Got Milk? Part 2

As we learned in the previous post, the lifelong ability to digest lactose is actually a genetic "defect". Could there be adverse consequences to consuming milk despite the benefits? If lactose reaches the colon whole, doesn't that make it a prebiotic fiber?

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From:  Lactose malabsorption and intolerance: pathogenesis, diagnosis and treatment (2013)

Lactase activity changes during development. In most humans, lactase activity reaches a maximum in late pregnancy but declines after 2–3 years of age and reaches a stable low level at age 5–10, a process which might help weaning. However, a proportion of the human population, especially Caucasians from Northern Europe or northern European descent, retain high lactase levels during adulthood (lactase persistence). Both, lactase persistence and non-persistence (leading to lactose malabsorption) are thus normal human phenotypes.

Just because you can drink milk...should you? Our early ancestors seemed to know to avoid the lactose, as shown here:

From: Direct evidence of milk consumption from ancient human dental calculus (2014) 

Adoption of animal milk consumption by humans typically requires behavioral adaptations, such as culturing and curdling techniques, to remove or reduce the lactose content of milk in order to make dairy products digestible after infancy. Additionally, populations with long pastoralist traditions in Europe and India, East Africa, and the Arabian peninsula have also independently evolved lactase persistence (LP), a genetic adaptation in the regulation of the lactase gene (LCT) that allows continued adult digestion of milk. LP is hailed as one of the clearest examples of gene-culture co-evolution in humans, yet many fundamental aspects of its evolution remain unknown and the socioeconomic context and scale of prehistoric and historic dairying are only poorly understood.

Lactose contents of dairy products

Our ancestors avoided lactose, why shouldn't we? For the most part, this means simply avoiding free-flowing, fluid milk (unless noted as "Lactose Free"). Lactose is the "carb" portion of milk, so processes that separate the fats from the carbs result in lower lactose concentrations.

Many "lactose content" charts exist, but they can be confusing and often in disagreement. Here are some lengthy lists of lactose contents in various dairy products:

• ACJN Lactose Contents
• Steve Carper's Big List

In general:

• All fluid, drinkable milk is high in lactose--unless lactose free.
• Cultured milk products like sour cream, yogurt, kefir all have a bacterial component that lowers the lactose content.
• Cheeses have lower lactose, with harder cheeses being lowest. American Pasteurized/processed cheese (like Velveeta) are high in lactose!
• Butter and Ghee are low in lactose.

The Dietary Guidelines for Americans dictate that every person should get "three servings" of dairy per day. A "serving" is a cup of milk/yogurt or two ounces of cheese.  Each serving of fluid milk contains approximately 12g of lactose. 

The reasoning behind this recommendation?

Dairy foods, particularly fluid milk, yogurt, and cheese, are the principal sources of calcium in the diets of the industrialized nations, and without a high dairy diet, it is difficult to come close to recommended calcium intakes.

The recommended daily allowance for calcium is 1000mg (1g). True to form, one cup of milk contains 300mg of calcium. But there are other ways to get 1000mg of calcium without dairy.  Fish, vegetables, and nuts, for instance (see calcium content list).  Admittedly, it's easier with dairy, and several servings of dairy a day is probably great advice. Our thought is that it may be wise, though, to limit overall lactose intake. In this case, enjoy your dairy, but get it from traditional sources: yogurt, cheese, buttermilk, and kefir over pasteurized, fluid milk.

Raw milk may be better than pasteurized in many ways, and if available where you live, immensely better than pasteurized milk. Goat or sheep's milk are also good choices, but again, raw or fermented to emulate traditional methods of consuming. 

We'll delve more into these recommendations in parts 3 and 4, but our feeling is that the lactose content, without accompanying bacteria found in raw and fermented dairy, is a problem.  If you look at a lactose content chart, like the two linked above, you'll see that fermented milk products have just as much lactose as regular milk, however, fermented dairy has a secret weapon!  The bacteria associated with fermented dairy have their own "lactase" (the enzyme that degrades lactose). This is a big part of our argument that "lactose is bad for you."

From: Lactose Contents of Milk and Milk Products

Fermented products that are not pasteurized or heated in ways that destroy enzyme activity have significant levels of B-galactosidase that contribute to the digestion of lactose in the intestine of persons consuming them.  Lactase activity can be detected in cultured yogurt but not in cottage cheese, soured cream, acidified yogurt, or milk. It can be concluded that lactase bound to bacterial cells in cultured yogurt may be released during gastric digestion, making these products more acceptable for lactose maldigesters.

 

Is lactose a prebiotic "fiber?

For most people in the world, the ~70% LNP population, drinking milk means undigested lactose enters the colon where it is rapidly degraded by gut bacteria. This may sound like the definition of a "prebiotic," but lactose appears to have quite different effects on people. 

More than a few researchers have reached the conclusion that being unable to digest lactose should be a protective measure, as it shifts milk being consumed to food for the gut flora, as shown here: Lactose--a potential prebiotic. 

In inflammatory bowel disease, lactose (together with other prebiotics) may promote the maintenance of lactic acid-producing bacteria and prevent the expansion of potential pathogens. In colorectal cancer, lactase insufficiency may serve a role similar to the postulated potential benefits of resistant starch...

Just as with FODMAPS, RS, and other fibers, some people just don't have the intestinal machinery needed to turn lactose into a "good thing." While some may develop a set of bacteria that can ferment lactose, others never seem to be able to drink milk without the symptoms that plague the lactose intolerant: gas, pain, bloating and diarrhea. 

So, whether it's genetic or bacterial in nature, one thing is apparent: humans react to lactose in radically different ways and the recommended 3 glasses of milk a day for everyone is foolhardy at best. Especially in the modern, pasteurized or low fat version, so different from the raw milk that the first dairy farmers would probably drink.

In this study, Colonic Fermentation May Play a Role in Lactose Intolerance in Humans, researchers looked at LNP type people who could and could not tolerate lactose. They examined all aspects of their large intestines to determine why some could or could not handle the lactose that entered their colons.

What they found is very interesting!  When lactose enters the colon, it is first broken down to glucose and galactose by a substance called "β-Galactosidase." This is the same family of enzymes that the missing lactase (of the LNP clan) belongs to. It turns out that not only humans can break down lactose, but bacteria as well!

During colonic fermentation, lactose is first hydrolyzed to glucose and galactose, which are subsequently fermented, leading to the production of a series of intermediate (e.g., lactate, formate and succinate) and end-product metabolites [i.e., acetate, propionate, and butyrate, gases (H₂, CO₂ and CH₄), and biomass].

This paper goes on to discuss the difference in lactose intolerant or lactose tolerant LNP:

A low lactose-fermenting capacity of the colonic microbiota, which leads to inefficient removal of the maldigested lactose (and/or its intermediate fermentation metabolites), or a low absorption capacity of the colon, which leads to inefficient removal of the fermentation metabolites, may contribute to the occurrence of symptoms.

Four issues with calling lactose a "prebiotic":

1. Some people (LNP) do not produce lactase enzymes in the small intestine, and their gut bacteria cannot utilize lactose.
2. Some people (LNP) do not produce lactase enzymes in the small intestine, but their gut bacteria can utilize lactose.
3. Some people (LP) should produce lactase enzymes (according to their genes) but still are lactose intolerant.
4. Gut bacteria must be able to break down lactose with enzymes AND ferment the byproducts AND the colon must be healthy to absorb the byproducts.

These are probably also the exact same reasons why we see some people having issues with FODMAPS, RS, and other fibers, and why there may truly be no "perfect prebiotic" for everyone.

Conclusion/Questions

Early "Paleo" diets dissuaded people from eating or drinking dairy...was this good advice? Should there have been a differentiation between consuming liquid milk and fermented dairy products such as yoghurt or cheese?   Whether it's raw, pasteurized, or chocolate milk has no bearing. It's all about the lactose content. The "lactose free" type milks may be OK. Cheese, butter, kefir, and yogurt all seem to fall outside the realm of LP/LNP issues.

Independently of whether one is LP, LNP, lactose intolerant, or has no problem drinking milk, lactose seems to be causing problems for lots of people worldwide.  Again we ask: Just because you can drink milk...should you?

We'll explore more in parts 3 and 4. What we've talked about today is not "new" knowledge, it's been known for quite a long time, actually. However some key pieces to the puzzle may be yet to fall into place.

...and we won't even mention the whole A1/A2 issue!

Tim, Gabriella, and Gemma