Thursday, July 11, 2013

Women who work shifts are 80% more likely to have fertility problems such as miscarriage

Just a social class effect

Women who work shifts are more likely to have reduced fertility levels, new research has revealed.  Shift work also increases the chance of menstrual disruption, while night work increases the risk of miscarriage, the study found.

The annual meeting of the European Society of Human Reproduction and Embryology in London heard that previous research has linked shift work, which causes sleep deprivation and disruption to the body clock, with ill health.

But little was known about the effects of shift work on reproductive health and fertility.

Dr Linden Stocker headed a study by the University of Southampton which found links between shift patterns and fertility problems.

The study is a meta-analysis of all studies on the subject published between 1969 and January 2013 and included data on 119,345 women.

It found that those working shifts had a 33 per cent higher rate of menstrual disruption than those working regular hours, and an 80 per cent increased rate of reduced fertility.

Women who worked only nights did not have an increased risk of menstrual disruption or difficulty conceiving, but they did have a 29 per cent increased rate of miscarriage.

The investigators describe their findings as ‘novel’, but in keeping with other studies.

Dr Stocker said: ‘If replicated, our findings have implications for women attempting to become pregnant, as well as for their employers.’

She added: ‘Whilst we have demonstrated an association between shift work and negative early reproductive outcomes, we have not proven causation.

‘In humans, the long-term effects of altering circadian rhythms are inherently difficult to study. As a proxy measure, the sleep disruption demonstrated by the shift workers in our study creates short- and long-term biological disturbances.

‘Shift workers adopt poor sleep hygiene, suffer sleep deprivation and develop activity levels that are out-of-sync with their body clock.

‘However, if our results are confirmed by other studies, there may be implications for shift workers and their reproductive plans.

‘More friendly shift patterns, with less impact on circadian rhythm, could be adopted where practical - although the optimal shift pattern required to maximise reproductive potential is yet to be established.’

She said that the underlying biological disturbances involved in reproductive difficulties ‘are complex and not the same across all the disease processes’.

‘Indeed,’ she said, ‘it is probable that completely different causes underlie menstrual dysfunction, miscarriage and subfertility.

‘This may explain why the effects of different types of shift work are seen in some groups of women, but not others.’


Taking high doses of vitamins could reduce your life expectancy by up to a quarter

Taking vitamin pills in high doses could be bad for your health, say scientists.

A study found that voles who were given a lot of vitamins C and E had a reduced lifespan of up to a quarter.

Researchers said the findings, published in Biology Letters, raise questions about the benefits of popping the supplements.

The human body does not make or store vitamin C and gets its supply from fruit and vegetables. It only needs 40mg a day to keep cells healthy and promote healing.

Vitamin E helps maintain the structure of cells and is found in foods such as nuts, seeds, and cereals.  A man needs just 4mg a day and a woman should have 3mg. But tablets containing up to a hundred times this amount are available in health food shops.

Researchers fed field voles large quantities of Vitamin E or C from the age of two months and compared their longevity to groups given a regular diet.

They say that voles were used for the study as giving such high quantities of vitamins to humans would be unsafe.

High doses of dietary antioxidants, such as vitamins, are commonly suggested to slow the process of cellular ageing by lessening the damage to proteins, lipids, and DNA.

Previous research had shown the lives of mice could be extended by giving them supplements, but the opposite was found to be true in voles. They had much shorter lives on average if given extra Vitamin E or C.

But despite these effects, the vitamin supplements had some effect in decreasing damage caused by aging.

Professor Colin Selman, of Glasgow University, said: ‘When we began our research we expected voles' lifespans would be boosted by the vitamin supplements in a similar way to the mice we had tested previously so we were surprised to see that was not the case.

‘Our findings suggest major differences exist in the effects of high doses of antioxidants on oxidative damage and lifespan across species.’

Britons spend £175million a year on supplements and pills containing antioxidants claimed to help combat disease.

Most popular are Vitamins C and E and beta-carotene - the pigment found in carrots, tomatoes and broccoli which the body converts into Vitamin A.

Ten million Britons take these vitamins regularly but some scientists have dismissed them as useless while others have branded them dangerous.

Professor Selman said: ‘There's been a lot of research suggesting at best vitamin supplements produce no benefit and at worst can have deleterious effects.  ‘Vitamin E pills have been linked with prostate cancer and an increased risk of all-cause mortality for example.

‘Most of the benefits have been shown in lab rodents so it's interesting the supplements were reduced the lifespan of voles which usually live for about 500 or 600 days.

‘What we did not look at is what they actually died of so it would be important to discover that in the future.’

Professor John Speakman, of Aberdeen University, said: ‘It's unlikely randomised controlled trials examining the effects of antioxidant supplementation on human lifespan would be possible so we are dependent on the results of animal studies.

‘It's impossible at this stage to extrapolate the results from this small amount of data we have on voles and mice but it does suggest caution is warranted in the use of high doses of antioxidant vitamins.’

Graham Keen, Executive Director of the Health Food Manufacturers' Association commented: 'The vitamin and mineral supplements industry has an exceptional record of both safety and efficacy, in the UK and worldwide.

'Figures published by the Food Standards Agency showed that there were only 11 reported reactions to food supplements over an 11 year period, the majority of them in the lowest category of harm.'


The above is an animal study only but there are other findings of similar conclusions: here and here and here and here and here and here and here and here, for instance.

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