Dietary fats and mortality among patients with type 2 diabetes: analysis in two population based cohort studiesBMJ 2019; 366 doi: https://doi.org/10.1136/bmj.l4009 (Published 02 July 2019) Cite this as: BMJ 2019;366:l4009
All rapid responses
Am I missing something? It appears from the tables that replacing mixed carbohydrate with mixed fat (including the usual percentages of saturated and trans fats) will be protective.
For all-cause mortality - HR for highest vs lowest quartile of isocaloric substitution for carbohydrate
SFA - 1.00 (0.85 to 1.19)
MUFA - 0.90 (0.76 to 1.06)
PUFA - 0.68 (0.60 to 0.78)
TFA - 1.08 (0.94 to 1.25)
Trans fatty acids are the only adverse association for the end-point measurable with most accuracy. During the study period industrial plant-based trans fats were phased out of the US diet, leaving mainly ruminant trans-fats, which are not associated with all-cause mortality and, relevant to the current question, have strong protective association with the risk of type 2 diabetes, RR 0.58 (0.46 to 0.74).
Isolated fatty acids are not available in stores. The oldest question in diabetes management is simply, what happens when fat replaces carbohydrate? This study seemingly confirms what was known before the introduction of insulin, that replacing carbohydrate with fat is beneficial, but fails to report this conclusion firmly, concluding instead "Increasing dietary PUFAs, especially linoleic acid and marine n-3 PUFAs, in replacement of saturated fatty acids, may facilitate long term survival among patients with diabetes".
If diabetes impairs long-term health and survival, then not having diabetes or reducing its severity would be a worthwhile clinical aim. It is possible to reverse or significantly improve the pathology of type 2 diabetes in a large proportion of sufferers by, as far as possible, replacing carbohydrate with fat from whole foods and added fats such a butter and olive oil.[2,3] Such diets are not deficient in polyunsaturated fat and can easily attain the upper intake in this study if diets include fish, nuts, and chicken, but the major benefit is the removal of glucose from a physiology unable to tolerate it. Saturated fat behaves differently when carbohydrate is restricted, and is seldom a nutrient of concern in such diets; to quote one paper, "The lower proportion of SFA [in serum TGs and phospholipids] in the context of low carbohydrate intake occurred despite the fact the low carbohydrate diet contained 2.5 times more SFA (i.e., 100 vs. 40 g/day)".
 de Souza Russell J, Mente Andrew, Maroleanu Adriana, Cozma Adrian I, Ha Vanessa, Kishibe Teruko et al. Intake of saturated and trans unsaturated fatty acids and risk of all cause mortality, cardiovascular disease, and type 2 diabetes: systematic review and meta-analysis of observational studies BMJ 2015; 351 :h3978
 Athinarayanan SJ, Adams RN, Hallberg SJ, et al. Long-Term Effects of a Novel Continuous Remote Care Intervention Including Nutritional Ketosis for the Management of Type 2 Diabetes: A 2-Year Non-randomized Clinical Trial. Front Endocrinol (Lausanne). 2019;10:348. Published 2019 Jun 5. doi:10.3389/fendo.2019.00348
 Unwin DJ, Tobin SD, Murray SW, Delon C, Brady AJ. Substantial and Sustained Improvements in Blood Pressure, Weight and Lipid Profiles from a Carbohydrate Restricted Diet: An Observational Study of Insulin Resistant Patients in Primary Care. Int J Environ Res Public Health. 2019 Jul 26;16(15). pii: E2680. doi: 10.3390/ijerph16152680.
 Hyde PN, Sapper TN, Crabtree CD, et al. Dietary carbohydrate restriction improves metabolic syndrome independent of weight loss. JCI Insight. 2019;4(12):e128308. Published 2019 Jun 20. doi:10.1172/jci.insight.128308
Competing interests: I work for PreKure, an online Health Coach Education and certification service. Our courses include instruction in reversing type 2 diabetes using ketogenic and low carbohydrate diets.
Re: Dietary fats and mortality among patients with type 2 diabetes: analysis in two population based cohort studies
The study does not make it clear objectively if the benefits increase proportionally to the degree of unsaturation of fatty acids; this work simply generalizes about this aspect. For example, does consuming eicosapentaenoic acid potentiate the benefits related to the benefits given by a-linolenic acid?
I was hoping to find a biochemical approach that better explains the underlying reason for these benefits.
Competing interests: No competing interests
Results from systematic reviews and meta-analyses of randomized controlled clinical trials are considered more reliable, level I evidence.
In a systematic review and meta-analysis of randomized controlled trials, replacement of saturated fat in the diet with linoleic acid effectively lowers serum cholesterol but does not translate to a lower risk of death from coronary heart disease or all causes. 
Another systematic review and meta-analysis concluded that there is an inverse association between high dairy intake and the risk of developing T2D and CVD in women. 
Another systematic review and meta-analysis of randomized controlled trials concluded that consuming more than four whole eggs per week did not affect cardiovascular risk factors. 
High LDL-C was inversely associated with mortality in most people over 60 years in a systematic review of cohort studies involving 68,094 elderly people. 
In PURE study intake of total fat and each type of fat was associated with lower risk of total mortality, higher saturated fat intake was also associated with lower risk of stroke. 
Meta-analyses of randomized controlled trials found that n-6 and n-3 PUFA diets should be balanced or else mortality could increase. 
Competing interests: No competing interests