Many new mothers worry about what to eat while nursing. The advice flies in from every direction and often contradicts itself. For something so basic, there is surprisingly little hard data on which foods actually reach the baby through the milk.
A large new analysis of nursing mothers in Minnesota and Oklahoma now provides a clearer picture. Researchers from the Mothers and Infants Linked for Healthy Growth, or MILK, study measured 458 compounds in milk samples taken about one month after birth.
In a bioRxiv preprint, the analysis found that a mother's diet explained more of the differences in milk composition than any other factor the team measured.
Coffee left the clearest trace. Coffee intake was tightly linked to two compounds in the milk, quinic acid and 1,3-dimethyluric acid, which is a caffeine breakdown product. Diet alone explained about one third of the differences in quinic acid between mothers.
Also read: Butter and cheese may not be as unhealthy as we thought, new research suggests
Diet also showed up through a compound called proline-betaine. It rose with high-fiber eating patterns and is widely used in nutrition research as a marker of citrus intake.
The findings are a preprint. That means they are being shared ahead of formal peer review and should still be read as preliminary.
How much of breast milk is shaped by what mom eats
The team ran more than a thousand comparisons between food habits and compounds in milk. They found 1,038 strong links between 199 dietary features and 458 milk compounds.
Nearly nine in ten of those links were positive. More of a given food in the mother's diet usually meant more of a given compound in her milk. A healthier overall eating pattern was tied to higher milk levels of riboflavin, better known as vitamin B2.
Also read: 12 Routine Daily Habits That Add Up to Serious Heart Disease Risk
Alcohol pointed the other way. Mothers who drank more had lower milk levels of a signaling fat called sphingosine-1-phosphate, which is involved in cell growth and immune function.
Genes mattered too, but less. The team found nine strong links between inherited gene variants and specific milk compounds. These included variants near two genes that help the body handle caffeine-related compounds and a sugar called sialic acid.
What the findings do and do not say about your baby
The study did not test whether any of these milk compounds affect infants. It only mapped what is in the milk and where it comes from. The authors describe their work as a foundation for later research on infant health.
The MILK study also measured milk only once, at about one month after birth, and relied on dietary questionnaires. Most participants were of European ancestry, and the genetic part of the analysis covered 197 mothers.
Also read: These signs of bowel cancer can easily be mistaken for common stomach problems
For an everyday coffee question, current public guidance has not changed. The Centers for Disease Control and Prevention says a low to moderate caffeine intake, about 300 milligrams a day or roughly two to three cups of coffee, usually does not affect a breastfed baby.
Very high intakes, around 10 cups a day or more, can cause irritability and poor sleep in the infant. Mothers of preterm or newborn babies are advised to consider less, since young infants clear caffeine more slowly.
Also read: A Mayo Clinic AI may predict your pancreatic cancer risk up to 5 years before symptoms
This article is made and published by Aksel Kryhlmand, who may have used AI in the preparation.