To fully harness the nutritional advantages of tuna while minimizing potential risks, it is advisable for pregnant women to consume only cooked tuna and to steer clear of varieties that are known for their elevated mercury content. Tuna is widely recognized as a rich source of essential nutrients, many of which are particularly vital during the pregnancy phase.

For example, it is often lauded for its significant levels of eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) — two long-chain omega-3 fatty acids that are instrumental in the development of your baby's brain and nervous system. However, it is important to note that various types of tuna also harbor high mercury levels, a substance associated with numerous health and developmental issues in infants. Consequently, women are frequently advised to limit their tuna intake during pregnancy.

This article explores the safety of consuming tuna during pregnancy and discusses appropriate portion sizes.

Tuna Offers Essential Nutrients Vital for a Healthy Pregnancy

Tuna is a powerhouse of essential nutrients, many of which are particularly beneficial during pregnancy. The key nutrients found in substantial amounts include:

  • Protein. This macronutrient is crucial for all stages of growth. Insufficient protein intake during pregnancy can lead to serious complications such as miscarriage, intrauterine growth restrictions, and low birth weight. Conversely, an excessive intake of protein may also result in similar adverse effects.
  • EPA and DHA. These long-chain omega-3 fatty acids are essential for the development of the baby's eyes and brain. Incorporating these omega-3s into your diet may additionally lower the risk of preterm birth, inadequate fetal growth, maternal depression, and childhood allergies.
  • Vitamin D. Tuna contains moderate levels of vitamin D, which is important for immune function and bone health. Maintaining adequate vitamin D levels may also decrease the likelihood of miscarriage and preeclampsia, a pregnancy complication characterized by elevated blood pressure.
  • Iron. This essential mineral plays a significant role in the healthy development of your baby’s brain and nervous system. Sufficient iron intake during pregnancy might also lower the chances of low birth weight, preterm birth, and maternal mortality.
  • Vitamin B12. This vital nutrient supports optimal nervous system function and aids in the production of protein and oxygen-carrying red blood cells. Low levels during pregnancy can increase the risk of miscarriage, preterm birth, birth defects, and other complications.

A serving size of 100 grams (approximately 3.5 ounces) of light canned tuna contains roughly 32% of the Reference Daily Intake (RDI) for protein, 9% of the Daily Value (DV) for iron, and an impressive 107% of the DV for vitamin B12. This serving also provides about 25 mg of EPA and 197 mg of DHA, which equates to approximately 63–100% of the daily intake recommended by most experts for pregnant women. For pregnant women who avoid tuna due to food allergies, or for religious or ethical reasons, it is important to seek alternative sources to meet these nutrient needs.

They may also consider taking a daily supplement that provides at least 200 mg of DHA or a combination of 250 mg of EPA plus DHA each day. Tuna serves as a convenient source of protein, long-chain omega-3 fatty acids, vitamin D, iron, and vitamin B12. Ensuring adequate intake of these nutrients during pregnancy can minimize the risk of complications and enhance birth outcomes.

Potential Risks of Tuna Consumption During Pregnancy

While many health experts advise that women who typically consume tuna may continue to do so throughout their pregnancy, they also emphasize the importance of moderation due to the fish's mercury content. High levels of mercury can pose risks to fetal development. Mercury, although a naturally occurring element, is predominantly found in fish due to industrial pollution, and its concentration in aquatic life has shown a troubling increase annually.

All fish contain some level of mercury; however, larger, older fish that sit higher in the food chain tend to accumulate more. Tuna, being a predatory species, can grow both large and old, resulting in significant mercury levels in their tissues. Excessive mercury intake during pregnancy can adversely affect the development of the baby's brain and nervous system, leading to various complications, including:

  • learning difficulties
  • delayed motor skills development
  • issues with speech, memory, and attention
  • impaired visual-spatial skills
  • lower intelligence quotients (IQs)
  • increased risk of high blood pressure or cardiovascular issues in later life

In extreme circumstances, elevated mercury levels during pregnancy can result in a loss of smell, vision, or hearing in infants, along with potential birth defects, seizures, coma, or even infant mortality. Interestingly, some studies have indicated that mercury exposure during the early stages of pregnancy may not adversely affect a child's behavioral and cognitive development, provided the mother consumes fish regularly throughout her pregnancy. This finding suggests that certain beneficial compounds present in fish might mitigate the harmful effects associated with mercury. However, further research is necessary to validate these claims. Additionally, it is crucial for expecting mothers to steer clear of raw tuna to reduce the risk of contracting Listeria monocytogenes, a bacterium capable of severely impacting an infant’s growth and overall development.

What is the Safe Limit of Tuna Consumption During Pregnancy?

The issue of mercury exposure is one that builds up over time, and various fish species contain differing levels of mercury. Therefore, the Food and Drug Administration (FDA) recommends that expectant mothers aim to eat 8–12 ounces (approximately 225–340 grams) of fish and seafood weekly. This intake should include no more than one of the following options:

  • 12 ounces (340 grams) of canned light tuna or other low-mercury options such as anchovies, cod, tilapia (tilapia), or trout.

Alternatively, you may consider:

  • 4 ounces (112 grams) of yellowfin, white, or albacore tuna, as well as other medium-mercury varieties like bluefish, halibut, mahi-mahi, tilefish, or snapper.

In addition, pregnant women are strongly advised to completely avoid high-mercury fish types like bigeye tuna, swordfish, shark, marlin, orange roughy, king mackerel, and tilefish. Numerous global food safety organizations have also put forth guidelines on tuna consumption for pregnant women. While many of these recommendations echo the FDA's advice, the specific types of tuna deemed safe can differ from one country to another.

The Bottom Line

Tuna is not only a convenient source of essential nutrients but is particularly beneficial during pregnancy due to its high content of vital minerals and vitamins. Nonetheless, certain types of tuna can harbor elevated levels of mercury, a toxic element that poses risks to your baby's health and may lead to various developmental issues. Additionally, consuming raw tuna increases the likelihood of contracting a Listeria infection, which can be particularly dangerous.

To reap the nutritional benefits of tuna while minimizing potential risks, pregnant women are advised to steer clear of raw tuna. Instead, they should opt for varieties that are lower in mercury, as well as other fish options, while avoiding those known to have high mercury concentrations. For women who refrain from consuming tuna due to allergies or for ethical or religious reasons, including a long-chain omega-3 supplement in their diet can be a beneficial alternative.