I had another moment of revelation today, on reading a study which is published on-line and due to appear in next month's edition of the American Journal of Clinical Nutrition . This study followed more than 58,000 Japanese adults over a 14-year period, and assessed the relationship between their saturated fat intake and risk death from a variety of 'cardiovascular' diseases.
Before we go any further, let's go through some terminology. 'Cardiovascular disease' is an umbrella term that essentially covers stroke or conditions related to the heart. Heart-related causes of death include heart attack (myocardial infarction), cardiac arrest (stopping of the heart) and heart failure (when the heart becomes too weak to support life). Strokes come in two main types: ischaemic and haemorrhagic. Ischaemic strokes are the most common types of stroke, and are caused by a blocking of one or more blood vessels in the brain. Haemorrhagic strokes are caused, on the other hand, by bleeding in the brain. These come in two main forms, 'intraparenchymal' and 'subarachnoid haemorrhage'. OK, enough of the technicalities.
For each of these conditions, the authors of the study compared risk of death with intakes of saturated fat. Here's a summary of what they found:
Compared to those eating the least saturated fat, those eating the most were found to be:
At NO increased risk of death due to heart attack, heart failure or cardiac arrest.Now, at least some of these findings should come as no surprise to followers of the scientific literature. We know that saturated fat has consistently not been linked with heart disease risk. Plus, several previous studies have linked higher saturated fat intakes with a reduced risk of stroke, principally haemorrhagic stroke. One theory here, put forward by the authors, is that low levels of cholesterol (perhaps secondary to low saturated fat intake) leads to thin and weak blood vessels in the brain (that are more likely to haemorrhage).
At NO increased risk of death due to subarachnoid haemorrhage.
At REDUCED risk of death due to intraparenchymal haemorrhage (52 per cent reduced risk).
At REDUCED risk of death due to ischaemic stroke (42 per cent reduced risk).
At REDUCED risk of death due to stroke (all types of stroke lumped together) (31 per cent reduced risk).
And, wait for it....
Higher intakes of saturated fat were found to be associated with a REDUCED RISK OF DEATH FROM CARDIOVASCULAR DISEASE (18 per cent reduced risk).
However, the fact that this study linked higher saturated fat intakes with reduced risk of cardiovascular disease was a bit of a shock to me. While the finding is in the results table of the paper, I can't find any mention of it elsewhere. The authors do make this comment, however: "Assuming that the inverse association between SFA [saturated fatty acid] and stroke mortality is causal, it would nevertheless be inappropriate to recommend an increased consumption of SFA-containing products to the general Japanese population, because it might increase population levels of total cholesterol and the risk of IHD [ischaemic heart disease]."
The authors are entitled to express any opinion they like, but this one is simply not supported by their own data. According to their findings, if the Japanese were to increase their saturated fat intake, heart disease deaths would stay the same, stroke deaths would go down, and so would deaths due to cardiovascular disease overall.
1. Yamagishi K, et al. Dietary intake of saturated fatty acids and mortality from cardiovascular disease in Japanese: the Japan Collaborative Cohort Study for Evaluation of Cancer Risk (JACC) Study. Am J Clin Nutri 2010;92(4):759-765