Lactation is the process of milk production and secretion from the mammary glands, which are exocrine glands located in the breasts. In female adult humans, milk production begins during pregnancy, and lactation continues throughout the postpartum period. Initially, hormones (like progesterone and prolactin) regulate milk production. Milk removal takes on a greater role in stimulating ongoing lactation by four days postpartum, and by ten days postpartum, ongoing lactation is entirely stimulated by removal of milk from the breasts. Lactation insufficiency occurs when the parent does not produce enough milk to meet the nutritional needs of their infant.

Moderate levels of exercise do not appear to affect milk production or impair infant growth.^[1][2][3] However, intense or exhaustive exercise may temporarily alter milk composition (e.g., increased lactic acid and decreased secretory IgA concentrations), but milk composition usually returns to baseline within one hour postexercise. Moreover, infants can safely drink milk produced immediately postexercise despite the change in composition.^[4]

Many supplements have been studied for lactation, including fenugreek seed, Coleus amboinicus (torbangun) extract, and moringa leaves. However, there is no robust or consistent data to support the effectiveness of supplements in increasing milk supply for lactating parents. Some trials examining single or multi-ingredient supplements and teas have reported positive findings, like increased milk volume and higher infant weight. However, other trials have found no effect on lactation, and the evidence is too limited to make strong conclusions about efficacy.^[5][6][7]

It is important for lactating parents to speak with a healthcare provider who is knowledgeable about lactation medicine before using a supplement while breastfeeding. Some herbal supplements may suppress lactation, including jasmine, licorice extracts in high doses, peppermint, and sage, although the evidence for this is limited and sometimes anecdotal.^[8]. It is also possible for supplements to pass into human milk and change its taste, color, and/or composition.^[9][10] Some of these changes may affect the infant.

Although diet can affect lactation, human milk volume and composition are resilient and remain relatively consistent across a wide variety of diets.^[11][12] Eating enough calories and staying hydrated builds an important dietary foundation for milk production. The additional energy demand of lactation is estimated at about 450 to 500 kcals per day (see below). Lactating people also have an increased requirement for protein, choline, many vitamins (including A, C, E, and most B vitamins), and the minerals iodine, selenium, and zinc.^[13][14] However, if a parent’s diet is deficient in the nutrients required to make milk, their body will mobilize and (if necessary) deplete fat, vitamin, and mineral stores to meet the demands of lactation, even at the expense of the parent’s health. A balanced, nutrient-dense diet can protect the parent from dietary deficiencies while also supporting ongoing lactation.

The primary driver of lactation past 10 days postpartum is milk removal. If the breasts aren’t emptied (i.e., the stored milk is removed to the point that the breasts feel soft and/or hand-expressing more is difficult) at feedings, the body makes less milk to compensate. Optimizing breastfeeding techniques is therefore important for sustained and bountiful milk production (see below).

Stress/anxiety, medications (e.g., oral birth control), menstruation, fatigue, hormonal conditions, genetics, and breast surgery can also affect lactation.^[15] Many prescription and over-the-counter medications and recreational drugs, including alcohol, can be expressed in human milk, but not all of them are expressed at levels that could be harmful to the breastfeeding infant.^[16][17]

If planning or needing to take medications or recreational drugs while breastfeeding, it’s wise to check with a knowledgeable healthcare provider, such as a doctor or pharmacist.