Response to Verd and Ponce-Taylor re: “Potentially Toxic Foods While Breastfeeding: Garlic,Caffeine,Mushrooms,and More”

I appreciate the interest in the LactMed Update column “Potentially Toxic Foods While Breastfeeding: Garlic, Caffeine, Mushrooms, and More,” ¹ by Drs. Verd and Ponce-Taylor, ² but find their comments rather confusing. They state that the LactMed Update column, “accepts that with typical intakes, the amount of caffeine present in breast milk is not sufficient to cause an effect on the infant.” They then state that a recent systematic review of published studies contradicts the column's warning about high-dose caffeine. Not only does the review not address extremely high maternal intake of caffeine, the abstract of the review concludes, “Evidence for recommendations on caffeine intake for breastfeeding women is scant, of limited quality and inconclusive.” ³

Current evidence indicates that maternal caffeine intake of 2–4 cups daily is likely not problematic for most breastfed infants. The intakes reported in some of the high-dose case reports were 5–10 times greater than this. To use safe typical intake of caffeine to refute the potential toxicity of high doses makes no pharmacological sense. It is unlikely that a randomized controlled study of high-dose caffeine in nursing mothers will ever be conducted. So, we are left with imperfect case reports of extreme caffeine intake to guide clinical judgment. Although the case with allegedly decaffeinated coffee is puzzling, the intakes in the other case reports are consistent with the toxicological maxim that, “the dose makes the poison.” These high intakes of caffeine could certainly be in the range of maternal doses that affect a breastfed infant.

The other issue raised concerns preterm infants, who have a caffeine clearance of <10% of adult clearance.^4,5 This means that any caffeine ingested in milk would have a greater impact on a preterm infant than it would in a full-term or older infant. Noting this fact does not seem unreasonable.

The point the authors make about not excessively restricting the diet of nursing mothers with healthy eating habits during breastfeeding is good advice. But, unless 20 cups of coffee a day is considered a healthy eating habit, the column simply did not make a recommendation to avoid all caffeine while breastfeeding.

Finally, LactMed Update is a greatly abbreviated summary of information contained in LactMed records at a point in time, organized by topic rather than by individual drug. Each column states that further information can be found in LactMed records. ⁶ The LactMed record on caffeine contains a more complete review of the literature on maternal use of caffeine during breastfeeding.