Dennis B. Kottler, MD

Westlake Village, CA

Appointments:   818-991-8376 


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(Material which is speculation is in GREEN)

Lactose Intolerance (LI) is the inability to break-down the milk sugar, LACTOSE, into the simple sugars, glucose and galactose, due to a deficiency of  LACTASE, an enzyme, in the small intestine.  It can start in childhood and it worsens with age.  Symptoms begin 15 minutes to 2 - 3 hours after ingestion of milk or other products with lactose, such as ice cream, cheese, yogurt, or certain processed foods, and include:

            1.  BLOATING

            2.  ABDOMINAL CRAMPS

            3.  FLATULENCE

            4.  DIARRHEA (often explosive)

(Less severe attacks may not manifest all of the above symptoms)

Most adults have LI to some degree.  However, it is less common in most northern Europeans and generally the most common in Asians, African Americans, Africans, Hispanics, Native Americans, and Mediterranean people.

Lactose Intolerance is NOT a Milk Allergy, but rather the relative inability to DIGEST the lactose in milk and other lactose-containing products.  The undigested lactose passes through the small intestine and encounters bacteria in the colon which break it down with the release of copious amounts of hydrogen and methane gas.  These gases lead to the explosive diarrhea, bloating, flatulence, and cramps.  Additionally, some of the undigested lactose draws water into the colon, the so-called osmotic effect, further aggravating the symptoms.



                1.  Cut down or eliminate milk/lactose products, a marked improvement suggests the presence of LI.

                 2. Consult with a physician who may do lab tests such as lactose tolerance, exhaled hydrogen, or stool pH.     



What appears to be lactose intolerance, can sometimes be Milk Allergy.  The symptoms overlap since Milk Allergy can also present with GI symptoms resembling those described above for lactose intolerance.  Clues that the problem may be Milk Allergy include a family history of Milk Allergy, including in infants born into the family, and a personal history of food allergies in general.  Also pointing to Milk Allergy are the presence of symptoms often not found in Lactose Intolerance, such as hives, rashes, rhinorrhea (runny nose), sneezing, and unpleasant itching of the skin and oral mucous membranes.  

The culprit in Milk Allergy is usually the milk protein CASEIN.  Heating milk will often denature this protein enough to diminish its allergenic potential.  The same can be said of other foods which cause allergies, but the heating trick is not a guarantee of avoiding a serious allergic reaction.  There is also some evidence that ingesting small quantities of the offending food allergen and gradually increasing the exposure over time can lead to a desensitization to the food.  But again, this technique cannot be relied upon, and should be discussed with a physician.  However, if one does experience lessening of symptoms upon milk ingestion over time, this would argue AGAINST lactose intolerance which should get worse as one ages and not better.

A helpful tip:  If symptoms are relieved, or significantly mitigated by the use of lactose-free milk, or LACTAID tablets added to a milk product, the problem is probably Lactose Intolerance.  If this doesn't help, consider the problem may be Milk Allergy.  

In addition:  LACTOSE INTOLERANCE IS OFTEN MISDIAGNOSED AS  IRRITABLE BOWEL SYNDROME  (IBS) and ANXIETY.....although these conditions can occur together with LI.  

Finally, there is some evidence that an increase of BILE ACIDS in the intestines can also lead to symptoms of an irritable colon.  These acids, in excess, can trigger violent "peristaltic rushes" in the colon and cause the urgency and explosive diarrhea seen in both Lactose Intolerance and Milk Allergy.  Certain prescription medicines, containing a resin called cholestyramine, a bile acid sequestrant, can help, preventing the violent symptoms that might otherwise occur.  A beneficial side effect of cholestyramine is its ability to lower serum cholesterol.



A patient reported that she had suffered lactose intolerance her whole life, unable to ingest any milk products, including her favorite, ice cream.  Then, as if by a miracle, the lactose intolerance was gone, completely.  She happily enjoyed ice cream sundaes and all her other favorite dairy products, without any GI problems.  She asked for an explanation.

Upon further inquiry, the patient reported she had traveled to Mexico and while there had acquired a severe case of  "travelers' diarrhea."  She saw a doctor when she got back and was put on a course of Bactrim, an antibiotic, for about 7 days.  The lactose intolerance seemed to disappear after that.


It is likely the Bactrim, an effective treatment for travelers' diarrhea, since it tends to wipe out the offending E. Coli in the intestine, caused the lactose intolerance symptoms to disappear.  However, the lactose intolerance probably still remains, the SYMPTOMS are just TEMPORARILY gone.  This patient still lacks LACTASE, the enzyme that digests LACTOSE, and the undigested LACTOSE still passes undigested into her colon.  However, in the absence of many of her gut flora, good ones and bad, she no longer had the bacteria that break down the undigested LACTOSE, releasing hydrogen and methane gases into the colon and causing the explosive symptoms of lactose intolerance.  The SYMPTOMS were temporarily gone, not the disorder.  

I assured her that within a month, or two or three, the lactose intolerance symptoms would reappear, once the gut bacteria returned to their normal state.  This did in fact happen, and she thanked me for "uncuring" her.

She than asked if she could just remain on the antibiotic indefinitely to relieve lactose intolerance symptoms.  I advised against this, since colonic bacteria are an essential part of the body, the microbiome, as it is sometimes called.  The microbiome can be thought of as just as intrinsic and necessary as an organ.  Without these naturally occuring flora, in the intestine, the vagina, the mouth, the skin, and other areas, the body would be vulnerable to disease from opportunistic infection with pathological organisms.   Examples of this are the colonization of the vagina with yeast and the colon with C. Difficile, a very serious and difficult organism to treat.  Both of these infections are the result, in most cases, of treatment with antibiotics for other conditions. 


The temporary absence of lactose intolerance symptoms due to an antibiotic can also correspond to a false negative test result for lactose intolerance.  The tests affected are the hydrogen breath test and stool pH.  The lactose tolerance test should still be positive, since lactose is not digested and therefore there is a deficiency of glucose absorbed from the small intestine after ingestion of a lactose test dose.  



Lactose Intolerance is not as bad as it sounds.  Most people have a relative, but not a complete, deficiency of lactase and can handle moderate amounts of lactose.  The actual amount tolerated is learned by trial and error.  

Small amounts of milk can often be ingested safely if mixed with food.   Hard cheeses, such as cheddar and parmesan, as well as yogurt are often tolerated better than milk.

If necessary, non-dairy creamers can be used.  

LactAid brand milk (containing reduced lactose) can also be tried.

Several products exist which can be added to lactose-containing foods prior to ingestion.  These products break down the lactose.


PRECAUTIONS:  Always consult with a physician.  Lactose intolerance shares symptoms with many other gastrointestinal conditions.  Also, if milk/milk products are reduced/eliminated, supplement calcium with other nutritional sources or calcium tablets, as recommended by your physician.


ORIGIN of  LACTOSE INTOLERANCE:  Historically, humans required lactase to digest milk through weaning.  After that, lactase was unnecessary, except in cultures where milk/milk products were regularly consumed.  In northern Europe, animals were raised for dairy products over the last 10,000's of years.  Random mutation occurred allowing prolonged lactase production by the small intestine and thus allowing the digestion of milk.  Other cultures, not practicing animal husbandry, did not select out this mutation.  Hence they remained milk intolerant (lactase deficient) after childhood.



LACTOSE:  A sugar found in milk, each molecule consisting of two simple 6-carbon (hexose) sugars, in this case, GLUCOSE and GALACTOSE.

LACTASE:  A digestive enzyme found in the small intestine which converts LACTOSE to GLUCOSE and GALACTOSE, which can then be absorbed.

MILK ALLERGY:  An IMMUNE SYSTEM problem caused by the development of "hypersensitivity" to milk components, usually the protein, casein.

IRRITABLE BOWEL SYNDROME:  Also known as spastic colitis, a functional disturbance of the colon, causing urgency and alternating constipation/diarrhea.



National Digestive Disorders Information Clearing House

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Appointments:   818-991-8376