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Vitamins & Health: Lecture Notes on Nutrition

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LFS 131 – NUTRITION
SEM II- 2020-2021
Chapter 5 Vitamins
LEARNING OUTCOME 1
To verbalize the connections between vitamins and health maintenance.
Concepts for Lecture
1. The discovery of vitamins did not occur until the early 1900s when the B vitamins were
isolated; others soon followed.
2. Early research focused on food sources of vitamins and understanding the amount of
vitamin and nutrient intake needed by healthy individuals to prevent nutrient deficiencies.
These amounts are now called dietary reference intake (DRI).
3. The realization of potential toxicity of higher doses of vitamins required establishment of
a safe upper limit for vitamin intake, now included in the DRIs as a tolerable upper intake
limit (UL).
4. Nurses face the challenge of balancing advice about healthful amounts of vitamin intake
from food and supplements while keeping up-to-date on both positive and negative
effects of higher doses of vitamin intake.
5. Vitamins are organic compounds made up of molecules of elements such as hydrogen,
oxygen, carbon, and others.
6. Vitamins and minerals are referred to as micronutrients because only small amounts are
required by the body. The body can only synthesize sufficient amounts of most vitamins,
with the exception of vitamin D.
7. Vitamins play many different roles in the body:
• They are important components of many cellular activities in the body, including
metabolism, growth, and repair.
• Some vitamins act as cofactors or co-enzymes in metabolism; their presence is
essential for specific biochemical reactions to take place.
• Other vitamins act as antioxidants, preventing damage to cells from free radicals, the
byproducts of metabolism or environmental damage to cells.
• Vitamin D is considered to be hormone-like because it is activated in a different part
of the body than that where it exerts its action.
• Vitamins have been used as pharmaceutical agents, such as niacin being used to treat
certain types of hyperlipidemia.
8. DRIs outline recommendations for vitamin intake for healthy people. Some vitamins
have an established Recommended Dietary Allowance (RDA) when there is sufficient
scientific evidence to support a specific recommendation. Examples: vitamin A has an
RDA; vitamin D has an Adequate Intake (AI).
©2011 by Pearson Education, Inc. Tucker, Instructor’s Resource Manual for Nutrition and Diet Therapy for Nurses
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LEARNING OUTCOME 2
To summarize good dietary sources of water-soluble and fat-soluble vitamins.
Concepts for Lecture (done by students)
1. Vitamins are classified according to solubility in solutions.
• Fat-soluble vitamins are vitamins A, D, E, and K; they are soluble in fatty substances
or fatty tissue in the body.
• Water-soluble vitamins include vitamin C and all the B vitamins, sometimes referred
to as B complex vitamins: thiamin, riboflavin, niacin, folate; vitamins B-6 and B-12,
biotin, and panthothenic acid. Water-soluble vitamins dissolve in watery solutions in
the body. They are more prone to destruction from excessive heat, air, or light
exposure during food storage or cooking than are fat-soluble vitamins.
2. The type of solubility affects the way in which vitamins are absorbed, transported, and
stored in the body.
3. Vitamins are also classified as:
• provitamins—inactive form of the vitamin that requires conversion by the body to the
active form of the vitamin
• preformed vitamins—metabolically active form of the vitamin
4. Vitamin A—adequate intake is essential. Lack of vitamin A is a public health issue in
developing countries where food sources of Vitamin A are scarce. Chronically high
intake of Vitamin A is associated with impaired bone remodeling and potential risk of
fracture.
• Functions: vitamin A is critical in maintaining important functions in the body
including:
✓ Healthy vision; night vision requires retinol, the preformed version of vitamin A
✓ Bone growth
✓ Immune response: vitamin A participates in the maintenance of cells that participate
in the immune response
✓ Cell proliferation and differentiation; gene encoding and embryonic development
require vitamin A.
✓ Epithelial cell integrity; maintaining surface lining of the intestines, lungs, eyes,
skin, and mucous membranes, vitamin A further assists immunity through synthesis
of these healthy barriers to infection
• Recommended Intake: The RDA for vitamin A is 700 mcg retinol activity equivalents
(RAE) for women and 900 mcg RAE for men. The use of RAE for vitamin A
incorporates all forms, performed retinoids and provitamin forms such as the
carotenoids beta carotene, lycopene, and lutein. Provitamin sources have lower RAE
than preformed sources. Retinoids are found in foods from animal sources and some
vitamin supplements; carotenoids are found in plant-based foods and some vitamin
supplements. Nurses must understand the differences between these forms of vitamin
A since high intake of retinoids is associated with greater risk of toxicity.
©2011 by Pearson Education, Inc. Tucker, Instructor’s Resource Manual for Nutrition and Diet Therapy for Nurses
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Sources:
✓ Preformed vitamin A (retinoid) is found only in animal sources such as liver, fatty
fish, egg yolks, whole milk, and butter. Margarine, low-fat, and skim milk are
fortified with vitamin A. Preformed vitamin A is present in vitamin supplements.
✓ Provitamin A (carotenoid) is found in leafy green vegetables and deep orange,
yellow, and red fruits and vegetables, i.e., spinach, broccoli, winter squashes,
cantaloupe, carrots, tomatoes, and sweet potatoes.
✓ Vitamin A can also be found in fortified foods such as meal replacement drinks or
cereals.
Deficiency: occurs because of insufficient intake or from intestinal losses with chronic
diarrhea that results from fat mal-absorption, such as with pancreatic disease or cystic
fibrosis. Excess alcohol intake compromises vitamin A status by depleting liver stores.
Deficiency of vitamin A may lead to:
✓ changes in eye health called xerophthalmia
✓ changes in the integrity of epithelial cells that lead to skin alterations known as
follicular hyperkeratosis
✓ higher risk of death or severe illness from common infections and measles
Toxicity occurs from excess intake of vitamin A supplements (UL for vitamin A as
retinol in adults is 2,800 mcg for females and 3,000 mcg for males). Preformed vitamin A
in food is associated with toxicity symptoms.
Wellness Concerns and Supplement Use: Hypervitaminosis A occurs with excess storage
and results in toxicity. Symptoms include:
✓ nausea and vomiting
✓ headaches
✓ blurred vision
✓ bulging fontanel (in infants)
✓ liver damage
✓ diminished bone mineral density
✓ increased risk of hip fracture
✓ Nurses should assess patients for intake of fortified foods with vitamin A and
supplements containing retinol. Cautionary advice is needed with pregnant females
and patients who approach the UL of vitamin A. The optimal source of vitamin A is
food.
Vitamin D is technically a hormone because it is activated in one tissue and exerts its
effect on other tissues in the body. Provitamin forms of vitamin D must first undergo
hydroxylation by the liver and then the kidney to become biologically active. Provitamin
D3 can be synthesized in the skin when exposed to sunlight.
• Function: Vitamin D is responsible for maintaining blood levels of calcium and
phosphorus. Proper bone mineralization relies upon adequate vitamin D to promote
calcium absorption.
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Epidemiological studies show an association between low vitamin D levels in the
body and risk of certain cancers, type 1 diabetes, and cardiovascular disease.
• Observational studies note an inverse relationship between vitamin D levels and risk
of prostate, colon, breast, and pancreatic cancers.
• Vitamin D is known to play a vital role in immune function and cell growth and
division.
• Recommended Intake: The DRI for vitamin D as an adequate intake (AI) is:
✓ Birth to 50 years: 5 mcg or 200 IU.
✓ American Academy of Pediatrics recommends 10 mcg or 400 IU daily for infants,
children, and adolescents.
✓ Age 51–70 years: The AI doubles to 10 mcg or 400 IU
✓ After age 70 years: The AI increases to 15 mcg or 600 IU.
Sources: Sun exposure is an important source of vitamin D. As little as 10–15 minutes of
midday sun exposure of the face, arms, and legs a few times a week is enough for
adequate vitamin D synthesis. Living at greater than 35° latitude during winter, smog,
dark pigmented skin, and using sunscreen with SPF 8 or more reduces UVB exposure
and therefore vitamin D synthesis. Homebound individuals are at risk for altered vitamin
D status. Natural foods with vitamin D are oily fish. Milk, margarine, some orange juices,
and ready-to-eat cereals are fortified with vitamin D.
Deficiency: Poor vitamin D status occurs because of:
✓ insufficient intake
✓ little exposure to sunlight
✓ medical conditions such as malabsorptive diseases and liver or kidney disease that
impair vitamin activation
✓ medications, such as anticonvulsants and steroids, that can cause deficiency because of
drug-nutrient interactions
Up to 90% of older adults in the U.S. do not consume adequate vitamin D. Those with
greatest risk of low vitamin D intake include:
✓ teenage girls and adult females
✓ older adults because of poor intake and decreased cutaneous synthesis
✓ individuals who follow a vegan diet and consume no animal products
✓ those with milk intolerance
✓ exclusively breastfed infants
Poor vitamin D status can exist for months before clinical signs develop.
✓ Rickets is clinical vitamin D deficiency in children. Infants with dark skin and those
who are exclusively breastfed are at greater risk. Rickets is the result of poor bone
mineralization, yielding soft and malformed bones, particularly at the growth plates.
✓ Adult “rickets” is called osteomalacia, also a result of poor bone mineralization,
occurring when bone growth has ceased. Bones become soft and pliable.
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Vitamin D deficiency is associated with nonspecific musculoskeletal pain that is often
misdiagnosed as fibromyalgia or wrongly associated with other disorders. Muscular
weakness and pain in the older adult with vitamin D deficiency is associated with an
increased risk of falls and hip fracture.
Bone health is a partnership between vitamin D and calcium. Diminished bone mass is
called osteopenia. Restrictive eating, including dieting and disordered eating or excessive
alcohol intake, contributes to poor vitamin D and calcium intake.
Toxicity: Hypervitaminosis D is more likely to occur with over supplementation than
from excess intake of food sources of vitamin D. Toxicity causes hypercalcemia. The UL
for vitamin D in children and adults is 50 mcg daily. Nurses should consult with a
dietitian when considering vitamin D supplementation for individuals with fat
malabsorptive conditions, such as pancreatitis, or following bariatric surgery.
Vitamin E is the universal name given to eight forms of the vitamin. Only the form
known as tocopherol contributes to the body’s need for the vitamin. Other forms are
absorbed from the diet, but are not preferentially metabolized by the liver and found in
plasma. Another vitamin E is found in some nuts, soybeans, and sesame oils.
Function: Vitamin E acts as an antioxidant in the body; it is also known to alter platelet
aggregation and adhesion and to play a role in immune function.
Recommended Intake: The RDA for vitamin E is 15 mg (16.5 IU) for males and females
over 13 years of age.
Sources: Vitamin E occurs naturally in vegetable oils, nuts, and seeds. Some foods, such
as breakfast cereals and orange juice, are fortified with vitamin E. It is also available in
vitamin supplements as part of a multivitamin or as a single supplement in varying doses.
Deficiency: It is uncommon and most often linked to an inherited metabolic disease or fat
malabsorption. Deficiency first manifests itself as peripheral neuropathy, or tingling in
the hands and feet, and then progresses to ataxia, myopathy, and retinopathy. Premature
low birth weight babies can have vitamin E deficiency.
People with chronically low fat diets may have diminished intake of vitamin E.
Toxicity: The UL for vitamin E is 1,000 mg daily. High doses can increase bleeding or
hemorrhaging. It can increase the anticoagulant effect of aspirin and coumadin. Reports
have included an association between high-dose vitamin E supplements and increased
risk of heart failure, ischemic events, and reduction in the cardioprotective effects of
statin drugs.
Wellness Concerns and Supplement Use: All nursing assessments should include vitamin
and supplement use, along with usual daily dosages.
Vitamin K functions as a coenzyme in the synthesis of several proteins in the body.
• Function: Some of these proteins are involved in the synthesis of blood clotting factors
while others are important for bone health.
• Recommended Intake: 120 mcg/day for adult males and 90 mcg/day for adult females.
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Sources: Vitamin K is available in the diet from green leafy vegetables and some plant
oils, such as soybean, cottonseed, canola, and olive oils. The presence of fat in food
helps absorption of vitamin K. Vitamin K is also synthesized by bacteria in the large
intestine; however, it is not sufficiently utilized by the body to support overall vitamin
K requirements.
• Deficiency: Newborn infants receive an intramuscular injection of vitamin K at birth
to prevent vitamin K deficiency bleeding. Infants receive vitamin K from breast milk
or infant formula, in addition to beneficial bacteria that eventually develop in the
intestine. Cystic fibrosis can lead to vitamin K deficiency because of chronic antibiotic
use and insufficient pancreatic enzymes. Vitamin K is stored in the liver. High intake
of vitamin E can antagonize the anticoagulation effects of deficient vitamin K status.
• Toxicity: No adverse effects have been reported with excess intake of vitamin K in
healthy individuals not receiving anticoagulant therapy, therefore no UL exists for this
vitamin.
• Wellness Concerns and Supplement Use: Poor vitamin K intake has been associated
with increased risk of hip fracture. Nurses should be aware that the effectiveness of
anticoagulants, such as warfarin (Coumadin), can be reduced by high intake of vitamin
K, either by food or supplements. Clients on anticoagulant therapy should not take
vitamin K supplements without the advice of a dietician or physician.
Water-soluble vitamins include vitamin C and B-complex vitamins, thiamin (B-1),
riboflavin (B-2), niacin, pyridoxine (B-6), folate, the cobalamins (B-12), biotin, and
pantothenic acid. Water soluble vitamins are more easily destroyed by handling and
cooking than fat-soluble vitamins. Water-soluble vitamins are cofactors of metabolism
and recommended intake is linked to overall energy need; they are stored in the body in
lesser amounts than fat-soluble vitamins. This means that symptoms of deficiency are
evident more rapidly than with fat-soluble vitamins.
Vitamin C was not isolated until the 1930s, although it was known that citrus helped
cure scurvy.
Function: as an antioxidant and cofactor in the biosynthesis of many substances in the
body, it:
✓ acts as an antioxidant scavenging free radicals, preventing oxidation in leukocytes,
lung, and gastric mucosa
✓ promotes the absorption of iron and may spare or regenerate vitamin E in the body
✓ plays a role in the biosynthesis of collagen and connective tissue, important to the
healing process
✓ aids in synthesis of norepinephrine, carnitine, and the amino acid tyrosine
Recommended intake: 90 mg for adult males and 75 mg for adult females. The
requirement for smokers is increased by 35 mg/day because of the oxidation stress of
smoking.
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Source: Vitamin C is present in fruits and vegetables, citrus fruits in particular. An intake
of five servings of fruits and vegetables should contain adequate vitamin C.
• Deficiency: Scurvy is the name for vitamin C deficiency. Symptoms include:
deterioration in connective and elastic tissues, pinpoint hemorrhages on the skin
(petechia), and swollen, bleeding gums (scorbutic gums). Wound healing may be
compromised. Death may result from hemorrhaging.
• Those at risk for vitamin C deficiency include:
✓ individuals with poor intake of fruits and vegetable
✓ those who abuse alcohol or drugs
✓ Smokers
✓ people receiving dialysis treatment for renal failure
✓ Treatment for vitamin C deficiency is 1 gm/day given for 5 days, followed by 300–
500 mg/day for a week.
✓ Vitamin C is easily destroyed by prolonged storage and cooking times
• Toxicity: The UL for vitamin C intake is 2,000 mg/day. Intake above this is associated
with gastrointestinal side effects such as diarrhea, abdominal cramping, and nausea. In
some individuals excess intake can increase oxalate kidney stones, as well as dental
enamel erosion and rebound scurvy.
• Wellness Concerns and Supplement Use: The practice of taking vitamin C supplements
to avoid the common cold is well known but not scientifically substantiated.
10. Thiamine was the first B vitamin to be identified and so is called B-1. It is the most
urgently required of the B vitamins.
• Function: as a coenzyme in the metabolism of carbohydrates and amino acids. An
individual at risk for thiamine deficiency should receive thiamine supplementation when
receiving intravenous glucose.
• Recommended Intake: The RDA for adults is 1.2 mg/day for males and 1.1 mg/day for
females. RDA is based upon energy intake in these groups.
• Sources: Thiamine is available in a wide variety of foods. Primary sources are enriched
bread, bread products and cereals, processed meat.
• Deficiency. Alcoholism is the most common cause of thiamine deficiency. It decreases
the absorption and liver storage of thiamine and increases its utilization. Additional risk
factors for thiamine deficiency include persistent vomiting, malabsorptive
gasatrointestinal diseases, and intestinal surgeries. Also, cultural food practices can lead
to thiamine deficiency. Symptoms of deficiency include:
✓ fatigue
✓ muscle weakness
✓ neurological complaints; numbness and tingling of extremities
✓ Beriberi is the name given to thiamine deficiency. It can progress to muscle wasting
and worsened neurological complaints (dry beriberi) or edema and cardiac failure (wet
beriberi), which mimics the symptoms of heart failure.
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✓ Wernicke-Korsakoff syndrome is comprised of two disorders, Wernicke’s
encephalopathy and Korsakoff’s psychosis. This is a condition of the brain in which
memory loss, disorientation, confabulation, altered gait (ataxia), and rapid, jerky eye
movements (nystagmus) occur.
• Toxicity: No UL recommendation exists for thiamine because of insufficient data.
• Wellness Concerns and Supplements: Patients who have undergone gastric bypass
surgery for treatment of obesity have been reported to be at risk for thiamine deficiency.
Treatment of heart failure with loop diuretics to manage fluid imbalance leads to
increased urinary losses of thiamine, furthering the risk of thiamine deficiency.
Consumption of a multivitamin promotes adequate intake on a daily basis. Risk of
toxicity is low.
11. Riboflavin was identified after thiamine, so is known as B-2. Like many B-complex
vitamins, riboflavin is sensitive to light (which is why milk is sold in opaque containers).
• Function: It functions as a coenzyme in various reactions involving metabolism and
energy production. Some reactions are dependent on other B vitamins.
• Recommended Intake: The RDA for adults is 1.3 mg/day for males and 1.1 mg/day
for females. Requirements increase with pregnancy and lactation.
• Sources: Riboflavin is available in foods from animals and plants; dairy, meat, whole
grains, and dark green leafy vegetables.
• Deficiency: known as ariboflavinosis. Deficiency is usually accompanied by other
nutrient deficiencies. Those at risk have little intake of dairy or meat. A single bowl
of enriched cereal with milk provides adequate riboflavin.
✓ Symptoms of riboflavin deficiency include sore throat with edema of the
pharyngeal and oral mucosa, a magenta-colored tongue with glossitis (atrophy of
the taste buds), angular stomatitis (fissures at corners of mouth), cheilosis
(swollen, fissured lips) and seborrheic dermatitis around the nasolabial folds.
• Toxicity: No UL for riboflavin exists.
• Wellness Concerns and Supplements: There is little concern regarding general issues
of wellness because riboflavin is widely available in foods.
12. Niacin. Originally called the pellagra-preventing vitamin or vitamin B-3. It has two
forms, nicotinic acid and niacinamide. The amino acid tryptophan can be converted into
niacin by the body.
• Function: Niacin acts as a coenzyme or co-substrate in many biological reactions,
including the metabolism of alcohol, proteins, fatty acids, lactate, pyruvate, and in
the synthesis of steroids.
• Recommendation: The RDA for niacin is expressed as “niacin equivalents” taking
into consideration the conversion of tryptophan content in foods to niacin. The RDA
for adults is 16 mg/day NE of males and 14 mg/day NE for females.
• Sources: poultry and lean meats. Other high-protein foods such as dairy, whole grain
breads and bread products, and ready-to-eat cereals are important sources.
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Deficiency. Pellagra is the term used for niacin deficiency, which encompasses the
“4D’s of pellagra”: dermatitis, diarrhea, depression, and ultimately death.
• Those at risk for poor niacin status are those with overall poor diet, lacking protein
and dairy. This includes those who consume a corn-based diet, alcoholics, those with
metabolic diseases, individuals with anorexia nervosa, and those who had gastric
bypass surgery.
• Toxicity: The UL for niacin intake is 35 mg/day NE. No adverse effects have been
reported for intake of naturally occurring niacin foods; supplements, fortified foods
and pharmacological agents containing niacin should be monitored. Nurses should
question patients about any self-prescribed treatment of high blood lipids as various
forms of high dose niacin are available over the counter.
• Wellness Concerns and Supplements: Niacin has been used to treat high blood
cholesterol and triglycerides for a number of years. Side effects include flushing of
the face, arms, and chest in addition to redness and a burning or itching sensation
from dilation of small subcutaneous blood vessels. Special consideration should be
given to patients with cirrhosis, dialysis treatment of renal disease, long-term
isoniazid treatment for tuberculosis, or multiparous females as the RDA specifically
does not meet the needs of these individuals.
13. Vitamin B-6 is comprised of pyridoxine and several related forms that are converted to
pyridoxal phosphate in the body.
• Function: Vitamin B-6 is a coenzyme for over 100 enzyme reactions in the metabolism
of amino acids, glycogen, neurotransmitters, and precursors to hemoglobin synthesis.
Vitamin B-6 is required for the conversion of trytophan to niacin by the body.
• Recommended Intake: The RDA is 1.3 mg/day for males and females. In adults older
than 50 years the requirement for B-6 increases slightly to maintain plasma levels of
pyridoxal in a normal range.
• Sources: whole grains/cereals, legumes, and protein-containing foods such as poultry
and beef. Excessive heat can destroy pyridoxine in processing or cooking.
• Deficiency: leads to seborrheic dermatitis and can contribute to microcytic anemia.
Reduced synthesis of neurotransmitters from poor B-6 status leads to convulsions,
depression, and confusion. Oral contraceptives, isoniazid for tuberculosis and
penicillamine used for treating rheumatoid arthritis, and lead poisoning are medications
that compromise vitamin B-6.
• Toxicity: The UL for vitamin B-6 is 100 mg/day. No adverse effects have been reported
from high intake of vitamin B-6, however, large supplemental doses have been
associated with development of peripheral neuropathy.
• Wellness Concerns and Supplemental Use: Supplemental vitamin B-6 is often
recommended in the popular press for treatment of premenstrual syndrome, although
there are no definitive data to support this.
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14. Folate exists in several forms depending on the source of the vitamin. Folate denotes the
vitamin that is found naturally in foods, while folic acid is found in supplements. Folic
acid is 50% more bioavailable for absorption by the body than folate in foods.
• Function: Folate functions as a coenzyme in the metabolism of nucleic acids and
amino acids. Folic acid plays a role in the prevention of neural tube defects, which are
among the most common type of birth defect. Anencephaly, spina bifida, and
encephalocele defects occur when the neural tube fails to close during fetal
development.
• Recommended Intake: The RDA for folate is expressed as dietary folate equivalents
to account for the difference in bioavailability of folate and folic acid. The RDA for
adults is 400 mcg/day with additional recommendations for females of childbearing
age who are advised to consume 400 mcg/day of folic acid from supplements or
fortified foods. For pregnant females the RDA is 600 mcg/day
• Sources: Green leafy vegetables, legumes, citrus juice, liver, fortified wheat flourbased products such as breads, cereals, pasta, and baked goods. Folate is easily
destroyed during food storage and cooking.
• Deficiency: First sign of folate deficiency is decreased folate content in plasma and
then red blood cells. Changes are not apparent in early stages of deficiency. Physical
symptoms of anemia from folate deficiency are the same as other anemias: fatigue,
difficulty concentrating, headache, shortness of breath on exertion, heart palpitations
and tachycardia (increased heart rate). When deficiency of folate is suspected,
vitamin B-12 status should be assessed. Those at risk for folate deficiency are those
with inadequate intake due to poor diet, such as alcoholics. Many medications alter
folate status by decreasing absorption.
• Toxicity: The UL for folate is 1,000 mcg/day from fortified foods and supplements.
Folic acid supplements over 1,000 mcg are not available over the counter.
• Wellness Concerns and Supplement Use: Folic acid, along with vitamins B-12 and B6, have been reported to lower elevated homocysteine levels, which are associated
with increased risk of cardiovascular disease.
15. Vitamin B-12 refers to a group of compounds belonging to the cobalamin family.
Absorption of vitamin B-12 requires several factors for optimal bioavailability. About
50% of ingested vitamin B-12 is absorbed under optimal conditions.
• Function: B-12 is a coenzyme in the metabolism of amino acids and reactions
producing nucleic acids, neurotransmitters, and the myelin sheaths of the central
nervous system. It is required for cell division and normal neurological function.
• Recommended Intake: The RDA for vitamin B-12 is 2.4 mcg/day in adults.
• Sources: Vitamin B-12 is found in foods of animal origin and fortified foods such as
breakfast cereals and some soy products.
• Deficiency: Vitamin B-12 deficiency leads to hematological changes. Neurological
symptoms may occur and are reversible if vitamin B-12 treatment is given in a timely
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fashion, but they can be permanent. Individuals at risk of vitamin B-12 deficiency
include those who have:
✓ inadequate intake
✓ lack of adequate gastric acid or intrinsic factor production
✓ malabsorptive conditions or bacterial overgrowth in the intestine
✓ Older adults and individuals who use medications to buffer or diminish gastric acid
production are at risk for food-cobalamin deficiency.
✓ Breastfed children of mothers who are vegans.
✓ Pernicious anemia is an autoimmune disease associated with vitamin B-12
deficiency. A dose of 1 to 2 mg of crystalline vitamin B-12 is prescribed for
deficiency.
• Toxicity: No UL for vitamin B-12 has been established.
• Wellness Concerns and Supplement Use: The DRI recommendations for vitamin B-12
urge supplemental or food-fortified sources of the vitamin for those over 50 years of age.
Synthetic vitamin B-12 or fortified foods are recommended for vegans because plant
forms of the vitamin are not bioavailable in humans.
16. Biotin was discovered in 1927, but not recognized as a vitamin for another 40 years.
• Function: acts as a cofactor for enzymes in metabolic reactions involving
gluconeogenesis, fatty acid metabolism, and catabolism of the amino acid leucine.
Biotin may play a role in regulating transcription of proteins.
• Recommended Intake: The DRI is given as an AI rather than an RDA. The AI for
biotin in adults is 30 mcg/day.
• Sources: Organ meat and egg yolks. Traditional food composition tables do not
contain information on biotin content of foods. Biotin is felt to be widely distributed in
foods, but can be protein-bound in some foods, affecting its bioavailability. Biotin is
synthesized by the microflora present in the gastrointestinal tract, although it is
unknown whether this form contributes to biotin status in the body.
• Deficiency: Biotin deficiency may lead to hair loss (alopecia) and a red scaly rash
above the eyes, nose, and mouth. Central nervous system alterations can occur. Those
at risk of deficiency are those who habitually consume raw egg whites or who have
short-gut syndrome.
• Toxicity: No UL exists for biotin.
17. Pantothenic Acid is a vital component of metabolism and is widely available and rarely
deficient in the diet, thus seldom capturing the attention of health care providers.
• Function: It is involved in the synthesis of coenzyme A, an important cofactor of
metabolism. The vitamin is also required for fatty acid synthesis.
• Recommended Intake: The AI for pantothenic acid is 5 mg/day for adults.
• Sources: Pantothenic acid is present in most foods. Protein-containing foods, such as
meats, eggs, poultry, and dairy foods, as well as plant foods are good sources.
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Deficiency: Deficiency of pantothenic acid is rare. Symptoms include irritability and
restlessness and generalized gastrointestinal complaints, such as nausea, vomiting, and
abdominal cramps.
Toxicity: Insufficient evidence exists to recommend a UL. No population subgroups have
been identified as being at risk.
LEARNING OUTCOME 3
To differentiate risk factors for hypovitaminosis and hypervitaminosis.
Concepts for Lecture
1. Hypovitaminosis is the term used to indicate insufficient vitamin stores and occurs for
three primary reasons:
• decreased vitamin intake
• altered absorption or metabolism
• increased need for the vitamin
Physical signs and symptoms of hypovitaminosis do not occur early. First, vitamin storage or
plasma levels are diminished. Only when vitamin status has been diminished for a longer period
are alterations in vitamin functions evident, including physical signs and symptoms. When
physical evidence of poor vitamin status is present, this indicates that the problem is long term.
When poor vitamin status is suspected, but no clinical evidence is obvious, the deficiency is
considered subclinical.
2. Hypervitaminosis is the term used to indicate excessive vitamin stores. Most cases occur
due to the use of supplemental vitamins rather than from excess consumption of foods
containing a high amount of a particular vitamin. It may occur from eating fortified
foods, especially when combined with supplemental vitamin use.
• Fortified foods are those with nutrients added that are not naturally found in the food.
• Enriched foods are those that have nutrients replaced that may have been lost in
processing.
©2011 by Pearson Education, Inc. Tucker, Instructor’s Resource Manual for Nutrition and Diet Therapy for Nurses
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