Overview

Your health and your baby’s health are top priorities. Some foods carry risks during pregnancy, and it’s important to know what to avoid and how to make informed choices. It’s easy to find long lists of foods you shouldn’t eat, but cutting these items out of your diet can be challenging, especially if they’re things you enjoy or eat regularly. Rather than simply telling you to avoid certain foods, this episode unpacks the reasons behind the recommendations so you can better understand the risks. You’ll also hear about a few foods that don’t typically appear on “do not eat” lists but may still be worth paying attention to. This episode will arm you with the knowledge you need to make confident decisions about what you are comfortable eating during pregnancy.

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Unpasteurized Foods

Pasteurization is a process that heats foods to eliminate bacteria and pathogens for safety and extends shelf life. Many of the foods that are more susceptible to harboring bacteria and pathogens are pasteurized. Unpasteurized foods primarily include milk, juices, and some cheeses.

Salmonella and Listeria

The FDA tested raw milk cheese aged 60 days for bacteria and pathogens. A total of 1,606 samples were tested. Salmonella was found in 3 samples. Salmonella is a bacteria that can be more serious when you are pregnant. While a tiny fraction of the cheeses were contaminated, this risk does exist.

Listeria was detected in 10 samples. Listeria is short for listeriosis, the foodborne illness caused by the bacterium Listeria monocytogenes. According to the CDC, An estimated 1,600 people get listeriosis each year, and about 260 die. The infection is most likely to sicken pregnant women and their newborns, adults aged 65 or older, and people with weakened immune systems. Several of the foods covered always carry a risk that they could be contaminated with listeria. Listeria can be harmful to your baby, and it is something you would not want to encounter while pregnant.

In the FDA testing, 9 of the ten kinds of cheese contaminated with listeria were soft cheeses. Soft cheeses could include feta, brie, and gorgonzola. These have a higher moisture content which makes them more susceptible to the growth of Listeria. Of these 10, 5 were domestic, three from the same manufacturer, and five were imported from other countries. The bottom line is that 0.62% were contaminated with listeria. To avoid unpasteurized cheeses, look for a label that says it is made with pasteurized milk.

You will enjoy unpasteurized juice if you squeeze oranges in your kitchen. That carries a lower risk than buying unpasteurized juice at a local farmer’s market or from another source. Most milk and juices are pasteurized and state that on the label.

Deli Meats

Many pregnant mothers are surprised to find that deli meats frequently appear on lists of foods to avoid. This is due to the chance of listeria. Deli meats include any sliced meat you would put on a sandwich. There is a massive incentive for restaurants, delis, and companies that sell deli meats to ensure their foods are safe. One of the ways companies who package deli meats try to prevent listeria is through bacteriophages, which are a virus that kills bacteria. These have been approved by the FDA since 2006 and are sprayed directly on deli meats before packaging to prevent listeria. There have been concerns about the risks of the effects of bacteriophages on your gut microbiome, but more research is needed to assess that.

You could decide to eliminate deli meats from your diet during pregnancy. Another option to eliminate the risk of listeria is to go with a hot sandwich. Heating the meat to 165° Fahrenheit (74° Celsius) will kill off any bacteria. 

Fish

ACOG recommends 2-3 servings (8-12 ounces in total) of fish per week. They recommend a maximum of six ounces of albacore tuna (commonly canned tuna). ACOG recommends avoiding fish with the highest levels of mercury and avoiding raw or undercooked fish.

Although some fish may have risks, there are also significant benefits to including fish in your diet during pregnancy. One of the most significant benefits of fish is omega 3s. One of these omega-3s, DHA, is a major structural fat in the human brain and eyes, representing about 97% of all omega-3 fats in the brain and 93% of all omega-3 fats in the retina. DHA is essential for your baby’s brain and retina development during the third trimester and up to 18 months of life. There is no universally recommended daily intake for omega 3s, and you are likely not getting much if you limit your fish to 12 ounces per week. You can mitigate this by taking a separate omega-3 supplement or a prenatal vitamin that includes DHA.

Mercury

A big concern with eating fish during pregnancy is mercury. Mercury comes from coal-fired power plants and gold mining, and naturally occurring mercury comes from the seabed. Bacteria consume mercury and convert it into methylmercury. Plankton eats the bacteria; small fish eat the plankton; large fish eat the small fish, etc. The result is that mercury accumulates in higher concentrations as it travels up the food chain. High quantities of mercury can be toxic to the nervous system.

Four fish are high in mercury to avoid, tilefish from the Gulf of Mexico, swordfish, shark, and king mackerel. If you are eating a lot of fish from a local lake or stream, check with the local advisory on the levels of mercury.

Mercury has been shown to impact the development and function of the brain and nervous system in humans. It has been blamed for developmental problems and reduced IQs in highly exposed children. The FDA has a list of Mercury Levels in commercial fish and shellfish. It is widely accepted that you want to avoid fish that are highest in mercury during pregnancy.

The risk of mercury is only half of the story. In addition to some amount of mercury, fish also contains selenium which reduces the effects of mercury toxicity. There is an argument that the ratio of selenium to mercury is a better determinant of seafood safety than just mercury content alone. In addition, some studies on prenatal and postnatal consumption of fish at high levels have not found a relationship to impaired neurodevelopment. For more in-depth information on eating fish during your pregnancy, you can listen to this episode. It also covers concerns like dioxins, PCBs, and radiation.

Sushi

There are a couple of things to keep in mind when deciding whether it is safe to eat sushi during your pregnancy. The FDA states that if fish are intended for raw or undercooked consumption, they must be properly frozen before they are served. The reason for this is that freezing the fish kills off parasites. This policy does have exceptions for some shellfish, tuna, and certain farm-raised fish. I struggled to find solid information on whether this policy is enforced or monitored. Even if fish is frozen and does not contain any parasites, it is still possible to contain bacteria or a virus. This risk can still exist even if the fish is frozen. While this risk is always present, it is a more significant concern during pregnancy. If you got a bacteria or virus from fish, it could create serious complications for your baby.

If you avoid raw fish, you still have some options to enjoy sushi. You could choose a roll with cooked fish or try a vegetarian option. It may not be the same as enjoying your favorite sushi roll, but it may satisfy your craving. See this episode for more in-depth information on sushi.

Undercooked Eggs

The same concerns about bacteria contaminating raw or undercooked fish apply to raw or undercooked eggs. The risk of a food-borne illness (think food poisoning) is always there, but with your baby on the way, you may want to be cautious or avoid it altogether.

Pesticides

Pesticides in your food don’t usually land on the do not eat list, but you may want to be cautious about them. A clinical report from the American Academy of Pediatrics on organic foods notes that lower pesticide levels may be significant for children. The risk of pesticides is one of the biggest reasons consumers choose to buy organic. I want to be clear that the health benefits of eating fresh fruits and vegetables outweigh the risk of pesticide exposure. Please do not avoid eating fruits and veggies to avoid pesticides. Children are at higher risk for pesticide toxicity than adults because their developing brain is more susceptible to neurotoxicants. Children also have lower activity and levels of enzymes that are responsible for processing toxins. Prenatal exposure is a concern because when you are pregnant, your baby goes through critical stages of development in utero.

Research has linked pesticides to ADHD in children, poorer intellectual development, working memory, and IQ as a function of prenatal exposure and structural changes in the developing human brain in children exposed prenatally to specific pesticides.

The Environmental Working Group evaluates 48 fruits and vegetables to monitor pesticide residue. The data used to create EWG’s Shopper’s Guide is from produce tested as it is typically eaten. This means washed and, when applicable, peeled. Two lists come from this data that are useful. The Dirty Dozen is the top 12 foods that rank highest for pesticides. If you want to avoid this, these are good fruits and veggies to buy organic. The Clean 15 are the 15 fruits and veggies rank the lowest in pesticide use. The non-organic versions of these fruits and veggies use a low amount of pesticides. Buying these non-organic can be an excellent strategy to save money on groceries.

Genetically Modified Organisms

If you are mindful of pesticides, you may want to pay attention to GMO foods. Overall, genetically modified crops have decreased the use of insecticides but increased the use of herbicides because many GMO crops are herbicide tolerant. That means that herbicides can be sprayed directly on crops and kill weeds without killing crops. The foods that are genetically modified are alfalfa, canola 90%, corn 88%, cotton 90%, Hawaiian papaya >50%, soy 94%, sugar beet 95%, yellow summer squash, and zucchini. A lot of animal feed is GMO because it contains corn, soy, and alfalfa.

More than 60 countries worldwide – including Australia, Japan, and all of the countries in the European Union – require GMOs to be labeled. This is something that the United States has been slow to adopt. If you would like to buy non-GMO, you can look for the Non-GMO product verified label, buy organic, or avoid foods with ingredients that are not organic and derived from GM crops. The vast majority of processed foods contain some GMO ingredients unless labeled otherwise.

The Institute for Responsible Technology has a lot of information on GMOs if you want to learn more. As a heads up, this is an organization that is very anti-GMO. The FDA also has consumer information on genetically engineered plants. The FDA holds that foods from the genetically engineered plant varieties marketed to date are as safe as comparable, non-GE foods. See this episode for more information on the pros, cons, and research on eating organic during pregnancy.

Additives in Meat

With the high consumption of meat in the Western world has come industrialization and farming that has had to grow to meet the demand. As a result, there may be some additives in the meat at your grocery store that you may want to be cautious about. Many of these additives are banned in other countries outside of the United States.

Antibiotics 

Antibiotics are microbial drugs used to treat bacterial infections. Antibiotics have been given to animals since the 40s when farmers found that giving animals a constant low dose of antibiotics caused them to gain more weight. This is called sub-therapeutic use. The meat industry holds that antibiotics are necessary for preventing, controlling, and treating diseases and infections. Farmers don’t use antibiotics 100% of the time and tend to stop using antibiotics towards the end of raising an animal to limit the amount of antibiotics in the meat.

There are maximum residue limits for antibiotics. Keep in mind the keyword here is maximum. These aren’t banned in food; they just need to remain below certain levels. One of the issues with the high use of antibiotics is that over time when bacteria come into contact with antibiotics, they can evolve to be resistant. The issue isn’t just antibiotics in the meat you eat but the antibiotic-resistant bacteria in the meat. Heating meat will kill the bacteria, but there is a lot of room for contamination before this happens. Sub-therapeutic antibiotics have been banned in the European Union and Canada, but not in the U.S. Pork has the highest use, followed by poultry, then beef. There are also antibiotics in farmed seafood.

Unfortunately, there isn’t much research on eating meat from animals treated with antibiotics during pregnancy. If you want to avoid meat from animals treated with antibiotics, you want to look for organic or something on the label explicitly stating that it was raised without antibiotics, no antibiotics ever, no antibiotics administered, no antibiotics, or no antibiotics added.

Hormones 

Hormones like Estradiol (an estrogen), progesterone, and testosterone are given to livestock through an implant in their ear. Farmers refer to these as naturally occurring hormones because animals produce them naturally. There are also synthetic hormones that are given to animals. Hormones increase the growth rate and efficiency of animals converting food into meat. Hormones are not given to pigs or chickens because they don’t have the same growth-promoting effects. When we talk about meat hormones, it is usually cows and sheep. You may still see something on the label of pork or chicken about not using hormones, which is just marketing. No one is using hormones in these animals.

rBGH

One hormone that has received much attention is rBGH (recombinant bovine growth hormone) used to spur milk production. The concern around rBGH is that it increases IGF (insulin-like growth factor) production, which has been linked to breast, prostate, and other cancers. Japan, Canada, Australia, New Zealand, and the EU have banned using rBGH. This has not been banned in the United States. It is common to see something on the label of meat or dairy products stating, “from cows not treated with rBGH.”

Like antibiotics, hormones are not banned in the United States, but maximum residue limits exist. There has been some controversy on the science of how these hormones affect humans. You know how important hormones are during pregnancy. Your hormones control everything from your cycle pre-pregnancy to your birth. Unfortunately, there are few studies on eating meat during pregnancy and what effects hormone-treated beef could have on you or your baby. See this episode for more in-depth information on eating meat during pregnancy.

Processed Meat, Nitrates, and Nitrites

Some meats are processed by smoking, curing, or adding salt or preservatives. Processed meat includes bacon, sausages, hot dogs, salami, corned beef, beef jerky, ham, canned meat, and meat-based sauces. 

The biggest concern with processed meats is a class of synthetic food preservatives that includes sodium or potassium nitrates and nitrites. These are added to cured meat to preserve color, prevent fats from going rancid, and keep bacteria from growing. When nitrites are exposed to high heat, in the presence of amino acids, they can turn into compounds called nitrosamines, which are carcinogenic and have been linked to causing cancer. Manufacturers are required to limit the amount of nitrites they use. They are also required to add Vitamin C, which inhibits nitrosamine formation.

A study that examined maternal dietary intake of nitrates, nitrites, and nitrosamines and selected congenital disabilities in offspring looked at things like cleft lip and physical defects. This study has a large sample size, with over 6,000 participants, and the researchers didn’t find sufficient evidence to link nitrates and nitrites eaten during pregnancy to congenital disabilities. Some epidemiologic studies suggest that maternal consumption of cured meat during pregnancy may increase the risk of brain tumors in offspring.

One study examined how some genes could impact a baby’s ability to deal with these carcinogenic compounds. This research did an excellent job of summing up some of the other studies linking nitrates and nitrates to brain tumors in children. There are also nitrates in vegetables. So it is unlikely you are avoiding these altogether. Although vegetables generally aren’t cooked at high temperatures, like a hotdog or bacon.

If you want to avoid synthetic nitrates and nitrites, you can purchase organic, which does not allow these. You can also look for labels stating that the processed meat you buy does not contain nitrates or nitrites.

Finding Solutions that Work for You

You always have the option to play it as safe as possible and avoid foods covered in this article. You can employ a few strategies to enjoy some of these foods while avoiding or mitigating risks. One tool to evaluate foods you should be cautious about is to weigh the risks and the benefits. The benefit may outweigh the risk depending on how much you want that sushi roll. You can use alternatives like a veggie roll to enjoy sushi without the risk of eating raw fish. Knowing the source of your foods can mitigate your risks. The concern of food contaminated with bacteria may be lower in a restaurant you have been going to for years than in an establishment you are not familiar with.

It is easy to go down the rabbit hole of overanalyzing everything you eat. For some of the foods in this article, the dose matters. There is a big difference in the amount of nitrates or nitrites you consume if you eat bacon daily than if you enjoy it once or twice a week. You can buy organic produce to avoid pesticides at home, but you may not have the option of organic if you eat at a restaurant or a friend’s house. Even if pesticides are a concern for you, you can mitigate your risk by mostly eating organic and not panicking if you eat something that isn’t.

If you feel like you cannot live without something we discussed today, you should have some good tools to evaluate your risks. If you decide to limit or cut out something you love, like cheese boards or sushi, I know this seems impossible now. You are only pregnant for nine months. This period of being cautious about everything you consume is short and gets easier over time. 

More In-Depth Information on Foods During Pregnancy and Breastfeeding

Many episodes of the Pregnancy Podcast examine the evidence on the risks and benefits of specific foods during pregnancy. Check out these episodes for in-depth information on the following topics:

• Nutrition and the Evidence on Popular Diets During Pregnancy
• The Truth About Protein in Pregnancy and Supplementing with Protein Powder
• Eating Meat During Pregnancy
• Eating Fish During Pregnancy
• Navigating Pregnancy Nutrition on a Vegetarian or Vegan Diet
• Eating Organic During Pregnancy
• Your Guide to Sugar During Pregnancy
• An Evidence-Based Guide to Natural and Artificial Sweeteners During Pregnancy
• Omega 3 and Fish Oil Supplements During Pregnancy
• Probiotics and Gut Health During Pregnancy
• Eating Deli Meat During Pregnancy
• Sushi

Talking to Your Doctor or Midwife

If you have questions about whether a food or drink is safe, please bring it up with your doctor or midwife. Don’t be afraid to ask why something is off-limits. You can also ask what the risks are of consuming it so you can better make an informed choice.

Thank you to the amazing companies that have supported this episode.