Natural toxins are chemicals that are naturally produced by living organisms. These toxins are not harmful to the organisms themselves but they may be toxic to other creatures, including humans, when eaten.
Some plants have the capacity to naturally produce compounds that are toxic to humans when consumed. For example, under certain conditions, microscopic algae (tiny plants) in the ocean can produce compounds that are toxic to humans but not to shellfish that eat this algae. When people eat shellfish that contain these toxins, illness can quickly follow. There is an active monitoring program in place to ensure that shellfish sold to Canadians do not contain these "shellfish toxins". This monitoring program is jointly administered by the Department of Fisheries and Oceans, the Canadian Food Inspection Agency, and Environment Canada.
Mycotoxins are another group of natural toxins. The word mycotoxin is derived from the Greek word for fungus 'mykes' and the Latin word 'toxicum' meaning poison. Mycotoxins are toxic chemical products formed by fungi that can grow on crops in the field or after harvest. The foods that can be affected include cereals, nuts, fruit and dried fruit, coffee, cocoa, spices, oilseeds and milk. There are now more than 300 known mycotoxins of widely different chemical structures and differing modes of action - some target the kidney, liver, or immune system and some are carcinogenic. Common mycotoxins include aflatoxins, ochratoxin A, ergot alkaloids, fumonisins, patulin, trichothecenes (such as deoxynivalenol which is also known as vomitoxin) and zearalenone.
Health Canada monitors the food supply for mycotoxins and other natural toxins. Health Canada scientists research and evaluate the toxicity of natural toxins to humans and assess the risk of adverse health effects from exposure to natural toxins; also, they participate in international assessments of natural toxins. These activities support the development of appropriate risk management strategies to reduce exposure to mycotoxins. For example, scientists provide direction to stakeholders on how to reduce toxin levels in foods while providing advice and guidance to Canadians on the risks and benefits of particular food choices.
In order to reduce the risk of exposure to natural toxins in retail food, Health Canada develops maximum levels for these compounds in foods. For example, there is a maximum level of 15 parts per billion total aflatoxin in the edible portion of nuts and nut products. There are also maximum levels for domoic acid and paralytic shellfish toxins (both shellfish toxins); and glycoalkaloids (a plant toxin) in potatoes.
Health Canada as well as other federal government partners including the Canadian Food Inspection Agency, Department of Fisheries and Oceans, and the Canadian Grain Commission undertake regular monitoring of the levels of various natural toxins in foods. These surveillance efforts enable the current exposure of Canadians to natural toxins in foods to be determined, which in turn allows for the risks to human health to be estimated and strategies to manage any associated risks to be developed. The Canadian Food Inspection Agency also monitors to ensure compliance with any maximum levels.
Health Canada recommends that Canadians consume a variety of foods from each food group included in Eating Well with Canada's Food Guide. Health Canada has issued advice for specific foods that may contain natural toxins and these may be viewed through the links provided below and in the Topics Box above. With respect to mycotoxins which can be produced by fungi or moulds, avoid eating mouldy nuts or other mouldy foods. Mycotoxins may be present in those foods, and furthermore, the conditions that allow the growth of mould could also allow the growth of harmful bacteria that cause food-poisoning. However, there are moulds that are essential to the preparation of certain foods, such as certain varieties of cheese. The moulds in or on these cheeses (for example, Blue cheese, Stilton, Brie) are not harmful.
Fish and Shellfish