Health  

Why longevity is not genetic

Gene

*Study of 400 million people reveals DNA has barely any impact on how long you will live
*Eating chocolate, drinking tea/coffee, with zinc supplement could help extend lifespan
*Children spending hours in front of screens at risk of short-sightedness, obesity, cancer

Your genes have little to do with how long you will live, according to a new ‘family tree’ study of more than 400 million people.

Deoxyribonucleic Acid (DNA)/genetic material determines many of our traits, and as genetic analysis becomes better and more accessible, it’s tempting to think it can predict our health – and what we will pass on to future generations.

However, longevity is influenced as much – if not more – by environmental factors, like your diet and whether or not you smoke, as well as social factors such as wealth that are even harder to factor into the equation.

But, as the study from research company Calico Life Sciences and Ancestry.com shows, our familial relationships inject much greater uncertainty into the DNA equation.

And while long lives do run in families, we can hardly count on our parents’ longevity to predict our own.

In fact, only about seven percent of our lifespan is based on our genetics, the new research reveals.

As animals, we biologically want to survive as long as possible. And it is in human nature to look for patterns to emulate in those who live longest.

Gerontology is an entire subset of science dedicated to studying aging and everything that determines it. For some scientists, the study of the longest living people borders on obsession as they chase the dream of immortality.

Unsurprisingly, they covet the genetic profiles and life stories of people like Jean Calment, a French woman who holds the record for the longest life ever recorded. She died in 1997, at the age of 122.

She has been called ‘almost immortal,’ and its true that she wasn’t the only one from her family to break the genetic mold: her father died just before his 93rd birthday, her mother died at 86, and her brother lived to be 97.

But her children did not inherit those ‘good genes,’ as we are wont to say. Or, if they did, those genetics didn’t protect them from other variables.

Jeanne’s daughter, Yvonne, died at 35 of pneumonia and her son, Frederic, died at 73 after eating spoiled cherries. Her grandson (also Frederic) died at 36, in a car crash. Her husband, Fernand, died in 1942, at 74.

In the past, scientists believed that between 15 and 30 percent of Yvonne and Frederic’s potential lifespans would have depended on Jeanne and Fernand.

But there is now more family tree and genetic data available for analysis than ever, and GSA’s research shows that our genes have far less to do with longevity than we thought.

The researchers used data from Ancestry.com’s database of 54 million family trees. Altogether, those trees had connected people to six billion ancestors.

Once the redundancies and mistakes were cut out of those trees, the scientists had a set of 400 million people, although the majority were Americans or descended from Europeans, meaning the sample was predominantly white.

Like Jeanne’s family, siblings tended to have similar life expectancies, as did cousins. But those blood-relatives did not have the most similar life spans. It turned out that spouses were more likely to live about as long as one another than were siblings of the opposite sex. Even in-laws tended to have similar live spans.

These genetically inexplicable patterns raised the scientists suspicions, but they narrowed their explanation down to something called “assortative mating.”

“What assortative mating means here is that the factors that are important for life span tend to be very similar between mate,” explained lead study author, Dr. Graham Ruby, of Calico Life Sciences research company.

Essentially, we like ourselves – and we tend to pick partners that are like ourselves.

“Generally, people get married before either one of them has died,” Ruby jokes.

“Because you can’t tell someone’s life span in advance, assortative mating in humans must be based on other characteristics.”

Those characteristics may include inherited physical traits, or factors like wealth, or other social or cultural commonalities that may also influence lifespan (people of similar heights tend to have similar lifespans, but so do people with similar incomes).

Our own families (and all their shared genetic and environmental traits) influence whom we choose as a mate as well.

This may help to explain our tendency to pick partners like ourselves, though perhaps on a subconscious level, as we search out someone aligned with our own values, and whom feels familiar.

So, these may be a series of correlations in gene pools that don’t prove causation – that longevity is actually passed down through DNA.

Once these other traits, which are shared among families, but are not necessarily genetic, pure DNA could only be credited for about seven percent of longevity.

“We can potentially learn many things about the biology of aging from human genetics, but if the heritability of life span is low, it tempers our expectations about what types of things we can learn and how easy it will be,” said Ruby.

“It helps contextualize the questions that scientists studying aging can effectively ask.”

Meanwhile, research suggests that eating chocolate and drinking coffee or tea could help you live longer.

Indulging in the treats while taking zinc supplements activates a compound that slows down ageing, a study found.

This reverses the ‘internal stress’ that naturally accumulates over the years and has been linked to everything from cancer to Alzheimer’s.

Zinc is a relatively safe supplement even at high doses and could therefore be taken regularly to help slow ageing, according to the German researchers.

Researchers from the University of Erlangen–Nuremberg found zinc activates a compound in polyphenols in the lab.

This activation then protects against a gas that is produced as a waste product by cells, according to the research in the journal Nature Chemistry.

This gas can damage a person’s DNA – oxidative stress – and is thought to play a key role in the ageing process.

It also linked to inflammation that can then cause cancer and degenerative diseases such as Alzheimer’s.

Polyphenols cannot break down this damaging gas alone. But when combined with zinc, they create a ‘mega complex’.

This complex mimics the naturally-occurring superoxide dismutase enzyme that destroys the gas to help protect the body from its effects.

This study is the first time the effects of this enzyme have been copied without resorting to the chemical properties of metals such as iron or copper.

Excessive exposure to these metals can cause so-called internal stress on their own. Zinc, however, is much less toxic.

Too much iron has also been linked to liver disease, diabetes and even heart failure, while too much copper can cause fever, anaemia and low blood pressure.

Zinc, however, can be tolerated at higher doses with overexposure largely leading to just nausea and a change in your taste.

The researchers therefore hope it can be taken as a supplement or incorporated as part of a drug with fewer side effects.

It is also plausible to add zinc to foods that naturally contain polyphenols. It already found in high quantities in red meat.

“It is certainly possible wine, coffee, tea or chocolate may well become be available in [the] future with added zinc,” lead author Dr Ivana Ivanović-Burmazović said.

“However, any alcohol content whatsoever would destroy the positive effects of this combination.” This means it could work with alcohol-free wines.

This comes after research released earlier this year suggested chocolate milk boosts exercise recovery more than sports drinks.

The popular milkshake allows athletes to intensely exercise for around six minutes longer than sports drink without tiring, according to Iranian scientists.

Meanwhile, experts say spending too much time gawping at screens is making children more likely to be short-sighted, become overweight and get cancer.

A review of 80 studies on more than 200,000 people has ranked smartphones and tablets alongside sugary drinks as one of the biggest risks for childhood obesity.

Being overweight can lead to a dozen types of cancer, including breast, colon, kidney, liver, ovarian, pancreas and prostate.

As well increasing their risk of dying young, too much time on gadgets is damaging youngsters’ eyes – the number of short-sighted children has doubled in 50 years.

Researchers say the findings are a ‘significant concern’ and call for more control on junk food adverts, which worsen the effects of children doing less exercise.

Research done by the World Cancer Research Fund examined the causes of weight gain in children around the world.

It found increasing amounts of time spent on smartphones, tablets and gaming is a big driver of children getting fatter – that and sugary drinks make up the top two.

“The report highlights the importance of acting early to help prevent cancer,” Sophia Lowes of Cancer Research UK told The Telegraph.

“Obese children are five times more likely to be obese as an adult, which is worrying because then they’ll be at an increased risk of different types of cancer.

“That’s why it’s vital we see a 9pm watershed on junk food adverts on TV and similar protection for children viewing adverts on-demand and online.”

Experts say as well as leading to children doing less exercise, sitting inside looking at screens makes youngsters more likely to overeat on snacks.

They call this “passive over-consumption” – meaning children snack on junk foods which they often see advertised on the same devices they’re spending their time.

In addition to the obesity and cancer risks, spending too much time in front of screens also increase the number of children with myopia – short-sightedness.

The proportion of children worldwide with short-sightedness has more than doubled from 7.2 per cent to 16.4 per cent in the past 40 years.

This effect has been dubbed ‘digital myopia’, and King’s College London researchers, in a separate study, found every hour a day spent on devices raised a child’s risk of sight damage by three per cent.

Past research has suggested children spend, on average, eight hours a day using gadgets.

Professor Chris Hammond, from King’s College, told The Telegraph UK: “I think it is a significant concern.

“We do believe that young children staying indoors and spending hours on screens is bad for eyesight, not to mention obesity and fitness.

“I think our concept in myopia is clearly that close work is a risk factor, and outdoor activity is protective.”

Eye expert, Dr. Mohamed Dirani, wrote in the British Journal of Opthamology: “The age of smart device uptake is getting younger, with many two-year-olds spending up to two hours a day on devices.

“The use and misuse of smart devices, particularly in our paediatric populations, must be closely monitored to address the emerging phenomenon of digital myopia.”

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