If there were a parental quiz, this would be one of the infancy extra credit questions: Why is it that babies can
drink infant formula (usually made from cow’s milk) at 10 months of age but they can’t drink whole milk (also from cows) until after their first birthday? What’s the difference?
What’s the Issue?
Realistically, almost all infants drink cow’s milk. If you are a breastfed baby, the cow’s milk comes to you via the breast and your mom’s last linguini with parmesan or decaf skinny latte. If you are a formula-fed infant, it comes from Nestlé Good Start, Enfamil Lipil, Similac Advance, or one of the other cow’s milk-based infant formulas. Seeing the obvious similarity, patients sometimes ask me why they can’t just switch to whole cow’s milk earlier than the one year birthday. It certainly would be cheaper. Is there a downside?
Well, the answer has little to do with vitamin content, fat content, or mad cow disease—the initial guesses my patients share. Instead, low blood counts and anemia (a condition characterized by low levels of red blood cells) are truly of concern.
Consider the Numbers
In the 1960s, the prevalence of anemia in the American one-year-old population was 15 to 30 percent. Today, the prevalence of anemia hovers somewhere around three percent. The major change? The introduction of iron into infant formulas and the strong recommendation by pediatricians that infants drink breastmilk or iron-fortified formula until their first birthdays, both around 1971.
Some of the seminal thinking on this subject came from Dr. Howard A. Pearson, MD, in New Haven, Connecticut. In his studies, he and his colleagues found that cow’s milk as the major source of nutrition in the infant diet before one year of age was associated with more significant anemia. The cause, we now know, seems to be an irritation of the intestinal lining and a resulting low-grade leakage of blood into the stool. Older children are much less likely to have this problem.
Dr. Pearson found that the earlier the introduction of cow’s milk, the more severe the anemia. For example, a six-month-old switching over to whole milk has a much larger risk of severe anemia compared to a one-year-old making the same switch. Again, the younger child just hasn’t developed the intestinal maturity to handle the whole milk protein.
What Parents Should Know
What makes cow’s milk formula different from just regular whole cow’s milk? For one, it is specially heat treated, which denatures its protein slightly. This makes the protein, which might normally be irritating to some infant tummies, much more tolerable—and therefore more generally nutritious. It is also iron fortified. This small boost of iron is critical in repleting an infant’s iron stores, which rapidly decrease after birth due to multiple factors, including decreased infant production of new red blood cells and increased turnover of red cells in the infant body. And unlike some of the rumors you’ve heard, it is not nearly enough iron to cause symptoms such as constipation.
Then parents ask me, “But grilled cheese or macaroni and cheese is considered okay at nine months of age for most infants, right? Why is this? Isn’t this cow’s milk, too?” In this case it is a matter of volume, I tell them. A small cheese meal or snack is a tiny proportion of an infant’s feedings at this age, whereas 24 ounces or more of whole milk in bottles over the course of a day ends up being too much. An excess of cow’s milk protein can irritate an infant’s intestine and cause microscopic blood loss. This blood loss is too small in amount for parents to see, but enough for babies to lose significant amounts of iron over time, becoming anemic.
Anemia may seem like a relatively minor issue, but babies who are anemic become older children with anemia. And chronically low blood counts in older kids can be associated with fatigue, heart issues, and learning problems. It just makes sense to take simple steps to prevent anemia at this early age.
What the Docs May Do
Most doctors would agree that even a three percent risk of anemia is too high for your child. Your pediatric provider will likely check a measure of iron stores at your baby’s one-year checkup. If there are other risk factors (like prematurity or maternal anemia), your provider may check a blood count well before the first birthday. Blood counts can be checked by a finger stick in the office (a hemoglobin) or a trip to the local lab (for a hemoglobin or complete blood count—called a “CBC”). Those infants failing their screening will typically be placed on some form of iron supplementation. When necessary, iron treatment is usually prescribed for a three-month period.
Most pediatricians will ask screening questions for lead exposure at the one year visit, as well. Lead intoxication is one of the infrequent causes of anemia in toddlers. Testing for lead may be performed at the same time.
Remember that if your infant has visible blood in the stool, this may represent more than just a minor protein overload issue, as discussed before. Talk to your pediatrician. Issues to think about include a fissure or cut around the anus (which can happen after the passage of a particularly large or hard poop) or a true milk protein allergy.
More 10th Month Health Help
Even the most confident parent has concerns about her child’s health and wellness from time to time. (If you have any pressing concerns or questions about your baby’s health, please check with her healthcare provider.)