chapter 8: the vitamins. vitamins essential organic substances yield no energy, but facilitate...

Chapter 8: The Vitamins

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

• Fat-soluble vitamins

• Water-soluble vitamins

• Antioxidants

Fat-Soluble Vitamins Overview

• Dissolve in organic solvents

• Not readily excreted; can cause toxicity

• Absorbed along with fat

• Transported like fat in chylomicrons, VLDL, LDL

Vitamin A

• Most common cause of non-accidental blindness• Preformed

– Retinoids

– Found in animal products

• Proformed– Carotenoids – Found in plant products

Functions of Vitamin A

• Night blindness

• Xerophthalmia

• Cell health

• Growth, development, reproduction

• Cardiovascular disease prevention

• Cancer prevention

Cell Health

• Vitamin A maintains health of cells that line internal and external surfaces (epithelial cells)

• Barriers to bacterial infections• Epithelial cells produce mucus• Without vitamin A, these cells do not

produce mucus• Increases infections and decreases immune

system

Cancer and Cardiovascular Disease

• Role in cell development and immune-system• Role as an antioxidant• Lower risk of breast cancer with vitamin A

supplements• Megadose is not advise• Mixed results in cancer/vitamin A studies• Foods rich in vitamin A and other phytochemicals

are advised

Vitamin A and Your Skin

• Topical treatment and oral drug

• Accutane (oral) and Retin-A (topical)

• Can induce toxicity symptoms

• Not recommended for pregnant women

• Use only under supervision of a physician

Sources of Vitamin A

• Preformed– Liver, fish oils, fortified milk, eggs– Contributes to half of all the vitamin A intake

• Proformed– Dark leafy green , yellow-orange

vegetables/fruits– Contributes to half of all the vitamin A intake

Vitamin A from the Food Guide Pyramid

Deficiency of Vitamin A

• Night blindness

• Decrease mucus production

• Leading to bacterial invasion in the eye

• Irreversible blindness

Measuring Vitamin A

• 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 for Vitamin A for Adults

• 900 REA for men

• 700 REA for women

• Average intake meets RDA

• Much stored in the liver

• Vitamin A supplements are unnecessary

• No separate RDA for carotenoids

Toxicity of Vitamin A

• Large intake of vitamin A over a long period

• Bone/muscle pain, loss of appetite, skin disorders, headache, dry skin, hair loss, increased liver size, vomiting

• Discontinue supplement is recommended

• Possible permanent damage

Vitamin D

• Prohormone

• Derived from cholesterol

• Synthesized from sun exposure

• Insufficient sun exposure makes this a vitamin

• Activated by enzymes in liver and kidneys

• Deficiency can cause diseases

Functions of Vitamin D

• Regulates blood calcium– Helps calcium absorption– Reduces kidney excretion of calcium– Regulates calcium deposition in bones

• Influences cell differentiation– Linked to reduction of breast, colon, and

prostate cancer

Role in Bone Formation

• Vitamin D causes Ca + Phos to deposit in the bones

• Strengthen bones

• Rickets is the result of low vitamin D

• Osteomalacia (soft bone) is rickets in the adult

Food Sources of Vitamin D

• Fatty fish (salmon, herring)

• Fortified milk

• Some fortified cereal

The Adequate Intake (AI) for Vitamin D

• 5 ug/d (200 IU/day) for adults under age 51 • 10-15 ug/day (400 - 600 IU/day) for older

Americans• Light skinned individuals can produce

enough vitamin D to meet the AI from casual sun exposure

• Infant are born with enough vitamin D to last ~9 months of age.

Toxicity Warning • Vitamin D can be very toxic• Regular intake of 5-10x the AI can be toxic• Result from excess supplementation (not from

sun exposure or milk consumption)• S/S: over absorption of calcium

(hypercalcemia), increase calcium excretion• Calcium deposits in kidneys, heart, and blood

vessels• Mental retardation in infants

Vitamin E

• Fat-soluble antioxidant• Resides mostly on cell membranes

Redox Agent

• Vitamin E is able to donate electron to oxidizing agent

• Protects the cell from attack by free radicals

• Protects PUFAs within the cell membrane and plasma lipoproteins

• Prevents the alteration of cell’s DNA and risk for cancer development

Vitamin E, An Antioxidant

Food Sources of Vitamin E• Plant oils

• Wheat germ

• Asparagus

• Peanuts

• Margarine

• Nuts and seeds

• Actual amount is dependent on harvesting, processing, storage and cooking

Food Sources of Vitamin E

RDA for Vitamin E

• 15 mg/day for women and men• (=22 IU of natural source or 33 IU of

synthetic form)• Average intake meets RDA1 mg d--tocopherol = 0.45 IU (synthetic

source)1 mg d--tocopherol = 0.67 IU (natural

sources)

Vitamin K (“Koagulation”)

• Synthesized by the bacteria in the colon and are absorbed

• Role in the coagulation process• Calcium-binding potential

Drugs and Vitamin K

• Anticoagulant– Lessens vitamin K reactivation– Lessens blood clotting process– Monitor vitamin K intake

• Antibiotics– Destroy intestinal bacteria– Inhibit vitamin K synthesis and absorption– Potential for excessive bleeding

Food Sources of Vitamin K

• Liver

• Green leafy vegetables

• Broccoli

• Peas

• Green beans

• Resistant to cooking losses

• Limited vitamin K stored in the body

Adequate Intake for Vitamin K

• 90 ug/day for women• 120 ug/day for men• Amount met by most• Excess vitamins A and E interferes with

vitamin K• Newborns are injected with vitamin

K(breast milk is a poor source)• Toxicity unlikely; readily excreted

Overview of Water-Soluble Vitamins

• Dissolve in water

• Generally readily excreted

• Subject to cooking losses

• Function as a coenzyme

• Participate in energy metabolism

• 50-90% of B vitamins are absorbed

• Marginal deficiency more common

Enrichment Act of 1941 and 1998

• Many nutrients lost through milling process of grains

• Grain/cereal products are enriched

• Thiamin, riboflavin, niacin, folate, iron

• Whole grains contain original nutrients

• Enriched grains still deficient in B-6, magnesium and zinc

Thiamin

• Contains sulfur and nitrogen group

• Destroyed by alkaline and heat

• Coenzyme

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

RDA For Thiamin

• 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

• Participate in many energy-yielding metabolic pathways

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

• Coenzymes• Needed when cell energy is being utilized• Synthetic pathways require niacin

Deficiency of Niacin

• Pellagra– 3 Ds – Occurs in 50-60 days– Decrease appetite & weight

• Prevented with an adequate protein diet• Enrichment Act of 1941• Only dietary deficiency disease to reach epidemic

proportions in the U.S.

Food Sources of Niacin

• Enriched grains

• Beef, chicken, turkey, fish

• Heat stable; little cooking loss

• 60mg tryptophan can be converted into 1 mg niacin

RDA for Niacin

• 14 (mg) NE/day for women

• 16 (mg) NE/day for men

• Upper Level is 35 mg

• Toxicity S/S: headache, itching, flushing, liver and GI damage

• Megadose can lower LDL and TG and increase HDL

Pantothenic Acid

• Part of Coenzyme-A• Essential for metabolism of CHO, fat,

protein

• Deficiency rare• Usually in combination with other

deficiencies

Food Sources of Pantothenic acid

• “From every side”• Meat• Milk• Mushroom• Liver• Peanut• Adequate Intake = 5 mg/day• Average intake meets AI

Biotin

• Free and bound form

• Metabolism of CHO and fat

• Help break down certain amino acids

• DNA synthesis

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

• Deficiency rare

• No Upper Level for biotin

• Relatively nontoxic

Vitamin B-6

• Coenzyme

• Activate enzymes needed for metabolism of CHO, fat , protein

• Synthesize nonessential amino acid via transamination

• Synthesize neurotransmitters

• Synthesize hemoglobin and WBC

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

• Athletes may need more

• Alcohol destroys vitamin B6

B-6 As A Medicine?

• PMS– B-6 to increase the level of serotonin– Not a reliable treatment

• Carpal tunnel syndrome• Toxicity potential• Can lead to irreversible nerve damage with

> 200 mg/day• Upper Level set at 100 mg/day

Folate

• Coenzyme

• DNA synthesis– Anticancer drug methotrexate

• Homocysteine metabolism

• Neurotransmitter formation

Deficiency of Folate

• Similar signs and symptoms of vitamin B-12 deficiency

• Pregnant women

• Alcoholics

• Megaloblastic Anemia

Neural Tube Defects

• Spina bifida• Anencephaly• Importance of folate

before and during pregnancy

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

• (600 ug/day for pregnant women)

• Average intake below RDA

• FDA limits nonprescription supplements to 400 ug per tablet for non-pregnant adults

• OTC Prenatal supplement contains 800 ug

• Excess can mask vitamin B-12 deficiency

• Upper Level set at 1 mg

Vitamin B-12

• Role in folate metabolism

• Maintenance of the myelin sheaths

• RBC formation

• Pernicious anemia (associated with nerve degeneration and paralysis)

Therapy for Ineffective Absorption

• Many factors can disrupt this process

• Monthly injections of vitamin B-12

• Vitamin B-12 nasal gel

• Megadoses of vitamin B-12 to allow for passive diffusion

Deficiency of Vitamin B-12• Pernicious anemia

– Never degeneration, weakness

– Tingling/numbness in the extremities (parasthesia)

– Paralysis and death

– Looks like folate deficiency

• Usually due to decreased absorption ability

• Injection of B-12 needed

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

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

• Synthesized by most animals (not by human & monkeys)

• Decrease absorption with high intakes• Excess excreted

Functions of Vitamin C

• Reducing agent (antioxidant)• Iron absorption• Synthesis of collagen• Immune functions

Antioxidant

• Can donate and accept hydrogen atoms readily

• Water-soluble• Needs are higher for smokers

Deficiency of Vitamin C

• Scurvy– Deficient for 20-40 days – Fatigue, pinpoint hemorrhages– Bleeding gums and joints. Hemorrhages– Associated with poverty

• Rebound scurvy– immediate halt to excess vitamin C supplements

Food Sources of Vitamin C

• Citrus fruit• Potato• Green pepper• Cauliflower• Broccoli• Strawberry• 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

Cancer

• Many diseases

• Formation of tumors (neoplasms)– Benign– Malignant

• Metastasize– Spreading of cancer

Type of Cancers

• Carcinomas– Cells that cover the body, including the secretory

organs

• Sarcomas– Connective tissues and bones

• Leukemias– Blood forming tissues

• Lymphomas– Lymph nodes or lymphoid tissues

Carcinogenesis

• Cancer initiation

• Cancer promotion

• Cancer progression

Cancer Initiation, Promotion, and Progression

Cancer Initiation

• Exposure to carcinogen

• Alteration of DNA (mutation)

• Is relatively short

• Tumor suppressor attempts to prevent the growth

Cancer Promotion

• May last for months or years

• Damage is “locked” in DNA

• Cell division increases– Promoters: estrogen, alcohol, maybe dietary fat

• Decrease time available for repair

Cancer Progression

• Final stage• Cancer cells proliferate and form a mass• Invade surrounding tissue• Metastasize to other tissues• Heredity can only explain a small

percentage of cancers• Environment contribute to most of the

cancer

Role of Diet• Excessive intake of calories increases the risk of cancer• Excessive body fat affect sex hormone production• High intake of fruits and vegetables is associated with

lower risk• High intake of meats and protein is associated with

higher risk• Excessive alcohol increases the risk• Excessive charcoal broiling increases risk• Nitrosamines (from nitrite) increases risk• Mycotoxins (from fungi) increases risk

Fat and Cancer

• The National Academy of Sciences recommend 30% of total calories from fat

• Effects of the type of fat to cancer

• There are still wide gaps in knowledge linking fat and cancer

• Excessive intake is a more likely cause

Recommendations to Reduce the Risk for Cancer

• Remain physically active• Avoid obesity• Engage in physical training that promotes lean

muscle mass• Consume abundance of fruits and vegetables• Consume plenty of low-fat/nonfat dairy products• Avoid high intakes of red meat and animal fat• Avoid excessive alcohol

Warning Signs

• Early detection is critical• Unexplained weight loss• A change in bowel or bladder habits• A sore that does not heal• Unusual bleeding or discharge• A thickening or lump in the breast or elsewhere• Indigestion or difficulty in swallowing• An obvious change in a wart or a mole• A nagging cough or hoarseness