The importance of nutrition during pregnancy not just for the health of the mother, but that of her infant as well, has long been recognized (Procter & Campbell, 2014). As pork is the most widely eaten meat worldwide, can it also be safe for consumption by women while pregnant?
Pork meat is a nutrient-dense source of protein and essential amino acids, and is an important component of a balanced diet in pregnancy. As long as it has been properly cooked, pork can be safely consumed by pregnant women.
This article demonstrates the importance of proper nutrition during pregnancy. Next, it will discuss the different pathogens that may be present in pork meat and the dangers of developing food borne diseases from them. Recommendations regarding pork consumption during pregnancy will follow. Lastly, some tips on pork meat safety will be given.
Proper Nutrition During Pregnancy
The Academy of Nutrition and Dietetics recommends women of childbearing age to adopt a lifestyle that would optimize their health and reduce the risk of birth defects, suboptimal fetal development, and chronic health illnesses in both mother and infant. Factors leading to healthy pregnancy outcomes include the following (Procter & Campbell, 2014):
- Healthy pre-pregnancy weight
- Appropriate weight gain and physical activity
- Consumption of different varieties of food
- Proper vitamin and mineral supplementation
- Avoidance of alcohol and other dangerous substances
- Safe food handling
Nutritional needs increase during pregnancy to be able to support fetal growth and development, on top of alterations in maternal tissues and metabolism (Picciano, 2003). Requirements for energy and protein are particularly higher during the second and third trimesters of pregnancy (Murphy et al., 2021).
The recommended dietary allowance (RDA) for protein intake during pregnancy is 46 grams per day (0.8 gram/kilogram body weight/day) during the first trimester, and 71 grams per day (1.1 gram/kilogram body weight/day) during the second and third trimesters (Murphy et al., 2021).
This is comparable to the nutrient requirement set by the nutrition societies of Germany, Austria and Switzerland (D-A-CH) for protein intake during pregnancy, which is 0.8, 0.9, and 1 gram per kilogram body weight per day during the first, second and third trimesters, respectively (Murphy et al., 2021).
This means that additional protein requirements from pre-pregnancy state are 1, 9, and 28 grams per day, respectively by trimester of pregnancy as recommended by the European Food Safety Authority (EFSA), or an additional 1 gram per day during the first trimester, and an increase of 21 grams per day in the second and third trimesters as derived by the Institute of Medicine (IOM) (Murphy et al., 2021).
Pork is an excellent source of high-quality protein, iron and zinc. It is also rich in many vitamins and minerals, and contains all nine essential amino acids. Lean meat can, thus, be a healthy addition to a pregnant woman’s diet.
According to the U.S. Department of Agriculture (USDA, 2019), 100 grams of cooked, fresh loin pork contains 26 grams of protein. Meanwhile, according to the British Nutrition Foundation, grilled lean pork can contain up to 32 grams of protein per 100 grams.
Food Borne Pathogens in Pork
Pork meat is an excellent substrate for the growth of microorganisms because of its composition and poor hygiene practices at the point of sale. The pathogenic bacteria Escherichia coli, Staphylococcus aureus, Clostridium, and Salmonella are all found in pig meat (Alfred et al., 2019).
According to the Food and Agriculture Organization (FAO), pork is the most regularly consumed meat in the European Union (EU) in 2017. Among different categories of food, pork products are the second highest cause of meat borne diseases in 2019 (Hdaifeh et al., 2020).
In the Republic of Côte d’Ivoire, pork meat is a valued food because of its good nutritional values and high digestibility. In their economic capital of Abidjan, there is even a special market called “Gabriel Gare,” which is dedicated to selling pork meat (Alfred et al., 2019).
A consumption survey in Côte d’Ivoire was conducted by Alfred et al. in 2019, which found that 52 percent of pork meat consumers has had at least one instance of gastrointestinal discomfort (vomiting, diarrhea, stomach ache) after eating pork. Analyzed commercial pork meat samples revealed Staphylococcus aureus, fecal coliforms and mesophilic aerobic germs.
Meat products are highly perishable with colonization of a variety of microorganisms, specifically bacteria. This is because of the complex nutrient-rich environment in meat with chemical and physical conditions favorable to bacterial development (Cauchie et al., 2019).
There are also several possible sources of contamination in the pork meat chain from farm to human consumption. These include direct contact with the infected pork, by contamination in the environment of the farm, at slaughtering, during processing, retail, preparation and consumption (Hdaifeh et al., 2020).
Pork meat and pork-based products are a frequent source of food borne diseases in humans, including those due to Salmonella, Yersinia enterocolitica, Toxoplasma gondii, Trichinella (EFSA Panel on BIOHAZ, 2013), Hepatitis E virus (HEV) (Casas & Martin, 2010), and Listeria monocytogenes.
L. monocytogenes is a food borne pathogen that causes severe infections in humans. It is ubiquitous in nature and can adhere to surfaces and form biofilms. It is also able to survive and grow at low temperatures, a wide range of pH, high salt concentrations, and low water activity (Li et al., 2018).
It can persist in food processing environments, leading to recurrent contamination of final products (Li et al., 2018). It causes the infection listeriosis, which is one of the most severe food borne diseases (Matle et al., 2020) transmitted to humans through consumption of contaminated food (Félix et al., 2018; Hilliard et al., 2018).
The majority of meat products that were involved in outbreaks and sporadic cases of listeriosis include processed and vacuum-packaged meat, pork tongue, sausages, and polony (a smoked sausage made from pork and beef) (Matle et al., 2020). In Bangkok, the prevalence of L. monocytogenes in marketed raw meats was 15.4 percent (Indrawattana et al., 2011).
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Pork meat has been regularly reported as being contaminated by L. monocytogenes, with a prevalence rate of up to 12 percent in raw products. In France, the pork production sector has been involved in a series of outbreaks related to L. monocytogenes food poisoning from 1992 to 2015 (Félix et al., 2018).
In China, high levels of contamination of L. monocytogenes in raw pork have been reported. In 2016, a retail market in China was examined. Results showed that overall, 15.2 percent of the samples taken were found to be contaminated, including raw pork samples, contact surface swabs, and insect samples, suggesting long-term and cross-contamination (Li et al., 2018).
Listeriosis can be difficult to control and can result in severe clinical outcomes (Maertens de Noordhout et al., 2014). It has a high case fatality rate (Hilliard et al., 2018), and ranks among the most important food borne infections in Europe in terms of disease severity and fatality (Eurosurveillance editorial team, 2015). In France, Listeriosis has the highest mortality rate (20-30%) and hospitalization rate (98.9%) among all food borne illnesses (Félix et al., 2018).
Maertens de Noordhout et al. (2014) estimated that in 2010 alone, listeriosis has caused more than 23 thousand illnesses and more than 5 thousand deaths, the proportion of perinatal cases of which are up to almost 21 percent. In China, a total of 256 cases of Listeriosis have been reported from 1964 to 2013, of which 48 were pregnant women and 86 were newborns (Li et al., 2018).
Listeriosis causes a wide spectrum of infections, which can be categorized into two forms: invasive listeriosis and non-invasive febrile gastroenteritis (Matle et al., 2020). Invasive listeriosis mostly occurs in immunocompromised patients and manifests as sepsis, meningitis, endocarditis, encephalitis, meningoencephalitis, septicemia and brain infection (Doganay, 2003). It is responsible for over 90 percent of hospitalizations and its mortality rate can be as high as 30 percent (Leong et al., 2014).
Non-invasive gastroenteritis can manifest as fever and watery diarrhea lasting for 2 to 3 days, often accompanied by headache and backache (Mateus et al., 2013). Less common forms of listeriosis in humans are in the form of endocarditis, hepatitis, myocarditis, arteritis, sinusitis, conjunctivitis, ophthalmitis and joint infections (Amato et al., 2017).
The clinical signs of listeriosis often appear after a long incubation period of up to 70 days (Matle et al., 2020). In 2008, Goulet et al. reported that incubation periods of listeriosis are highly influenced by its clinical forms. However, the longest incubation time observed happened among cases of pregnant women (with a median of 27.5 days).
Pregnant women have a 17-fold increased risk of developing invasive listeriosis, and it occurs most commonly during the third trimester of pregnancy (Mateus et al., 2013). In pregnant women, listeriosis is generally associated with flu-like symptoms with or without gastrointestinal manifestations (Doganay, 2003). However, the complications of fetal or newborn infections are extremely severe, which includes abortion, premature birth, pneumonia, meningitis (Indrawattana et al., 2011), and sepsis (Mateus et al., 2013; Li et al., 2018).
With a high disease burden, T. gondii ranks worldwide among the most important food borne pathogens (Scallan et al., 2015). It causes toxoplasmosis, which poses the greatest disease risk among all food borne parasitic infections worldwide (Sroka et al., 2019). About 30 percent of the human population are chronically infected with toxoplasmosis (Robert-Gangneux & Darde, 2012).
Toxoplasmosis can be acquired through ingestion of contaminated raw or undercooked meat containing T. gondii tissue cysts (Tenter et al., 2000). Pork meat and pork meat products are considered as important risk factors for infection (Sroka et al., 2019).
Sroka et al. (2019) found that the prevalence of T. gondii in meat products, including sausages, smoked meat, ham, and minced meat, ranged from 4.5 to 5.8 percent. In Poland, the prevalence of T. gondii infection in pigs is at 11.1 to 14.3 percent.
However, with intensive farm management, research has shown that the prevalence of T. gondii in meat has decreased considerably over the past 20 years. In countries of the European Union, the prevalence of T. gondii in pigs are now less than 1 percent (Tenter et al., 2000).
Nevertheless, if contracted during pregnancy, T. gondii can be transmitted vertically via the placenta to the fetus (Tenter et al., 2000), to cause a congenital infection (Robert-Gangneux & Darde, 2012). Congenital toxoplasmosis causes a severe disease, with cerebral and ocular damage in newborns (Sroka et al., 2019).
Salmonellosis remains one of the most common food borne infections globally. Non-typhoidal Salmonella causes more than 93 million cases of human illnesses and 155 thousand deaths every year worldwide (Campos et al., 2019). In the U.S., majority of deaths from food borne illnesses were due to Non-typhoidal Salmonella (28%) (Scallan et al., 2011).
Salmonella was the second most common food borne pathogen associated with outbreaks in the U.S. according to the 2015 report from the Centers for Disease Control and Prevention (CDC), and the most frequent cause in the European Union (EU) according to the EFSA (Campos et al., 2019). In 2018, Salmonellosis was also the second most commonly reported zoonotic infection among 36 European countries (EFSA and ECDC, 2019).
The most frequent sources of Salmonella infection are food products of animal origin, with pork being the most relevant (Campos et al., 2019). Pork meat is estimated to account for 20 percent of cases of food borne Salmonellosis worldwide (Hoffmann et al., 2017), while the most frequent bacterium identified in pork is also Salmonella (Hdaifeh et al., 2020).
Pigs are important reservoirs of Salmonella, which can be found in the digestive and lymphatic tissues. Pork is a key vector of transmission because live pigs exhibit no symptoms of infection (EFSA Panel on BIOHAZ, 2013). Salmonellosis is also the most common infection acquired from pork meat (EFSA and ECDC, 2019).
In 2015, an outbreak of Salmonella has been associated with consumption of contaminated pork (Lianou et al., 2017). In the EU, pork has been a common source of cases of Salmonellosis infections ranging from 2 to 13 percent. In the USA, pork meat was the second most frequent source of Salmonella outbreaks (5%) and the most commonly associated with the highest number of illnesses (16%), hospitalizations (2%) and deaths (11%) (Campos et al., 2019).
Salmonellosis is commonly manifested as a self-limiting syndrome of gastroenteritis, with diarrhea as its main symptom. Fever, vomiting, and abdominal pain may also occur (Campos et al., 2019).
Clostridium perfringens is commonly found in meat products, such as pork, beef and chicken, through fecal contamination of carcasses, contamination from other ingredients (like spices), or post-processing contamination. Meat products that have been associated with Clostridium botulinum illness include meat roll, pork sausage, home-cured ham, and reheated chicken (Lianou et al., 2017).
In 2006, an outbreak of Clostridium botulinum in Austria has been linked to barbequed pork as the most likely source of infection (Meusburger et al., 2006).
Yersiniosis was the fourth most commonly reported zoonotic infection in the EU in 2018 (EFSA and ECDC, 2019). Animals are the principal reservoir of Y. enterocolitica, and slaughtered pigs are its single most important source (Lianou et al., 2017).
Because of its high association with pigs, raw pork meat and its products have been extensively investigated as potential transmission routes for Yersiniosis to humans. However, Y. enterocolitica has only rarely been recovered from raw or undercooked pork samples (Lianou et al., 2017).
Hepatitis E Virus
HEV is transmitted to humans from domestic pigs, wild boar and deer. Food borne transmission occurs by consumption of raw and undercooked meat from infected animals (Szabo et al., 2015). The presence of HEV has been demonstrated in pig liver, pork meat and their products (sausages), which are important vehicles of foodborne HEV infection (Lianou et al., 2017).
In 2015, Szabo et al. detected HEV in 20 percent of raw sausages and 22 percent of liver sausages for retail in Germany.
Recommendations on Pork Consumption During Pregnancy
According to the NHS, pork meat can be safely eaten during pregnancy, as long as they were well cooked with no trace of pink or blood. Similarly, according to the NSW Food Authority, cooked pork can be safely consumed as long as they were thoroughly heated to at least 71 degrees Celsius and eaten while still hot. Both NHS and NSW Food Authority recommend avoidance of any raw or undercooked pork meat because of the risk of developing food borne illnesses.
According to the U.S. Food and Drug Administration (US FDA, 2020), all raw pork should be cooked to 145 degrees Fahrenheit with a 3-minute rest time after removal from the heat source. “Resting cooked meat allows the juices, which have been driven by cooking to the center of the meat, to be reabsorbed throughout the meat.”
For ground pork mixtures, cooking to an internal temperature of 160 degrees Fahrenheit is recommended, with no further rest time needed (US FDA, 2020). Raw cured meats, like prosciutto, chorizo, pepperoni and salami, should also be avoided unless they were thoroughly cooked. A food thermometer can be used to check that the meat has reached the recommended safe minimum internal temperature.
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Tips on How to Keep Pork Meat Safe for Consumption
According to the U.S. FDA (2020), the four basic steps to food safety are the following:
- Wash hands before and after handling food.
- Wash cutting boards, dishes, utensils, and counter tops in between preparation of raw pork meat.
- Use paper towels to clean up kitchen surfaces. If using cloth towels, wash them often in the hot cycle of the washing machine.
- Separate raw pork from other foods in shopping carts, grocery bags, and in the refrigerator.
- Place raw pork meat on the lowest shelf in the refrigerator so that the juices will not drip on other foods that will not be cooked.
- Never place cooked food on a plate or cutting board that previously held raw meat.
- Use a food thermometer to measure the internal temperature of cooked foods, and check in several places of the meat.
- Bring sauces, soups, and gravy to a boil when reheating. Heat other leftovers to 165 degrees Fahrenheit.
- Refrigerate or freeze pork meat within 2 hours of cooking or purchasing.
- Never thaw food at room temperature, such as on the counter top.
- It is safer to thaw food in the refrigerator, cold water, or microwave.
Pork is an excellent source of high-quality protein and a healthy addition to a balanced diet during pregnancy. However, there are many pathogens that are potentially present in raw pork meat that can cause devastating consequences to the mother and fetus.
Therefore, properly cooking pork according to the recommended safe temperature is needed before consumption by any pregnant woman. Steps to follow for food safety should also be practiced diligently when dealing with any kind of meat product.
A consultation with a physician is best to alleviate any dietary concerns during pregnancy.