Antioxidants Flashcards
Antioxidants definition
substances in foods that function in the body to protect against damage caused by free radicals
how are free radicals generated
through:
- normal physiological processes: when oxygen gains extra electron from the ETC
- exposure to toxic substances: air pollution and cigarette smoke
antioxidant rich diet
decreases risk of many chronic diseases (CVD and cancer)
what are free radicals?
- molecules with one or more unpaired electron, makes the molecule unstable and highly reactive
- attack vulnerable compounds in the body, stealing an electron in order to regain stability
- second molecule now has an unpaired electron (becomes a free radical)….sets up chain reaction
damage by free radicals
free radicals cause extensive damage within the body
- widespread damage to PUFAs in lipoproteins
- cell membranes, cell proteins and DNA/RNA
- damage linked to: cell damage, diseases (CVD and cancer, and aging
oxidative stress definition
condition in which the production of oxidants and free radicals exceeds the body’s ability to defend itself
damage by free radicals = oxidative stress
oxidative stress can lead to…
aging and development of several chronic diseases
free radicals: first line of defense
system of enzymes that:
- limit free radical formation
- disarm the most harmful oxidants
- these systems depend on the minerals selenium, copper, manganese, iron, zinc
Free radicals: second line of defense
dietary antioxidants:
- most notably: vitamins C, E, and beta-carotene
- some phytochemicals have antioxidant properties
4 steps of how antioxidants work
- limiting free radical formation
- scavenging or quenching free radicals
- repairing the damage caused by free radicals
- supporting healthy immune function
roles of vit. C (Ascorbic Acid)
- helps to form collagen
- potent antioxidant
- assists in synthesis and conversion of serval hormones (thyroxin) and nuerotransmitters (serotonin)
- aids in absorption of iron
the 5 antioxidant properties of Vit. C
- electron donor (capable of scavenging free radicals)
- restores vitamin E to its active state
- reduces nitrosamines to harmless form
- protects against effects of environmental contaminants and cigarette smoke
- supports immune function
vit. C deficiency: Early symptoms
- gums bleed easily (scorbutic gums)
- pinpoint hemorrhages in capillaries just under the skin
Vit. C deficiency: prolonged
scurvy
- further hemorrhaging & anemia
- muscle degeneration
- dry scaly skin, poor wound healing
- frequent infections
completely curable if caught early - poses little threat
link between nutrition and scurvy
mid 1700’s - British sailors - limited diet, no provisions to prevent spoilage, many became very ill
lead to discovery of “anti-scorbutic factor” in citrus fruits which was later isolated as vitamin C
Vit. C RDA
75mg F
90mg M
increase 35mg in smokers
Vit. C sources
citrus fruits, peppers, dark green veggies, cantaloupe strawberries, tomatoes
Vit. C toxicity
supplements
- nausea, abdominal cramps, diarrhea
can cause Fe overload
pro-oxidation?
Vit. C absorption
limited absorption above 200 mg, most will be lost in urine
intake above UL(2000 mg) = toxic symptoms
Vit. C and the common cold
no consistent effect on duration or severity
minimal to no impact on the duration of common cold
“no meaningful benefit”
Vit. E (tocopherol) roles
- potent antioxidant
- protection of cell membranes, polysaturated fats
Vit. E deficiency
deficiency is rare - usually associated with diseases of fat malabsorption
- damage to cell walls cause RBCs to break open leading to hemolytic anemia
Vit. E RDA
15mg/day
Vit. E sources
polyunsaturated oils, leafy greens, whole grains, eggs, nuts & seeds
Vit E. antioxidant properties
- alpha-tocopherol ( boosts the immune system and helps keep blood clots from forming)
- capable of scavenging free radicals
- protects against damage to arterial walls
- prevents LDL oxidation and oxidation of PUFAs in cell membranes
Vit E prolonged deficiency
results in nerve damage
Vit E. and Performance
no long-term studies and no evidence of improved performance
some research say PA increases oxidative stress (increase O2 consumption - source of free radicals)
Vit E supplements MAY prevent oxidative damage to muscles (especially in extreme environments)
BUT regular exercise increases antioxidant enzymes
Beta-Carotene abd Vit. A roles
- both have antioxidant properties
- fat soluble - prevents LDL oxidation and damage to PUFAs
- scavenges free radicals
- beta-carotene: relatively weak antioxidant
compared to vitamins C & E, other phytochemicals
3 forms of Vit. A active in the body
retinol (main transport/storage form)
retinal
retinoic acid
Vit. A roles in the body
key role in vision
sexual reproduction
maintenance of epithelial cells
growth (bones and teeth)
immunity
Vit. A = “jack of all others” involved in a wide range of physiological processes
Vit. A and Vision: 2 indispensable roles in eye
- aids in maintenance of cornea
- participates in conversion of light energy to nerve impulses at the retina
Vit. A deficiency symptoms
- night blindness
- impaired immunity
- stunted growth
- hyperkeratosis - damage to epithelial cells
- deficiency effects 250 M children worldwide
Vit. A and Beta carotene RDA
RDA expressed in retinol activity equivalents
reflecting that vitamin A can be synthesized from beta-carotene (provitamin A)
700 ug - Female
800 UG - Male
Vit. A sources
liver, fish, milk, butter, eggs
b-carotene sources
carrots, pumpkin, sweet potato, cantaloupe, spinach
Vit. A and Beta carotene UL
3000ug
excessive vit. A is teratogenic (
