There was a study published recently comparing iron levels in babies exclusively breastfed for 6 months to those who started solids at 4 months. Here are a couple of articles about it:
Babies breastfed for 6 months may have lower iron levels
Starting Solids: Introducing Cereal At 4 Months Can Boost Babies' Iron Levels
They seem to be saying it's better to start solids at 4 months, don't they? But if you take a closer look at the text...
Okay, complementary foods starting at 4 months led to higher iron levels at 6 months. What were the complementary foods?In the study, mothers of 100 infants in Iceland who were exclusively breast-feeding their babies were randomized to begin giving other foods at either 4 months or 6 months old. The researchers... measured the babies' growth rates and iron levels when they were 6 months old.
Results showed that higher iron levels were seen in the infants who began eating other foods at 4 months old.
I.e. mostly iron-fortified cereal.For the babies given other foods, the main source of iron was infant cereal, though infant formula and fruit purees also contributed.
But, while the babies given complementary foods had higher iron levels,
The researchers' conclusion was "The biological importance of this finding remains to be determined."Both groups of babies had sufficient iron levels, and there were no differences in rates of anemia, the researchers said.
There was no difference between the groups in terms of the babies' weight gain or growth.
So, to sum up,
- Babies who are given supplemental iron have higher iron levels
- These higher iron levels don't appear to make any difference to babies' health