Breast milk samples with detectable cannabis metabolites had higher protein levels and 11% lower fat content compared to samples without cannabis exposure, though calorie and carbohydrate levels were unchanged.
Lactation consultants, obstetricians, breastfeeding mothers who use cannabis, pediatric nutritionists.
Cannabis-exposed breast milk had 11% less fat and more protein than unexposed samples
What the researchers found
The presence of cannabis metabolites in breast milk was associated with an increase of 0.244 mg/dL in protein and an 11% reduction in fat content. Energy and carbohydrate levels were not significantly different between exposed and unexposed samples.
Why it matters
As cannabis use rises among lactating women, understanding its effects on breast milk composition is important for infant nutrition. Changes in protein and fat levels could theoretically affect infant development, though the clinical significance of these specific changes is unknown.
The numbers in context
637 breast milk samples; 165 with detectable cannabis metabolites; protein increase of 0.244 mg/dL (95% CI 0.112-0.376, p<0.05); 11% reduction in fat (p=0.020); no significant differences in energy or carbohydrates.
How the study worked
Cross-sectional study analyzing 637 breast milk samples, of which 165 had detectable cannabis metabolites (study group) and 472 did not (control group). Multivariable linear regression was used to assess associations between cannabis metabolite presence and protein, carbohydrate, fat, and calorie content.
What this study cannot tell us
Cross-sectional design cannot establish causation. Self-reported cannabis use may underestimate exposure. Cannot determine dose-response relationships. The clinical significance of the observed macronutrient changes for infant health is unknown. Does not account for all potential confounders (diet, other substances).
How to read the evidence
Moderate: Meaningful sample size with objective metabolite detection and multivariable adjustment, though cross-sectional design and unknown clinical significance of findings are limitations.
When this study was published
Published in 2025.
The bigger picture
This is one of the first studies to examine how cannabis affects the macronutrient composition of breast milk beyond simply detecting THC transfer. The finding adds a new dimension to discussions about cannabis and breastfeeding that have mostly focused on THC exposure to infants.
Questions still open
- What are the downstream effects of altered breast milk macronutrients on infant growth? Does the frequency or amount of cannabis use affect the degree of macronutrient change? What mechanisms explain how cannabis alters breast milk composition?
Common questions
Is it safe to use cannabis while breastfeeding?
How were cannabis metabolites detected in breast milk?
Read the original research
The Effect of Cannabis Consumption During Lactation on the Macronutrient Concentrations in Breast Milk.
Breastfeeding medicine : the official journal of the Academy of Breastfeeding Medicine, 20(1), 33-41
Citation
Narayanan, Priyadharshini; Bertrand, Kerri; Waalen, Jill; Chambers, Christina; Ferran, Karen; Bandoli, Gretchen. (2025). The Effect of Cannabis Consumption During Lactation on the Macronutrient Concentrations in Breast Milk.. Breastfeeding medicine : the official journal of the Academy of Breastfeeding Medicine, 20(1), 33-41. https://doi.org/10.1089/bfm.2024.0083
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