Can Vegan Diets or Cutting Carbs Change Your Breast Milk? Here’s What Science Says.

Can a vegan diet or cutting carbs affect your breast milk? Here’s what the science says about nutrition and breastfeeding health.

Breast milk is widely recognised as the gold standard for infant nutrition, but mothers often wonder whether their dietary choices change its composition. Two recent systematic reviews shed light on this question, one looking at vegan and vegetarian diets, and the other examining carbohydrate-restricted diets in breastfeeding women, giving us valuable insights into how these patterns may affect both mothers and their babies.

A systematic review published by Karcz and Królak-Olejnik in 2021 analysed 13 studies comparing breast milk from omnivorous, vegetarian, and vegan mothers. The overall conclusion was reassuring: when diets are well-balanced and appropriately supplemented, breast milk from vegan or vegetarian mothers remains nutritionally adequate for infants [1]. Total protein, lactose, and fat content were similar to those in milk from omnivorous mothers. Some differences were noted in lipid profiles, milk from vegan and vegetarian women often contained less saturated fat and trans fat and sometimes a higher proportion of plant-derived omega-3 fatty acids such as alpha-linolenic acid. Longer chain omega-3 fatty acids like DHA and EPA showed no major differences, especially when mothers used supplements [1,2].

Micronutrients are where the differences become more significant. Vitamin B12 is consistently lower in the milk of vegan mothers unless supplementation is used, and its deficiency can have serious consequences for infant neurological development. Selenium levels were sometimes higher in milk from vegan or vegetarian mothers, which might reflect higher intake of plant sources rich in selenium or supplementation [3]. The key message is that vegan and vegetarian diets can support healthy breastfeeding if mothers ensure adequate calorie intake, include a variety of protein sources, and use supplements for B12 and possibly DHA/EPA to maintain optimal milk quality [1].

In contrast, the evidence on carbohydrate-restricted diets during lactation paints a more cautious picture. A 2024 systematic review by Amorim and colleagues evaluated 16 studies on women following low-carb or ketogenic diets while breastfeeding, most of whom adopted these diets for weight loss rather than medical reasons. Many reported maternal symptoms such as nausea, vomiting, fatigue, muscle weakness, and abdominal pain, and in some cases, severe metabolic complications like lactational ketoacidosis were documented [4]. Although no consistent adverse effects were reported in infants, data on milk composition remain scarce, and the long-term impact of these diets on infant growth and development has not been established [4].

These findings highlight a stark contrast between the two dietary patterns. Vegan and vegetarian diets, when planned with attention to key nutrients, are generally compatible with healthy lactation. Carbohydrate restriction, especially at ketogenic levels, carries more risk for the mother’s health and should only be undertaken with close medical supervision. Extremely low carbohydrate intake can reduce overall calorie availability and may disrupt normal metabolism, putting mothers at risk for dehydration, electrolyte imbalances, and metabolic stress [4,5].

For breastfeeding mothers considering dietary changes, the key takeaway is to focus on adequacy rather than restriction. Meeting energy and protein needs, including a variety of foods, and using targeted supplementation when necessary are essential steps to support both maternal health and optimal milk composition. Any major diet change should be discussed with a healthcare professional or dietitian, especially when it involves cutting out entire food groups or significantly reducing carbohydrates.

The science is clear: a well-planned vegan or vegetarian diet can provide breast milk that supports healthy infant growth, while extreme carbohydrate restriction carries measurable risks for mothers and remains under-researched for its effects on milk and infant outcomes. Supporting maternal health through balanced nutrition is one of the most powerful ways to protect both mother and baby during the critical months of breastfeeding.

References

1. Karcz K, Królak-Olejnik B. Vegan or vegetarian diet and breast milk composition – a systematic review. Crit Rev Food Sci Nutr. 2021;61(7):1081-1098.

2. Perrin MT, Pawlak R, Allen LH, Hampel D. Total water-soluble choline concentration does not differ in milk from vegan, vegetarian, and nonvegetarian lactating women. J Nutr.2019;150(3):512-517.

3. Major and trace mineral composition of milk from lactating women following vegan, vegetarian and omnivore diets. Br J Nutr. 2023;130(6):1005-1012.

4. Amorim ALB-d, Rodrigues EF, Sussi EL, Neri LCL. Carbohydrate restriction during lactation: A systematic review. Nutr Res. 2024;125:91-100.

5. USDA Nutrition Evidence Systematic Review: Dietary Patterns during Lactation and Human Milk Composition. 2022.