How to Safeguard Your Hormone Health & Fertility | Dr. Shanna Swan

Here are the top 10 key takeaways from Dr. Shanna Swan's conversation with Andrew Huberman about safeguarding your hormone health and fertility in our chemical-filled world.

1. Endocrine-disrupting chemicals significantly impact reproductive health

Endocrine-disrupting chemicals in our environment can significantly alter our hormones and reproductive health. Dr. Swan's research focuses on man-made chemicals that disrupt the body's hormonal systems, particularly affecting fertility and development. These chemicals interfere with natural hormone function, especially testosterone and estrogen pathways.

The effects of these chemicals are most harmful during specific developmental windows, particularly during fetal development. Early exposure can lead to lifelong changes in reproductive organs and function. Dr. Swan's research demonstrates that the timing of exposure is critical, with the most vulnerable period being early pregnancy when reproductive organs are developing.

2. Phthalates can alter male genital development and reduce fertility

Phthalates, chemicals used to make plastics soft and flexible, have been linked to what researchers call "phthalate syndrome" in males. When pregnant mothers are exposed to phthalates, their male offspring can be born with incompletely masculinized genitals. This includes shorter anogenital distance (AGD), smaller penis size, and undescended testicles.

Dr. Swan's groundbreaking research showed that men with shorter anogenital distance (a biomarker of prenatal phthalate exposure) had significantly lower sperm counts. This connection between early phthalate exposure and later reproductive capacity suggests these chemicals can have lasting effects on male fertility. Her findings have been replicated in multiple studies, confirming the relationship between phthalates and reduced male reproductive capacity.

3. Sperm counts have declined dramatically worldwide over recent decades

Global sperm counts have declined approximately 50% over the past 50 years, according to Dr. Swan's extensive research. After initially being skeptical of this claim, she conducted meticulous analyses controlling for numerous factors like counting methods, obesity, and smoking. Her systematic approach confirmed the decline was real and not due to methodological issues.

This decline is occurring worldwide and parallels the rise in chemical exposures, particularly endocrine disruptors. The drop is significant enough to affect fertility rates. Sperm counts below 45 million per milliliter significantly reduce the probability of conception, while counts above 75-100 million don't provide additional fertility benefits. With many men now falling below optimal levels, this trend represents a serious concern for global fertility.

4. Prenatal exposures create permanent changes that can't be reversed later

According to Dr. Swan, exposures during prenatal development create permanent changes that cannot be reversed in adulthood. For example, she cited a Danish study showing that if a mother smokes during pregnancy, her son will have a 50% reduction in sperm count that persists throughout his life. While changes from adult exposures (like smoking as an adult) can often be reversed, developmental changes cannot.

These prenatal effects extend beyond just the immediate offspring. Environmental exposures can affect multiple generations because the developing fetus's germ cells (future eggs or sperm) are also exposed. This means that what a pregnant woman is exposed to could potentially affect her grandchildren and possibly beyond, creating a multigenerational impact.

5. Everyday products are major sources of endocrine disruptors

Common everyday products represent significant sources of exposure to endocrine-disrupting chemicals. Food and beverages, along with their packaging and storage containers, are major routes of exposure. Plastic containers, non-stick cookware, and food wraps can leach harmful chemicals into food, especially when heated.

Fragranced products represent another significant source of exposure, particularly to phthalates. Dr. Swan advises avoiding products with added fragrances, including perfumes, scented soaps, laundry detergents, and air fresheners. Even products marketed as containing "essential oils" may contain problematic chemical mixtures. Personal care products, especially those with scents or that enhance absorption (like lotions), frequently contain endocrine disruptors.

6. Simple lifestyle changes can reduce exposure to harmful chemicals

Several practical steps can reduce exposure to endocrine-disrupting chemicals. Avoiding plastic food containers, especially when heating food, can significantly reduce exposure to phthalates and BPA. Using glass, stainless steel, or ceramic alternatives for food storage and heating is recommended. Avoiding canned foods (unless specifically labeled as BPA-free) can also reduce exposure.

Choosing fragrance-free personal care and household products can dramatically lower phthalate exposure. Buying organic produce when possible helps reduce pesticide exposure. Other helpful practices include removing shoes when entering the home to reduce tracking in contaminated dust, and using water filters or distillation systems to reduce chemical exposure through drinking water. These simple changes can collectively make a meaningful difference in reducing chemical body burden.

7. Regulatory approaches differ dramatically between Europe and the U.S.

Europe takes a much more protective approach to chemical regulation than the United States. The European REACH policy requires manufacturers to demonstrate a chemical's safety before it can enter the marketplace. This precautionary approach puts the burden of proof on companies to show their products are safe before consumers are exposed.

In contrast, the U.S. system allows chemicals to enter the market first, with testing and regulation only occurring later if problems emerge. Dr. Swan noted that it took her team 10 years and $10 million to establish the link between phthalates and reproductive harm, illustrating why the current U.S. approach is problematic given the approximately 80,000 chemicals in use. Progress in removing harmful chemicals from products in the U.S. has been slow and challenging, often requiring battles for regulation of individual chemicals.

8. Declining fertility rates pose significant demographic challenges

Birth rates are declining worldwide, creating demographic challenges with fewer young people supporting larger aging populations. Many countries have fallen below the replacement fertility rate of 2.1 children per woman, with some nations like South Korea (0.78) and Japan (around 1.0) facing particularly dramatic declines. This creates an inverted population pyramid with more elderly individuals and fewer working-age adults.

While delayed childbearing and socioeconomic factors contribute to declining birth rates, Dr. Swan's research suggests chemical exposures are also significant contributors. The pattern of declining fertility is observed not just in humans but in wildlife as well, where factors like delayed childbearing and economic choices don't apply. This suggests environmental factors are playing a substantial role in the global fertility decline.

9. Environmental exposures affect brain development and behavior

Beyond reproductive organs, endocrine-disrupting chemicals can affect brain development and behavior. Dr. Swan described research showing that boys whose mothers had higher phthalate exposure during pregnancy displayed less male-typical play behavior at age four. This suggests these chemicals may affect the sexual differentiation of the brain as well as the body.

The brain, like reproductive organs, is sexually dimorphic (having differences between males and females) and develops under the influence of hormones during specific critical periods. Disruption of normal hormone levels during these periods can permanently alter brain development. Dr. Swan also mentioned research showing certain pesticides, like atrazine, can affect sexual behavior in animals, providing further evidence that environmental chemicals can impact neurological development.

10. Western regulatory systems are not adequately protecting public health

The current regulatory approach in the United States and many Western countries fails to adequately protect public health from chemical threats. The system is reactive rather than preventative, waiting for evidence of harm before taking action. Dr. Swan noted that industry resistance makes regulatory change difficult, with even small victories like banning one chemical (DEHP) from IV bags representing major battles.

Even when harmful chemicals are banned, they're often replaced with similar compounds that may be equally problematic. For example, when BPA was recognized as harmful and companies began marketing "BPA-free" products, many substituted closely related chemicals like BPS and BPF, which appear to have similar harmful effects. This pattern of "regrettable substitution" highlights the need for more comprehensive regulation of chemical classes rather than individual compounds.