The first prospective analysis to investigate the association between dietary fats and cardiovascular mortality in patients with diabetes.
Diabetes is on the rise, imposing a substantial disease toll and an economic burden on patients and healthcare systems. Cardiovascular disease is the leading cause of death in patients with diabetes. For that reason, dietary guidelines recommend limiting trans fat intake in patients with diabetes, and replacing saturated fats with unsaturated fats to help reduce total and cardiovascular disease mortality. Examples of foods rich in polyunsaturated fatty acids ( PUFAs) include fish, nuts and seeds.
This study is a prospective, longitudinal cohort study that included 11 264 participants with type 2 diabetes in two population-based cohort studies. The objective of this study is to assess the association of specific dietary fats based on their quality with total and cardiovascular mortality among patients with type 2 diabetes. The primary exposure is the dietary fat intake which is assessed using validated food questionnaires and updated every 2-4 years. The primary outcome of the measure is total and cardiovascular disease mortality. Information on lifestyle and other potential risk factors for mortality were assessed at baseline and updated through questionnaires. Cox proportional hazard models were used to calculate hazard ratios and 95% confidence intervals for the associations of different dietary fats with cardiovascular disease mortality, cancer and total mortality. P values below 0.05 were considered to be statistically significant.
During a mean follow up of 11 years, 2502 deaths were documented; 646 of them were due to cardiovascular disease. Women with higher consumption of PUFA appeared to be healthier, and had a shorter duration of diabetes than women with lower PUFA consumption. Similar results were observed with men that had a higher PUFA consumption. Intakes of saturated fatty acids and trans fats were positively associated with higher cardiovascular disease mortality after adjusting for age and sex. However, a significant inverse association was observed with PUFAs and cardiovascular disease mortality. Hazard ratios across quarters of PUFA intake (from low to high) were 1.00, 0.99 (95% confidence interval 0.80 to 1.23), 0.85 (0.67 to 1.08), and 0.76 (0.58 to 0.99) for cardiovascular disease mortality.
On the other hand, monounsaturated fatty acids were not significantly associated with either cardiovascular disease mortality or total mortality. When replacing saturated fatty acids with PUFAs, a 13% ( HR 0.87, 0.77-0.99) decrease in cardiovascular disease mortality was observed and a 12% decrease in total mortality ( HR 0.88, 0.83-0.94).
Some of the strengths of this study are the large sample size, long term follow-up with a high follow-up rate (>90%), and repeated assessments of other lifestyle factors. However, the study also has limitations. Firstly, the severity of diabetes was not rigorously assessed. In addition to that, the study used self-reported questionnaires to assess diet and lifestyle factors which may affect the reliability of the results. Thirdly, the quality of the research is not considered to be high since this is an observational study.
Collectively, these data suggest that intake of PUFAs may exert a beneficial effect on cardiovascular health among people with type 2 diabetes. No significant associations were observed for MUFAs as it relates to cardiovascular disease and total mortality.
- Higher intake of PUFAs is associated with lower total and cardiovascular disease mortality. In addition to that, increasing dietary PUFAs in replacement of saturated fatty acids may facilitate long term survival among patients with diabetes.
- This study is a prospective longitudinal cohort study that included a large sample size of 11, 264 patients diagnosed with type 2 diabetes.
- PUFAs may exert a beneficial effect on cardiovascular health among people with type 2 diabetes.
Jiao J, et al. Dietary fats and mortality among patients with type 2 diabetes: analysis in two population-based cohort studies. BMJ. 2019 10.1136/bmj.l4009
Nadeen Ayad, BCPS, PharmD Candidate, Skaggs School of Pharmacy, University of Colorado