The Swedish mortality study showed that milk was linked to increased mortality rates, heart disease and hip fractures. What does this mean?

Firstly, it is important to point out that the same author published two subsequent papers (in 2015 and 2017 ), one which showed no association between milk and mortality and the other that showed mortality risk was diminished by fruit and vegetable intake. The original study also found that a high intake of cheese or fermented milk products was associated with lower mortality and lower fracture rates.

This study is an outlier among the wider research in this area, with the majority of studies indicating positive roles for dairy across several areas of health [ Thorning et al. 2016 ]. In addition, a recent meta-analysis study , which combined data from 29 other studies showed no association between dairy and mortality.

The authors of this study themselves warned that their results should be “interpreted cautiously” due to their study design. The design was an observational study, which means it can identify a correlation, not causality – therefore it is a scientifically incorrect to conclude that milk increases mortality on the basis this observation. There is also a risk that inherent confounding factors were not measured or accounted for in the observation. For example, a study could observe that people with long hair wear more lipstick but that does not mean that long hair causes people to wear lipstick. Gender would be a confounding factor in this case.

Lastly, for anyone that is confused about the validity of the Swedish study, it is worth visiting the website of the British Medical Journal, who published the paper. Here the journal also published 49 letters that they received in response to the publication. The letters are mainly from independent scientists who identify flaws with the study and its interpretation.