Monday, February 24, 2014
MEN are warned: Older dads are more likely to have 'mutant sperm'
This seems pretty dubious to me. Mutated sperm would be less fit and hence less likely to reach the egg first. Nature's own filtering system should take care of the problem proposed
The longer a man delays fatherhood, the more likely his sperm is likely to become 'mutant', researchers have warned.
They say that older fathers have a higher risk of fathering a child with a disorder such as autism or schizophrenia.
This is because mutations cause stem cells in the testicles to divide abnormally, resulting in an increasing proportion of mutant sperm as men age, New Scientist reports.
Some studies have even linked having an older father to Alzheimer's disease, bipolar disorder (previously known as manic depression), heart disease and cancer.
Now, scientists warn that a man in his 40s is twice as likely to pass down potentially disease-forming genetic mutations as a man in his 20s - indicating that the biological clock ticks for men, too.
Plenty of high-profile men have become late-life fathers, including Steve Martin at 67, David at 53 and Des O'Connor, who became a father for the fifth time at 72.
For decades, scientists have speculated about links between older fathers and birth defects. But it was only recently that a groundbreaking study, published in the respected journal Nature, proved that men undoubtedly pass on more genetic mutations to their children as they get older.
Researchers sequenced the DNA of 78 Icelandic parents and their children and found a direct correlation between the father's age and the number of mutations linked to autism spectrum disorders and schizophrenia in a child's DNA.
The mother's age had no bearing on their risk - indeed, the team found that 97 per cent of all mutations in a child's DNA come from their father.
'Society has traditionally been very focused on the age of the mother,' says Dr Kari Stefansson, of Decode Genetics, a leading genetic research company, who led the study.
'But it seems that disorders such as schizophrenia and autism are actually influenced by the age of the father and not the mother.'
Dr Stefansson's report suggested that the apparently surging numbers of children diagnosed with autism may at least in part be explained by the ever-increasing age of fathers
It is thought that just as a man's memory and skin elasticity gets worse with age, the quality of his sperm seems to as well.
Crucially, unlike women who are born with a complete set of eggs, men continually make new sperm throughout their lifetime.
Every 16 days, cells in the testicles divide and the DNA in each cell is copied into a new one which is used to make new sperm.
The body is highly accurate at making an exact copy, but inevitably it sometimes makes mistakes. Some sperm will be made containing an error in the DNA - what's known as a genetic mutation.
As a man gets older, the copying process becomes tired and less efficient and his sperm contains more mutations.
And if mutated sperm is then used to form a foetus, there's more chance of problems in its development, says Professor Wilkie.
'It's a game of chance. It may be that this mutation does not occur in a critical place. But sometimes the game of chance is against you and the mutation hits a gene that will lead or predispose your child to a certain condition.'
So if the mutation is in the gene controlling brain development, for example, it can cause autism or schizophrenia.
And potentially if a mutation occurs in a gene affecting your risk of a type of cancer, it could increase the chances of the child getting it in later life.
Dr Allan Pacey, the country's leading authority on male fertility, says it's time for a wake-up call on the dangers of putting off becoming a dad. 'I can understand why couples do it, but it's bad biology.
My advice is for men to have children as young as possible - don't wait until you're in your 50s. It will make all the difference in the world to your children's health.'
Another great fad unwinds: Vitamin E supplements 'raise risk of prostate cancer by 20%... and have NO health benefits'
Men should not take high doses of vitamin E or selenium supplements because they have no health benefits and increase the risk of prostate cancer by up to a fifth, scientists have claimed.
Vitamin E, naturally found in nuts, spinach and broccoli, is taken to boost the body’s immune system and the mineral selenium, found in fish and meat, is taken to ward off heart disease.
But US researchers claim large doses of both can increase the risk of prostate cancer by 17 per cent.
This can rise to as much as 91 per cent if a man already has high levels of selenium before taking supplements.
The warning centres on high-dose supplements, with researchers saying there appear to be no risks from taking a standard multivitamin.
But nor were there any apparent benefits from the supplements.
Lead researcher Alan Kristal, of the Fred Hutchinson Cancer Research Centre in Seattle, said: ‘Men using these supplements should stop, period.
Neither selenium nor vitamin E supplementation confers any known benefits, only risks.’
The study looked in detail at a past trial, carried out to test whether extra vitamin E and selenium could help prevent prostate cancer.
But instead, researchers discovered more cases of prostate cancer among men taking 400 international units (IU) of vitamin E daily than those taking a placebo.
This is the equivalent of 363mg a day, which is 30 times the recommended daily amount.
Men with low levels of selenium were the most affected by extra vitamin E – with the supplements raising their prostate cancer risk by 63 per cent.
‘We know from several other studies that some high-dose dietary supplements – that is, supplements that provide far more than the daily recommended intakes of micronutrients – increase cancer risk.’
More than 35,000 healthy men in their 50s and older took part in the initial trial, which began in 2001. Further investigation of this data, published yesterday in the Journal of the National Cancer Institute, revealed the latest findings.
In the UK, the recommended daily amount of vitamin E is 12mg, and most multivitamin pills contain between 15mg and 30mg.
However, the UK Expert Group on Vitamins and Minerals says the upper ‘safe’ limit is between 700 and 800mg a day – twice as much as taken in the trial.
Dr Matthew Hobbs, deputy director of research at Prostate Cancer UK, said more studies were needed, but added: ‘If men are concerned about their prostate cancer risk, rather than worrying about selenium and vitamin E supplements, they should talk to a GP
Posted by jonjayray at 12:18 AM