What’s causing our declining fertility?

Fertility is one of the clearest indicators of overall health. When a species can't reproduce properly, something has gone fundamentally wrong.

And that’s where we are right now.

The numbers don't lie

Infertility now affects roughly 1 in 6 people globally—nearly double the estimates from just a decade ago.

The trend isn't slowing down, either—a 2025 study analysing 204 countries found that infertility prevalence has been rising by roughly 0.5–0.7% per year since 1990, and is projected to continue climbing.

In men, sperm counts have declined by roughly 50% over the past five decades. Testosterone levels have been declining across generations — independent of age and obesity — a pattern now confirmed across multiple countries and is not showing any signs of reversing. In women, conditions like PCOS — which now affects an estimated 66 million women globally — are another growing reproductive concern.

Even when conception succeeds, the road is far from smooth. An estimated 23 million miscarriages occur every year globally— that’s 44 pregnancy losses every minute, roughly 15% of all pregnancies. One in ten women will experience at least one miscarriage. The Lancet's landmark series on miscarriage identified alcohol, air pollution, pesticide exposure, stress, and night-shift work among the confirmed risk factors—all hallmarks of modern life.

Caesarean sections now account for over 20% of births globally. C-sections are usually considered routine, but babies born this way miss out on colonisation by the mother's vaginal microbiome—a process that appears critical for setting up the newborn's immune system—and the long-term consequences, including links to immunological diseases, are only now being understood.

The IVF industry tells the story

If fertility was improving, the IVF industry would be shrinking.

It's not.

In the United States, over 100,000 IVF babies were born in 2024—1 in every 36 births. The global IVF market is now valued at roughly $26 billion, projected to nearly triple by 2034.

That's not a sign of progress. That's an industry built on the back of a population that is losing its most basic biological function.

IVF is also not particularly effective. Success rates vary dramatically — under 35 years, roughly 1 in 3 cycles results in a live birth. It is expensive, physically demanding, and emotionally draining.. And it does nothing to address why people are struggling to conceive in the first place.

We're spending billions to work around a problem we should be trying to prevent.

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What's driving the decline

It's not one thing. It's a convergence of modern inputs that our physiology was never designed to handle.

We stopped eating the nutrients our reproductive hormones are made from

Cholesterol is the sole precursor to every steroid hormone in the body—pregnenolone, testosterone, progesterone, Vitamin D, estrogen, cortisol, all of them. The biosynthetic pathway runs: cholesterol → pregnenolone → progesterone (and from there to the rest of the steroid family).

Progesterone — the true fertility hormone, which derives its name from 'pro-gestational' — orchestrates the entire reproductive process. It triggers ovulation, prepares the uterus for implantation, sustains the placenta, and supports the development of the baby's brain, nervous system, and organs.

Beyond reproduction, progesterone is the body's most protective hormone — anti-inflammatory, anti-stress, and essential for energy production at the cellular level. Without adequate cholesterol, the body cannot make enough of it.

For decades, mainstream dietary advice has demonised cholesterol and saturated fat—the very nutrients required to build reproductive hormones. Low-fat diets are associated with reduced testosterone in men. The consequences for women's reproductive hormones—particularly progesterone—follow the same biochemical logic. We've been told to remove the building blocks of fertility from our diets, and then we act all surprised when fertility declines.

We are running cold (slow metabolism)

Here is another fact that doesn't get enough attention: human body temperature has been declining for over 150 years.

Body temperature is a reliable indicator of metabolic rate. A declining population-wide temperature suggests a declining population-wide metabolism. And metabolism governs everything—energy production, hormone synthesis, immune function, and yes, fertility. A body that can't produce adequate heat is a body that is under-producing energy at the cellular level.

This aligns with what is seen clinically—cold hands and feet, sluggish thyroid function, excess body fat, difficulty conceiving—are all symptoms of a suppressed metabolic rate. The modern cocktail of seed oils, nutrient deficiencies, chronic stress, and endocrine-disrupting chemicals is slowing us down from the inside.

We're being poisoned—slowly and systemically

The modern environment is loaded with compounds that our physiology never encountered until very recently.

Environmental pollutants are now consistently linked to declining sperm quality.

Plastics contain xenoestrogens that disrupt sex hormone balance. Non-stick cookware leaches PFAS — 'forever chemicals' — into our food. Estrogenic mycotoxins, produced by common food-borne moulds, contaminate many packaged foods.

We are exposed to thousands of synthetic compounds that didn't exist a century ago, and we have very little understanding of how they interact inside the human body.

But it's not just the chemicals around us—it's the ones we're eating. Over the past fifty years, the composition of human body fat has fundamentally changed. Linoleic acid—an omega-6 fatty acid found in industrial seed oils—has increased by 136% in human adipose tissue, directly correlated with the rise of soybean, canola, and sunflower oil in the food supply. We are literally made of different fat than our great-grandparents were.

These fats oxidise easily, producing toxic compounds that drive chronic inflammation — partly by fuelling the production of prostaglandins. They also suppress the metabolic rate. Our ancestral omega-6 to omega-3 ratio was roughly 1:1, but in modern Western diets it's closer to 20:1. A body that is inflamed and metabolically suppressed does not prioritise reproduction.

Our lifestyles do not support our basic physiological needs

We avoid sunlight — even though UVB exposure activates a direct hormonal pathway from the skin to the brain to the gonads, increasing sex hormone levels and reproductive drive.

We spend our evenings bathed in blue light from screens, disrupting the circadian rhythms that govern the release of reproductive hormones.

We wear synthetic plastic fabrics against our skin — which have been shown to impair spermatogenesis.

Too much of some things. Not enough of others. The result is a species slowly losing its ability to do the one thing it absolutely must.

What to do about it

The good news is that most of these variables are within your control.

Eat a diet rich in animal foods. Saturated fat, cholesterol, fat-soluble vitamins (A, D, E, K), minerals like calcium, zinc, potassium and magnesium—these are the nutrients that traditional cultures prioritised for parents-to-be. They're found in their most bioavailable forms in animal foods: red meat, organ meats, eggs, butter, raw dairy, bone broth. These are basic materials your body needs to produce reproductive hormones, maintain metabolic rate, and build healthy cells.

Eliminate seed / vegetable oils. Soybean, canola, sunflower, safflower, cottonseed, grapeseed—get them out of your kitchen and read every ingredient label. They are in virtually everything in the modern food supply.

Support your metabolism. Eat enough. Eat regularly. Don’t eat zero carbs. Make sure you’re getting sufficient protein. Don't chronically under-eat or over-exercise—both suppress thyroid function and metabolic rate. Prioritise nutrient-dense calories over restriction. If your hands and feet are cold, if your morning body temperature is consistently below 36.5°C, your metabolism is likely suppressed—and your fertility will reflect that.

Eliminate the synthetic toxins. Ditch the plastic food containers, the non-stick cookware, the synthetic-fabric underwear, air fresheners, scented candles and overpriced perfumes. Choose natural fibres—cotton, wool, bamboo. Filter your water. If an ingredient label reads like a chemistry experiment, it's a red flag.

Get outside. Daily sunlight and barefoot walks aren't wellness trends—they're biological expectations your body has had for millions of years.

Move your body. Move around often and at a slow pace. Practice challenging, whole-body, functional movement patterns. Lift heavy things. Sprint if you can. And remember to play.

Protect your sleep. Screens off after sundown. Swap your LEDs for incandescents. Think mood lighting. Try to keep a consistent schedule. Your circadian rhythm governs your hormone production—mess with it, and everything downstream suffers.

Protect your emotional and psychological wellbeing. Avoid checking your phone 150 times per day. Prioritise the people and relationships that have a positive impact on your life. Forget about being ‘informed’ by newspapers and news programs — they’re in the entertainment business, not the truth business.

It’s not fancy, but it works. The benefits compound over time.

Health is generational—and that's the real concern

This isn't just about you getting pregnant. It's about what you pass on.

Many traditional cultures understood that the health of parents directly shapes the health of their children. Mothers and fathers-to-be were put on special dietary regimes before conception—designed to stockpile essential nutrients, optimise the health of both parents, and ensure a surplus of nutrition throughout pregnancy.

The field of epigenetics is revealing that environmental factors—particularly nutrition—impact gene expression across generations. Many conditions we label as 'genetic' may simply result from missing critical developmental inputs or exposure to environmental toxins at key developmental windows.

The fertility crisis isn't just about declining conception rates today. It's about the compounding consequences for future generations. Each generation that conceives in a state of stress, nutritional deficiency, and metabolic suppression, passes those disadvantages forward.

The bottom line

Our most fundamental biological function is failing at a population level, and rather than addressing the root causes, we've built a multi-billion-dollar industry to work around the problem.

The solution isn't complicated, even if it's inconvenient—eat real food, eliminate modern toxins, support your metabolism, and align your lifestyle with your biology.

Your future children—and theirs—are depending on it.

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