The soybean is a legume that has is well-known for its use in Asian cuisine and more recently, for its touted benefits as a potent phytoestrogen. Medicinally, soy can provide the body with plant-based hormones that are proposed to have the ability to either mimic or inhibit the effects of estrogen. Men produce small quantities of estrogen in comparison to women, but produce the masculinizing hormone testosterone in far greater quantities. Soy estrogens have very controversial effects in males. A physician should be consulted before using soy estrogen as therapy.
Soy Estrogens and Prostate Cancer
Increased soy consumption is believed to lower prostate cancer mortality rates in some men. Both cultural and epidemiological studies point to this relationship, according to a 2001 "Reviews in Urology" article. Prostate cancer is considered a cancer of old age and its instigator appears to be a highly stimulating testosterone derivative, known as DHT. The estrogens in soy, namely genistein have been linked to cancer growth inhibition in vitro, by the 2001 study. When comparing American to Japanese men for prostate risks, the "Reviews in Urology" journal article correlated high soy consumption with decreased testosterone to DHT conversion, and therefore less tumor-stimulating activity. While the article strongly suggests the need for clinical studies to confirm the epidemiological and in vitro studies, it implies that soy use in men with prostate cancer may be beneficial.
Soy Estrogens and Male Fertility
Soy estrogens may impact male fertility. Sperm maturation and activity are stimulated by testosterone. Estrogens oppose testosterones, as their effects are responsible for different activities. A 2010 "Molecular and Cellular Endocrinology" journal article concluded that long-term exposure to soy estrogens and other phytoestrogens negatively affect male reproduction. Small decreases in sperm count and fertility were observed in the presence of soybean consumption from conception to adulthood in male mice.
Soy Estrogens and Male Birth Defects
Soy infant formula was noted to flood the systems of male and female babies with estrogenic compounds. These compounds may negatively influence the biological testosterone surge that occurs male babies, according to the Soy Online Service, and may alter the development of male physical and behavioral characteristics later in life. The Tulane and Xavier University Biotech Research Center, additionally notes that soy estrogen consumption by the pregnant mother increases the risk of her male child developing the genetic defect known as hypospadius.
Male infants undergo a surge of hormones, equivalent to the level associated with puberty within the first few months of life. The 2002 "Journal of Clinical Endocrinology and Metabolism" article notes that this event occurs secondary to the withdrawal of the mother's estrogen load with birth and is purposed to prepare the testis for sperm production in adulthood and frame other male characteristics. The surge wanes within the six months to year following birth and for these reasons, the Soy Online Service notes that soy consumption before 6 months of age is highly discouraged and is dispensed only through prescription in many European countries. Even in Asian countries where soy is a staple food, a 2001 "Reviews in Urology" article notes that children are not introduced to soy until they reach approximately 18 months of age.
References
- Center for Bioenvironmental Research at Tulane and Xavier University: Phytoestrogens
- Soy Online Service: Phytoestrogens & Male Health
- Molecular and Cellular Endocrinology: "Potential Detrimental Effects of a Phytoestrogen-Rich Diet on Male Fertility in Mice"
- "Journal of Clinical Endocrinology & Metabolism": "The Postnatal Gonadotropin and Sex Steroid Surge---Insights from the Androgen Insensitivity Syndrome"
- PubMed/"Reviews in Urology": "Complementary Medicine for Prostate Cancer: Effects of Soy and Fat Consumption"
