Chapter 7 Vitamins

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Key Concepts

Vitamins are noncaloric essential nutrients that are necessary in very small amounts for specific metabolic control and disease prevention

Certain health problems are related to inadequate or excessive vitamin intake

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Key Concepts

Vitamins occur in a wide variety of foods that are packaged with the energy- and tissue-building macronutrients (CHO, fat, and protein)

The body uses vitamins to make coenzymes required for some specific enzymes to function

Vitamin supplementation needs depend on a person’s vitamin status

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Objectives

Describe what vitamins do in the human body

Identify: the nature of vitaminsthe fat soluble vitaminsthe water soluble vitaminsthe B – Complex vitaminsfood sources of vitamins

Describe the issue of vitamin supplementation

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Dietary Reference Intake: DRI

4 interconnected categories of recommendations:

The Recommended Dietary Allowance (RDA)- The daily intake that meets the needs of almost all healthy individuals in a specific group

Estimated Average Requirements (EAR) – Basis for developing the RDA “the intake that meets the needs of half of the individuals in a reference population

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Dietary Reference Intake: DRI

4 Interconnected categories (cont’d)

Adequate Intake (AI) – Guidelines used when not enough scientific evidence available to establish an RDA

Tolerable Upper Intake Level – New guideline that sets the maximum intake of a nutrient that is unlikely to pose a risk of toxicity in healthy individuals

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The Nature of Vitamins

Early observations: Vitamins were discovered during the search for cures for classic diseases that were initially thought to be associated with dietary deficiencies

1753- British Naval surgeon Dr. James Lind observed that on long voyages, when sailors were forced to live on very limited rations because no fresh foods were available, many of them became ill and died. When Lind gave some fresh lemons and limes, no one became ill. This vital clue led to the discovery that “scurvy” was caused by a dietary deficiency

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History of vitamin discovery

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The Nature of Vitamins

Vitamin Discovery cont.

Early Animal Experiments: Dr. Frederich Hopkins of Cambridge University fed a group of rats a diet of a synthetic mixture of protein, fat, CHO, mineral salts and water. All of the animals became ill and died. When he added milk to the purified ration, all of the rats grew normally discovery: accessory factors present in natural foods that are essential for life

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The Nature of Vitamins

Vitamin Discovery cont.

Most of the vitamins now known were discovered during the first half of the 1900s.

1911 – Casimir Funk, a Polish chemist, discovered a nitrogen-containing substance called amine which he thought was the chemical nature of these vital agents. So he called it “vitamine”

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Definition: VitaminMust be organic, dietary substance

that is not a carbohydrate, fat, protein, or mineral and is necessary in extremely small amounts to perform a specific metabolic function or prevent an associated deficiency disease

Must perform a vital functionIt cannot be manufactured by the

body in sufficient quantities to sustain life - it must be supplied by the diet

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Functions of Vitamins

General Functions:1. Components of coenzymes

2. Antioxidants3. Hormones that affect gene expression

4. Cell membrane component

5. Component of light-sensitive rhodopsin molecule in eyes

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Functions of vitamins

Control agent to cell metabolism – Enzymes and coenzymes control specific chemical reactions by acting as necessary catalysts – e.g. B vitamins thiamin, niacin, and riboflavin help turn glucose to energy.

Component of body tissue construction – Vit C helps synthesize collagen- Also act as antioxidants to protect cell structure and prevent free radical damage

Prevent specific nutritional deficiency disease – e.g. scurvy due to lack of vit C

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Vitamin Metabolism

Fat-Soluble Vitamins:A,D,E,KDependant upon fat for absorption

and transport -incorporated into lipoproteins along with dietary fat- Then enter lymphatic system for circulation – stored for long periods of time in liver and adipose tissue

Absorbed in the GI tractExcess intake can result in toxicity

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Vitamin Metabolism

Water-Soluble Vitamins:Vit C and most of B vitamins Easily absorbed directly into the blood circulation from GI tract

Does not need a carrierWith the exception of B12 & B6 body does not store water soluble vitamins- need foods rich in water-soluble vitamins daily

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Fat-Soluble Vitamins

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Vitamin A (Retinol)Functions

VisionMajor function in the retina of eye. Retinol is a part of rhodopsin, that is the pigment in the eye known as visual purple

Enables the eye to adjust to different amounts of available light.

Maintenance of vision in dim light. Maintenance of vision in dim light. Mild deficiency night blindness

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Vitamin A (Retinol)Function cont.

Tissue strength and immunity Maintains epithelial tissue Primary barrier to infection- the vital protective tissue covering the body (skin) and the mucous membranes in the nose, throat, eyes, GI tract, and GU tract

Growth of skeletal and soft tissueInfluences the stability of cell membranes and protein synthesis

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Vitamin ARequirements = 700ug women and 900ug for

menFood forms and units of measure:Vitamin A occurs in 2 forms:

Preformed Vit A or RetinolThe ‘active’ vitamin A found in foods derived from animals

Beta-Carotenea pigment in yellow and green foods that the body converts to Vit. A

Body storage – liver can store large amounts of retinol

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Vitamin AFood sources – Page 99 (Table 7-1)

Fish liver oils, egg yolks, butter, cream, fat part of milk; dark leafy greens, orange veggies and fruits

Stability – Retinol is unstable in heat and in contact with air. Cook quickly with little water.

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Vitamin A foods

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Vitamin AVitamin A : Deficiency

disease Xerosis – itching and

burning and red inflamed lids

Xerophthalmia –blindness

Note: Vitamin A deficiency is the number one cause of blindness in children world wide

Epithelial Disorders and compromised immune system

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Vitamin AToxicity symptoms – (Hypervitaminosis A)

joint pain thickening of long bones loss of hair jaundice, liver injury which could result in

elevated blood pressure (portal hypertension) or swelling or fluid accumulation in the abdominal cavity (ascites)

UL = 3000 mcg / dayToxicity usually results from the Preformed

Vit A and not beta-Carotene sources23

Vitamin D (Cholecalciferol)Functions

Not a true vitamin because made in our own bodies with the help of the sun’s ultraviolet rays.

Mistakenly classified as a vitamin by its discoverers in 1922, because they were able to cure the childhood deficiency disease, rickets, with its only known natural form in fish liver oils.

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Vitamin D (Cholecalciferol)Function cont.

The compound made in our skin by sunlight is actually a “prohormone” – a fat-soluble sterol (cholecalciferol/calciferol) that controls calcium metabolism in bone building

Calciferol is then activated by 2 enzymes to become the active Vitamin D hormone form called calcitriol that functions in the body.

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Vitamin D (Cholecalciferol)

Calcitriol performs the following functions:Acts physiologically with the parathyroid hormone (PTH) and the thyroid hormone calcitonin.

In balance with these 2 hormones, the Vitamin D hormone (calcitriol) stimulates the absorption of calcium and phosphorus in the small intestine

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Vitamin DBone mineralization – Vit D (calcitriol) works with calcium and phosphorus to form bone tissue, regulating the rate of deposit and resorption of these minerals in bone. Clinically used to tx. osteoporosis

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Vitamin DRequirements:

Difficult to establish an RDA because:1. made in the skin by the sun’s UV rays2. food sources are limited3. Vit D requirements vary with individuals exposure to sunlight which is affected by season, latitude, and skin color

Adequate Intake is 600 IU/ day UL upper limit is 4,000 IU/dayRecommendation: triple dose for persons 70+ years old

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Vitamin DFood sources: Only fish liver oils

and yeast are natural sourcesFoods fortified with Vitamin D

Stability: Vit D is stable to heat, aging and storage

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Vitamin DDeficiency disease

Rickets – Malformation of skeletal tissue in growing children- Soft bones will bend with the weight of the child

Poorly developed teeth and boneToxicity symptoms-

Hypervitaminosis DCalcification of soft tissue in kidneys and lungsFragile bones

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Vitamin E (Tocopherol)History

Early vitamin studies identified a substance necessary for animal reproduction that was chemically in alcohol

This “substance” was named “tocopherol” –

Gk. – “tophos” meaning childbirth

“phero” meaning “to bring”

“ol” from alcohol

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Vitamin E (Tocopherol)

Fat –soluble3 forms display the most biological activity: alphatocopherol, betatocopherol, gammatocopherol.

Of these three, alphatocopherol is the most significant in human nutrition and is used for measuring dietary needs

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Vitamin E (Tocopherol)

Functions:Antioxidant function – A molecule that prevents cellular structure from being broken down by oxygen (the process of oxidation)

Relation to selenium metabolism – Selenium is a trace mineral that works as a partner to help the antioxidant function

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Vitamin E (Tocopherol)Function cont.

Requirements- Expressed in terms of alpha-tocopherol in mg./day. Men and women age 14 years + : 15mg/day

UL = 1000mg/dayFood sources – vegetable oils: wheat

germ, soybean, safflower oil: nuts, fortified cereals, and avocados

Stability- stable to heat and acids but not to alkalis (Table 7-3 p. 101)

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Vitamin E foods

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Vitamin EDeficiency Disease Hemolytic Anemia –

preemies: infants who miss the final 1-2 months of gestation when tocopherol stores are normally built up, are vulnerable to hemolytic anemia – the lipid membranes of RBCs are easily oxidized by oxygen and the continued loss of RBCs leads to anemia

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Vitamin EDeficiency Disease cont.

Decreased myelin synthesis – In older children and adults, a deficiency of tocopherol disrupts normal synthesis of myelin, the protective fat covering of nerve cells that helps them pass messages along to specific tissues. The main nerves involved are: 1) spinal cord fibers that affect physical activity (eg. walking) and 2) the retina of the eye that affects vision

Toxicity symptoms – no toxicity from food source; mega doses of supplemental tocopherol may interfere with Vitamin K activity and blood clottingUL 1000 mg/day

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Vitamin KHistory: Henrik Dam, a biochemist at the

University of Copenhagen, discovered a hemorrhagic disease in chicks that were fed a fat –free diet

He determined that the factor responsible was the absence of a fat-soluble, blood-clotting vitamin that he called “koagulationsvitamin”, or Vitamin K

Several forms of Vitamin K compose a group of substances with similar biologic activity in blood clotting. The major form found in plants, is named “phylloquinone” .

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Vitamin K

Phylloquinone is our dietary form of Vitamin K

Menaquinone:synthesized by intestinal bacteria

Contributes about ½ of our daily supply of Vit K

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Vitamin K functionsBlood clotting -The basic function of Vit K is

in the blood clotting process.The most familiar of these Vitamin K-dependent blood factors is Prothrombin. Thus phylloquinone can serve as an antidote for the excess effects of anticoagulant drugs.

Used in the control and prevention of certain types of hemorrhages.

Bone development – specific proteins in bone and bone matrix are dependent on Vitamin K for their synthesis and are involved with calcium in bone development

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Vitamin KRequirements :

AI value 120 ug/day men and 90 ug/day for women

Gradual increase from birth-adulthood

Food sources: green leafy vegetables, spinach, turnip greens, broccoli

(note: a diet assessment should be made when a person is started on anticoagulation therapy to help determine therapeutic dose. Also, ongoing intermittent evaluation of diet when concern arises about therapeutic control or stability.)

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Vitamin KDeficiency disease:

Uncommon except in clinical conditions related to blood clotting, malabsorption, or lack of intestinal bacteria to synthesize the vitamin E.g. Vitamin K shot given to newborns to prevent hemorrhage from the cutting of the umbilical cord

(a newborn’s intestine is sterile at birth)

Toxicity symptoms – none knownNo UL exists

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Water-Soluble Vitamins

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Vitamin C (ascorbic acid)Functions – Vitamin C acts as a protective agent

(antioxidant), and enzyme cofactor, and plays a role in many metabolic and immunologic activities.Connective tissue – needed to build and maintain strong tissue by involvement with collagen synthesis – esp. bone, cartilage, tooth dentin, and strong capillary walls in blood vessels

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Vitamin C (ascorbic acid)General body metabolism – a greater concentration of ascorbic acid in the more metabolically active tissues such as adrenal glands, brain, kidneys, liver, pancreas, thymus, and spleen. Also helps in the absorption of iron, and for clinical needs such as wound healing, fevers, infection, and growth periods

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Vitamin C foods

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Vitamin C

Antioxidant function – Vit C protects from free radical damage which is associated with increased risk of cancer and heart disease. May prevent the development of chronic disease

Requirements : (RDA)Men (18 years +) 90 mg/dayWomen (18 years +) 75 mg./daySmokers – increase by 35mg/dayIncreased needs during pregnancy and

lactationUL = 2000mg /day

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Vitamin C

Stability – oxidizes to air and heat.

Not stable in alkaline substances such as baking soda which destroys the ascorbic acid content.

When extra water is added to cook with, vitamin C leaches out into the water.

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Vitamin CS/S ascorbic acid deficiency are:

Tissue bleeding (easy bruising, pinpoint skin hemorrhages, etc.)

Bone and joint bleedingPoor wound healingEasy bone fxSoft bleeding gums with loosened teeth

Extreme deficiency produces scurvy: a hemorrhagic disease characterized by bleeding in joints, other tissues, & breakdown of fragile capilaries

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Vitamin CToxicity symptoms –

excessive levels may cause diarrhea; kidneys will usually excrete excess Vit C

Food sources – Citrus fruit, tomatoes, cabbage and other leafy vegetables; berries, melons, broccoli, potatoes, and other green and yellow veg., green and red bell peppers, kiwi

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Vitamin C deficiency

Scurvy teeth Petechiae

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Thiamin (Vitamin B1)Thiamin is a coenzyme

factor that relates to the production of energy from glucose and the storage of energy as fat

Especially necessary to maintain 3 body systems:Gastrointestinal system-

lack of poor appetite, indigestion, constipation, poor stomach function and decrease HCL secretion

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Thiamin (Vitamin B1)Nervous system – Depends on glucose for energy. Without sufficient thiamin inability of nerves to do their work -> decreased alertness, decreased reflex response, apathy, fatigue, and irritability.

Cardiovascular system – Without constant energy ->Heart muscle weakens -> heart failure; circulation becomes a problem, and fluid accumulation in the lower part of the legs

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Thiamin (Vitamin B1)Requirements are directly related to energy and

CHO metabolism:For healthy persons: RDA for 18yrs. +

Men 1.2 mg Women 1.1 mgIncrease need during pregnancy and lactation;

when treating infection, and alcoholismNo UL

Food sources – Pork, Beef, Liver, Whole or enriched grains, legumes, wheat germ, eggs, fish

Stability- Fairly stable but is destroyed by alkalis and prolonged heat

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Vitamin B1 ThiaminDeficiency disease:

Beriberi – a paralyzing diseaseAssociated with chronic ETOH abuse and poor dietAlcohol inhibits the absorption of ThiaminWernicke’s encephalopathy: a disease affecting mental alertness and coordination

Toxicity symptoms – No evidence of toxicity from oral intakeKidneys clear excess

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Vitamin B1 Thiamin deficiency

Beriberi

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Riboflavin (Vitamin B2)

“Riboflavin” comes from the Latin word “Flavus” meaning yellow; and “ribose”, a sugar A yellow-green fluorescent pigment

Functions – Vital coenzyme factor in both energy production and tissue protein building

Requirements: RDA 18 yrs. + Men 1.3 mg Women 1.1 mg Increase during pregnancy and lactation

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Riboflavin (Vitamin B2)

Food sourcesMilk and milk products, meat, enriched cereals, green vegetables

Stability Destroyed by light, milk is now sold in plastic or cardboard cartons instead of glass containers

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Riboflavin (Vitamin B2)Deficiency disease

rarely occurs alone; usually occurs with a deficiency of other B vitamins and protein.

Cracked lips, mouthSwollen tongueEyes burning, itching, or tearing from extra blood vessels in the cornea

Scaly, greasy dermatitis in skin folds

Toxicity symptoms – None known; no UL60

Niacin (Vitamin B3)

Functions Coenzyme role: partners with riboflavin and thiamin to help in the cell -metabolism system that produces energy

A necessary part of important chemical reactions involved in DNA repair and calcium mobilization in the body

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Niacin (Vitamin B3)

RequirementsExpressed in terms of “niacin equivalents”

(NE). Because the body can make some of its

niacin from the essential amino acid tryptophan, the total niacin requirement is stated in terms of “niacin equivalent”.

60mg tryptophan = 1mg niacin = 1NERDA :

for adults age 14 yrs. +: Men 16 mg NE and women 14 mg NE per day

Increase dose during pregnancy and lactation 62

Niacin (Vitamin B3)Deficiency disease:

Pellegra: dermatitis, diarrhea, dementia, death

corrected with supplemental NiacinOther s/s of general niacin deficiency:

Weakness, poor appetite, indigestion, skin and nervous system disorders

Extended deficiency may result in CNS damage with resulting confusion, apathy, disorientation, and neuritis. Such CNS s/s seen in chronic alcoholism

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Niacin deficiency

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Niacin (Vitamin B3)Toxicity symptoms –

excessive supplementation can cause reddened skin with burning, itching, and tinglingUL 35mg/day

Food sources – Meat (Most common source), peanuts, legumes, enriched grain

Stability – Stable to acid and heat; lost when cooked with excess water

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Vitamin B6

Vitamin B6 is the collective name of a group of six related compounds.

Known also as “pyridoxine”Function:

protein metabolism and cell reactions involving amino acids

Aids neurotransmitter synthesis for brain activity and CNS function

As a coenzyme it is active in CHO and fat metabolism

Extensively stored in tissues throughout the body – particularly muscle

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Vitamin B6 (Pyridoxine)Requirements : RDA up to 50 years old:

Men and women - 1.3 mg / dayOlder adults: men 1.7 mg/day; women 1.5mg/day

Increased need during pregnancy and lactation

UL 100m/dayDeficiency disease – Abnormal CNS, hyperirritability, neuritis, and possible convulsions and certain types of anemia

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Vitamin B6 (Pyridoxine)Toxicity symptoms –

large supplemental doses can cause lack of muscle coordination and nerve damage

Food sources – Grains, enriched cereals, liver and kidney and other meats.

Stability – Stable to heat but sensitive to light and alkalis

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FolateFolate – from Latin “folium” meaning “leaf”; was

used because a major source for it was in dark green leafy vegetables

Chemical form: folic acidFunctions – a coenzyme which is used in:

the formation of body cells and creation of DNAThe formation of hemoglobin and synthesis of

amino acidsAdequate amt reduces neural tubal defects in

the unbornRequirements - RDA age 14 yrs. + = 400 ug of

DFE (dietary folate equivalent) per dayUL 1000 mcg/day

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FolateDeficiency disease

Megaloblastic anemia (esp. during pregnancy, and rapidly growing adolescents esp. ones following fad diets or those who smoke)

Neural tubal defects in unborn infant if maternal intake is inadequate

Toxicity symptoms – none noted from excessive intake of folate from foods. Some evidence that excess intake of folate from supplements may have toxic effects.

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Folate deficiency – neural tube defect

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FolateFood sources –

chicken and beef liver, dark green leafy vegetables, legumes, yeast, orange juice, fortified grains

Stability – easily destroyed by heat and leaches into cooking water

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Cobalamin Vitamin B12Functions:

Normal blood formation and synthesis of the heme portion of hemoglobin

Essential for proper nervous system function

Requirements:RDA 19yrs.+ for men and women = 2.4 ug/day

Increased need during pregnancy Older than 50, some have trouble absorbing Vitamin B12.

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Cobalamin Vitamin B12

Deficiency disease:Pernicious anemia – reduced secretion of “ intrinsic factor” that comes from the cells lining the stomach ->poor absorption of Vit B12.

Nervous disorders, sore mouth and tongue, amenorrhea, and neuritis

Toxicity symptoms – none knownFood sources – Beef/chicken livers, lean

meat, clams, oysters, herring, crabStability – Stable in ordinary cooking

process74

Cobalamin Vitamin B12

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Pantothenic AcidFunctions :In its coenzyme role, it is essential to the

synthesis and functioning of coenzyme A which controls many cell metabolic reactions involving fat and cholesterol, heme formation and amino acid activation

Requirements - No RDA; AI = 5 mg/day for 14yrs +

Deficiency disease – unlikely. The only cases are people fed synthetic diets with virtually no pantothenic acid

Toxicity symptoms – none; excreted in urineFood sources – Meat, eggs, milk, whole grains,

legumes and vegetablesStability – Stable to acid and heat but sensitive to

alkalis76

BiotinFunctions – Partners with co enzyme A; also

involved with synthesis of fatty acids and amino acids

Requirements – no RDA; AI 30 ug/day in persons 18yrs. +

Deficiency disease – no known natural deficiency; induced deficiency may occur in patients on TPN without biotin supplementation; occasional inborn errors of metabolism r/t biotin

Toxicity symptoms – none knownFood sources – cornmeal, soy meal (flour),

liver, egg yolk, cereals that aren’t wheat based, meat, tomatoes, and yeast

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Biotin foods

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CholineFunctions:A water-soluble nutrient associated with B-Complex Vitamin

Helps maintain the structural integrity of cell membranes

Insufficient data to determine whether essential to human diet

Active in the synthesis of acetylcholine which is a neurotransmitter involved with memory storage, muscle control, and other functions

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CholineRequirements :

No RDA; AI = for persons over 18yrs: Men: 550mg/day; Women: 425mg/day

UL 3.5g/dayDeficiency disease – Liver damage

Toxicity symptoms - low blood pressure, fishy body odor, sweating, increased salivation, and reduced growth rate

Food sources – Milk, eggs, liver, peanuts80

Phytochemicals

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PhytochemicalsPlant compoundsBioactive molecules

with health benefitsA nutrient but not a

vitamin or mineral Research believes that

there are 25,000 of these phytochemicals found in fruit and vegetables

Act as either antioxidant or hormone

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PhytochemicalsFunction:

Diets high in phytochemicals induce a protective lipid profile to protect against coronary heart disease, improve overall colon function, help prevent age-related macular degeneration and cancer, and increase the body’s antioxidant status

Multiple studies are exploring the possible link between increased intake of phytochemical and reduced risk of developing chronic disease

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PhytochemicalsRecommended intake –

A dietary intake of 400-600g/day of fruits and vegetables reduces one’s risk of various forms of cancer

Food sources: Color categories:Red foods – lycopeneYellow green – zeaxanthinRed purple – anthocyaninsOrange – beta caroteneOrange yellow – flavonoidsGreen – glucosinolatesWhite green - allyl sulfides

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Phytochemicals

Red foods – lycopene Yellow green – zeaxanthin

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PhytochemicalsRed purple – anthocyanins

Orange – beta carotene

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PhytochemicalsOrange yellow – flavonoids

Green – glucosinolates

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Phytochemicals

White green - allyl sulfides

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Food Sources cont.

By consuming one fruit or vegetable from each of the 7 color categories daily, can meet you dietary recommendation.

Grains, soybeans, legumes, and nuts also contain phytochemicals

Vitamin Supplementation

Ongoing debate – Most commonly bought over the counter item in America

Biochemical individuality - The body’s chemical composition is not the same for everyone.

Everyone is different and has different needs.

This pattern chances within a given person at different times, under different circumstances during normal life-cycle and with disease.

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Vitamin SupplementationIndividual approach based on

needs assessment:Life cycle needs

Pregnancy and lactation- Folic acid to prevent birth defects

Infancy- Vit D, K, Iron (Fe) and Fluoride

Children and adolescents – Multi vitamin for rapid growth period

Aging- decrease food intake and impaired nutrient absorption

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Lifestyle needs: choices and habits influence the need for supplementsOral contraceptive use – reduces serum

levels of several B vitamins and Vit CRestricted diets – E.g. a wise weight-

reduction program should meet all nutritional needs. E.g. A strict vegan diet may need Vit B12 supplementation

Smoking – need Vit C

Vitamin supplementationExercise programs –

Need more riboflavinAlcohol – Chronic or

abusive use of alcohol can interfere with absorption of B-complex vitamins; esp. Thiamin and may destroy folate

Caffeine – in large quantities, it flushes water-soluble vitamins out of the body faster than usual

Disease states – require careful nutritional assessment

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MegadosesPersons taking megadoses of vitamins are

using them as a drug for therapeutic treatment; no longer operating as a nutritional agent

Toxic effects: (in megadoses)Fat-soluble vitamins are stored in the liver

and may lead to liver and brain damageB6 – nerve damage and reduced muscular

coordination Vit C – may cause GI pain, increase the

risk for kidney stones; reduce the action of leukocytes against bacteria

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Megadoses“Artificially induced” deficiencies: above-

normal blood levels of one nutrient may increase the need for the other nutrients with which it works in the body, creating deficiency symptoms.

Deficiencies may also occur when a person suddenly stops taking the large amounts and a “rebound effect” results.E.g. infants born to mothers who took

megadoses of ascorbic acid during pregnancy have developed scurvy when their high nutrient supply was cut off at birth

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Supplementation Principles

Read labels carefullyVitamins can be harmful in large amountsProfessionally determined individual

needs govern specific supplement useAll nutrients work together to promote

good healthFood is the best source of nutrientsEvaluate the information for safety and

efficacy of nutrition supplementation

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