Tag Archives: science journalism

Does breastfeeding ‘cut leukaemia risk’? No good evidence

Occasionally my work and home life collide – I read some stories in the press about research claiming breastfeeding for six months or more could cut the risk of childhood acute leukaemia. The research was shaky, so I wrote this for the Leukaemia & Lymphoma Research blog (where I work).


Reports coming out in the media (such as Express, Mail, Mirror) are suggesting that breastfeeding for six months or more can lower the child’s risk of developing leukaemia. But where did these findings come from and how reliable are they?

In this post, we take a look at the research that led to these reports, and suggest that the results are not very robust, the conclusions are overstated and the claims likely to cause unnecessary alarm.

Greater than the sum of its parts?

The new research, published in the peer-reviewed journal JAMA Pediatrics, combines many previous studies that looked at whether children who had been breastfed (and for how long) went on to develop childhood leukaemia. The studies in the new analysis were a mixture of size and quality, so on their own couldn’t lead to any definitive conclusions. But when put together and re-analysed – known as a meta-analysis – it is intended to boost the power of the findings.

The new study includes 18 studies that met a certain quality threshold. The researchers, based at University of Haifa in Israel, report that children who had been breastfed for six months or more had up to a 19% lower risk of developing leukaemia than children who had never been breastfed or had been breastfed for under six months.

From this, they conclude this is sufficient evidence of a protective effect to further promote the health benefits of breastfeeding and encourage greater uptake amongst new mothers.

But we are not persuaded these claims truly stack up.

Correlation is not causation

The strength of a meta-analysis is that it tries to make sense of all the best research on the subject. But all of the studies within the new analysis looked at the association between breastfeeding and leukaemia, and therefore cannot tell you about true causes. Other background factors that affect both the likelihood of breastfeeding and leukaemia risk could have been missed or overlooked.

For example, parental affluence may affect the decision to breastfeed. But affluence will also affect a host of behaviours, like attendance at nursery, exposure to infections, decision to vaccinate, time of weaning, and many, many more. We don’t know for sure what factors do influence leukaemia risk – and parental affluence is just given as an example here merely to illustrate the complexity of background factors – but simply linking breastfeeding and leukaemia risk without consideration of other potential influencing factors is far too premature.

Experts who conduct these types of studies are well aware of these issues and always attempt to account for background factors, like socio-economics, lifestyle, gender, ethnicity, and so on, but it’s always hard to eliminate them altogether. Nevertheless, we were alarmed when we spoke to our statistical experts who noticed that the meta-analysis unusually relies on crude data that did not appropriately account for background factors.

They suggested that the authors’ relative inexperience with this type of analysis has led to a number of flaws.

Hidden biases

The experts we spoke to pointed out a gross error in the data – one dataset, that had been used in two different publications, is included twice. This could distort the statistical robustness or the size of any effect, and could be serious enough to consider a correction or withdrawal of the paper.

There are also a few ways these data could have been skewed to give wrong or exaggerated results. One is a bias in those participating in these studies. Many were based on phoning mothers at home or by a self-administered questionnaire. This introduces a potential participation bias, where the people surveyed and who agreed to take part were not representative of the population as a whole. This may mean certain groups, such as more educated or time-rich parents, were overrepresented in the comparison group (children who didn’t get leukaemia), suggesting a larger proportion of children who did not get leukaemia were also breastfed.

Almost all of the studies asked mothers or parents to remember the duration of breastfeeding, sometimes many years later. This introduces a possible recall bias, where parents may not have accurately remembered what they did or their responses were affected by knowing that their child had had leukaemia. And because childhood acute leukaemia is thankfully relatively rare – only three to four children in every 100,000 are affected each year in the UK – the small numbers could have inflated these biases.

It would be far better to recruit a large random sample of people, collect data in real-time, and then look at whether children went on to develop leukaemia. This is more costly and time-consuming, but it would help diminish some of these potential biases because the particpants and research questions would be defined up-front. 

The authors acknowledge these limitations in their discussion section of their paper, which is why we were surprised by the strength and certainty of their claims in the conclusions section.

What would this mean in the real world anyway?

There is some evidence that links proper immune system development to a reduced likelihood of developing leukaemia as a child and certain genetic faults present at birth can raise the risk substantially, but we are still far from truly understanding all the many different factors at play. It is an important area to be able to understand who is most at risk and what factors can alter their likelihood of developing this disease if we are to prevent some of these cases, but we are not convinced that this new analysis provides strong evidence for a significant role of breastfeeding.

We should also stress that because of the relative rarity of childhood leukaemia, even if the authors’ claims were true, it would still affect only a tiny number of children. And it would still only affect children who are already at risk because of key genetic faults that occur in the womb.

There is a lot of pressure on new mothers, some mothers cannot breastfeed and many factors can affect how long new mothers can breastfeed for. Parents of children who develop leukaemia can also feel a lot of guilt, even though we know some children will unfortunately get the disease whether they’ve been breastfed or not.

Stories based on problematic research do not help anyone.

  • For some expert opinion, including our Research Director and Prof Eve Roman (an epidemiologist whose work we support), see the Science Media Centre
  • Reference: Amitay & Keinan-Boker (2015). Breastfeeding and Childhood Leukemia Incidence A Meta-analysis and Systematic Review. JAMA Pediatr. 2015;169(6):e151025. doi:10.1001/jamapediatrics.2015.1025

What can Mickey Mouse tell us about a growing child?

At a party some time ago, I got talking to a biology graduate friend about comparative psychology, as a geek tends to do at social occasions.

Comparative psychology is the study of animal behaviour and mental processing across different species. By doing this, it gives us clues to the function, benefit and development of a particular behaviour. Understanding the similarities and differences amongst different animals in this way can shed light on evolutionary relationships.

The topic came up because our friends were revelling in how cute baby animals are. If you don’t believe me, just look at these cherry-picked examples:

Author: George Estreich

Baby monkey

Author: Ville Miettinen

Baby fur seal

Author: Matt Stanford

Baby elephant

Author: uaeveggies

Baby duck

What’s striking is how wildly different baby animals can provoke the same “aaah” reflex. Baby primates and baby birds, separated from each other and from us by millions of years of evolution, can elicit the same cooing reaction. And size doesn’t seem to matter − a 100kg baby elephant can bring as much infatuation as a 5kg baby seal.

In other words, there’s something about being a baby, and not just a miniature version of an adult.

This immediately reminded me of an image drawn by Nobel prize-winning animal behaviourist, Konrad Lorenz. It shows how juvenile proportions are conserved across different animal groups, and goes someway to explain why we react to many baby animals as we do.

From Studies in Animal and Human Behavior, vol. II, by Konrad Lorenz, 1971. Methuen & Co. Ltd.

From Studies in Animal and Human Behavior, vol. II, by Konrad Lorenz, 1971. Methuen & Co. Ltd.

I think I first saw this image in a book by renowned evolutionary biology, Steven Jay Gould*. He also included it in a wonderful essay called Homage to Mickey Mouse. In this article, Gould explains that over time, to chime with his softening of character, Mickey’s appearance became increasingly juvenile.

via Zoonomian

A large head relative to body, short legs and feet, bulbous cranium and big eyes, as seen in a latter-day Mickey, look like the hallmarks of a juvenile. And Mickey travelled this path to juvenility in reverse − a phenomenon known as ‘neoteny‘.

An illustration’s fine, but to truly demonstrate this scientifically, Gould actually measured the relative changes in Mickey’s physical attributes and plotted the results on a graph. The result, as was Gould’s wont, is an engaging fusion of science and creative writing − do read it. (On reading, I did wonder whether Mickey’s appearance was altered to match a desired change in character, or the other way round.)

The key to all this is that the proportions of a baby’s face, as compared to an adult, are similar across many different animals. This set of features triggers what Lorenz described as an ‘innate releasing mechanism’ − an automatic and consistent reaction to an important behavioural cue. It makes sense that a hard-wired mechanism has evolved to trigger an immediate sense of attachment when confronted with a baby’s face − it will promote parental care, which has clear evolutionary advantages.

But that same hard-wired mechanism also appears to fire when we see similar baby-ish proportions in other animals. It’s an inappropriate response in an evolutionary sense, but it’s better to be harmlessly fooled by a baby bird than to not feel instinctively drawn to our own baby.

What’s fascinating is that, in some cases at least, these ‘releasers’ are reduced to very specific features. A classic example was demonstrated by Lorenz’s Nobel prize-winning collaborator, Niko Tinbergen, using three-spined sticklebacks. A male stickleback will attack another male, as identified by a red belly, but will also attack any object with a red spot − fish-shaped or otherwise. A stickleback-shaped object without a red belly is suitably ignored. Like a red rag to a stickleback, it’s better to be safe than sorry.

Babies do something similar in reaction to stylised smiley faces − a circle for a head, two dots for eyes, and a curved line for a mouth is enough to grab a baby’s attention. This stays with us into adulthood and is, for better or worse, the reason why emoticons are so enduring. So, similar to a stickleback reacting solely to a red spot, it seems it’s not a whole baby’s face we respond to, just a certain set of features.

Yes, your baby’s cute because of this graph:

“At an early stage in his evolution, Mickey had a smaller head, cranial vault, and eyes. He evolved toward the characteristics of his young nephew Morty (connected to Mickey by a dotted line).” By Steven Jay Gould

* I should dedicate this post to the late, great Derek Yalden, who taught me zoology at The University of Manchester and told me to read The Panda’s Thumb.

(As an addendum: none of this makes animals we find cute any more ‘worthwhile’ than “ugly” animals. Check out the recent campaign by the “Ugly Animal Preservation Society“.)

Parenting science: 12 top stories of 2012

It’s that time of year when we’re flooded with ‘best of’ lists, so allow me to jump on the bandwagon. 2012 has been a great year for science – the discovery of the Higgs Boson, the landing of Curiosity rover on Mars, and the ‘encyclopaedia of DNA’ that has given us the deepest insights into the human genome.

Here, I’ve picked out some of the stories that might interest parents, covering areas such as child learning and development, reproductive technologies, embryology, genetics, and even a bit of public policy thrown in. I’m sure I’ve missed some interesting ones too, so please add yours in the comments!

Mouse eggs created from stem cells for the first time (New Scientist)

Once a fully functional body cell develops from a ‘parent’ stem cell, it’s thought there is no going back to the previous state. A team of scientists in Japan, however, used a cocktail of signalling molecules to reprogram skin cells to become immature egg cells in mice (they had already done this to create sperm cells). What’s more, these cells could be fertilised and, in some cases, led to healthy mouse pups. This was a stunning feat of biological engineering that will help in the study of mammalian development and also hold promise in treatment of infertility. In a related story, controversy over whether biology textbooks need to be re-written took a turn when more convincing evidence was published that the number of eggs in a female isn’t fixed for her lifetime but can instead by replenished from a stem cell stock.

‘Chimera’ monkeys created in lab by combining several embryos into one (The Guardian)

The headline is pretty self-explanatory and the article itself is a fascinating read, so I won’t re-invent Ian Sample’s superbly crafted wheel. So if you want to know more about the controversial technique of creating normal, healthy monkeys with cells from more than one embryo and why it might benefit stem cell therapies, go read it! This may not be as bizarre and ‘unnatural’ as it first sounds, though, as we may all be walking chimeras and carry cells from siblings, aunts and uncles.

Genome Sequencing for Foetuses (Wired Science)

Being able to test foetuses for genetic faults that increase the risk of a serious disease, such as Down’s syndrome and blood or nervous system disorders, is hugely important. This is currently done mostly by invasive techniques such as taking samples of the placental tissue or amniotic fluid. This study, however, showed that it’s possible to work out the foetus’ genetic make-up by piecing together tiny fragments of DNA floating around in the mother’s blood. The ease of such a test would, of course, raise ethical issues about what is appropriate to screen for and what counselling parents would need, as well as requiring a firm and clear communication of risk.

DNA-swap technology almost ready for fertility clinic (Nature News)

Mitochondria are little energy powerhouses within most of our cells and they contain a small amount of their own DNA that is inherited wholly from the mother. A range of devastating diseases, that can affect the brain, liver, muscle and many other organs, are caused by defects in this mitochondrial DNA. A group of US researchers showed it was able to swap the mitochondria in a mother’s egg with one from a healthy donor to produce a normal looking embryo free from the mitochondrial genetic faults (restrictions on this technology would not allow a live birth). You can read about how the scientists actually did this in David Cyranoski’s article. And I would add that, contrary to some scare stories, these would not be ‘3 parent babies’ – mitochondrial DNA contains only 37 genes (involved in protein synthesis and biochemical reactions that make up respiration) compared with the many thousands of genes coded for by the DNA in the nuclei of our cells.

Babies are born dirty, with a gutful of bacteria (New Scientist)

Earlier this year I blogged about the “The microworld that lives inside you” and how the microorganisms that outnumber our own cells 10:1 are first transmitted from mum as a baby is born. A study by Spanish scientists, suggested that this isn’t the whole story. By studying the “meconium” – the baby’s first poo that is made up of materials ingested during the time in the womb – they detected two types of well developed bacteria. We don’t know for sure, but these were probably passed from the mother through the placenta. Our so-called “microbiome” is really important, because it influences our digestion, immune system, risk of disease, and maybe even our personalities.

Childhood stimulation key to brain development, study finds (The Guardian)

A US study provided more evidence that a sensitive period of learning and development exists early in childhood. They surveyed children from when they were four years old, recording details such as the number of books and the types of toys they had, to measure the amount of mental stimulation to which they were exposed. They also scanned the brains of the same children when they were between 17 and 19. As Alok Jha explains: “…the more mental stimulation a child gets around the age of four, the more developed the parts of their brains dedicated to language and cognition will be in the decades ahead.” Of course, this was an observational study and so limits the strength of the conclusions about whether the types of toys really caused brain developments, but the way the researchers tracked the same children over many years and the factors they took into account (parental nurturance had little effect, for example), was particularly impressive. Another cautionary note: the results were presented at a scientific conference and, as far as I know, have not appeared in a scientific journal, which means it won’t have yet been properly quality assessed by experts.

Golden ratio discovered in uterus (The Guardian)

At the risk of straying into mysticism, this was a nevertheless alluring report of a Belgian gynaecologist’s claim that the uterus represents an aesthetically pleasing “golden ratio”. This ratio is derived from something called the “Fibonacci sequence”, which is a sequence of numbers starting 0,1,… where every subsequent number is the sum of the previous two (so: 0, 1, 1, 2 , 3, 5, 8, 13, 21,…). The ratio between pairs of number in the sequence (divide one by the other) ends up being 1.618, which is the “golden ratio”. As Alex Bellos explains, its devotees believe it expresses aesthetic perfection and is found wherever there is beauty. According to Dr Verguts, when women are between the ages of 16 and 20 and at their most fertile, the ratio of uterine length to width is 1.6, spookily close to the “golden ratio”.

What happens to women denied abortions? This is the first scientific study to find out (io9)

Another set of results presented at a scientific conference, rather than in a scientific journal, but that is worth noting nonetheless. Annalee Newitz cites a Facebook post written by the lead researchers of a study that followed up women who had sought abortions at different abortion clinics in the US: “We have found that there are no mental health consequences of abortion compared to carrying an unwanted pregnancy to term. There are other interesting findings: even later abortion is safer than childbirth and women who carried an unwanted pregnancy to term are three times more likely than women who receive an abortion to be below the poverty level two years later.” Newitz further emphasises the preliminary results: “When a woman is denied the abortion she wants, she is statistically more likely to wind up unemployed, on public assistance, and below the poverty line.” If these findings turn out to be valid when further quality checks are carried out, they could help shape the debate on abortion policies and the state support a women seeking an abortion receives.

Boys and girls may be entering puberty younger (New York Times and The Guardian)

A study on the timing of puberty in boys by the American Academy of Pediatrics complements an earlier study on girls, which both hinted that puberty is, on average, starting gradually earlier in both sexes. Current estimates, at least for US children, are that the average age of puberty onset is around 9 years in black boys and girls and around 10 years in white boys and girls (although full sexual maturity may happen later than this). No one, as yet, knows why, but speculations include diet, changes in physical activity, improvements in healthcare, and chemicals present in the environment that affect our hormones.

Fathers bequeath more mutations as they age (Nature News)

A Swedish study concluded that a father passes on more genetic mistakes to their children than do mothers, and the older the man, the more mutations he is likely to pass on. This is most probably explained by the fact that sperm are generated from dividing ‘precursor’ cells throughout a man’s life and this cell division becomes less precise with age. Most inherited mutations won’t lead to any problems for the child, but the occasional one may increase the risk of a genetic disease like autism or schizophrenia. Taken together with rising average age of fatherhood, does this help explain, at least in some part, why autism rates are rising? (It could, but awareness and diagnostic changes are also likely to be at play). It’s not definitive and it shouldn’t scare older would-be fathers, but it may help in better informed decision-making.

An HPV Vaccine Myth Debunked (New York Times)

One of the arguments opposing vaccinating children against the Human Papilloma Virus (HPV), which can cause warts and cancer, is that in the minds of the young girls it frees them up to be sexually more promiscuous. Studying long-term medical data from girls in Atlanta, USA, however, showed no difference between vaccinated and non-vaccinated girls in pregnancies, sexually transmitted diseases, testing for sexually transmitted diseases, or contraceptive counselling. The article finishes by saying: “As one expert said, parents should think of the vaccine as they would a bicycle helmet; it is protection, not an invitation to risky behavior.”

Hungry mothers give birth to more daughters (Nature News)

Another eye-catching story was the report that during the Chinese Great Leap Forward famine, the proportion of boys being born dropped (from 109 boys for every 100 girls to 104 boys for every 100 girls). This sets up the tantalising possibility that sex ratios are adjusted in response to environmental conditions such as nourishment, a situation already known in deer where undernourished males tend to have fewer offspring than undernourished females (although in humans other factors like psychological and physical stress could be at play).

A final story that caught my eye was the latest results from the Avon Longitudinal Study of Parents and Children (ALSPAC), also known as the Children of the 90s, which probably warrants a blog post in itself. Nature News covered it and The Guardian’s sublime Science Weekly podcast featured it too (after 26:10). My favourite bit was how they collected the children’s milk teeth: “We had to negotiate for those. They are worth money to children, after all. In the end, we only got the milk teeth when we presented each boy and girl with an official Alspac form, signed by the tooth fairy.”

How sweet!

Telly addicts: alarm over kids’ TV viewing habits

There was a flutter of activity across Twitter and blogs the other day, in response to some reports that suggested kids’ increasing TV viewing was having a detrimental effect on mental health. According to the reports, TV viewing should be limited for children even into their teens and banned altogether for under-threes. The issues highlighted here will be familiar to detractors of Bad Science and Bad Reporting, but I wanted to record some thoughts for posterity.

I first saw the story in The Guardian and it was also picked up by BBC News, The Independent, The Telegraph, Daily Mail, Metro and many other outlets. Whilst it’s an interesting and worthwhile area of study, the paper published in the journal Archives Of Disease In Childhood and the subsequent press statements, had a few problems that undermine the stark headlines.

The paper was not an original research paper, but an opinion piece that looked back at some previous research. The chief agitator in this is Aric Sigman, a psychologist whose method of ‘cherry-picking’ evidence Ben Goldacre has had much to say about in the past. ‘Cherry-picking’ is essentially picking the bits of evidence that support a particular claim, whilst ignoring other evidence that doesn’t. As Goldacre points out, a better way to analyse previous research is to perform a ‘systematic review‘. These reviews say exactly how the literature was searched and compiled, which means it is more free from bias and allows others to reproduce it.

As for this specific case, Pete Etchells at SciLogs does a good job at highlighting the problems with the selective nature of the analysis and why it’s important to understand the cause of something before issuing guidance on fixes. I worry that many developmental outcomes – such as empathy, attention, educational performance – are lumped in under the banner of ‘mental health’, but that is probably for someone more qualified to comment on. Professor Dorothy Bishop‘s remarks in the Guardian article are salient too – if Sigman’s concerns are to do with kids just sitting for long periods, you shouldn’t advocate reading books for too long.

My first thought on reading the reports was that the conclusions seem to be based entirely on correlative studies, so it’s hard to determine cause-and-effect. What if children who watch more TV are also more likely to have inattentive parents? You may still see an association between more TV watching and developmental problems if these are both caused in some way by inattentive parenting, but enforcing a reduction in TV time wouldn’t do anything – getting parents to interact more at other times would have the most effect. (For the record, this is just an example of ‘correlation does not imply causation’ and I’m not suggesting this is supported by the evidence!)

On a more general but related point, there is a real problem with defining ‘screen time’, because you’re essentially describing a medium and not an activity. The Mind Hacks blog (written by KCL psychologist Vaughan Bell and Sheffield University psychology lecturer Tom Stafford) has written about this in relation to internet use. Bell has also written about how there have been worries throughout modern history over new technology. Even ‘education’ was once considered a risk to mental health.

As for TV, there are clearly different types of programmes kids can watch – some are aimed at learning and education, some are musical and participatory, some are interactive, and so on. And there are also different contexts in which to watch TV – alone, with parents talking things through, in the background whilst doing other things, etc. Understanding whether different types of TV interaction have different effects or whether other factors in the child’s environment tend to lead to a particular sort of behaviour, are critical in getting to the root of the issue.

The evidence just isn’t strong or reliable enough to make the sort of alarmist claims Sigman has made. And this is why it is again so disappointing to see the same blanket coverage across much of the press, with little in the way of a proper critique (Prof Bishop’s comments aside). It was once again left to bloggers and commentators on social media to provide a more discerning look at the issues.

I want to emphasise that I’m not dismissing these issues, and there may well be problems caused by excessive use – however that’s defined – of certain types of ‘screen time’ (as Etchells notes too). But it’s important to know what you’re measuring and understand the nuances. It is also crucial to have proper evidence before issuing supposed evidence-based guidance.

The microworld that lives in you

From a pod near you

I love a podcast. Episodes of audio goodness are delivered daily or weekly to my MP3 player, ready to keep me company on my long commute. I subscribe to podgrams dealing in current affairs, football, history and comedy.

But the overwhelming amount of disk space is taken up by science. Scientific news, scientific scepticism, scientific ideas, science in culture and scientific history. Even science comedy. Science science science.

Sometimes issues related to pregnancy and childbirth, childhood and parenting crop up, which as a science-minded parent is right up my street. And, I hope, right up other people’s streets too.

Here are some nuggets with which to start.

Ed Yong on BBC Radio 4’s Four Thought | 19 Oct 2011

Science writer Ed Yong describes his fascination with the human ‘microbiome’ – the bloom of microbes that each of us house in and on our body. The cells of bacteria, fungi and other microorganisms actually outnumber the cells of the human host by 10 to 1, and their genes by 100 to 1. Are we humans hosting a microbial community or a superorganism in which human cells are simply partners?

We can’t function as we do without these microbes. They help to digest complex foods like carbohydrates, metabolise drugs and toxins, interact with our immune system, and affect energy balance. The types and numbers of microbes within each of us are different and can depend on diet, environment and behaviour. The microbiome may have even played a part in shaping our evolution. They have such an important role that the microbiome has been called the ‘forgotten organ’ or the ‘second genome’. How, then, would you define what is ‘us’ – is it any cell that contains the same DNA as when we were an embryo, or are the constantly interacting microorganisms that are vital to our survival ‘part of us’.

What’s really interesting, at least from someone interested in child development, is how we gain this microworld. As Ed explains in the audio clip, we develop in the sterile environment of our mother’s womb*. The first gift from our mum is a smattering of microorganisms, but this depends on how we are born. A baby born of a vaginal birth is delivered their birthday presents as they travel through the vaginal canal and slides past (brace yourselves) the mother’s anus. The makeup of bacteria in vagina of pregnant women is actually quite different from that in non-pregnant women. A particular bacterium, usually found in the gut where it helps digest milk, becomes far more abundant in the vagina during pregnancy, which may give the baby a healthy coating as it is born.

Babies born of a caesarian section, however, do not have this close encounter and instead pick up a different spectrum of bugs that more closely resemble the ones found on skin. It can then take a while for the full complement of gut bacteria to establish.

The community expands and becomes more varied as the child interacts with its surroundings. Breast milk has been found to contain up to 600 species of bacteria, which furnish the babies gut and hinder the growth of any harmful nasties. Babies are then ready to take in more complex foods. This in turn fosters a richer microsociety and the mutual relationship continues. Environmental contaminants and toxins can perturbe the microbial community, which has been suggested (though not proven) to contribute to type II diabetes, cardiovascular disease or obesity.

Kerri Smith on Nature Podcast | 23 August 2012

Kerri Smith on the Nature Podcast reports on recent research that shows how antibiotics, at least in mice, can affect the gut bacteria composition and, consequently, the amount of body fat. The antibiotics seem to spur the bacteria into producing more fatty acids, which are converted by the human host into fatty tissue. Listen from 05:45 – 11:35 to hear a discussion with one of the researchers on the study of antibiotics in early life and the possible link to obesity.

And another fascinating potential of our microbiome is discussed by Chris Smith on The Naked Scientists podcast. Listen from 16:30 – 20:55 to hear Dr Marcello Riggio talk about how certain bacteria can promote oral health (good!) but also lead to bad breath or tooth decay (bad). Skip to 21:00 to hear a debate with Prof Gareth Morgan on whether probiotics – beneficial bacteria supplemented in the diet – may help to prevent/treat allergies and gut infections by interacting with the host’s immune system (ends 26:30). This idea is, however, not fully supported by the current evidence: results are variable and inconsistent (see The Cochrane Library reviews on allergies, eczema, colitis and diarrhoea).

Chris Smith on The Naked Scientists | 5th Sep 2011

Click to listen to: The_Naked_Scientists_in_Africa

And, finally, an even more fascinating potential of our microbiome is discussed by Mo Costandi in his Neurophilosophy blog. The bacteria in our guts may have the ability to affect brain development and mood.

For more on the wonder of the microbiome, read Ed Yong’s excellent blog post and Carl Zimmer’s article in the NY Times.

*or, maybe not.


Is breastfeeding all it’s cracked up to be?

Zoe Williams wrote an intriguing article in The Guardian that challenged some widely held assumptions and beliefs about the benefits of breastfeeding (‘The backlash against breastfeeding’). It did, as you might imagine, generate strong reactions from those who vehemently espouse that “breast is best”. It was written on the back of a recent front cover of Time magazine that caused an even greater furore (‘Are you mom enough’), which championed a form of ‘attachment parenting’ that encouraged breastfeeding until the child is well over one year old.

I did feel that Zoe Williams’ article raised some interesting points, some of which I wanted to address here.

But I also had the strong suspicion that the claims made for [breastfeeding’s] benefits – the higher IQ, the protection against obesity, the superior bonding, the warding off of disease both now and for ever, both for baby and for mother – were mostly bogus. A lot of the reasoning seemed syllogistic (babies born into low-income families end up fatter; low-income mothers breastfeed less than high-income mothers; therefore breastfeeding prevents obesity) or frankly lame.

This relates to the concept I’ve written about before, that correlation does not imply causation. As she quotes Joan B Wolf later in the article: “Breastfeeding cannot be distinguished from the decision to breastfeed, which could represent a more comprehensive commitment to healthy living.”  

While this is true, that is not to say that the researchers who conduct these types of observational studies are not aware of this limitation. It is hard to do interventionist, controlled studies, as you would do in a lab or in randomised controlled trials to test a new medicine. Imagine randomly assigning new mothers to one of two groups – breastfeeding or formula-feeding – and getting them to stick to this regimen so that you can measure the outcomes of the children. Not likely, which is why such interventionist studies have been limited (1 & 2).

So researchers work with the tools available to them. They try to include appropriate comparator groups and make statistical adjustments to account for potential confounding variables. Not perfect by any stretch, but the best available methods.

I knew a lot of mothers who formula fed; they didn’t seem to love their babies less.

Ignoring the submission to anecdote, which is a mortal sin to evidence-based thinkers, a more worthwhile point to address is an argument I’ve often heard that goes approximately: “Well, they say breastfeeding is best, but I formula-fed and my child turned out alright”.

There are two key flaws in this reasoning. One is that by advocating breastfeeding, it is implying that formula-feeding is bad. No. It’s just there’s less chance that any outcomes associated with breastfeeding will also be seen with formula-feeding. The second misconception is that there’s a complete separation, or dichotomy, between the two groups. But here we’re comparing averages of large study groups – there will be huge amounts of variability around the averages and a lot of overlap, and only the right statistical analyses can reveal any true differences.

Put simply, there will be mothers of formula-fed babies who form strong attachments (to carry on the example in the article) and mothers of breastfed babies who do not.

By analogy, there will be some people that do all the ‘right’ things – not smoke, eat healthily, exercise, apply sun cream – who will get cancer and there will those who smoke 40-a-day and drink to excess who do not. It doesn’t disprove the link, it’s all about stacking the odds in your favour.

(I should clarify that the evidence I’ve seen for superior bonding associated with breastfeeding is somewhat weak, but I referred to it here to address a more general point about the common use anecdotal evidence).

This struck me as a bizarre place to have arrived at; where even to talk about the evidence behind the benefits of one type of infant feeding over another is heretical.

Absolutely correct. We should constantly gather and scrutinise data, and if strong enough evidence emerges that contradicts our prior assertions, then we should be prepared to change our minds. I applaud the fact that this article was written, even if there are bits I wouldn’t necessarily or wholeheartedly go along with, as we should always be ‘talking about the evidence’.

The questioning of the orthodoxy is taken as a direct attack on babies.

[Charlotte Faircloth, sociologist]: “… Everything has got very heated, and very moralised. How you feed your kids is no longer a personal decision. There’s this idea that you can breastfeed your way out of poverty, or if you don’t breastfeed your kid’s going to be fat or have a low IQ…” She pauses. “It’s all got a bit out of hand.”

Williams is right that some breastfeeding advocates are evangelical and overly ideological about breast milk, to the point that some mothers feel over-bearing pressure to breastfeed. As Charlotte Fairclough is quoted, it’s a personal decision. Fairclough also touches on my earlier point that there’s no binary distinction in the outcomes of children who are breastfed and those who are not – breastfeeding doesn’t determine the outcome but may make it more probable (and, if it does, it will certainly still only be one factor amongst many).

Williams then quotes French feminist Elisabeth Badinter:

“when it’s recommended that you breastfeed your child for one year – six months exclusively, with nothing else, day and night, on demand – there are obviously consequences for a couple.”

“There are women for whom breastfeeding is a true pleasure. It’s very good for them and it’s very good for the baby. But to breastfeed a baby if the mother herself doesn’t like it? It’s a catastrophe. The decision to breastfeed is an intimate and private decision. No one should be able to interfere.”

In my mind, this touches on something I have written about before – that to lay down a hard-and-fast prescription for parents to follow is not always straightforward or productive. A more nuanced approach is often required that takes into account the familial circumstances and considers the parents’ well-being as well. It would be no good hectoring parents to follow a particular path, if it leads to a significant worsening of their own physical or mental health, especially if the knock-on effect is a deterioration in family relationships.

It seems highly unlikely that this would allow people to be good parents nor provide a decent environment for the child (a brief look at the scientific literature suggests this assumption isn’t entirely unreasonable, e.g. thisthis and this). It also risks attaching blame to a parent for any perceived character flaw in their child, and guilt-tripping parents in this way seems a counter-productive approach.

The research about ear infections, respiratory disease and diabetes is very mixed. Neither fussiness around new foods nor constipation are classic or very salient markers of good health. The obesity studies are debatable. The weight loss of breastfeeding mothers is taken from a WHO report, based on two interventionist studies in Honduras. It’s nothing like that straightforward: it does use 500 calories a day, but if your appetite increases at the same time, it is amazing how quickly and easily you can pop 500 calories into your mouth. Meanwhile, Wolf points out, no study on maternal cancer has “distinguished the effects of breastfeeding from the behaviour of women who breastfeed”

Again, I agree, it’s not straightforward! But I would, perhaps, strike a more positive tone.

The studies aren’t perfect (Williams also quotes the American Academy of Paediatrics: ‘There are a lot of methodological problems’), but that’s no reason to just give up on evidence altogether. The best available evidence, as far as I can see, is saying that breastfeeding is likely to bring a range of benefits to the child, and possibly some to the mother. A Cochrane Review from 2009 includes many citations that support various benefits of breastfeeding, as well as a discussion of some of the uncertainties.

I also agree that the weight loss data must be taken in context, such as whether you are dealing with developed or developing countries, and some effects, such as iron status, can be achieved through supplementation. So, in some instances, there’s no need to be over-zealous about breastfeeding, as long as adequate healthcare advice is in place.

“The notion of risk [has been] transformed from a dichotomy to a continuum.” It’s no longer a case of “safe” versus “dangerous”; rather, everything carries some risk and you announce your fitness as a parent to the world by interpreting hazards in the most credulous, fervent way. The onus isn’t on the researcher to prove the point any more – the onus is on the parent, or parent-to-be, to prove that they’ll believe the researcher.

I’m not sure this is true and seems an over-generalisation. There’s a huge variety in parental attitudes and some are incredibly questioning, and whether and how this has changed in recent years is uncertain without any data. I think it misrepresents the role of a researcher, too – that the onus is on them to ‘prove a point’. Scientists don’t (or shouldn’t) undertake work to prove already held beliefs, rather they formulate hypotheses and design experiments to support or reject those theories.

There are lots of other points in and around the ones I’ve highlighted, a lot of which veer from my intention to address evidence-based decisions, but I do encourage you to read the whole article for some interesting discussion of feminism and social policy.

I’ll summarise by saying that I would still state that breastfeeding can potentially bring a range of benefits over formula-feeding, because that is where the balance of scientific evidence is, with little or no contrary evidence to dissuade me yet. And this should be reflected in the healthcare advice that is provided. I absolutely agree, though, that foisting this decision on mothers is, at best, unnecessary and, at worst, damaging. Healthcare advice must take context into account.

On a more general point, I welcome any sensible, critical look at the evidence behind claims, as Zoe Williams has done. It’s certainly made me re-evaluate – and in some instances, such as in the link to lowered risk of maternal breast cancer, made me temper – my own standpoint on the benefits of breastfeeding.

A final point, though. It was disappointing that an article that relied so heavily on rejecting or challenging some of the evidence that is used to promote the “breast is best” standpoint, did not once link to any primary research. A few quotes here and there from, no doubt, serious academics, and a link to a book, but nothing that could point the reader to the original research studies.

It is perennial complaint that evidence-based advocates level at popular journalists, so I don’t want to single out this author for special criticism. But it is something that could do with a cultural shift and, perhaps, mainstream commentators will start to follow the examples of their science colleagues.


Hat-tip to Mum-in-law, Jenny, for The Guardian article.

On seeking out the evidence

The running theme of this blog is trying to find the evidence behind some of the stories or claims I come across. This is often tricky, even for someone from a scientific background, as the wealth of slanted and misleading messages in the popular media is sometimes overwhelming. Part of the motivation for this blog was for my benefit in trying to separate fact from fiction, so I hope that by sharing my thoughts, it proves useful to others trying to do the same in the new and scary world of parenting.

There are many great blogs, providing informed, critical analysis of some of the health stories making the news, and I would urge anyone take a look at DiscoverNature, Scientific American, PLoS, Occam’s Typewriter and Scientific Blogging, to name a few. It’s also worth checking stories at science specialist media, such as Discover Magazine and New Scientist, which cast a more critical and cautious eye over the latest scientific research than do some popular news outlets.

As an example of the variability in journalism, see the alarmist headlines reporting the effects of high-dose radiation during pregnancy on offspring:

Frightening stuff, indeed. But the study was actually conducted on mice, which may not be a suitable model for human pregnancy, and the amount of radiation exposure wouldn’t correlate with that of a mum using a mobile phone. The Mail and The Telegraph articles actually include some of this discussion in the body text, but this is only after the sensationalist headlines that do not do the research justice. The New Scientist gave a more reasoned account, pointing out the problems with overly sensational headlines:

So, with this in mind, I wanted to highlight some sites that might be especially useful for parents in getting the facts behind the stories.


Science Daily:

Science Daily is a dedicated science news service that provides informative and critical reporting on the latest discoveries from across all scientific disciplines, including health and medicine. The articles are balanced and accurately represent the research findings, which cuts through some of the ideological or politically motivated spin in some media.

One thing worth highlighting about Science Daily is that each article clearly cites the research on which the story is based. This allows readers to go to the source for further reading, to check the data behind the claims and find out whether there are any funding conflicts. This is often severely lacking in many newspaper articles, a deficiency that has previously attracted the ire of ‘Bad Science’ author and Guardian columnist, Dr Ben Goldacre.

Just look at Science Daily‘s reporting of the story I wrote about last month concerning on-demand vs. scheduled feeding, with a clear citation to the original research – “Feeding Your Baby On Demand ‘May Contribute to Higher IQ“. This is in contrast to the reporting of the same piece of research in many major news outlets – the Daily Mail, The Guardian, The Scotsman and Time,  which didn’t include any links to the original research.


NHS Behind The Headlines:

This NHS-backed news service provides a critical look at the health stories in the media and teases out the evidence behind the claims. It’s a superb, unbiased resource that gets underneath the hyperbole that is often used to sell newspapers, and provides the information that really matters to people trying to make day-to-day decisions that affect their and their family’s health.

Take a look at the Daily Mail (again), which reported “Babies treated in the womb for obesity: Overweight mothers-to-be get diabetes pill to cut the risk of having a fat child”. The big splash is that obese pregnant women are being treated with the glucose-lowering drug, metformin. The aim of the trials is to reduce the chances of the children being overweight themselves, which the Mail suggests is alarming because ‘fatness’ can be solved simply by diet or exercise and because we shouldn’t be ‘drugging’ overweight but otherwise healthy mothers-to-be.

A visit to Behind The Headlines (“Baby obesity research: no need to panic”) quickly unpicks the evidence. The study is also only half-way through and will ultimately tell us whether this treatment can improve health outcomes for mother and baby. Metformin is already being used safely to help obese mothers control their blood sugar levels, which might otherwise lead to complications in pregnancy such as gestational diabetes, pre-eclampsia, premature birth, caesarean section and a larger than average baby. It may also be the case that an overweight baby is more likely to be overweight as an adult, so an early prevention is likely to be more effective than a later cure and I fail to see this as “controversial”. All of this argues against the claim that the mothers receiving the drug are ‘overweight but otherwise healthy’, given the known worse outcomes of obesity for mother and baby,

The article finishes with some general advice for women in pregnancy, such as what to do if you’re worried about losing weight before getting pregnant and whether you should alter your eating habits when pregnant.

So if you see a story in the news, especially one that may motivate you to take major health decisions, then I would suggest taking a look at Behind The Headlines.


More or Less:

Aimed at the more statistically minded amongst us, this radio show/podcast isn’t for everyone. If, however, you enjoy some number crunching to unravel the distorted numbers and statistics used in all walks of public life, then you should find this an engaging listen. Tim Harford is a lucid and entertaining host, and handles the potentially dry subject of statistics in a competently inviting manner. Check out his Undercover Economist blog for more of his analysis.

Hear the More Or Less team discuss the figures behind the claims, Over half of new mothers who die are overweight or obese and Do mobile phone towers make people more likely to procreate?.


These are some of sources I am aware of and which I thought might be useful to others. I’ve recently found the Parenting Science website run by biological anthropologist, Gwen Dewar, which I look forward to picking through for some more evidence-based, rational parenting information.

If anyone has other suggestions, then please share!