When considering any supplement during lactation, a foundational understanding of the potential risks and benefits is necessary. Quercetin, a popular bioflavonoid, has gained attention as a dietary supplement. New mothers often question the safety of supplemental quercetin while breastfeeding, given the need for caution with any substance that could pass into breast milk.
What is Quercetin?
Quercetin is a natural plant pigment belonging to the flavonoid group of polyphenols. This compound is widely distributed in the plant kingdom and is one of the most abundant dietary flavonoids consumed by humans. Common foods that contain quercetin include onions, capers, apples, berries, tea, and kale.
The average daily consumption of quercetin from the diet is estimated to be between 10 and 100 milligrams. Because it is present in many healthy foods, it is recognized as safe for consumption through diet. People often take quercetin supplements for its antioxidant and anti-inflammatory effects.
The supplemental form provides a much higher concentration of the compound, with doses often ranging from 250 to 1,000 milligrams per day. Quercetin is marketed for its potential to support immune function, reduce inflammation, and alleviate allergy symptoms.
How Compounds Transfer into Breast Milk
The transfer of any compound from a mother’s bloodstream into her breast milk is governed by several physicochemical properties. Most compounds enter the milk via passive diffusion across the mammary alveolar cells. The resulting concentration in milk is influenced by the compound’s characteristics, the mother’s plasma concentration, and the composition of the milk itself.
A compound’s molecular weight is a significant factor in transfer; smaller molecules, generally those under 300 Daltons, cross the milk barrier more easily. Quercetin has a molecular weight of 302 Daltons, suggesting it could potentially diffuse into milk. The degree of a compound’s lipid solubility is also important, as the mammary epithelium is a lipid membrane, making highly fat-soluble substances more likely to penetrate.
Compounds highly bound to plasma proteins, such as albumin, are less likely to transfer into milk because only the free, unbound fraction is available to diffuse. Additionally, the degree of ionization at the slightly lower pH of breast milk can lead to “ion trapping,” where a compound becomes ionized in the milk and cannot diffuse back into the maternal circulation. The amount of drug that transfers into milk is often expressed as the milk-to-plasma (M/P) ratio.
Safety Data on Quercetin and Lactation
Direct safety data on the use of high-dose quercetin supplements during human lactation is lacking. Currently, no human clinical trials have specifically investigated the effects of quercetin supplementation on breastfeeding mothers or their infants. The absence of specific research means that the potential risks to the nursing infant are unknown, leading to a general recommendation for caution.
Despite the lack of safety data for supplements, a small study confirmed that quercetin from the maternal diet passes into human milk. After mothers consumed a single quercetin-rich meal, the compound was detected in their milk at very low, nanomolar levels. The estimated daily dose an infant receives from a mother eating a quercetin-rich diet is approximately 0.01 milligrams, which is considered a negligible exposure.
The concern centers on high-dose supplements, which provide concentrations far exceeding typical dietary intake. The low oral bioavailability of quercetin means most of the compound is rapidly metabolized, which may limit the amount that ultimately reaches the milk. However, the lack of information on the M/P ratio and the half-life of its metabolites in human milk makes it impossible to confirm the safety of supplemental doses. Organizations advise breastfeeding mothers to avoid supplements when data is insufficient to ensure safety.
Consulting Healthcare Professionals
Before a breastfeeding mother begins taking any dietary supplement, consulting with healthcare professionals is essential. A physician or an International Board Certified Lactation Consultant (IBCLC) can provide guidance tailored to the individual mother and infant. They help weigh the potential benefits of the supplement against the unknown risks to the nursing infant.
Practical steps involve reviewing the specific formulation of the supplement for purity and the presence of other additives. If a healthcare professional agrees to a trial, it is suggested to start with the lowest possible dose. The mother should monitor the infant closely for any signs of an adverse reaction, such as a rash, changes in sleep patterns, or increased fussiness. This cautious approach helps mitigate the risks associated with supplementing when specific safety data is unavailable.