Antioxidants Flashcards
What are antioxidants?
Vitamins: fat-soluble (beta-carotene, E & A); water-soluble (C)
Minerals: trace (Selenium, Copper, Zinc, Manganese, and Iron)
What are free radicals?
- unstable atoms that contain an unpaired electron in the outer orbital (shell)
What function do antioxidants serve?
Antioxidants reduce naturally-occurring reactive oxidizing species (ROS), or damage caused by ROS that have one unpaired electron in their outer orbital.
- Neutralize free radicals
- Inhibit oxidant formation
- Intercept oxidants once they are formed
- Repair oxidant-induced damage
Name three enzymes that require mineral antioxidants to function.
- glutathione peroxidase (requires Se)
- superoxide dismutase (requires Cu, Zn, Mn)
- catalase (requires Fe)
Compare the vitamin antioxidants with the mineral antioxidants.
Vitamin antioxidants donate their electrons to the unpaired electron in the outer orbital of the free radical, thereby neutralizing the free radical and ending the chain reaction.
Mineral antioxidants activate enzymes to destroy free radicals (converted to less damaging molecules that are excreted from the body).
What substances do free radicals target?
Free radicals destabilize other molecules and damage:
- cell membranes (lipids)
- cellular proteins
- blood LDL lipoproteins
- nuclear DNA
How are free radicals formed?
- endogenously: normal products of metabolic processes (eg - oxidizing macronutrients, immune responses, production of ATP)
- exogenously: environmental (eg - radiation from the sun, pollution, tobacco smoke, etc…)
Provide examples of free radicals.
- superoxide radical (O2- )
- hydroxyl radical (OH)
- nitric oxide (NO)
Describe the interrelationship between vitamin E and C.
- Active vitamin E (an antioxidant) donates one of its hydrogen atoms (with accompanying electron) to a lipid radical.
- Vitamin E is no longer active, but it has stopped the lipid radical from creating further camage and generating more free radicals.
- Vitamin E can be reactivated by accepting a hydrogen atom from vitamin C (ascorbic acid).
- Both the reduced & oxidized forms of vitamin C are stable.
Provide three rich sources of vitamin C.
- kale
- red bell pepper
- guava
- kiwi
- broccoli
- tomato
- blueberries
- oranges
Provide three rich sources of vitamin E.
- brazil nuts
- sunflower seeds
- wheat germ
(nuts, seeds)
Provide three rich sources of beta-carotene.
- carrots
- yams
- kale
- tomatoes
- kale
(leafy greens, red/orange veggies)
Provide three rich sources of iron.
- lentils
- hempseeds, linseed
- pumpkin seeds
- kale
- beans
- tofu
- oats
- spinach
- red meat, shellfish (disgusting)
Provide three rich sources of copper.
- spirulina
- nuts and seeds
- leafy greens
- dark chocolate
- shiitake mushrooms
Provide three rich sources of selenium.
- brazil nuts
- pork, beef, turkey, chicken, fish, and eggs. (ewwww)
Provide three rich sources of manganese.
- brown rice
- almonds, pecans
- pinto beans, legumes
- oatmeal,
- leafy green vegetables
- pineapple
- dark chocolate
Provide three rich sources of zinc.
- chickpeas
- lentils, and beans
- nuts and seeds
- whole grains
- meat, shellfish, dairy, eggs (nasty af don’t support this!)
What are the two stable forms of vitamin C?
Ascorbic acid (reduced form)
Dehydroascorbic acid (oxidized form)
What are the 3 ‘natural sets’ of antioxidant nutrients a la FNH 250?
- Vitamin E, Selenium & Vitamin C
- Beta-Carotene & Vitamin A
- Copper, Zinc, Manganese, & Iron
Is taking antioxidant supplements a good idea?
Myths:
- Antioxidants are all vitamins
- All antioxidants are created equal
- It’s important to eat “super fruits”
- You should amp up your intake with supplements
- If some antioxidants are good, more are better
- Packaged food with labels touting antioxidants will boost your health.
How many forms of tocopherols are there?
- tocopherols “to bring forth birth” (aka Vitamin E) has 8 forms
What form of vitamin E has effective biological activity?
alpha-tocopherol
What is the bioavailability of vitamin E and where is it stored in the body?
- moderate bioavailability (~20-70%)
- mostly stored in adipose (~90%), some in cell membranes, little in liver
What are the fat-soluble vitamins?
beta-carotene, E, and A
What are the water-soluble vitamins?
C
Define: bioavailability.
The proportion of a drug or other substance (eg - nutrients in food) which enters the circulation when introduced into the body and so is able to have an active effect.
Give an introduction for selenium, (trace mineral).
- high bioavailability (~60-90%)
- homeostasis regulated by the kidneys
- high potential for toxicity with supplements
There are 25 selenoproteins (proteins bound to selenium) known in humans. What are the most common?
- selenocysteine (active Se)
- selenomethionine (storage Se)
How is vitamin E lost during food preparation?
Vitamin E is readily destroyed by heat (eg - deep frying), and exposure oxygen & light.
Keep oils in cool, dark cupboard or fridge.
What is the primary action of vitamin C?
Vitamin C primarily acts as a reducing agent (electron donor).
Discuss the absorption of vitamin C in the body.
Absorption (<100mg): 80+%
Absorption (1000mg): ~50%
Excess vitamin C is excreted in urine.
What are the antioxidant roles of Vitamin E?
Vitamin E maintains membrane integrity:
- in cell membranes - neutralizes free radicals, maintains integrity of membranes (especially lung)
- in nuclear and mitochondrial membranes - protects DNA and other celluar compounds from oxidative damage.
What is the antioxidant role of selenium?
Selenium, through its role in glutathione peroxidase, reduces production of free radicals, and spares use of vitamin E.
- Cofactor for glutathione peroxidase enzyme (riboflavin is a necessary coenzyme) - protects cell membranes.