Transcript Document

Chemistry 106
University of Nebraska
Spring 2009
Husker Baseball
27 March 2009
Vitamin D
• several vitamin D’s exist, with slightly different molecular structure,
but with identical physiological function
• characteristics
•Fat-soluable vitamin
• excess only occurs from overdosing of supplements
• most common of D vitamins: D3, chloracalciferol
• sources: formed from sunlight striking skin & converting
7-dehydrocholesterol into D3 or from drinking fortified milk
• deficiency symptoms: poor bone development in children and
rickets in adults
Know this structure
for test!!
Vitamin D3
Cholesterol
Vitamin C
• Chemical name: ascorbic acid (is carboxyl acid)
• Characteristics
– Water soluble vitamin
– food sources: citrus fruits- and vegetables
– destroys bacteria/viruses, healing of wounds
– deficiency symptoms: scurvy (bleeding of gums, loss of
teeth, lethargy)
Be able to recognize for
test!!!
Vitamin E
• Fat Soluble vitamin
• Unique among vitamins in that its primary function is as
an antioxidant, especially in the lungs (vitamin C also
has some antioxidant properties)
• Important in maintenance of cell membranes, essential
for reproduction
• Lack of E can cause sterility and contribute to muscular
dystrophy
• Widely distributed in many foods
“B” Vitamins
Many B vitamins act as coenzymes
• Coenzymes: small molecules that work in
conjunction with enzymes to enhance
enzyme activity
• Niacin: critical role in energy transfer during
glucose and fat metabolism
• Niacin is present in the coenzyme
nicotinamide adenine dinucleotide (NAD+ and
NADH)
Vitamin Myths
• What do massive doses of Vitamin C do in
the body?
– Water soluble – not stored
– Relatively nontoxic
– Other vitamins (A & E for example) can be toxic
by overdose
• Does Vitamin C really cure disease?
– Linus Pauling (1971) claimed it does
– Large-scale studies since then show no
advantage to massive doses of the vitamin
– However, the myth persists especially about
curing the cold
– “Placebo Effect” – if you think it will work, it will
– Although vitamins might prevent disease no one
knows if they can cure disease.
Natural versus Synthetic
Vitamins
•An iron atom obtained from iron ore dug from the
earth is no different that than an iron atom found in a
steak
•The use of iron in heme molecule requires vitamin B12
as a coenzyme
Natural versus Synthetic
Vitamins
•Just like iron, vitamin B12 although a compound,
contains the same atoms and arrangement whether it
comes from food or a pill
•Vitamin B12 (cobalamin) is obtained from ingesting
meats (along with iron)
• It is also obtained from vitamin supplements (which may
or may not contain iron)
• Similarly iron may be obtained from mineral supplements
(which may or may not contain cobalamin)
Natural versus Synthetic Vitamins
Not vitamin C
Vitamin C from different sources
The stereochemistry of vitamin C. All molecules of vitamin C have
this structure and stereochemistry, regardless of their source
The Health Food/Junk Food
Debate
• Health food:
• food that is organic, natural or without
chemicals (is this possible?)
• unprocessed, fresh, no sugar, fat or
cholesterol
• food supplying a large number of mincronutrients
compared its calorie content
The Health Food/Junk Food
Debate
• Junk food:
– food containing a large number of calories but
with few nutrients_- (empty calories)
– highly processed sweet food, snacks, “fast”
food
Nutrition Content Labeling
• Recommended Daily Allowances (RDA)
– Levels of intake of essential nutrients judged
to meet the nutritional needs of the majority
of healthy individuals
– Help provide a standard for daily dietary intake of
micronutrients
– No RDA has been established for carbs or fats (
there is one for protein)
– One size fits all philosophy doesn’t fit anyone
Nutrition Content Labeling
• Reference Daily Intake (RDI)
– Highest RDA micronutrient allowance
– Excluding pregnant or nursing mothers
• Daily Reference Value (DRV)
– Highest RDA macronutrient allowance
(includes carbs, fats, proteins)
• Daily Value (DV) (% Daily Value)
– Combineds RDI and DRV
– usually based on 2000 calories/day
Nutrition Content Labeling
• “Nutrition Facts”
– Found on labels of processed foods
(cereal, etc) – based on %DV
– Ingredients listed in order of decreasing
weight
– Includes chemicals we think of as food
additives
Nutrition Content Labeling
• “Nutrition Facts” based on
– 2000 calories/day
– Fats subdivided into saturated and
unsaturated types
– Carbohydrates categorized as sugars and
fiber
– Total protein- is always listed
– Based on standard serving size (set by
Feds)
Food Additives
• A quick history lesson
– Salt (NaCl) used for centuries as
preservatives
– Egyptians used food dyes 3500 yrs ago !!
– Using herbs, spices, & honey to enhance
flavor practiced for centuries
– Used to cover rank smell and taste of
rancid food
Food Additives
• History of food additive regulation in
the U.S.
– Late 1800’s U.S. Patent Office issued first
patent for food additive (NaCl and Ca3
(PO4)2)
– 1902: Dr. Harvey Wiley (chemist) used
volunteers to test additives by eating them
– Upton Sinclair’s “The Jungle” highlighted
slaughterhouse and meat processing
facility filth and unsanitary conditions in
early 1900’s
Food Additives
• History of food additive regulation in
the U.S.
– Sinclair’s book stimulated passing of
• 1906 Meat Inspection Act
• 1906 Pure Food and Drug Act
– 1906 food and drug administration (FDA)
created
Food Additives
• Today Pure Food and Drug Act includes
cosmetics – Federal food, drug and cosmetic
act
• A food additive is any substance added to
food to produce a specific, beneficial result
– One type of additive:
• Substances used as an additive before Jan. 1, 1958
• Substances that through long usage we generally
recognize as safe
• GRAS (Generally recognized as safe) list– substances
not requiring constant testing for safety
• anise, cinnamon, ascorbic acid, etc
Food Additives
• A second type of additive
– Compounds shown by scientific studies to
be safe
– Must be tested- prior to use
– Includes newly developed chemicals
– Butylated hydroxytoluene (BHT),
pyridoxine hydrochloride
BHT