Lipoprotein(a) [Lp(a)] is a class of lipoprotein associated with an increased rick of cardiovascular disease because it may damage the endothelial linings of the arteries. Lipoprotein(a) is structurally similar to the low density lipoprotein particle, except that it contains an apolipoprotein(a) [apo(a)] particle attached to the apoB particle of the normal LDL particle. The similarity between the two particle led Dr Linus Pauling to suggest that some studies claiming to be measuring LDL were in fact measuring La(a). The normal physiological function of Lp(a) are not understood, but elevated levels (>200mg/dL) increase the risk of developing cardiovascular disease considerably. It was Linus Pauling who suggested that Lp(a) levels become elevated due to a deficiency of vitamin C and that vitamin C in high doses could reduce cardiovascular risk by lowering the plasma level of Lp(a). However, other dietary components may also reduce plasma levels of Lp(a).
Researchers1 have investigated the effects of ground flaxseed on the plasma lipid levels of 62 subjects with plasma LDL cholesterol levels between 130 and 200mg/dL. Subjects were fed 40g of ground flaxseeds per day or a wheat bran product contained within baked products, for 10 weeks. As expected the flax seeds increased the plasma levels of α-linolenic acid (ALA, C18:3 (n-3)) as has been shown previously by other researchers. In addition, subjects consuming flax experienced a reduction in LDL cholesterol at 5 weeks, but by 10 weeks the effects were not significant. More importantly, flax treatment reduced Lp(a) by 14% compared to the control wheat group and reduced the homeostatic model assessment of insulin resistance (HOMA-IR) by 23.7%. Flax supplementation also decreased high density lipoprotein (HDL) cholesterol in men, (16%) but not in women. There was no decrease in inflammatory markers with flax consumption.
The ability of flax to decrease inflammation is controversial. Flax appears unable to inhibit inflammation in most humans due to the limited capacity to convert ALA to eicosapentanoic acid (EPA, C20:5 (n-3)) or docosahexanoic acid (DHA, C22:6 (n-3)). However, results from previous research suggest that flax may have some benefits to cardiovascular disease beyond its ability to prevent inflammation. This study suggests that one such mechanism might be through the modification of plasma lipoproteins, and in particular by reductions in the circulating concentrations of Lp(a). Just how flaxseeds are able to influence blood lipids are unknown, but it may relate to the mineral and vitamin, the fibre or the fatty acids present in the seeds. Flax seeds may therefore reduce the risk of cardiovascular disease through a lowering of Lp(a). Whether this is because of the fatty acids they contain or other components requires further research.
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