence (wind)

• diarrheoa

• bloated stomach

• stomahc cramps + pain

• stomach rumbling

• feleing sick

severity ot symptoms depends on the amound of lactose consumed

some people may be able to drink small glass of milk withotu triggering symptoms

testing for lactose intolerance

• eliminate lactose from diet to see if results improve

• hydrogen breath test where breath is tested for hydrogen to see how well lactose is digested

• blood test to measure blood glucose levels after drinking lactose solution- a lactose intoelrant person will show low glucose levels as lactose would not be broken down

most standard treatment for lactose intolerance

reducing lactose consumption

lactose supplements

wrk by replacing or supplementing the body’s defiecnt lactase enzymes

Clinical considerations include individual response,

as some people may still experience symptoms if the lactase dose is insufficient for the lactose load.

Lactase enzyme supplements are generally well-tolerated with few side effects.

. Rarely, patients might experience gastrointestinal upset, but this is usually mild. The effectiveness of lactase supplements can vary, so if symptoms persist, the dose may need adjustment.

further reading