BPA, Phthalates, and Testosterone: What Human Studies Show

Triggernometry host: We are going to talk about microplastics, but we wanted to start with testosterone. We hear that testosterone in men is dropping with each generation. Is that true?

Dr. Rhonda Patrick: Some evidence suggests that testosterone levels are dropping. Sperm quality and sperm counts are also reported to be dropping. A widely discussed global analysis estimated that sperm counts fell by roughly half across several decades. These are related reproductive-health concerns, but sperm count and serum testosterone are not interchangeable measurements.

Many possible factors have changed over that period. Chemical exposures have increased, and food is more processed and packaged. One study gave men a 75-gram oral glucose load and measured a temporary decrease in testosterone of about 25 percent. That was an acute laboratory response. It does not show that one sugary meal causes chronic low testosterone.

Another concern is exposure to plastic-associated endocrine-disrupting chemicals, including bisphenol A, or BPA, bisphenol S, or BPS, and phthalates. These chemicals are different from microplastic particles, although they can be associated with plastic products.

Not all plastic bottles, cans, or paper cups contain BPA or BPS. Formulations vary. Heat, wear, contact time, acidity, fat, and the specific material can affect chemical migration. One study reported a large increase in BPA migration after boiling water was placed in tested polycarbonate bottles. That result should not be generalized to every container.

BPA can interact with estrogenic and other endocrine pathways. Experimental studies also report antiandrogenic and steroidogenesis effects. The hormonal feedback system is more complex than one chemical binding one receptor and directly shutting off testosterone production.

Some human studies link BPA biomarkers with altered testosterone or sperm measures, but results are inconsistent and mostly observational. One adolescent NHANES analysis found lower testosterone in some higher BPA exposure quartiles. A separate adolescent cohort found an association in the opposite direction. These studies do not establish that BPA caused a population-wide decline in testosterone.

Triggernometry host: If testosterone declines, could that affect energy, mood, libido, health, or society more broadly?

Dr. Rhonda Patrick: Clinically low testosterone can affect libido, sexual function, bone, muscle, energy, and sometimes mood. Cardiovascular associations are more complex because illness and obesity can also lower testosterone. Political or cultural effects are outside my expertise and would be speculative.

Phthalates are used in some flexible plastics, packaging, medical products, and personal-care products. Some fragrance mixtures can contain phthalates, but not every fragranced product does. Human studies associate certain phthalate metabolites with altered testosterone in some age groups. The findings vary by chemical and study and do not prove causation.

Prenatal phthalate exposure has also been studied in relation to male reproductive development. The strongest human evidence concerns shorter anogenital distance with some metabolites. Evidence for cryptorchidism and hypospadias is less consistent and should not be described as a universal or dramatic causal effect.

Practical exposure reduction is reasonable. Avoid heating food in unsuitable plastic. Use glass or stainless steel for hot foods and drinks when practical. Choose fragrance-free personal-care products when feasible. These steps have not been proven to preserve or raise testosterone.

Low testosterone should not be diagnosed from one symptom or one blood test. Clinical guidelines require compatible symptoms and two separate low morning fasting testosterone measurements, followed by evaluation of the cause. Testosterone and over-the-counter “boosters” should not be self-started, especially when fertility matters.