Studies say 80 percent or more of Southeast Asians are Lactose Intolerant

June 11, 2012

Have you ever noticed feeling gassy, bloated or even had a diarrhea after drinking milky chiya or eating a bowl of cereal with milk? Consider this, you maybe lactose intolerant i.e. your body doesn’t produce enough lactase, an enzyme that breaks down lactose, sugar found in milk.

Without lactase, lactose passes through the stomach undigested and reaches the large intestine, where bacteria try to metabolize it, causing fermentation and gas by-products that leave people feeling gassy. It also prevents colon from reabsorbing water, causing laxative effect, thus the diarrhea, flatulent and stomach craps.

There seem to be not much of a consensus on the exact figure, some quote 95 percent, some 90 percent and a few even 100 percent, but all the reports agree that lactose intolerance is most prevalent among Southeast Asians and Native Americans. At least 80 percent if not more of Southeast Asians are said to be lactose intolerant. “Yes, it is common among Nepalese people. However, no studies have been done on the subject, and thus you cannot say for certain how many percent of Nepalese are lactose intolerant. But Nepal do fall in that category. Also many doctors confuses lactose intolerance with IBS (Irritable Bowel Syndrome), as they resemble a lot in terms of symptoms,” says Dr Umid Shrestha, Associate Professor, Gastroenterology & Hematology, Manipal College of Medical Sciences & Manipal Teaching Hospital, Pokhara.

What could be the reason for high prevalence among Southeast Asians?

For us to understand why some of us are lactose intolerant and others are not, we have to first understand that humans were designed to digest milk as babies but not as adults, and that it took genetic mutation to enable adult humans to digest milk. Thus you will find that lactase presence is highest in babies, when milk is the sole source of nutrient, and it gradually declines over time there after when weaning is stopped.

Scientists believe that humans evolved into being lactose tolerant or ‘lactose persistent’ around ten to twelve thousand years ago when people started domesticating animals and drinking their milk.

The new insights on the 5,300 old iceman nicknamed Ötzi found in Italian Alps in 1991 published in the journal Nature Communication this February also reconfirms the idea that the early humans were all lactose intolerant. When scientists sequenced his complete genome, they found him to be lactose intolerant.

In early 2002, a team of scientists from University of California, Los Angeles identified the two variations in the human gene associated with lactose intolerance. They studied people from different backgrounds who had been diagnosed with lactose intolerance — Finnish, Germans, South Koreans, French, Americans, and found them to have either one of the two variations. The findings published in Nature Genetics conclude that if the same variations occur in distantly related populations, it must be a very old gene, the original form of the gene, which mutated to tolerate milk when early humans started dairy farming.

Thus, lactose persistence is most common among people with a long tradition of dairy farming, such as northern Europeans, some groups in India and the Tutsis in central Africa. Only five percent of Northern Europeans (who started dairy farming early on) and close to 100 percent of Southeast Asians (who started dairy farming later) are found to be lactose intolerant. Essentially, whether you are lactose intolerant or not, has lot to do with whether your ancestors hail from regions where dairy farming was practiced or not.

But, Nepalis have cattle culture, we even worship them?

Dahi ko achar, mahi, milky chiya, our diet do include milk products, very much unlike our neighbor to the north, China, prompting us to quickly to dismiss even a remotest idea that we may indeed be lactose intolerant. However, a study published last year in Molecular Biology and Evolution out of University of Cambridge says that the way we incorporate milk in our diet may be the reason.

The study took DNA sample of 2,300 individuals from 105 different tribes and castes all across India and also a group from Nepal. The study found four out of five individuals tested to have the gene associated with lactose intolerance — meaning only 18 percent of population tested were able to digest milk, and 82 percent were lactose intolerant.

The study indicates that there may be two reasons why we don’t notice the symptoms of lactose intolerance. One, non-Europeans experience less severe symptoms of lactose intolerance; two, we usually don’t drink our milk straight, we usually ferment it as dahi or put it in chiya breaking down the lactose within.

Other reasons for lactose intolerance?

“Most of the Nepalese acquire lactose intolerance, as a result of the primary diseases like gastroenteritis, etc,” says Dr Satish Gurung, Gastroenterologist and Senior Medical Practitioner at Gurkha welfare Scheme, Pokhara. “Our intestines contain villi for absorption and digestion, when it is damaged, lactase production also decreases. So when people get gastroenteritis or severe diarrhea or intestine infection; they also develop secondary lactose intolerance along with primary disease. Once the main cause of the disease is treated; lactase level can be restored,” he explains.

Though rare, one can be born with complete absence of lactase activity as well, called congenital lactose intolerance. Passed from generation to generation, one of the parents pass on the defective form of gene to the baby. Babies with this type of lactose intolerance have diarrhea from birth and require lactose-free infant formulas.

How can you find out if you are lactose intolerant?

The two common methods doctors use to find out whether you are lactose tolerant are — Hydrogen breath test and Lactose tolerance blood test. In both tests you are asked to drink liquid containing high level of lactose. In Hydrogen test, Hydrogen level is tested, and in blood test, blood glucose level is tested, at regular intervals. If high level of Hydrogen is detected in your breath, it means you were unable to digest lactose, which went on to your colon and fermented releasing Hydrogen. Similarly, in the blood test, if there is no rise in blood glucose level, it means you were unable to digest lactose, which would otherwise have broken down to glucose increasing your blood glucose level.

For infant and children who cannot undergo these two tests, Stool acidity test is administered. Fermentation of undigested lactose results in lactic and other acids, which can be detected in stool sample.

“None of these tests are currently done in Nepal,” says Dr Gurung. “Doctors rely solely on patients’ medical history which increases the chances of misdiagnosis between IBS and lactose intolerance. The reason being both has similar symptoms—abdominal distension (fullness), nausea, abdominal pain and intermittent of both constipation followed by diarrhea. But having said that, it is also possible that sometimes patients may have both IBS and lactose intolerance,” he adds.

What treatments are available?

“If you have lactose intolerance, it’s not like fever or infection that after a course of medications or antibiotics, you become better,” explains Dr Gurung. “However, if you understand your level of ability to digest lactose, you can control the symptoms of lactose intolerance with quantity dairy in your diet. Lactose intolerance doesn’t mean that you cannot drink milk products at all.”

In fact lactose intolerant individuals can drink milk and eat milk products in certain quantity depending upon their lactase activity level; it is only if you are allergic to lactose that you should not drink milk.

Perhaps all those many cups of milky chiyas should indeed be reconsidered.

A self-diagnosis is not advised, but be sure to start a conversation with your doctor about it on your next visit.

Have you ever felt uneasy in your stomach after consuming milk or milk products?

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One Response to Studies say 80 percent or more of Southeast Asians are Lactose Intolerant

  1. Praman Adhikari on January 7, 2015 at 12:57 AM

    Is Hydrogen Breath Test available in Nepal? If yes, please do share.
    Thank you

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