Leading reproductive expert: 12 hormones your diet is secretly controlling

Main Ideas

Hormones Affect the Whole Body

• Hormones are chemical messengers involved in metabolism, inflammation, immunity, reproduction, cognition, appetite, sleep, and more.
• They are made in many places—not only in the ovaries, testes, thyroid, and other traditional endocrine glands, but also in fat tissue and the gut.
• The speakers compare hormones to an orchestra: many systems have to work together, and problems in one area can affect others.
• Hormones are relevant to everyone. Men have estrogen, women have testosterone, and hormones are not limited to reproduction or menstrual cycles.

What Can Affect Hormone Function

The discussion highlights several influences:

• Life stage: Hormones change during puberty, the menstrual cycle, pregnancy, perimenopause, and menopause.
• Stress and circumstances: Ongoing stress and high cortisol may affect hormone systems and how people feel.
• Nutrition: Some hormones require particular nutrients to be produced. The speakers use iodine and thyroid hormones as an example.
• Health conditions and body composition: Conditions such as PCOS can affect hormone signaling, metabolism, and weight.
• Environmental exposures: Helen O’Neill discusses endocrine-disrupting chemicals in everyday products and environments as a potential influence on hormone signaling.

Fatigue, anxiety, irritability, low mood, feeling unusually cold, hair loss, and changes in weight can have many causes. The speakers caution that people may dismiss symptoms or blame themselves; persistent concerns are worth discussing with a healthcare professional.

Testing Versus “Balancing” Hormones

• The speakers distinguish between a hormone being clinically outside its appropriate range and the popular online idea of “balancing” normal hormonal fluctuations with particular foods or supplements.
• Hormones are tightly regulated through feedback systems. The discussion cautions against trying to “hack” individual hormones or suppress normal functions. For example, insulin is an important hormone, not something the body should avoid producing.
• Testing can help establish what is happening, but the appropriate test and interpretation depend on the situation and should guide any intervention.

Testosterone Treatment and Male Fertility

• Testosterone therapy can help men with confirmed low testosterone, or hypogonadism, which O’Neill says should be assessed with repeated fasting blood tests.
• Injected or external testosterone can cause the testes to reduce or stop their own testosterone production. The speakers warn that this can impair fertility, particularly for younger men.
• They caution against using testosterone without a confirmed medical need.

PCOS

• The speakers describe polycystic ovary syndrome (PCOS) as a common condition, affecting roughly one in ten women.
• It can involve elevated androgens, including testosterone; irregular or absent ovulation; and symptoms such as excess facial hair or hair loss on the head.
• PCOS can also be associated with weight-management difficulties, insulin resistance, and effects on mood and mental health. The condition is complex, and its causes are not fully understood.
• The speakers say PCOS remains under-researched and that women’s health has historically been poorly represented in medical research.

Endometriosis and Diagnosis

• Endometriosis involves endometrial-like tissue outside its usual location. It can cause severe cyclical or persistent pain and may affect other parts of the body.
• The speakers describe it as an inflammatory condition and discuss research into possible links with gut health and diet. These links are not presented as a complete explanation or cure.
• They note that diagnosis can take an average of around nine years and that severe menstrual pain is often normalized or minimized.
• Painful bowel movements are described as a strong predictor in the data discussed. The speakers say symptom and health data may help identify people who should be referred to a gynecologist sooner.
• They stress that data can indicate suspicion, but it does not establish a diagnosis on its own; clinical investigation is still needed.

The Gut’s Role in Hormone Signaling

• About 1–2% of gut cells are described as hormone-producing cells. Federica Amati focuses on gut “L cells,” which can produce hormones including GLP-1 and PYY.
• These hormones contribute to appetite and fullness signaling, gut emptying, and other digestive processes.
• Gut microbes produce compounds, including short-chain fatty acids, that help support these cells. A diet poor in foods that nourish gut microbes may impair this system.
• The speakers discuss research suggesting that high-fiber diets, especially those rich in fermentable fibers such as inulin and beta-glucan (found in foods such as oats), may improve insulin resistance in people with PCOS. They cite studies comparing this effect with metformin, while noting that diet and medication can both have a role.

Practical Dietary and Lifestyle Guidance

The recommendations discussed include:

• Eat a wide variety of plants. Amati suggests aiming for about 30 different plant foods a week as a starting point to provide a range of fibers and phytonutrients.
• Include fermentable-fiber foods, such as oats and other plant foods, to support gut microbes and gut hormone-producing cells.
• Include healthy fats, particularly omega-3 sources such as oily fish, seaweed, nuts, and seeds.
• Add fermented foods for their live microbes and fermentation products.
• Get micronutrients from food where possible. Nuts, seeds, and seafood are mentioned as sources of zinc; seafood is also discussed as a source of iodine.
• Use supplements selectively. Amati recommends prioritizing food and not supplementing without a reason or knowledge of a deficiency. The stated exception is folic acid for people trying to conceive and during early pregnancy, in line with the guidance discussed in the episode.

These approaches are presented as support for health, not as a replacement for appropriate medical care.

Fertility: Both Partners Matter

• Women are born with their supply of egg cells, which mature over time. O’Neill says nutrition and exposures across life may affect egg quality, and that the months before conception matter as eggs mature.
• Sperm develops on an approximately three-month cycle. The speakers say dietary and lifestyle changes over that period may improve sperm-health measures.
• They cite a study in which a handful of walnuts a day improved multiple sperm parameters, and recommend avoiding smoking and alcohol in the months before trying to conceive.
• The speakers emphasize that fertility and pregnancy outcomes are shared responsibilities. They discuss associations between paternal health and pregnancy or child outcomes, while cautioning against blame: many pregnancies are unplanned, and people do not need to be in perfect health for a healthy pregnancy.
• For women preparing for pregnancy, the discussion recommends a nutrient-dense diet, limiting alcohol, avoiding smoking and drugs, and understanding one’s health and fertility status.

Research and Data

• O’Neill describes research using at-home hormone testing timed to the early menstrual cycle, which helps address the challenge of studying many women at the same cycle point.
• She says her team’s data includes more than 100,000 women and can combine hormone results, health assessments, and scans to investigate reproductive conditions.
• The speakers argue that modern exposures and lifestyles mean older research may not fully reflect women’s health today. They also describe how excluding women or failing to analyze results by sex has limited medical knowledge.

Speakers and Sources Featured

• Jonathan — Host and interviewer.
• Dr. Helen O’Neill — Reproductive and molecular genetics researcher at University College London; discusses reproductive hormones, fertility, PCOS, endometriosis, and women’s-health research.
• Dr. Federica Amati — ZOE’s head nutritionist; discusses diet, gut microbes, gut hormones, and nutrition.

Other people or materials mentioned, but not featured as speakers in the main discussion: Dr. Sarah Berry and Professor Tim Spector are referenced in promotional material for other ZOE content. The guests also refer to research studies and O’Neill’s hormone and health data without naming all of the underlying studies.