Abstract
Background: Milk intake has been associated with lower blood pressure (BP) in observational studies, and randomized controlled trials suggested that milk-derived tripeptides have BP-lowering effects. Milk intake has also been associated with body mass index (BMI). Nevertheless, it is unclear whether increasing milk consumption would reduce BP in the general population. Methods: We investigated the association of milk intake with obesity and BP using genetically-defined lactase persistence (LP) based on the rs4988235 polymorphism in a Mendelian randomization design in the 1982 Pelotas (Southern Brazil) Birth Cohort. These results were combined with published reports identified through a systematic review using meta-analysis. Results: In the 1982 Pelotas Birth Cohort, milk intake was 42 [95% confidence interval (CI): 18; 67) ml/day higher in LP individuals. In conventional observational analysis, each 1-dl/day increase in milk intake was associated with −0.26 (95% CI: −0.33; −0.19) kg/m2 in BMI and −0.31 (95% CI: −0.46; −0.16) and -0.35 (95% CI: −0.46; −0.23) mmHg in systolic and diastolic BP, respectively. These results were not corroborated when analysing LP status, but confidence intervals were large. In random effects meta-analysis, LP individuals presented higher BMI [0.17 (95% CI: 0.07; 0.27) kg/m2] and higher odds of overweight-obesity [1.09 (95% CI: 1.02; 1.17)]. There were no reliable associations for BP. Conclusions: Our study supports that LP is positively associated with obesity, suggesting that the negative association of milk intake with obesity is likely due to limitations of conventional observational studies. Our findings also do not support that increased milk intake leads to lower BP.
Highlights
Single nucleotide polymorphisms (SNPs) in the enhancer region of the LCT gene [OMIM: 603202] are functionally associated with adult-type hypolactasia;[1] rs4988235 is one such SNP, whose association with lactase persistence (LP)—maintenance of lactase expression after weaning [MIM: 223100]—was first identified in Finland.[2]
There was an inverse association of milk intake with obesity and blood pressure
LP was positively associated with body mass index (BMI) and overweight-obesity in our meta-analysis
Summary
Single nucleotide polymorphisms (SNPs) in the enhancer region of the LCT gene [OMIM: 603202] are functionally associated with adult-type hypolactasia;[1] rs4988235 (a C to T SNP located 13910 base pairs downstream of the LCT gene) is one such SNP, whose association with lactase persistence (LP)—maintenance of lactase expression after weaning [MIM: 223100]—was first identified in Finland.[2]. We evaluated whether geneticallydefined LP is associated with milk intake, obesity and blood pressure among subjects who have been followed up since birth in a southern Brazilian city. We combined these results with published data identified through a systematic review of the literature
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