Sunday, 21 April 2013

Biologically speaking, when should we stop breastfeeding?

Biologically, we are designed to breastfeed our young. As are, and do, other species with mammary tissue (an organ in female mammals that produces milk to feed young offspring).

This blog isn't about whether we 'should' be breastfeeding our babies - there is no question that we should be, it's why women have mammary glands (breasts) and it provides the nutrition babies needs. Instead what I have done is take the novel approach of comparing between a range of species, the fraction of their lifespan spent feeding their young with milk to determine when, based on other similar species, humans are 'biologically' designed to wean (stop breastfeeding their babies).

Representative data from a number of species showing weaning age, lifespan and the % of lifespan spent drinking mothers milk.

Weaning age (years)
Estimated % of lifespan spent drinking milk from mother

Where a range is given, the average was used to calculate the fraction of life-spent suckling.
Human values for weaning age and estimated fraction of life-spent suckling are given as X as this data varies widely across and within populations.
Weaning age and lifespan values are approximate only and some strain/breed variation exists within species, data obtained from Wikipedia.

The data in the table shows that for the most part, the higher order animals, that is, those species with larger brains and long-life spans, like the human, breastfeed their young for a significantly larger portion of their lifespan than do the lower order animals, that is, those with smaller brains and shorter-life spans. An oddity is the sheep, who spends a large portion of lifespan 4.5% drinking milk in comparison to the dog who has a similar lifespan, who only spends 1.2%.

What is most surprising however is how short, relative to lifespan the majority of Australian women are breastfeeding their babies. The World Health Organisation recommend exclusive breastfeeding to 6 months of age and continued breastfeeding with appropriate complimentary food up to 2 years or beyond (2 years = ~2.6% of lifespan). The Australian National Health and Medical Research Council reported in 2005 that 22% of infants less than 3 months of age were receiving formula and that no (0%!!!) of infants at 6 months of age were exclusively breastfed. Additionally, they reported that only 23% of babies are being breastfed at 12 months of age.

If we take the data in the table above and use it to extrapolate to the human, if we invested 12% of our lifespan (~75 years) feeding our young, as do apes and chimpanzees (our closest genetic relatives), this is approximately 9 years of feeding our young milk and if we invested the same amount of time as cows and horses (~3.5%) this would equate to 2.6 years. 
What it seems we are doing however (based on the NHMRC study), is investing a similar amount of time (relative to lifespan) as rats, dogs and rabbits (~0.7-1.5% of lifespan = 0.6-1.1 years). Species that are strikingly different to the human in terms of growth and development after birth and brain function throughout life.

It is time for more targeted research on the appropriate weaning age for humans - what are the consequences/advantages of short duration breast feeding vs long duration breast feeding? Most importantly it is time that we, as a society, change our attitudes so that breastfeeding, for the biologically appropriate timeframe is accepted, encouraged and supported. 

For further reading see this blog by Kathryn Dettwyler which provides a good summary of many of the studies done by anthropologists to try and determine the appropriate weaning age for humans.

Sunday, 1 July 2012

The things I wish I'd known before I brought my baby home....

Disclaimer: This isn't a 'scientific' blog. I have just become a mum for the first time and wanted to share my list of things I didn't know (or didn't listen to when I was told!) but wish that I had! I certainly don't claim to be an authority on babies, this is my first and she is only 11 weeks old! That said, I feel as though I've learnt a lot of things the hard way and hope that the few points below may help make the transition to motherhood a little smoother for others.

In no particular order:
1. When your baby wakes in the night, feed her first, then once she stops suckling, change her nappy, then feed her again, before putting her back to bed. This will achieve 3 things, 1. She will be fed and changed, 2. It will avoid a screaming session at 2am, brought about by you changing her nappy before you feed her and 3. She may sleep for longer as she will have had 2 feeds, not just 1.
2. Don't bother timing your feeds, instead, pay attention to your baby. You need to learn your babies signals; believe it or not you don't immediately know what your baby wants! Those 'mothers instincts' take some time to develop, but the more attention you pay to your baby, the sooner this will happen!
3. Don't forget you need to rest after you've delivered your baby. Your body has been through a major stress and needs to repair itself; so help it! If you can't sleep during the day (which I couldn't), go to bed as soon as the sun goes down and don't get up in the morning until you feel ready. There is nothing more important than you looking after you and your baby. You need to be at your absolute best to cope with the curve balls that your baby will keep throwing at you!
4. If you sleep on your side, don't sleep in a bra. The bra will put pressure on your breast where you lie and can cause engorged breasts and blocked milk ducts. This will cause you incredible pain and if not quickly rectified (suggestions include: gentle massage, emptying of the breast, apply heat pre-feed and cool post-feed) can lead to an infection which will require antibiotics to treat. If your worried about milk leaking in your bed, sleep on a towel.
5. Don't expect your friends/family to know what you want them to do once you get home with your baby. If you want people to prepare meals for you, ask them, if you want someone to come and clean your bathrooms, ask them. People will be more than willing to help, but most aren't mind readers! And if you want them all to nick off for awhile and let you find your feet, then tell them that to!
6. Expect to achieve nothing (but tending to your babies every need) in the first month after you get home with your baby. That way, when you do manage to do something else, it'll feel really good, rather than being frustrated that you can't get anything else done. Be prepared that some days even a shower will be out of the question....
7. You will be overloaded with advice, suggestions and know how from other people (as above!!). Don't believe everything you read, trust your instincts, and do what is best for your baby.

Happy mothering!

Saturday, 7 May 2011

Breast is best

There remains much discussion about how best to feed a newborn baby; breast milk or formula. We all know the phrase 'breast is best', but it seems there is still a large population of mothers who, in the absence of a medical reason for not breast feeding, choose not to do so. This is despite the World Health Organization recommending that mothers exclusively feed their baby breast milk for the first 6 months of life.

What I wish to discuss here is one aspect of the science of why 'breast is best' and hope that it convinces the mothers who are choosing not to breastfeed, to do it, for the health of their baby.

Your baby is born with a gut and immune system that are functionally immature - that is, because they have been protected by you and the placenta during pregnancy, these organs haven't really had to do anything yet. All of the necessary parts are there, they just need some time to learn what to do.
When your baby is born, there are large gaps in between the cells within your baby's gut. This is so that large molecules from your body, including molecules produced by your immune system, can pass into your baby's blood. These molecules help to develop his/her immune system, as well as protect your baby until its own immune system is fully functional. After pregnancy, these very important molecules can only pass from your body to your baby via the breast milk. In fact, during the first days/weeks after birth, the cells within your breast also have large gaps in them so that these large molecules can pass out of your blood and into your breast milk for your baby. These important molecules are specific to you and your baby, and are not in formula feed.

The gaps in between the cells in your baby's gut are very important for the development of a healthy and strong immune system, but this also increases the risk of your baby getting an infection. Importantly, the gaps between the cells in the gut of babies that are fed breast milk close much more quickly than babies that are fed formula. Closure of the cell gaps in the gut minimize the risks of infection, so that your baby will be protected from getting infections much more quickly if you breast feed.

There is good scientific evidence that the health of your baby will be significantly improved by feeding him/her your breast milk, it is after all, what it is meant for, and what your baby's body is expecting.

Friday, 29 April 2011

Why are women advised to take folate supplements before and during pregnancy?

Key points:

1. Your baby grows by the process of cell division and cells start dividing immediately after the sperm and egg meet (conception).

2. Neural tube defects result when the neural tube (the structure that will become your baby's brain and nerves) doesnt close properly, this event normally occurs by week 4 of pregnancy.

3. Folate plays an important role in the production and copying of DNA, which must occur every time a cell divides and is an important part of closing the neural tube.

4. It is important for women to ensure that their folate levels are sufficient before they fall pregnant, as well as during pregnancy, so that appropriate cell division occurs as soon as your baby starts developing.

5. The body absorbs more folic acid from supplements than folate found naturally in food, so it is important to take only the recommended daily intake of supplemental folic acid (400μg).

Folate is a B vitamin that is found in legumes, leafy green vegetables and some fruits (such as citrus fruits and juices). Folic acid is the man-made form of folate and the form often used in vitamin supplements and in fortified foods you may have seen in the supermarket. We are able to absorb about 70% more folic acid from supplements than we can from folate naturally contained in foods.

Folate plays a very important role in the normal functioning of all cells within our bodies, and it is particularly important when new cells are rapidly dividing, which is how your baby grows and develops during pregnancy. A baby forming from cells dividing is a hard thing to imagine, especially since its a process we dont actually see. But its very important to understand, so Ill try and break it down.

Your baby starts out as only 2 cells. To make more cells, these 2 cells rapidly divide (2 become 4, then these 4 become 8, 8 become 16 and so on) so that by the time you are only 5 days pregnant, your baby, (called a blastocyst at this stage) is made up of between 80-160 cells. Of these cells, one third will continue dividing to eventually become your baby and the remainder will become the placenta. By mid-pregnancy (20 weeks), the number of cells in your baby's brain alone is approximately 20 billion and when he/she is born, the total number of brain cells is about 40 billion. This process of cells dividing to form new cells is called mitosis and you can see a basic diagram of this in Figure 1.

When each cell divides, our DNA (the genetic code that make us who we are; our genes) is also copied so that there is an identical copy in each and every new cell that forms. Folate plays a key role in this process. If someone is folate deficient, or has low levels of folate in their blood, this has been shown to decrease the rate that DNA is produced and copied into each new cell. This basically means the cells dont divide and copy the genetic code as they should. This is how defects occur.

The most widely publicised role for taking folate/folic acid supplements during pregnancy is for the prevention of neural tube defects. This group of abnormalities affects development of the neural tube, the structure that eventually becomes your babies brain and nerves (see Figure 2). The neural tube should close by the time you are 4 weeks pregnant.

It is thought that a folate deficiency increases the risk of neural tube defects.

Specifically, instead of the genetic code telling the neural tube to close, it stays open. The two most common neural tube defects are anencephaly and spina bifida (see Figure 2). Anencephaly occurs when the skull part of the neural tube doesnt close properly, this is very serious and babies with anencephaly are usually stillborn (the baby is dead at the time of delivery), or die soon after birth. Spina bifida is when the spinal part of the neural tube doesnt close properly. This is also very serious, and if your baby survives, he/she will need extensive surgery and medical care. Babies with spina bifida who do survive usually suffer severe mental and physical disabilities. It is important to know that neural tube defects are usually not detected in pregnancy until the 18-20 week ultrasound.

But the news isnt all bad, scientific experiments and big clinical trials have shown that taking folic acid supplements before falling pregnant can significantly lower the risks of these neural tube defects.

The World Health Organisation (WHO) recommends that women have 400μg (micrograms) of folic acid each day in supplements, as well as eating foods that are folate rich. To ensure adequate folate levels for your babies' cells it is recommended that women start taking folic acid supplements 12 weeks before conception. Because we can absorb much more folic acid in supplements than folate contained in foods, it is important not to overdose on folic acid supplements, because this can mask some of the symptoms of vitamin B12 deficiency (which can cause other problems). It is recommended that the daily intake of supplemental folic acid is not more than 1,000μg per day. To work this out make sure you read the labels on supplements and fortified foods.

There maybe some circumstances in which your doctor may advise higher levels of folic acid supplements, such as if you have a past history of neural tube defects, are taking anti-epileptic drugs or if you have diabetes.

In summary, folate plays an important role in the division of new cells and it is important to understand that your babies growth and development occurs because cells are dividing. Folate levels should be adequate before conception and throughout pregnancy because cellular division is an essential part of your babies development from the very moment of conception.

Acknowledgments: Jake of Ranz for the figures and Dr. Leah-Anne Ruta for editing.

Disclaimer: All information contained within this blog represents my own interpretation of published scientific works. Before any supplement/dietary intervention is considered by a pregnant woman/woman planning on becoming pregnant, it should be discussed with your doctor.

The references I used during the preparation of this blog are listed below:

[1] Tucker M, Morphological scoring of human embryos and its relevance to blastocyst transfer.

[2] Samuelsen GB, et. al., The changing number of cells in the human fetal forebrain and its subdivisions: a stereological analysis. Cereb Cortex, 2003. 13(2): p. 115-22.

[3] Kamen B. Folate and antifolate pharmacology. Semin Oncol 1997;24:S18-30-S18-39.

[4] Czeizel AE, Dudas I. Prevention of the first occurrence of neural-tube defects by periconceptional vitamin supplementation. New England Journal of Medicine 1992;327(26):1832-5.

[5] Anonymous. Prevention of neural tube defects: results of the Medical Research Council Vitamin Study. MRC Vitamin Study Research Group. Lancet 1991;338(8760):131-7.

[6] De-Regil LM, et. al., Effects and safety of periconceptional folate supplementation for preventing birth defects. Cochrane Database of Systematic Reviews 2010, Issue 10.

[7] McNulty H, Pentieva K. Folate bioavailability. Proceedings of the Nutrition Society 2004;63(4):529-36.