Guest Columns

Why lactose?

Joseph O’Donnell is executive director of the California Dairy Research Foundation. He contributes this column exclusively for Cheese Market News®.

Blond, sweet and amply proportioned — I’m talking about lactose of course. Lactose is a well-known ingredient. As the most abundant solid in milk, much of commercial lactose finds its way into everything from pharmaceuticals to animal feed. The main constraint on lactose as a food ingredient is competition from low-priced corn syrup. There are distinctions that lactose holds over the competition with low hydrophilicity, low sweetness level and lower digestibility (which can be a negative for those with lactose malabsorption) just being a few.

While I’m not suggesting that lactose could beat the price of corn syrup any time soon, it is an interesting exercise to explore expanding markets by figuring out the puzzle nature threw at us. Why is it that nearly the entire plant world of carbohydrates (and even the storage form of carbohydrates in animals) is based on glucose and/or fructose polymers, yet milk comes up with this unique disaccharide — lactose? When we answer that question, we can delve into a plethora of new marketing and product development opportunities.

Fortunately, there are a number of bright scientists trying to get a handle on that very question. One train of thought looks at life from the first meal. Infant mammals are born with a sterile gastrointestinal tract (GI). If it were to stay that way, one could expect a host of diarrhea and other water and nutrient balance problems that would threaten rather than promote life. This is not unlike people placed on heavy antibiotics.

Another line of thinking winding its way through the hallowed halls of nutrition is the concept of slow food. Milk is the original slow food. Casein hits the stomach acid and forms clumps, making it harder for the proteases to break it down. Milkfat is in globules with a protective protein coating, and the saturated fat content so widely criticized actually slows digestion. Of course, the lactose depends on the presence of limited lactase for digestion, but the bottom line is that milk is digested at a rate consistent with the need to deliver nutrients. This means the body doesn’t have to deal with a huge influx of nutrients all at once. There are no surges of insulin and no dealing with loads of nitrogen released by amino acids unable to be incorporated so quickly into growth protein — life is good.

Lactose as a slow food is a good argument for explaining how evolutionary pressure came up with this sugar. As I mentioned above, lactose requires lactase to be digested and absorbed. With only modest levels of lactase available, the lactose cruises throughout the length of the small intestine, gradually releasing simple sugars at rates the rest of the body can assimilate. Some of this lactose also may escape to the colon. Isn’t this a definition of fiber — a carbohydrate resisting complete degradation in the small intestine and presenting itself to the bacteria laden colon?

Here’s where we put on our probiotics hat. Lactobacillus probiotics tend to reside in the small intestine at modest levels. Bifidobacteria probiotics hang out in the colon. We might not know the full benefits of these probiotics but we are gaining considerable insight. So, lactose comes along feeding the lactobacillus in the small intestine and continues down to jump into the colon to feed the bifidobacteria. Evolution has constructed a carbohydrate that delivers metered energy to the body, energy to selected bacteria in the small intestine and energy (ala fiber) to selected bacteria in the colon.

With the original consumer being a baby with a sterile gastrointestinal tract, this means that the bugs that do set up housekeeping are those that can utilize lactose. This is fascinating stuff. Now, if all this is indeed fact, then we should see evidence in the mammalian genome, specifically in the human genome, which has been sequenced and is under intense scientific investigation. This is a developing picture, but the answer to “Why lactose?” will become clear. The concept of slow food via a directed bacterial colonization of a sterile gastrointestinal tract OR for maintenance of a mature GI tract will be more completely understood.

Currently adult nutrition is compromised by the consumption of highly refined and easily digestible and available foods that deliver a slug of nutrients to trigger an insulinogenic, anabolic response under crises conditions. Constant nutritional insults of this sort lead to breakdowns and chronic diseases. Foods can be reformulated to regain the slow food approach and, no doubt, lactose can be part of that solution. At the same time, a slow food approach should be able to reduce lactose malabsorption, which has as much to do with the rate of digestion as with the level of lactase in the body.

Of course, all the above is spoken like a true nutritionist. Lactation physiologists will talk about osmotic pressure, solubility and a bunch of other things built around the chemistry of milk. Someone else can write that column. I’ll stick with nutrition since the function of milk is to deliver nutrition and health.

Lactose production today is pretty much in balance with demand. Product development never ends. We know that as production of cheese and ultrafiltered milk grows there will be growing supplies of permeate. Answering nature’s lactose riddle requires one step at a time. Nature rarely displays superficiality. Pursing the relationship between lactose products and support of probiotics certainly appears to make sense as an initial foray into the solution. Other aspects such as interactions between lactose and the largest immune organ of the body — GI tract — lay ahead.

While lactose might not have a direct effect on immune activity, immune activity could be the indirect consequence of lactose’s biological (prebiotic) activity. We could brainstorm all day long on this and other scenarios of lactose bioactivity. At the end of the day, however, we know that the best and brightest of our dairy scientists are actively pursuing this area. Bit by bit we will solve the lactose puzzle to the benefit of the industry and consumers.


The views expressed by CMN’s guest columnists are their own opinions and do not necessarily reflect those of Cheese Market News®.

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