Dietary lipid intake influences the level of cholesterol bound to haemoglobin in human erythrocytes

Abstract

Background Blood cholesterol levels are affected by diet and in particular by the type of fat intake. We originally showed that a significant but variable amount of cholesterol is firmly bound to haemoglobin (Hb) yielding the Hb-lipid adduct (Hb-Ch) in erythrocytes isolated from normo-lipidemic males. Aim of the study To establish whether dietary lipids affect the level of Hb-Ch in human erythrocytes. Methods Seventy-four healthy free-living adults were separated according to their serum cholesterol levels into two groups: normo-cholesterolemic (LDL cholesterol lt 3.4 mmol/l and total cholesterol lt 5.2 mmol/l) (NC) and hyper-cholesterolemic (LDL cholesterol gt = 3.4 mmol/l) (HC). Habitual dietary information was used to classify subjects in both study groups into sub-groups of low-fat ( lt = 30% total energy as fat) and high-fat consumers ( gt 30% total energy as fat). The NC low-fat consumers were placed on a high-lipid (high-fat and high-cholesterol) diet whereas the HC subjects with high-fat intake were assigned to a low-lipid (low-fat and low-cholesterol) diet. Both types of dietary intervention were allowed to continue for 6 weeks. The main variable under scrutiny was the Hb-Ch concentration. Results In both study groups low-fat intake subjects had low levels of Hb-Ch (approx. 0.35 mmol/l RBC) compared with high-fat intake subjects (approx. 0.60 mmol/l RBC), and serum cholesterol was not correlated with Hb-Ch. The two dietary interventions produced substantial changes in the Hb-Ch level that paralleled variation in the serum cholesterol concentration. A high-lipid diet (35% fat, 15% saturated; 580 mg cholesterol) increased Hb-Ch (by approximately 47%, P lt 0.001) in subjects with low Hb-Ch at onset, whereas a low-lipid diet (28% fat, 9% saturated; 280 mg cholesterol) decreased Hb-Ch (by approximately 40%, P lt 0.001) in subjects with high Hb-Ch at onset. Conclusion High consumption of dietary lipids, including saturated fat and cholesterol, has an important influence on the level of Hb-Ch in human erythrocytes.