The beneficial effects of estrogens on the vascular elasticity and the reduction of the cholesterol level are very important. This is the reason why arteriosclerosis appears in women mainly after the menopause when the estrogen level decreases.
Influence of isoflavones on cholesterol
Supplements containing isoflavones have been investigated for their role in cardiovascular risk reduction. Studies in animals and humans have shown that isoflavones can reduce total and Low Density Lipoprotein (LDL) cholesterol, particularly in people with increased cholesterol levels. A trial involving 156 healthy men and women, intake of soya protein providing 62mg isoflavones was associated with a significant reduction in total and LDL cholesterol compared with isoflavone-free soya protein.The exact mechanism of the cholesterol lowering activity is not determined yet .
Influence of isoflavones on arteries
Isoflavones may play a greater role in improving vascular functions than in reducing cholesterol. Isoflavones can help in the preservation of the vascular elasticity because the estrogen beta-receptor are present in the walls of the arteries.
In particular the isoflavoon genistein stops the blood plates from attaching to the wall of the blood vesels. When arteries are damaged by atherosclerosis they usually form blood clots. These blood clots can cause a heart attack or a stroke. With the help of other antioxidants such as vitamin E and vitamin C, the free radicals are destroyed and the oxidation of LDL Cholesterol (bad cholesterol) is prevented. A study by Sanmugam Nagarajan et al (2006) showed that soy isoflavones reduce the risk of atherosclerosis . This study concluded that anti-atherosclerosis effect of soy isoflavones is the result of the inhibition of the interaction between monocytes and endothelial cells.
Jiang YB and Yang of the Xiamen University, China, found that dietary supplementation of broilers with Trifolium pratense isoflavones reduced pulmonary hypertension syndrome incidence and improved pulmonary vascular remodeling without affecting their growth . The researchers think that this beneficial effect came from isoflavonesthat improved pulmonary vascular remodelling. Isoflavones induced inducible nitric oxide synthase expression and downregulated the expression of endothelin. They concluded that dietary supplementation of Trifolium pratense isoflavones might be a potential candidate for the treatment of pulmonary hypertension.
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 Soy isoflavones attenuate human monocyte adhesion to endothelial cell-specific CD54 by inhibiting monocyte CD11a. J Nutr. 2006 Sep;136(9):2384-90
 Trifolium pratense isoflavones improve pulmonary vascular remodelling in broiler chickens. J Anim Physiol Anim Nutr (Berl). 2015 Dec 15.