Is saturated fat beneficial after all?
There seems to be no convincing evidence to say that high intake of saturated fat prevents any disease and the evidence about harmful effects is very inconsistent.
Saturated fat and stroke
There is some inconsistent evidence about the association between high saturated fat intake and a decreased or no risk of stroke.
This meta-analysis reveals that higher SFA intake is inversely
associated with risk of stroke morbidity and mortality...(Neurological Sciences, 2016)
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. (systematic review and meta-analysis of observational studies, BMJ, 2015)
Studies on SAFA [saturated fatty acids] intakes and risk of ischemic
stroke are inconsistent. Compared with the abundant data on SAFA
consumption and risk of CHD, there is insufficient evidence to support
dietary SAFA recommendations to reduce stroke risk. (Annals of Nutrition and Metabolism, 2017)
Why has saturated fat been considered harmful?
High saturated fat intake has been associated with increased levels of LDL cholesterol, which in turn has been associated with an increased risk of cardiovascular disease, but this does not automatically mean that saturated fat causes cardiovascular disease (Current Atherosclerosis reports, 2010).
Large studies and study reviews according to which saturated fat intake has been associated with:
The conflicting results can be due to neglecting the effect of other nutrients in the diet and individual differences (Circulation, 2018).
1) The effect of other nutrients on the effect of saturated fat
According to some systematic reviews, replacing some saturated fat with unsaturated fat decreases the risk of heart disease (Cochrane, 2015, NMCD, 2017).
A 2018 Cochrane systematic review have found a weak association between increased intake of polyunsaturated fats and lower risk of cardiovascular disease, but another review in Annals of Internal Medicine, 2014 has not.
It is possible that not every polyunsaturated fat is beneficial. In two meta-analyses, replacing saturated fat with omega-6 polyunsaturated fatty acids was associated with a higher risk of heart disease, and replacing with omega-3 fatty acids with a reduced risk (Cambridge Core, 2010, Nutrition Journal, 2017).
Dairy, despite being high in saturated fat, has not been associated with increased risk of cardiovascular disease (British Journal of Nutrition, 2016, Current Nutrition Reports, 2018). It was suggested that high levels of calcium and vitamin D in milk may counteract the effect of saturated fat (Nutrition Bulletin, 2017).
Red meat and processed meat are both high in saturated fat, but processed meat intake has been associated with much higher risk of heart disease and diabetes 2 than unprocessed red meat (Circulation, 2010, BMC Medicine, 2013). This suggests that it may not be saturated fat but preservatives (sodium, nitrates) in processed meat that can be harmful.
High intake of refined carbohydrates (sugar, plain starch) in combination with saturated fat intake has been associated with increased risk of cardiovascular disease (The Netherlands Journal of Medicine, 2011).
2) Individual differences in response to saturated fat
Individuals who produce small dense LDL particles can be more negatively affected by saturated fat than those who produce large particles.
Because medium and small LDL particles are more highly associated with
cardiovascular disease than are larger LDL, the present results
suggest that very high saturated fat intake may increase
cardiovascular disease risk in phenotype B individuals [who produce a
large percent of small LDL particles]. (Plos One, 2017)
Individuals with increased risk of heart disease seem to be more prone for harmful effects of saturated fat. In a prospective PREDIMED study following 7038 participants at high risk of cardiovascular disease for 6 years, high intake of saturated fat was strongly positively associated (+81%) and unsaturated fat strongly inversely associated (-32-50%) with cardiovascular events and deaths.
In conclusion, the effect of saturated fat on health cannot be evaluated in isolation but only in context of overall diet and individual differences. High saturated fat intake can be harmful in individuals with risk factors for heart disease, but less likely in healthy individuals without risk factors who consume enough whole grains and unsaturated fat. There is no evidence to recommend increasing saturated fat intake.