Naturally occurring toxicants Flashcards
(103 cards)
1
Q
What are added sugars?
A
- 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!)
2
Q
What are the health risks of added sugars? [3]
A
- 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
3
Q
What diseases are associated with increased sugar intake? [5]
A
- 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!
4
Q
Comment on the ethics of the most commonly added sugar (HFCS). [3]
A
- Made from genetically modified corn
- Farmed using the Productionist Paradigm (i.e., ‘more production is always good’)
- Little respect for the environment
5
Q
What is a sweetener?
A
- Naturally occurring or synthetic molecule
- Low calorie & non caloric sweeteners
- Does not increase blood [GLU] or insulin levels
6
Q
When are sweeteners preferred or necessary for consumers? [3]
A
- With diabetes
- Concerned with high caloric intake
- Trying to reduce dental caries
7
Q
Sorbitol is a low calorie sweetener.
True or False?
A
True.
8
Q
Sorbitol is a non caloric sweetener.
True or False?
A
False.
Sorbitol is a low calorie sweetener.
9
Q
Describe sorbitol.
A
- 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
10
Q
Give one PRO and one CON about sorbitol.
A
- PRO: Does not contribute to dental caries
- CON: Excessive consumption may lead to laxative effects.
11
Q
Name three non caloric sweeteners.
A
- Acesulfame Potassium
- Aspartame
- Sucralose “Splenda”
12
Q
Describe acesulfame potassium.
A
- 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
13
Q
Aspartame is often used with […]
A
Acesulfame-potassium
14
Q
Acesulfame Potassium is often used with […]
A
Aspartame
15
Q
Describe Sucralose.
A
- “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
16
Q
Rank in order from least to most sweet:
- Acesulfame Potassium
- Sorbitol
- Sucralose
A
- Sorbitol - 60% as sweet as sucrose
- Ace-K - 200x sweeter than sucrose
- Sucralose - 600x sweeter than sucrose
17
Q
What should we do about added sugars in food? [3]
A
- 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’
18
Q
What causes protein oxidation? [2]
A
- 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
19
Q
Amino acid oxidation: Lysine
A
Alpha-aminoadipic acid
20
Q
Amino acid oxidation: Tyrosine
A
Dityrosine
Kynurenine
21
Q
Amino acid oxidation: Tryptophan
A
Kynurenic acid
22
Q
Alpha-aminoadipic acid
A
Amino acid oxidation: Lysine
23
Q
Dityrosine
Kynurenine
A
Amino acid oxidation: Tyrosine
24
Q
Kynurenic acid
A
Amino acid oxidation: Tryptophan
25
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*.
26
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*
27
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
28
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)
29
What are the 3 phases of lipid oxidation?
* Initiation
* Propagation
* Termination
## Footnote
(1) Loss of essential fatty acids; (2) rancidity; (3) oxidation products are free radicals.
30
What occurs in the initiation of lipid oxidation?
* Pro-oxidant lowers activation energy so molecule will oxidize to produce a radical
31
What occurs during propagation of lipid oxidation?
* Peroxyradical is very radical
* Attacks another lipid
32
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.
33
How can lipid peroxidation products be controlled? [4]
1. Photosensitizers
2. Temperature
3. Water activity
4. Presence of antioxidants
34
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.
35
Oxidized products of cholesterol initiate [...]
* Oxidized products of cholesterol initiate **atherosclerosis**
36
Name 2 methods to measure lipid oxidation.
* Peroxide value
* Thiobarbituric acid test
37
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**).
## Footnote
These are measures of primary lipid oxidation products (as compared to TBA test which measures secondary products)
38
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).
39
What are antiminerals?
Substances that interfere with the absorption or metabolic utilization of mineral elements.
## Footnote
e.g., phytic acid; oxalates; goitrogens
40
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
41
List some sources of antiminerals.
* Tea leaves (*Camellia sinensis*)
* Vegetables (spinach; lettuce; carrots; rhubarb; beets; peas)
* Nuts
42
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.
## Footnote
Anti-mineral
43
What are goitrogens?
* Substances that suppress the synthesis and function of the thyroid gland by interfering with iodine uptake.
| Antiminerals
## Footnote
Goitrogens include: (1) glucosinolates, and (2) thiocyanates
44
Give examples of where to find goitrogens.
* Phenolic glucosides: *Brassica* species: broccoli, brussel sprouts, cabbage, cauliflower, mustard, radish, rutabaga, rapeseed, turnip.
* Legumes: soybean, peanuts.
* Milk if cows were fed with goitrogenic pasture.
## Footnote
Susceptible to heat and freezing - very unstable.
45
Describe the toxicity of goitrogens.
* **Actions**: Interference in iodine uptake by direct action on the thyroid gland; Prevention or interference in thyroxine synthesis.
* Lowers thyroxine content of the thyroid gland.
* Block in the intestinal absorption of iodine or the re-absorption of thyroxine.
## Footnote
Cooking and freezing reduce the amount of goitrogens in milk and vegetables.
46
What are cyanogenic glycosides?
Compounds that yield hydrogen cyaninde (HCN) - upon treatment with acid or appropriate hydrolytic enzymes.
HCN is a potent respiratory inhibitor - inhibits cytochrome oxidase.
## Footnote
1000 different species of plants are cyanophoric (e.g., seeds in lemon lime, apple plum, bamboo shoot, seeds of bitter almond)
47
Why is hydrogen cyanide dangerous?
* It is a potent respiratory inhibitor
* Site of inhibition is enzyme cytochrome oxidase (terminal respiratory catalyst of aerobic cyanohydrin)
48
What are anti-proteins?
* Protease inhibitors
* Substances (some are proteins) that interfere with the digestion, absorption, or utilization of amino acids and proteins
* In doing so - they reduce protein quality
## Footnote
Examples include: Specific Protease Inhibitors: Inhibit function of peptidases (proteolytic enzymes) by binding to the enzyme’s active site (i.e., act as competitors)
49
Give examples of anti-proteins. [4]
* Lectins
* Digestive protease inhibitors (e.g., trypsin inhibitors)
* Saponins
* Polyphenols: tannins
50
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.
51
Name food sources of trypsin inhibitors. [5]
* Ovomucoid (egg white) and ovoinhibitor
* Bovine colostrum and milk,
* Lima beans, soybeans, kidney beans
* Bovine and porcine pancrease
* White and sweet potatoes.
52
Name some food sources of chymotrypsin inhibitors. [5]
* Egg white
* Soybean
* Lima beans
* Lettuce
* White and sweet potatoes
53
Name some food sources of elastase inhibitors. [3]
* White and sweet potatoes
* Kidney beans
* Soybeans
54
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.
55
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
56
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)
57
Edible lectins from [...] are the most toxic.
Edible lectins from **kidney beans** and **hyacinth beans** are the most toxic.
58
Some effects of lectins obtained from animal studies are: [6]
* Growth retardation
* Low nitrogen retention
* Excessive stimulation of secretory exocrine pancrease cells
* Excretion of proteins in the feces due to the inability to digest them
* Liver necrosis
* Death
59
Ricin is inactivated by moist heat.
True or False?
False.
Risin is a lectin from castor beans and it is not inactivated by moist heat.
60
Ricin is not inactivated by moist heat.
True or False?
True.
61
Most lectins are inactivated by moist heat.
True or False?
True.
Not ricin.
62
Most lectins are inactivated by dry heat.
True or False?
False.
Dry heat is largely ineffective; most lectins are inactivated by moist heat (not ricin).
63
What decreases the hemagglutinatin activity of lectin in some varieties of beans and peas?
Germination
64
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.
## Footnote
Oral toxic dose in adults: 150 - 200 mg.
65
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
66
What are saponins?
* Glycosides that occur in a wide variety of plants
* 27 carbon atom steroids or 30 carbon atom triterpenes
| Anti-protein
## Footnote
e.g., spinach; beetroot; asparagus; ginseng
67
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
68
What are the two main groups of saponins?
* Steroid (27 carbon atom steroids)
* Triterpenoid (30 carbon atom triterpenes)
69
What are psychoactive substances?
* Occur naturally and exert effect on the central nervous system
70
List the three general categories of psychoactive substances and give examples of each.
* **Trimethylxanthines and alkaloids** (e.g., caffeine; nicotine)
* **Myristicin** - a weak monamine oxidase inhibitor (inhibitor of phase I detoxification) (e.g., nutmeg; mace)
* **Safrole, eugenol** - belong to the Umbelliferae family of crops (e.g., carrot; parsley; celery; dill)
71
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
## Footnote
Plasma peak concentration caffeine (75 minutes) vs. paraxanthine (300 minutes)
72
What is the principle metabolite excreted after consuming a methylxanthine?
* Paraxanthine (1,7 dmx) is the principle (70-80%) metabolite excreted
73
What is a pressor amine?
## Footnote
(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
## Footnote
Trytophane decarboxylated to tryptamine causes headaches after eating chocolate in some people.
74
What will the pressor amine L-DOPA cause?
| Precursor to dopamine
* Nausea, vomiting, and involuntary chewing movements
## Footnote
Many tissues contain the mitochondrial enzymes (monoamine oxidases) that can catalyze the oxidative deamination of most vasoactive amines.
75
How do biogenic amines form? [4]
* Decarboxylation (most common)
* Reductive amination
* Transamination
* Hydrolysis
76
What are the common conditions that affect the formation of biogenic amines? [5]
* Availability of free amino acids
* Presence of decarboxylase-positive microorganisms
* Conditions that allow bacterial growth, decarboxylase synthesis and decarboxylase activity:
* Acidic Environments (pH 4.0 - 5.5)
* Temperature (Between 20° C - 37° C)
* Presence of salts (Variable effect)
77
What conditions allow bacterial growth, decarboxylase synthesis and decarboxylase activity? [3]
| i.e., formation of biogenic amines
* Acidic Environments (pH 4.0 - 5.5)
* Temperature (Between 20° C - 37° C)
* Presence of salts (Variable effect)
78
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
## Footnote
Receptor: H1, H2, H3
79
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**
80
What are the symptoms of histamine poisoning?
1. **Dilation** of peripheral blood vessels capillaries and arteries = hypotension, flushing, headache;
2. **Contraction** of intestinal smooth muscle (**H1**) = abdominal cramps, diarrhea, vomiting;
3. Regulation of gastric acid secretion (**H2**) = secretion of gastric acid;
4. **Sensory** and **motor** neuron stimulation (**H1**) = pain, itching associated urticarial lesion
81
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)
82
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
83
What is the CFIA set standard for melamine based on dose-response data?
* Melamine LD50 = 3100 mg/kg in rats
* TD50 = 735 mg/kg body wt. per day (carcinogenic potency)
* Lowest identified dose for general toxic effect <63 mg/kg body wt per day
* CFIA set standard for toxicological reference dose = **0.35 mg/kg body wt per day**
84
List the naturally occurring toxicants. [5]
1. Added sugars
2. Anti-nutrients (e.g., lectin)
3. Saponins
4. Psycho-bioactive substances (e.g., trimethylxanthines like coffee)
5. Adulterants (e.g., melamine)
85
Discuss the safety of aspartame.
* An issue with those with phenylketonuria (PKU) because they cannot metabolise phenylalanine
* Aspartame is composed of two amino acids, aspartic acid and phenylalanine
* Generally safe at levels used in foods.
86
## Footnote
Similar structure so competes with adenosine which is involved in homeostatic control.
* Caffeine
## Footnote
Sulfur metabolites of caffeine are too large for renal reabsorption and are excreted.
87
## Footnote
Similar structure so competes with adenosine which is involved in homeostatic control.
Theophylline
88
## Footnote
Similar structure so competes with adenosine which is involved in homeostatic control.
Theobromine
89
What is responsible for the effects of methylxanthines?
They have similar structure to adenosine (which is involved in homeostatic control), and so compete for binding sites.
Competitively binds to adenosine receptors resulting in indirect release of norepinephrine, dopamine, serotonin, GABA.
Some people metabolize them faster than others.
90
Name 3 biogenic amines.
Tyramine
Histamine
Dopamine
## Footnote
Histamine usually lowers blood pressure through vasodilation.
The other pressor amines mentioned, like tyramine and dopamine, raise blood pressure by promoting vasoconstriction or increasing norepinephrine levels.
91
Name 3 biogenic amines.
Tyramine
Histamine
Dopamine
Cause an increase in blood pressure.
92
Name 3 vasoactive amines.
Serotonin
Norepinephrine
Tyramine
In banana peel, spinach, potatoes, grape, and tomato.
93
What can reduce the amount of goitrogens present in milk and vegetables? [2]
* Cooking
* Freezing
94
What is used as a biomarker for both assessment of food oxidation damage and potential diseases in humans?
Alpha-amino adipic acid
| Found in processed muscle foods.
## Footnote
A **carbonyl product derived from the oxidation of lysine**.
95
What is alpha-amino adipic acid used for? [2]
* Biomarker for (1) assessment of food oxidation damage and (2) potential diseases in humans.
| Found in processed muscle foods.
## Footnote
A **carbonyl product derived from the oxidation of lysine**.
96
Has a phenolic hydroxyl structure and can induce ROS production increases the level of oxidative stress and chronic inflammation
**Dityrosine - the major oxidation product of tyrosine**, which accounts for 22% of total oxidized tyrosine products.
97
What accounts for 22% of total oxidized tyrosine products?
Dityrosine
## Footnote
Has a phenolic hydroxyl structure and can induce ROS production; increases the level of oxidative stress and chronic inflammation
98
What does dityrosine cause?
* Has a phenolic hydroxyl structure that can induce ROS production
* Increases the level of oxidative stress and chronic inflammation
## Footnote
Accounts for 22% of oxidized tyrosine products
99
Where are oxidation products of tryptophan found? [5]
* Dairy products
* Processed meat
* Honey
* Cocoa powder
* Fermented foods (e.g., beer and cheese)
100
Goitrogens are very susceptible to heat and freezing.
True or False?
True
101
Goitrogens are not susceptible to heat and freezing.
True or False?
False.
Goitrogens are very susceptible to heat and freezing.
102
Goitrogens include: [2]
(1) glucosinolates
(2) thiocyanates
103
How are pressor amines deactivated and excreted?
Many tissues contain the mitochondrial enzymes (monoamine oxidases) that can catalyze the oxidative deamination of most vasoactive amines.
## Footnote
Oxidative deamination inactivates vasoactive amines, helping to regulate their levels and maintain physiological balance.
