Sunday, January 9, 2011

Science Sunday: Purées vs. Lumpy Foods

Today I'd like to revisit something that I mentioned earlier this week, namely that we've decided to largely skip purées in favor of introducing our daughter to whole foods that she can grasp on her own, a practice known as "baby-led weaning."

A friend asked, "what does the actual research say about first foods to give babies?  Is there any benefit--or reason--to giving rice cereal and the like, rather than fruits or vegetables?"

I had been given the same advice by our pediatrician:  that the best thing to start with was rice cereal, and then to advance slowly through single-ingredient fruit and vegetable purees, introducing a new one every 4 to 5 days.  But, he cautioned, "parenting is more of an art than a science."

Indeed, the advice given by our pediatrician is the recommendation by the American Academy of Pediatrics Committee on Nutrition (1).  The reason given for introducing rice cereal and puréed meats first is two-fold: 1) they are unlikely potential allergens, and 2) store-bought rice cereal is artificially fortified with, and meats are naturally high in, iron.  The thought is that infants who are exclusively breast-fed can no longer get adequate iron from breast milk, and their own reserves may have run out, by about 6 months of age.

It may be helpful to know that UpToDate, a well-regarded online reference for national recommendations in medical practice, labels the standard "rice cereal and single ingredient purée" recommendation a Grade 2C recommendation.  In their rating system, Grade 2C refers to a "very weak recommendation;" it is based on "low-quality evidence," including evidence from "observational studies,  unsystematic clinical observations, or from randomized, controlled trials with serious flaws."  Indeed, the only type of research I was able to find to support this recommendation consisted of observational studies demonstrating that some, but by no means all, mothers in the United States choose to introduce solids in this way.  I'm not even going to bother with citing those studies; they really only show that that's what some people do, not that that way is associated with any better outcomes.

The evidence that exclusively breastfed babies require supplemental iron is slightly stronger in comparison, at least based on calculations (2) of how much iron babies need per day, the size of their iron stores, the amount of iron available in human milk, and the bioavailability of iron in human milk (how much of that iron can actually be absorbed).  Going by all of these estimates, it seems like breast-fed babies should require supplemental iron after about 6 months of age from foods other than breast milk in order to avoid iron deficiency anemia (low levels of red blood cells, which could lead to growth restriction).

HOWEVER. Actual observational studies of mothers who are breastfeeding past 6 months are by no means conclusive.  One small study (n=4) studied infants who were exclusively breastfed from 8 to 18 months; all of them had normal iron status (3).  A somewhat larger study (n=30) similarly found that exclusive breastfeeding (EDIT: meaning no formula, cow's milk, or iron-fortified cereal supplementation), as long as it continued, protected infants from anemia, although once breastfeeding had stopped--even if it had continued for a long time--those infants who were not given iron-fortified or high-iron content foods were likely to become anemic (4).  In short, there's not much actual evidence that infants who are being exclusively breastfed are in great danger of becoming anemic; giving iron fortification is largely a matter of playing it safe.  [Note that the amount of iron in human milk does decrease with increasing duration of lactation, and the amount of iron available in breast milk varies a lot from one woman to the next--furthermore, giving iron supplements to mom doesn't change how much iron is available in her milk!**]  Given the universality of the recommendation for iron supplementation, I am slightly shocked by the paucity of actual evidence.  Someone needs to get out there and do a good randomized controlled trial in this area!

OK.  So here's where we are:  there's virtually no evidence that starting with rice cereal and purées offers any advantages, and I couldn't find much good evidence that breastfed babies require iron supplementation via fortified rice cereal, either.  So what about the alternative?  Is there any benefit to be had by introducing lumpier, more whole foods, earlier?

There isn't much work in this area either, to be honest.  I really only found one relevant study (5), and was comforted that an expert in the area of children and food textures who was forwarded my post about "baby-led weaning" sent back the same study for reference.  The authors of this UK study looked at children who had first been given "lumpy" or chewy foods at ages before 6 months, between 6 and 9 months, and after 9 months, and examined correlations between the age of introduction and the frequency of eating different types of fruits and vegetables much later, at 7 years old.

More of the children who had an earlier age of introduction of lumpy solids (before 9 months) later consumed all 10 types of fruits and vegetables.  More of the children with the earliest age of introduction (before 6 months) later consumed green leafy vegetables.  Not only did children who were introduced to lumpy foods at a younger age eat more varied diets later; also, children who were NOT introduced to lumpy foods till after 9 months were more likely to have problems with eating at age 7 years.  Problems included "not eating sufficient amounts, refusal to eat the right amounts, and being choosy with food."  Note that the study did control for standard demographic variables like mother's level of education, as well as things like duration of breastfeeding.

In short, I think my pediatrician's parting comment to me about introduction of solids, that "parenting is more of an art than a science," is about right.  Given the (surprising!) lack of good science in this area, it makes sense to do what seems right and good for you and your child.  There is some evidence that there could be advantages to introducing lumpy, real foods earlier, in the form of a less picky eater later on.  And if you still are worried about your breastfed baby's iron levels?  You could always try giving her what my baby had for dinner last night.  A steamed carrot, a steamed piece of cauliflower, toast...and pâté!  

(1).  Committee on Nutrition American Academy of Pediatrics. Complementary feeding. In: Pediatric Nutrition Handbook, 6th ed, Kleinman, RE (Ed), American Academy of Pediatrics, Elk Grove Village, IL 2009. p.113.

(2).  Griffin IJ, Abrams SA.  Iron and Breastfeeding.  Ped Clinics North Amer.  2001; 48: 

(3).   McMillan JA, Landaw SA, Oski FA. Iron sufficiency in breast-fed infants and the availability of iron from human milk. Pediatrics. 1976; 58:686-691.

(4).  Pisacane A, De Vizia B, Valiante A. Iron status in breast-fed infants. J Pediatr.  1995; 127:429-431.

(5).  Coulthard H, Harris G, Emmett P.  Delayed introduction of lumpy foods to children during the complementary feeding period affects child's food acceptance and feeding at 7 years of age.  Matern Child Nutr.  2009; 5: 75-85.


  1. I recently wrote a post about our experience with baby-led weaning with real foods. My 10-month old has never had cereal (I've never even purchased any cereal or baby food).
    Joshua has had beef, pork, chicken, turkey, salmon and a few different kinds of white fish. He's getting plenty of iron from meat, and it's my understanding that the iron in meat and breastmilk is better absorbed than fortified cereals or formula.
    I tend to look at things from an evolutionary perspective, and I know our ancestors didn't evolve to eat processed rice cereal as a first food!

  2. Interesting, thanks! Wish there was more data...

  3. This is a great post! We did Baby Led Weaning starting a little after 7 months with our daughter and have loved it! She was never spoonfed purees and never had rice cereal. The iron issue can also be solved by delaying cord clamping after birth to make sure the baby receives all of it's own blood and iron stores.

  4. Isn't it fun? I love that my daughter's eating all these foods that I never tried till my 20's...goat cheese, bruschetta, curries. Every meal's an adventure for her!