If you’re reading this there’s a good chance that you, like me, are a millennial. If so, you’ve probably noticed more and more cases of friends or acquaintances with diseases that you would normally associate with later adulthood – hypertension, type 2 diabetes or perhaps even the one that we’re all scared to name: cancer.
Millennials – people born between 1981 and 1995 – are the first generation at greater risk of developing tumours than their parents. Between 1990 and 2019, cases of early-onset cancer among people under 50 increased by 79 per cent worldwide, and mortality by 28 per cent.
The truth is that around 80% of cancers are “sporadic” , meaning they are not caused by hereditary mutations but by external factors that damage DNA over time. This includes what we eat and breathe, as well as our level of physical activity, rest, stress and exposure to harmful substances.
In other words, the things that make the biggest difference are the lifestyle factors that surround us every day, and not the genetics we inherit. And we know that our parents’ and grandparents’ lifestyles differed greatly from our own.
One of the main factors behind this “new epidemic” is diet. Childhood obesity began to skyrocket in the 1980s. In 2022, more than 390 million children and adolescents aged 5 to 19 were overweight – 160 million of these were obese, according to the WHO .
This condition is not just a question of aesthetics: it is associated with insulin resistance, low-grade chronic inflammation, and hormonal changes that increase the risk of developing colorectal, breast, or endometrial cancer.
Most importantly, the effects of childhood obestity do not disappear with age. According to the Colon Cancer Foundation, a meta-analysis involving more than 4.7 million people showed that those with a high body mass index (BMI) in early life are at greater risk of colorectal cancer in adulthood: 39 per cent higher in men and 19 per cent higher in women compared to those who had a healthy BMI in childhood.
Changes in diet have also altered our gut microbiota. It has been shown that diets rich in ultra-processed foods reduce bacterial diversity, and increase the proportion of strains that produce pro-inflammatory metabolites.
This contributes to gastrointestinal diseases such as irritable bowel syndrome or SIBO , which often seem to be endemic among millennials – ask a group of thirty-somethings which of them suffers from gastrointestinal problems and you’ll find few hands are left unraised.
The second major culprit is alcohol, as millennial gatherings often revolve around a table laden with food and drink . For years it was thought that a glass of wine was could “protect” you in some way, but today we know that there is no safe level of alcohol consumption: the International Agency for Research on Cancer classifies it as a Group 1 carcinogen, on the same level as tobacco. This is because the body converts ethanol into acetaldehyde, a compound that damages DNA.
Furthermore, consumption patterns differ between generations. While baby boomers (those born between 1946 and 1964) drink more on a daily basis, millennials tend to drink less frequently but engage in more binge drinking , which carries significant risks. This is confirmed by the Spanish Ministry of Health’s 2024 EDADES survey , which explores the different levels of risk associated with different behaviours across generations.
We sleep less and worse than previous generations. Recent surveys show that millennials and generation Z get an average of 30-45 minutes less sleep per night than baby boomers, largely due to night-time exposure to screens and social media. This artificial light disrupts the release of melatonin, an antioxidant hormone that regulates the cell cycle.
Chronic lack of sleep not only impairs DNA repair, but also reduces melatonin’s protective effects against cancer. Reduced levels of this hormone have been linked to a reduced ability to counteract oxidative DNA damage and increased cell proliferation.
Millennials are probably the generation with the highest cortisol levels . When this “stress hormone” remains elevated for a long time, it not only promotes insulin resistance and hypertension, but also weakens the immune system.
Research reveals that chronic stress increases inflammation, hinders the body’s defences from eliminating abnormal cells, and can even “awaken” dormant tumour cells. In fact, studies in the general population have found that people with higher stress levels are up to twice as likely to die from cancer as those who manage stress better.
-By Lydia Begoña Horndler Gil, profesor en inmunología y biología del cáncer, Universidad San Jorge
