Food Poisoning

Science of Food Nutrition and Health

Vinod Puri

(Publishers: Austin Macauley Publishers, London, 2023)

Food Poisoning

Foodborne illness, also known as food poisoning, occurs when individuals consume foods or beverages that have been contaminated with bacteria, viruses, parasites, or toxic substances. It is a significant public health issue, affecting more than 10% of the global population annually. While most cases of foodborne illness resolve on their own, some can lead to serious complications such as neurological disorders, kidney and liver issues, paralysis, and potentially cancer.

Symptoms of food poisoning can vary and may include diarrhea, vomiting, abdominal pain, bloating, and fever. According to the World Health Organization (WHO), billions of people become ill each year and many die due to the consumption of unsafe food.

There are over 250 identified foodborne diseases, including:

Enteric diseases

These are caused by bacteria and viruses found in contaminated food. Some common bacteria associated with foodborne illnesses include:

  • Brucella spp., found in unpasteurized milk and meats, can cause diseases like Bang fever, Mediterranean fever, and Maltese fever.
  • Bacillus bacteria in uncooked foods can lead to emetic and diarrheal food poisoning.
  • Campylobacter bacteria are a common cause of gastroenteritis and diarrhea.
  • Clostridium botulinum, found in improperly canned or preserved foods, can cause botulism. Clostridium perfringens in raw meats and poultry can cause food poisoning.
  • Cryptosporidium causes food poisoning when fluids or foods contaminated with faecal matter are consumed.
  • Enteropathogenic (E. coli) bacteria can cause haemorrhagic colitis and are commonly found in uncooked ground beef, unpasteurized milk, and unwashed fruits and vegetables.
  • Listeria monocytogenes can cause listeriosis and severe illness, thriving in unpasteurized milk, soft cheeses, and ready-to-eat foods.
  • Salmonella, commonly found in contaminated food and water, can cause diarrhea, fever, and abdominal pain.
  • Staphylococcus aureus, transmitted through meat, eggs, or contact with infected objects, can lead to food poisoning and endocarditis.
  • Vibrio bacterial species, found in contaminated water, fish, shellfish, and leftover cooked grains, can cause diarrhea.




On the other hand, Viruses are basic microscopic infectious agents made up of RNA or DNA surrounded by a protective protein layer. Viruses require a host to replicate and proliferate. By infiltrating the cells of living organisms, viruses replicate quickly within the host cells. In certain instances, viruses can harm the host cells, while in others, they prompt the host cells to multiply without causing harm.
 

Viruses are ubiquitous and can be transmitted through airborne contact or by consuming contaminated food and fluids. Some viruses that cause foodborne illnesses include:

• Hepatitis A Virus, which is typically spread through food and water contaminated with faeces, especially shellfish grown in polluted water. Hepatitis A outbreaks are frequent, infecting thousands of individuals annually and leading to fatalities.

• Norovirus, a highly contagious virus that is responsible for over 85% of non-bacterial gastroenteritis outbreaks. It spreads easily from person to person through aerosolized particles from infected individuals' faeces or vomit, contaminated food and water, and sharing utensils with infected individuals.

• Rotavirus A primarily affects children aged 6 months to 5 years and is a leading cause of gastroenteritis. Rotavirus B and C can also cause gastroenteritis in adults. Transmission occurs through the faecal-oral route, contaminated food and fluids, contaminated surfaces, and aerosolized particles.

• Astrovirus commonly causes acute diarrhea in children and is typically transmitted through contaminated food and water via the faecal-oral route.

Parasitic Diseases

Parasites are organisms that rely on other living organisms for sustenance. They can be single-cell microscopic organisms like protozoa or more complex multicellular organisms like worms. Parasitic diseases, also known as 'parasitosis,' are caused by these organisms feeding off their hosts. They are most common in warm, humid environments, especially in tropical, subtropical, and temperate regions. Parasitic infections often result in intestinal illnesses such as diarrhoea and vomiting, along with symptoms like muscle aches, fatigue, and vomiting. These infections are typically caused by consuming contaminated water, undercooked meats, or contaminated soil. Recognizing the significant impact of parasitic infections, the WHO/FAO conducted extensive research to identify the top 10 food-borne parasites based on their burden on human health and estimates of incidence, mortality, and previous disease consequences. Some of the key parasites of interest include:

• Taenia solium (pork tapeworm) is typically contracted from consuming raw or undercooked pork, leading to a mild infection known as cysticercosis.

• Echinococcus granulosus (Hydatid worm or dog tapeworm) is commonly spread through dogs and their faeces, causing intestinal infections that may result in allergies, nausea, coughing, or vomiting.

• Echinococcus multilocularis (Tapeworm) can be transmitted through fresh produce and contact with wild foxes, dogs, and cats, potentially causing echinococcosis with symptoms such as pain, distension, nausea, vomiting, chest pain, shortness of breath, headache, or stroke-like symptoms.

• Toxoplasma gondii (protozoa) can be contracted by consuming undercooked or parasitic encysted meats, contaminated water, or cat faeces, as well as oysters, clams, and mussels, leading to toxoplasmosis with symptoms like swollen lymph glands, muscle aches, headache, fever, inflammation of the lungs, heart muscle, or retina.

• Cryptosporidium (protozoa) can cause diarrhea and is typically transmitted through drinking water, juices, or milk contaminated with faeces, or foods washed with contaminated water.

• Entamoeba histolytica (protozoa) is responsible for amoebic dysentery and colonic ulceration, transmitted through the faecal-oral route by consuming raw foods contaminated with or washed in contaminated water.

• Trichinella spiralis (nematode) causes trichinosis when consuming undercooked meats, particularly from domestic pigs, with symptoms including nausea, diarrhea, and abdominal pain.

• Opisthorchildae (flatworms) can be contracted by consuming raw or undercooked fish, leading to symptoms like indigestion, nausea, abdominal pain, diarrhea, fever, and jaundice.

• Ascaris spp (intestinal roundworms) are typically transmitted through the faecal-oral route by consuming contaminated food and water, resulting in ascariasis with symptoms such as fever, abdominal swelling, and diarrhea.

• Trypanosoma cruzi (protozoa) causes Chagas disease, which can become serious if chronic and lead to heart disease. It is generally transmitted through mammals like dogs and cats and via the faecal-oral route by ingesting contaminated fruit juices.

Chemical and Toxins

Chemicals and toxins are another group of disease-causing factors linked to food. Some naturally occurring toxins include mycotoxins, marine biotoxins, cyanogenic glucosides, and toxins present in certain types of mushrooms. Moreover, numerous chemicals used in food processing, packaging, fertilizers, agricultural products, and industrial byproducts have been detected in food chains globally. These chemicals can build up in animal or human body fat, and prolonged exposure has been associated with reproductive and developmental issues, cardiovascular disease, diabetes, and cancer.

Natural Toxins: Bacteria and fungi present in food can generate toxins that are not eliminated by cooking, freezing, smoking, or curing. We regularly ingest a wide range of foods containing these toxins, which is difficult to avoid. While small amounts of these toxins are generally not harmful to our health, there is a risk of toxicity from allergies, contamination, or excessive consumption. Some of the well-known toxins known to cause health problems in humans include:

  • Mycotoxins, which are secondary metabolites of filamentous fungi, can grow on a variety of crops and foods such as grains, nuts, fruits, juices, etc under warm and humid conditions. Some notable mycotoxins include:
    • Aflatoxins, commonly found in corn, peanuts, and cottonseed crops, are known to cause hepatic disease, vomiting, abdominal pain, oedema, convulsions, and even death in high doses. Aflatoxin B1 has been classified as a human carcinogen by the International Agency for Research on Cancer (IARC).
    • Ochratoxins, produced by certain molds of Aspergillus and Penicillium, are most notably represented by Ochratoxin A, a potent mycotoxin that can be found on barley, oats, rye, wheat, and other plant products. It is believed to be genotoxic (causing DNA damage) and teratogenic (harmful to the fetus).
    • Fusarium toxins, which are plant pathogens, are associated with opportunistic infections of the eyes, skin, and nails, and may lead to systemic infections in individuals with weakened immune systems.
  • Cyanogenic glucosides are naturally occurring compounds found in many foods, especially cassava, a staple food in developing countries that contains significant levels of cyanogenic glucosides. Sweet cassava contains approximately 50mg/kg, while bitter cassava can contain up to 400mg/kg of hydrogen cyanide. Consumption of cassava has been linked to cyanide poisoning, resulting in various symptoms ranging from mild discomfort to serious conditions like konzo, a neurological disorder characterized by gait abnormalities, leg stiffness, and paralysis. Apart from cassava, apricot kernels contain around 0.5mg/kernel of cyanide, which can also lead to cyanide poisoning if ingested.
  • Marine biotoxins, including shellfish toxins and ciguatoxins, are among the most potent toxins produced by phytoplankton during harmful algal blooms. Shellfish toxins are classified into five categories based on the type of intoxication and human reactions:
    • Paralytic shellfish toxins lead to paralytic shellfish poisoning (PSP) when shellfish such as clams, mussels, oysters, cockles, scallops, and lobsters, which consume specific types of dinoflagellates and a species of blue-green algae containing PSP toxins, are ingested.
    • Diarrhoeic shellfish toxins cause diarrhoeic poisoning (DSP) when contaminated shellfish are ingested resulting in diarrhoea, nausea, vomiting, and abdominal pain.
    • Amnesic shellfish toxins result in amnesic shellfish poisoning (ASP) by consuming contaminated shellfish. ASP causes abdominal cramps, vomiting, disorientation, and memory loss in humans.
    • Neurotoxic shellfish toxins lead to neurotoxic shellfish poisoning (NSP) when contaminated shellfish are consumed. Symptoms of NSP in humans include asthma-like symptoms, nausea, vomiting, tingling sensations in the mouth, lips, and tongue, slurred speech, and dizziness.
    • Azaspiracid shellfish toxins result in Azaspiracid shellfish poisoning (AZP) when contaminated shellfish with dinoflagellate Protoceratum crassipes are consumed. AZP symptoms may include stomach cramps, nausea, vomiting, and severe diarrhoea.
  • Ciguatoxins are produced by dinoflagellates (Gambierdiscus toxicus) which thrive in tropical or subtropical seawaters. Ciguatera poisoning occurs by the ingestion of reef fish affecting the gastrointestinal tract (nausea, vomiting, diarrhoea, and abdominal pain), nervous system paresthesias (pins and needles), pruritus (itching of the skin) respiratory paralysis, hypertension, bradycardia (slow heart action), myalgia (muscle pain), and pulmonary oedema (excessive fluid in lungs)
  • Scombroid poisoning is caused by eating fish from the Scombridae family, including tuna, herring, mahi-mahi, dolphin, mackerel, sardines, and others contaminated with bacteria that produce high levels of histamine. Symptoms of scombroid poisoning can include facial and neck redness, sweating, palpitations, dizziness, burning or tingling in the mouth, headaches, and more. Individuals with asthma may experience more severe symptoms.

 

Chemical Contaminants: Chemical contaminants are substances that are not naturally found in food but are deliberately introduced during food processing and production. Additionally, chemical contaminants can enter the food supply through packaging materials, transportation, and storage. These contaminants can come from sources such as air, water, and soil. Key environmental chemical contaminants include:

  • Dioxins, which are a group of aromatic halogenated hydrocarbons produced during industrial activities and waste incineration, are persistent organic pollutants and highly toxic substances. They have been classified as human carcinogens by the Environmental Protection Agency (EPA). The most potent dioxins are TCDD and PCB, and they enter the food chain through air, water, and soil. These chemicals are environmentally stable with a half-life of 7-11 years and have been found in animal fatty tissues, dairy products, and seafood. According to a joint study by WHO and FAO, at very low concentrations, dioxins are not expected to cause significant health issues. The study recommends removing fats from meats and consuming low-fat dairy products to reduce exposure to dioxins.
  • Benzene, an aromatic hydrocarbon commonly used as a solvent and in the production of specific polymers, can be generated through the thermal breakdown of food components like β-carotene (e.g. Carrots, leafy greens, many red fruits, turmeric, etc), phenylalanine (e.g. meats, fish, dairy, eggs, nuts, seeds, legumes, etc.), terpenes ( e.g. citrus fruits, avocadoes, black pepper, etc.), and certain food additives. In natural occurrences, benzene is formed during forest fires, volcanic activities, cigarette smoking, and the combustion of fossil fuels. Benzene is classified as a Group 1 carcinogen. The presence of benzene in food and beverages is linked to cooking methods, the breakdown of food preservatives like benzoates, and drinking water, and the irradiation of food, and packaging materials.
  • Perchlorates, commonly used in rocket fuels, batteries, munitions, fertilizers, cleaning agents, and bleach, are potent oxidizing agents that are highly soluble in water. They have been detected in drinking water and soil. Leafy crops irrigated with water contaminated with perchlorate tend to accumulate higher levels of this compound. Research has shown that the presence of perchlorate in human blood can disrupt thyroid gland function by inhibiting iodine uptake and reducing the gene expression of thyroglobulin and thyroperoxidase, which are essential for thyroid hormone biosynthesis. Additionally, other naturally occurring chemicals like nitrates and thiocyanates in the food chain can also hinder iodine uptake.
  • Melamine, a white crystalline organic base derived from urea, is utilized in the production of melamine resin and is a key component of pigment yellow 150 found in inks and plastics, as well as fire-retardant materials in paints, plastics, and paper. Due to its high nitrogen content (67% by mass), melamine has been used to adulterate milk and wheat gluten. In China, melamine scraps have been mixed into fish and pet foods. This led to numerous pet deaths in the US and infant illnesses with renal and kidney issues in 2007. Melamine was also discovered in wheat gluten and rice protein concentrate exported from China and used in pet food manufacturing. Contamination was found in various brands of powdered baby formula, a frozen yogurt dessert, and canned coffee drinks. Studies have shown that when melamine combines with cyanuric acid in the bloodstream, it forms crystals that can cause kidney stones. These crystals can block and harm renal cells, leading to kidney malfunction or failure. Melamine resin-based products are commonly used for food packaging and tableware, and melamine has been detected in foods at parts per million levels. In light of these incidents, the FAO/WHO does not endorse the addition of melamine to foods and has proposed a maximum upper limit of 0.2mg/kg.
  • Radionuclides, specifically Iodine (131 I), and Caesium (134 Cs, and 137 Cs) are a significant concern as they have been found in specific regions in certain vegetables, fruits, and edible plants. It is thought that radionuclides enter the food chain through soil, air, and water. Animals that consume radioactive feed can produce milk contaminated with radioactive iodine or caesium. Elevated levels of radioactive iodine in the thyroid gland can increase the likelihood of thyroid cancer, while caesium, with a longer half-life than iodine, poses a higher cancer risk.

 

WHO/FAO has actively monitored food products entering the market and identified numerous chemicals that can enter the food chain through packaging, processing, and transportation, potentially harming human health. While low concentrations of these chemicals may not present a significant threat, WHO/FAO has established guidelines for national food safety organizations to follow to prevent chemical adulterants from endangering human life. For a comprehensive list of these chemicals, refer to WHO's documentation and Chapter 13 of my book, "Science of Food Nutrition and Health," published by Austin Macauley Publishers. Stay tuned for my next blog post, where I will delve into the Global Burden of Foodborne Diseases, a critical public health concern worldwide.

 

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