About Lactose

Lactose, or "Milk Sugar", is a two sugar molecule (disaccharide). Lactose consists of one molecule each, of Glucose and Galactose bound together. Lactose is an important Nutrient found in Milk but some people cannot digest it effectively.

Lactase Enzyme

Lactase is an Enzyme located in the Small Intestine which breaks the bond between the two sugars in Lactose. By breaking this bond, the Lactase Enzyme turns the nonabsorbable Lactose, into two, Absorbable sugars, Glucose and Galactose.
Lactose Intolerance and Hypolactasia
Some people cannot properly digest Lactose because they have problems making the enzyme, Lactase, necessary to break the bond between the two sugars.

Patients with low levels of Lactase activity, or Hypolactasia, cannot appropriately digest Lactose. Depending on the extent of enzyme activity, Hypolactasia can be Asymptomatic or patients can suffer from Symptoms of Lactose Maldigestion.


  • Congenital Alactasia - Complete Loss of Lactase Enzyme (Rare)
  • Loss of Lactase Enzyme after Weaning
  • Secondary Lactase Enzyme Loss due to Small Bowel Damage - Celiac Disease, Crohn's Disease Intestinal Infection, Hormone Imbalance

Symptoms of Lactose Intolerance

Lactose Intolerance Symptoms are primarily caused by the undigested Lactose entering the Colon and can be used as a food source by the Bacteria that reside there. The Bacteria Ferment the Lactose, producing Gas in the process. Excess Gas causes Symptoms such as:
Abdominal Pain
Borborygmus / Borborygmi
Flatulence (Farting)

Undigested Lactose can also cause extra water to enter the Intestine, and cause:
Intestinal Expansion
Increased Intestinal Motility (movement).

Where is Lactose Found?

Lactose can be used as a Filler, Stabilizer, and Texture Improving Agent in many foods and beverages. Lactose can be found in some surprising places, including:
  • Beer (some types)
  • Biscuits
  • Breads
  • Cakes
  • Custards
  • Doughnuts
  • Icing / Frosting
  • Many Medicines contain Lactose as a filler.
  • Lactose is a component of Milk from animals.
  • Pickles
  • Sausage
  • Whey

Lactose and IBD

Many patients with Crohn's Disease can consume milk products without feeling effects of Dairy Sensitivity immediately. However, exacerbation of Crohn's Symptoms may take many weeks of repeated Dairy consumption before effects are finally felt.

One study reported 70% Patients with Crohn's disease had a positive Lactose malabsorption test when 25 grams of Lactose was consumed, while only 30% of Controls had a positive test result.

Patients with Crohn's Disease have a greater risk for positive Lactose malabsorption testing depending on location of the disease. The authors caution that a positive Lactose malabsorption test may instead be due to bacterial overgrowth.
Proximal Small Bowel (Duodenum, Jejunum) 100%
Terminal Ileum 68.1%
Terminal Ileum / Colon 54.9%
Colon 43.5%


Lember M. Hypolactasia: a common enzyme deficiency leading to lactose malabsorption and intolerance. Polskie Archiwum Medycyny Wewnetrznej. 2012; 122(Suppl1): 60-64.

Mattar R, Ferraz de Campos Mazo D, Carrilho FJ. Lactose intolerance: diagnosis, genetic, and clinical factors. Clin Exp Gastroenterol. 2012; 5: 113-121.

Matthews SB, Waud JP, Roberts AG, Campbell AK. Systemic lactose intolerance: a new perspective on an old problem. Postgrad Med J. 2005; 81: 167-173.

"Lactose." PubChem. Accessed January 2013.

Nickerson TA. Symposium: Use of milk derivatives in other foods. Use of milk derivative, lactose, in other foods. Journal of Dairy Science. 1976; 59(3): 581-587. http://download.journals.elsevierhea...0276842427.pdf

Mishkin B, Yalovsky M, Mishkin S. Increased prevalence of lactose malabsorption in Crohn's disease patients at low risk for lactose malabsorption based on ethnic origin. Am J Gastroenterol. 1997; 92(7): 1148-1153.

Mishkin S. Dairy sensitivity, lactose malabsorption, and elimination diets in inflammatory bowel disease. Am J Clin Nutr. 1997; 65(2): 564-567.

Popular Threads Discussing Lactose

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01-22-2013, 02:10 AM   #1
Jennifer's Avatar
Join Date: Jan 2010
Location: California
THANK YOU! Now I'll never have to look it up again.
Diagnosis: Crohn's in 1991 at age 9
Surgeries: 1 Small Bowel Resection in 1999; Central IV in 1991-92
Meds for CD: 6MP 75mg
Things I take: Tenormin 25mg (PVCs and Tachycardia), Junel (endometriosis), Tylenol 3 (Osteoarthritis), Zantac 150mg 2/day (acid reflux), Klonopin 1mg (Panic Disorder), Imitrex 25mg (migraines), Zofran 8mg (nausea)
Currently in: REMISSION Thought it was a flare but it's just scar tissue from my resection. Dealing with a stricture. Remission from my resection, 19 years and counting.
01-22-2013, 02:20 AM   #2
Judith's Avatar
Join Date: Mar 2012
Location: California
I appreciate it Thanks! Julie345 noticed it was missing from the Wiki. Thank you Julie, nice catch!
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