Phytoestrogens and Cardiovascular Disease
Where’s the Meat?
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The potential role of phytoestrogens in postmenopausal women’s health has been an area of intense interest in recent years and, a report1 in this issue of Arteriosclerosis, Thrombosis, and Vascular Biology adds to this body of knowledge. While there are several different classes of phytoestrogens, much of the recent phytoestrogen research has focused on the isoflavones, most common in soybeans, with some attention on lignans that are abundant in flaxseed. Since cardiovascular disease (CVD) is the leading cause of death in postmenopausal women, it is important that potential new therapies have proven benefits for CVD risk. Although there are many women taking phytoestrogens to maintain their health postmenopausally, there is only one rather small observational study that has linked phytoestrogen intake with cardiovascular morbidity or mortality.2 The results of this nested case-control study were that serum enterolactone concentrations (a lignan metabolite) were lower in men with acute coronary events compared with controls.2
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What is the evidence that phytoestrogens might reduce CVD risk? Data in animal models have shown that soy protein with its isoflavones, compared with isoflavone-devoid soy, can inhibit atherosclerosis.3–6⇓⇓⇓ One study in rabbits found that high doses of an isoflavone extract reduced atherosclerosis.7 Two studies in rabbits found an anti-atherogenic effect of flaxseed containing lignans,8,9⇓ and in one, treatment with the primary lignan in flax inhibited atherogenesis.9 Recent cardiovascular research with phytoestrogens in humans has focused largely on risk factors for CVD, including plasma lipoprotein concentrations and to a lesser extent vascular function, LDL oxidation, and blood pressure.10,11⇓ Much of the research in humans to date has been small, short-term clinical trials using relatively high amounts of soy, isoflavone, or flaxseed supplementation. Taken on balance, these studies suggest that soy with higher …