Babies and food: when to introduce solids?

Advice around when to give babies solid food has changed dramatically over time, and advice regarding allergies is also changing. But what are the guidelines, and what science is there to back them up? When should we be introducing solids to babies?

A quick note on the terms:

  • Allergy: the reaction to the food or other substance
  • Allergen: the food or other substance someone reacts to

The recent history 

Some of the vintage posters from the 1940s and 1950s are telling of how different current advice is, compared to only a few decades ago. This one, from a 1947 issue of Life magazine, recommended introducing strained meat into a baby’s diet from six weeks. Trying to get a baby to eat meat with a “custard like consistency” is beyond my imagination, never mind the resulting nappies!!

While this is shocking by today’s standards, a study of 100 mothers in the 1970s showed the most common time to introduce solids was three to four weeks, the earliest being two days old. Although the age of introducing solids got later in the 1980s, it wasn’t until 1995 in the UK that four to six months was recommended.

In 2003, the Department of Health in the UK adopted the World Health Organization guidelines (published in 2001) and recommended the introduction of solids at around six months of age. By 2010, 69% of mothers were waiting until 17 weeks, though 75% had introduced them by five months.

As well as when to introduce solids, there has been much changes in what we have been advised to introduce, particularly in relation to allergens. Currently the NHS website advises to not introduce key allergens like wheat, gluten, nuts and fish until six months, and then to introduce them slowly. It also states there is no need to delay past six months. However, previous advice for mothers with allergy in their family was to consider excluding peanuts from their diet while pregnant and breast feeding and to delay eggs until two years and other allergens for even longer. This advice has now been withdrawn.

[As an aside, I’ve noticed I’ve typed “mother” about 100 times there without typing “father” or “parent”. The surveys only asked mothers, it’s not me being presumptuous!]

The science

Unfortunately, there doesn’t seem to be a scientific consensus. In part this is because of methodological difficulties around conducting studies on diet: Parents may report what they deem to be “good behaviour” rather than what they’ve done, they may delay certain foods because of personal beliefs even if investigators want them to give them, and in the case of a recent study, might just really struggle to get solid foods into very young babies! Many of the studies have also been observational, which means untangling whether the diet caused the allergy or the allergy caused the diet is often impossible.

Added to this, there are multiple factors to consider: nutrition, growth, digestive tract maturity, renal function, obesity, autoimmune disease. And then allergy, which itself is poorly understood. I love this honest comment from one editorial:

“Confused? So are we. And so are our patients. Practically, it seems that the timing of introduction of certain foods might matter…The food, dose, frequency, age of introduction, and heritable background of the child might all play important roles. And we do not yet have all the answers.”

What this means, is that you can find a study to support pretty much any position you would like to take. That makes it hard not to cherry-pick based on my own personal biases. So, here’s my best attempt at summarising what’s known.

Should we be avoiding allergens?

Previously it was thought that exposure to allergens early could prime the immune system to react to them, possibly even in the womb. While it seems some allergens do reach the baby in the womb, it now seems likely that low dose continued exposure to these allergens teaches the immune system to tolerate them, rather than react to them.

The scientific consensus is now that there is no evidence that delaying eating allergens like eggs, peanuts, wheat and shellfish past six months reduces the chance of allergies (as was previously thought). In fact, introducing them earlier may be protective.

Solids before six months?

In 2009, a consensus document from the European Food Safety Authority concluded that solids between four and six months in healthy infants is safe and does not pose a health risk. They concluded that at four months, the digestive tract and kidneys are suitably mature for consumption of solids. After about six months, the baby begins to need nutrition (particularly iron) from other sources.

In terms of autoimmune diseases, such as coeliac disease (here and here) and type 1 diabetes, there is some evidence that in children at risk of these conditions, introduction of gluten around four to six months might be ideal, with an increased risk of developing these diseases if gluten is before four months, and a smaller increased risk if delayed until after seven months.

The same may be true for allergies. Some recent studies have suggested that introducing foods between four and six months may reduce the chance of developing an allergy (eggs, peanuts, wheat, among others). Two recent prospective studies, the EAT  and LEAP studies, have provided more evidence of the benefit of introducing (and giving regularly) key allergens before the age of one, and in the case of the EAT study, before six months.

The results of the EAT study, while not astounding, were certainly interesting. When looking at only those who managed to stick to the protocol, significantly fewer babies who had solids from three months developed allergies to egg and peanut, than those who had solids from six months. Now, the numbers of mothers/babies who didn’t manage to stick to the protocol were quite high, and so there are some uncertainties around the results. But it does provide some useful evidence to suggest that introducing solids from three or four months may not cause allergies to these specific foods.

While this is important, there are other things to consider. The addition of food before six months will likely lessen the amount of milk consumed. As one study noted, for breastfed babies the perfect time to introduce solids may “depend on weighing an infant’s unique atopic risk factors against the many benefits of exclusive breastfeeding for six months”. That’s not something you or I are going to be able to do, and it’s not feasible to write it into a guideline. And that’s why the guideline is likely to stick at 6 months for a while yet.

That, and it would seem there are always people that introduce solids earlier than the guidelines. I’d be concerned that if you put the guideline at four to six months, you’d begin to slip back to the very early weaning of the 1970s.

And what if you formula feed? In all of the guidelines available, and most of the research, it is stressed that the ideal is that breast feeding is continued alongside complimentary food. For those who formula feed, the situation is perhaps even less clear. Though, certainly formula has nutritional benefit, the comparison between exclusive formula feeding for six months and solid food consumption is lacking.

What did I do?

I have really enjoyed introducing both my kids to solid foods. With both of them I was baby-led (please note the use of lower-case there). Girlbug, with her inefficient breastfeeding, skinny frame, early mobility and what I presume is her father’s over active metabolism started solids at five and a half months. Boybug, a more sedentary soul, started at just before six. Many more people told me Boybug would need solids earlier because of his size, but he seemed to have no problem maintaining his size on breastmilk alone.

Both have enjoyed their food, and have no allergies, though I am sure both these things are genetics rather than anything we have or haven’t done. We didn’t avoid any foods in particular, except obvious choking hazards, honey (due to the risk of infant botulism) and anything too salty or full of sugar (though that didn’t last long!!)