You may have heard about a study published in Pediatrics last week (Maguire et al. 2013) showing an association between iron deficiency and breastfeeding beyond a year. If you’re breastfeeding a toddler, or considering it, you might be wondering if you should be worried about iron deficiency. There is very little research on breastfeeding beyond a year in developed countries, so this study is worth a closer look. (If you’re interested, I’ve written before about some of that research, my own reasons for choosing to breastfeed beyond a year, and my experience of weaning my two-year-old.)

What This Study Shows

This was a cross-sectional study of children ages 1-6 in Toronto, Canada. Blood samples were taken from 1647 children, and their mothers were asked, “How long has your child been breastfed?” We always have to be cautious about studies based on parental recall. However, research shows that mothers actually answer this question with good accuracy (Li et al. 2005). Of the children in this study, 93% had been breastfed at all, and median breastfeeding duration was 10 months. Twenty-seven percent of children were breastfed for more than one year, and 4% breastfed for more than two years.

The children’s blood samples were analyzed for serum ferritin and hemoglobin. Serum ferritin reflects the amount of iron stores available for use by the body, so it can be used to assess iron deficiency. If an iron deficient child also had low hemoglobin, he was diagnosed as having iron deficiency anemia. In this study, the prevalence of iron deficiency was about 9%, and 1.5% had iron deficiency anemia, findings similar to other studies in developed countries (Baker et al. 2010, full text here).

This study showed that kids that were breastfed for longer were more likely to be iron-deficient. Each month of breastfeeding beyond baby’s first birthday increased the risk of iron deficiency by about 5%. Children who were breastfed for longer than a year were estimated to have 1.7 times the odds of being iron deficient than those breastfed for less than a year. The researchers corrected for several potentially confounding factors: age, gender, birth weight, BMI, ethnicity, household income, day-care attendance, age of introduction of solids and cow’s milk, and current daily intake of cow’s milk. Children with iron deficiency were also more likely to be heavier at birth (bigger babies have higher iron requirements), younger (meaning that older kids seemed to have recovered from iron deficiency), and to be drinking more cow’s milk (something I wrote about here). Breastfeeding duration was not associated with iron deficiency anemia, which would indicate a more severe deficiency.

An obvious limitation to this study was that the observed relationship between breastfeeding and iron deficiency was just a correlation. There are other factors that could come into play that weren’t examined, like timing of umbilical cord clamping and how much iron these kids were getting from their diets or supplements. For example, it’s possible that moms who breastfeed longer are less likely to give their toddlers a multivitamin or other iron supplement. It that case, it wouldn’t be the breastfeeding that increased the risk of iron deficiency, but rather something else about moms who choose to breastfeed beyond a year. This is a major limitation, but to be fair, almost every study that shows positive outcomes for breastfeeding has the same problem.

Why be concerned about iron deficiency?

Iron is a mineral essential to life in all animals. Most of the iron in the body is used to make hemoglobin and myoglobin, so iron is really critical for oxygen transport to all tissues of the body. Iron is also part of several enzymes involved in energy metabolism. Every cell in the body requires iron, but blood, brain, and muscle cells are the ones that really suffer if there isn’t enough iron around. A person with severe iron deficiency will develop iron deficiency anemia, one of several types of anemia.

Iron deficiency in the first years of life, even without anemia, has been associated with cognitive, motor, and behavioral deficits (Lozoff et al. 2006). There are a lot of confounding variables in these studies, because kids that are iron deficient are likely to have other disadvantages as well. However, there are mechanisms for a causal relationship established through animal research (McCann and Ames 2007). So there’s some controversy as to just how scared we should be about iron deficiency, but given that we’re talking about brain development of our kids and that iron deficiency can be corrected with dietary changes, I think we should pay attention to it.

The current study was the first to look at the relationship between breastfeeding and iron in toddlers. Many studies have shown that exclusively breastfed babies are at higher risk for iron deficiency during late infancy (reviewed by Baker et al. 2010, full text here). Human breast milk is low in iron, but babies are usually born with enough iron, passed from mom via the placenta, to last for about the first six months. Delayed cord clamping at birth can extend the iron stores by another month or two. If breastfed babies aren’t getting some good iron-rich solid foods by late infancy, they can become iron-deficient.

So should I be worried about my breastfed toddler?

Worried? I wouldn’t go that far. Instead, I’d say you should be alert to the possibility that your breastfed toddler could become iron deficient. The good news is that it isn’t that hard to prevent iron deficiency if you’re mindful about nutrition.

How can I ensure that my breastfeeding toddler is getting enough iron?

Why would a breastfed toddler be at greater risk for iron deficiency? The study at hand doesn’t tell us, but I’ll speculate for you. Breast milk doesn’t have much iron. Yes, the iron in breast milk is well-absorbed, but there is still very little there. That’s probably a good thing for an infant (more on that here), but it means that breast milk really can’t provide complete nutrition for a growing toddler. Toddlers need good iron-rich sources of solid foods in their diets.  If a toddler fills up on breast milk, then it may be challenging for him to get balanced nutrition.

So how can you make breast milk part of a balanced diet for a toddler?

• Talk with a health care provider about your child’s risk for iron deficiency. Consider having him tested so that you know if you should be concerned. If he does test low for iron, then depending on the severity, your pediatrician might recommend a supplement or suggest trying to correct the problem through diet.

• Include lots of iron-rich foods in your toddler’s diet, like meats, legumes, whole grains, green veggies, and dried fruits. Of course, toddlers can be picky, so this may be easier said than done. Know that it may take many low-pressure exposures for your kid to be ready to try new foods. Iron-fortified breakfast cereals are a good option for more skeptical eaters. You can find a list of iron-rich foods, as well as strategies for increasing iron absorption, in this post.

• Cow’s milk inhibits iron absorption. If your toddler is breastfeeding AND drinking cow’s milk, consider limiting cow’s milk to just one or two cups per day (or even none at all). Of course, without cow’s milk, you’re losing a good source of vitamin D (also low in breast milk), so you may want to consider a vitamin D supplement.

• Evaluate if breastfeeding is getting in the way of your toddler eating well at meals. This might be an issue if you’re breastfeeding on demand throughout the day. Toddlers do better with eating if they have structure around their meals and snacks. To you and your toddler, breast milk is probably much more than a food. It is comfort, closeness, and a moment of quiet together. But, it is also calories, and there’s no getting around that. Toddlers who snack on breast milk throughout the day might not come to the table hungry and be ready to eat a variety of foods with the rest of the family. If that seems like it might be an issue for your child, consider fitting breastfeeding into times of day when it is unlikely to interfere with eating, such as before nap and bedtime.

If you’re breastfeeding beyond a year, what do you do to balance breast milk and foods in your toddler’s diet?