Saturday, 15 November 2014

Milk has gotta lotta bottle?

"High milk intake was associated with higher mortality in one cohort of women and in another cohort of men, and with higher fracture incidence in women". Those were some of the conclusions reached in the study by Karl Michaëlsson and colleagues [1] (open-access) looking at milk consumption and "mortality and fractures in women and men". The BBC among other media have covered the study (see here).
Take me out tonight

Based on quite a large participant group (two actually) who completed a food frequency questionnaire among other things, researchers followed over 100,000 people some 10-20 years later to ascertain details on "fracture events" and mortality. For a smaller subgroup, they also reported on: "the urine oxidative stress marker 8-iso-PGF2α, a dominant F2-isoprostane and an ideal standard biomarker of oxidative stress in vivo" on the basis of analysing any connection between: "D-galactose in milk with theoretical influences on processes such as oxidative stress and inflammation". Oh, and a familiar cytokine also gets a mention: interleukin-6.

Authors, with caveats, reported something of a possible connection between milk intake and outcomes: "a dose dependent higher rate of both mortality and fracture in women and a higher rate of mortality in men with milk intake, a pattern not discerned with other dairy products" and "positive associations between milk intake and concentrations of markers for oxidative stress and inflammation". IL-6 levels were also correlated with milk intake (although surprisingly little is made of this association in my opinion bearing in mind some of the other literature in this area [2]). For quite a thorough review of the study and findings, I will refer you to the NHS Choices take on it (see here).

Milk has been something of some interest to this blog down the year based on my preoccupation with diet and [some] autism [3] (see here and see here for examples) and further a possible relationship with other behaviourally-defined conditions (see here). I have tried not to come down too heavy on the white stuff (see here) given that it's not all doom and gloom when it comes to the benefits of milk for quite a few people albeit with the sunshine vitamin/hormone also needing to be considered. As an aside, the recent coverage of the the Caerphilly Cohort Study and their 'roadmap to healthy ageing' (see here) previously also talked about milk products and "a markedly reduced prevalence of the metabolic syndrome" [4], so one has to be slightly cautious about demonising milk generally.

The Michaëlsson results however cannot be readily ignored given the impressive participant size and prospective design of study used. The fact that authors reported findings pertinent to milk consumption but that "intake of fermented milk products such as yogurt and soured milk and cheese were associated with lower rates of fracture and mortality" is also potentially important. I could start going on about how processing might affect lactose / galactose content in some cheeses [5] and yoghurts [6] but this is perhaps fodder for another day. Likewise the findings reported by Ji and colleagues [7] suggesting "people with lactose intolerance, characterised by low consumption of milk and other dairy products, had decreased risks of lung, breast, and ovarian cancers" might also be relevant. I note also that chatter about casein (the protein in milk) content as a function of researchers findings are largely absent from the discussions but are perhaps also potentially relevant in light of the whole A1-A2 milk issue rising in prominence these days (also including mention of oxidative stress too).

Music to close: Lorde - Yellow Flicker Beat.

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[1] Michaëlsson K. et al. Milk intake and risk of mortality and fractures in women and men: cohort studies. BMJ. 2014; 349.

[2] Labonté MÈ. et al. Dairy Product Consumption Has No Impact on Biomarkers of Inflammation among Men and Women with Low-Grade Systemic Inflammation. J Nutr. 2014 Nov;144(11):1760-7.

[3] Whiteley P. Nutritional management of (some) autism: a case for gluten- and casein-free diets? Proc Nutr Soc. 2014 Oct 14:1-6.

[4] Elwood PC. et al. Milk and dairy consumption, diabetes and the metabolic syndrome: the Caerphilly prospective study. J Epidemiol Community Health. Aug 2007; 61(8): 695–698.

[5] Portnoi PA. & MacDonald A. Determination of the lactose and galactose content of cheese for use in the galactosaemia diet. J Hum Nutr Diet. 2009 Oct;22(5):400-8.

[6] Alm L. Effect of fermentation on lactose, glucose, and galactose content in milk and suitability of fermented milk products for lactose intolerant individuals. J Dairy Sci. 1982 Mar;65(3):346-52.

[7] Ji J. et al. Lactose intolerance and risk of lung, breast and ovarian cancers: aetiological clues from a population-based study in Sweden. Br J Cancer. 2014. October 14.

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ResearchBlogging.org Michaelsson, K., Wolk, A., Langenskiold, S., Basu, S., Warensjo Lemming, E., Melhus, H., & Byberg, L. (2014). Milk intake and risk of mortality and fractures in women and men: cohort studies BMJ, 349 (oct27 1) DOI: 10.1136/bmj.g6015