How mercury from fish can get into your breast milk

There are traces of mercury in virtually every kind of fish and shellfish. But the big fish contain higher levels that may contaminate the breast milk of a nursing mother and damage the developing brain of the baby.

Nursing mothers should avoid eating fish high in mercury.

What is mercury?
Mercury is a type of metal found naturally in the environment. However, human industrial activities, such as farming, burning coal, and manufacturing contribute to higher mercury levels. As a result, fish receive a higher amount of mercury and pass it on to humans when consumed. A high level of mercury is harmful to a baby’s brain development.

Larger fish generally possess a greater mercury level than small fish because they prey on large amounts of small fish. And the longer life span of big fish gives them time to accumulate mercury in their system.

How does it harm Your Child?
Mercury accumulates in your bloodstream over time and slowly leaves the body through urine, feces, and breast milk. If you eat a lot of fish high in mercury, it may take up to a year for your mercury levels to drop. While elevated levels of mercury usually do not cause significant health problems, they may affect your child’s brain development. 

Should I stop eating fish while breastfeeding?
Generally, fish and shellfish are healthy foods. They are low in saturated fat and contain high-quality protein and other essential nutrients. They also contain omega-3 fatty acids, a type of essential fatty acid. A balanced diet that includes fish and shellfish can contribute to a healthy heart and children’s growth and development. 

How much fish and what kind of fish should I eat?
Sharks, swordfish, king mackerel, and tilefish contain high levels of mercury; do not eat any of them. Instead, you can eat up to 340 g a week (two average meals) of a variety of fish and shellfish that are lower in mercury. The five most commonly eaten fish that are low in mercury are shrimp, canned light tuna, salmon, pollock, and catfish.