Saturated fats: do they cause heart disease?

For press reports and expert analyses challenging the hypothesis that saturated fats cause heart disease, click here.

The following is a list of review papers and meta-analyses from the past 5 years.

In recent years, there have been a total of at least 17 meta-analyses and systematic reviews, plus 5 non-systematic reviews that have have failed to find a clear link between saturated fats and heart disease/cardiovascular death:

–3 meta-analyses (2, 4, 11), 3 systematic reviews (2, 4, 12)) and 2 non-systematic reviews (3, 13) examined epidemiological data (the kind of evidence that can show association but not causation) and found that saturated fats are not associated with heart disease (in one review, polys but not carbs were found to pose less cardiovascular risk).

–5 meta-analyses (1, 4, 5, 9, 15), 6 systematic reviews (1, 4, 5, 8, 12, 15) and 3 non-systematic reviews (3, 10, 13) examined clinical trials (the more rigorous kind of data that can demonstrate cause and effect), and found no effect of saturated fats on either heart disease, cardiovascular mortality or total mortality. In some analyses, replacing saturated fats with polyunsaturated vegetable oils reduce cardiovascular events (but not deaths). In one analysis looking only at cardiovascular events (14), a benefit was seen in replacing saturated fats with polyunsaturated vegetable oils.

There have also been commentaries and other non-systematic reviews (6, 7, 8)

Some of these reviews (4), have been controversial, and details of debates about those reviews is forthcoming

  1. Reduction in saturated fat intake for cardiovascular disease,” (systematic review and meta-analysis of randomized, controlled clinical trials)Hooper, L. et al., Cochrane Database Systematic Review, 2015, an independent organization of scientists
    Details: This is a systematic review and meta-analysis of randomized controlled trials, performed by the Cochrane collaboration – an independent organization of scientists. The trials reviewed include more than 59,000 participants.
    Results: The study found no statistically significant effects of reducing saturated fat, in regard to heart attacks, strokes or all-cause deaths.  Although reducing saturated fat had no effects, replacing some of it with polyunsaturated fat led to a 27% lower risk of cardiovascular events (but not death, heart attacks or strokes). Conclusion: People who reduced their saturated fat intake were just as likely to die, or get heart attacks or strokes, compared to those who ate more saturated fat. However, partially replacing saturated fat with polyunsaturated fat may reduce the risk of cardiovascular events (but not death, heart attacks or strokes).
  2. “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.” (on observational data)
    • The BMJ (Clinical Research ed.) (2015)
      R.J. de Souza, Department of Clinical Epidemiology and Biostatistics, McMaster University, Chanchlani Research Centre, McMaster University, A. Mente, Population Health Research Institute, McMaster University, et al.
    • Conclusion: “Saturated fats are not associated with all cause mortality, CVD, CHD, ischemic stroke, or type 2 diabetes, but the evidence is heterogeneous with methodological limitations.”
  3. “Saturated Fats Versus Polyunsaturated Fats Versus Carbohydrates for Cardiovascular Disease Prevention and Treatment”
    • Annual Review of Nutrition (2015)
      Patty W. Siri-Tarino, PhD, Sally Chiu, PhD, Nathalie Bergeron, PhD, and Ronald M. Krauss, PhD, Atherosclerosis Research Program, Children’s Hospital Oakland Research Institute, Oakland, California
    • Conclusion: “Replacement of SFAs with polyunsaturated fatty acids has been associated with reduced CVD risk, although there is heterogeneity in both fatty acid categories. In contrast, replacement of SFAs with carbohydrates, particularly sugar, has been associated with no improvement or even a worsening of CVD risk, at least in part through effects on atherogenic dyslipidemia, a cluster of traits including small, dense low-density lipoprotein particles.”
  4. Association of Dietary, Circulating, and Supplement Fatty Acids with Coronary Risk: A Systematic Review and Meta-analysis” (on observational data and RCTs)
    • Annals of Internal Medicine (2014)
      Rajiv Chowdhury, MD, PhD, University of Cambridge, Samantha Warnakula, University of Cambridge, et al.
    • Conclusion: “Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.”
  5. “Dietary fatty acids in the secondary prevention of coronary heart disease: a systematic review, meta-analysis and meta-regression,” (on clinical trials)
    • BMJ Open (2014)
      Lukas Schwingshackl and Georg Hoffman, Faculty of Life Sciences, Department of Nutritional Sciences, University of Vienna, Vienna, Austria
    • Conclusion: (looking only at subjects with existing CVD) The present systematic review provides no evidence (moderate quality evidence) for the beneficial effects of reduced/modified fat diets in the secondary prevention of coronary heart disease. Recommending higher intakes of polyunsaturated fatty acids in replacement of saturated fatty acids was not associated with risk reduction.
  6. The Questionable Benefits of Exchanging Saturated Fat With Polyunsaturated Fat” (Commentary)
    • Mayo Clinic Proceedings (2014)
      Ravnskov, Uffe, MD, PhD, independent investigator, et al.
    • Conclusion: “The benefits of replacing SFAs with PUFAs are questionable. There is no evidence that a lower intake of SFA can prevent CVD and a high intake of PUFAs without specification may result in a high intake of omega-6, which is associated with many adverse health effects. Because there is much evidence that saturated fat may even be beneficial, we urge the American Heart Association, the American Diabetes Association, and the National Institute of Clinical Excellence to consider the aforementioned evidence when updating their future guidelines.”
  7. Chewing the Saturated Fat? Should We or Shouldn’t We?
    • New Zealand Medical Journal (2014) (Commentary)
      Simon Thornley, University of Auckland, George Henderson, Auckland University of Technology, and Grant Schofield, Auckland University of Technology
    • Conclusions: “…randomised trial data, which is superior to the observational evidence offered by Jakobsen, does not support either limiting or altering saturated fat intake to improve survival.”
  8. Dietary Fats and Health: Dietary Recommendations in the Context of Scientific Evidence” (Review paper)
    • Advances in Nutrition (2013)
      Lawrence, G. D., Department of Chemistry and Biochemistry, Long Island University.
    • Conclusion: “Saturated fats are benign with regard to inflammatory effects, as are the MUFAs. The meager effect that saturated fats have on serum cholesterol levels when modest but adequate amounts of polyunsaturated oils are included in the diet, and the lack of any clear evidence that saturated fats are promoting any of the conditions that can be attributed to PUFA makes one wonder how saturated fats got such a bad reputation in the health literature. The influence of dietary fats on serum cholesterol has been overstated, and a physiological mechanism for saturated fats causing heart disease is still missing.
    • “Various aldehydes produced in the oxidation of PUFAs, as well as sugars, are known to initiate or augment several diseases, such as cancer, inflammation, asthma, type 2 diabetes, atherosclerosis, and endothelial dysfunction. Saturated fats per se may not be responsible for many of the adverse health effects with which they have been associated; instead, oxidation of PUFAs in those foods may be the cause of any associations that have been found. Consequently, the dietary recommendations to restrict saturated fats in the diet should be revised to reflect differences in handling before consumption, e.g., dairy fats are generally not heated to high temperatures. It is time to reevaluate the dietary recommendations that focus on lowering serum cholesterol and to use a more holistic approach to dietary policy.”
  9. Reduced or Modified Dietary Fat For Preventing Cardiovascular Disease” (Systematic Review and Meta-analysis) (Analysis of clinical trials)
    • Cochrane Database Syst Review (2012), An independent organization of scientists who specialize in systematic reviews. This review is an update on one conducted in 2011.
      Hooper L, Norwich Medical School, University of East Anglia, Summerbell CD, Thompson R, et al.
    • Conclusions: “Reducing saturated fat by reducing and/or modifying dietary fat reduced the risk of cardiovascular events by 14%. There were no clear effects of dietary fat changes on total mortality (RR 0.98, 95% CI 0.93 to 1.04, 71,790 participants) or cardiovascular mortality (RR 0.94, 95% CI 0.85 to 1.04, 65,978 participants).”
  10. Saturated Fat, Carbohydrate, and Cardiovascular Disease” (Review of clinical trials)
    • American Journal of Clinical Nutrition (2010)
      Siri-Tarino PW, Children’s Hospital, Oakland Research Institute Oakland, Sun Q, MD, Departments of Nutrition and Epidemiology, Harvard School of Public Health, Hu FB, MD, Departments of Nutrition and Epidemiology, Harvard School of Public Health, et al.
    • Conclusions: “Although substitution of dietary polyunsaturated fat for saturated fat has been shown to lower CVD risk, there are few epidemiologic or clinical trial data to support a benefit of replacing saturated fat with carbohydrate.”
  11. Meta-analysis of Prospective Cohort Studies Evaluating the Association of Saturated Fat with Cardiovascular Disease
    • American Journal of Clinical Nutrition (2010)
      Siri-Tarino PW, Children’s Hospital, Oakland Research Institute Oakland, Sun Q, MD, Departments of Nutrition and Epidemiology, Harvard School of Public Health, Hu FB, MD, Departments of Nutrition and Epidemiology, Harvard School of Public Health, et al.
    • Conclusions: “A meta-analysis of prospective epidemiologic studies showed that there is no significant evidence for concluding that dietary saturated fat is associated with an increased risk of CHD or CVD. More data are needed to elucidate whether CVD risks are likely to be influenced by the specific nutrients used to replace saturated fat.”
  12. A Systematic Review of the Evidence Supporting a Causal Link Between Dietary Factors and Coronary Heart Disease” (review of observational data and clinical trials)
    • Archives of Internal Medicine (2009)
      Andrew Mente, MA, PhD, Associate Professor, Department of Clinical Epidemiology & Biostatistics, McMaster University, Lawrence de Koning, Clinical Assistant Professor, Department of Pathology and Laboratory Medicine, Pediatrics, University of Calgary, et al.
    • Conclusions: “The evidence supports a valid association of a limited number of dietary factors and dietary patterns with CHD…. Insufficient evidence (< or =2 criteria) of association is present for intake of supplementary vitamin E and ascorbic acid (vitamin C); saturated and polyunsaturated fatty acids;…”
  13. Dietary Fat and Coronary Heart Disease: Summary of Evidence From Prospective Cohort and Randomised Controlled Trials” (review of observational data and clinical trials)
    • Annals of Nutrition and Metabolism (2009)
      Skeaff CM, PhD, Professor, Dept. of Human Nutrition, the University of Otago, Miller J.
    • Conclusions: “Intake of SFA was not significantly associated with CHD mortality, with a RR of 1.14 (95% CI 0.82–1.60, p = 0.431) for those in the highest compared with the lowest category of SFA intake (fig. 6). Similarly SFA intake was not significantly associated CHD events (RR 0.93, 95% CI 0.83–1.05, p = 0.269 for high vs. low categories). More- over, there was no significant association with CHD death (RR 1.11, 95% CI 0.75–1.65, p = 0.593) per 5% TE increment in SFA intake.”
  14. Effects on Coronary Heart Disease of Increasing Polyunsaturated Fat in Place of Saturated Fat: A Systematic Review and Meta-analysis of Randomized Controlled Trials
    • PLOS Medicine (2010)
      Mozaffarian D, Department of Epidemiology, Harvard School of Public Health, Micha R, Department of Epidemiology, Harvard School of Public Health, and Wallace S, Department of Epidemiology, Harvard School of Public Health.
    • Conclusions: “These findings provide evidence that consuming PUFA in place of SFA reduces CHD events in RCTs. This suggests that rather than trying to lower PUFA consumption, a shift toward greater population PUFA consumption in place of SFA would significantly reduce rates of CHD”
  15. “Re-evaluation of the traditional diet-heart hypothesis: analysis of recovered data from Minnesota Coronary Experiment (1968-73)” The BMJ 2016, starting p. 7. (on RCT data)

    • Details: This paper contains, as a separate piece of research, a systematic review and meta-analysis of clinical trials in which saturated fats were replaced by “oils rich in linoleic acid (such as corn oil, sunflower oil, safflower oil, cottonseed oil, or soybean oil).” (5 trials, 10,808 participants)
    • Results: “There was no evidence of benefit on mortality from coronary heart disease (hazard ratio 1.13, 95% confidence interval 0.83 to 1.54).”
    • Conclusion: “Although limited, available evidence from randomized controlled trials provides no indication of benefit on coronary heart disease or all cause mortality from replacing saturated fat with linoleic acid rich vegetable oils.”