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Cholesterol lowering activity of flaxseed |
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A meta-study funded by the Chinese Academy of Science concluded that flaxseed significantly reduced total and LDL-cholesterol but the changes were dependent on the type of intervention, sex, and initial lipid profiles of the subjects [1]. The researchers also concluded that more studies are needed to determine the efficiency of flaxseed on lipid profiles in men and premenopausal women. They investigated twenty-eight studies of randomized controlled trials of flaxseed or its derivatives on lipid profiles in adults and found that flaxseed interventions reduced total and LDL cholesterol by 0.10 mmol/L and 0.08 mmol/L respectively. These reductions translate in a reduction of 3% in mortality. The cholesterol-lowering effects were most apparent in females, mainly in postmenopausal women. These effects were mainly observed in subjects with relatively high initial cholesterol concentrations, as postmenopausal women, who have increased total and LDL cholesterol concentrations as a result of lower estrogen levels. The researchers were not sure if the observed effect of sex was the result of study design or biological differences. Studies with flaxseed oil did not show an effect in total and LDL cholesterol. Flaxseed contains about 0,6% lignans and 28% of fiber, of which 25% is soluble. Dietary soluble fiber has been proven to have cholesterol lowering effects, whereas lignans have been show to reduce total and LDL cholesterol in animals.
A more recent study that was not included in the meta-study found that a daily administration of secoisolariciresinol diglucoside, a flaxseed lignan, could be effective at reducing blood level of cholesterol and hepatic diseases risk in moderately hypercholesterolemic men [2]. In their previous study Fukumitsu and co-workers of the Central Laboratory of
Nippon Flour Mills Co., Ltd. (Kanagawa, Japan) found that the phytochemicals attenuated high-fat, diet-induced hypercholesterolemia in mice. This time they conducted a double-blinded, randomized, and placebo-controlled study in thirty moderately hypercholesterolemic men. They found that the group that were administered with secoisolariciresinol diglucoside showed a significant reduction in the ratio of low-density lipoprotein/high-density lipoprotein cholesterol.
[1] Meta-analysis of the effects of flaxseed interventions on blood lipids. Am J Clin Nutr. 2009 Aug;90(2):288-97.
[2] Flaxseed lignan lowers blood cholesterol and decreases liver disease risk factors in moderately hypercholesterolemic men. Nutr Res. 2010 Jul;30(7):441-6.
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