Dietary flax seed in prevention of hypercholesterolemic atherosclerosis

Oxygen free radicals (OFRs) have been implicated in the development of hypercholesterolemic atherosclerosis. Flax seed is the richest source of omega-3 fatty acid and lignans. omega-3 Fatty acid suppresses the production of interleukin-1 (IL-1), tumor necrosis factor (TNF) and leukotriene B-4 (LTB4), and of OFRs by polymorphonuclear leukocytes (PMNLs) and monocytes. Lignans possess anti-platelet activating factor (PAF) activity and are antioxidant. PAF, IL-1, TNF and LTB4 are known to stimulate PMNLs to produce OFRs. Flaxseed would, therefore, reduce the levels of OFRs and hence would prevent the development of hypercholesterolemic atherosclerosis. The effects of dietary flax seed on a high cholesterol diet induced atherosclerosis, lipid profile and OFR-producing activity of PMNLs (PMNL-CZ) were investigated in rabbits. The rabbits were divided into 4 groups: group I, control; group II, flax seed diet (7.5 g/kg daily, orally); group III, 1% cholesterol diet; and group IV, same as group III but received flax seed (7.5 g/kg daily, orally). Blood samples were collected before and after 4 and 8 weeks on their respective diets for biochemical measurements and aortae were removed at the end of 8 weeks for estimation of atherosclerotic changes. The high cholesterol diet increased the serum level of total cholesterol (TC) and PMNL-CL without altering the levels of serum triglycerides (TG). These changes were associated with a marked development of atherosclerosis in the aorta. Flax seed reduced the development of aortic atherosclerosis by 46% and reduced the PMNL-CL without significantly lowering the serum cholesterol. Flax seed in normocholesterolemic rabbits increased serum fetal cholesterol and decreased PMNL-CL without significantly affecting the serum TG. Modest dietary flax seed supplementation is effective in reducing hypercholesterolemic atherosclerosis markedly without lowering serum cholesterol. Its effectiveness against hypercholesterolemic atherosclerosis could be due to suppression of enhanced production of OFRs by PMNLs in hypercholesterolemia. Dietary flax seed supplementation could, therefore, prevent hypercholesterolemia-related heart attack and strokes. (C) 1997 Elsevier Science Ireland Ltd.