Reducing serum low density lipoprotein-cholesterol (LDL-C) by lowering the intake of saturated fatty acids (SFA) to no more than 10% of total energy, remains the mainstay of dietary guidelines to prevent cardiovascular diseases(1). However, there is marked inter-individual variation in the serum LDL-C response to the lowering of SFA. If the variability of this response exceeds the potential reduction in LDL-C, then this may limit the usefulness of this recommendation in the UK population. The overall aim of the RISSCI project is to investigate the mechansims underlying variation in serum LDL-C to dietary SFA, to inform more personalised dietary approaches. To achieve this aim, a study (RISSCI-1) was designed to reproduce the variation in serum LDL-C seen in large dietary intervention trials(2, 3). Participants showing hyper and hypo-responsiveness to a reduction in SFA could then be selected and retained for further metabolic investigations (RISCCI-2).
In RISSCI-1, healthy men were recruited at the Universities of Reading and Surrey (n = 109, mean age 48 (range 30–65 years), mean BMI 25.2 (range 19.1–33.3 kg/m2), and were asked to follow a high SFA diet (18% total energy) for 4 weeks, and then a diet of lower SFA content, equivalent to that of National dietary guideline (≤ 10% total energy) for a further 4 weeks. Dietary SFA was replaced with mono and polyunsaturated fatty acids (MUFA and PUFA) using a food exchange model(4). The diets were iso-energetic, and dietary intake was determined by 4-day diet diaries (0, 4, 8 weeks). Serum total cholesterol (TC), triacylglycerol (TAG) and HDL-cholesterol (HDL-C) were measured by commercially available colorimetric assays, and LDL-C calculated by the Friedewald formula, at baseline, post-high SFA diet, and post-lower SFA diet.
Replacement of dietary SFA with MUFA and PUFA was achieved with good compliance(4), no effect on BMI, and produced significant reductions in total serum TC and LDL-C of 0.64 (12%) and 0.5 mmol/L (15%), respectively, within 4 weeks (High vs Lower SFA). Inter-individual variation in the change in serum LDL-C ranged from -40% (-1.2mmo/L) to + 20% (3.2mmol/L), and was of a magnitude previously observed in longer-term intervention trials(2, 3).
These findings support the effectiveness of the dietary guideline to replace SFA with MUFA and PUFA to reduce serum LDL-C, in a short-term intervention. They also demonstrate large inter-individual variation in serum LDL-C, which will allow further investigation of the metabolic and/or genetic origins of this phenomenon in RISCCI-2.
Biotechnology & Biological Sciences Research Council Grant No. BB/P010245/1