by Matt Weik, BS, CSCS, CPT, CSN
Soy has been a hot topic for years. Some claim it messes with hormones, while others say it’s packed with health benefits. But what does the science actually say about soy raising estrogen?
I know one thing is for sure: gym rats and bodybuilders have been steering clear of anything soy for many years now. In fact, we have been avoiding it like the plague in fear of increasing estrogen levels.
A new study, partially funded by the United Soybean Board, suggests that soy doesn’t act like estrogen in the body. Instead, its bioactive compounds have tissue-specific effects.
I guess that’s good news, right?
Researchers from Canada and the U.S. published their findings in Advances in Nutrition, stating that soy isoflavones likely function as selective estrogen receptor modulators (SERMs). That means they don’t mimic estrogen in a general way — they behave differently depending on where they act in the body.
In this article, let’s dive deeper into these findings and get a better understanding of whether or not we should worry about soy raising estrogen levels.
Disclaimer: This article is for informational purposes only and is not meant to treat or diagnose any condition. It is recommended that you speak with your doctor before starting any exercise program, making changes to your nutrition plan, or adding any new supplements into your current regimen.
The Soy and Estrogen Controversy: Myth vs. Reality
Soy contains high levels of isoflavones, which are polyphenolic compounds found in legumes. Because isoflavones have been shown to have estrogen-like effects, they’ve been labeled as phytoestrogens.
Hence, why we’ve been so worried about consuming any and all products that contain soy.
For years, there’s been concern about soy’s impact on hormone-dependent cancers, thyroid function, and cognitive health. However, much of the evidence comes from animal studies.
The problem?
Rodents metabolize soy differently than humans. That means those studies don’t necessarily translate to real-world effects on people. We’d need actual studies with humans to make the final determination.
Are There Health Benefits of Soy?
Human trials have shown that soy may actually offer health benefits. Research suggests it may help with:
- Cardiovascular disease (CVD) prevention
- Certain cancers
- Bone health
- Menopause symptom relief
One key finding in the study supports earlier research from 2016. That review found no significant change in endometrial thickness (ET) in peri- and postmenopausal women using soy isoflavones.
Interestingly, higher doses of isoflavones may actually reduce ET. This could potentially lower the risk of endometrial cancer — something backed by some epidemiological data.
Since SERMs have tissue-specific effects, soy’s benefits on bones, memory, cancer risk, and menopausal symptoms remain promising.
Researchers emphasized that isoflavones do not act like hormone replacement therapy (HRT), and concerns about them being too similar to estrogen are largely unfounded.
What Does This Mean for Your Diet?
Most of the clinical trials in the study used isoflavones in supplement form. However, eating whole soy foods may offer additional benefits, thanks to the other biologically active compounds present.
It’s also worth noting that some soy-based processed foods (like soy protein isolates) can lose up to 90% of their isoflavone content during processing. If you’re looking for benefits, whole soy foods or purified isoflavone supplements might be the way to go.
Soy also has another advantage: it’s an eco-friendly protein source for those on a plant-based diet. With its low environmental impact and affordability, researchers suggest that incorporating more soy into the diet could align with public health goals.
Soy Study Breakdown: What the Research Found
The study was a systematic review and meta-analysis that examined 40 trials, covering 52 comparisons. In total, 3,285 middle-aged, postmenopausal women participated.
Researchers focused on four key measures of estrogenicity:
- Endometrial thickness (ET)
- Vaginal maturation index (VMI)
- Follicle-stimulating hormone (FSH)
- Estradiol levels
These markers were chosen because they are directly influenced by estrogen and were commonly evaluated in studies on soy isoflavones.
Participants took a median dose of 75 mg of soy isoflavones daily over 13 to 24 weeks.
The results?
Soy isoflavones had no statistically significant effect on any of the estrogenicity markers.
That’s actually quite interesting, no? And here we have been avoiding anything with soy like the plague.
The certainty of this evidence was rated high to moderate, meaning the conclusions are pretty solid.
So… Should You Shy Away from Soy in Fear of Higher Estrogen?
The question everyone is asking is, does soy actually mess with your hormones? Based on the latest research, the answer is no.
While it contains isoflavones, they don’t act like estrogen in a general sense. Instead, they function as selective estrogen receptor modulators, meaning their effects depend on the specific tissue they interact with.
For those looking to improve heart health, bone strength, and menopausal symptoms, soy may actually be a helpful addition to your diet. Just make sure you’re getting it from whole foods or high-quality supplements.
