Selenium is a trace mineral obtained through diet that performs several functions in the body. Its concentration in food is affected by its presence in soil and water. For new mothers, understanding selenium’s role is important for their own health and the optimal development of their newborn, as it contributes to thyroid hormone synthesis and antioxidant defense.
Selenium’s Role for Mother and Infant
During the postpartum period, a mother’s body undergoes significant adjustments, and selenium supports this recovery. One of its primary functions is regulating thyroid hormones, which can be volatile after childbirth. Selenium is a component of enzymes that convert the thyroid hormone T4 into its more active form, T3, helping to maintain metabolic balance.
The mineral also mitigates oxidative stress. Childbirth and recovery increase the production of free radicals, which are unstable molecules that cause cellular damage. Selenium is a constituent of selenoproteins, such as glutathione peroxidase, which act as antioxidants to neutralize free radicals, protecting cells and supporting the mother’s immune system.
For a nursing infant, breast milk is the primary source of nutrition, and its composition directly impacts development. The selenium from breast milk is used for the infant’s own antioxidant defenses, protecting them from cellular stress as their body grows. This antioxidant capacity is important for the healthy development of all organ systems.
Selenium intake from breast milk is also linked to the development of the infant’s immune system and thyroid. The concentration of selenium is highest in colostrum, the first milk produced, before stabilizing in mature milk. This early supply helps establish the infant’s selenium stores and supports the metabolism of thyroid hormones, which are necessary for brain development and physical growth.
Recommended Intake and Dietary Sources
For lactating women, the Recommended Dietary Allowance (RDA) for selenium is 70 micrograms per day. This is higher than for non-pregnant women to account for the mineral secreted into breast milk. Achieving this intake is manageable through a well-rounded diet, as the mother’s dietary intake directly influences the selenium concentration in breast milk.
The selenium content in plant-based foods is highly dependent on the soil in which they were grown. Good dietary sources include:
- Seafood, such as a three-ounce serving of yellowfin tuna, halibut, or sardines.
- Animal products like turkey, chicken, and beef, with a single hard-boiled egg containing about 20 micrograms.
- Brazil nuts, which are potent in selenium.
- Other nuts and seeds, like sunflower seeds, as well as whole grains and legumes.
Selenium Deficiency and Toxicity
An inadequate selenium intake can lead to health issues for both the mother and infant. In the mother, deficiency may manifest as fatigue, a weakened immune response, and impaired thyroid function. Since breast milk is the infant’s primary source of selenium, maternal deficiency can put the baby at risk for issues with immune function and brain development.
Conversely, consuming too much selenium can result in a condition known as selenosis. This is most often caused by over-supplementation rather than diet, with the notable exception of frequent, high consumption of Brazil nuts. The Tolerable Upper Intake Level (UL) for adults, including breastfeeding women, is 400 micrograms per day.
Early signs of selenium toxicity include a metallic taste in the mouth and garlic-like breath odor. More pronounced symptoms can involve hair loss, brittle nails, skin rashes or lesions, and gastrointestinal disturbances like nausea and diarrhea. Severe cases can cause neurological symptoms such as fatigue, irritability, and nerve damage.
Given the risks of both deficiency and toxicity, it is best for breastfeeding mothers to obtain selenium from a balanced diet. If there are concerns about intake or a restrictive diet is being followed, consult with a healthcare provider. A professional can assess selenium status and provide guidance on whether supplementation is necessary.