The Water-Soluble Vitamins

B vitaminsVitamin C

B Vitamins Originally thought to be one vitamin 8 of them Act primarily as coenzymes in

metabolic pathways Important for ATP production!!!

Important for MANY additional functions.

B Vitamins Dietary requirement is linked

closely to metabolic rate (i.e., production)

Ruminant requirements met by rumen bacterial synthesis

Hindgut bacterial synthesis and absorption is insufficient to meet full requirements for a horse

B Vitamins-Sources

VARIETY of foods! Plant sources

Found in fibrous portion of plants

Most cereals and grain products are enriched

Animal sources Liver Milk Egg Beef, pork and chicken

B Vitamin-Deficiency LOTS of symptoms including

fatigue Specific diseases for each vitamin

deficiency (e.g., beriberi, pellagra)

Thiamin (B1) Present in tissues as thiamin

pyrophosphate (TPP) TPP is an essential coenzyme for oxidative

decarboxylation of alpha-keto acids pyruvate to acetyl CoA

Deficiency beriberi in humans polyneuritis in birds bracken fern poisoning in ruminants and

horses antithiamin activity

Polyneuritis

Riboflavin (B2)

Essential constituent of flavoproteins (e.g., FAD)

Hydrogen carrier in glycolysis, TCA and oxidative phosphorylation

Deficiency curled toe paralysis in birds

Curled Toe Paralysis

Nicotinamide (niacin) Amide derivative of nicotinic acid

Can be synthesized from trytophan Essential constituent of NAD and NADP Hydrogen carrier catalyzed by

dehydrogenase enzymes ATP synthesis

Deficiency Pellagra in farm animals and humans

Fiery inflammation of tongue, mouth and upper esophagus

Pyridoxine (B6)

Active form is pyridoxal phosphate Essential coenzyme for

transamination and decarboxylation of amino acids

Deficiency None in farm animals

Pantothenic acid Dipeptide derivative of alanine and

a butyric acid derivative Essential constituent of coenzyme

A Acyl transfer

Deficiency None in farm animals

Folic acid (folacin) Tetrahydrafolic acid is active

functional form Carrier of one-carbon (e.g., methyl)

groups Deficiency

None in farm animals

Focus on Folate Important for proper

neural development during fetal growth.

Controlled, clinical intervention trial showed decreased risk of spina bifida in women supplemented with folate

“problems” with study Current

recommendation

More on Folate May also reduce

(greatly) risk for heart disease

Dietary Sources Animal sources

Liver Crab meat

Plant sources Spinach Lentils Dried beans Fortified cereal products!

Biotin Coenzyme involving CO2 transfer

acetyl CoA to malonyl CoA Propionyl CoA to methylmalonyl CoA Pyruvate to oxaloacetate

Deficiency Fatty liver and kidney syndrome, a fatal

metabolic disorder in chicks and turkey poults Raw egg white (avidin) can block

absorption

Cyanocobalamin (B12) Active form is cyanide derivative of

cobalamin Cobalt is an integral component Coenzyme for numerous reactions

Methylmalonyl CoA to succinyl CoA DNA synthesis Transmethylation (methionine synthesis)

Deficiency Pernicious anemia in humans (lack intrinsic

factor) Wasting disease in ruminants (Co deficiency)

Vitamin C Discovery

Sailors used to die from disease called “scurvy.”

James Lind conducted first human nutrition intervention trial and found that citrus fruits prevented scurvy.

Why Brits are called “limeys.”

Vitamin C Ascorbic acid Antioxidant

Protects cells from free radicals Protects iron from oxidative damage, thus

enhancing iron absorption in the gut Required for various hydroxylation reactions

proline to hydroxyproline for collagen synthesis

Deficiency Not in farm animals Scurvy in humans

Vitamin CRoles in the Body Stress (e.g.,

infections, smoking) Mechanism unknown,

but vitamin C requirements increase during stress

Common cold? Disease prevention?

Cancer, heart disease: stay tuned…

Vitamin CDeficiency Scurvy

Bleeding gums Small red spots on

skin Rough skin Wounds fail to

heal Weak bones and

teeth Anemia and

infections

What about vitamin supplements? Remember, most supplements that you

can buy aren’t actually vitamins. Megadosing (> 500% RDA) almost never

recommended No harm in “one-a-day” type Probably prudent in

Those who do not eat certain types of food People with generally poor diets

Don’t get lazy BECAUSE you take a supplement.