Introducing Solids: Is It Best to Wait Until 6 Months?

In 2005, the American Academy of Pediatrics (AAP) changed their recommendations from gradually introducing solids between 4 and 6 months of age to exclusively breastfeeding for “about the first 6 months of life. For the first 6 months “your baby”, they assert, “needs no additional foods (except Vitamin D) or fluids unless medically indicated.”

You might think that these recommendations were updated because of a new evidence showing substantial benefits for the baby of delaying the introduction of solids.

But, nope, this is not the case. Instead, these changes were motivated by studies showing an absence of harm to the baby and some minor potential benefits for the mother.

The World Health Organization was the first major medical organizations to recommend exclusive breastfeeding for 6 months, for reasons they outline in a 2002 research review (updated in 2007):

1. No evidence exclusive breastfeeding for 6 months results in poor growth
2. No apparent increase in the risk of allergies*
3. A longer period of lactation-induced infertility, about an extra month on average
4. Greater postpartum weight loss between 4-6 months, about a pound on average
5. Lower risk of illness for the first six months, and possibly throughout the first year

* (Since this review was published, new evidence suggests delaying solids until 6 months may increase the risk of food allergies. More on this complex topic below.)

When weighing the pros and cons of exclusive breastfeeding for 6 months, the social and environmental context matters. The WHO crafted its guidelines to maximize health outcomes in both developing and developed nations. But benefits that have a large public health impact in the developing world, where access to basic medical care, birth control, clean water, and nutritious food is limited and inconsistent, can have little or no impact in the developed world.

Benefits of Exclusive Breastfeeding for Six Months

For mothers living in the developed world, the benefits of exclusive breastfeeding for 6 months are small, arguably negligible.

We have been blessed with access to birth control, so lactation-induced infertility is not a critical means of pregnancy prevention and birth spacing.

And, when it comes to weight loss, although almost every mother I know would gladly shed an extra pound or 2 of baby weight, the benefit is really small, just an extra a pound on average. Surely there are other activities that do not require 8-hours a day, round-the-clock efforts that would be just as effective forms of weight loss.

Certainly neither of these two benefits warrant the stress placed on introducing solids “at the right time.”

Of the reasons given by the WHO, the only truly persuasive one is a reduced risk of illness for the baby during its first 6 to 12 months of life. Here again, though, there are important differences between the developing and the developed world.

In the developing world, exclusive breastfeeding for 6 months is literally life saving. Within the 42 nations with the highest child mortality rates, widespread adoption of exclusive breastfeeding for 6 months would prevent an estimated 13% of the deaths of children under the age of 5. This is a larger percentage than would be saved with improved access to antimalarial medication or antibiotics.

Within the developed world, the picture is more nuanced. Here, completely weaning from breast milk before 6 months, or introducing solids before 4 months, or introducing formula before 6 months substantially increases the risk ear infections, diarrhea, pneumonia, and bronchitis.

But gradually introducing solids between 4 to 6 months while continuing to breastfeed does not. Studies that compare the outcomes of infants who were exclusively breastfed until 6 months (EBF or exclusively breastfed) with those who were exclusively breastfed for at least 4 months and then partially breastfed thereafter (MBF or mostly breastfed) find that 6 months of exclusive breastfeeding neither harms nor benefits growth and development.

The only apparent benefit of delaying until 6 months was a 25-50% lower risk of diarrhea in the first year of life. The effects on ear infections, pneumonia, and bronchitis were unclear: A couple of observational studies found a lower risk, but the majority of studies, including the only two randomized controlled trials, found no effect. And longitudinal study conducted in Belarus found no differences in weight, height, BMI, asthma, allergies, or other illnesses by age 6.

“Exclusive breastfeeding for six months does not seem to confer any long-term (at least to early school age) protection against obesity or allergic disease, nor any benefits in cognitive ability or behaviour, compared with exclusive breastfeeding for three to four months with continued partial breastfeeding to six months.”  – Kramer & Kakuma, 2012

Costs of Exclusive Breastfeeding

Lower Iron Status. EBF infants tend to have lower iron levels than mixed fed or formula-fed infants. Two randomized controlled trials, one conducted in Honduras and the other in Iceland, found significantly higher iron levels among MBF than EBF infants. Reassuringly, at 6 months of age, iron levels in both groups remained within the normal range, and the EBF infants were not more likely to be iron deficient or to develop anemia.

Still, iron needs rise sharply in the second half of the first year. By then newborn iron stores have been depleted. Lower iron status in the first six months therefore places EBF babies at higher risk of iron deficiency as they age. This is why the CDC considers “breastfed babies who after age 6 months are not being given plain, iron-fortified cereals or another good source of iron from other foods” to be at high risk for iron deficiency and anemia.

Increased Risk of Food Allergies. On this point, the advice given to parents has seesawed from it is best to delay solid foods, especially highly allergenic ones, to it is best to introduce these foods early, between 4 to 6 months. This is because the evidence behind the advice is of poor quality and inconsistent. A handful of observational studies find that early introduction increases the risk of allergies. A comparable number find that late introduction increases the risk. And not all of the studies find when solids are introduced matters at all.

Some researchers to speculate that there is something of a sweet spot in infancy, between 4-6 months of age, when introducing solids lowers the risk of allergies. This protective effect may be strongest for peanuts and cooked whole eggs. But until proper clinical trials have been done, it seems wise not to make too much of these findings. (UPDATE: A randomized controlled trial has now shown that introducing peanuts before 1 year of age lowers the risk of a peanut allergy substantially. More on this study here.)

The AAP no longer recommends waiting to introduce solids until 6 months or later to reduce the risk of allergies, and instead advises waiting until at least 4 months. And of course, this statement on solids and food allergies conflicts with guidance the AAP gives elsewhere to exclusively breastfeed for 6 months.

Conclusions

Like so many parenting decisions, the actual evidence suggests that we can all relax a bit. For those of us lucky enough to live in the developed world, introducing a small amount of solids between 4 to 6 months is unlikely to harm our babies, and equally unlikely to benefit them.

That said, when giving your baby solids before 6 months, it makes sense to provide small amounts. The immune benefits of breast milk are dose-dependent: the more milk the baby takes in, the greater the protection from illness. This is why solids during the first year should not be used to replace but to supplement breastfeeding. And when introducing solids, especially to exclusively breastfed babies, it makes sense to emphasize iron rich foods like broccoli, meat, eggs, fish, and fortified cereals.

Here is most sensible statement I found on the 6-month rule, from a review article in The BMJ, the flagship journal of the British Medical Association:

“From a biological perspective, the point when breast milk ceases to be an adequate sole source of nutrition would not be expected to be fixed, but to vary according to the infant’s size, activity, growth rate, and sex, and the quality and volume of the breast milk supply.”  – Fewtrell, Booth, & Lucas, 2010

When did you first introduce solids? Did the risk of allergies or infections play a role in your decision?