How does a plant-based diet affect the mineral content of breast milk?

A new study suggests that following a vegan or vegetarian diet may influence the selenium levels in breast milk – but not in the way that might be predicted.

While plant-based diets continue to grow in popularity, there is currently limited information on the influence of maternal dietary patterns on the mineral composition of breast milk.

Breast milk contains water, fat, carbohydrates, protein, vitamins, minerals and amino acids. Some of these constituents, such as calcium, are almost guaranteed to be in breast milk regardless of maternal diet – as they are drawn from the mother’s body stores if needed. But other constituents – such as vitamin B12, iron, iodine and zinc – that the body doesn’t store in large amounts or can’t make itself must come from the food eaten by the lactating mother.

Some previous research has suggested that adults following vegan or vegetarian diets may consume low amounts of some minerals including calcium, iodine, selenium and zinc. But studies looking at the mineral content of breast milk from vegan and vegetarian mothers are currently scarce.

Mineral analysis

In a new study, published in the British Journal of Nutrition, researchers explored the major and trace mineral composition in breast milk associated with different maternal diets.1

The researchers collected a sample of breast milk from 42 US women following a vegetarian, vegan, or omnivore diet. They measured the amount of sixteen minerals in each sample using inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma optical emission spectrometry (IOP-OES). They then analysed data using traditional statistical techniques and five different machine-learning approaches.

Selenium was the only mineral with statistically different levels between the dietary groups: vegetarians 18 to 26 µg/L; vegans 18 to 25 µg/L; and omnivores 14 to 20 µg/L. The team also identified selenium as a potential biomarker for differentiating breast milk by maternal diet pattern using machine learning techniques.

The researchers used ultrapure water generated from an ELGA PURELAB® Option-Q laboratory water purification system for preparing samples for analysis, minimising the risk of introducing contaminants that may affect their results.

Future studies

In this small study, researchers assessed the breast milk mineral composition of US women with different dietary patterns. They found that selenium consistently differed between women following plant-based diets (vegan and vegetarian) compared to omnivore diets – using a variety of statistical and machine learning approaches.

These results agree with previous studies suggesting that selenium is found at higher levels in the breast milk of women who follow plant-based diets – which is perhaps surprising given the reports of low selenium intake among vegans.

Future research on the impact of a maternal plant-based diet on breast milk composition is now warranted, using larger sample sizes and longitudinal designs. These studies should also distinguish maternal mineral intake from diet versus supplementation, maternal mineral status, and infant outcomes measures including growth and development.

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Reference:

1. Perrin, M. T. et al. Major and Trace Composition of Milk from Lactating Women Following Vegan, Vegetarian, and Omnivore Diets. Br J Nutr. 2022;23:1-8 doi: 10.1017/S0007114522004007

Dr Alison Halliday

After completing an undergraduate degree in Biochemistry & Genetics at Sheffield University, Alison was awarded a PhD in Human Molecular Genetics at the University of Newcastle. She carried out five years as a Senior Postdoctoral Research Fellow at UCL, investigating the genes involved in childhood obesity syndrome. Moving into science communications, she spent ten years at Cancer Research UK engaging the public about the charity’s work. She now specialises in writing about research across the life sciences, medicine and health.