Saturated fat won't kill ya...
I figured by now we could put this topic to bed. But in my role as a teacher and editor, I still see popping up, time and time again, the completely outdated notion that saturated fats cause heart disease. 

Now, I’m not one of the wand-waving keto-magis suggesting that saturated fats are a miracle food and that you should drastically increase your intake…BUT I am suggesting that saturated fats, in the context of an otherwise healthy diet, are innocuous for most (almost all) people and that there is no need to restrict them. 

TL:DR – Don’t be scared of saturated fat homie!

Basically, all the reviews of the available scientific evidence show no associat6ion between saturated fat intake and cardiovascular mortality

Reviews of the evidence show no real association between saturated fats and cardiovascular mortality

The majority of systematic reviews and meta-analyses find little or no association between saturated fat intake and CVD mortality.(1-3)  

In a Cochrane review of randomised studies on the effect of modified or reduced fat interventions on total and cardiovascular disease (CVD) by Hooper and colleagues, saturated fats showed no overall effect on either outcome (total mortality: relative risk 0.98, 95% CI: 0.93 to 1.04; and for CVD mortality: relative risk: 0.94, 95% CI 0.85 to 1.04).(4)  

Polyunsaturated fats = good… Saturated fats… = good!

Substitution studies show that replacement of some saturated fat with polyunsaturated fats improves CVD mortality outcomes. For example, Jakobsen et al., showed a positive association between replacing saturated fat with polyunsaturated fat in reducing both total coronary disease events (pooled hazard ratio 0.69; 95% CI 0.59, 0.81) and coronary disease mortality (pooled hazard ratio 0.57; 95% CI 0.42 to 0.77).(5)  However, they did not find that replacing saturated fat with monounsaturated fat or carbohydrate similarly improved outcomes. 

So, it should be concluded that polyunsaturated fats (i.e. essential fats) are important (duh...essential) not that saturated fats are bad. If saturated fat independently worsened outcomes, any reduction by replacement with nutrients deemed ‘heart healthy’ (carbohydrates and monounsaturated fats) should improve outcomes. But it doesn’t… 

In a meta-analysis of fatty acid substitution RCTs Mozaffarian et al., stated that we “cannot distinguish between potentially distinct benefits of increasing polyunsaturated fatty acids (PUFA) versus decreasing saturated fatty acids (SFA).”(6) We all recognise the importance of PUFAs / essential fatty acids. This does not, however, by extension, make saturated fats the ‘bad guy’. 

Jakobsen and colleagues  predicted that substituting PUFA for SFA would reduce the risk of CHD deaths. However, substituting carbohydrate for SFA would increase the risk of CHD deaths, especially in women, and substituting MUFA for SFA would increase the risk of coronary events, but not deaths.(5) The method of reporting replacement of saturated fats with PUFAs and improvements in outcomes vs no (or negative) effects of substitution with other fatty acids or carbohydrates is disingenuous at best and likely results from post-hoc fishing to confirm a previously biased hypothesis. It also seems cavalier to suggest a low-fat, low-saturated fat and high-carbohydrate diet in light of these findings. 

Be aware of whether those Omegas are 3 or 6 though!

Later research has looked more closely at the essential Omega 6 fatty acid linoleic acid, found in greater abundance in the diet than the Omega 3 family of lipids, and often recommended in the form of vegetable oils as a ‘heart healthy’ alternative to saturated fats. Ramsden et al., found in their study of men aged 30-59 years with a recent coronary event that replacement of dietary saturated fats (from animal fats, common margarines, and shortenings) with omega 6 linoleic acid (from safflower oil and safflower oil polyunsaturated margarine) increased rates of death, cardiovascular and coronary heart disease. They also performed a meta-analysis of the use of linoleic acid intervention trials, concluding “In this cohort, substituting dietary linoleic acid in place of saturated fats increased the rates of death from all causes, coronary heart disease, and cardiovascular disease. An updated meta-analysis of linoleic acid intervention trials showed no evidence of cardiovascular benefit. These findings could have important implications for worldwide dietary advice to substitute omega 6 linoleic acid, or polyunsaturated fats in general, for saturated fats.”(7)

What does this mean?

Based on the weight of evidence, saturated fats in the context of an otherwise healthy diet don’t increase your risk of either cardiac disease, mortality, or all-cause mortality. 

So, while increasing to excess your intake of ANY nutrient is not a good idea… you shouldn’t be scared of saturated fats homie!

 References

1. Skeaff CM, Miller J. Dietary fat and coronary heart disease: summary of evidence from prospective cohort and randomised controlled trials. Ann Nutr Metab. 2009;55(1-3):173-201.

2. Siri-Tarino PW, Sun Q, Hu FB, Krauss RM. Meta-analysis of prospective cohort studies evaluating the association of saturated fat with cardiovascular disease. The American journal of clinical nutrition. 2010;91(3):535-46.

3. Mente A, de Koning L, Shannon HS, Anand SS. A systematic review of the evidence supporting a causal link between dietary factors and coronary heart disease. Arch Intern Med. 2009;169(7):659-69.

4. Hooper L, Summerbell CD, Thompson R, Sills D, Roberts FG, Moore H, et al. Reduced or modified dietary fat for preventing cardiovascular disease. Cochrane Database Syst Rev. 2011(7):CD002137.

5. Jakobsen MU, O'Reilly EJ, Heitmann BL, Pereira MA, Balter K, Fraser GE, et al. Major types of dietary fat and risk of coronary heart disease: a pooled analysis of 11 cohort studies. Am J Clin Nutr. 2009;89(5):1425-32.

6. Mozaffarian D, Micha R, Wallace S. 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 Med. 2010;7(3):e1000252.

7. Ramsden CE, Zamora D, Leelarthaepin B, Majchrzak-Hong SF, Faurot KR, Suchindran CM, et al. Use of dietary linoleic acid for secondary prevention of coronary heart disease and death: evaluation of recovered data from the Sydney Diet Heart Study and updated meta-analysis. BMJ. 2013;346.

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