Vitamins and minerals
Learning objectives
Understand why V/M are essential to healthy living;
Understand that there are healthy intake levels for V/M and
that excesses may be worse than deficiencies;
Know the four fat soluble vitamins and basic roles;
Know the water soluble vitamins we discuss in class and their
roles;
Know the roles of the minerals we discuss in class;
Know that processing and storage may affect some vitamins
more than others.
What is wrong with “If a little is good, more must be better”?
Fat soluble vitamins
ADEK
Dissolve in organic solvents – methanol, gasoline etc..
Can build up because they are not excreted
Absorbed during fat absorption
Transported in lipoproteins
Vitamin A – carotenoids and retinoids
Vitamin D – cholesterol product
Vitamin E – tocopherols
Vitamin K – menaquinones and phylloquinones
Vitamins
Essential organic substances
Yield no energy, but facilitate energy-yielding chemical
reactions
If absent from a diet, it will produce deficiency signs and
symptoms
Preservation of vitamins in foods
exposure to light, heat, air, water, and alkaline
Vitamin A
Two general types
Pre-formed
retinoids are found in animal products
Precursors
carotenoids are found in plant products
beta carotene, lutein, lycopene, others
must be converted to retinoids
absorbed and converted by intestinal cells
Absorption of Vitamin A
Requires bile, digestive enzymes, integration into micelles
Dependent on the fat in the diet
olestra
90% of retinoids can be absorbed
Only ~3% of carotenoids are absorbed
so eat your carrots
Intestinal cells can convert carotenoids to retinoids
Transport in body/storage
Liver stores 90% of vitamin A in the body
polar bear liver
Reserve is adequate for several months
Transported via chylomicrons to the liver
Transported from the liver as retinol via retinol-binding
protein to target tissue
Carotenoids can be transported via VLDL
Functions of Vitamin A
Night and color vision
xerophthalmia
Cell health and maintenance
epithelial cell differentiation and division
cells deteriorate without Vit A
follicular hyperkeratosis
Antioxidant
Macular Degeneration
lutein
The vision cycle
Sources of Vitamin A
Retinoids - animals
Liver, fish oils, fortified milk, eggs
50% of vitamin A intake is from these sources
Carotenoids - plants
dark green leafy
yellow orange
the other 50%
Overdose of a Vitamin?
High doses of vitamin A are toxic
HYPERVITAMINOSIS A
3 – 10x supplements
Teratogenic – birth defects/spontaneous abortion
3x RDA
Carcinogenic – some feeding trials with smokers
3 – 10x RDA
Fatal dose – 12 gram
How much do we need?
International unit (IU)-crude method of measurement
Retinol activity equivalent (RAE) -current, more precise
method of measurement
1 ug of retinol = 1 RAE = 3.3 IU =12 ug beta-carotene =
24 ug of other provitamin A
RDA
900 REA men
Supplement or no?
700 REA women