Category Archives: Childhood

Four ways breast milk is really interesting

You might have heard a lot that breastfeeding may reduce the risk of infections, allergies and gut problems. But it’s perhaps even more fascinating than you realise.

1. Mums may produce different breast milk for sons and daughters

Dr Katie Hinde from Harvard University studies lactation in monkeys to understand how breast milk provides not only nutrition, but shapes immunity, nervous systems and behaviours in their offspring.

Her team has found that even a monkey mother’s own breast milk can vary in the composition of fat, hormones, protein and minerals. It can depend on her age, how many children she’s had and what she’s been eating now and in the past. But, as this Naked Scientists interview explains, it even matters whether she’s had a son or a daughter.

Rhesus macaque monkeys produce more, lower energy milk for daughters, but less, higher energy milk for sons, in such a way that the overall energy supplied balances out. Why this is is unclear and Dr Hinde’s team is working to unpick these tricky questions. The monkey mothers also produce more calcium for daughters, which Dr Hinde speculates is linked to a quicker development of daughters’ skeletons.

As the interviewer, Kate Lamble asks, how do the monkey mums know whether it’s a son or daughter? Dr Hinde thinks it’s probably down to more hormones produced during female foetal development affecting mammary glands. It could also be behavioural interactions between mother and offspring after birth.

The big question is, does this hold true for humans? Is this something that mattered more in our evolutionary past, but is less relevant in our cosier modern world?

2. Time of day matters

Many animals exhibit day-night rhythms that can affect everything from sleep-wake cycles, metabolism, immune responses and heart rate. And it seems breast milk production is no different.

Milk produced during the night contains higher levels of a hormone, melatonin, which is known to regulate day-night (“circadian”) cycles. Researchers have suggested this can help reduce irritability and prolong night-time sleep, but more work is needed to show this for sure. Adults can manufacture melatonin from essential molecules taken in through the diet, but babies can’t.

Other studies have focused on tryptophan – an important building block in the body’s biochemical manufacturing of melatonin. One study linked higher levels of tryptophan in breast milk at night with a rise in melatonin in the breast-fed babies, which was also associated with more sleep.

To try to establish whether elevated tryptophan caused improved sleep (rather than because of some other differences between breast- and formula-fed babies), another study compared babies who were fed formula milk with added tryptophan at night, added tryptophan in the day and with no added tryptophan at all. Only babies fed added tryptophan at night had better sleep and metabolites in the urine suggested this was down to the production of more melatonin.

Whilst the overall effect on babies’ sleep and whether fluctuations in the makeup of breast milk can really cause changes is still to be fully teased out, these findings suggest that mothers who express milk for their babies for a later time may want to pay attention to what time of the day they did it.

3. Hormones in breast milk can affect behaviour too

Hormone levels, such as cortisol, can naturally fluctuate throughout the day. Cortisol, in particular, is not only important in the stress response but is needed in the mammary glands to stimulate new milk production and protect the survival of mammary cells.

Researchers comparing breast- and formula-fed babies have suggested that higher cortisol levels in milk are associated with more fearful babies. Others studying monkeys and humans have reported levels of maternal cortisol affecting temperament in three-month olds, and this may differ for sons and daughters. For some animals, like red squirrels, it may give them a competitive advantage – cortisol-like hormone levels rise as a forest gets more crowded, which accelerates the growth of their offspring.

Back to Katie Hinde’s research. Again, studying rhesus macaques, her team wanted to know whether these effects were genuinely down to cortisol or because of variations in the amount of nutrients passed on (which are in turn affected by hormone levels). The researchers measured milk one month after birth, and again three to four months after birth. Generally, higher levels of cortisol in milk were associated with babies who scored higher for nervousness and lower for confidence.

But why? They point to evidence that elevated cortisol in humans may lead to reduced growth, and speculate that there may be a trade-off between infant temperament and growth – if more nervous, less confident behaviours reduce activity, then the available energy from milk can be put towards growth, particularly for sons. This may be particularly crucial in times when resources are scarce or competition is high.

At least in rodents, the receptors for these hormones are most abundant in the gut in infancy, before declining into adulthood. This suggests that babies of at least some animals may be taking an active role in sensing the environment through their mother’s milk.

 

4. Breast milk may shape the friendly gut bacteria

Californian researchers compared the bacteria in the intestines of breast- and bottle-fed baby macaque monkeys between five and 12 months old. They also took blood samples to analyse the immune cells in the growing babies.

The bacteria profiles in each group showed stark differences. The breast-fed babies contained higher levels of Prevotella, Ruminococcus and Lactobacillus, whilst the bottle-fed babies had higher levels of Clostridium. The immune systems of the two groups also differed. Breast-fed babies had more immune ‘memory cells’ and ‘helper cells’ (which help fight off foreign invaders) and produced a sturdier immune response when isolated blood cells were challenged. The researchers noticed differences in chemical signals in the blood known to influence how the immune system develops.

Another study, this time on mice, may give clues as to one way this can happen. By manipulating particular antibodies in maternal milk, these researchers showed that a lack of antibodies produced very different bacterial gut colonies and affected how well the mice could cope with an intestinal insult. Both studies showed that variations in bacterial profiles were still seen many months after the experimental diets ended, indicating that the effects on the immune system may be very long-lasting.

All this suggests that breast milk, possibly through the action of antibodies, causes certain helpful microbes to colonise the gut. These then produce a spectrum of chemicals that help shape the maturing immune system, making it better equipped to fend off infections and less likely to trigger allergic reactions.

The question is, for humans in today’s world, how much would these variations actually matter?

 

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“.)

Should babies watch TV?

This question seems to trouble many parents, and can cause a lot of guilt too.

“Will the TV numb my baby’s brain?”

“Are they destined for a sedentary life?”

“AM I CONDEMNING THEM TO LIFE AS A MINDLESS AUTOMATON?!”

This is why an interview last week with psychologist Annette Karmiloff-Smith on the BBC’s The Life Scientific caught my ear (thanks to a pointer from mum-in-law, Jenny). It’s a fascinating insight into how babies learn to learn, and how their brains develop to understand the world around them. You can listen here: The Life Scientific.

But on TV watching, Prof Karmiloff-Smith, an expert in developmental disorders, argues that if the subject matter of the programme is carefully chosen and scientifically based, then the TV can be better for a child’s learning than even a book.

This was largely in response to advice reissued by the American Academy of Pediatrics (AAP) that babies under two shouldn’t watch any TV or DVDs. There are three main concerns: poorer language skills, a negative effect on sleep, and less time spent taking part in other types of unstructured play that are critical for the proper development of mental capabilities.

This is based on a growing body of scientific research. TV/DVD watching is common: in the US at least, by two years old over 90% of children regularly watch TV, spending an average of 1-1.5 hrs a day in front of the box. Very young babies (under 1.5 years old) cannot, however, really understand TV programmes, and are instead mainly attracted by obvious changes like applause or visual surprises.

Children learn new words or actions better when an adult is teaching it to them live, rather than via a television screen, and the worry is that parents talk to their kids less when the TV is on. And a growing number of studies suggest that children who spend longer watching TV/DVDs have delayed language development, at least in the short-term, and may also develop a worse attention span.

A child’s play may also be hindered by the distraction of a TV that’s on in the background, so the AAP advise to turn it off altogether. Many parents also use TV/DVDs as a sleep aid, but there is evidence that bedtime viewing may lead to more disturbed and shorter sleep.

Karmiloff-Smith, on the other hand, argues that we live in a media saturated world and it’s unrealistic to expect parents to shut down all media use. This view has support from some of the evidence cited in AAP report itself. Despite the original recommendation in 1999 that parents should be discouraged from letting their babies watch TV/DVDs, over 90% of them in the US currently do so by the time their child is two years old. What’s more, the average age that TV is introduced is 9 months, so the advice is clearly not striking a loud enough chord.

From my experience, I can certainly appreciate this. The AAP report says that many parents use the TV so that they can have a shower or cook dinner. Absolutely! Even these seemingly mundane activities can feel like an exercise in military-like efficiency when you’re looking after a child. A 10-minute respite when they’re quiet and content gazing at a TV or prodding an iPad can be just too tempting.

It’s also interesting to consider that throughout history many new technologies have been treated with caution. Dr Vaughan Bell, a psychologist based at King’s College London, has highlighted how the printing press, popularisation of the radio, and now the Internet have been damned for ruining kids’ brains.

Karmiloff-Smith goes on to say that, rather than banning TV for babies, TV programmes just need to be made better and based on science developments. For instance, the visual system is attracted by movement, but most kids’ TV programmes have their focus on the centre of screen. Instead, objects and features that come in from the sides, move across screen and encourage the child to interact promotes the active participation that’s good for mental development. For very young babies, moving image media may even have advantages over books, which are static and whose main attraction is the rustling of the pages.

The caveat in this is that Karmiloff-Smith reveals herself to be a scientific consultant to a DVD company that is designing such programmes. This could cause suspicion of a financial conflict of interest. But her honesty and gusto make me suspect that she became a consultant so that she could promote these ideas, rather than the other way around.

She finished the interview by emphasising that parents still need to interact with their children and the TV shouldn’t be used as a babysitter. But we should think more carefully about which types of media can stimulate the visual and auditory systems, so as to help train the attention and memory systems early.

I’ve written before about the various kinds of programmes and the various contexts in which kids can watch TV, which may have different effects on child development. And some of the evidence cited in the AAP report highlights these complexities. The effects on children’s attention, for instance, seem to depend on the programme content and style, with problems seen not when the content is deemed educational but only when it’s geared towards entertainment. And when a parent watches a programme with an infant and talks them through it, the child tends to become more attentive and responsive. The AAP report also points to evidence that watching Sesame Street can have a negative effect on expressive language in children under two. But the same study showed that watching other programmes, such as the North American-based shows Dora the Explorer, Blue’s Clues, Arthur, Clifford, or Dragon Tales, was associated with greater vocabularies and higher expressive language scores. So it appears that not all ‘screen time’ is equal.

The AAP report seems to fall into the trap of treating all TV and DVD viewing as the same:

For the purposes of this policy statement, the term “media” refers to television programs, prerecorded videos, Web-based programming, and DVDs viewed on either traditional or new screen technologies.

Another major limitation of the AAP report is that all of the cited studies are, by necessity, observational. These investigations are good at highlighting whether two factors are associated with each other, but they cannot tell you whether one causes the other. As the report itself asks, are children with poor language skills simply placed in front of the TV more? Are children with shorter attention spans more attracted to screens? Are parents who are less attentive on the whole, more prone to resort to screen time? If so, then turning the TV off would not necessarily lead to more parent-child interactions.

And some results are just contradictory. One study in the US showed that when the mother’s educational status and household income were taken out of the equation, the association between TV viewing and poor language development disappeared. This appears to have been glossed over by the AAP.

So how do I answer my original question?

The AAP are right to caution against a lot of TV for under twos (over four hours a day, say), as this is when the damaging effects are really apparent. But Karmiloff-Smith is also right to say it’s unrealistic to expect no TV at all, and that the right programme in the right environment is fine and potentially beneficial.

And I’ll leave you with this quote in Time from Dr Dimitri Christakis, a paediatrician at Seattle Children’s Hospital:

Ask yourself why you’re having your baby watch TV. If you absolutely need a break to take a shower or make dinner, then the risks are quite low. But if you are doing it because you think it’s actually good for your child’s brain, then you need to rethink that, because there is no evidence of benefit and certainly a risk of harm at high viewing levels.

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.

SZZ2C7MMNW2B

Hoping for a Seahorse but a Limpet Might Just Do

I’ve tried before to articulate my hopes and aspirations for the next generation, in a possibly vain attempt to pass on some of my wisdom (ahem) and experiences. I encouraged a sense of wonder, to be questioning and to favour reason over superstition.

This was brought back to my mind on reading Robin Ince‘s elegant post on inquisitiveness. It captured wonderfully the idea of always questioning the world around you, something I had wished to grant to Harry and Reuben. So I thought I would share it here.

Robinince's Blog

here is my usual warning of spelling mistakes, punctuation horrors and possibly ill-thought out ideas. this one is a reaction to peering into rock pools. I haven’t yet found time to reply to people’s comments on last blogs, but thank you to those that left them whether negative or positive ( a much smaller thank you to the negative ones obviously, said through clenched teeth in a mockery of good manners)

One of my favourite train journeys is from London to Cornwall. It is a pleasant, sometimes beautiful, crossing through the pastures and countryside of southern England, but from Exeter St Davids to Newton Abbot it can dazzle and enlighten even when an umbrella of storm clouds overshadow it. The rails are as close to the sea as any train line I know. Tunneling through the cliffs and then almost avalanching onto the coast, it is a vision of the…

View original post 2,076 more words

366* days later…

The little man is one year old today. It’s been something of a rollercoaster, with time often dragging at an excruciating pace (crying nights) and zipping along at a breakneck velocity at others (how long did his first set of clothes last?).

I often scoff at arbitrary milestones – why was my 30th birthday worth more celebration than my 29th or 31st? – but a single year does mark a significant planetary event. Many animals are intimately linked with the calendar year, displaying ‘circannual’ (= “about a year”) cycles, observed in the reproduction of ground squirrels and the migration of birds. Even testicle size can be affected by a yearly rhythm.

Anyway, fluff and bluster aside, here are some awesome videos to mark the occasion. Happy birthday Reuben!

A montage of the four season, with footage clipped from Planet Earth (from AJS6251):


A year of sunrises, as viewed from METEOSAT-9 Earth-observing satellite (from TheBadAstronomer):


And, what actually is a year? (from cassiopeiaproject):

—-

* Leap year

The influence of early eating habits in children

Our little one, who is now 10 months old, seems to have got his eating sorted after a stubborn start. We started weaning around the World Health Organization’s recommended 6-month mark, using a mix of spoon feeding and baby-led weaning (more on that in later post). Since then, it has seemed apparent that some things have gone down better than others: scrambled eggs, yoghurt, cheese, toast, chicken, bananas and strawberries were all early hits, while broccoli, tomatoes and beef were swiftly rejected.

He seems to have developed an appetite for some foods after a unsure start, such as cucumber, carrot and apple. And this brought to mind a Naked Scientists podcast from a few months ago, which featured an interview with Marion Hetherington, Professor of Biopsychology at the University of Leeds, on children’s appetite and eating behaviour.

The full transcript is available here and the audio is available here. I’ve made a few summary points below, but do check out the full interview.

  • A developing foetus can encounter tastes and odours derived from the mother’s diet and toxins from the environment, and this may affect later food preference.
  • Babies fed with breast milk are exposed to a greater variety of flavours than are formula-fed babies, and this can mean they are more willing to try new tastes.
  • Babies are primed to accept sweet tastes from birth, whereas bitter tastes are rejected. This means that we have to learn to like bitter foods but not sugary foods.
  • Parents may need to try their baby 8-10 times with a new flavour before the child will accept it, so parents shouldn’t give up after the usual 2-3 times. Also, there may be a sensitive period between 6-9 months in which to introduce new flavours and textures, after which it becomes harder for the child to accept a new food.
  • If a child of school age is fussy about trying new foods, then using rewards and social praise is an effective way of persuading them to test new tastes.
  • Setting healthy eating preferences early on is best to keep healthy eating going into childhood. Even if eating habits go awry in teenage years, many return to their early healthy eating habits as adults.

I thought this raised some interesting points, such as the persistance needed to introduce new tastes during a sensitive time window, and was worth highlighting.

It’d be interesting to know how these environmental factors interact with genetically influenced preferences, such as whether early exposure to broccoli, sprouts or cabbage can moderate the repulsion certain people have towards a compound in those foods. It has been suggested that ageing, smoking or illness may modify this genetically based food preference, and so it would be intriguing to know whether child eating behaviour did so too.

Demanding babies and fraught mothers

There was quite a bit of coverage at the end last week about a report published by Essex and Oxford-based researchers that looked at the effects of on-demand feeding versus scheduled feeding. The researchers analysed just over 10,000 thousand babies born in the 1990s and checked whether babies fed in a particular way at 8 weeks and 33 months achieved better academic results later in their lives and whether the well-being of the mothers was affected.

The authors of the study reported an association between being fed on-demand as a baby and higher IQ scores at 8 years and better SATs exam scores at 5, 7, 11 and 14 years. This held true for breastfed and bottle-fed babies. Another effect they uncovered was that mothers who fed on-demand reported lower confidence, higher fretfulness and worse sleep patterns.

Photo by Anton Nossik*

Now I’ve mentioned quite a few times the mantra that “correlation does not imply causation”, and so my immediate reaction to seeing this in The Guardian was ‘here we go again’. Journalists often overlook the limitations of correlative studies in favour of neat and tidy story – after all, “this behaviour causes this effect” has a bit more punch than “this behaviour is associated with this outcome, but it may be acting through a third or multiple independent variable(s)”.

For an entertaining and revealing example of this issue, I would recommend reading stand-up mathematician Matt Parker’s ‘mobile phone masts cause increase in birth rates’ hoax story.

My first thought when my wife told me about this story was that, rather than on-demand feeding directly causing the higher IQ scores, it could equally be that a third factor was at play. As a speculative example, it could be that an attentive personality primes a mother to feed on-demand and also, independently, to spend more time with their child on educational development. This is an important distinction because it would mean that mothers wouldn’t be able to improve their child’s academic chances by feeding on-demand, rather they would have to pay more attention to educational development.

The authors were well aware of possible confounders and tried to take into account other differences between the groups to narrow down the possibilities as much as possible. This involved adjusting for family income, the education level of the parents, different parenting styles, the age and sex of children, and general maternal health. After all this, there was still a significant difference – children who were fed on-demand as babies had, on average, IQ scores 4 points better than children who were fed to a schedule.

This study has an advantage over many other correlative studies in that a third group presented itself – mothers who wanted to feed to a schedule but were unable to and so fed on-demand, i.e. they wanted to be in one group (scheduled feeding) but ended up as if they were in the other group (on-demand feeding). Crucially, the children in this third group achieved the same elevated academic achievement as seen in the other on-demand group.

Photo by Tom Carmony**

This meant that the authors were able to suggest that the improved academic outcomes weren’t due to having the type of mother who wishes to feed to a schedule, but that they were due to the actual act of being fed on-demand. This relies on an assumption that the mothers in the scheduled feeding group and the attempted scheduled feeding group had similar characteristics, and would therefore have similar approaches in other ways that may affect educational development. This may not be entirely true as other, more subtle differences could exist between these groups, but it’s a tantalising result that merits further investigation. I guess measuring the amount of time spent with the child on learning and development would be something at which to look.

There will still be other factors at play and it is still essentially a correlation, but it starts to narrow down the possibilites. The authors themselves admit the limitations in their study, with the lead author Dr Maria Iacovou telling Science Daily:

“At this stage, we must be very cautious about claiming a causal link between feeding patterns and IQ. We cannot definitively say why these differences occur, although we do have a range of hypotheses. This is the first study to explore this area and more research is needed to understand the processes involved.”

Dr Iacovou was also fairly even-handed on Channel 4 news, rightly highlighting that we still don’t know the mechanism for the observed effects and this is really the first step in establishing a causal relationship.

The final thing to note about the study, is that it was gratifying that the researchers looked at both sides of the issue – the outcomes for the baby (IQ, academic achievement) and the mother (well-being indicators). I’ve written before about the importance of looking at all knock-on effects, as it can be counter-productive to focus solely on the baby if it means a serious detrimental effect on the mother’s mental health.

If on-demand feeding really does drive academic development, then implementing a healthcare strategy to encourage this must take into account the negative impact this may have on the mother and include an appropriate support mechanism. Otherwise, the effectiveness of the intervention will be limited, as mothers will be more likely to give up in favour of a reassuring routine.

As Dr Iacovou said, “mothers are people too”.

—-

Hat-tip to mum-in-law Jenny who sent me this story.

*CC licence: http://creativecommons.org/licenses/by/3.0/deed.en

**CC licence: http://creativecommons.org/licenses/by-nc-nd/2.0/deed.en_GB

Do all babies start off female?

There was a bit of coverage last week in the scientific and popular press about some research that appears to refute the idea that the human Y chromosome could disappear at some point in our evolutionary future. In early mammals, the Y chromosome was the same size as the X chromosome but, during the course of our evolution has shrunk to a fraction of the size. This has led to the theory that the Y chromosome could disappear altogether if this shrinking carries on, but the new study has challenged this notion by showing that Y has, in fact, remained a fairly stable size over the last 25 million years. It seems that we may be arriving, or have arrived, at the bare essentials – the non-critical genes have been stripped away over time and natural selection has preserved the vital ones.

The jury’s still out on whether the Y chromosome will become extinct – “we won’t nail it without a crystal ball”, said Professor Darren Griffin of University of Kent in a Guardian article – but this sparked a memory of a conversation I had a while ago about what it is to be ‘male’ or ‘female’.

Some of wife’s friends had been debating whether or not all babies “start off as females”. This debate arose, I guessed while desperately trying to recall my high school biology classes, because of the fact that all fertilised embryos develop along the same path, regardless of the genetic make-up of the embryo. This is until certain genes on the Y chromosome (if present) are activated at around eight weeks and male-associated hormones, chiefly testosterone, are produced that act on some cells to start forming male-specific organs. Without these hormones kicking in, which is the case  in XX embryos when no Y chromosome in present, the cells in the developing embryo go on to form female-specific organs. This means that fertilised embryos under normal circumstances will develop female-specific sex organs unless a hormone cue is activated that signals otherwise.

So all embryos are female, then?

Hmm, perhaps not. One can still make a genetic distinction between males and females at the very point of fertilisation – XX chromosomes will give rise to females and XY will lead to males – and this remains static throughout an individual’s development (and, indeed, life). There are, however, some clinical oddities that throws some confusion into the mix. Some males, for instance, have two X chromosomes but develop as males instead of females because of the presence of a third, Y chromosome that contains the genes to provide the male hormone cues (“Klinefelter’s syndrome“).

So could we define maleness as the presence of at least one Y chromosome (some males are XYY too)?

Not really, because that definition comes unstuck when we consider individuals who are XX but develop as males (at least outwardly), due to the gene for the male hormone cue being copied to one of the X chromosomes (“XX male syndrome“), or individuals who are XY but develop as females, due to a defective Y chromosome (“Turner syndrome“) or mutated Y genes (“Swyer syndrome“).

This leads to complications when trying to enforce a purely genetic definition of gender. The International Olympics Committee for years attempted to enforce this view to adjudicate on cases of gender uncertainty, believing that this represented a more definitive and less intrusive test than physical examination. In this Y-centric definition, without ever meeting an individual and having only a few of their cells, the presence of the Y chromosome or any of its genes (such as the male sex determining gene called ‘Sex-determining Region Y’ (SRY)) would lead to the conclusion that those cells came from a man.

However, for the reasons I mentioned above about all the genetic uncertainties, pressure from a number of medical associations in the USA thankfully led to this sort of test being dropped by 2000. A ‘one-or-the-other’ test of this sort simply does not fully account for the complexities of gender and can lead to discrimination and unfair impediment. The lead opponent of such gender screening, Georg Facius, even proposed a ‘third gender’ for those that could be considered both male and female. One instance where this could be applicable is in cases of “Androgen insensitivity syndrome“, in which XY individuals show abnormal responses to the masculinising hormone androgen. Because the effects can vary, some individuals are anatomically male but have reduced fertility (mild), some possess ambiguous genitalia (partial), while some are almost indistinguishable from XX females (complete).

Even going back to the possible demise of the Y chromosome casts doubt on this Y-centric world. The experts that do anticipate the disappearance of Y are not predicting the end of ‘males’, rather they envisage another sex determining mechanism will take over. This happened before the emergence of the Y chromosome (sex was determined by environmental factors, such as temperature, and still is in some reptiles) and occurs in mammals where the Y chromosome has disappeared (in spiny rats, for example, the male-specific genes have hitched onto other chromosomes).

And this is all before we get into the complex world of gender identity, such as when an individual of one gender is uncomfortable being associated with that gender, which may be environment-driven (or may not be, or may be a little bit). Nor have I touched on psychological and behavioural differences, which lie on a continuous and overlapping spectrum between males and females and are often socially defined (and therefore subject to variation and change).

So none of this means that an embryo is female before the male signals kick in. It is perhaps more accurate to say that an embryo is gender-neutral, i.e. neither male nor female, until towards the end of the embryonic period, at which point anatomical differences start to become apparent in the foetus. But even then, as highlighted above, someone may share characteristics of both sexes and remain ‘double gender’.

Which is all a long-winded of way of saying that a binary male-female distinction is a little fuzzy.