Cannabis use temporarily changed fat and sugar levels in breast milk
After mothers used cannabis, breast milk showed lower lipid levels and altered fatty acid profiles for several hours, with THC levels correlating positively with fat and negatively with lactose.
Quick Facts
What This Study Found
Cannabis use was associated with temporarily lower lipid and fatty acid concentrations and blunted lactose increase in breast milk; THC levels correlated positively with lipids and negatively with lactose.
Key Numbers
20 cannabis users, 19 controls; lipid and 10 of 39 identified fatty acids were lower after use; no baseline differences between groups; no protein differences at any timepoint.
How They Did This
Within-subjects design with 20 breastfeeding cannabis users matched with 19 non-using controls by BMI and time postpartum; cases abstained 12+ hours, collected baseline milk, used cannabis, then collected samples at multiple timepoints up to 8-12 hours.
Why This Research Matters
Cannabis use among breastfeeding women is increasing, but almost nothing is known about how it affects milk nutritional composition beyond cannabinoid transfer.
The Bigger Picture
This adds a nutritional dimension to the discussion about cannabis and breastfeeding, beyond the known issue of THC transfer to infants.
What This Study Doesn't Tell Us
Small sample (n=39 total); single cannabis use session; did not measure infant outcomes; could not control for cannabis product variation; THC as the measured cannabinoid may not capture full effects.
Questions This Raises
- ?Do repeated cannabis use sessions produce cumulative effects on milk composition?
- ?Could these transient changes affect infant nutrition or growth?
- ?What mechanisms drive the lipid decrease?
Trust & Context
- Key Stat:
- 10 of 39 fatty acids measured were lower in milk after cannabis use
- Evidence Grade:
- Well-designed matched study with repeated sampling, but small sample size and single-session design limit generalizability.
- Study Age:
- Published 2025
- Original Title:
- Short-Term Effects of Maternal Cannabis Use on Human Milk Macronutrient Composition: The Lactation and Cannabis (LAC) Study.
- Published In:
- Breastfeeding medicine : the official journal of the Academy of Breastfeeding Medicine (2025)
- Authors:
- Castro-Navarro, Irma, Williams, Janet E, Dussurget, Léa, Richardson, Haley, Berim, Anna, Gang, David R, Holdsworth, Elizabeth A, Caffé, Beatrice, Smith, Caroline, Barbosa-Leiker, Celestina, Brooks, Olivia, McGuire, Mark A, Meehan, Courtney L, McGuire, Michelle K
- Database ID:
- RTHC-06173
Evidence Hierarchy
Enrolls participants and follows them forward in time.
What do these levels mean? →Frequently Asked Questions
Did cannabis change the nutritional content of breast milk?
Yes, temporarily. Fat and several fatty acids dropped after use, and the normal lactose increase seen in controls was blunted in cannabis users.
Was protein affected?
No. Protein concentrations showed no differences between cannabis users and controls at any timepoint.
Read More on RethinkTHC
Cite This Study
https://rethinkthc.com/research/RTHC-06173APA
Castro-Navarro, Irma; Williams, Janet E; Dussurget, Léa; Richardson, Haley; Berim, Anna; Gang, David R; Holdsworth, Elizabeth A; Caffé, Beatrice; Smith, Caroline; Barbosa-Leiker, Celestina; Brooks, Olivia; McGuire, Mark A; Meehan, Courtney L; McGuire, Michelle K. (2025). Short-Term Effects of Maternal Cannabis Use on Human Milk Macronutrient Composition: The Lactation and Cannabis (LAC) Study.. Breastfeeding medicine : the official journal of the Academy of Breastfeeding Medicine. https://doi.org/10.1177/15568253251407688
MLA
Castro-Navarro, Irma, et al. "Short-Term Effects of Maternal Cannabis Use on Human Milk Macronutrient Composition: The Lactation and Cannabis (LAC) Study.." Breastfeeding medicine : the official journal of the Academy of Breastfeeding Medicine, 2025. https://doi.org/10.1177/15568253251407688
RethinkTHC
RethinkTHC Research Database. "Short-Term Effects of Maternal Cannabis Use on Human Milk Ma..." RTHC-06173. Retrieved from https://rethinkthc.com/research/castro-navarro-2025-shortterm-effects-of-maternal
Access the Original Study
Study data sourced from PubMed, a service of the U.S. National Library of Medicine, National Institutes of Health.
This study breakdown was produced by the RethinkTHC research team. We analyze and report published research findings without making health recommendations. All interpretations are based solely on the published abstract and study data.