Why Most People Cannot Tolerate Drinking Milk

I received this article about milk intolerance from a friend, Professor Andrew Gomez who is a renowned ENT Surgeon. It was written by Dr. Joel Yong PhD.

(I quote what Dr. Young wrote below with no edition):

“One Root Cause Behind Lactose Intolerance"

Is the inability of the small intestine to produce sufficient lactase enzymes.

We tend to think of our digestive system at a very simple level. 

We eat food, our stomach acids break it down, our intestines absorb it, and whatever that isn’t absorbed is excreted into the toilet bowl. Unfortunately, life isn’t that simple. 

There are many more chemical reactions that are ongoing within the body to an extent that we may not even be aware of them.

Our digestive systems, for instance, contain a wide variety of enzymes that decompose complex foods into simpler substances. The saliva in our mouth contains amylase enzymes which decompose starch into simpler sugars such as glucose. Amylase, of course, is not just present in the saliva* but is produced by other organs in the digestive system such as the pancreas. Other enzymes work on decomposing fats (lipase enzymes) and proteins (protease enzymes).

There are even lactase enzymes in our small intestines that work specifically on decomposing lactose sugars. When our bodies aren’t producing enough of these digestive enzymes, we’d end up developing some *intolerances*.

For example, my mother had a gall bladder operation many years back, and the *consequence* of going through that operation was that *she cannot take in too much dietary fat in one sitting* because *she experiences fat malabsorption*. 

She does experience indigestion if the meal is too fatty, *though supplementation* with digestive enzymes *can be helpful to alleviate that discomfort*.

 *Lactose intolerance*

People who are lactose intolerant *tend to face the symptoms of* 

 *bloatedness* and *diarrhea* because their digestive systems *aren’t producing sufficient lactase enzymes* to decompose dietary lactose into its constituent glucose and galactose for absorption into the blood. Now, milk and other assorted dairy products *contain a good dose of this lactose sugar*

Hence lactose intolerance *is just about associated with the inability to operate normally after drinking milk*.

One of my friend’s friends had a stag night where they brought him to eat the spiciest chicken wings that one could find in Melbourne, Australia. They brought along a 1 litre bottle of milk to cool off the spice. He downs the entire bottle to cool off his tongue and says. 

_*“oh, by the way… I’m lactose intolerant” * That s**t did not go down well, pun intended.

The issue is that the lactase enzyme provides the _*fastest*_ route for lactose decomposition.

When that route cannot be used, *the lactose becomes a free-for-all for any other Tom, Dick or Harry microbe in the gut to grab and make use of*.

Unfortunately, these different microbes will respond differently to lactose and create different metabolites out of lactose:

Depending on which metabolites are being produced predominantly, there can be quite a fair bit of *irritation in the gut, * which leads to the digestive system wanting to *expel* everything _*quickly*. 

As lactose is a carbohydrate consisting of carbon and water molecules in its chemical structure, *it’s quite easy for a cell to break it down partially and produce carbon dioxide gas* — of course, a build-up of carbon dioxide inside the intestines *would create quite a fair bit of discomfort* and provide the symptom of _*belatedness* And that’s lactose intolerance right there.

Unfortunately, *if the digestive system isn’t equipped with the means to produce sufficient digestive enzymes, * or if we have had to undergo certain surgical operations that will affect our digestive system functions, *we’d inevitably face problems when eating certain types of foods*

That’s a sombre reminder that *our bodies tend to continue decaying* and that we do need to provide support for them to function at their best. (unquote)

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Here’s my response to what Dr. Joel Yong, PhD wrote above. Below is what I think is the reason.  

I believe the reason why most Asians are unable to tolerate milk is because they wean themselves off milk too early in life, one year after birth.  

Milk containing milk sugar (lactose) is broken down by an enzyme called beta-galactosidase, or rather more specifically the enzyme called lactase-phlorizin hydrolase (LPH). Approximately two-thirds of the world population are from Asia, and milk is the only food for babies. Unfortunately, most Asians, especially the Chinese, take milk off their babies after about a year and start to give them other foods instead of continuing with milk alongside with other supplemental foods.

Nutritionists know that the levels of this enzyme lactose decline hugely after the weaning phase of about a year. We call this trait “lactase non-persistence (LNP)”.  But we also know that if we continue to give the baby milk even after a year, we are able to simulate the lactase LPH gene encoded on the chromosome 2q21 that exclusively expresses the lactase in the small intestine to continue to express (produce) the lactase. This gene, as far as we know, is located in the apical part of microvilli within the brush border membrane of enterocytes. The LPH enzyme reaches the highest levels of activity during the nursing period when the baby is not taken off milk. Unfortunately, it declines dramatically after a short period from birth if the baby is weaned off milk too early.  

The majority of Asians are unable to tolerate milk (lactose intolerance) during adulthood, and some suffer clinical complications if they consume it. It has been estimated that approximately two-thirds of humans worldwide are LNP because we believe the baby was taken off milk far too early in life especially among Chinese.  We observed the poorer Indian communities are more tolerable to milk even at adult stage because they continue to breast-feed or give lactose-rich milk to their babies for as long as 5 years after birth. I believe this could have stimulated the LPH genes to express the lactase enzymes even at adulthood, but not the Chinese. We have no data for the Malays.

Not just our LPH genes, but even our human gut microbiome may be considered an annex of the human genome; as thousands of metabolic progressions are being performed by the microbial population that directly influence our gut physiology, including their host’s ability to utilize lactose and other carbohydrates. I believe we need further studies on the utilization of lactose by the human microbiome to explain discrepancies found in LP/NLP phenotypes.

Nutrition research has laid the foundations for the study of the genetic bases of lactase phenotypes in humans and represents a new paradigm in the way of visualizing genetic and phenotype data at the population level.

As far as I know no other animal is milk and lactose intolerant. I personally think that we humans too, like the rest of all other animals are capable of maintaining high levels of LPH lifelong as lactase persistence LP, for us to be able to tolerate milk during adulthood.

Both lactase phenotypes in humans present a complex genetic basis and have been widely investigated during the last decades. The distribution of lactase phenotypes and their associated single nucleotide polymorphisms (SNPs) across human populations has also been extensively studied. This is a small part of my personal view as an ex-nutritionist.   

 lim ju boo