Milk intake and incident stroke and CHD in populations of European descent: a Mendelian randomisation study

Higher milk intake has been associated with a lower stroke risk, but not with risk of CHD. Residual confounding or reverse causation cannot be excluded. Therefore, we estimated the causal association of milk consumption with stroke and CHD risk through instrumental variable (IV) and gene-outcome analyses. IV analysis included 29 328 participants (4611 stroke; 9828 CHD) of the European Prospective Investigation into Cancer and Nutrition (EPIC)-CVD (eight European countries) and European Prospective Investigation into Cancer and Nutrition-Netherlands (EPIC-NL) case-cohort studies. rs4988235, a lactase persistence (LP) SNP which enables digestion of lactose in adulthood was used as genetic instrument. Intake of milk was first regressed on rs4988235 in a linear regression model. Next, associations of genetically predicted milk consumption with stroke and CHD were estimated using Prentice-weighted Cox regression. Gene-outcome analysis included 777 024 participants (50 804 cases) from MEGASTROKE (including EPIC-CVD), UK Biobank and EPIC-NL for stroke, and 483 966 participants (61 612 cases) from CARDIoGRAM, UK Biobank, EPIC-CVD and EPIC-NL for CHD. In IV analyses, each additional LP allele was associated with a higher intake of milk in EPIC-CVD (β = 13·7 g/d; 95 % CI 8·4, 19·1) and EPIC-NL (36·8 g/d; 95 % CI 20·0, 53·5). Genetically predicted milk intake was not associated with stroke (HR per 25 g/d 1·05; 95 % CI 0·94, 1·16) or CHD (1·02; 95 % CI 0·96, 1·08). In gene-outcome analyses, there was no association of rs4988235 with risk of stroke (OR 1·02; 95 % CI 0·99, 1·05) or CHD (OR 0·99; 95 % CI 0·95, 1·03). Current Mendelian randomisation analysis does not provide evidence for a causal inverse relationship between milk consumption and stroke or CHD risk.

Associations between saturated fatty acids from different dietary sources and cardiovascular disease risk in 114,285 UK Biobank study participants

Background

Previous studies suggest that different foods rich in saturated fatty acids (SFA), particularly meat and dairy, have diverging directions of association with risks of total cardiovascular disease (CVD) and CVD subtypes.(1,2)

Purpose

To investigate the associations between SFA from different dietary sources and risks of total CVD, ischaemic heart disease (IHD), and stroke.

Methods

We analysed data on 114,285 UK Biobank participants who had completed ≥2 24-h dietary assessments and were free of CVD at the date of the latest 24-h dietary assessment. Risks of incident (non-fatal and fatal) total CVD, IHD and stroke by intakes of SFA from different sources were estimated using multivariable Cox regressions. Additional models assessed the role of body mass index (BMI) and low-density lipoprotein cholesterol (LDL-C) as potential mediators. We also estimated the associations between modelled isoenergetic substitution of 5% energy from SFA from meat with SFA from dairy, polyunsaturated fatty acids, monounsaturated fatty acids, carbohydrates from whole grains and carbohydrates from fruit and vegetables, and risk of CVD outcomes. A false discovery rate controlling procedure was used to account for multiple testing.

Results

Over a median 8.5 years of follow-up, there were 4,365, 3,394, and 1,041 cases of total CVD, IHD and stroke, respectively. There were no significant associations between total SFA intake and CVD outcomes. SFA from meat was positively associated with total CVD (hazard ratio for each 5% of energy, 1.19; 95% CI, 1.05–1.35) and IHD (1.21; 1.05–1.39) risk independently of lifestyle and cardiovascular risk factors. However, the estimates were attenuated and non-significant for both total CVD (1.11; 0.98–1.26) and IHD (1.12; 0.97–1.29) after adjustment for BMI. SFA from dairy was inversely associated with IHD risk (0.89; 0.82–0.96) in the multivariable model, however this finding was also attenuated after adjustment for BMI and did not pass correction for multiple testing (0.91; 0.84 to 0.98). Modelled replacement of 5% of energy from SFA from meat with carbohydrates from whole grains or carbohydrates from fruit and vegetables were associated with lower risk of stroke in the multivariable model (0.86; 0.78–0.94 & 0.86; 0.78–0.95, respectively) and the model adjusted for BMI and LDL-C (0.87; 0.79–0.96 & 0.86; 0.78–0.95, respectively).

Conclusion(s)

SFA from meat was associated with a higher risk of total CVD and IHD, while SFA from dairy was associated with lower risk of IHD, although BMI seemed to account for a large proportion of these associations. It is possible that diverging associations of SFA from different sources with CVD risk may explain the overall null association with total SFA observed in this study and some previous observational studies. Randomised controlled trials are needed to confirm whether replacing SFA from meat by carbohydrate from wholegrains or fruit and vegetables may be beneficial in reducing stroke risk.

Funding Acknowledgement

Type of funding sources: Public Institution(s). Main funding source(s): Clarendon Fund and Jesus College Clarendon Old Members' AwardJesus College Graduate Scholarship

Association of leukocyte DNA methylation changes with dietary folate and alcohol intake in the EPIC study

Background

There is increasing evidence that folate, an important component of one-carbon metabolism, modulates the epigenome. Alcohol, which can disrupt folate absorption, is also known to affect the epigenome. We investigated the association of dietary folate and alcohol intake on leukocyte DNA methylation levels in the European Prospective Investigation into Cancer and Nutrition (EPIC) study. Leukocyte genome-wide DNA methylation profiles on approximately 450,000 CpG sites were acquired with Illumina HumanMethylation 450K BeadChip measured among 450 women control participants of a case-control study on breast cancer nested within the EPIC cohort. After data preprocessing using surrogate variable analysis to reduce systematic variation, associations of DNA methylation with dietary folate and alcohol intake, assessed with dietary questionnaires, were investigated using CpG site-specific linear models. Specific regions of the methylome were explored using differentially methylated region (DMR) analysis and fused lasso (FL) regressions. The DMR analysis combined results from the feature-specific analysis for a specific chromosome and using distances between features as weights whereas FL regression combined two penalties to encourage sparsity of single features and the difference between two consecutive features.

Results

After correction for multiple testing, intake of dietary folate was not associated with methylation level at any DNA methylation site, while weak associations were observed between alcohol intake and methylation level at CpG sites cg03199996 and cg07382687, with q_val = 0.029 and q_val = 0.048, respectively. Interestingly, the DMR analysis revealed a total of 24 and 90 regions associated with dietary folate and alcohol, respectively. For alcohol intake, 6 of the 15 most significant DMRs were identified through FL.

Conclusions

Alcohol intake was associated with methylation levels at two CpG sites. Evidence from DMR and FL analyses indicated that dietary folate and alcohol intake may be associated with genomic regions with tumor suppressor activity such as the GSDMD and HOXA5 genes. These results were in line with the hypothesis that epigenetic mechanisms play a role in the association between folate and alcohol, although further studies are warranted to clarify the importance of these mechanisms in cancer.

Electronic supplementary material

The online version of this article (10.1186/s13148-019-0637-x) contains supplementary material, which is available to authorized users.