‘Undervalued’ lactose doesn’t deserve bad dairy rap, study

Introducing a special February issue of the journal examining the nutrition and health aspects of lactose and its derivatives, International Dairy Federation (IDF) action team chair Michael Gänzle and his fellow authors wrote:

“Lactose is far more than a source of dietary energy. This milk sugar also helps to boost calcium absorption in the mammalian body, and derivatives such as lactulose have been shown to exert a number of physiological effects, including the promotion of bifidobacteria in the intestine.”​

The calcium absorption claim, for instance, is supported by paper exploring this issue published in the same issue of the IDJ, by H.S Kwak, W-J Lee and M.R Lee, ‘Revisiting lactose as an enhancer of calcium absorption’​.

The scientists noted that although the stimulating effect of lactose on calcium absorption was clear in animal studies, in humans the exact absorption/retention mechanism was still not clearly identified, and thus the same effect was “still controversial”. ​

Kwak, Lee and Lee wrote: “Part of this uncertainty can probably be attributed to the design of several studies in which control sugars (e.g. glucose, galactose [its component monosaccharides]) used for comparison with lactose also enhance calcium absorption.”​

Calcium absorption claim support​

Despite calling for future research lactose absorption/retention, the team concluded: “Lactose does have a significant (P<0.05) effect on the absorption of calcium when compared with either non-absorbable sugars such as mannitol, or to a high molecular weight carbohydrate source, such as cornstarch.”​

More generally, Gänzle et al. speculated that perhaps one reason why lactose was undervalued stemmed from concerns about dietary intolerance.

They wrote: “Although many people lose their ability to digest lactose after childhood, scientific studies show that most people can consume milk with a meal and not suffer any adverse effects."​

Moreover, traditional dairy products such as ripened cheeses were virtually lactose-free, the authors said, while technological advances in dairy processing had led to the introduction of many lactose-free products.

Caries-causing potential rebuffed​

Questions raised about the dental caries or tooth decay-causing potential of lactose were also misplaced, Gänzle et al. suggested, since lactose had been “widely accepted as the least cariogenic of dietary sugars over the years”.​

Concerns were partly due to the effect of organic acid metabolites – produced during lactose fermentation – on tooth enamel – they added.

“However, as with so many nutrition-related matter, it is easy to lose sight of the fact that people consume whole foods and not pure substances. Humans would not ordinarily consume pure lactose,"​ the authors wrote.

“They normally consume lactose within dairy and other foods, and these foods also contain a wide range of other nutrients including proteins, fats, vitamins and minerals, which buffer the effect of lactose and thus offer protection from cariogenicity.”​

The team added that a review of lactose cariogenicity with special reference to childhood dental caries formed part of the IDJ's February issue.

Title: ​‘Nutrition and health aspects of lactose and its derivatives: state of the science’

Authors: ​M.Gänzle, J.Bryans, P.Jelen, G.Smithers

Source: ​International Dairy Journal, ​Vol. 22, Issue 2 (February 2012), Published online ahead of print: doi:10.1016/j.idairyj.2011.11.001​