Change Mom’s Diet and Her Milk Changes Too

Written by: Alla Katsnelson, Ph.D | Issue # 127 | 2025

You’ve probably heard the old adage, “You are what you eat.” A new study finds it’s true for lactating mothers – at least, for their breastmilk. Diet influences both the quantity and the nutritional content of  breastmilk, according to a recent study of lactating mothers in Turkey [1].

Earlier studies on the link between diet and milk content [2] were largely observational, meaning that researchers drew conclusions based on what women reported that they ate in their normal diet. However, many of these studies are dated and have yielded conflicting [3] and unclear [4, 5] results, so a coherent picture of nutrition’s effects on milk is lacking.

In this study, researchers provided women with specific diets and then tested how each of the diets affected a given woman’s breastmilk. Based on this interventional approach, they looked at dietary effects on macronutrient content as well as on concentrations of lactose, vitamin B2, and several amino acids in expressed breastmilk.

A diet high in carbohydrates increased the amount of amino acids, and a diet high in protein boosted milk quantity and its lactose content, the study found.

In the study, the researchers compare the effects of three different diets on the nutritional content and quantity of breastmilk in a group of 72 mothers  between 4 and 24 weeks postpartum. In each of the three diets, the women ate 2200 calories per day, as advised by Turkey’s dietary guidelines.

All the diets included a set list of foods. However, the diets different by macronutrient composition. The generally healthy nutrition diet consisted of 55–60% carbohydrates, 10–15% protein, and 25–30% fat. The carbohydrate-rich diet included 65% carbohydrates, 15% protein, and 20% fat. And the protein-rich diet contained 50% carbohydrates, 25% protein, and 25% fat. The researchers achieved these macronutrient changes by altering amounts of foods included in the healthy nutrition diet.

The researchers divided the mothers into four groups – a younger group, ages 24-29, who were 4-12 weeks postpartum or 13-24 weeks postpartum, and an older group, ages 30-35, who were 4-12 weeks postpartum or 13-24 weeks postpartum.  Each participant consumed the healthy nutrition diet for one week, then switched to the carbohydrate-rich diet for the second week, and finally had the protein-rich diet for the third week.

There were no breaks between the three stints, and researchers checked in twice per week to ensure that participants adhered to the diets. At the conclusion of each week, researchers collected milk expressed by the women for 20 minutes, measured its volume, and analyzed its contents.

The study found that milk volume was not affected by maternal nutrition, except in one condition – milk from women in the later postpartum group contained more protein after the protein enriched diet than after the carbohydrate enriched diet. That finding  aligns with previous work, the researchers note. Results also showed that several amino acids were increased after the carbohydrate enriched diet, compared to the healthy nutrition diet. These were glutamic acid, serine, glycine, histidine, tyrosine, valine, isoleucine, leucine, and lysine. This list of amino acid changes is somewhat different than one obtained in an observational study comparing dietary effects on lactation in Mexican mothers who follow a high carbohydrate and low-fat diet and American mothers who follow a low carbohydrate and high fat diet [6].

Levels of only a few amino acids – aspartic acid, glutamic acid, glycine, and lysine increased in milk expressed after the protein rich diet, compared to milk expressed after the healthy nutrition diet. At least one previous study, an observational study of mothers in Beijing, found no changes in amino acid levels after mothers increased their consumption of dietary protein [7].

The protein rich diet also appeared to increase lactose in the expressed milk. Vitamin B2 levels in the study were decreased after both the carbohydrate and protein enriched diets.

Because the researchers focused on a very specific population – women living in Istanbul –it’s difficult to know whether the results generalize more broadly. In fact, taken together with past studies, the results suggest that regional and population differences may play a role in how exactly nutrition affects breastmilk. Overall, the work underscores the need for a wider and more detailed study on the subject.

References

1. Öner Sayar C, Köseoğlu SZA. Evaluation of the effect of different diets applied to breastfeeding mothers on the composition and quantity of human milk. Eur J Clin Nutr. 2025.  doi: 10.1038/s41430-025-01588-z.
2. Bravi F, Wiens F, Decarli A, Dal Pont A, Agostoni C, Ferraroni M. Impact of maternal nutrition on breast-milk composition: a systematic review. Am J Clin Nutr. 2016 Sep;104(3):646-62.
3. Adhikari S, Kudla U, Nyakayiru J, Brouwer-Brolsma EM. Maternal dietary intake, nutritional status and macronutrient composition of human breast milk: systematic review. Br J Nutr. 2022 Jun 28;127(12):1796-1820.
4. Binder C, Baumgartner-Parzer S, Gard LI, Berger A, Thajer A. Maternal diet influences human milk protein concentration and adipose tissue marker. Nutrients. 2023;15:433.
5. Miliku K, Duan QL, Moraes TJ, Becker AB, Mandhane PJ, Turvey SE, Lefebvre DL, Sears MR, Subbarao P, Field CJ, Azad MB. Human milk fatty acid composition is associated with dietary, genetic, sociodemographic, and environmental factors in the CHILD Cohort Study. Am J Clin Nutr. 2019 Dec 1;110(6):1370-1383.
6. Villalpando S, Butte NF, Flores-Huerta S, Thotathuchery M. Qualitative analysis of human milk produced by women consuming a maize-predominant diet typical of rural Mexico. Ann Nutr Metab. 1998;42:23–32.
7. Zhao X, Xu Z, Wang Y, Sun Y. Studies of the relation between the nutritional status of lactating mothers and milk composition as well as the milk intake and growth of their infants in Beijing. Pt. 4. The protein and amino acid content of breast milk. Ying Yang Xue Bao. 1989;11:227–232.