Water-Soluble Vitamins

Water soluble

Readily excreted – expensive urine

Can be lost from food by cooking/storage

Typically work as part of enzymes in metabolism

Relatively high absorption rate

Severe deficiencies rare

Vitamins – Niacin, Thiamine, Folic Acid, Riboflavin, B12, and C.

Enrichment Act of 1941 and 1998

Milling of rice, wheat, oats, etc…

significantly reduces nutritional quality

Whole grains contain original nutrients

Enrich with

thiamin, riboflavin, niacin, folate, iron

Enriched grains still

deficient in B-6, magnesium and zinc

ThiaminDestroyed by alkaline and heat

Coenzyme: Thiamin pyrophosphate (TPP)

Absorbed in the jejunum by a carrier-mediated system

Transported by RBC in the blood

Deficiency

Beriberi

Weakness, nerve degeneration, irritability, poor arm/leg coordination, loss of nerve transmission

Edema, enlarge heart, heart failure

Food Sources of Thiamin

Wide variety of food

White bread, pork, hot dogs, luncheon meat, cold cereal

Enriched grains/ whole grains

Thiaminase found in raw fish

1.1 mg/day for women

1.2 mg/day for men

Most exceed RDA in diet

Surplus is rapidly lost in urine; non toxic

Riboflavin

Coenzymes:

Flavin mononucleotide (FMN)

Flavin adenine dinucleotide (FAD)

Oxidation-reduction reactions

Electron transport chain

Citric Acid Cycle

Catabolism of fatty acids

Absorption, Transport, & Metabolism of Riboflavin

HCL in the stomach release riboflavin from its bound forms

Absorption

Active or facilitated transport during low to moderate intake

Passive absorption during high intake

Increase with intake

Transported by a protein carrier in the blood

Functions of Riboflavin

Accepts electrons Electron Transport Chain

FAD FADH2

Succinate Fumarate Citric Acid Cycle

Participates in beta oxidation

FMN shuttles hydrogen ions and electrons to into the electron transport chain

Metabolism of oxidized glutathione

Deficiency of Riboflavin

Ariboflavinosis

Glossitis, cheilosis, seborrheic dermatitis, stomatitis, eye disorder, throat disorder, nervous system disorder

Occurs within 2 months

Usually in combination with other deficiencies

Glossitis (Fig. 10-4)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Who is at Risk For Deficiency?

Rare

Low milk/dairy intake

Alcoholics

Long term phenobarbital use

Food Sources of Riboflavin

Milk/products

Enriched grains

Liver

Oyster

Brewer’s yeast

Sensitive to uv radiation (sunlight)

Stored in paper, opaque plastic containers

RDA for Riboflavin

1.1 mg/day for women

1.3 mg/day for men

Average intake is above RDA

Toxicity not documented

Niacin

Nicotinic acid (niacin) & nicotinamide (niacinamide)

Coenzyme

Nicotinamide adenine dinucleotide (NAD)

Nicotinamide adenine dinucleotide phosphate (NADP)

Oxidation-reduction reaction

Metabolic reactions

Absorption, Transport and Storage of Niacin

Readily absorbed from the stomach and small intestine

Absorption: active transport and passive diffusion

Transported from the liver to all of the tissues where it is converted to the coenzymes

Deficiency of Niacin

Pellagra

3 Ds Occurs in 50-60 daysDecrease appetite & weight

Prevented with an adequate protein dietEnrichment Act of 1941Only dietary deficiency disease to reach epidemic proportions in

the U.S.Who is at risk?

(Untreated) corn as main staple, poor diet, Hartnup disease, alcoholics

Dermatitis of Pellegra (Fig. 10-5)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Food Sources of Niacin

Mushroom

Enriched grains

Beef, chicken, turkey, fish

Heat stable; little cooking loss

60mg tryptophan can be converted into 1 mg niacin

RDA for Niacin

14 NE/day for women

16 NE/day for men

Niacin as a Medicine

75-100 x RDA can lower LDL and TG and increase HDL

Slow/ reverse progression of atheroscelerosis with diet and exercise

Toxicity effects

Flushing of skin, itching, nausea, liver damage

Biotin

Free and bound form

Biocytin (protein bound form)

Biotinidase in small intestine

Metabolism of CHO, fat, protein (C skeleton)

DNA synthesis

Functions of Biotin

Assists in the addition of CO2 to substances

Carboxylation of acetyl-CoA to form malonyl-CoA for the elongation of a fatty acid chain

Addition of CO2 to pyruvate to yield oxaloacetate

Breaks down leucine

Allows 3 essential amino acids to be oxidized for energy

Food Sources of Biotin

Cauliflower, yolk, liver, peanuts, cheese

Intestinal synthesis of biotin

Biotin content only available for a small number of foods

Unsure as to bioavailablity of synthesized biotin

We excrete more than we consume

Avidin inhibits absorption

> a dozen of raw eggs a day to cause this effect

Biotin Needs

Adequate Intake is 30 ug/day for adults

This may overestimate the amount needed for adults

No Upper Limit for biotin

Who is at Risk For Deficiency?

Rare

High intake of raw egg white diet

Alcoholics

Biotinidase deficiency

Anticonvulsant drug use

Signs & symptoms: skin rash, hair loss, convulsion, neurological disorders, impaired growth in children

Vitamin B-6: Pyridoxal, Pyridoxine, Pyridoxamine

Main coenzyme form: pyridoxal phosphate (PLP)

Activate enzymes needed for metabolism of CHO, fat , protein

Transamination

Synthesis of hemoglobin and oxygen binding and white blood cells

Synthesis of neurotransmitters

Deficiency of Vitamin B-6

Microcytic hypochromic anemiaSeborrheic dermatitisConvulsion, depression, confusionReduce immune responsePeripheral nerve damageWho is at risk?

ElderlyAlcoholics

Alcohol decreases absorptionDestroy the coenzyme form

Food Sources of Vitamin B-6

Meat, fish, poultry

Whole grains (not enriched back)

Banana

Spinach

Avocado

Potato

Heat and alkaline sensitive

RDA for Vitamin B-6

1.3 mg/day for adults

1.7 mg/day for men over 50

1.5 mg/day for women over 50

Daily Value set at 2 mg

Average intake is more than the RDA

Factors That Affect B-6 Requirement

L-DOPA-medication used to treat Parkinson’s disease and

Isoniazid-antituberculosis medication

Reduce blood concentration of PLP

Need extra vitamin B-6

Preeclampsia

Reduce blood concentration of PLP

Will supplementation will reduce preeclampsia?

B-6 As A Medicine?

PMS

B-6 to increase the level of serotonin

Improve depression

Not a reliable treatment

Carpal tunnel syndrome

Toxicity potential

Can lead to irreversible nerve damage with > 200 mg/day

Folate (Folic acid, Folacin)

Consists of pteridine group, para-aminobenzoic acid (PABA), and glutamic acid

Coenzyme form: tetrahydorfolic acid (THFA)

Functions of Folate

DNA synthesis

Transfer of single carbon units

Synthesis of adenine and guanine

Anticancer drug methotrexate

Homocysteine metabolism

Neurotransmitter formation

Deficiency of Folate

Similar signs and symptoms of vitamin B-12 deficiency

Pregnant women

Alcoholics

Interferes with the enterohepatic circulation of bile/folate

Neural Tube Defects

Spina bifida

Anencephaly

Importance of folate before and during pregnancy

(Fig. 10-8)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Food Sources of Folate

Liver

Fortified breakfast cereals

Grains, legumes

Foliage vegetables

Susceptible to heat, oxidation, ultraviolet light

RDA for Folate

400 ug/day for adults

Daily Value is set at 400 ug

Vitamin B-12

Cyanocobalamin. methlcobalamin,

5-deoxyadenosylcobalamin

Contains cobalt

Folate metabolism

Maintenance of the myelin sheaths

Rearrange 3-carbon chain fatty acids so can enter the Citric Acid Cycle

Absorption of Vitamin B-12 (Fig. 10-10)

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Functions of Vitamin B-12

Helps convert methylmalonyl CoA to succinyl CoA (citric acid cycle)

RBC formation

Nerve functions

Maintains myelin sheath

Megalobalstic anemia

Deficiency of Vitamin B-12

Pernicious anemiaNever degeneration, weakness

Tingling/numbness in the extremities (parasthesia)

Paralysis and death

Looks like folate deficiency

Usually due to decreased absorption ability

Achlorhydria especially in elderly

Injection of B-12 needed

Takes ~20 years on a deficient diet to see nerve destruction

Who is at Risk For Deficiency?

Vegans

Breastfed infants of vegan moms

Elderly

Individuals with AIDS or HIV

Food Sources of Vitamin B-12

Synthesized by bacteria, fungi and algae

(Stored primarily in the liver)

Animal products

Organ meat

Seafood

Eggs

Hot dogs

Milk

RDA for Vitamin B-12

2.4 ug/ day for adults and elderly adults

Average intake exceeds RDA

B-12 stored in the liver

Non-toxic

Vitamin C

Ascorbic acid (reduced form), dehydroascorbic acid (oxidized form)

Synthesized by most animals (not by human)

Absorbed by a specific energy dependant transport system

Passive transport if intake is high

Decrease absorption with high intakes

Excess excreted

Functions of Vitamin C

Reducing agent (antioxidant)

Iron absorption

Synthesis of carnitine, tryptophan to serotonin, thyroxine, cortiscosteroids, aldosterone, cholesterol to bile acids

Immune functions

Cancer prevention?

Collagen synthesis

Collagen Synthesis (Fig. 10-12) Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

Antioxidant

Can donate and accept hydrogen atoms readily

Water-soluble intracellular and extracellular antioxidant

Must be constantly enzymatically regenerated

Needs are higher for smokers

Deficiency of Vitamin C

ScurvyDeficient for 20-40 days Fatigue, pinpoint hemorrhagesBleeding gums and joints. HemorrhagesAssociated with poverty

Rebound scurvyimmediate halt to excess vitamin C supplements

Who is at risk?Infants, elderly men Alcoholics, smokers

Food Sources of Vitamin C

Citrus fruits

Potatoes

Green peppers

Cauliflower

Broccoli

Strawberries

Romaine lettuce

Spinach

Easily lost through cooking

Sensitive to heat

Sensitive to iron, copper, oxygen

RDA for Vitamin C

90 mg/day for male adults

75 mg/day for female adults

+35 mg/day for smokers

Average intake ~72 mg/day

Fairly nontoxic (at <1 gm)

Upper Level is 2 g/day

Warning to people with hemochromatosis, oxalate kidney stones