Sweating in Plastic: Understanding the Risks of Synthetic Workout Clothing

When you hit the gym or head out for a run, the last thing on your mind is likely to be the materials your workout clothes are made from. But did you know that most activewear is made from petroleum-based synthetic fabrics like polyester, nylon, and spandex? These materials, while stretchy, durable, and moisture-wicking, come with some hidden health concerns.

When you sweat, your body is not just cleansing itself—it is also exposing your skin to these synthetic fibers, potentially increasing your exposure to harmful substances, otherwise known as “forever chemicals.” Forever chemicals, known as per- and polyfluoroalkyl substances (PFAS), are synthetic chemicals used in various consumer products for their water- and grease-resistant properties. They are called "forever chemicals" because they do not break down in the environment or in the human body, leading to potential health risks such as cancer and hormone disruption. This raises the question: Should we be rethinking the plastics in our workout clothing?

In this post, we'll explore:

  • How synthetic materials in activewear affect your body during exercise.

  • Steps you can take to minimize exposure to potential risks.

  • The benefits of switching to natural fiber workout clothing.

The Problem with Plastic Activewear

Synthetic fabrics have become the gold standard for workout clothing due to their lightweight, durable, and moisture-wicking properties. However, these materials are essentially plastics, made from petroleum-based products. Here’s why that matters:

1. Sweat and Chemicals

When you sweat, your body absorbs more than just water. Many synthetic fabrics are treated with chemicals, such as dyes, stains, flame retardants, and antimicrobial agents. According to a study published in Environmental Science and Technology, chemicals from synthetic clothing can be transferred to your skin through sweat. Once on the skin, these chemicals are easily absorbed into your bloodstream, potentially disrupting bodily functions over time.

Plastic-based fabrics can also release microplastics, tiny plastic particles, onto your skin. These microplastics may clog pores, irritate your skin, or contribute to long-term health issues when absorbed.

2. Breathability Issues

Petroleum-derived fabrics often trap heat and moisture against your skin instead of allowing it to escape. This trapped environment can become a breeding ground for bacteria and skin irritation, leading to issues like body acne or fungal infections.

3. Impact on the Environment

Plastics in activewear don’t just affect you—they impact the planet too. Synthetic workout clothes shed microplastics during every wash, which eventually make their way into our oceans. These microplastics are consumed by marine life, presenting risks across ecosystems and food chains.

Statistics to Consider

  • Over 60% of clothing is made from synthetic fibers like polyester and nylon.

  • Washing synthetic fabrics releases an estimated 500,000 tons of microplastics into our oceans each year (IUCN Report).

  • Studies suggest the average person ingests 50,000 microplastic particles annually through food, drinking water, and air.

How to Minimize Your Exposure to Synthetic Materials

If completely avoiding synthetic workout wear isn’t feasible, you can still take steps to reduce your exposure to potential risks:

1. Choose Certified Non-Toxic Activewear

Look for labels that indicate sustainability and safety certifications like OEKO-TEX or GOTS (for organic materials). These certifications ensure that clothing is free from harmful chemicals and manufactured responsibly.

2. Wash Clothes Before Wearing Them

Washing brand-new clothes helps remove any lingering chemicals or residues from the manufacturing process. Use gentle, fragrance-free laundry detergents to limit adding unnecessary chemicals.

3. Always Wash with a Microfiber Filter

To reduce microplastic shedding, use a washing bag (like a Guppyfriend washing bag) or a microfiber filter for your washing machine. These tools are designed to capture microplastics before they enter waterways.

4. Opt for Layers

If you wear synthetic clothing, use a natural fiber layer (like a cotton tank top) between your skin and the synthetic material. This can help minimize direct contact with plastic-based fabrics.

5. Rinse Off After Workouts

Taking a quick shower immediately after a workout can help remove any sweat and residual chemicals from your skin, reducing the risk of absorption.

6. Gradually Transition Your Wardrobe

Replacing workout staples doesn’t have to happen overnight. Start with replacing pieces you use most often, like bras or leggings, with natural alternatives.

Natural Fiber Workout Wear Options

Switching to clothing made from natural fibers is one of the most effective ways to reduce exposure to synthetic plastics. Here’s a look at some sustainable and skin-friendly materials you can incorporate into your activewear wardrobe.

1. Organic Cotton

Soft, breathable, and hypoallergenic, organic cotton is a great choice for low to moderate-intensity workouts like yoga or pilates. Certified organic cotton avoids harmful pesticides and synthetic fertilizers, making it gentler on your skin and better for the planet.

2. Merino Wool

Though it might surprise you, Merino wool is an excellent choice for high-performance workouts. It regulates body temperature, wicks moisture away from the skin, and resists odors naturally. Plus, unlike synthetic fabrics, it is biodegradable.

3. Bamboo Fiber

Bamboo fabric is silky smooth and naturally antibacterial, making it a great option for activewear. It wicks moisture better than cotton and is often blended with other natural fibers for added stretch.

4. Hemp

Known for its durability, hemp is breathable, lightweight, and resistant to UV rays. It gets softer with every wash and is often blended with organic cotton in activewear.

5. Tencel (Lyocell)

Made from sustainably sourced wood pulp, Tencel is soft, breathable, and environmentally friendly. It’s perfect for activewear as it naturally resists bacteria and moisture build-up.

6. Blends with Natural Rubber

For stretch and flexibility, some brands blend natural fibers with natural rubber or plant-based elastane, a more sustainable alternative to petroleum-based materials.

Brands Making a Difference

  • Pact offers organic cotton activewear, focusing on ethical production.

  • Icebreaker specializes in naturally cooling Merino wool workout gear.

  • Tasc Performance blends bamboo and organic cotton for high-performance pieces.

Why It’s Worth the Switch

Making the transition away from synthetic, petroleum-based workout gear isn’t just about personal health; it’s also about contributing to a healthier environment. By opting for natural fibers, you reduce unnecessary exposure to synthetic chemicals, avoid clogging your pores with plastics, and lower the overall impact of microplastics on our planet.

This shift also represents a broader lifestyle change—towards conscious consumerism and mindfulness about what we put on (and into) our bodies.

Take the First Step Toward Clean, Comfortable Activewear

You don’t have to compromise on performance to prioritize your health and the environment. Whether it’s exchanging one piece of synthetic clothing at a time or fully committing to natural fibers, every small step counts.

Feeling overwhelmed with where to start? Explore sustainable activewear brands that align with your values or check out our curated list of natural-fiber activewear options to make your transition seamless.

Taking care of your health—and the planet—starts with the choices you make today. Your workout clothes can do more than make you look good; they can help you feel good—inside and out.

More Info:

Thread carefully: your gym clothes could be leaching toxic chemicals

12 Best Non-Toxic & Organic Sports Bras

16 Brands of Plastic-Free & Sustainable Activewear

What Microplastics Are Doing to the Brain, Body, and Reproductive System (YouTube video featuring Dr. Rhonda Patrick)

Always yours in health,

Stephenie

Nerd Out: Hypothyroidism

My latest assignment for my Master’s in Holistic Nutrition was to write a paper about a disorder of the endocrine system. I chose Hypothyroidism, as it ranks up there as one of the most prevalent chronic disorders people experience. If you’d like to nerd out with me, continue reading:

Hypothyroidism is defined as a deficiency of thyroid hormone (Pizzorno & Murray, 2013, p.1473), and is due to one of three factors: insufficient hormone synthesis, a lack of stimulation by the pituitary gland, and/or impaired conversion of thyroxine (T4) to triiodothyronine (T3) (Pizzorno & Murray, 2013, p. 1473; Rakel, 2018, p. 347). Many factors contribute to hypothyroidism, including nutrient deficiencies, environmental toxins and endocrine disruption, estrogen dominance, infections, food intolerances and food allergies, poor liver function, and chronic stress (Kohlstadt, 2012, p. 391, 398; Myers, 2019; Rakel, 2018, p. 348-350).

In primary hypothyroidism, iodine deficiency is the most common cause due to lack of dietary iodine intake in certain regions of the world, with autoimmune destruction of the thyroid gland (Hashimoto’s Disease) most common in iodine-sufficient regions (Rakel, 2018, p. 347). Other factors contributing to primary hypothyroidism include surgery to thyroid, radioactive iodine administration, certain medications, overconsumption of goitrogens, and external beam radiation (Rakel, 2018, p. 347). Low thyroid hormone levels and high thyroid-stimulating hormone (TSH) levels from the pituitary gland indicate defective thyroid hormone synthesis (Pizzorno & Murray, 2013, p. 1473). 

Secondary hypothyroidism, on the other hand, is indicated by decreased levels of both TSH and thyroid hormones (Pizzorno & Murray, 2013, p.1473). This occurs most commonly due to pituitary tumors, pituitary surgery, or disease of the pituitary gland (Rakel, 2018, p. 347). Finally, tertiary hypothyroidism is defined by a deficit of thyroid hormone-releasing hormone (THRH) from the hypothalamus (Pizzorno & Murray, 2013, p. 1473), and may be due to infection, congenital defect, or infiltrative processes of the brain (Rakel, 2018, p. 347). Subclinical hypothyroidism is indicated by elevated TSH but normal levels of T4, and may be asymptomatic, but may lead to primary hypothyroidism over time (Rakel, 2018, p. 347). 

Hypothyroidism, regardless of its etiology, affects women more than men, and whites and Mexican-Americans more than African-Americans (Kohlstadt, 2012, p. 391; Pizzorno & Murray, 2013, p. 1473). It is estimated that the rate of hypothyroidism is somewhere near 25% of the adult population, with incidences significantly higher among the elderly (Pizzorno & Murray, 2013, p. 1473).

Symptoms of hypothyroidism can mimic other diseases making it challenging to identify and diagnose (Kohlstadt, 2012, p. 392). Mild fatigue or depression may go on for years and precede any clinical serum abnormalities, therefore a careful analysis of both symptoms and lab test results are crucial to diagnosis (Kohlstadt, 2012, p. 393; Pizzorno & Murray, 2013, p. 1474). Chronic fatigue, depression, malaise, difficulty concentrating, forgetfulness, weight gain, sensitivity to cold (especially in the hands and feet), edema, decreased libido, menstrual abnormalities, infertility, dry skin, hair loss, thinning eyebrows, thin, brittle nails, muscle weakness, joint stiffness, gastroesophageal reflux disease (GERD), shortness of breath, constipation, delayed tendon reflex, loss of hearing, and atherosclerosis are all possible presentations in hypothyroidism (Kohlstadt, 2012, p. 393; Pizzorno & Murray, 2013, p. 1474; Rakel, 2018, p. 348).  

Allopathic approaches to treatment of hypothyroidism rely primarily on serum lab testing of TSH and sometimes T4 (Mayo Clinic, 2018). Traditionally the accepted as normal range for TSH is quite broad, measuring 0.35-5.50 mIU/mL, with some conventional practitioners using levels greater than 10 mIU/mL as a basis for recommending treatment (National Academy of Hypothyroidism, 2012; Pizzorno & Murray, 2013, p. 1476). Additional labs such as cholesterol and triglyceride measures as well as clinical presentation of the patient may also be taken into account. If lab results indicate low TSH, a pharmaceutical is prescribed, most often the synthetic T4 thyroxin (levothyroxine sodium), with the most common brand names of Levoxyl (levothyroxine) and Synthroid (Lee & Hopkins, n.d.; National Academy of Hypothyroidism, 2017). It is interesting to note that thyroid hormone-replacement drugs are ranked the third most common prescribed in the United States (National Academy of Hypothyroidism, 2017). Rarely are nutrition, lifestyle, gut integrity, and stress addressed in allopathic care of hypothyroidism, with the focus almost solely on pharmaceutical intervention (National Academy of Hypothyroidism, 2012). Typically, once stabilized within normal range, TSH levels are monitored yearly and dosages adjusted as needed (Mayo Clinic, 2018). 

Integrative approaches to healing hypothyroidism are more holistic in approach, taking into account not only lab tests of thyroid hormones but also nutrition, stress levels, lifestyle choices, sex hormone levels and blood sugar regulation. A comprehensive evaluation, including labs, medical history, symptomatology, and lifestyle choices recognize that hypothyroidism is a multi-faceted disorder with often more than one overt cause (Kohlstadt, 2018, p.392). 

Comprehensive thyroid labs test not only for TSH, but for T4, free T4, T3, free T3, and reverse T3 (rT3) (Pizzorno & Murray, 2013, p. 1474; Rakel, 2018, p. 348). Cholesterol, triglyceride, cortisol, homocysteine, and C-reactive protein (CRP) levels may also be tested, and if elevated, indicate possible hypothyroidism (Pizzorno & Murray, 2013, p. 1474). Low iron and B12 are also indicators of thyroid insufficiency (Pizzorno & Murray, 2013, p. 1474). Supplementation is recommended based on lab results, with brand name Armour Thyroid most commonly prescribed in functional medicine. Combination via dessicated pig or cow thyroid (also called USP thyroid) provides both T3 and T4 support in approximately the ratio made by the human thyroid (Lee & Hopkins, n.d.; National Academy of Hypothyroidism, 2017) as opposed to only TSH replacement. In addition to labs and to further support a hypothyroid diagnosis, a Basal Body Temperature test may be done to measure for lowered body temperature, while the Iodine patch test demonstrates iodine uptake and therefore the body’s need for iodine (Weatherby & Ferguson, 2005, p. 17-23). 

Environmental toxins play a role in thyroid health. Heavy metals compete for thyroid hormone, iodine, and selenium uptake in the thyroid, so testing for mercury, lead, and cadmium by way of urine provocation test would be indicated (Kresser, 2019; Pizzzorno & Murray, 2013, p. 194-195). The halides, including fluoride, bromide, and chloride bind with iodine receptors in the thyroid gland (Fluoride, Bromide, Chloride, and Thyroid Health, 2018). A 24-hour urine iodine test may be ordered to check for possible iodine deficiency and levels of halides (Fluoride, Bromide, Chloride, and Thyroid Health, 2018; Kohlstadt, 2012, p.396). Measures to decrease exposure to these chemicals are encouraged.

Gut dysbiosis and increased intestinal permeability both interfere with iodine, selenium, and other mineral absorption (Kohlstadt, 2012, p. 394). A Comprehensive Digestive Stool Analysis for dysbiosis, Organix test to measure protein digestion, and a lactulose-mannitol test to measure intestinal permeability may all be utilized (Rakel, 2018, p. 580). Selenium- , zinc-, and iodine-rich foods and/or supplementation may be recommended to ensure proper uptake (Kresser, 2019).

Lifestyle, and particularly stress plays an enormous role in thyroid health, as excess cortisol inhibits thyroid hormone metabolism (Kohlstadt, 2012, p. 401; National Academy of Hypothyroidism, 2017). An adrenal stress profile using salivary collection will provide clues to cortisol levels (Kohlstadt, 2012, p. 401). Meditation, low-intensity exercise, breathwork, and body work may all be recommended to support thyroid health, even if cortisol levels are within normal range (Rakel, 2018, p. 358-359). Blood glucose levels may be checked and measures taken to balance insulin levels and reduce inflammation through diet and exercise (Wentz, 2019).  Encouraging proper sleep hygiene and maintaining a healthy body weight are regarded as positive practice as well (Rakel, 2018, p. 590). 

Estrogen dominance and/or progesterone deficiency also play a big role in hypothyroidism. An imbalance of these female sex hormones not only produce symptoms mimicking hypothyroidism, but increase serum thyroid binding globulin (TBG), rendering thyroid hormones inactive (Myers, 2019). A 6- or 24-hour saliva or urine collection to measure estrogen levels may be ordered to determine a course of action.  Balancing estrogen-dominance calls for a multi-faceted approach, including decreasing stress and inflammation, minimizing exposure to xenoestrogens and hormone disruptors, reducing exposure to heavy metals, and eating organic and minimally-processed whole foods (Myers, 2019; National Academy of Hypothyroidism, 2017).  

Nutrient-rich foods are encouraged to support optimal thyroid health, regardless of lab results. Iodine-rich foods such as sea vegetables, ocean fish, and unrefined sea salt support iodine levels (Fluoride, Bromide, Chloride, and Thyroid Health, 2018; Kohlstadt, 2012, p. 394). Cooking raw goitrogens (cruciferous or Brassica vegetables, including cabbage, turnips, Brussels sprouts, broccoli, cauliflower, bok choy, etc.) before consuming or avoiding altogether is recommended (Kohlstadt, 2012, p. 394-395), as goitrogens compete for iodine uptake and block incorporation into the thyroglobulin molecule (Kohlstadt, 2012, p. 394-395. Minimizing the effect of thyroid peroxidase enzyme-inhibiting (TPO-inhibiting) soy isoflavones by consuming fermented soy is encouraged (Kohlstadt, 2012, p. 395). Increasing intake of zinc-rich foods (seafood, oysters, red meats, and organ meats), heme iron (chicken liver, oysters, beef liver, beef, turkey, and chicken), selenium (Brazil nuts, grass-fed meat, eggs, ans seafood), and copper (organ meats, eggs, yeast, beans, nuts, and seeds) are also extremely supportive to the thyroid (Kohlstadt, 2012, p. 393-398). Finally, daily exposure to sunshine or vitamin D supplementation, and vitamin A, C, E, copper, the B vitamins, and trace mineral supplementation may also be indicated to optimize thyroid hormone production and uptake (Pizzorno & Murray, 2013, p. 1479). 

Regardless of etiology, hypothyroidism can be managed through lab testing and hormone supplementation. A holistic approach provides additional support with nutritional supplementation, a nutrient-dense diet, exercise, and lifestyle modifications. 




   

References

Fluoride, Bromide, Chloride and Thyroid Health. (2018, January 2). Retrieved November 26, 2019, from https://www.naturalendocrinesolutions.com/articles/fluoride-bromide-chloride-and-thyroid-health/.

Kohlstadt, I. (2012). Advancing Medicine with Food and Nutrients, Second Edition. Hoboken: Taylor and Francis.

Kresser, C. (2019, October 10). How Environmental Toxins Harm the Thyroid. Retrieved November 25, 2019, from https://kresserinstitute.com/environmental-toxins-harm-thyroid/.

Lee, J. R., & Hopkins, V. (n.d.). What Your Dr May Not Tell You About Your Thyroid. Retrieved November 24, 2019, from https://www.virginiahopkinstestkits.com/thyroidarticle.html.

Myers, A. (2019, November 14). 9 Causes of Estrogen Dominance and What to Do About It. Retrieved November 24, 2019, from https://www.amymyersmd.com/2019/03/9-causes-estrogen-dominance/.

Mayo Clinic. (2018, December 4). Hypothyroidism (underactive thyroid). Retrieved November 24, 2019, from https://www.mayoclinic.org/diseases-conditions/hypothyroidism/diagnosis-treatment/drc-20350289.

National Academy of Hypothyroidism. (2012, January 27). Why Doesn't My Endocrinologist Know All of This? Retrieved November 24, 2019, from https://www.nahypothyroidism.org/why-doesnt-my-doctor-know-all-of-this/.

National Academy of Hypothyroidism. (2017, September 13). Estrogen Dominance and Hypothyroidism: National Academy of Hypo. Retrieved November 24, 2019, from https://www.nahypothyroidism.org/estrogen-dominance-and-hypothyroidism-is-it-hypothyroidism-or-hormone-imbalance/.

Pizzorno, J. E. (2013). Textbook of natural medicine. St. Louis, MO: Elsevier/Saunders.

Rakel, D. (2018). Integrative medicine. Philadelphia, PA: Elsevier.

Weatherby, D., & Ferguson, S. (2005). The complete practitioners guide to take-home testing: tools for gathering more valuable patient data. Ashland, OR.: Emperors Group.

Wentz, I. (2019, March 14). Why Balancing Blood Sugar is Vital for Hashimotos Help. Retrieved November 26, 2019, from https://thyroidpharmacist.com/articles/blood-sugar-imbalances-and-hashimotos/