Effects of Soy Consumption on Men's Health: Hormonal, Cardiovascular, and Reproductive Aspects

Soy Consumption and Men’s Health

Soy consumption has been a topic of extensive research due to its potential effects on human health, particularly in men. Soy products contain isoflavones, which are phytoestrogen that can mimic the effects of estrogen in the body. This review examines the effects of soy consumption on men’s health, focusing on hormonal balance, cardiovascular health, and reproductive function.

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Hormonal Effects of Soy Consumption

Testosterone Levels and Reproductive Hormones

Soy isoflavones have been studied for their potential impact on testosterone levels and other reproductive hormones. Some studies suggest that high doses of soy isoflavones may suppress testosterone production. For instance, a study on male rats found that soy protein isolate supplementation decreased testosterone levels and disrupted the expression of genes involved in testosterone biosynthesis (El‑Latif et al., 2024). Similarly, another study observed that genistein, a major isoflavone in soy, inhibited testosterone production in Leydig cells by upregulating estrogen receptor alpha and downregulating cytochrome P45017A1 (Yang et al., 2022).

However, human studies have yielded mixed results. A randomized controlled trial involving men with type 2 diabetes and subclinical hypogonadism found no significant changes in total or free testosterone levels after soy protein isolate supplementation (Sathyapalan et al., 2016). Another study on healthy young men consuming soy protein isolate with varying isoflavone content observed minor decreases in dihydrotestosterone (DHT) and the DHT/testosterone ratio, but no significant changes in overall testosterone levels (Dillingham et al., 2005). These findings suggest that while soy isoflavones may have some hormonal effects, they are unlikely to cause significant disruptions in healthy men.

Estrogen Receptor Modulation

Isoflavones in soy can bind to estrogen receptors, which may lead to changes in estrogen receptor expression. A study on male Wistar rats found that soy milk exposure reduced the expression of estrogen receptor alpha (ERα) in the medial preoptic area (MPOA) and spermatogonia cells, potentially affecting reproductive function (Nurdiana et al., 2023). However, the clinical relevance of these findings in humans remains unclear.

Cardiovascular Health and Soy Consumption

Reduction in Cardiovascular Disease Risk

Soy consumption has been associated with a reduced risk of cardiovascular diseases (CVD). A meta-analysis of cohort studies found that high soy intake was linked to a 13% lower risk of CVD, including coronary heart disease and stroke (Zuo et al., 2023). The beneficial effects of soy on cardiovascular health may be attributed to its ability to improve lipid profiles, lower blood pressure, and enhance endothelial function.

Mechanisms of Cardiovascular Protection

Isoflavones in soy are thought to play a key role in cardiovascular protection. They have been shown to improve endothelial function by increasing nitric oxide production and reducing oxidative stress (Yamagata, 2019). Additionally, soy isoflavones may inhibit the oxidation of low‑density lipoprotein (LDL) cholesterol, which is a major contributor to atherosclerosis (Yamagata, 2019).

Effects on Blood Lipids

Soy protein has been shown to lower LDL cholesterol and triglycerides while increasing high‑density lipoprotein (HDL) cholesterol (Sheneni, 2023). A randomized crossover study found that replacing meat protein with soy protein in the diet improved markers of oxidative stress and reduced serum testosterone levels, which may further contribute to cardiovascular protection (Gardner‑Thorpe et al., 2003).

Reproductive Health and Soy Consumption

Sperm Quality and Fertility

The impact of soy consumption on male fertility has been a subject of debate. Some studies suggest that high isoflavone intake may negatively affect sperm quality. For example, a study on men from an infertility clinic found an inverse association between soy food intake and sperm concentration, particularly in overweight or obese men (Chavarro et al., 2008). Another study on mice exposed to soy flour observed increased sperm abnormalities, including defects in the head, neck, and tail regions (Primiani et al., 2023).

However, other studies have found no significant association between soy consumption and sperm quality. A cross‑sectional study on urinary isoflavone levels and semen quality found no correlation between isoflavone exposure and sperm motility, morphology, or ejaculate volume (Yang et al., 2022).

Prostate Health

Soy isoflavones may have beneficial effects on prostate health. A study on human prostate smooth muscle contractions found that genistein and daidzein inhibited contractions and reduced the growth of prostate stromal cells, potentially relieving symptoms of benign prostatic hyperplasia (Huang et al., 2022). Additionally, a randomized trial on men at high risk of prostate cancer found that soy protein isolate consumption suppressed androgen receptor expression in the prostate (Hamilton‑Reeves et al., 2007).

Conclusion

The effects of soy consumption on men’s health are complex and multifaceted. While soy isoflavones may have minor suppressive effects on testosterone levels and sperm quality, the evidence in humans is not conclusive. On the other hand, soy consumption has been consistently associated with improved cardiovascular health and may offer protective effects against prostate cancer. Moderate soy intake as part of a balanced diet is unlikely to pose significant risks to men’s health, but further research is needed to fully understand its effects on reproductive function.

References

1. Abd El‑Latif, N., Elfiky, A., Moussa, S. A., & Aziz, S. (2024). Impact of Soy Protein Isolate Supplementation on Testosterone Hormone Levels and Its Biosynthesis Pathway in Male Rats. Egyptian Journal of Chemistry. DOI: 10.21608/ejchem.2024.266217.9260

2. Wang, Y., Deng, J., Gao, J., et al. (2022). Associations between isoflavone exposure and reproductive damage in adult males. Biology of Reproduction, 107, 1360–1373. DOI: 10.1093/biolre/ioac157

3. Sathyapalan, T., Rigby, A. S., Bhasin, S., et al. (2016). Effect of Soy in Men With Type 2 Diabetes Mellitus and Subclinical Hypogonadism. The Journal of Clinical Endocrinology and Metabolism, 102(2), 425–433. DOI: 10.1210/JC.2016‑2875

4. Dillingham, B. L., McVeigh, B. L., Lampe, J. W., & Duncan, A. M. (2005). Soy Protein Isolates of Varying Isoflavone Content Exert Minor Effects on Serum Reproductive Hormones in Healthy Young Men. Journal of Nutrition, 135(3), 584–591. DOI: 10.1093/JN/135.3.584

5. Nurdiana, N., Chania, M. P., Nurvitasari, R., et al. (2023). The effect of soy milk on estrogen receptor alpha expression in male Wistar rats. Nucleation and Atmospheric Aerosols. DOI: 10.1063/5.0111499

6. Zuo, X., Zhao, R., Wu, M., et al. (2023). Soy Consumption and the Risk of Type 2 Diabetes and Cardiovascular Diseases: A Systematic Review and Meta‑Analysis. Nutrients, 15(6), 1358. DOI: 10.3390/nu15061358

7. Yamagata, K. (2019). Soy Isoflavones Inhibit Endothelial Cell Dysfunction and Prevent Cardiovascular Disease. Journal of Cardiovascular Pharmacology, 74(3), 201–209. DOI: 10.1097/FJC.0000000000000708

8. Sheneni, V. D. (2023). Review of Dietary Soy’s Effects on Human Health. Journal of Clinical Medicine Research. DOI: 10.46889/jcmr.2023.4209

9. Gardner‑Thorpe, D., O’Hagen, C., Young, I., & Lewis, S. J. (2003). Dietary supplements of soya flour lower serum testosterone concentrations and improve markers of oxidative stress in men. European Journal of Clinical Nutrition, 57(1), 100–106. DOI: 10.1038/SJ.EJCN.1601495

10. Chavarro, J. E., Toth, T. L., Sadio, S. M., & Hauser, R. (2008). Soy food and isoflavone intake in relation to semen quality parameters among men from an infertility clinic. Human Reproduction, 23(11), 2584–2590. DOI: 10.1093/HUMREP/DEN243

11. Primiani, C. N., Susanto, L., & Megananda, R. C. (2023). Effect of Repeated Exposure of Soy Flour on Testicular Histology and Morphology of Mice Spermatozoa. European Journal of Biology and Biotechnology. DOI: 10.24018/ejbio.2023.4.5.493

12. Huang, R., Liu, Y., Hu, S., et al. (2022). Inhibition of α1‑Adrenergic, Non‑Adrenergic and Neurogenic Human Prostate Smooth Muscle Contraction by Genistein and Daidzein. Nutrients, 14(23), 4943. DOI: 10.3390/nu14234943

13. Hamilton‑Reeves, J. M., Rebello, S. A., Thomas, W., et al. (2007). Isoflavone‑Rich Soy Protein Isolate Suppresses Androgen Receptor Expression without Altering Estrogen Receptor‑β Expression. Journal of Nutrition, 137(7), 1769–1775. DOI: 10.1093/JN/137.7.1769