Chemistry 106University of Nebraska

Spring 2009

27 March 2009

Husker Baseball

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

Vitamin D3

Cholesterol

Know this structure for test!!

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

Vitamin C from different sourcesNot vitamin C

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