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Health News from NHS Choices

Constantly updated health news across a range of subjects.

NHS Choices News

  • GI diet 'debunked' claims are misleading

    Today, the Mail Online says, “The GI diet debunked: Glycaemic index is irrelevant for most healthy people”, explaining how “it doesn't matter if you eat white or wholewheat bread”.

    This is overgeneralised and misleading, so the diet certainly hasn't been "debunked".

    Glycaemic index (GI) measures how quickly foods containing carbohydrates raise blood sugar levels in the bloodstream. It’s used in some diets on the basis that foods that raise blood sugar slowly (low-GI) are considered better for you.

    This small US study tried mainly obese people on different high- and low-carbohydrate versions of the GI diet for five weeks at a time.

    It found that low-GI diets were no better than high-GI diets at reducing certain risk factors for cardiovascular disease and diabetes.

    However, the results came from mainly obese adults, a quarter of whom had high blood pressure – so may not necessarily represent “most healthy people”. The very select group involved in this research makes it difficult to generalise the findings to the wider population.

    What this trial tells us is that selecting low-GI foods as a way to reduce risk of diabetes and cardiovascular disease might not be any more beneficial than choosing high-GI foods.

    This is food for thought for those aiming to reduce disease risk through dietary modifications, and for health professionals advising them.

     

    Where did the story come from?

    The study was carried out by researchers from Harvard Medical School and collaborators. It was funded by the (US) National Heart, Lung and Blood Institute; National Institute of Diabetes and Digestive and Kidney Diseases; the Harvard Clinical and Translational Science Center; the National Center for Advancing Translational Science; and the general clinical research center at Brigham and Women’s Hospital.

    The study was published on an open -access basis in JAMA, a peer-reviewed medical journal.

    The Mail Online got its headline a bit wrong when saying that the results applied to “most healthy people”, as the study had specific eligibility criteria to include people with a BMI over 25, some of whom had high blood pressure. It was also not correct to say that GI diets have been “debunked”, as the results may not be generalisable to the wider population.

     

    What kind of research was this?

    This was a randomised crossover trial (RCT) looking at the effect of different diets on cardiovascular disease and diabetes risk factors. The dietary elements of interest were carbohydrate content and GI.

    GI is a measure of how quickly foods containing carbohydrates raise blood sugar levels in the bloodstream. High-GI foods cause a short-term spike in blood sugar level, while low-GI foods cause a more prolonged and smaller rise in blood sugar.

    Some popular diets advocate the consumption of low-GI foods, based on the assumption that low-GI is healthier than high-GI. However, the researchers point out that the independent benefits of GI on health are uncertain.

    An RCT is one of the best methods to isolate the effects of a dietary intervention such as this. Common issues reducing the reliability of RCTs are a lack of compliance to the diet, high levels of people dropping out of the study, or only recruiting small or highly specific numbers of people. Anything less than a couple of hundred is generally considered small. In this RCT, participants were assigned to trial at least two of the different diets, with a wash-out period in between.

     

    What did the research involve?

    Researchers recruited 189 overweight people (all had a body mass index (BMI) of 25 or above) and randomly allocated them to follow one of four strictly controlled diets for five weeks.

    After this first phase, they were allowed a break to eat what they wanted for two weeks – called a wash-out period. After the wash-out period, they were randomly allocated a second time to a different diet for a further five weeks. 

    To be eligible, people had to have a systolic (upper figure) blood pressure of 120 and 159mmHg and diastolic (lower figure) of 70 to 99mmHg. On this basis, some of the people could have had normal blood pressure, some borderline/pre-hypertension, and some high blood pressure (hypertension).

    Other eligibility criteria included being aged 30 or above, and being free from diabetes or cardiovascular disease, and not taking medication related to these conditions.

    The researchers aimed to ensure that everyone included in the trial went on two different strictly controlled diets for five weeks, with a two-week gap in the middle.

    The background diets from which GI was manipulated were healthy dietary patterns established in the Dietary Approaches to Stop Hypertension (DASH) and Optimal Macronutrient Intake to Prevent Heart Disease (OmniHeart). These are diets that, the authors state, are being recommended in dietary guidelines to prevent cardiovascular disease (CVD).

    Participants were randomised to one of four different diets:

    • high-GI, high-carbohydrate
    • low-GI, high-carbohydrate
    • high-GI, low-carbohydrate
    • low-GI, low-carbohydrate

    All food and drink was provided and controlled by the researchers. The researchers directly monitored how people stuck to each diet through food diaries and the participants making daily visits to a centre, where the researchers directly observed them eating their main meal of the day. 

    The main health measurements of interest were risk factors for diabetes and cardiovascular disease, including:

    • Insulin sensitivity. Taken via an oral glucose tolerance test, this shows how the body metabolises carbohydrates – specifically, how sensitive your body is to the effect of insulin. A tendency towards glucose intolerance can be a sign of higher risk of developing diabetes in the future.
    • LDL cholesterol – so-called “bad cholesterol”.
    • HDL cholesterol – so-called “good cholesterol”.
    • Blood fat levels.
    • Systolic blood pressure – the top number in a standard blood pressure measurement representing blood pressure as the heart contracts.

    The analysis was restricted to people who had successfully completed the two diets, one after another, with the two-week gap in the middle.

     

    What were the basic results?

    Of the 189 randomised to start the trial, 163 completed enough of the study to be included in the final analysis. Compliance to the diets was high. The average BMI was 32 (BMI above 30 is classed as “obese”) – 92% of participants were obese or heavier. Around a quarter of people (26%) were defined as having high blood pressure. The main findings fell into three groups, summarised below.

    Low-GI, high-carbohydrate diet, compared with high-GI, high-carbohydrate diet

    • insulin sensitivity worsened by 20%
    • bad cholesterol increased by 6%
    • good cholesterol, blood fat levels and systolic blood pressure were not any different between the groups

    Low-GI, low-carbohydrate diet, compared with high-GI, low-carbohydrate diet

    • blood fat levels reduced by 5%
    • all other measures were not different between the groups

    Low-GI, low-carbohydrate diet, compared with high-GI, high-carbohydrate diet

    • blood fat levels reduced by 23%
    • all other measures were not different between the groups

    The researchers’ main conclusion was that: “In the context of an overall DASH-type diet [a diet to prevent or help people with high blood pressure], using GI to select specific foods may not improve cardiovascular risk factors or insulin resistance.”

     

    Conclusion

    This RCT showed that low-GI diets might not reduce risk factors for diabetes and cardiovascular disease in a group of mainly obese adults. All of these adults were free from diabetes or current cardiovascular disease, although a quarter of them had high blood pressure, and some may have had borderline high blood pressure.

    As such, the trial’s participants were a specific group. This means that the results may not be relevant to the general population or other subgroups – for example, those who are a healthy weight or have an existing medical condition, such as diabetes.

    However, compliance to the dietary interventions was high and the statistics seemed sound, thereby increasing our confidence in the results. If the findings were replicated in other studies, or if this trial had included more participants and/or been longer in duration, we could have some confidence in saying that for this group, the GI diet did not have the expected benefits. However, for example, if any of the effects of GI took longer than five weeks to occur, this study will not have picked them up. 

    The authors themselves make the points that GI is only one attribute of carbohydrate-containing foods. They said: “Further, nutrients often cluster. Hence, the effects of GI, if any, might actually result from other nutrients, such as fibre, potassium and polyphenols, which favourably affect health.”

    The study achieved a high compliance to the diets, through food diaries and observation. If this was attempted in real life, compliance would be much less. This would mean that any GI effects would probably be even smaller than was found in this study.

    For this group of overweight people, the evidence of the GI diet reducing certain risk factors for cardiovascular disease and diabetes is lacking. The diet certainly haven’t been “debunked” for “most healthy people”, as the Mail Online claimed.

    Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

    Links To The Headlines

    The GI diet debunked: Glycaemic index is irrelevant for most healthy people - so it doesn't matter if you eat white or wholewheat bread, scientists claim. Mail Online, December 17 2014

    Links To Science

    Sacks FM, et al. Effects of High vs Low Glycemic Index of Dietary Carbohydrate on Cardiovascular Disease Risk Factors and Insulin Sensitivity. The OmniCarb Randomized Clinical Trial. JAMA. Published December 17 2014



  • Ibuprofen unlikely to extend life

    The Daily Mirror today reports that, “taking ibuprofen every day could extend your life by up to 12 YEARS”. The Daily Express also has a similar front page headline, while the Mail Online suggests that these extra years would be of “good quality life”.

    If you read these headlines and felt sceptical, you’d be right to do so.

    The news has been extrapolated to humans, based on research in yeast, microscopic worms and fruit flies. These organisms are often used in longevity research due to their naturally short lifespans – even the longest-lived among them is measured in days, not decades. 

    However, if a chemical does extend lifespan in these relatively simple organisms, this is not a guarantee that it will do the same in more complex organisms, such as mammals. We also have no idea whether any extension of life would be of “good quality”.

    Even in the fruit flies, the effect was more complicated than in yeast or worms. Ibuprofen increased the flies’ average lifespan, but actually reduced the maximum lifespan in male flies.

    We’re definitely not at a stage where taking ibuprofen every day could be recommended as a way to extend your lifespan. While some people might think “what harm can it do?" and "it might do some good”, ibuprofen is not risk-free. As with most drugs, ibuprofen can cause side effects, including gastrointestinal bleeding.

     

    Where did the story come from?

    The study was carried out by researchers from the Buck Institute for Research on Aging, and universities in the US and Russia. It was funded by the US National Institutes of Health and National Science Foundation.

    The study was published in the peer-reviewed, open access journal PLOS Genetics.

    The newspapers’ headlines are unwarranted over-extrapolations of this animal and laboratory research. Most later clarified that the research was in yeast, worms and flies – but read in isolation, the headlines are misleading.

    This seems an irresponsible approach, given the potential harm that could result from people taking a cheap and readily-available drug unnecessarily.

     

    What kind of research was this?

    This was an animal and laboratory study looking at whether ibuprofen increases lifespan in flies, worms and yeast.

    The researchers say that ibuprofen has been associated with a reduction in the risk of some age-related problems such as Alzheimer’s disease and Parkinson’s disease. However, whether it also has an effect on lifespan is unknown.

    The organisms used in this study are often used in studies of lifespan, as their lives are short. This means that researchers can quickly find out if a chemical affects lifespan. If they find the same effect on lifespan in the multiple organisms tested, this suggests that the chemical is affecting a system that has been evolutionarily “conserved” across different organisms. This makes it more likely that the effect may also apply to other, untested, organisms.

    However, flies, worms and yeast are relatively simple organisms, and things that affect their lifespans may not have the same impact on more complex organisms such as mammals. For example, while a chemical might double lifespan in a yeast, even if it also has an effect on lifespan in mice, it would be unlikely to have as dramatic an effect.

    The researchers say that getting from chemicals that show promise in yeast and other organisms to drugs that are effective and safe in humans is a “significant hurdle”. For this reason, they wanted to look at a drug that was already used in humans, as they are already known to be safe enough for human use.

     

    What did the research involve?

    The researchers tested the effects of ibuprofen on one type of yeast, one type of microscopic worm, and fruit flies. In each case they exposed one group of yeast/worms/flies to ibuprofen and another group was not exposed (controls). They measured how long each group lived to see if it differed.

    For yeast and worms, exposing them to ibuprofen involved growing them in a solution containing the drug. For yeast, the study looked at how long they were able to keep dividing to produce new yeast cells – a standard measure of their “active” lifespan. For flies, this involved feeding them with a solution that included ibuprofen. The organisms were grown in standard conditions, to make sure that the only thing that differed between them was whether or not they received ibuprofen.

    The researchers then carried out a wide range of detailed experiments to determine how ibuprofen was having an effect.

     

    What were the basic results?

    The researchers found that yeast exposed to ibuprofen lived 17% longer on average than they did without it. Worms exposed to ibuprofen throughout their lives lived about 20 days, compared to about 18 days on average without ibuprofen. The researchers said that the levels of ibuprofen that extended the lifespan of worms and yeast were in the range of levels reached in people taking ibuprofen at typical doses.

    In female fruit flies, ibuprofen extended the average lifespan and also the maximum lifespan. In male fruit flies, ibuprofen extended the average lifespan but, oddly, reduced the maximum lifespan. This meant that the shorter-lived flies were living longer with ibuprofen, but the longest-lived flies were not living as long.

    The researchers found that ibuprofen seemed to be having its effect by reducing uptake of the amino acid tryptophan by cells.

     

    How did the researchers interpret the results?

    The researchers concluded that their results “identify a largely safe drug that extends lifespan across different kingdoms of life” and “implicate [tryptophan] import in aging”.

     

    Conclusion

    The current study has found that ibuprofen can extend lifespan in yeast, worms and flies.

    This does not guarantee that it will extend the lives of humans – or indeed other animals more complex than flies. Even if a chemical was to have an effect on mammals, it would be unlikely to be as great an effect as in the simpler organisms that have been tested.

    The results of the study themselves point to a more complicated story as organisms get more complex. While average lifespan was extended in all of the organisms, in male fruit flies (but not females) maximum lifespan was actually reduced with ibuprofen.

    Doubtless these findings will lead to more research, as ways to fight the ravages of ageing are among the “holy grails” of drug development. The researchers point out in the news that there is probably already data available from observational studies in humans that could be used to assess whether ibuprofen use is associated with increased lifespan.

    If you’re tempted to take a daily ibuprofen to extend your life because they’re cheap and readily available – don’t!

    Ibuprofen, while safe enough for human consumption, is not risk-free. As with most drugs it can cause side effects, including gastrointestinal bleeding. While the benefits are likely to outweigh the harms for people taking the drug in the short term for its intended uses (such as pain relief), this is not the case when taking the drug on a daily basis for an unproven, and potentially non-existent, benefit.

    Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

    Links To The Headlines

    Is Ibuprofen the key to a longer life? Study finds it may provide 12 extra years of good health. Mail Online, December 18 2014

    Taking ibuprofen every day could extend your life by up to 12 YEARS. Daily Mirror, December 18 2014

    Ibuprofen adds 12 years to life! Cheap painkillers can slow ageing and fight disease. Daily Express, December 19 2014

    Could ibuprofen be key to anti-ageing? Study finds painkiller extends life of flies and worms by equivalent of 12 human years. The Independent, December 19 2014

    Hangover cure may aid a longer life. The Daily Telegraph, December 19 2014

    Links To Science

    He C, et al. Enhanced Longevity by Ibuprofen, Conserved in Multiple Species, Occurs in Yeast through Inhibition of Tryptophan Import. PLOS Genetics. Published December 18 2014



  • Shift workers more likely to report poor health

    "Higher rates of obesity and ill-health have been found in shift workers than the general population," BBC News reports.

    These are the key findings of a survey into health trends among shift workers; defined as any working pattern outside of the normal fixed eight-hour working day (though start and finish times may vary).

    According to the survey (The Health Survey for England 2013), shift workers were more likely to report general ill-health, have a higher body mass index (BMI) and increased incidence of chronic diseases such as diabetes.

    The Health Survey for England 2013 also monitored other trends in the nation’s health, including people’s weight, smoking habits, fruit and vegetable consumption, and prescribing patterns for drugs (a story we covered earlier this month). 
     

    Who produced the data?

    The report was produced by the Health & Social Care Information Centre (HSCIC), the official provider of national health and social care statistics. The HSCIC was set up by the government in April 2013. Its role is to provide information on a range of issues concerning health for use by commissioners, analysts and clinicians in driving patient services.

    In the interests of transparency we should point out that the Behind the Headlines team, along with all NHS Choices staff, is employed by the HSCIC.

    The HSCIC produces an annual Health Survey for England that monitors important aspects of the population’s health.

     

    How was the data collected?

    The data comes from interviews with a representative sample of the population. Participants aged 16 years and over who were in employment were asked whether they worked in shifts either "most of the time", "occasionally" or "never". Those who answered either "most of the time" or "occasionally" were then asked which type of shift work they were doing. Shift work was defined in the question as "work outside the hours of 7am to 7pm in your (main) job".

    Participants were then grouped into shift workers (who reported that they did shift work "most of the time" or "occasionally") and non-shift workers.

    Comparisons between shift workers and non-shift workers across a range of health and lifestyle factors were age-standardised, so that any differences in age profile are taken into account in the comparisons.

    What were the key findings?

    • Men were more likely than women to report that they did shift work (33% of men and 22% of women).
    • Shift working was most prevalent in the 16-24 age group, and declined with age for both men and women. Almost half of men and over a third of women aged 16-24 did shift work compared with fewer than a third of men and a fifth of women aged 55 and over.
    • The prevalence of shift work varied significantly by household income, being highest in the lowest two income quintiles (42-43% among men, 27-28% among women, compared with 21% and 19% respectively in the highest income quintile). Similarly, the proportion of men and women in shift work was highest in the most deprived quintile compared with the least deprived.
    • Both men and women in shift work were more likely than non-shift workers to report fair or bad health.
    • Shift workers were more likely than non-shift workers to have a limiting longstanding illness; they were also more likely to have more than one longstanding illness.
    • Shift workers were more likely than non-shift workers to be obese. This is reflected in higher mean body mass index (BMI) measurements, higher proportions classified as obese, and greater proportions with a very high waist circumference.
    • Men and women in shift work were more likely than non shift workers to have diabetes (10% of both men and women in shift work, compared with 9% and 7% respectively of those not working shifts).
    • Current cigarette smoking prevalence was higher among shift workers than non-shift workers, with a larger difference among women than men. 28% of men in shift work currently smoked compared with 23% of men who did not do shift work. The equivalent figures for women were 26% and 15% respectively.
    • The proportion of both men and women who drank alcohol in the last year was slightly smaller among shift workers (84% of men, 81% of women) than among those who did not work shifts (88% and 83% respectively).
    • Daily fruit and vegetable consumption was lower among shift workers than non-shift workers. Men in shift work ate an average of 3.3 portions compared with 3.6 for non-shift workers. Among women the equivalent means were 3.6 and 3.8 respectively. Shift workers were also slightly less likely than non-shift workers to meet government recommendations of eating five or more portions per day.

     

    Why do shift workers tend to be less healthy?

    There are a number of potential underlying factors that may impact on health and wellbeing.

    Firstly, shift working can disrupt what are known as circadian rhythms, the internal "body clock". This can disrupt the normal workings of a hormone called melatonin. This disruption can lead to poor sleep and chronic fatigue.

    Persistent lack of good quality sleep has been linked to a range of chronic conditions such as obesity, depression, diabetes and heart disease.

    While the body can slowly adapt to the changes in working patterns, many shift workers are on rotating shifts and suddenly switching from a night to day shift leads to further disruptions.

    Rotating shift work can also disrupt the production of insulin, which may increase the risk of someone developing type 2 diabetes.

    There is also the fact that shift workers tend to be on the lower end of the socioeconomic scale. And there is evidence that people on lower incomes have an increased tendency to smoke, drink excessive amounts of alcohol and eat a poor diet. There is also the stress and worry associated with trying to make ends meet.

     

    What has previous research found?

    There has a been a range of studies linking shift work to a number of different adverse outcomes; which we have looked at previously in Behind the Headlines. These include claims that:

    The issue with all the studies is that due to the complex play of personal, environmental and socioeconomic factors, researchers were unable to prove a direct cause and effect link between shift work and the outcomes listed above; only an association.

    Still, there seems to be a consensus that while shift work may not be actively dangerous, it is certainly not an ideal arrangement for healthy living.

     

    So what can shift workers do?

    Well, ideally, find another job. But that is often easier said than done. Most of us don’t have the luxury of quitting a job if the hours don’t suit us unless we have another job lined up.

    That said, if you are unhappy with your current situation, it is worth spending a few hours every week signing up to job search sites. Along with commercial sites, the government also provides a service known as Universal Jobmatch.

    The Health and Safety Executive also offers some useful and practical advice for people working shift work. This includes:

    • take extra care if you drive to and from work as your concentration may be impaired; if possible it may be a better idea to use public transport
    • identify a suitable sleep schedule of at least seven hours a day, you may find it useful to keep a diary to assess what sleep times suit you best
    • try to create an environment that promotes good sleep, for example heavy curtains or an eye mask may help you sleep during the day
    • making changes to your diet to improve both alertness and digestion; smaller healthy snacks during your shift may be a better idea than one big meal
    • limit your use of stimulants such as caffeine or energy drinks as well as sedatives such as alcohol; while they may bring short-term benefit they are unlikely to be of help in the long term
    • try to get regular exercise – at least 30 minutes per day

    Read more Hints and tips for shift workers

    .

    Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

    Links To Science

    Shift workers 'sicker and fatter'. BBC News, December 15 2014

    Shift workers more likely to suffer from poor health, including diabetes and obesity. The Independent, December 15 2014



  • 'Electromagnetic smog' unlikely to harm humans

    The Daily Telegraph reports that “mobile phones are unlikely to harm human health”, adding to the ongoing, and often conflicting, coverage of the potential health impact of environmental exposure to what some commentators have called “electromagnetic smog”.

    This is a term used to refer to a mix of low-level magnetic fields that exist in the modern environment. This "smog" is not just generated by mobile phones, but also by Wi-Fi routers, tablets, laptops, power lines and cell towers. In the modern world, you are never far away from a magnetic field.

    Concerns regarding the impact of exposure to environmental magnetic fields (MFs) on human health have existed for decades. While observational studies have suggested that there is an association between such exposure and certain diseases, no studies have demonstrated a direct causal link. Part of the difficulty in determining whether there is a direct effect is the lack of an established mechanism of action by which magnetic fields could plausibly bring about changes in the biochemical processes that occur in the body.

    The most plausible mechanism of action is known as the radical pair mechanism. A "radical" is an atom or molecule that is chemically reactive due to the presence of an unpaired electron. Some biochemical processes produce brief radicals as an intermediate step in the longer process. Processes that involve, or are thought to involve, pairs of these radicals were used in this research.  

    This latest study investigated whether exposure to magnetic fields alters processes in a class of enzymes known or thought to involve radical pairs, which could potentially damage cells. The researchers found that these reactions were not sensitive to magnetic fields.

     

    Where did the story come from?

    The study was carried out by researchers from the University of Manchester and was funded by the EMF Biological Research Trust, in the UK.

    The study was published in the peer-reviewed Journal of the Royal Society  Interface.

    The research was reported well by the Daily Telegraph, which clearly stated that this was a lab-based study, and reported the need for further research to rule out other potential causal mechanisms.

     

    What kind of research was this?

    This was a lab-based study that systematically investigated the magnetic field sensitivity of a variety of enzymes. This research explored the impact of MFs in cells under lab conditions, to test the hypothesis that biological processes involving radical pairs are a plausible mechanism of action by which environmental MFs could affect biology.

    It is important to note that the study did not assess the direct impact of MFs on the development of human disease.

     

    What did the research involve?

    The researchers tested the effect of exposure to a range of magnetic fields (MFE) on chemical reactions involving a group of enzymes called flavin-dependent enzymes. These are responsible for a variety of essential biological processes, including energy production, DNA repair, regulating natural cell death, neural development and detoxification. Several radical pairs can temporarily occur during reactions initiated by these enzymes, and the researchers were interested in magnetically-induced changes in these reactions arising from MF sensitivity.

     

    What were the basic results?

    The researchers found no magnetic field effects in the various reactions studied. They say that a number of conditions must be met for a radical pair reaction to be sensitive to magnetic fields, and that these conditions do not appear to be widespread in biology.

     

    How did the researchers interpret the results?

    The researchers concluded that we “should reconsider the likelihood of magnetic sensitivity as a result of the radical pair mechanism in biology”. That is, mechanism of action thought to be most plausible in explaining the observed association between magnetic field exposure and human disease was not seen.

     

    Conclusion

    This study adds to the literature suggesting that environmental magnetic field exposure is unlikely to cause human disease. It's important to note, however, that this study did not examine disease states directly, but instead investigated a mechanism of action thought to be the most likely candidate to explain the observed link between MFs and certain medical conditions. The results of this study suggest that radical pair mechanism is not likely to be sensitive to magnetic fields.

    Further potential mechanisms of action will need to be studied before drawing firm conclusions on the risk (or lack thereof) presented by mobile phones, power lines and other sources of weak magnetic fields.

    The results of this study do not conflict with the most recent guidance from the UK Health Protection Agency, which states that “there is no known mechanism or clear experimental evidence” that explains the association between MF exposure and diseases such as childhood leukaemia or Alzheimer’s disease.

    Other agencies have released similar guidance on magnetic field exposure. In 2002, the International Agency for Research on Cancer (IARC) categorised extremely low-frequency magnetic fields as "possibly carcinogenic [i.e. cancer-causing] to humans". A later report from the same agency concluded that there is inadequate evidence to confirm the impact of these fields on human health.

    Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

    Links To The Headlines

    Mobile phones unlikely to harm human health, scientists find. The Daily Telegraph, December 10 2014

    Links To Science

    Messiha HL, Wongnate T, Chaiyen P, et al. Magnetic field effects as a result of the radical pair mechanism are unlikely in redox enzymes. Journal of the Royal Society - Interface. Published online December 10 2014 



  • Fathers-to-be experience hormone changes

    “Men suffer pregnancy symptoms too: Fluctuating hormones make fathers-to-be … more caring,” the Mail Online reports. A small US study found evidence of changes in hormonal levels that may make fathers-to-be more able to cope with the demands of fatherhood.

    The story comes from a study that looked at whether expectant fathers and their partners experience any changes in their hormone levels during pregnancy. It found that, as expected, women experienced a large increase in four hormones associated with pregnancy. Their male partners also experienced small changes in the hormones testosterone and oestradiol.

    The researchers, as well as the media, speculate that these small changes in hormone levels could lead to men becoming less aggressive, less interested in sex, and more caring. Though whether such changes are linked to subsequent changes in their behaviour is unproven.

     

    Where did the story come from?

    The study was carried out by researchers from the University of Michigan. There is no information about external funding.

    The study was published in the peer-reviewed American Journal of Human Biology.

    The Mail Online overstated the results of the study, claiming that “men’s hormones go into a spin in the months before becoming a parent” and that this helps them prepare to bond with their babies – and stops them from straying. This is all speculation. The study did not look at men’s behaviour in the months before birth, only at their hormone levels. It is also misleading in that it claims that the men experienced “pregnancy symptoms”, when none were reported in the study.

     

    What kind of research was this?

    This study measured changes in levels of certain hormones in 29 first-time expectant couples at four points throughout the prenatal period. The authors point out that expectant mothers experience large increases in hormones such as testosterone, cortisol, oestradiol and progesterone. They say that these hormones are implicated in the neuroendocrine pathways (a complex connection of nerves that both respond to and also produce hormones) that affect maternal behaviour and may have long-term implications for women and their families.

    They say that far less is known about changes in the hormone levels of expectant fathers, even though their behaviour may be influenced by the same neuroendocrine pathway. In addition, it is not known if there is any correlation between couples in changes in hormone levels.

    The researchers focused on four hormones, which have large prenatal changes in women and which they say have important implications for parental behaviour. These are:

    • Testosterone – higher levels are associated with aggression and lower levels with parental care. Women’s testosterone levels increase during pregnancy and decline after birth.
    • Cortisol – associated with stress and challenges. In women, cortisol increases through pregnancy and declines after birth.
    • Oestradiol – associated with caregiving and bonding and thought to be important for maternal attachment. In women it increases during pregnancy and drops after birth.
    • Progesterone – associated with social closeness and maternal behaviour. In pregnant women it increases during pregnancy and drops after birth.

     

    What did the research involve?

    The researchers measured changes in all four hormones in 29 expectant couples. The couples, who were recruited online and in print, were paid $50 per session for participating. They had to be between 18 and 45, living together, expecting their first child and within the first two trimesters of pregnancy. Smokers, those with medical conditions that could influence hormone levels, and those taking hormone altering medications were excluded.

    The couples’ hormone levels were assessed up to four times throughout the prenatal period, at approximately weeks 12, 20, 28 and 36 of pregnancy. Each couple came to the laboratory together and had their hormone levels measured at the same time and on the same day of the week. They provided two saliva samples on each visit. These were frozen until being tested for levels of testosterone, cortisol, oestradiol and progesterone, using commercially available kits.

    The researchers analysed the results using standard statistical methods.

     

    What were the basic results?

    • As expected, women showed large prenatal increases in all four hormones.
    • Men showed significant but small prenatal declines in testosterone and oestradiol, but there were no detectable changes in men’s cortisol or progesterone. 

     

    How did the researchers interpret the results?

    The researchers say their study is the first to demonstrate prenatal testosterone changes in expectant fathers.

    They say the findings on testosterone and oestradiol support the idea that the same hormones may be involved in maternal and paternal care.

    They say their findings provide some support for the theory that similar neuroendocrine pathways support both maternal and paternal behaviour.

     

    Conclusion

    This is an interesting study, but it was very small and, as the authors point out, found only limited evidence of small hormone changes among expectant fathers, so it is difficult to draw any conclusions from it.

    One important limitation was the lack of a comparison group of non-expectant couples. This means the authors cannot say whether any hormone changes among the men occurred as a result of expectant fatherhood or other causes.

    Nor did the researchers assess the men’s hormones before conception or postnatally, so they could not determine how men’s hormone levels change during the entire transition to parenthood.

    In women, changes in hormone levels are vital to maintain the pregnancy and are also thought to affect maternal feelings and behaviour. This study does not provide conclusive results on the changes in hormone levels that occur in expectant fathers or whether these might be linked to changes in behaviour.

    Becoming a dad for the first time can be an overwhelming and somewhat frightening experience, though most men quickly learn and adapt. The human race wouldn’t be here if that wasn’t the case.

    Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on Twitter. Join the Healthy Evidence forum.

    Links To The Headlines

    Men suffer pregnancy symptoms too: Fluctuating hormones make fathers-to-be less aggressive and more caring. Mail Online, December 16 2014

    Links To Science

    Edelstein RD, Wardecker BM, Chopik WJ, et al. Prenatal hormones in first-time expectant parents: Longitudinal changes and within-couple correlations. American Journal of Human Biology. Published online December 15 2014