Biological Adaptations to Dietary Toxins

Class 3

The omnivore’s dilemma

Have a lot of options, increased risk of exposure to toxins; have to evaluate diverse foods between nutritions or dangerous

Urtication

irritation from stinging plant hairs

Ex: Utica dioica: called stoning medal and can sting hand ; edible but has to be processed

Trigeminal Nerve

Detects pain, touch, and temperature

Sensitive to chemical irritants (capsaicin, pipeline)

Works with taste and smell

Taste Signals and Meaning

Sweet = energy rich

Bitter = possible toxins or medicines

Genetic Response

innate avoidance behavior

Learned Responses

Conditioned taste aversion

Speed of Detection

Rates: detect taste quality in 0.1 seconds (very fast)

Humans: detect in 0.4-2.2 seconds (we integrate memories into food)

Phenylthiocarbamate (PTC) taste genetics

PTC tasting varies among humans (genetics)

Linked to glucosinlate detection (Brassicaceae)

Goitrogenic compounds disrupt thyroid function

Taste Test and Genetics

70% of people taste PTC as bitter

Neophobia

Fear / Caution with new foods

Children: reduced in kids post weaning → makes them at higher risk for poison bc they will eat anything

Adults: limited experimentation, don’t try new foods

Conditioned Taste Aversions

Stronger taste or illness = stronger aversion

Nausea

Key defense mechanisms

Links illness with specific foods

Food aversion easier to learn then preferences

Physiological effects of encountering plant chemicals

Disrupts DNA / protein synthesis

Alter membrane transport

Inhibit or activate enzymes

Block neurotransmitter receptors

DetoxICation

Enzymatic defense against toxins\

Your BODY removes a toxin

Key enzymes: Cytochrome P450, gluthione, superoxide dismutase

DetoxIFIcation

Treatment of poisoning

Gut Microbiome’s role

Gut bacteria transform toxins before absorption

Hydrolyze glycosides to release active aglycones

Diet affects microbiome activity → alters detoxication

Cyanogenic Glycosides

Found in cassava, bitter almonds, apple/ apricot seeds

Release hydrogen cyanide (HCN) when hydrolyzed

Acute exposure = cellular asphyxiation

Chronic exposure = thyroid disruption

Detoxication via rhodanese → thiocyanateG

Glucosinaltes

Found in Brassicaceae (Broccoli, cabbage, mustard, horseradish)

Hydrolyzed to isothiocyanates, thiocyanates, nitriles

Low levels = pungent flavor ; high =unpalatable

Chronic metabolites linked to goiter (enlarged thyroid)

Alkaloids

Diverse, nitrogen-containing compounds (nicotine, quinine, morphine)

Bitter or trigeminal irritants (capsaicin, pipeline)

many are CNS active, some theraputic, other toxic

Detoxication pathways vary widely

Saponins and Glycoalkaloids

Glycosides of steroidal / triterpenoid compounds

Bitter, foaming in water ; hemolyze red blood cells

Found in quinoa, potates, yams, lentils

Poorly absorbed in gut → GI distress but rarely fatal orally

Potato glycalkaloids can accumulate and cause poisioning

Tannins and Flavonoids

Tannins: bind proteins, reduce digestibility, cause astringency

Flavonoids: widespread, often antioxidant and medicinal

Proline-rich proteins in saliva bind tannins, reducing effects

Balance between deterrent effects and health beeneftis

Geophagy

Purposely eating: Clay / soil binds toxins prevents absorption

Taste Modiferers and Co evolution

Miracle fruit: miraculin makes sour taste sweet

Thaumatin and monellin: intensely sweet proteins from African fruits

Plant benefits from seed dispersal; human exploit as novelty and food aid

PTC tasting ability is evenly distributed across all human populations

False

PTC tasting ability is linked to sensitivity to which plant compound group

Glucosinlates

Goitrogens interfere with the function of the _____ gland

thyroid

Sensory specific satiety helps

prevent overconsumption of any one toxin

Geophagy refers to

eating soil or clay

Match each detoxification related rem to its description

Detoxication

Gluthione

Cytochrome P450

Detoxification

Detoxication: enzymatic metabolism of toxins

Glutathione: Antioxidant molecule that neutralizes free radicals

Cytochrome P450: Enzyme system in the liver that oxidizes toxins

Detoxification: treatment for poisoning

Miracle fruits alter taste perceptions by modifying sour flavors into sweet

true

Industrial diets may reduce exposure to beneficial bitter compounds

True

Which compound gives grapefruit peel its extreme bitterness

Naringin

Coffee bitterness come from cucurbitacins

False