Vitamins, Antioxidants, and Free Radical Scavengers Flashcards
What are vitamins?
Vitamins are macronutrients required by the body to carry out a range of normal functions. However, these macronutrients are not produced in our bodies and must be derived from the food we eat
- Not produced by the body so need to get them from food
Vitamins?
- Organic compounds essential for normal functioning growth and maintenance of the body
- Needed in small amounts (fat soluble especially)
- Not an energy source
- Individual units rather than long chains
How does food preparation affect vitamin?
Factors that determine amounts
- Source (animal vs. plant)
- Sunlight
- Moisture
- Growing conditions
- Plant’s maturity at harvest
- Packaging and storage
By cooking food or preserving it, vitamins can be lost
Mandatory Fortification of foods in Canada?
- Fortified vitamin D in milk
- Folate and niacin must be added to flour
- Potential problems – junk foods and deception
What is a consequence of vitamin D deficiency?
Not taking in as much calcium
Why are some people vitamin deficient?
- Some people are deficient in enzymes to uptake vitamins
- Some medication prevents some vitamin uptake
- At different times in life, need more/less vitamins
What are provitamins?
- Inactive forms of vitamin
- Body must change them to active form
Example: Beta-carotene
Need enzymes to break it down to be able to absorb it as vitamin A
A provitamin is a substance that may be converted within the body to a vitamin
What are the types of vitamins? (2)
- Water soluble
- Fat-soluble
Water soluble vitamins?
B1: thiamine
B2: riboflavin
B3: Niacin
B5: pantothenic acid
B6: pyridoxine
B7: Biotin
B9: Folic acid
B12: Cobalamin
C: ascorbic acid
Fat-soluble vitamins?
A: Retinol-al-oic acid
D: Cholecalciferol
E: Tocopherol
K: Phylloquinone
Differences in Vitamin Digestion?
Micelle: aggregate of surfactant amphipathic lipid molecule dispersed a liquid forming a colloidal suspension
Important in transport of vitamins into the intestinal epithelial cells
Chylomicrons: important in the movement of vitamins from gut epithelial cells into the lymphatics
What system takes up vitamins first?
The lymphatic system takes up vitamins first, it is involved in immune function
Fat soluble molecules features?
- Vitamins A, D, E, and K have lipid solvent solubility, diverse nonenzymatic functions, sequestration in lipid vacuoles and adipose, and greater risk for toxicity
How are fat soluble molecules absorbed?
- Like dietary triglycerides, fat-soluble vitamins are solubilized in the duodenal lumen in the presence of bile and pancreatic enzymes
- Fat-soluble vitamins are maintained within the lipophilic core of mixed micelles
- Next, pancreatic esterase’s, in the presence of bile salts, catalyze the release of fat-soluble vitamins from esters
- Stays in the body longer than water soluble vitamins, fat-soluble can accumulate
Absorption of Fat soluble vitamins?
Fat soluble vitamins
Together with fatty acids derived from triglycerides, fat-soluble vitamins are released from micelles at the enterocyte brush border membrane
At high doses, vitamins A and E can be absorbed directly from water-miscible emulsions. The next steps involve incorporation into the chylomicrons for secretion into lymphatics and ultimate uptake by the liver
Intestinal, biliary, and pancreatic diseases that cause decreased dietary lipid absorption may cause a decrease in the absorption of fat-soluble vitamins
Vitamin A also known as?
The retinoids
What are the active forms of Retinoids?
Retinol
Retinal
Retinoic Acid
o Precursors (carotenoids)
Adapalene is a retinoid
Vitamin A is important in what? (6)
- Vision: night and day
a. Becomes part of retina
b. Keeps eye surface healthy
c. Allows night and colour vision - Immune function
a. Produce immune cells to fight microorganisms - Cell production and differentiation
a. Regulates production of enzymes, blood carrier proteins, and structural proteins (like those in skin) - Skin
a. Needed to replace epithelial cells of you skin - Reproduction
a. Keep reproductive tracts healthy
b. Women: maintain fertility, Men: sperm production
c. Embryo development - Bones
a. Helps produce bone cells
b. Required for bone remodeling a increase in osteoclasts
Vitamin A and vision?
Vitamins A is a precursor of rhodopsin, the pigment found in rods within the retina, helps us see at night.
Without vitamin A “night blindness” occurs
Rods are not properly formed if Vitamin A deficient
Rod vs Cones?
Rods outnumber cones 20:1
Rods: night vision
Cones: day vision
Vitamin A is a required precursor for the formation of rhodopsin, the photopigment in rods
Sources of Vitamin A?
Will get enough if you have a balanced diet
Exceptional source: beef liver carrots, sweet potatoes
High sources: spinach, mango, broccoli
Good sources: dried plums, milk
Vitamin A deficiency can lead to?
- The issue in the eye
o Xerophthalmia (inability to see - The skin and other epithelial cells
o Keratin issues - Immune function
o Vulnerable to infection - Other effects
o Growth retardation, bone deformations, defective teeth, and kidney stones
Vitamin A toxicity symptoms?
- Fatigue, vomiting, abdominal pain, bone and joint pain, loss of appetite, skin disorders, headaches, blurred or double vision, liver damage
1. Teratogen (birth defects, if have too much when pregnant
a. Agent that causes birth defects: clef palate, heart abnormalities
2. Discoloration of skin
3. Acne treatment: Retin A and Accutane
(vitamin A is used in a lot of beauty product which can be bad during pregnancy)
Vitamin A has been linked to an increased risk for hip fracture in postmenopausal women, lung cancer, cardiovascular mortality and total mortality
Vitamin D forms?
Forms:
- Activated in the liver and kidney
- 25-hydroxyvitamin D [25(OH)D]
Vitamin D functions?
- Essential for bone health
- Helps regulate insulin formation and secretion
- Calcium absorption
Vitamin D sources?
- Exposure to sunlight
- Fortified foods, milk, cereal
- Oily fish, egg yolk, cod liver oil
- supplements
Why is vitamin D needed in the body?
- vitamin D enters the body from the diet or the synthesis in the sky
- vitamin D must be chemically modified first by the liver and then by the kidneys to function
- active vitamin D increase the absorption of calcium and phosphorus in the intestines
- active vitamin D also increases bone breakdown which releases calcium and phosphorus into the blood, at the kidneys, calcium retention is stimulated reducing the amount lost in the urine
- normal levels of blood calcium and phosphorus support mineralization of the bones
What is Vitamin D soluble in?
Chylomicrons
Vitamin D signaling?
Vit D binds VDR in the cytoplasm, moves into the cell nucleus
In nucleus binds RXR (retinoid X receptor)
This binds to the transcription factor (VDR response element)
This regulates gene coding
To regulate: proliferation, differentiation, apoptosis, oxidative stress, membrane transplant, Inflammation, tissue mineralization, adhesion
Vitamin D deficiency?
Deficiency
- rickets in children (impaired calcium absorption, bones don’t form)
- Osteomalacia and osteoporosis in adults
Vitamin D toxicity?
Toxicity:
- Hypercalcemia (stones, groans, thrones, psychiatric overtones), calcium stones
- Usually, minimal
Newborns are usually given Vitamin D supplements (especially in winter)
Does Vitamin D have chemo preventative properties?
Vitamin D has no chemoprevention effects (doesn’t prevent cancer)
Vitamin E forms?
- Family of 8 similar compounds
- Only alpha tocopherol considered for human vitamin E requirement
- Stored mainly in body fat
Vitamin E functions?
- Antioxidant
o Protects cell membranes from free radicals
o May lower risk of some chronic diseases
It has many effects on tissue systems
Dietary recommendations of Vitamin E?
Dietary recommendations
- Related to intake of polyunsaturated fatty acids
- RDA
o 15mg/day alpha tocopherol
o 19mg/day for breastfeeding
Vitamin E sources?
- Nuts, seeds, vegetable oil, whole grain, fruit, vegetables, animal products
Vitamin E Deficiency?
Deficiency:
- Occurs with fat malabsorption or rare genetic disorders
Vitamin E toxicity?
Toxicity:
- Nontoxic and adverse effects have not been found
- Can interfere with blood clotting
- Lung injury when inhaled, banned from e-cigarettes