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synergistic or additive effects in lowering serum lipid and HbA1c when provided concurrently with soy protein.
Zhan and Ho (2005) reported greater reduction in TC and greater increase in HDL-C in subjects with baseline TC
higher than 6.22 mmol/l (240 mg/dl). The initial TC had a powerful effect on changes in TC and LCL-C
(Anderson, Johnstone and Cook-Newell, 1995). In the present study, the effects of soy protein isolate on serum
lipid changes were not significant. This may be because the initial serum TC of the subjects in this study was
normal or mildly hypercholesterolemia (ranging from 3.03 to 6.67 mmol/l [117 to 246 mg/dl]). Nutrition
Committee of the American Heart Association (AHA) also concluded that consumption of soy protein does not
appear to have a hypocholesterolemic effect in adults with low or normal cholesterol levels (Erdman, 2000). This
study found a statistically significant reduction of TC in hypercholesterolemic subjects (baseline TC > 5.18
mmol/l [200 mg/dl]) after SPI supplementation.
Previous studies found no effect of SPI supplementation on hs-CRP (Maskarinec et al., 2009). The
present study confirms these results by showing no effect of SPI containing isoflavones on hs-CRP levels
(baseline mean hs-CRP values < 1.6 mg/l) in type 2 diabetic patients. In contrast, some reports described lower hs-
CRP levels with soy protein or isoflavones supplement, when baseline mean hs-CRP values > 3 mg/l (Azadbakht
et al., 2007) and it is probable that soy protein or isoflavones may have an effect only in subjects with elevated hs-
CRP (hs-CRP >3 mg/l). The effects of SPI on hs-CRP must be further investigated, particularly among subjects
with elevated inflammation (end stage renal disease (ESRD)-patients, arthritis, etc.).
This study found that hs-CRP significantly positively correlated with HbA1c. hs-CRP rose as HbA1c
levels increased in individuals with type 2 diabetes, compared to improvements seen in hs-CRP with improved
glucose control (expressed by lowering HbA1c) (Gonzalez-Clemente et al., 2002). Therefore, SPI supplementation
influence tight good glycemic control can slow-down the progression of diabetes complication in diabetic patients
(Fukuhara et al., 2006).
In conclusion, the present study has shown that SPI containing isoflavones may have the additional
benefits reported, including improve glycemic control (HbA1c reduction) and trend toward lowering serum lipids
and hs-CRP from baseline. So it is reasonable to suggest that SPI containing isoflavones improve the some
biomarkers of CVD in type 2 diabetic patients.
Acknowledgement
I am really thankful to the Faculty of Graduate Studies, Chulalongkorn University for the supporting
scholarship which enabled me to undertake this study.
