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While investigating the rise of adult lactose tolerance, I came across the news that China has been encouraging its citizens to drink more milk, even though most of the Asian population lacks the SNP (single-nucleotide polymorphism) which conveys lactase persistence.

Is it still possible for an adult without lactase persistence to build-up a tolerance for lactose over time? If so, what's the mechanism?

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    $\begingroup$ Have you seen this? Looking around, it seems that you can get some of your intestinal microflora to break down the lactose for you... $\endgroup$
    – user132
    Dec 15, 2011 at 16:23
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    $\begingroup$ @shigeta SNP is a single nucleotide polymorphism (i.e., an allele that differs from another by just one base pair). Many important genetic polymorphisms are SNPs, but not all. I don't know if persistent lactose tolerance is caused by a SNP, or even by a single gene. $\endgroup$
    – octern
    Jul 5, 2012 at 1:34

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It seems that yes, it is possible to increase the tolerance for lactose over time, and it has to do with the adaptation of microbiota.

A simplistic explanation comes in the following article: Hertzler SR, Savaiano DA. 1996. Colonic adaptation to daily lactose feeding in lactose maldigesters reduces lactose intolerance. The American journal of clinical nutrition 64: 232–6.

In which the authors claim the following:

  • "Colonic adaptation appears to reduce the symptomatic response to lactose via several mechanisms. (...)
  • (...) increased β-galactosidase activity after regular lactose ingestion indicates that colonic bacteria are able to ferment lactose more rapidly. (...)
  • (...) This metabolic shift is thought to result from the proliferation of lactose-fermenting, non-hydrogen producing organisms such as Bifidobacteria."

This article makes reference to another one which supposedly explains the microbiota adaptation: Hill Mi. Bacterial adaptation to lactase deficiency. In: Delmont J, ed. 1983. Milk intolerances and rejection. New York: Karger: 22–6.

But unfortunately I could not find the full text. I hope you are luckier than me.

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    $\begingroup$ The second 'article' is actually a chapter in a book, which is why you couldn't find the full text :) $\endgroup$
    – Rik Smith-Unna
    Jul 2, 2012 at 16:12
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Here are my thoughts on the topic.

Dairy good is not only milk, but also the following milk products: sour milk products (like yougurt, kefir, katik, buttermilk, etc.), cheese, etc. These products can contain less lactose than in the milk solids (due to fermentation during processing). It is also common for some of these products to contain living lactase-active bacteria, that can digest lactose.

Regular intake of these products can lead to certain changes in our small intestine microflora, so that the lacking lactase activity is substituted by the bacteria and thereby the tolerance grows. Maybe this is the intend of the Chinese government? Maybe they encourage the intake of sour milk products and not solid milk?

It is known, for example, that children with congenital/primary enzymatic deficiency develop the tolerance at the age of 6-10 years so that no special diet is needed anymore. This is true at least for such common enzymatic deficiencies like phenylketonuria and coeliacia.

In Russia, where I got my medical degree, it is common to use bacteria in the treatment of many types of primary intolerance combining this treatment with dietary support.

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