Lecture 8 - Foodborne Hazards and Human Health
When we eat something and we get stomach pain and cramps, we usually say, “It must be
something I ate”.
There are two major forms of foodborne illnesses. First one is transmissible diseases
caused by bacteria, viruses, and parasites (like worms, etc.). The other group are called
nontransmissible diseases (something that cannot be transmitted from person to person).
Some of these diseases that will be discussed in this lecture are: Shellfish-associated
toxins (something that can cause poisoning), Colour additives, Bioengineered foods,
Obesity, Diabetes. These are some of the major ones, but not all are listed here.
Cardiovascular diseases can also be associated with food.
Transmissible Foodborne illnesses
Types of food
We are all aware that in Canada, we have one of the safest food supplies in the world.
However, every year significant number of people get sick as a result of the contaminated
food. Some examples of food that could turn out to be the reason of poisoning include:
Meat (number one cause), milk, dairy products (cheese, in summer ice cream can be very
risky from some sources), unpasteurised fruit and vegetable juices (pasteurised fruits and
food material is not that bad for hour health, as most the bacteria and contaminants are
killed during pasteurization. But, unpasteurized material can be very toxic if they are
contaminated) , raw or undercooked eggs, chicken, tuna, potato and macaroni salads,
cream filled pastries, fresh produce (like some vegetables, spinach can cause food
poisoning or salmonellosis), spices, chocolate (has milk in it), seafood. It is not only up
to the type of the food, it is also up to how we handle and process the food. For example,
food standing too long in the room temperature (maybe it needs to be in the refrigerator
right away), improper cooking, contaminated cutting boards and kitchen tools.
Symptoms of Foodborne illness
All of these symptoms are related with your stomach. These include diarrhoea, abdominal
cramping, fever, vomiting, headache, sometimes blood in the stool. It could also be that
you could have all of these symptoms together. Usually these symptoms occur after one
or two hours of consuming the contaminated food. However, sometimes when viruses or
parasites are the cause of the contamination, then it can happen after a couple of days or
couple of weeks, but not right away. If bacteria are the cause, these symptoms will start
very quickly after you eat the contaminated food. Your symptoms will not last for very
long, usually no longer then a week. In more severe cases, the duration can be longer for
7 – 10 days. In summary, the symptoms usually last only a day or two sometimes 7- 10
days. For most people, these diseases are not life threatening if the person does not face
the complications. They can be very severe for young children as they can de-hydrate
very quickly, they cannot drink as they vomit all the time, and they need to see a doctor
and get hydrated a different way. They also can be dangerous for old people as they
already have weak immunity. Also they can be dangerous for people with certain diseases and conditions such as liver disease, iron disorder (people with lower iron in blood can
cause problems if it lasts for a long time), diabetes, and cancer.
Prevention of Foodborne illnesses
The best way is not to wait until we get sick, but to prevent them from happening. This
prevention starts the moment you enter supermarket, the moment we choose our food,
and we need to have a right choice. Prevention of foodborne illness starts with your trip
to the supermarket.
In the supermarket:
• Pick up your packaged and canned foods first.
• Don't buy food in cans that are bulging or dented or in jars that are cracked
or have loose or bulging lids.
• Check the expiration date
• If you have weak immune system (if you have higher risk to get
complications), avoid seafood.
• Choose eggs that are refrigerated in the store. Open the case and see if there
is any cracked egg, and if yes, do not buy it.
• Select frozen foods and perishables such as meat, poultry or fish last. This is
because some people have to travel long distance to get back home to properly store
meat, poultry or fish, and by that time, maybe such foods can melt by that time.
Always put these products in separate plastic bags so that drippings don't
contaminate other foods in your shopping cart.
When you get home, you have to properly store your food. You have to keep certain
foods in refrigerator and some food some food to be frozen. Meats can last about 2 – 3
days in a fridge, but after that it has to be frozen. Basically keep food in safe place. Then
comes safe food preparation. The biggest source of contamination of food can be cutting
boards or kitchen table where you usually cut your food. Never cut meat (first processing
meat) on a cutting board, and then use the same board for cutting vegetables without
washing the cutting board. A good solution to wash the cutting board is bleach. Basically,
5 millilitres of bleach for one hour in water. This is a very good solution to disinfect
kitchen board or cutting board where you process meat. After that all you need to do is
just wash it with that solution. The sink can be disinfected with that solution. You can
also run that solution through the drains, to disinfect the drains. To sum this all up, you
need to keep everything clean. You must wash hour hands before you touch food or
anything food related. Keep hot food hot and cold food cold. If you cook something and if
that food is hot, that food should not stay longer than 2 hours in room temperature. Cold
food should always stay in fridge or refrigerator, not in the room temperature. You must
cook food properly, as raw food can cause food borne illnesses. This is because inside
raw meat you do not kill bacteria, as it is uncooked process. You must properly store
leftovers. After the lunch or dinner, leftovers must be closely packed and placed in the
fridge. It is supposed to be consumed in the next three days. The photographs in the
lecture slide show that brushes or sponges or cloths used in the kitchen can be source of
contamination as well. We should always disinfect them with bleach or some other
commercial disinfectant, or simply buy new ones. Bacteria: Escherichia coli
It can cause contamination in water. Food poisoning usually associated with eating
unwashed vegetables and meat contaminated post-slaughter (contaminated in kitchen
boards, after you buy the meat). The biggest source of contamination is grounded beef.
Common symptoms include diarrhoea, vomiting, abdominal (stomach) cramps. Basically,
these are common symptoms for any food borne disease. Some people face complications
such as Hemolytic Uremic Syndrome, which is very serious problem. Here, the red
blood cells are destroyed. This means that the immune system is destroyed as the red
blood cells are part of our immune system. As a result of that, kidneys fail. It will lead to
death if we are not treated medically. Around 2 – 7% of all cases will have these
Another type of bacteria that can cause food borne disease is Salmonellosis. The name is
the bacterium is Salmonella, and Salmonellosis is the illness. It is very similar to
Escherichia coli, as the symptoms are very similar. Only medical doctors can realize what
is really happening, by analyzing the stool and detecting what kind of bacteria caused this
illness. The characteristic for salmonellosis is that is closely associated with animals.
That is, it is related to feces of certain types of animals. When food comes in contact with
animal feces, it might result in salmonellosis. Animals like different types of reptiles. In
this case, small turtles are common source of the illness. Prof. suggests washing hands
after playing with any reptiles or any animal. Often we get warnings to not to eat certain
types of spinach or some other leafy vegetable. However, spinach is more common as it
gets contaminated somewhere between growing and our kitchen table. There are many
warnings about spinach from US. There is usually no need for treatment. It will last two
to three days with its symptoms, and then it will be finished. No medication is necessary.
Botulism is very serious and fatal food borne illness. However, it is rare and not seen
often. In US, every year there are only five or ten cases. It is caused by nerve toxin
produced by bacterium called Clostridium botulinum. This bacterium does not cause
illness by itself, only toxin causes the problem. Problem caused by the toxin made by C.
botulinum, not by the bacterium itself. Always, these toxins are associated with home-
canned foods. Home-canned foods are usually the source of this toxin, not commercially
canned food. Commercially canned food has to go through certain process that is called
“botulinum cook". Each can is cooked at 121 °C (250 °F) for 3 minutes. This means that
Clostridium botulinum bacteria and their spores will be killed. Usually home-canned food
is maybe not pasteurized long enough or maybe it’s not treated under appropriate
temperature. Therefore, it could be (not always) the source of botulism. Some unusual
sources that are listen in the literature. 1) Garlic or herbs stored covered in oil. 2)
Improperly handled baked potatoes wrapped in aluminium foil. 3) Home-canned or
fermented fish (in Canadian north people store the fish and use some kind of fermentation
to preserve for later use). Main kinds of botulism
There are three major kinds of botulism. 1. Food borne botulism, 2. Wound botulism,
3. Infant botulism. Food borne botulism is consumed the food already contaminated with
toxin, produced by Clostridium botulinum. Wound botulism is contamination of wound
by the bacteria, it has similar symptoms but entrance is different. Infant botulism is very
rare, but it is still around us. Here, kids can consume spores of Clostridium botulinum,
not the toxin, and then in their body that bacteria can produce toxins. The spores of these
bacterium are often found in soil, and consuming (accidentally) some dirt or sand, kids
can intake some spores.
Symptoms of Food borne botulism
Symptoms occur between 12–36 hours after consuming the botulinum toxin, which is
very quick. It has very serious symptoms. There is double and/or blurred vision (chan