Christine Dawczynski, PhD; Marcus E. Kleber, PhD; Winfried März, PhD; Gerhard Jahreis, PhD; Stefan Lorkowski, PhD
Disclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L14-0322.
Dawczynski C., Kleber M., März W., Jahreis G., Lorkowski S.; Association of Dietary, Circulating, and Supplement Fatty Acids With Coronary Risk. Ann Intern Med. 2014;161:453-454. doi: 10.7326/L14-5018-2
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Published: Ann Intern Med. 2014;161(6):453-454.
TO THE EDITOR:
Chowdhury and colleagues (1) analyzed 8 studies to assess the association between circulating blood levels of SFAs and RR for coronary outcomes (1). From our point of view, the results of NSHDS (Northern Sweden Health and Disease Study) and VIP (Västerbotten Intervention Program) have been misinterpreted, and the studies should be excluded for the following reasons.
First, data from VIP (2, 3) have been included in the evaluation of NSHDS results (4). Second, VIP and NSHDS assessed the association between high intake of SFAs from dairy products (indicated by pentadecanoic acid [C15:0] and heptadecanoic acid [C17:0] or their sum in serum lipid esters) and CVD (3, 4). In both studies, negative associations between milk fat intake and first-ever myocardial infarction were found. Neither of the 2 studies described the impact of total circulating blood levels of SFA on coronary outcomes. Of note, C15:0 and C17:0 contribute only 0.5% to 1.0% of the fatty acids in total phospholipid levels (4). In contrast, the total SFA level in plasma phospholipids ranges between 40% and 45%, which is mainly composed of palmitic acid (C16:0) and stearic acid (C18:0) with approximately 50% to 60% and 30% to 40% of the total SFA level, respectively (5). Thus, C15:0 and C17:0 are markers for milk or ruminant fat intake (3, 4) but not for total SFA intake. However, there are several SFA sources, such as baking margarines, coconut oil, and palm oil, that do not contain C15:0 and C17:0. In agreement with this, we also found that proportions of C15:0 and C17:0 in human erythrocyte membranes are between 1.0% to 2.9% of total SFA levels and show no correlation with the concentration of total SFAs (ClinicalTrials.gov: NCT01437930 and NCT01742468). When we repeated the meta-analysis after excluding VIP and NSHDS results, we found a positive association of total SFA blood levels and coronary outcomes (RR, 1.21 [CI, 1.04 to 1.40]). This finding contradicts the overall conclusion drawn by Chowdhury and colleagues (1).
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