Too little iron in infancy can cause irreversible cognitive deficits. And iron deficiency can have no symptoms. It’s scary.
Yet the advice parents receive about their baby’s iron needs is complex, conflicting, and incredibly confusing.
My pediatrician, for example, takes a laid back approach. Her well-baby questionnaires ask whether my baby eats meat (a rich source of iron). But they do not ask how much or how often she eats meat, or about other sources of iron in her diet, like iron-fortified baby cereals. My pediatrician has never suggested giving her iron supplements or having her iron levels checked.
This is odd, because the American Academy of Pediatrics (AAP) recommends both. They recommend that fully or mostly breastfed babies receive iron supplements from 4 months of age until they start eating lots of iron-rich foods. They also recommend that all babies have their iron levels checked at 12 months of age.
“Given that iron is the world’s most common single-nutrient deficiency and there is some evidence of adverse effects of both ID and IDA on cognitive and behavioral development, it is important to minimize ID and IDA in infants and toddlers without waiting for unequivocal evidence. Controversies remain regarding the timing and methods used for screening for ID/IDA as well as regarding the use of iron supplements to prevent ID/IDA” — AAP, 2011
This is a huge discrepancy. Is getting iron into my baby no big deal? Or is it a reason to give my baby iron supplements starting at 4 months? Do I need to shovel baby cereals (which she is no fan of) into my munchkin several times a day? Or can I take a pass and figure if she eats some meat a couple times a week, she is going to be fine?
I turned to KellyMom, one of my favorite breastfeeding sites. But they muddied the waters further. KellyMom claims that iron supplementation is not only unnecessary, but potentially harmful. Taking in too much iron, they argue, lowers the amount of iron your baby absorbs from breast milk and thus, paradoxically, raises the risk of anemia.
Confused? I was too. Ultimately, I decided I did need to make sure my baby was eating iron-rich foods every day, but that she could pass on irons supplements.
Before I get into how I made that call, let’s back up a bit to talk about why babies do need lots of iron, starting around 4 months of age.
Why Care About Your Baby’s Iron Intake?
The short answer: You want to avoid iron-deficiency (ID) and iron-deficiency anemia (IDA).
Iron deficiency (ID) occurs when your body lacks sufficient iron stores. ID can happen quickly, as soon as iron intake falls or iron stores become depleted.
Over the course of weeks to months, ID can progress to Iron Deficiency Anemia (IDA), a blood disorder caused by a lack of red blood cells. Iron is used to generate red blood cells, and you need red blood cells to carry oxygen from your lungs to your muscles and brain. Anemia can therefore cause pale skin, shortness of breath, and fatigue.
Most of us know that iron used to carry oxygen in the blood and to the muscles and other organs in the body. But it is also used in the brain to for myelination (the coating neurons with a substance–myelin–that speeds up their ability to communicate) and to synthesize the neurotransmitters neurons need to talk to one another.
Because the body preferentially uses iron stores for the blood, ID alone, even in the absence of frank anemia, can affect your baby’s brain development.
This is likely why ID and IDA in infancy and early childhood, when the brain is growing rapidly, have been linked with motor delays and permanent, irreversible cognitive deficits.
When do I need to worry about Iron Deficiency (ID) and Iron Deficiency Anemia (IDA)?
Most full-term exclusively breastfed babies are born with enough iron stores to get them through the first 4 to 6 months of life. After 4 to 6 months, their stores become depleted, and they need to start taking in a significant amount of iron to keep up with their rapid growth and development.
(Babies born early can run through their stores before this time, and may need supplements from birth. If you have a preemie, this is definitely something to discuss with your care team.)
How likely is iron deficiency?
Iron deficiency is the most common nutrient deficiency worldwide. It is especially common in children under 5.
Iron deficiency is more common in developing nations than in developed ones. But even in the U.S., it remains common among fully and mostly breastfed babies like my daughter.
How common? It is hard to say. Estimates range widely. Some studies have put the rate of iron deficiency in breastfed babies in the U.S. as high as 1 in 6 [2,3]. Others suggest that the rate of true IDA in industrial countries is low, closer to 3% . Probably the best estimate comes from NHANES III, a nationally representative cross-sectional study of instants 6-4 months old conducted from 1988-1994, which found that about 1 in 10 infants exclusively breastfed for 6 months are iron-deficient .
Who is at risk for ID and IDA?
The risk for ID and IDA is determined by growth, how much iron your baby stored during pregnancy, and how much iron they take in from their diet.
Some of the major risk factors for ID and IDA in babies are:
Prematurity. Babies lay down roughly two-thirds of their total iron stores at birth during the third trimester of pregnancy, This means babies born prematurely, before 37 weeks, tend to be born with lower iron stores.
Premature babies also often experience catch-up growth, sometimes quadrupling their birth weights within a year. Because of their rapid growth, premature babies often run through already diminished iron stores at a faster rate than full-term babies, placing them at especially high risk for ID and IDA [2,3,6].
Babies born weighing under 2500 grams are at also higher risk of iron deficiency and anemia than full term babies.
(Whether and when to supplement babies born early and/or under 2500 grams depends on their postnatal care and blood test results. If your baby fits either category, you should talk to your pediatrician about making sure their iron needs are met. Some of these babies will need iron supplements from birth on.)
Being fully or mostly breastfed after 4 months of age. Contrary to what some popular breastfeeding sites claim (looking at you KellyMom), breastfed babies like my daughter are at higher risk for ID and IDA .
Breast milk does contain some iron, and the iron it contains is very well-absorbed. But there is just not very much iron in breastmilk, only an average of 0.2-0.4 mg of iron per liter. This is not enough iron to meet the needs of babies 4 to 6 months and older. Studies show that babies exclusively breastfed beyond 4 months have much higher chances of IDA than formula-fed babies 
Early cord clamping. Waiting a few minutes to clamp your baby’s umbilical cord gives your baby an extra month or so of precious iron stores. The placenta continues to pulsate for a few minutes after delivery. When clamping is delayed, these extra minutes allow more iron rich blood to transfer to your newborn.
All of the risk factors make me nervous about my daughter getting enough iron. She was born a little underbaked, at exactly 37 weeks; she is mostly breastfed, getting only occasional bottles of formula; and, because her umbilical cord was wrapped around her neck, not just once but twice, it was clamped as soon as she came out.
What about formula-fed babies?
Provided they were born full term and are fed an iron-enriched formula, fully formula-fed babies receive enough iron and are at very low risk of ID and IDA .
What about mixed-fed babies?
Your baby’s iron status depends on how much breast milk and how much formula he or she is taking in on a daily basis. If fewer than half of your baby’s feeds are from formula, the American Academy of Pediatrics advises iron supplementation from four months on, just as in fully breastfed babies.
Do we really know if anemia causes cognitive problems? Isn’t that correlation not causation?
Nearly all of the studies on the long term effects of IDA in human infants have been observational instead of randomized trials, and that means we cannot say definitively whether the link is causal [9,13].
That said, there is a strong circumstantial case for causation. Numerous studies, in developing and developed countries, and in a wide range of ethnic groups, show a strong link between anemia in early life and later cognitive and behavioral problems.
There are also sound biological reasons why lack of iron in infancy would affect later cognitive and behavior. The developing brain needs lots of iron for the coating of neurons with myelin (a process that happens during early infancy) and to synthesize neurotransmitters (the chemicals neurons use to talk to one another) . In the face of low iron, the body uses iron for the blood at the expense of the brain.
Finally, randomized trials in animals show long-term impaired cognition after IDA early in life.
How much iron does my baby need?
The recommended dose for babies under 6 months is 0.27 mg per day. For babies 6 months and older, the recommended amount is 11 mg per day.
Wait a second, does my babies need for iron jump that sharply at 6 months?
No. Of course not. A full term baby’s iron needs increase gradually during their first year of life as iron stores become depleted.
But wait, I still do not understand why iron needs skyrocket at 6 months.
Well, the short answer is that they don’t.
Medical organizations calculate a baby’s iron needs differently during the first half of the first year than during the second half. This gives the false appearance of a sudden jump, when instead full-term babies’ iron needs climb slowly from about 4 months on, as their birth stores become depleted.
For babies younger than 6 months, iron needs are calculated by heuristic. The average amount of iron a fully breastfed baby receives is assumed to be the amount needed.
(Of course, the amount of milk babies drink varies, as does the amount of iron that in different mama’s milk, so these recommendations are tantamount to a giant shrug, like saying, if you’re baby is full term and under 6 months, do not worry about iron.
This would be great, if it were true. Unfortunately, this assumption is almost surely wrong, which is why the American Academy of Pediatrics recommends iron supplements for exclusively breastfed babies from 4 months on.
For babies 6 months and older, researchers used a “factorial approach” to calculate daily iron needs, by estimating the amount of iron lost and the amount of iron needed for growth.
In short, the daily requirement of 11 mg after age 6 months is based on estimates, not data. 11mg is a staggering amount of iron to take in from complementary foods. (Iron-enriched formula provides about 12 mg/L, so formula fed babies do get this amount).
This recommended amount also assumes a very low absorption rate, of about 5%. This is about how much iron babies absorb from formula, but less than they absorb from a carefully planned iron-rich diet.
Are you suggesting my older baby does not really need 11 mg of iron?
Sort of. This amount is just a guideline. And thank goodness, because who can shovel in that much iron-fortified cereal to a 7-month-old baby? Especially when only about a tenth of the what you try to feed them ends up in their mouths, and the rest in their hair. Maybe if babies could absorb iron through their scalps.
But more seriously: What matters is not how much iron your baby ingests, but how much ingested iron your baby absorbs.
If you follow some simple tips to enhance your baby’s absorption of iron from solid foods, they probably do not need to meet the 11 mg of iron requirement.
Iron in food comes in two forms: heme and nonheme. Animal sources of iron, like beef, chicken, and fish, contain heme iron, whereas plant-based sources, like legumes, kidney beans, and raisins, contain non-heme iron.
This matters because heme iron is about 2-3 times better absorbed than as nonheme iron.
Fortified cereals and iron-enriched formula contain non-heme iron, so your baby absorbs only about 5-10% of the iron in these foods.
The good news is you can boost your baby’s absorption of nonheme iron with some careful food pairing. Giving your baby a nonheme rich food like lentils with a food rich in vitamin C or a source of heme iron can double to quadruple the amount of nonheme iron your baby absorbs.
(Breastmilk represents an special case because contains a protein known as lactoferrin. Lactoferrin binds to the iron breastmilk and helps your baby absorb it. Babies absorb anywhere from 50-80% of the iron in breast milk . Lactoferrin also blocks the growth of pathogenic bacteria like E. Coli by depriving them of iron .
Although the iron in breastmilk is very well absorbed, it contains too little iron to meet your baby’s needs from about 4-6 months of age.)
There’s one more important wrinkle: Many foods contain substances like phytates, oxalates, and polyphenols that inhibit iron absorptions. (This website provides a great summary of absorption-enhancing and absorption-inhibiting foods.) Calcium also inhibits iron absorption, which is why it is a good idea to serve meat and milk separately, even if you are not keeping kosher!
And this brings us to the worst offender: Cow’s milk. Cow’s milk can cause mild bleeding in the intestines, leading to a loss of iron through blood loss. This is the major reason all major medical organizations recommend that babies not start drinking cow’s milk until at least one year of age. It is also why young children should not exceed 24 oz. of cow milk per day .
But if iron-deficiency anemia in infancy is such a big concern, why not supplement from 4 months on, just to be on the safe side, as the American Academy of Pediatrics recommends?
Unfortunately, universal supplementation also carries risks for your baby.
First, if your baby has adequate iron stores, iron supplementation is not only unnecessary but also potentially harmful. Iron is a pro-oxidant. Taking in too much of it increases oxidative stress.
Babies eating iron-rich cereals, for example, have higher levels of fecal calprotectin, an indicator of oxidative stress in their intestines. (These markers increase less in babies who eat meat or pair their baby cereals with fruit–another good reason to pair iron-rich foods with foods rich in vitamin C.)
Second, younger babies have trouble regulating their absorption of iron  Starting around 5 to 6 months of age, iron absorption corresponds to iron stores–our bodies take in more iron when we are depleted, and less when we are iron-sufficient. Because of this, supplementation in early infancy risks potential overload. And just like iron-deficiency, iron overload can impair growth, raise the risk of infections, and harm cognitive development.
Third, iron supplementation can alter your baby’s gut microbiome, increasing “bad” bacteria like pathogenic E. coli, and causing diarrhea [19,20,21,22].
Finally, taking in too much iron can affect the absorption of other important nutrients for your baby, like zinc . This is especially a concern because many iron-fortified baby cereals are not enriched with zinc. Breastmilk provides enough zinc for the first few months of life, but like iron, not enough for the second 6 months of life. Meat provides both zinc and iron, as do some baby cereals, like Cream of Wheat and Happy Baby. If your baby’s main source of iron is cereals, be sure to check your labels. They should contain zinc and iron.
Can you boost the amount of iron in your breast milk by upping your own iron intake?
No. Although the amount of iron in breast milk varies from woman to woman, it is not affected by the amount of iron in your diet.
If you do fail to take in enough iron while breastfeeding, then your iron stores will become depleted, placing you at risk for anemia. But the amount of iron in your breast milk will remain the same.
There is something that can affect your baby’s absorption of iron, though. And sadly, it is my beverage of choice: Coffee. Drinking a lot of coffee may lower the amount of iron your baby absorbs from your breast milk. One study found that drinking large amounts of coffee, more than 3 cups a day, corresponded with worse iron status in breastfed babies . Animal studies back this up, finding similar effects of coffee on iron status. Fortunately, this is not due to the caffeine (so you can still get your caffeine fix elsewhere), but due to the chlorogenic acids found in coffee, which pass into breast milk and hinder iron absorption.
Why is breast milk so low in iron?
Based on the belief that breast milk is the “perfect food” for babies, some breastfeeding advocated suggest that babies must not need much iron, or breast milk would have more of it.
This is nonsense. After all, evolution often does not arrive at “perfect” solutions. Human childbirth is a great example. Evolution had to balance baby’s having big heads with mom’s narrow hips needed for walking upright, and the compromise it struck is why human labors are far longer, more painful, and much more dangerous than those of other mammals.
Evolution likely also struck a compromise when it came to iron in breast milk.
On the one hand, iron deficiency can affect long term cognitive development. On the other, having too much iron can cause problems, leading to diarrhea, which can be deadly in small babies, and boosting the risk of malaria among children living in malaria-endemic areas.
Evolution provided a solution for early infancy, by babies having lay down lots of iron during pregnancy, and by adding lactoferrin to breast milk to make sure your baby–and not your baby’s gut bacteria–gets what little iron breast milk contains.
It is in later infancy and early childhood, when lack of iron becomes a concern.
But remember, in our evolutionary past, no one was recommending exclusive breastfeeding beyond 4 months. And babies also had a lot of contact with soil, which contains iron.
The Bottom Line
Exclusively breastfed babies start to run out of iron at 4 months of age . Given this, once your baby is showing signs of being ready for solid foods, it makes sense to start introducing iron-rich solids, paired with good sources of vitamin C like strawberries or oranges, between 4 to 6 months of age.
Note, though, that introducing lots of foods low in iron is a no-go. Low iron foods can reduce your baby’s ability to absorb the iron in breast milk and raise their risk of ID. Cow’s milk in particular should be avoided, because it can cause bleeding in your baby’s intestines, leading to additional iron loss .
(Not sure if your baby is ready for solids? Alice Callahan over at Science of Mom has an excellent post how to tell whether your baby is ready to meet this amazing milestone.)
As for the daunting 11 mg daily requirement? It assumes a very low rate of iron absorption. So if you continue to breastfeed (which supplies about half of your baby’s iron needs), and take measures to enhance your baby’s iron absorption, such as pairing iron-rich foods with those rich in vitamin C, I would not worry about hitting this target.
What about the guidelines to breastfeed exclusively for 6 months, as the World Health Organization and the American Academy of Pediatrics recommend?
As I detail here, the recommendation to exclusively breastfed was based entirely on the needs of babies in the developing world. There access to clean water and safe food sources can be limited, making formula dangerous, and diarrhea is often deadly. Prolonged exclusive breastfeeding mitigates these risks, while providing an important form of birth control for women who lack access to other forms of contraception.
In the developed world, however, no compelling evidence shows that exclusive breastfeeding for 6 months is superior to exclusive breastfeeding for 4 to 6 months. If anything, recent evidence tilts in the opposite direction. Exclusive breastfeeding for 6 months raises your baby’s risk of iron deficiency and anemia. As I discuss in an earlier post, it may also raise their risk of food allergies.
If you have access to a safe food supply and clean water, it a good idea to start iron-rich foods in this 4 to 6 months of age window.
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