Soy Consumption, Markers of Inflammation, and Endothelial Function

Abstract

OBJECTIVE -To determine the effects of soy consumption on markers of inflammation and endothelial function in postmenopausal women with the metabolic syndrome.RESEARCH DESIGN AND METHODS -This randomized cross-over clinical trial included 42 postmenopausal women with the metabolic syndrome. Participants were randomly assigned to consume a control diet (Dietary Approaches to Stop Hypertension [DASH]), soy protein diet, or soy nut diet, each for 8 weeks. Red meat in the DASH diet (one serving/day) was replaced by soy protein in the soy protein diet and by soy nut in the soy nut diet.RESULTS -For nitric oxide levels, the difference from the control diet was 9.8% (P Ͻ 0.01) on the soy nut and Ϫ1.7% (P ϭ 0.10) on the soy protein diets. The difference from the control diet for serum E-selectin was Ϫ11.4% (P Ͻ 0.01) on the soy nut consumption and Ϫ4.7% (P ϭ 0.19) on the soy protein diet. Soy nut consumption reduced interleukin-18 compared with the control diet (difference from the control diet: Ϫ9.2%, P Ͻ 0.01), but soy protein did not (difference from the control diet: Ϫ4.6%, P ϭ 0.14). For C-reactive protein, the difference from the control diet was Ϫ8.9% (P Ͻ 0.01) on the soy nut diet and Ϫ1.6% (P Ͻ 0.01) on the soy protein diet.CONCLUSIONS -Short-term soy nut consumption reduced some markers of inflammation and increased plasma nitric oxide levels in postmenopausal women with the metabolic syndrome. Diabetes Care 30:967-973, 2007T he metabolic syndrome is a heterogeneous condition accompanied by visceral adiposity, dyslipidemia, hypertension, and insulin resistance (1,2). Elevated blood levels of inflammatory markers such as C-reactive protein (CRP), interleukin (IL)-2, IL-6, IL-18, and tumor necrosis factor (TNF)-␣ and endothelial dysfunction are associated with features of the metabolic syndrome (3-7). Inflammation, insulin resistance, and endothelial function are strongly correlated in individuals with the metabolic syndrome and may influence each other and exacerbate metabolic deterioration (8,9). Estrogen deficiency in postmenopausal women may further aggravate these conditions (10); endothelium-dependent vasodilation declines with aging, particularly in women after menopause (11). Therefore, postmenopausal women with the metabolic syndrome are at greater risk of endothelial dysfunction.Diet plays an important role in the development of the metabolic syndrome, partly through its effects on proinflammatory markers (12). Several studies have examined the effects of diet on serum levels of inflammatory markers and endothelial function (13-17); some have focused on the effects of soy consumption (18 -24). Soy contains fiber, polyunsaturated fat, and phytoestrogens, which are individually associated with lower levels of inflammatory markers and improved endothelial function (12,16,17). Most studies on the effects of soy consumption on these markers have been performed in healthy (18 -20,22-24) or hypercholesterolemic (21) postmenopausal women. We are aware of no study regarding such effects among women with the met...

Soy Protein Intake, Cardiorenal Indices, and C-Reactive Protein in Type 2 Diabetes With Nephropathy

“…Although several short-term studies regarding the effect of soy on kidneyrelated biomarkers and cardiovascular Soy protein and diabetes risk factors are available (4,7,8), to our knowledge this is the first study in which such effects have been assessed for a long period of time (4 years). Thus, the results would be useful in interpreting the stability of soy effects.…”

“…Previous studies have shown that other soy products such as soy nut might have more beneficial effects on cardiovascular risks (7), inflammatory markers (8), and oxidative stress (27) than textured soy protein. Further studies are required to assess the effects of soy nut among type 2 diabetic patients with nephropathy.…”

“…This new pathogenic perspective leads to some therapeutic considerations that can be considered in clinical treatments for diabetic nephropathy (6). Several studies have shown that substitution of soy protein for animal protein might have beneficial effects on lipid profiles (4,7,8), circulating levels of inflammatory biomarkers (9,10), and renal function indexes (4,11). However, most data available in this regard come from short-term clinical trials, and no study has assessed the long-term consumption of soy protein as a stable component of the diet.…”

Does the DASH diet lower blood pressure by altering peripheral vascular function?

“…To our knowledge, the effects of the DASH diet on functional measures of endothelial function such as flow-mediated vasodilatation (FMD) have not been assessed earlier, even though functional or biochemical markers of endothelial function are improved by various dietary manipulations. 15,16 The regulation of blood flow through metabolically important tissues is another potential link between vascular and metabolic function. In particular, adipose tissue blood flow (ATBF) and its rapid response to nutrient intake seem to be markers of metabolic health.…”

Functional foods for dyslipidaemia and cardiovascular risk prevention

“…As foreseen, in neither of these studies (139,140) in individuals with essentially normal cholesterolaemia was there evidence of any significant LDL-C reduction. Finally, beneficial effects of a soya protein-based diet were also recently described in Iranian women with the 'metabolic syndrome' (141) ; these women had also reduced inflammatory markers after soya, as well as reduced insulin resistance (142) . The remarkable effectiveness of this very simple regimen thus reinforces the recommendation to increase the intake of soya proteins for cardiovascular protection.…”