Generational decline in testosterone: why is it happening and what can you do?

Why is testosterone in men declining generation by generation?

Why your forefathers had higher testosterone levels than you…

It’s perfectly natural and expected for men’s testosterone levels to decline with age but recent research shows levels have been dropping further than usual decade by decade. The burning question is why might men today have lower levels than their grandads or great grandads and can anything be done to buck the trend?

Testosterone levels in men are known to fall steadily by roughly 1%-2% a year from around their late 30 onwards¹ but a range of recent studies suggest levels are declining at a faster level than simply ageing. To put this in some sort of context: a US study from 2007 concluded that testosterone levels from 100 years ago – for men born in the 1920s – were higher than those born in the 1960s. Plus, on average the testosterone of a 60-year-old in 1989 was higher than that in a 60-year-old male in 1995.² Researchers suggest levels appear to be going down by around 1 % a year. The trend appears to be global with further studies confirming comparable findings – research carried out in Finland³ and Denmark⁴ show similar results and a large study of Israeli men published in 2020 has shown average testosterone levels dropped by around 10% between 2006 and 2019⁵, And a more recent US study published in 2021 involving over 4,000 healthy men aged between 15-40 shows a decline of almost 25% in testosterone levels among adolescent and young adult men over the last 20 years.⁶

Why are testosterone levels in men declining?

The honest answer to this question is that nobody knows for certain and it’s hard to pinpoint any one cause. Plus, we won’t know definitively that a 60-year-old Millennial male (born between 1981 and 1996), say, will have significantly lower testosterone that a Boomer (born between 1946 and 1964) at the same age but going by current trends it is looking increasingly likely. Whilst more research is needed to understand why this is happening there are a range of lifestyle, behavioural and environmental factors that researchers theorise could be contributing to it including:

The way we work and live

It is easy to forget sometimes just how radically the digital age has transformed the way we live and work compared to previous generations. Much twenty first century work tends to be office based or done from home - making many of us considerably less active than the generations who came before us (and who were possibly more likely to have had jobs which involved manual labour). This is significant for testosterone levels in men as evidence shows men who lead more sedentary lives tend to have lower testosterone levels than ones who are more active.⁷ Linked to this change in working patterns is also a recorded drop in men’s grip strength.⁸

Being overweight

Related to the above, the impact of our 24/7, possibly WFH, world where anything can be delivered to your door at the press of a button is clearly impacting on how much we move (or don’t) and it is markedly different to how our forefathers lived. Our increasingly sedentary lifestyles have led to rising levels of being overweight and/or obese and this is almost certainly impacting on testosterone levels. One study involving 1667 men aged between 40 and 70 shows that a rise in BMI by four to five points was associated with the testosterone levels of someone a decade older.⁹ However, since testosterone levels have also been shown to have declined in healthy men with a normal BMI it is suggested that other factors need to be taken into consideration.¹⁰

Changing relationships

Interestingly, certain close relationships – including marriage, fatherhood and increased time spent caring for children - are linked to lower testosterone levels. Married men have lower levels of testosterone than single men according to research.¹¹ Multiple studies have also shown that fathers have lower testosterone levels than men who are not dads¹² – and these may never return to pre-baby levels. Nobody is exactly sure why this should be the case but it is variously attributed to increased stress, lack of sleep and/or an increase in the production of the so-called ‘cuddle hormone’ oxytocin experienced by fathers. A fascinating 2022 study has also found adult men had lower testosterone levels if their father was around when they were growing up and involved with their care but boys whose dads were present but not actively involved in their care grew up to have higher levels of testosterone.¹³ The fact that there are more full-time stay at home dads, co-parenting dads and/or dads more heavily involved in childcare than 50 years ago certainly appears to be having an impact of testosterone levels.

What we eat and drink

Our diets have changed dramatically since the 1970s¹⁴ – we now have a huge amount of choice when it comes to ingredients, including many highly nutritious ones, but we have also seen a dramatic rise in convenience, ultra-processed or ‘fast’ foods which are often low in nutrients and high in sugar and/or unhealthy fats. Why this is significant is that there is some evidence to suggest eating an ultra-processed diet may contribute to lower testosterone.¹⁵ Research also shows that some dietary fats – particularly trans fats (found in small amounts naturally in certain foods such as meat and dairy products but also made when liquid fats are turned into solid ones to prolong their shelf life) and too many omega 6 fatty acids (found in some plant oils and seeds, which are healthy in small amounts but not if you have too much of them) - can adversely influence testicular function in young healthy men.¹⁶ There is also evidence to suggest binge drinking or prolonged heavy drinking over extended periods can cause testosterone levels to decline.¹⁷

Fewer smokers

Some studies have shown that smoking could push up testosterone levels by a small amount.¹⁸ It is thought that this is due to a component in nicotine called cotinine which may prevent testosterone from breaking down.¹⁹ There’s absolutely no suggestion that men should take up smoking in order to raise their testosterone levels but this is quite a big change in recent behaviour - according to figures from the Office of National Statistics (ONS) the number of male smokers has reduced from 51% in 1974 to 20% in 2014 and it is thought to be even lower now.²⁰ How does vaping compare? Research is still in its early stages and whilst some studies have found that testosterone levels are altered by using e-cigarettes others have found no significant impact. They are, however, associated with lower sperm count.²¹

Using mobile phones

The fact that many of us are practically surgically attached to our smart phones these days is another generational change that could be potentially impacting on testosterone levels and male fertility. Carrying your mobile in your trouser pocket (ie. in close proximity to your testicles) has been especially linked to a reduction in testosterone levels and sperm count²² although the evidence is largely inconclusive at this stage. It is recommended, however, that you don’t keep your mobile close to your body and especially not in the pockets of your trousers or shorts.

Environmental pollutants

Researchers are studying how our increased exposure to environmental toxins such as pesticides, parabens and other chemicals common in household products could be impacting on hormone health. Many of these contain endocrine-disrupting chemicals (EDCs) which are found in everyday products such as plastic bottles, detergents and food storage containers, some of which can be slow to break down and may accumulate in the body over time. Several EDCs have been linked to lower testosterone levels and lower sperm quality although more research is necessary to fully understand the association.²³ There has also been concern around the levels of pharmaceuticals in our tap water (such as antidepressants, recreational drugs, painkillers and tranquillisers) and, significantly, oestradiol, a type of oestrogen,²⁴ which is believed to be excreted into the water supply by women after taking the hormone contraceptive pill. Some researchers suggest oestradiol could have an adverse effect on men long term who may develop more breast tissue than men in previous generations and could potentially have problems with abnormal prostate development.²⁵

7 ways to boost, and maintain, testosterone levels

You might have no control over some of the factors attributed to lowered testosterone levels but there are many you do and by making a few simple but strategic lifestyle changes you can boost and maintain yours including:

1. Regular exercise. Men who do regular moderate exercise have been shown to have higher testosterone levels compared to those who are more sedentary. Exercising too much and too hard, however, can suppress testosterone production – studies show men who over-exercise are more likely to have lower testosterone levels and report lower libido^26,27

2. Eat testosterone-boosting food. Eating a healthy balanced diet with plenty of fresh, unprocessed food such as the Mediterranean diet is important for maintaining general good health as well as optimal testosterone levels. Many nutrients including vitamin D, zinc and magnesium are important for maintaining testosterone. Specific foods also appear to be particularly beneficial including oysters, avocados, salmon, mushrooms and vegetables such as broccoli and cauliflower.

3. Maintain a healthy weight. A study involving 1,849 men found that 40% of obese men had low testosterone levels. Carrying excess fat can lead to insulin resistance (where your body is unable to process insulin normally and help regulate your body’s blood sugar) which not only puts you at an increased risk of type 2 diabetes but is also implicated in disrupting the delicate balance of hormones in the body, including testosterone. These trends can be quite easily reversed, however, as testosterone levels increase quite significantly as you lose weight.²⁸ One way to shed the pounds is by time-restricted eating or intermittent fasting. 

4. Get enough sleep. Sleep not only helps to keep you generally healthy it also helps facilitate normal testosterone production (levels increase as you sleep and decrease the longer you are awake). Research suggests men who don’t get the recommended seven to nine hours a night may have lower testosterone levels. 

5. Take testosterone supporting supplements. Look for ones that contain a good range of nutrients including zinc (a deficiency of which is associated with lower testosterone)²⁹ - as it has been proved that zinc contributes to the maintenance of normal testosterone levels³⁰ by EFSA.

6. Manage stress. Whilst it is not possible to avoid stress completely if it is chronic and prolonged it can significantly impact on testosterone levels, reducing production at its very source – from the testes.^31,32 Exercise can help to manage stress, as can getting enough sleep but other tools that can help include breathing exercises, meditation, yoga, getting outdoors and/or taking stress-regulating adaptogenic herbs such as ashwagandha. An eight-week study from 2022 involving men given 300mg of ashwagandha twice daily showed they had increased testosterone and reported improved sexual functioning at the end of the trial.³³

7. Testosterone replacement therapy (TRT) – if lifestyle changes don’t help TRT could help restore testosterone levels to a healthier range. In order to be prescribed testosterone you need to have an official diagnosis of low testosterone from a GP or health professional first.

References

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