A dietary exchange model to study inter-individual variation in serum low-density lipoprotein cholesterol response to dietary saturated fat intake

Abstract

A current dietary recommendation to reduce of cardiovascular diseases (CVD) is to decrease intake of dietary saturated fatty acids (SFA) to 10 % total energy. One of the key mechanistic links between SFA and CVD is the impact of SFA in raising serum lowdensity lipoprotein cholesterol (LDL-C). However, this response displays a high degree of inter-individual variation (1). The Reading, Imperial, Surrey Saturated fat Cholesterol Intervention (RISSCI) study has been designed to investigate the metabolic mechanisms underlying this variation in LDL-C response. A dietary exchange model has been developed for the RISSCI study to deliver diets with a high (18 % total energy) and lower (≤ 10 % total energy) content of SFA by its replacement with polyunsaturated (PUFA) and monounsaturated fatty acids (MUFA), to reproduce the variation in LDL-C observed in human intervention studies. This abstract presents interim data as evidence for the efficacy of this dietary exchange model. Data from twenty healthy male participants (51 ± 10 y; 24 ± 3 kg/m 2) recruited at the Universities of Surrey and Reading were included in this interim analysis. A dietary exchange model using exchangeable sources of dietary fat (butter/spreads, oils, dairy foods and snacks)-equating to 40 g/d of fat-was devised for the two 4-week dietary interventions: a high (18 %), followed sequentially by a low (≤10 %) SFA diet. Dietary intakes were assessed at baseline and in the final week of the two dietary intervention periods using 4-day food diaries. Data were analysed using one-way repeated measures ANOVA with the Holm procedure used to correct for multiple pairwise comparisons. Data are presented as mean ± SD. Dietary compositional targets were broadly met (Table), with significantly higher SFA intakes and trends in favour of lower PUFA and MUFA intakes, during the high SFA diet compared to the low SFA diet. There were no other significant differences between the two intervention diets in total energy or other macronutrient intakes. Our initial findings indicate the flexible dietary exchange model was successful in substituting SFA with unsaturated fatty acids in free-living men. This exchange model will be used subsequently in the RISSCI study, to investigate the mechanisms underlying the inter-individual variation in LDL-C response to SFA.

Determination of variability in serum low density lipoprotein cholesterol response to the replacement of dietary saturated fat with unsaturated fat, in the Reading, Imperial, Surrey Saturated fat Cholesterol Intervention (‘RISSCI’) project

“…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 ) .…”

“…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/m 2 ), 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).…”

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“…While variance in dietary compliance may undoubtedly contribute to the variation in response to intervention studies, there is evidence for innate differences in the metabolic handling of SFA and regulation of cholesterol homeostasis, especially between the liver and gut, to explain individual variation in LDL-C. Professor Bruce Griffin and Dr Barbara Fielding described an ongoing collaborative study between the Universities of Surrey, Reading and Imperial College London, which was designed to investigate the mechanisms to explain variation in serum LDL-C response to SFA (15) . The original hypothesis stated that inter-individual variation in serum LDL-C to reduced intake of SFA will be explained by variation in the efficiency of the absorption of dietary SFA, and relative stimulation of LDL receptors.…”

Dietary pattern analysis reveals key food groups contributing to the successful exchange of saturated with unsaturated fatty acids in healthy men

“…The two diets were designed using data from the NDNS years 1–4 rolling programme among men aged 19–64 years (2014) and a previous dietary intervention study “DIVAS” (2) , identifying the following food groups as sources of exchangeable fats: butter/spreads, oils, full-fat and low-fat dairy foods, and snacks. Analysing daily nutrient intakes in a subsample from the same cohort of participants confirmed the two diets both broadly achieved their nutritional targets (3) . Thus, the current analysis aimed to investigate the impact of implementing the exchange of SFA for MUFA/PUFA to overall dietary patterns.…”