All That Bad Stuff You Heard About Soy and Phytoestrogens Among Adults... Yeah, About That

Dr Shawn M. Carney
6 days ago
8 min read

This blog is being published during Breast Cancer Awareness Month. So let's take this opportunity to review a topic from nutrition that has had a '180 degree turn' in recent years. Long maligned as an endocrine system disruptor, soy and some of its specific derivatives have increasingly been shown to have health benefits, when used among adults. Let's shed some light on how this popular bean can help your hormones, your immune system, your bones, and you!

When it comes to plant-based estrogen sources, or 'phytoestrogens', soy:

is a primary source of estrogens called "isoflavones"
has the largest amount of volume ingested by people
as well as most amount of research with regard to health.

So for the purpose of this article, soy isoflavones, which include daidzein and genistein, will be the focus of our attention with regard to phytoestrogens.

On the Topic of Estrogens, Nutritional Supplements and Prescriptions

Our bodies contain different forms of estrogens, of which 'estradiol' is a key player. A common ingredient in estrogenic hormonal support medications and supplements is 'micronized estradiol USP'. When comparing USP-grade estradiol to synthetic or natural versions, it's important to clarify terminology. "Estradiol, USP" is a standardized, bioidentical hormone, but it is chemically manufactured rather than directly extracted from a natural source. The designation "USP" (United States Pharmacopeia) means the ingredient meets strict, laboratory-tested standards for purity, potency, and consistency. It is not a reference to its origin. The final product, "estradiol, USP", is bioidentical to the natural hormone produced by the human body.

For commercial production, the raw ingredients often come from plant compounds, such as those found in wild yams or soy. Hence the connection with phytoestrogens. However, a chemical process is required to convert the plant substance (like diosgenin) into human-identical estradiol. After synthesis, purification, and standardization, the resulting USP-grade estradiol has the exact same molecular structure as the estradiol found in the body. The USP standard ensures that a product is high-quality and consistent from batch to batch, which is a key requirement for prescription medications.

The "Natural" Versus "Synthetic" Debate

The distinction between "natural" and "synthetic" hormones can be misleading. "Natural" in this context refers to the plant-derived origins of the precursor materials. However, a series of chemical reactions is needed to transform these materials into human estradiol. The final product is not "natural" in the sense of being taken directly from a plant, but it is "bioidentical".

The term "synthetic" can refer to chemically manufactured compounds that have a slightly different chemical structure than the body's natural hormones. These structural differences cause them to be metabolized differently. Ethinylestradiol, for example, is a synthetic estrogen often used in oral contraceptives. Estradiol, USP, is both chemically synthesized and structurally identical (bioidentical) to the body's natural estradiol. For this reason, calling it simply "synthetic" or "natural" can cause confusion. (1) Some synthetic estrogens are intentionally formulated to be different from human estradiol for specific applications, such as hormonal birth control. For example, unlike estradiol, ethinylestradiol (EE) is designed to be highly bioavailable when taken orally, resisting the rapid metabolism that affects oral estradiol. Another example is conjugated equine estrogens (CEE), which is found in the drug Premarin; these are a mix of estrogens derived from pregnant horse urine. They are not bioidentical to human hormones and are distinct from estradiol, USP.

And on the topic of safety, the source and production method can influence a hormone's performance, but the route of administration also plays a crucial role. Bioidentical estradiol studies show that when delivered via the skin (transdermally), it may have a lower risk of blood clots and stroke than oral synthetic estrogen because it bypasses the liver . (1) By contrast, synthetic forms (e.g., ethinylestradiol, Premarin) have been shown to have different metabolic effects and different side effect profiles, including a higher risk of certain cardiovascular problems, particularly with oral formulations (2).

Estrogen: No Longer Typecast to Shoulder All the Blame

There have been decades of controversy around the safety of soy consumption, particularly among infants, children and adolescents with regard to proper endocrine and reproductive organ development (3), (4). Though many of these conclusions found their origins among research on rodents, given significantly higher doses than what would comparatively be taken in by humans, there have also been concerns about the above mentioned phytochemicals isoflavones. Isoflavones in soy can act like estrogen in some ways within the body, and increased estrogen has been linked to certain types of breast cancer (3).

However, research from earlier this year expanded on a growing body of evidence that estrogen is increasingly not being seen as the driver to breast cancer as much as progesterone (4).

'Yet emerging clinical and experimental evidence points to progestogens [endogenous

progesterone or synthetic progesterone (progestin)] as the primary hormonal driver underlying

seemingly estrogen-associated breast cancer risk. Estrogens may contribute to breast cancer

risk indirectly by induction of the progesterone receptor and thus amplifying progesterone

signaling. Large studies of hormonal contraceptives suggest that the small increase in breast

cancer risk from hormonal contraceptives is mainly attributable to progestins, not estrogens.

Estrogen-plus-progestin hormone replacement therapy (HRT) has consistently shown an

increase in breast cancer risk among postmenopausal women, whereas estrogen-alone HRT has

little impact on breast cancer risk in naturally or surgically menopausal women' (5).

Soy Isoflavones and Phytoestrogens are NOT the Same as Estrogen

If soy isoflavones are like a fishing line, estrogens are like a drift net - catching and triggering many more things, in a more profound way, resulting in more problematic results.

Phytoestrogens are non-nutrient bioactive compounds and are ubiquitous to the plant kingdom, possessing a wide range of biological properties that contribute to the many different health-related benefits reported for soy foods and flaxseeds--two of the most abundant dietary sources of phytoestrogens. Isoflavones are such compounds, found in high concentrations in soy foods, and thus "soy isoflavones" have been the object of significant research. Arguments have been made for considering soy isoflavones as 'natural selective estrogen receptor modulators' (SERMs) based upon decades of data of their conformational binding to estrogen receptors (6, 7). But they are 'selective' and more targeted, as well as less provocative to the receptors they signal within the human body, compared with estrogen itself.

Thus comprehensive research published last year concluded: "Current evidence suggests that soy isoflavones do not exhibit estrogenic effects compared with non-isoflavone controls on 4 measures of estrogenicity in postmenopausal women. This synthesis supports that soy isoflavones likely act as selective estrogen receptor modulators, differing clinically from the hormone estrogen" (8).

Soy and Phytoestrogen Benefits for Your Immune System

A large body of evidence supports the safety of soy foods as part of a healthy diet for adults. Multiple research studies have found consuming soy foods is associated with a decreased risk, or at least no change in risk, for cancers. "Some of the confusion around the safety of soy foods has been due to some earlier study findings in mice and rats compared to humans, ... [h]owever, mice and rats break down and process isoflavones differently than humans. Also, the doses used in animal studies are much higher than in studies conducted on people" (9).

Soy and Phytoestrogen Benefits for Your Bones

Phytoestrogens, most notably derived from soy and red clover, have been shown in several studies to not just alleviate menopausal symptoms, but even improve bone health and reduce the risk of fractures (10).

Currently, initial treatments for osteoporosis in postmenopausal women include antiresorptive agents such as bisphosphonates, strontium ranelate, estrogen replacement therapy (ERT) and synthetic SERMs; however, these do not rebuild bone, be it from outright mechanisms of action or the 'over-suppression' of mending micro-fractures. These characteristics limit their effectiveness.

By contrast, the estrogenic effects on bone could contribute to the preservation of bone mineral density (11).

A Note on Phytoprogestins

The most commonly prescribed progestogens are progestins, which are synthetic compounds such as medroxyprogesterone acetate. Natural progesterone, termed progesterone USP, is synthesized from plant sources. In contrast to progestins, progesterone USP is structurally identical to endogenously produced progesterone. A number of Food and Drug Administration (FDA)-approved forms of natural progesterone are available and include micronized oral capsules, vaginal gel, topical progesterone gel, and intramuscular preparations. Natural progesterone cream (progesterone USP) products can be purchased over the counter (and over the Internet) in the United States as well as other countries. Progesterone cream is categorized as an herbal beauty product and as such is not regulated by the Food and Drug Administration (FDA).

'Phytoprogestins' are plant-based chemical compounds of natural origin, which have progestagenic effects. While phytoestrogen-based therapies have been extensively studied, not so for phytoprogestins. Their potential remains largely untapped, especially given some of the concerns around progesterone-based HRT as outlined above. This is undoubtedly an area from which there is more to come.

In conclusion, the benefits of soy among adults and its safety have been increasingly established. Even among children, the peer-reviewed reference abounding NatMed database finds soy as "likely safe" for children "... when consumed in amounts commonly found in foods or as a component of infant formula. Soy milk that's not designed for infants should not be used as a substitute for infant formula. ... Most evidence shows that exposure to soy formula or other soy products in infancy does not cause early onset of puberty or health or reproductive problems later in life" (12).

References:

The content and any recommendations in this article are for informational purposes only. They are not intended to replace the advice of the reader's own licensed healthcare professional or physician and are not intended to be taken as direct diagnostic or treatment directives. Any treatments described in this article may have known and unknown side effects and/or health hazards. Each reader is solely responsible for his or her own healthcare choices and decisions. The author advises the reader to discuss these ideas with a licensed naturopathic physician.