The effect of consumption of soy foods on metabolic syndrome in women: a case study from peri-urban Qwa-Qwa, South Africa

Objectives: The objective was to determine the long-term effect (18 months) of 40 g daily consumption of whole soy bean on metabolic syndrome (MetS) in apparently healthy women. Design: Single-system experimental design. Subjects and setting: Ninety women were randomly recruited from three communities in Qwa-Qwa, Free State province. Outcome measures: Dietary intake (24-h recall questionnaire), waist circumference (WC), blood pressure, fasting venous blood samples for total serum cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), triglycerides (TRGs) and glucose analyses. Results: The prevalence of MetS was significantly (p < 0.001) reduced from 53.3% to 34.4% after the intervention. The most prominent risk factors were low serum HDL-C and high serum TRG levels followed by obesity (WC). After the intervention, the MetS group had significantly improved mean serum glucose (p = 0.013), systolic (p < 0.001) and diastolic (p < 0.001) blood pressure. No significant improvements were observed in the non-MetS group. Conclusions: The prevalence of MetS is high in black women residing in Qwa-Qwa. Despite the beneficial metabolic effects observed in this study, a relationship between soy protein consumption and MetS risk factors could not statistically be confirmed. However, soy is a source of good-quality protein and is often used in low-income households as a replacement for other more expensive protein sources and the use of soy should not be discontinued as it may have a beneficial effect on MetS and may play a role in preventing MetS. More research is needed in large-scale case-control studies to determine the effect of soy consumption on MetS risk factors. Social media message: Research has shown that soy may be beneficial for ameliorating some of the metabolic syndrome risk factors.