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The Vitamins

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Vitamins

Organic, essential nutrients required in minute amounts to perform specific functions that promote growth, reproduction, or the maintenance of health and life

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Bioavailability

The availability of vitamins from food depends on two factors:

The quantity provided from a food

The bioavailability of the vitamin from that food

Bioavailability refers to the rate and extent to which a nutrient is absorbed.

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Vitamins As Precursors Or Provitamins

Some vitamins occur in foods in inactive forms.

Once in the body they are changed chemically to an active form of the vitamin.

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Solubility

Apparent in the different food sources of the vitamins

Affects their absorption, transport, and excretion by the body

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Water Soluble Versus Fat Soluble Vitamins

Water SolubleThiamin- B1

Riboflavin- B2

Niacin- B3

BiotinPantothenic AcidVitamin B6

FolateVitamin B12

Vitamin C

Fat SolubleVitamin AVitamin DVitamin EVitamin K

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Water FatSoluble Soluble

Absorption Directly into blood First into lymph, then the blood

Transport Travel freely May require protein carriers

Storage Circulate freely in water filled body compartments

Trapped in the cells associated with fat

Excretion Kidneys detect and remove excess

Tend to remain in fat cells

Toxicity Possible to reach toxic level from supplements

Likely to reach toxic level from supplements

Requirements Needed in frequent doses

Needed in periodic doses

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Thiamin- B1

Part of coenzyme thiamin pyrophosphate (TPP) which assists in energy metabolism

Recommended intake is 1.2 mg/day and 1.1mg/day for adult men and women, respectively.

Best sources of thiamine are pork, liver, sunflower seeds, legumes, whole grain and enriched breads and cereals.

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Thiamine Deficiency

Prolonged deficiency is known as Beriberi.

First recognized in East Asia where rice comprises ~80% of their diet. They began “polishing” the rice which is removal of the hull. Rice hulls were the principal source of thiamine.

Characterized by edema (wet beriberi) or wasting (dry beriberi), enlarged heart, muscle weakness, loss of appetite, mental confusion, paralysis.

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Thiamine Toxicity

None noted

Cannot occur from food sources

May occur with supplementation, however excess is readily excreted in the urine

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Riboflavin- B2

Part of coenzyme flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD) used in energy metabolism

Supports normal vision and skin health

Recommended intake is 1.3 mg/day and 1.1 mg/day for adult men and women, respectively.

Best food sources are milk, yogurt, cottage cheese, meat, whole grain and enriched breads and cereals.

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Riboflavin Deficiency

Deficiency of riboflavin is referred to as ariboflavinosis.

Characterized by angular cheilosis, glossitis, photophobia, and inflamed, scaly skin lesions

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Riboflavin Toxicity

None noted

Cannot occur from food sources

May occur with supplementation, however excess is readily excreted in the urine

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Niacin- B3

Part of the coenzyme nicotinamide adenine dinucleotide (NAD) used in energy metabolism

Supports the health of skin, nervous system, and digestive system

Recommended intake is 16 mg NE/day and 14 mg NE/day for adult men and women, respectively.

Best food sources are milk, eggs, meat, poultry, fish, whole grain and enriched breads and cereals.

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Niacin Deficiency

Deficiency of niacin is known as Pellegra.

Characterized by vomiting, diarrhea, glossitis, fatigue, memory loss, bilateral symmetrical dermatitis.

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Niacin Toxicity“Niacin flush”- a burning, tingling, itching

sensation that occurs when a person takes large doses of nicotinic acid.

Can effectively lower blood cholesterol but such therapy needs close monitoring because of its adverse side effects.

Common toxicity symptoms include nausea, diarrhea, vomiting, peptic ulcers, headache, fatigue, low blood pressure, and liver damage.

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BiotinFunctions as a coenzyme in the metabolism

of carbohydrates and fats

Biotin is needed in very small amounts. Instead of an RDA, an Adequate Intake (AI) has been established at 30 μg/day for both adult men and women.

Biotin is widespread in foods, however, the best sources are organ meats, soybeans, fish, and whole grains.

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Biotin Deficiency

Deficiency is uncommon.

Symptoms include loss of appetite, nausea, depression, lethargy, hallucinations, muscle pain, weakness, fatigue, dry scaly dermatitis, and hair loss.

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Pantothenic Acid

Involved in more than 100 different steps in the synthesis of lipids, neurotransmitters, steroid hormones, and hemoglobin

The principal active form is part of coenzyme A called “CoA”.

CoA is involved in several metabolic pathways.

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Pantothenic Acid {continued}

An AI for pantothenic acid has been set at 5mg/day to replace daily losses.

Pantothenic acid is widespread in foods, however the best sources are organ meats, mushrooms, broccoli, and whole grains.

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Pantothenic Acid Deficiency

Deficiency is uncommon.

Characterized by nausea, vomiting, stomach cramps, insomnia, fatigue, and depression

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Vitamin B6- Pyroxidine

Part of coenzymes important in amino acid and fatty acid metabolism

Helps convert tryptophan to niacin and serotonin

Helps make red blood cells

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Vitamin B6- Pyroxidine {continued}

Recommended intake is 1.3 mg/day for both adult men and women.

Best food sources are green leafy vegetables, meats, fish, poultry, shellfish, and legumes.

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Vitamin B6- Pyroxidine Deficiency

Deficiency is uncommon.

Characterized by small cell type anemia, glossitis, angular cheilosis, insomnia, irritability, muscle twitching, convulsions, scaly dermatitis, and kidney stones.

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Vitamin B6- Pyroxidine Toxicity

Toxicity is uncommon.

First appeared in 1983 in people taking greater than two grams per day for two months or more

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Folate

Functions as coenzyme used in DNA synthesis and therefore is important in cell formation

Folate prevents neural tube defects in the growing fetus. The brain and spinal cord develop from the neural tube in the early weeks of gestation.

Neural tube defect- malformations of the brain, spinal cord or both during embryonic development.

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Folate {continued}

Recommended intake is 400 μg/day for both adult men and women.

Best food sources are green leafy vegetables, legumes, seeds, and liver.

There is growing evidence that folate plays a role in preventing heart disease by decreasing homo-cysteine levels. Elevated homocysteine is associated with increased risk of developing heart disease.

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Folate Deficiency

Characterized by a large cell type of anemia, heartburn, diarrhea or constipation, immune system suppression, glossitis, mental confusion, weakness, fatigue, irritability, and insomnia.

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Vitamin B12

Characterized by the presence of cobalt

The active forms of coenzyme B12 are methylcobalamin and deoxyadenosyl-cobalamin.

Works closely with folate, thus also playing a role in the prevention of heart disease

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Vitamin B12 {continued}

Recommended intake is 2.4 μg/day for both adult men and women.

Only found in animal products

Best food sources are meat, fish, poultry, shellfish, milk, cheese, and eggs.

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Vitamin B12 DeficiencyB12 gets absorbed by attaching to a glygoprotein in

the stomach known as the intrinsic factor (IF).

Pernicious anemia is due to lack of or ineffective IF.

It is characterized by a large cell type anemia and memory loss.

A deficiency can also occur from inadequate dietary intake.

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Vitamin Ccollagen synthesis

antioxidant properties

thyroxin synthesis

amino acid metabolism

immune system booster

aides in the absorption of iron

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Vitamin C {continued}

Recommended intakes are 60 mg/day for both adult men and women, 100 mg/day for pregnant women and smokers.

Best food sources are citrus fruits, dark green vegetables, cantaloupe, strawberries, peppers, and tomatoes.

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Vitamin C Deficiency

Referred to as Scurvy.

Characterized by small cell type anemia, pinpoint hemorrhages, immune system suppression, bleeding gums, loose teeth, muscle pain, joint pain, and poor wound healing.

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Vitamin C Toxicity

Cannot occur from food sources

May occur with supplementation, however, excess is readily excreted in the urine

Characterized by nausea, diarrhea, abdominal cramps, headache, fatigue, and rashes

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Vitamin A

Three active forms in the body: retinol, retinal, and retinoic acid, collectively known as the retinoids.

Promotes vision

Participates in protein synthesis and cell differentiation

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Vitamin A {continued}

Supports reproduction and growth

Recommended intake is 1000 μg and 800 μg retinol equivalents (RE) per day for adult men and women, respectively.

Best food sources of preformed vitamin A are foods of animal origin such as liver, fish, milk and milk products, butter, and eggs.

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Vitamin A DeficiencyDeficiency takes one to two years to develop after

vitamin A intake has been stopped due to the body’s effective storage of fat soluble vitamins.

Characterized at first by night blindness, but if left untreated can cause xeropthalmia or keratomalacia

Xeropthalmia- progressive blindness caused by vitamin A deficiency.

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Vitamin A Deficiency

Keratomalacia- softening of the cornea seen in severe vitamin A deficiency that leads to irreversible blindness.

Other symptoms include diarrhea, plugging of hair follicles with keratin forming white lumps, immune system suppression and kidney stones.

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Vitamin A ToxicityToxicity can occur when taking greater than ten

times the RDA.

Characterized by joint pain, headaches, dry, itchy, peeling skin, jaundice, nose bleeds, hair loss, loss of appetite, insomnia, fatigue, blurred vision, nausea, and vomiting.

Can cause birth defects in pregnant women .

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Vitamin DSynthesized in the body with the help of

sunlight

Chief function is the mineralization of bones.

Recommended intake is 5 μg per day for both adult men and women, respectively.

Best food sources include milk, margarine, butter, cereals, veal, beef, and liver.

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Vitamin D Deficiency

Deficiency disease known as rickets in children and osteomalacia in adults.

Rickets- vitamin D deficiency disease seen in children characterized by inadequate mineralization of bone manifested in bowed legs or knock knees.

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Vitamin D Deficiency

Osteomalacia- a bone disease characterized by softening of the bones. Symptoms include bending of the spine and bowing of the legs, occuring most often in adult women.

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Vitamin D Toxicity

Likely to be toxic when consumed in amounts above the recommendations

Characterized by nausea, vomiting, increased blood calcium and phosphorus, loss of appetite, headache, muscle weakness, joint pain, excessive thirst, and irreversible kidney damage

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Vitamin EOne of the body’s primary antioxidants

Evidence suggests that vitamin E can reduce the risk of heart disease.

Recommended intake is 10 mg α TE and 8 mg α TE per day for adult men and women, respectively.

Best food sources are wheat germ oil, soybean oil, corn oil, and sunflower seeds.

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Vitamin E Deficiency

Deficiency is rare but may be encountered in cases of fat malabsorption.

Characterized by a hemolytic anemia

Prolonged deficiency can cause neuromuscular dysfunction, impaired vision and speech

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Vitamin E Toxicity

Toxicity is rare.

Can occur with supplementation

May interfere with the blood clotting action of vitamin K

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Vitamin K

Primary function is the synthesis of blood clotting proteins

Participates in the synthesis of bone proteins

Can be obtained from non food sources such as the bacteria in the GI, however, that can only meet 1/2 of a person’s needs.

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Vitamin K {continued}

Recommended intakes are 80 μg and 65 μg per day for adult men and women, respectively.

Best food sources are liver, leafy green vegetables, and cabbage like vegetables.

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Vitamin K Deficiency

Deficiency is rare but it may be encountered in cases of fat malabsorption, which would diminsh vitamin K absorption.

Antibiotics kill the vitamin K producing bacteria in the intestine.

Deficiency would be characterized by hemorrhaging.

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Vitamin K Toxicity

Toxicity is rare.

Can occur with supplementation

High dietary intakes of foods rich in vitamin K may interfere with anticoagulating medications.

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AntioxidantsA compound that protects others from oxidation

by being oxidized itself. An antioxidant donates electrons to another substance, that substance becomes reduced as the antioxidant simultaneously becomes oxidized.

“Free radical scavengers”

Free Radicals- atoms and molecules that have one or more unpaired electrons resulting in the high reactivity of free radicals.

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Antioxidants

Research has linked antioxidants as defenders against certain types of cancers and heart disease.