Puberty, the culprit of many teenage woes, has been under significant scrutiny for decades. Characterised by the rapid maturation into an adult body capable of reproducing, girls and boys experience its effects and timings completely differently.

As of 2024, boys and girls typically go through their first puberty stage at around 10, a significant shift from the average of 11 just 30 years ago. This pattern of earlier onset has been observed over the centuries. In the 18th century, children generally started at 12, and in the 17th century, they began at 13, with historical records suggesting that the average age of puberty was around 15 in even earlier times.

Some may attribute this rising age to a lack of nutrition, but even the richest families experienced similar ages in their children’s reproductive development. This begs the question: what has changed? What has happened over the most recent centuries that has caused the average age of puberty to drop by five years, reaching its lowest point since records began?

Firstly, since the 1970s, numerous studies have linked overweight and obese girls with earlier periods than those of average body mass. In fact, girls who weighed 10 kg above their range are associated with twice the likelihood of precocious puberty. This may be due to adipose tissue’s effect on increased oestrogen production, the governor of female reproduction. However, overweight and obese boys saw the opposite effect. Due to excess oestrogen, they had lower testosterone production, inadvertently delaying testicular development.

However, obesity is not the only antagonist. A 2009 study in Copenhagen found that girls were getting their periods earlier than previously reported. But unlike places like the United Kingdom and the USA, their body mass index was within normal ranges and had not changed in 20 years. Similarly to the heavier countries, however, their puberty ages were dropping. One theory for this conclusion is the immense chemical exposure we impose upon our population. Further interest led the most vocal proponent of this theory to discover that the Danish girls entering precocious puberty had elevated levels of phthalates in their urine. This substance is used to make plastics more flexible and transparent and is found in almost everything. From medical devices to shampoo bottles and nearly all food packaging containers, phthalates are completely unavoidable in our modern society. Known to disrupt our endocrine systems, they have been associated with reproductive and developmental issues, lowering testosterone in men and increasing the proliferation of PCOS. Moreover, we know that boys with significant levels of phthalates in their urine experienced the opposite effect of the girls, having an increased age of puberty.

Diet also plays a part in the disrupted development our children are facing. Animal studies have shown that diets high in phytoestrogens, usually sourced from soybean products, alter pubertal timing, impair oestrous cycling, and dysregulate ovarian function. The interesting part is that rats and mice, the animals used in these studies, metabolise phytoestrogens similarly—both producing equol, a potent oestrogenic compound. However, little evidence has been shown for this having a significant impact on age. Diets high in animal protein were associated with earlier puberty in girls, but findings aren’t reliable due to a lack of control for body fat mass.

Finally, chronic stress has been linked to earlier puberty. Unlike acute stress, which refers to a short-term reaction, chronic stress—prolonged and constant—has been shown to cause earlier puberty in girls. For example, victims of sexual abuse had an earlier onset than average. Similarly, girls who did not live with their biological fathers experienced the same outcome.

It is difficult to pinpoint the exact consequences of this phenomenon. However, we now have a society with the highest recorded fertility issues, the most menstrual irregularities in young women, and skyrocketing psychological issues among young people. For girls, there is a rising prevalence of conditions like PCOS. For boys, we have the lowest testosterone levels in modern history, alongside the least muscle mass and worst sperm count.

Is this a result of early-onset puberty? Or is it just part of the multitude of factors contributing to our deteriorating quality of life? If you were to ask me, this highlights the importance of reducing oestrogen within our lifestyle and suggests that it is not part of a separate paradigm.