New Study: Dietary Saturated Fat is Not Associated with Increased Risk of CVD

A recently published meta-analysis of 43 cohort or nested case-control studies up until July 1, 2018 [1] did not find that higher saturated fat intake is associated with higher risk of cardiovascular disease (CVD) events. This is the first study to examine the effect of total dietary fat intake and the intake of specific fatty acids on CVDs risk based on dose-response meta-analysis of prospective cohort studies. It has been proposed that saturated fat (SFA) and trans fatty acids (TFA) contribute to CVD via inflammatory mechanisms and oxidative stress, mediated through the production of reactive oxygen species (ROS) [2,3]. With respect to trans fatty acids, this new study found that dietary TFA intake had a dose-response association with CVDs risk; specifically a 16% increased risk of CVD with an increased TFA intake of 2% of energy per day, however no association was observed between total fat or dietary saturated fatty acid (SFA) intake and the risk of CVDs [1]. In addition, this meta-analysis found no protective effect from the consumption of either monounsaturated fatty acids (MUFA), or polyunsaturated fatty acids (PUFA) and risk of CVDs, except PUFAs showed a protective effect in sub-group analysis followed up for more than 10 years [1]. These findings do not support 2010 recommendations of the WHO / FAO [4] which continue to influence national dietary guidelines around the world to recommend reducing intake of saturated fat in order to lower the rates of CVD. As well, these new findings call into question the findings of the PREDIMED study [5] and the Lipid Research Clinics Prevalence Follow-up Study [6] that indicate that diets high in polyunsaturated fatty acid (PUFA) and monounsaturated fatty acid (MUFA) and low in saturated fatty acid (SFA) and trans fatty acids (TFA) are associated with reduced CVDs events. The authors caution that;
it is possible that the role of dietary fat played in the development of CVDs might be confounded by the fat sources. For instance, vegetables and fruits play protective roles in the development of CVDs. However, we could not investigate the different effects of fat from animal, vegetables and fruit separately in this current meta-analysis.” [1]

Some thoughts…

For almost 50 years it has been believed that dietary saturated fat intake was a risk factor for CVDs based on the assumption that dietary fat can increase low density lipoprotein (LDL) cholesterol and blood pressure and in turn, increase CVDs risk, however this meta-analysis of 43 cohort studies did not find a positive association between total dietary fat intake or saturated fat intake and CVDs risk. The 2017 Prospective Urban Rural Epidemiological (PURE) study (covered in this earlier article) is the only prospective study to date which covered multiple world regions and which found that total dietary fat and types of dietary fat were not associated with cardiovascular disease or mortality and further, that dietary saturated fat had an inverse association with stroke and a risk of all-cause mortality with higher intake (up to ~14% of energy intake). That is, dietary saturated fat intake was protective. The findings of the current meta-analysis study, combined with the findings of the 2017 PURE study call into question current dietary recommendations which continue to recommend that people limit dietary saturated fat in order to reduce cardiovascular risk. Such recommendations are included in the most recent Canada’s Food Guide which encourages Canadians to “choose foods with healthy fats instead of saturated fat” and to “prepare meals and snacks using ingredients that have little to no added sodium, sugars or saturated fat” (see this article for details) .

Post publication note (April 7, 2019): As I’ve stated in previous articles, I am not opposed to Canada’s new Food Guide. It is a huge improvement over it’s predecessor for many reasons already discussed. My two concerns that I’ve expressed previously remain; (a) that the recommendations for the general population to continue to limit saturated fat because it contributes to CVD has not been conclusively demonstrated. The only thing that has been shown is that saturated fat can raise LDL, but which LDL; the large fluffy sub-fraction, or the small dense sub-fraction? Please see article linked to above for an elaboration. My second concern is that; (b) the amount of carbohydrate in the diet is too high for the large percentage of the population that are metabolically unhealthy. Please see this article for an elaboration.

Author’s Conclusions

The study’s authors concluded that;

This current meta-analysis of cohort studies suggested that total fat, SFA, MUFA, and PUFA intake were not associated with the risk of cardiovascular disease. However, we found that higher TFA intake is associated with greater risk of CVDs in a dose-response fashion. Furthermore, the subgroup analysis found a cardio-protective effect of PUFA in studies followed up for more than 10 years. Dietary guidelines taking these findings into consideration might be more credible.” [1]

If you would like to learn about the types of fats in your diet and how they may impact your health or those of your family, please send me a note through the Contact Me form on the tab above. You can learn more about the services I provide by clicking on the Services tab or having a look in the Shop. To your good health, Joy You can follow me on: Twitter: https://twitter.com/lchfRD Facebook: https://www.facebook.com/BetterByDesignNutrition/ Instagram: https://www.instagram.com/lchf_rd

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References

  1. Zhu Y, Bo Y, Liu Y, Dietary total fat, fatty acids intake, and risk of cardiovascular disease: a dose-response meta-analysis of cohort studies, Lipids in Health and Disease (2019) 18:91, https://doi.org/10.1186/s12944-019-1035-2
  2. Sverdlov AL, Elezaby A, Qin F, Behring JB, Luptak I, Calamaras TD, Siwik DA, Miller EJ, Liesa M, Shirihai OS, et al. Mitochondrial reactive oxygen species mediate cardiac structural, functional, and mitochondrial consequences of diet-induced metabolic heart disease. J Am Heart Assoc. 2016;5:e002555.
  3. Ruparelia N, Chai JT, Fisher EA, Choudhury RP. Inflammatory processes in cardiovascular disease: a route to targeted therapies. Nat Rev Cardiol. 2017;14:133–44.
  4. Nations FaAOotU. Summary of conclusions and dietary recommendations on total fat and fatty acids in fats and fatty acids in human nutrition—report of an expert consultation. Geneva: FAO/WHO; 2010.
  5. Estruch R, Ros E, Salas-Salvado J, Covas MI, Corella D, Aros F, Gomez- Gracia E, Ruiz-Gutierrez V, Fiol M, Lapetra J, et al. Primary prevention of cardiovascular disease with a Mediterranean diet. N Engl J Med. 2013;368:1279–90.
  6. Guasch-Ferre M, Babio N, Martinez-Gonzalez MA, Corella D, Ros E, Martin-Pelaez S, Estruch R, Aros F, Gomez-Gracia E, Fiol M, et al. Dietary fat intake and risk of cardiovascular disease and all-cause mortality in a population at high risk of cardiovascular disease. Am J Clin Nutr. 2015;102:1563–73.
  7. Dehghan M, Mente A, Zhang X, Swaminathan S, Li W, Mohan V, Iqbal R, Kumar R, Wentzel-Viljoen E, Rosengren A, et al. Associations of fats and carbohydrate intake with cardiovascular disease and mortality in 18 countries from five continents (PURE): a prospective cohort study. Lancet. 2017;390:2050–62.
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