Lactation is a complex biological process regulated by hormones, and new parents often worry about maintaining a sufficient milk supply. Peppermint, a popular herb found in teas, candies, and various flavorings, has a long-standing connection to reduced milk production. This association often causes confusion for those navigating the early stages of breastfeeding and warrants a closer look at the available evidence.
The Mechanism of Supply Reduction
The concern surrounding peppermint’s effect on milk supply stems from its primary active compound, menthol. Menthol is traditionally recognized as an anti-galactagogue, a substance believed to decrease breast milk production by interfering with the physiological pathways responsible for lactation.
Recent research, primarily from in vitro (cell culture) and animal studies, suggests that menthol may suppress milk production at a cellular level. Studies show menthol can inactivate key signaling pathways, known as STAT5 and mTOR, within the mammary epithelial cells. These pathways are normally activated by the hormone prolactin, which is necessary for initiating and maintaining milk synthesis.
By interfering with prolactin signals, menthol is thought to reduce the production of major milk components, such as beta-casein. Menthol is also believed to act on specific receptors, TRPM8 and TRPA1, potentially inhibiting the cell’s ability to secrete milk fat. While this mechanism aligns with traditional use, robust clinical trials isolating this effect in humans are limited.
Risk Based on Peppermint Form
The likelihood of peppermint affecting milk supply is highly dependent on the concentration and frequency of consumption. The amount of menthol ingested is the primary factor determining the potential anti-galactagogue effect, with a significant difference existing between essential oils and trace amounts used for flavoring.
Pure peppermint essential oil, which contains 30% to 55% menthol, represents the highest risk. Ingesting this oil in capsule form or using large amounts topically should be avoided during lactation. Strong medicinal-grade peppermint teas, especially those consumed multiple times daily, deliver a substantial dose of menthol and are associated with a higher potential for reducing milk supply.
Conversely, the risk posed by standard food flavorings is considered low or negligible. Small amounts of peppermint extract found in commercial chewing gum, candies, or a single cup of mild, commercially prepared tea are unlikely to impact milk production significantly. For those who consume concentrated forms, monitoring milk output is advisable, and any perceived drop in supply should prompt immediate discontinuation.
Other Common Herbs Affecting Lactation
Peppermint is not the only botanical substance that influences milk supply; numerous other herbs act as either anti-galactagogues or galactagogues.
Other common herbs known to interfere with milk production include sage, which is frequently used to suppress milk supply during weaning. Parsley, when consumed in very large quantities, can also exhibit anti-galactagogue properties, as can oregano oil. These substances are often recommended to those who wish to dry up their milk supply.
Galactagogues are herbs traditionally used to support or increase milk production. While scientific evidence supporting their efficacy is often based on traditional use, common galactagogues include:
- Fenugreek
- Fennel
- Blessed thistle
- Stinging nettle