Textbook Notes (367,985)
Canada (161,540)
HNSC 1200 (46)
Snehil Dua (46)
Chapter 4

HNSC 1200 Chapter 4: Topic 4.4

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Human Nutritional Sciences
HNSC 1200
Snehil Dua

o|82 The CFIA regularly tests domestic and imported commercial fish and shellfish, both freshwater and marine, in order to enforce the mercury guideline of 0.5-1.0 parts per million (ppm) for total mercury in domestically produced and imported fish. The recommendation is to consume a variety of fish, as this minimizes your exposure to any particular toxin that may accumulate in a particular fish species. Health Canada recommends consumers limit their consumption of shark, swordfish, fresh or frozen tuna, orange roughy, escolar and marlin to a maximum of no more than 150g per week (excluding canned light tuna). For children, pregnant women and women of childbearing age, consumption of these fish is more restricted. The reason these fish are limited for children, is that children are at a stage of rapid development with metabolic rates higher than that of an adult, resulting in a greater ability to absorb substances (e.g., their level of gastro-intestinal absorption and retention is greater). In addition, the immature or developing organs and systems of children are less able to get rid of mercury. There is also less ability to repair the damage caused by mercury due to their cellular repair mechanisms not being fully developed. Methyl mercury ingested by a pregnant woman can be passed from the maternal blood to the developing fetus by crossing the placental barrier. It can accumulate in the unborn baby's blood at concentrations higher than the concentration in the mother. Mercury can also be transferred through breast milk to a nursing infant. With chronic maternal fish consumption, infants may appear normal during the first few months of life but later display IQ deficits, abnormal muscle tone, reduced motor function, and lower attention and visuospatial performance. In recent human studies, neuropsychological deficits are detected in children aged seven years following prenatal exposure to methyl mercury. Increased blood pressure in children exposed prenatally to methyl mercury has also been reported. Halogens and Organic Halogens • Chlorine o|82 Iodine Vinyl chloride Ethylene dichloride Trichloroethylene Dioxins Polybrominated biphenyl (PBB) Polychlorinated biphenyls (PCB's) PCB's refer to a group of at least 50 widely used compounds containing chlorine that can accumulate in the food chain and cause a variety of harmful effects (fatigue, eye irritation, growth retardation in children when exposed prenatally). They are man-made and were banned in North American in 1977. They can still be found remaining in the environment, because they do not break down and are difficult to destroy. So we are still exposed to small amounts of PCB's, typically through food consumption. The levels we are exposed to however are well below what Health Canada determines could cause adverse health effects. See page 25 (527) of your textbook for suggestions on how to minimize your risk of PCBs Food Additives Learning Objectives • Define toxin and discuss examples of natural toxins; Course Notes Food Additives: substances added to food either intentionally or by accident that become part of the food and affect its characteristics (like colour or flavour). Most food additives are done purposely (intentional additives), including sugar, colourings, salt, baking soda, etc. Some additives however are contaminants that are accidently introduced (indirect / incidental additives). These substances can be accidently introduced to the food during the production, processing or packaging process. Food additives have been used for OS82 thousands of y
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