A randomized clinical trial in Austin asked 24 families to eat prepared meals over a 25-day period. The meals were nutritionally balanced and identical except for the main protein: whole-food beef or an ultra-processed plant-based substitute. Total fat in the meals remained the same, but the types of fat that appeared in breast milk shifted with each diet.
Mothers who ate the plant-based substitute showed lower levels of long-chain polyunsaturated fatty acids, nutrients known to support infant neurodevelopment. Their milk also contained higher levels of saturated fats that come from tropical oils commonly used in ultra-processed foods. The study, published in the American Journal of Clinical Nutrition, reported these changes within about six days.
Lead author Marissa Burgermaster, an assistant professor at the University of Texas at Austin, said the team was surprised by how quickly one food swap produced clear changes. The researchers note the trial did not assess long-term infant outcomes, and they called for clearer, evidence-based guidance for breastfeeding families.
Difficult words
- randomize — to choose people into groups by chancerandomized
- ultra-processed — made with many industrial ingredients and steps
- polyunsaturated fatty acid — a healthy fat with many double bondspolyunsaturated fatty acids
- saturated fat — a fat type often solid at room temperaturesaturated fats
- tropical oil — oils from tropical plants like coconuttropical oils
- evidence-based — based on scientific research and data
- breastfeeding — feeding a baby with milk from the mother
Tip: hover, focus or tap highlighted words in the article to see quick definitions while you read or listen.
Discussion questions
- Would you consider changing your diet while breastfeeding after reading this? Why or why not?
- What information would you want from health professionals about how diet affects breast milk?
- How easy or difficult would it be for families to replace meat with ultra-processed plant foods? Give reasons.
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