Is Your Underwear Destroying Your Hormones? The Scary Truth About Polyester

By: Marc Lobliner, IFBB Pro

Polyester might be one of the most common fabrics in your wardrobe, but when it comes to what you wear underneath—it could be doing more harm than you think.

Polyester Is Plastic—And It’s Rubbing Against Your Skin

Polyester is a synthetic polymer made from polyethylene terephthalate (PET), the same petroleum-based material used in plastic water bottles. While it’s cheap, durable, and moisture-wicking, its synthetic nature comes at a biological cost—especially when it comes into direct contact with your skin.

When polyester underwear is exposed to body heat and friction (think sweating, working out, or sitting in a sauna), it begins to shed microplastics. These microscopic particles can penetrate the skin or be absorbed through sweat glands, potentially entering systemic circulation.

Microplastics and Reproductive Health: The Science Is Alarming

A 2023 study published in Toxicological Sciences found that microplastic exposure in mice significantly disrupted their endocrine systems and decreased sperm quality. While more human studies are needed, early research suggests similar risks.

Meanwhile, research published in Environmental Health Perspectives observed that men with higher phthalate (a plasticizer) levels had lower testosterone levels and reduced fertility. Phthalates are commonly found in synthetic clothing and personal care products.

Perhaps most alarming, microplastics have now been found in human blood, semen, and placental tissue—suggesting widespread systemic exposure. A 2022 study led by Jenner et al. and published in Environment International confirmed these particles can circulate within the human body and potentially cross biological barriers.

Heat + Plastic = More Microplastic Shedding

When you wear tight-fitting polyester underwear, you’re creating the perfect storm for microplastic release. Friction, heat, and moisture accelerate the breakdown of fibers, and all of it happens in close contact with your most sensitive body parts.

Wearing plastic directly against hormone-rich and absorbent regions of the body increases the chance of microplastic exposure where you absolutely don’t want it.

The Safer Swap: Organic Cotton Underwear

Organic cotton is breathable, biodegradable, and free of synthetic chemicals or heat-reactive plastics. It doesn’t leach phthalates or shed microplastics.

Choosing organic cotton underwear is:

• Safer for your skin and reproductive health

• Free from endocrine-disrupting compounds

• Better for the environment

• Durable when cared for properly

Even Your Laundry Matters

It's not just wearing synthetic fabrics—washing them is a problem too. One study from Philosophical Transactions of the Royal Society B (Browne et al., 2011) found that a single load of polyester laundry can release over 700,000 microfibers into the water system.

These fibers escape filtration, enter oceans, get ingested by marine life, and eventually come back into our food supply. It’s a full-circle environmental and health hazard.

Final Thoughts

If you care about your hormones, reproductive health, performance—or just don’t want plastic grinding against your groin all day—it’s time to ditch the polyester underwear.

Choose organic cotton. Protect your health, your hormones, and your future.

NOTE: I have a coupon code, "LOBLINER" at NADSUNDER.COM. This is the brand that I use.

Sources:

• Browne, M. A., et al. (2011). Accumulation of microplastic on shorelines worldwide: sources and sinks. Philosophical Transactions of the Royal Society B.

• Jenner, L. C., et al. (2022). Detection of microplastics in human blood. Environment International.

• Toxicological Sciences, 2023: Endocrine disruption and sperm impairment in mice exposed to microplastics.

• Environmental Health Perspectives: Associations between urinary phthalate metabolites and testosterone levels in men.