Soy Isoflavone Dietary Supplement Helps Improve Functioning Of Arteries In Stroke Patients

A dietary supplement containing Isoflavone, a naturally-occurring nutritive bio-chemical (phyto-estrogen) found in soybeans, chickpeas and legumes - can improve artery function in stroke patients according to important new research.

The study is believed to be the first randomized controlled trial to investigate the effects of an Isoflavone supplement on the way the brachial artery (the main artery in the arm) dilates in response to an increase in blood flow.

This phenomenon is known as flow-mediated dilation (FMD) - in patients with established cardiovascular disease. Brachial FMD is an indicator of the functioning of the cells that line the inner surfaces of blood vessels (vascular endothelium), and endothelial dysfunction is implicated in cardiovascular disease.

The Cardiology Division in the Department of Medicine, Queen Mary Hospital, The University of Hong Kong (Hong Kong, China) research team found that 12 weeks of Isoflavone supplementation, at a dose of 80 mg a day, significantly improved brachial FMD and, therefore, vascular endothelial dysfunction in patients who had suffered an ischaemic stroke (a stroke caused by blood clots or other obstructions).

These findings may have important implications for the use of Isoflavone for secondary prevention in patients with cardiovascular disease, in addition to conventional treatments.

The trial was a double-blind, placebo-controlled trial, involving 50 patients taking the Isoflavone supplement, and 52 taking a placebo pill. The research team explained: "The relative increase actually amounted to about 50%. The therapeutic effect of Isoflavone in the study was comparable with lifestyle changes with endurance training or pharmacological interventions with statin therapy."

In addition, the prevalence of impaired FMD after 12 weeks became significantly lower in Isoflavone-treated patients than in the controls (isoflavone: 58%, control: 79%). There was also a greater effect in patients with more severe endothelial dysfunction.

The patients who had a lower initial FMD were found, in general, to respond with a larger absolute increase in FMD after receiving 12 weeks of Isoflavone intervention, compared to patients who had a better baseline FMD in the first place. These findings suggest that Isoflavone has the ability to reverse endothelial dysfunction in this group of patients with cardiovascular disease.

This has important clinical implications, as the benefit of the treatment is conferred to the group of patients with the highest risks for cardiovascular events, and this effect persists.

No improvement from Isoflavone treatment was found in diabetic patients compared with non-diabetic patients, but there was an improvement of one per cent in patients who were current smokers or who had smoked in the past compared with non- or never smokers. Since smoking is known to be associated with more severe endothelial dysfunction, this observation was coherent with the hypothesis that patients with worse baseline endothelial function are, in general, more responsive to Isoflavone supplementation.

The researchers also found that 12 weeks of Isoflavone supplementation therapy resulted in a significant decrease in levels of high-sensitivity C- reactive protein. This protein increases during systemic inflammation and is an independent predictor of cardiovascular-related events. These findings suggested that Isoflavone treatment alleviated vascular inflammatory stress and was an important component that mediated the reversal of endothelial dysfunction.

The researchers further explained that the mechanisms by which Isoflavone produces these changes in FMD were not completely understood. Other than the anti-inflammatory effect observed in this study, Isoflavone is a major class of phytoestrogens - naturally occurring chemicals that mimic the effect of the human hormone oestrogen. Oestrogen is known to protect against heart disease and so this could be a possible mechanism.

A balanced diet is still the top priority in promoting health. Diets with higher soy content might be beneficial due to the Isoflavone contents. These food products also, in general, have higher contents of polyunsaturated fats, fiber, vitamins and less saturated fat.

Journal reference: Reduction of C-reactive protein with isoflavone supplement reverses endothelial dysfunction in patients with ischaemic stroke. European Heart Journal, September 23, 2008