Naturally occurring toxicants Flashcards
What are added sugars?
- Naturally occurring mono- and di- saccharides that are added to food during processing or preservation
- Examples (needed to provide functional properties beyond sweetness in formulations)
- HFCS (converted from glucose in the form of maltose)
- Fructose
- Glucose
- Sucrose
- Maltose
Sugar = sucrose; sugars = everything else (including sucrose - a bit confusing!)
What are the health risks of added sugars? [3]
- Excess intake of sugars
- Increases the risk of weight gain & obesity
- over the limit of dietary caloric needs, body stores excess GLU as fat
- Increases the risk of weight gain & obesity
- Reduces intake of other nutrients
- (i.e dietary fiber, nutrients from dairy, fruits & vegetables)
- Foods with high [GLU] cause significant fluctuations in blood glucose levels
What diseases are associated with increased sugar intake? [5]
- Type II Diabetes
- High blood pressure
- Heart disease
- Stroke
- Crohn’s disease
Save for Type II diabetes, these health risks associated with sugars are not substantiated!
Comment on the ethics of the most commonly added sugar (HFCS). [3]
- Made from genetically modified corn
- Farmed using the Productionist Paradigm (i.e., ‘more production is always good’)
- Little respect for the environment
What is a sweetener?
- Naturally occurring or synthetic molecule
- Low calorie & non caloric sweeteners
- Does not increase blood [GLU] or insulin levels
When are sweeteners preferred or necessary for consumers? [3]
- With diabetes
- Concerned with high caloric intake
- Trying to reduce dental caries
Sorbitol is a low calorie sweetener.
True or False?
True.
Sorbitol is a non caloric sweetener.
True or False?
False.
Sorbitol is a low calorie sweetener.
Describe sorbitol.
- Naturally found in fruits & commercially produced
- Used in chewing gums, frozen desserts, etc. (for physical properties, not sweetness - e.g., prevents recrystallization of sugars in candies)
- 60% as sweet as glucose
- Does not contribute to dental caries
- Excessive consumption leads to laxative effects
- Low calorie
Give one PRO and one CON about sorbitol.
- PRO: Does not contribute to dental caries
- CON: Excessive consumption may lead to laxative effects.
Name three non caloric sweeteners.
- Acesulfame Potassium
- Aspartame
- Sucralose “Splenda”
Describe acesulfame potassium.
- Often used with Aspartame
- Used in soft drinks, baked goods, etc.
- 200 times sweeter than sucrose
- Does not contribute to dental caries
Non caloric sweetener
Aspartame is often used with […]
Acesulfame-potassium
Acesulfame Potassium is often used with […]
Aspartame
Describe Sucralose.
- “Splenda”
- Chlorinated molecule
- 3-OH groups of sucrose are replaced by Cl
- Used in canned fruits, fruit drinks, baking, etc.
- 600 times sweeter than sucrose
- Does not contribute to dental caries
Non-caloric sweetener
Rank in order from least to most sweet:
- Acesulfame Potassium
- Sorbitol
- Sucralose
- Sorbitol - 60% as sweet as sucrose
- Ace-K - 200x sweeter than sucrose
- Sucralose - 600x sweeter than sucrose
What should we do about added sugars in food? [3]
- Decrease consumption of foods with added sugars
- Increase consumption of foods in its raw form
- Occasionally use artificial or natural sweeteners
Did we forget another sugar alternative?
Yes - stevia (non-caloric) - similar sweetness to sucralose. Not available in Canada - sold in the US as ‘Sweet n’ Low’
What causes protein oxidation? [2]
- Protein is oxidized during frozen storage in different food matrices like beef patties, chicken meat, raw pork and different types of fish
- The usage of sodium nitrite, in cured meat, is another cause of protein oxidation
Amino acid oxidation: Lysine
Alpha-aminoadipic acid
Amino acid oxidation: Tyrosine
Dityrosine
Kynurenine
Amino acid oxidation: Tryptophan
Kynurenic acid
Alpha-aminoadipic acid
Amino acid oxidation: Lysine
Dityrosine
Kynurenine
Amino acid oxidation: Tyrosine
Kynurenic acid
Amino acid oxidation: Tryptophan
What is alpha-aminoadipic acid?
- A carbonyl product derived from the oxidation of lysine; found in processed muscle foods
- A biomarker for both assessment of food oxidation damage and potential diseases in humans.
What is dityrosine?
-
The major oxidation product of tyrosine, which accounts for 22% of total oxidized tyrosine products.
- Has a phenolic hydroxyl structure and can induce ROS production increases the level of oxidative stress and chronic inflammation
What are kynurenine and kyneuric acid?
- Oxidation products of tryptophan, found in dairy products, processed meat and also in honey, cocoa powder, and fermented foods such as beer and cheese
Describe regulations related to controlling protein oxidation.
- Currently no regulations related to controlling protein oxidation in food in Canada.
- The Canadian Food Inspection Agency (CFIA) recognizes heating and smoking as minimum processes, while oxidation by addition of chemicals is considered a maximum process that results in significant alteration of the natural character of foods (CFIA, 2019)
What are the 3 phases of lipid oxidation?
- Initiation
- Propagation
- Termination
(1) Loss of essential fatty acids; (2) rancidity; (3) oxidation products are free radicals.
What occurs in the initiation of lipid oxidation?
- Pro-oxidant lowers activation energy so molecule will oxidize to produce a radical
What occurs during propagation of lipid oxidation?
- Peroxyradical is very radical
- Attacks another lipid
How does lipid oxidation terminate?
- Lipid oxidation terminates when reactive radicals combine to form stable, non-radical products, such as when two radicals react together or when an antioxidant donates electrons to neutralize the radicals.
- This halts the chain reaction that propagates lipid oxidation.
How can lipid peroxidation products be controlled? [4]
- Photosensitizers
- Temperature
- Water activity
- Presence of antioxidants
How does control of generation of free radicals control lipid peroxidation products?
- Control of generation of free radicals (1) reduces availability of lipid oxidation catalysts and inactive oxidation intermediates and (2) mitigates generation of oxidation breakdown products.
Oxidized products of cholesterol initiate […]
- Oxidized products of cholesterol initiate atherosclerosis
Name 2 methods to measure lipid oxidation.
- Peroxide value
- Thiobarbituric acid test
What is peroxide value?
Peroxides can be measured by their (1) ability to liberate iodine from potassium iodide (iodimetry) or to (2) oxidize ferrous to ferric ions (thiocyanate method).
These are measures of primary lipid oxidation products (as compared to TBA test which measures secondary products)
What is the thiobarbituric acid test?
TBA reacts with malondialdehyde (MDA), a major breakdown product of lipid peroxides (i.e., secondary product of lipid oxidation).
What are antiminerals?
Substances that interfere with the absorption or metabolic utilization of mineral elements.
e.g., phytic acid; oxalates; goitrogens
Give 3 examples of antiminerals.
- Phytic acid - can be used as a sequestering agent for divalent metal ions (e.g., to prevent turbidity in apple juice from polyphenol interaction with minerals); however, its irreversible binding capacity could lead to deficiencies - not presently used as an additive
- Oxalates - also bind strongly to divalent metal ions to form irreversible salts
- Goitrogens - suppress the synthesis and function of the thyroid gland by interfering with iodine uptake
List some sources of antiminerals.
- Tea leaves (Camellia sinensis)
- Vegetables (spinach; lettuce; carrots; rhubarb; beets; peas)
- Nuts
What is oxalic acid?
- Strong organic acid that forms water-soluble salts with divalent minerals such as calcium and potassium.
- Deposition of calcium oxalate in the kidneys (kidney stones).
- Salts are known as oxalates; bioavailablity is reduced.
Anti-mineral
What are goitrogens?
- Substances that suppress the synthesis and function of the thyroid gland by interfering with iodine uptake.
Antiminerals
Goitrogens include: (1) glucosinolates, and (2) thiocyanates
What are trypsin inhibitors?
- Types of protease inhibitors based on the specificity of trypsin, chymotrypsin, or elastase
- The toxicological and nutritional significance depends on their activity on human proteases.
How may protease inhibitors be inactivated?
- Most antiproteases are inactivated by moist heat.
- Dry heat is less effective.
- Heating milk for at least 1h at 85°C can destroy trypsin inhibitor.
- Autoclaving soybean for 30min at 121°C is necessary for maximum destruction of inhibitors.
- Soaking in water before heat treatment.
Name some food sources of lectins. [4]
- Legumes: soybean, peanut, lima beans, kidney beans, fava beans, lentils, pea
- Grains: wheat and its germ
- Potato
- Fruits: banana, mango
What are lectins?
- An anti-protein
- Most lectins are glycoproteins of non-immunoglobulin origin.
- Capable of specific recognition of and reversible binding to carbohydrate moieties.
- Also called hemagglutinins (agglutinate red blood cells)
What is ricin?
- A non-edible toxic lectin
- Toxic if inhaled, injected, or ingested.
- A disrupter of the intestinal absorptive capacity for nutrients and other compounds
- Inhibits protein synthesis
- The most toxic of all lectins (LD50 = 0.2 mg)
- Isolated from castor bean
Eight beans are considered toxic for an adult.
Oral toxic dose in adults: 150 - 200 mg.
What is the toxic mechanism of ricin?
- Related to ability to bind to specific cell receptors.
- Binding to cells disrupts the intestinal absorptive capacity for nutrients and other compounds
What is the toxicity of a saponin associated with?
- The potential to lower surface tension
- Have a soap-like quality; dissolve in water to form a stable soapy froth
- Targets cell membranes
What are the two main groups of saponins?
- Steroid (27 carbon atom steroids)
- Triterpenoid (30 carbon atom triterpenes)
Describe the pharmacology of methylxanthines (plant alkaloids).
- Wide range of T1/2 is due to individual variation and variety of physiological and environmental factors that involve metabolism.
- Tolerance with continued use develops; does not have the profile of addictive ‘drug’
- Rapidly absorbed (99% after 1hr ingestion)
- Distributed into body water pool so access to all tissues.
- Undergoes hepatic 1st-pass metabolism
- Readily re-absorbed by renal tubules
- General effects include:
- Mild CNH stimulation, wakefulness, cardiovascular and renal systems;
- Side effects: restlessness, tachycardia, nervousness
Plasma peak concentration caffeine (75 minutes) vs. paraxanthine (300 minutes)
What is the principle metabolite excreted after consuming a methylxanthine?
- Paraxanthine (1,7 dmx) is the principle (70-80%) metabolite excreted
What is a pressor amine?
(vaso)pressor
- Biogenic amines- (tyramine, histamine, dopamine) cause an increase in blood pressure on exposure
- Vasoactive amines- in banana peel, potato, spinach, grape, and tomatoes: (serotonin, norepinephrine, tyramine);
- Generated by microbial, vegetable, and animal metabolism
Trytophane decarboxylated to tryptamine causes headaches after eating chocolate in some people.
How do biogenic amines form? [4]
- Decarboxylation (most common)
- Reductive amination
- Transamination
- Hydrolysis
What is histamine?
- Contained in mast cells and basophils - part of the immune response
- Receptors on the membrane of respiratory, cardiovascular, gastrointestinal, and heamatological/immunological systems and the skin
Biogenic amine
Receptor: H1, H2, H3
Describe histamine in food.
- Histamine is an useful indicator of decomposition in scombroid
- Found in scombroid fish tissue as free histidine
- Found highly in tuna fish with inadequate food processing
- Low storage temperature is required for storing fish to reduce the level of histamine from histidine production:
- Hazardous bacterial histamine production can form rapidly at high temperature
What are the symptoms of histamine poisoning?
- Dilation of peripheral blood vessels capillaries and arteries = hypotension, flushing, headache;
- Contraction of intestinal smooth muscle (H1) = abdominal cramps, diarrhea, vomiting;
- Regulation of gastric acid secretion (H2) = secretion of gastric acid;
- Sensory and motor neuron stimulation (H1) = pain, itching associated urticarial lesion
Describe melamine.
- Melamine contains nitrogen (but is not an amino acid); protein is assessed by nitrogen content
- Melamine intoxification = nephrotoxicity
- Acute kidney injury (necrosis of distal tubular cells; mild inflammation)
- Chronic kidney disease (large cyrstals; interstitial inflammation; fibrosis)
Describe the results of the assessment of melamine and cyanuric acid toxicity in cats, fish, and pigs.
- Touch impressions of the cats kidneys found they developed the presence of fan-shaped birefringent crystals
- No dose-dependent effects either clinically or
clincopathologically - Similar results and effects observed in fish and hogs
Similar structure so competes with adenosine which is involved in homeostatic control.
- Caffeine
Sulfur metabolites of caffeine are too large for renal reabsorption and are excreted.
Similar structure so competes with adenosine which is involved in homeostatic control.
Theophylline
Similar structure so competes with adenosine which is involved in homeostatic control.
Theobromine
Where are oxidation products of tryptophan found? [5]
- Dairy products
- Processed meat
- Honey
- Cocoa powder
- Fermented foods (e.g., beer and cheese)
