The Cow’s Milk Hypothesis and TRIGR: A Rationale for Exclusive Breastfeeding?

There are lots of good reasons to breastfeed. The ones that seem to be most commonly discussed include transferring antibodies to the baby; Convenience, with milk always available when required at the right temperature and no need for any special equipment or preparation; Cost saving against the cost of formula milk; And general health benefits to mother and baby including reduced risks of problems such as certain cancers and obesity respectively.

Despite the benefits though, breastfeeding remains far from universal in the UK. The 2005 Infant Feeding Survey, the most recent for which full results are currently available, gives a UK-wide initial breastfeeding rate of 78%. At six months less than 25% of mothers were giving any breast milk at all. Exclusive breastfeeding rates (where no other foods or liquids except breast milk are given) were 45% at 1 week, meaning that more than half of all mothers had supplemented with infant formula within that week. These figures fell to 21% at six weeks and 7% at four months. The proportion attaining the target outlined in official Department of Health Guidelines, in line with World Health Organisation guidance, of 6 months of exclusive breastfeeding was less than 1%. These figures add up to one of the lowest breastfeeding rates in the world.

Early results of the 2010 Infant Feeding Survey, published in June this year, do show that initial breastfeeding rates have increased to 83%, so it is not unreasonable to suggest that some of the other rates may also have increased. However, anecdotally at least, it seems that there are possible causes for a rise in initial rates, including formula often not being available in hospital maternity units, and short term improved breastfeeding support, which are not applicable to long term feeding rates. In fact, anecdotally again, it seems that longer term breastfeeding support is frequently poor, if available at all.

I do plan to breastfeed this baby when they arrive, however. It wasn’t something that required much thought. In fact, I can’t remember a time at which I thought I would try to do anything else. But I am determined to succeed for very different reasons to the majority of women. It’s a reason that is so important to me that it may just help me be in that 1%. But equally I’m afraid that I’m setting myself up for huge self disappointment if I allow myself to make breastfeeding so important. I’m concerned that I’ll put inordinate pressure on myself to succeed and instead be doomed to failure.

As with many things in this pregnancy, diabetes is my motivation. Or rather the possibility of its prevention for my child.

It’s not a great secret that I’m not particularly in love with diabetes. I’ve made my peace with it for now, and I accept it is what it is, but I still wouldn’t wish all of its difficulties, frustrations and complications on to my worst enemy. So I would do anything I could to make sure that my child doesn’t have to live with any diabetes other than mine.

Modern thinking on the aetiology of diabetes is looking towards a combination of genetic predisposition with an environmental or other external factor triggering autoimmune destruction of insulin producing beta cells. The genetic component is complex and there is no simple heredity involved. The risk of developing diabetes if you have a first degree relative with the condition is only 10% and most people who develop it do not have a family history at all. However it is certainly possible that I have passed on a genetic tendency, so all that I can do now is my best to modify any other contributing factors. And one of the most prominent of those currently under investigation is cow’s milk.

The Cow’s Milk Hypothesis emerged more than 20 years ago when preliminary studies suggested a link between cow’s milk proteins and the development of type 1 diabetes including a decreased incidence of type 1 amongst breastfed children in the US, and higher levels of antibodies to cow’s milk protein amongst Finnish children who had diabetes than those who did not. A more specific study in 1991 showed that 100% of the children with diabetes in the study had high levels of antibodies to a specific region of bovine serum albumin molecules. Only 2.5% of the healthy children had this specific antibody. Combined with circumstantial evidence, such as a correlation between per capita milk consumption and type 1 diabetes incidence rates worldwide, and the increasing consumption of cow’s milk based infant formula milk alongside significantly increasing incidence of type 1 diabetes in countries such as China, this has been enough to support a large scale trial to test the theory that early introduction of traditional cow’s milk protein based infant formula may increase the risk of type 1 diabetes.

Of course the Cow’s Milk Hypothesis isn’t really the cow’s milk hypothesis – it’s the Protein Hypothesis. It’s simply that the first non-human protein foodstuff that babies are exposed to tends to be in formula milk and is a cow’s milk protein. But it’s the protein, not that it’s cow’s milk, that potentially poses the problem. The presence of any foreign proteins before the age of 6 months is a massive challenge for the immune system, which can lead to a tendency towards autoimmunity. In someone who already has tendency to diabetes, this could possibly lead to its development. The theory continues that by 6 months, the immune system has developed and there has been staged exposure to some of these challenging proteins, so is better able to cope with their introduction in to the diet. Another factor which lends weight to this theory is the fact that a number of the genes known to be associated with type 1 actually cause an increase in gut permeability, thus allowing these proteins to pass across.

One way to avoid the exposure to large proteins, other than breastfeeding, is to use a milk formulated without those proteins – where they have been broken down to a small enough size that the immune system can’t “see” them. Such “highly hydrolysed” formulations are available for babies with cow’s milk protein intolerance. A randomised feeding study involving 240 children with a close-family history of type 1 diabetes and autoimune markers present, showed that the risk of developing either type 1, or at least two beta cell antibodies, was cut by a half in the group given such highly hydrolysed formula milk compared to those given traditional formula.

In 2002, recruitment began for the Trial to Reduce Insulin Dependent Diabetes Mellitus in the Genetically at Risk (TRIGR) – a large multinational randomised controlled trial to investigate whether infant feeding really does have the potential to modify the risk of developing type 1 diabetes. The TRIGR trial will determine whether delayed exposure to intact food proteins will reduce the chances of developing type 1 diabetes later in life.

Secondarily, the study will also show if there is any specific positive effect of exclusive breastfeeding over using a formula in which the proteins have been broken down – a so-called highly hydrolysized formula – instead. This was not an intitial study aim, but has come about because a a higher percentage of mothers than expected achieved exclusive breastfeeding until the age of 8 months.

TRIGR is not completed yet. It might prove the hypothesis completely invalid. Or it might prove that actually there is some hidden benefit to traditional milk formulas, although based on the preliminary research I think this is unlikely. So why am I so adamant that I want to breastfeed to potentially reduce type 1 diabetes risk anyway?

The breastfeeding part is because highly hydrolysed formula milks are available in the UK only on prescription from a doctor, and the prescribing guidelines stipulate their use only for cow’s milk protein sensitivity. So breastfeeding is the only accessible way for me to avoid cow’s milk proteins, which I want to do because it seems to be what nature intended. The TRIGR study group themselves state that the aim is not to interfere with or specifically modify feeding – particiapnts have been encouraged to breastfeed in line with WHO guidelines. The study simply looks to see the effects of different feeding when this comes to an end. In the absense of any clear clinical data, it makes sense for me to stick with what nature intends human babies to drink.

This is a highly personal decision, and I wouldn’t for a moment advocate that everyone should do the same. But with all the known benefits of breastfeeding that already exist, it seems illogical for me to give my human baby anything other than human milk.

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