It’s the age old question (pun intended), and one that has given rise to an anti-ageing industry that is estimated to grow to $216.52 billion by 2021: how can we, mere mortals that we are, live longer?

According to recent studies, the answer could well lie in Japan. The Japanese top the global table for life expectancy: on average, they can expect to live for 83.7 years (the UK comes 20th, with an average of 81.2 years).

And this week, they hit another milestone, as it was revealed that the number of Japanese people aged 90 or over has hit the two million mark for the first time.

So, what is it that they’re putting in the water in Japan? Have they found a mainstream supply to the fountain of youth?

More realistically, the Japanese seem to have their finger on the pulse when it comes to lifestyle. Their diet is lean and balanced, consisting mainly of fish, seafood, whole grains, vegetables and tofu. The processed Western foods that science is now linking to an array of health issues are largely absent from Japanese plates.

This healthy approach to eating reflects in the country’s rate of obesity, which is impressively low at just 3.5pc of the population (it looks even better when you compare it to the UK’s dismal 24.9pc). It hardly needs saying that obesity is now considered a killer, linked to everything from coronary heart disease to diabetes and cancer.

And, importantly, the Japanese start young. Schools in the country adhere to dietary guidelines that Jamie Oliver can only dream of, with lunch plans consisting of very little refined sugar. Naomi Moriyama, author of Secrets of the World’s Healthiest Children: Why Japanese Children Have the Longest, Healthiest Lives — And How Yours Can Too told Today, “this way, believe me, children learn to like the healthy, delicious choices put in front of them.”

It’s not all about diet, however. The Japanese healthcare system is considered one of the world’s best, combining advanced medical knowledge and equipment with an accessible public/private hybrid model that sees the government pay at least 70pc of the cost of procedures (more if you’re on a low income). For a developed country, it’s an eye-catchingly cheap arrangement: Japan’s healthcare system sucks up around 9.5pc of GDP (compare that to America’s 16.4pc), even though it has an aging population.

The government has also taken preventative measures to care for its citizens. A recent focus on suicide prevention as seen impressive results: in 2012 in was reported that the number of suicides in Japan fell below 30,000 for the first time since 1998. “Initially we thought that this was just temporary, a blip,” Dr Tadashi Takeshima, Director of Japan’s Centre for Suicide Prevention at the National Institute of Mental Health, told the WHO. “But in 2013 we saw a further decline in the numbers.”

Access to good healthcare and a tendency towards fish certainly help the Japanese live longer – but there are some studies that suggest their longevity may simply be down to having good genes. Two very specific genes, in fact.

The first is DNA 5178, which helps individuals resist adult-onset diseases, such as myocardial infarction, cerebrovascular diseases and type 2 diabetes. The second, ND2-237Met genotype, may confer resistance to cardiovascular and cerebrovascular atherogenic diseases. Japanese people are more likely to have these genes, although, as ever with genes, it’s something of a lottery on an individual case. Some receive more ‘life extending’ genes than others.

Regardless, it’s fair to say the average Japanese person is likely to have been raised in an environment consistent with extended life. For example, in 2012 it was reported that the 98pc of Japanese children walk or cycle to school.

So, if you’re looking for a long and healthy life, hopping on a Boris bike might just get you that letter from the Queen.