Dietary habits have been shown to modulate the micro-organisms populating the human digestive tract 6,18,19, but low adherence to diet change recommendations has failed to render diet-based public health interventions successful on a large scale.
One might imagine that a high cheese intake might lead to weight gain. In our study, the R2 value indicates that 29.8% of the prevalence of obesity is explained by the annual consumption of cheese. However, the correlation is an inverse correlation, meaning that the more cheese is consumed in a country, the lower the prevalence of BMI is. Further, to reduce the prevalence of BMI by 5% in a given country, analysis of the regression slope concluded that the annual consumption of cheese per capita would need to increase by approximately 33kg, which represents the exact weight of a 12-month matured Gruyère cheese wheel.
The beneficial effect of cheese on weight loss is supported by recent evidence. For instance, a systematic review and meta-analysis of 24 cross-sectional studies found that dairy products intake and milk consumption were associated with decreased risk of obesity 20. Further, consumption of dairy products was demonstrated to modulate the gut microbiome 21,22 and reduce markers of systematic inflammation 23-26. Looking more specifically at cheese consumption, Alegria-Lertxundi et al. described that cheese consumption was inversely correlated to obesity in the Basque population in Spain 27.
The effect of dairy products seems to differ depending on the type of dairy and fermentation. Hansson et al. randomized 47 participants to receive four daily dairy meals corresponding to 45g of fat in the form of butter, cheese, whipped cream or sour cream. The authors found that cheese intake increased gastrointestinal hormones secretion and decreased appetite when compared to whipped cream 28 and induced different postprandial effects on serum triglycerides, HDL cholesterol and insulin 29. Further, a cross-sectional study on 114,692 Dutch citizens showed a positive association between milk, non-fermented dairy products and obesity, and an inverse association for fermented dairy such as custard and yoghourt. Results were heterogeneous for cheese, and Dutch cheese was not reported to have an effect on obesity 30. The effect on weight might also be modulated by the bacteria contained in dairy products. For instance, different strains of Lactobacillus were shown to have opposite effects on weight gain 31,32. Of note, taxonomic differences of the microbiome of dairy product consumers are modulated by the origin of the milk, but also by the effect of fermentation 33. Different dairy products were shown to have different effects on inflammatory markers, and consumption of fermented dairy products such as cheese, has been shown to induce a less of an inflammatory response than non-fermented dairy products 34,35.
The study has several limitations. First, the cheese consumption at the nation-level might not represent the cheese intake at the individual level. Also, our results do not allow to conclude if a high cheese intake during a short time period is equivalent to a low cheese intake spread over a long time period. Consumption of a Gruyère cheese wheel on a week before Summer holidays might not be recommended. Second, the existence of potential confounding factors is not excluded. People with the highest cheese intake might also be people who ski the most, as cheese is usually consumed when practicing Winter sports.
We note that Swiss citizens are the biggest consumers of cheese, which they consume raw or melted in fondue, but also have the lowest age-adjusted prevalence of BMI. Moreover, chocolate consumption was previously demonstrated to be correlated to the number of Nobel laureates per 10 million inhabitants 36. We therefore believe that public health intervention should aim at adopting a Swiss-inspired diet, which traditionally includes locally produced chocolate and cheese. Further, in this time of COVID-19 pandemic, we wonder whether the required limitation of travel to the Swiss Alps might lead to an increase of the average BMI in addition of a shortage of Nobel laureates in Europe.