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Death and Dietary Fats in Type 2 Diabetes

Aug 17, 2019
 
Editor: David L. Joffe, BSPharm, CDE, FACA

Author: Kassey  James, Pharm.D. Candidate, LECOM School of Pharmacy

A higher intake of polyunsaturated fats is associated with reduced mortality in patients with type 2 diabetes.

The leading cause of death for patients with type 2 diabetes is cardiovascular disease. Current dietary guidelines for the prevention and management of cardiovascular disease state that patients with diabetes should consume high amounts of omega-3 polyunsaturated fatty acids and limit their intake of saturated fatty acids, trans fat, and cholesterol. Since these recommendations are based off data from the general public, this study evaluates whether these recommendations for consumption of polyunsaturated fats can be extrapolated to patients with diabetes.

Two large prospective cohort studies of 11,264 patients with type 2 assessed the associations between fats, cardiovascular related mortality, and total mortality in the United States. This data was taken from validated questionnaires that were completed every two years for the NHS and HPFS ongoing cohort studies. The questionnaire response rate was greater than 90% and completed questionnaires implied informed consent. Exclusion criteria included cancer, cardiovascular disease, and those with an extreme caloric intake (<500 or >3500 kcal/day for women; <800 or >4200 kcal/day for men). Diabetes final patient sample included 1,498 prevalent cases and 9,766 incident cases.

Dietary assessment was done with semiquantitative food frequency questionnaires since the reliability and validity of these assessments have been previously documented. Nutrition composition data came from Harvard Food Composition Database. Physical activity, lifestyle, and risk factors for mortality were assessed at baseline and throughout the study. Deaths were determined by searching the National Death Index, family reports, or postal authorities.

After adjustments were made for age and sex, results revealed an inverse association of total polyunsaturated fatty acids with all-cause mortality and cardiovascular disease mortality. Saturated and trans-fat consumption was positively associated with cardiovascular disease mortality even after adjusting for age and sex, but lost significance when adjustments were made for other variables. Although the total amount of monounsaturated fatty acids was not associated with any increased mortality risk, a greater intake of monounsaturated fatty acids from animal sources was linked to an increased risk of all-cause mortality. No mortality risk was associated with plant derived monounsaturated fatty acids. In addition, saturated fatty acids and monounsaturated fatty acids did not have any associations with cancer mortality.

A recent meta-analysis of four randomized controlled trials supports this study and showed that risk of coronary heart disease can be reduced by 30% by replacing saturated fatty acids with polyunsaturated fatty acids. Also, a recent 30-week intervention study showed that a diet rich in linoleic acid, the most abundant polyunsaturated fatty acid, reduced cholesterol in patients with type 2 diabetes. This intervention study also suggested that n-6 polyunsaturated fatty acids have cardiovascular benefits in patients with and without diabetes. The VITAL trial and REDUCE-IT trial also support the cardiovascular benefits of polyunsaturated fatty acids. Marine n-3 polyunsaturated fatty acids and alpha linolenic acid are inversely related to cancer and consuming these may provide additional protection for patients with diabetes, since they are already at a higher risk of certain cancers.

Limitations of this study include: diabetes management and severity of diabetes was not well documented; self-reported diet and lifestyle questionnaires leave room for error; and this was an observational study. Takeaway of this study is that dietary intake of polyunsaturated fatty acids, specifically linoleic acid and marine n-3, is associated with lower all-cause and cardiovascular mortality in patients with type 2 diabetes.

Practice Pearls:

  • Patients with type 2 diabetes should replace saturated fatty acids or carbohydrates with polyunsaturated fatty acids to improve long term survival odds.
  • Dietary intake of polyunsaturated fatty acids, specifically linoleic acid and marine n-3, are associated with lower all-cause and cardiovascular mortality in patients with type 2 diabetes.
  •  This study confirmed that the current dietary guidelines for the prevention and management of cardiovascular disease — to increase polyunsaturated fats and reduce saturated fatty acids, trans fat, and cholesterol — can be extrapolated to patients with type 2 diabetes.

References:

Jiao, J., Liu, G., Shin, H. J., Hu, F. B., Rimm, E. B., Rexrode, K. M., . . . Sun, Q. (2019). Dietary fats and mortality among patients with type 2 diabetes: Analysis in two population-based cohort studies. Bmj, L4009. doi:10.1136/bmj.l4009

 

Kassey James, Pharm.D.Candidate, LECOM School of Pharmacy