Whole flaxseed consumption lowers serum LDL-cholesterol and lipoprotein(a) concentrations in postmenopausal women

We conducted a double-blind cross-over study to compare the effects of whole flaxseed and sunflower seed, as part of the daily diet, on the lipid profile of postmenopausal women. During two 6-wk periods, thirty-eight mild, moderate, or severely (5.85-9.05 mmol/L) hypercholesterolemic postmenopausal women were randomly assigned to one of the two regimens: flaxseed or sunflower seed. The subjects were provided with 38 g of either treatment in the forms of breads and muffins. The first treatment period lasted six weeks and was followed by a two-wk washout phase. After the washout phase, subjects switched regimens and treatments continued for another 6 weeks. Blood samples were collected at baseline, 6, 8, and 14th wk of the study periods. Significant (p<0.01) reductions in total cholesterol were observed for both treatments (6.9 and 5.5% for flaxseed and sunflower seed, respectively). However only flaxseed regimen was able to significantly (p<0.001) lower LDL-cholesterol (14.7%). Serum HDL-cholesterol and triglyceride concentrations were unaffected by either of the treatments. Most interestingly, lipoprotein(a) [Lp(a)], a strong predictor of cardiovascular disease, concentrations were significantly (p<0.05) lowered by the flaxseed treatment (7.4% compared to baseline values). Regression analyses showed the strongest association between age and both total and LDL-cholesterol concentrations. Among the dietary variables, total and soluble fiber intakes were negatively correlated with serum total and LDL-cholesterol concentrations. The cholesterol lowering effects of flaxseed and sunflower seed may be due to the activity of single or multiple components, including alpha-linolenic or linoleic acids, total and soluble fiber, and non-protein constituents present in these seeds.