Baby-led weaning and breast milk vitamin D

Baby knows best?

Can babies make better food choices for themselves than Mom and Dad?  A very interesting new piece of research suggests the answer is “Yes.”  Weaning is the period when babies transition to eating solid food, sometime around 6 months of age.   Parents and health professionals can have very definite opinions about what foods to offer during this time.  Small items that require chewing, like grapes or pieces of meat, should be avoided, since young babies can’t chew very well.  Typically soft or pureed foods, like cooked cereal, rice or peas, are offered.

Drs. Ellen Townsend and Nicola Pitchford compared food choices of two groups of babies during weaning:

  1. Baby-led
  2. Spoon-fed by parents

They found that the baby-led group had a definite preference for carbohydrate foods like bread or other grain-based items, while the spoon fed group had a clear preference for sweets.  The baby-led group actually preferred all other types of food — vegetables, fruit, protein — over sweets, when compared to the spoon fed group, although those statistics weren’t significant.  They also had lower average BMI.  More of the spoon fed babies were classified as obese.

Why would this be?  The researchers speculate that babies like to learn about the textures and flavors of new foods.  When babies are spoon-feeding pureed foods, it’s easy to over feed, and that stuff goes down pretty easy.  No need for the baby to try chewing or gumming or handling pureed food.  The parent just spoons it in the baby’s mouth.  It makes sense in a way.  Tens of thousands of years ago, Mother Nature had to prepare babies to learn about new foods as quickly as feasible, when spoons and pureed baby food didn’t exist.

How much vitamin D should babies be getting?  And does breast milk have enough?  Orthodox thinking says that breast milk is deficient and breast fed babies need to get 400 IU daily, typically as infant vitamin D drops.  The interesting part of this conventional “wisdom” is that breast milk levels of D depend on the mother’s blood status.  And since it’s now becoming apparent that many people are deficient to begin with, then “deficient” breast milk levels might just be a reflection of the mother’s existing deficient status.  Is there evidence that when pregnant or lactating women take vitamin D, the breast milk and the baby’s blood levels are increased?  Results from a couple of recent studies hint at the answer:

*When pregnant women were given different levels (400, 2000 or 4000 IU/day) of vitamin D, the highest dose was most likely to achieve a sufficient blood level.  Both the 2000 and 4000 IU doses led to significantly improved blood levels compared to the lowest 400 IU dose.  The researchers didn’t find any evidence of adverse events linked to taking vitamin D.

*A small group of breast feeding women were divided into two vitamin D dosage groups: either 0 or 6000 IU/day for 6 months, in addition to the standard 400 IU/day present in a multiple vitamin supplement.  The infants of the non-supplemented mothers were given 300 IU/day in drops; the infants whose moms got the high dose of vitamin D didn’t take vitamin D drops.

The researchers analyzed the vitamin D in mother’s blood and breast milk and in the infant’s blood.  They also considered factors like sun exposure and skin pigmentation.  The vitamin D in the milk of women in the 0 IU group actually went down during the study, to a low of 45 IU/liter.  The level in the high dose group went from 82 IU at 1 month to 873 IU/liter at the end of the study.  By comparison, the vitamin D content of formula is set at 400 IU per liter.

When infant blood vitamin D was compared, both groups had similar levels.  The conclusion: supplementing the breastfeeding mother raises breast milk vitamin D, and that level raises the baby’s vitamin D level as much as supplementing the baby with drops.  What we don’t know is whether a lower dose for the mom would work just as well, say 2000 or 4000 IU/day.  This study also seems to say that, even when infants consumed over 800 IU/day in breast milk they only absorbed the vitamin D at a rate comparable to the recommended daily dose of 400 IU.

So while it seems high dose supplementation for a nursing mom can raise vitamin D in breast milk, we still don’t know what an ideal level is.  We also don’t know what an ideal level for the infant is.  A blood level that prevents rickets (vitamin D deficiency) might not be optimal, considering all the other metabolic roles vitamin D appears to play.  For now, infants should certainly get the recommended 400 IU/day, whether from formula or drops or breast milk.  Unfortunately the only way for a mom to be sure her milk has enough D is to have it tested at a lab, which is probably a lot of expense and trouble.  Someday perhaps we’ll have breast milk dip strips to test for D.  Until then, new moms can at least be sure they have enough vitamin D in their own blood, and supplement if necessary.

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