Soy Bean Extract; Prepared
Also known as: Soybean extract, soy protein isolate, soy isoflavones, genistein, daidzein, glycitein, Glycine max
Overview
Soybean extract, derived from the Glycine max plant, is a widely used plant-based dietary supplement. It is rich in proteins and phytoestrogens, particularly isoflavones like genistein, daidzein, and glycitein, which exhibit weak estrogen-like activity. This extract is commonly utilized for its potential benefits in managing menopausal symptoms, supporting cardiovascular health, and influencing metabolic regulation. Available in various forms such as isolated soy protein, soy isoflavone concentrates, or whole soy extracts, its efficacy has been extensively studied through numerous randomized controlled trials, systematic reviews, and meta-analyses. While strong evidence supports its role in alleviating menopausal hot flashes, and moderate evidence points to its lipid-lowering effects, its impact on glycemic control is less conclusive.
Benefits
Soybean extract offers several evidence-based benefits, primarily due to its isoflavone content. For menopausal symptom relief, a meta-analysis of 19 RCTs demonstrated that soy isoflavones significantly reduce hot flash frequency by approximately 20.6% and severity by 26.2% compared to placebo, with effects observed within 6 weeks to 12 months of treatment. The evidence for this benefit is strong and consistent across studies. Regarding cardiovascular health, cumulative meta-analyses indicate that soy protein intake modestly lowers total cholesterol and LDL cholesterol, supporting the FDA's heart health claim for soy protein. This effect, while small, is consistent over time. However, for glycemic control, a systematic review and meta-analysis found no significant beneficial effect of soy consumption on fasting plasma glucose, insulin, or HbA1c in patients with type 2 diabetes, suggesting limited efficacy in this area. Additionally, soy supplementation has been shown to have no significant clinical impact on thyroid hormones, with only minimal and clinically insignificant increases in TSH observed.
How it works
Soy isoflavones function as phytoestrogens, interacting with estrogen receptors (ERα and ERβ) in the body. Depending on the tissue context, these interactions can elicit either weak estrogenic or anti-estrogenic effects. Beyond hormonal modulation, isoflavones may influence lipid metabolism by affecting hepatic cholesterol synthesis and clearance pathways. They also possess antioxidant and anti-inflammatory properties, which contribute to their potential cardiovascular benefits. The bioavailability of soy isoflavones is significantly influenced by gut microbiota, which metabolize glycoside forms into more readily absorbed aglycone forms, impacting their overall efficacy.
Side effects
Soy extracts are generally considered safe, with clinical trials reporting no serious adverse effects. Mild gastrointestinal symptoms, such as bloating or nausea, are rare but can occur. There are no consistently reported significant drug interactions. However, caution is advised for individuals with a known soy allergy. While evidence of adverse effects in hormone-sensitive conditions is limited, individuals with such conditions should consult a healthcare professional. No firm contraindications have been established for healthy populations. Studies on thyroid function indicate that soy supplementation causes only minimal and clinically insignificant increases in TSH, with no significant impact on free T3 or free T4 levels, suggesting it does not adversely affect thyroid health in most individuals.
Dosage
For menopausal symptom relief, an effective dosage typically involves 40–80 mg of soy isoflavone aglycone equivalents per day. Noticeable effects can often be observed within 6 weeks of consistent supplementation. To achieve lipid-lowering effects, a higher intake of approximately 20–25 g of soy protein per day is commonly used, with benefits usually appearing after 8–12 weeks or longer. The specific form of isoflavone (e.g., extracted, synthesized, or from whole soy) can influence its efficacy and bioavailability. It is important to consider the duration of supplementation, as some benefits require sustained intake. Upper limits and safety thresholds are generally high, given the overall safety profile, but adherence to recommended dosages is advised.
FAQs
Is soy extract safe for long-term use?
Yes, clinical trials lasting up to 12 months have shown that soy extract has a good safety profile with no serious adverse effects reported.
Does soy extract affect thyroid function?
Soy extract has a minimal and clinically insignificant effect on thyroid hormones, with only slight increases in TSH observed in some studies.
How soon can benefits be expected from soy extract?
Relief from menopausal symptoms may be noticed within 6 weeks, while lipid-lowering effects typically require 8–12 weeks or more of consistent use.
Is soy extract effective for diabetes management?
Current evidence does not support significant benefits of soy extract for glycemic control, including fasting glucose, insulin, or HbA1c levels.
Research Sources
- https://pmc.ncbi.nlm.nih.gov/articles/PMC6946090/ – This systematic review and meta-analysis investigated the effect of soy consumption on glycemic control in type 2 diabetes patients. It concluded that soy had no significant beneficial effect on fasting plasma glucose, insulin, or HbA1c, indicating limited efficacy for diabetes management.
- https://www.ahajournals.org/doi/10.1161/JAHA.119.012458 – This cumulative meta-analysis, supported by the FDA, examined the long-term effects of soy protein on lipid profiles. It found that soy protein modestly lowers total and LDL cholesterol, with a consistent but small effect size observed over time, supporting its heart health claim.
- https://pubmed.ncbi.nlm.nih.gov/22433977/ – This systematic review and meta-analysis of 19 RCTs demonstrated that soy isoflavones significantly reduce both the frequency (by 20.6%) and severity (by 26.2%) of hot flashes in perimenopausal and postmenopausal women compared to placebo, with effects seen over 6 weeks to 12 months.
- https://www.nature.com/articles/s41598-019-40647-x – This systematic review and meta-analysis assessed the impact of soy supplementation on thyroid function. It concluded that soy has no significant effect on thyroid hormones (TSH, free T3, free T4), with only minimal and clinically insignificant increases in TSH observed.
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