NUTR Module 9

Fat Soluble Vitamins (A, D, E, K)

Vitamin A

• Discovered in 1913

• Exists in three forms:

  • retinol (most active form, stored in the liver),

  • Retinal

  • retinoic acid

Functions include:

• Maintaining the integrity of epithelial cells

  • Found in skin, lungs, and lining of the GI tract

  • Cell differentiation:

    • the process where cells become specialized to perform specific functions

• Bone growth

  • Stimulates the bone cells that break down the inner part of bone

    • Can lead to poor growth in children

• Cell membrane stability

• Gene regulation

  • Role in turning genes on and off

  • Indirect tole in the regulation of metabolism

• Vision

• Immune function (especially for children)

  • Disease resistance in children

  • Production of white blood cells

Functions of Vitamin A

• Crucial to normal vision

  • Early stages of deficiency

    • Night blindness

      • Reversible

• Maintenance of healthy cornea tissue

  • Short-term vitamin A deficiency:

    • Corne becomes dry and damaged

  • Long-term vitamin A deficiency

    • Xerophthalmia

      • Permanent loss of vision

Dietary Sources:

• Preformed Vitamin A:

  • Ready to use

    • found in animal-based or fortified foods

      • Examples: fortified milk, cheese, cream, butter, eggs, liver

  • Bioavailability is 70-90%

• Provitamin A

  • Converted to the active form as needed

    • Example: beta-carotene.

    • Found in plant-based foods:

      • green leafy vegetables

      • orange and red produce

        • apricots, cantaloupe, carrots, sweet potatoes, pumpkins

      • Bioavailability is variable, ranging from 9-22%.

Recommended Intakes for Vitamin A:

• RDA

  • 900 µg RAE per day for men

  • 700 µg RAE per day for women

  • Increased needs for:

    • Women who are pregnant and breastfeeding

Vitamin A Toxicity:

• Vitamin A is stored in fat tissue and the liver

  • remaining in the body for a longer time.

• Symptoms of toxicity include

  • liver damage

  • birth defects

• Nutrient interaction

  • Vitamin A deficiency may coexist with iron deficiency.

Beta-Carotene Supplementation:

• Provitamin A (including beta-carotene) is not toxic.

• Beta-carotene may help prevent heart disease and cancer.

• Increased risk of lung cancer in smokers taking beta-carotene supplements.

• Health professionals do not recommend beta-carotene supplementation for the general public.

Vitamin D (Cholecalciferol):

• Discovered in 1922

• Classified as a vitamin, hormone, and steroid.

Functions of vitamin D

• Regulation of calcium metabolism.

  • Stimulates cells of the small intestine to produce calbindin

    • a calcium-binding protein, which can increase calcium absorption.

• Stimulates the kidneys to conserve calcium

  • decreasing urinary calcium excretion.

• Stimulates calcium release from bone to help maintain blood calcium levels.

Dietary Sources:

• Very few foods are naturally concentrated in vitamin D.

  • cod liver oil, sardines, salmon, shrimp, liver, and mushrooms exposed to UV light.

• Fortified foods provide the majority of dietary vitamin D

  • milk, margarine, cereals, juices.

  • Note: Cheese and yogurt are not often fortified with vitamin D.

Vitamin D Synthesis:

• The human body makes vitamin D with adequate exposure to sunlight through a series of steps.

  • Cholesterol in skin combines with ultraviolet rays

  • converted into a precursor of vitamin D

  • eventually making its way to the kidneys where it is converted to the active form D₃.

Factors Influencing Vitamin D Synthesis:

• Distance from the equator

• Amount of clothing coverage on the body

• Sunblock use

• Cloud cover or smog

• Skin color

• Age

Recommended Intakes of Vitamin D:

• Food and Nutrition Board of Institute of Medicine recommends:

  • Infants: 400 IU (10 µg) per day (AI).

  • Ages 1 to 70 years: 600 IU (15 µg) per day (RDA).

• Why do requirements increase with age?

  • requirements increase with age due to decreased ability to convert vitamin D to its active form and decreased likelihood of adequate sun exposure.

    • Adults > 70 years: 800 IU (20 µg) per day (RDA)

Deficiency:

• Children

  • Rickets

    • a disease characterized by softening and deformity of long bones due to the inability to deposit calcium in newly formed bone.

    • This can lead to malformation of the skull, rib cage, and ends of long bones.

• Adults

  • Osteomalacia

    • softening of bone caused by decalcification.

Vitamin D Toxicity:

• Not common.

• Occurs from overuse of supplements.

• Symptoms

  • nausea, vomiting, diarrhea, calcification of soft tissues.

• Food fortification with vitamin D is strictly regulated.

Supplementation:

• High rates of vitamin D insufficiency in the U.S.

  • 90% of ethnic populations with dark skin

  • 75% of the Caucasian population.

• Possible link between vitamin D insufficiency and chronic diseases

  • heart disease, respiratory infections, diabetes, and hypertension.

Vitamin E:

• Discovered in 1922.

• A fat-soluble vitamin

  • primarily found in cell membranes

• Not a single compound, but a group of compounds called tocopherols

  • There are four different types of tocopherols

    • alpha, beta, gamma, and delta

Functions:

• Acts as an antioxidant

  • neutralizing free radicals that can damage cell membranes, DNA, and proteins.

  • Enhances immune function

• Required for nerve cell development

• In the past, the use of vitamin E supplements recommended to protect against cancer & CVD

Vitamin E and Free Radicals:

• As an antioxidant, vitamin E fights against

  • Free radicals are unstable compounds with an unpaired electron that attacks other molecules with electrons.

    • This initiates a chain reaction, damaging cell membranes, proteins, enzymes, and DNA.

• Vitamin E donates an electron to neutralize free radicals.

Recommended Intakes For Vitamin E

• RDA: 15 mg per day for adults.

• UL: 1,000 mg per day for adults.

Note: The UL may be lower for some populations, such as smokers, due to an increased incidence of brain hemorrhage among those who take vitamin E supplements.

Vitamin E Deficiency:

• Rare

• Most likely to occur in premature infants due to insufficient stores.

• Condition resulting from vitamin E deficiency:

  • anemia due to red blood cell fragility and subsequent rupture.

• Other symptoms include:

  • loss of muscle coordination and reflexes, muscle weakness, reproductive failure, and impaired vision.

Vitamin E Toxicity:

• Signs of toxicity include:

  • headache, nausea, blurred vision

  • reduced sexual function in men

  • accelerated signs of aging

  • inflammation of the mouth

  • chapped lips

  • Fatigue

  • GI disturbances

  • muscle weakness

  • increased bleeding

• Vitamin E can be toxic as a fat-soluble vitamin

Vitamin K

• Discovered in 1929.

• Primary Function:

  • Blood clotting by activating proteins required to make fibrin

  • Fibrin: which forms blood clots.

• Required for the synthesis of the bone protein: osteocalcin

Vitamin K Deficiency:

• Primary deficiency is rare in adults.

• Population at highest risk for deficiency:

  • Newborns, due to:

  • Relatively sterile GI tract at birth.

  • Breast milk being a poor source of vitamin K.

• A single dose of vitamin K is given at birth.

• Oher potential risk factor

  • Prolonged antibiotic use

Vitamin K Sources:

• Nonfood source

  • Bacteria in the large intestine, which is the most significant source for humans.

• Food sources:

  • Green vegetables (spinach, kale, cruciferous vegetables).

  • Green fruits (avocado, kiwi).

  • Some vegetable oils.

Fat Soluble

• Storage in body

  • Longer period

  • Larger amounts

  • In liver and fat cells

• Increase likelihood of adverse effects or toxicity

Water Soluble

• Storage in body

  • Short period of time

  • Not generally stored in large quantities

• Decrease the likelihood of toxicity

• Greater risk of deficiency

Vitamins:

• Vitamins are micronutrients that are not energy-yielding but are involved in metabolic processes that assist in providing energy.

• Vitamins

  • Organic

• Minerals

  • Inorganic

• Vitamins can be lost during processing and added back to meet needs (enrichment).

• Vitamins may also be added to foods in which they are not naturally present (fortification).

Vitamin C:

• Also known as ascorbic acid.

• Discovered in 1926.

• Vitamin C deficiency causes scurvy, a disease characterized by:

  • Bleeding gums

  • Tooth loss

  • Poor wound healing

  • Small hemorrhages on the skin

Roles of Vitamin C:

• Acts as an antioxidant, which supports immune system health.

• Synthesis of collagen:

  • a protein that forms the connective tissue of tendons, bones, teeth, and skin.

  • Functions of Collagen is important for:

    • Wound healing

    • Maintenance of blood vessel structure

• Facilitates iron absorption in the GI tract.

Recommended Daily Allowance (RDA) for Vitamin C:

• 90 mg per day for males.

• 75 mg per day for females.

  • Smokers require an additional 35 mg per day because vitamin C is used to protect the body against damaging compounds in tobacco smoke.

Upper Limit (UL) for Vitamin C:

• 2,000 mg per day.

• Supplementing at greater than 1,000 mg per day can cause diarrhea and bloating.

Vitamin C Food Sources:

• Fruits and vegetables

  • Orange juice is the best-known source.

• Other good sources:

  • Other citrus fruits: limes, lemons

  • Kiwis

  • Strawberries

  • Sweet potatoes

  • Brussels sprouts

• Vitamin C is vulnerable to heat and oxygen, so food preparation affects levels in food.

Vitamin C Deficiency:

• Scurvy

  • a severe deficiency, results in the improper formation of collagen.

• Anemia

  • due to poor iron absorption.

Signs of deficiency include:

• Bleeding gums

• Loss of appetite

• Small hemorrhages on the skin

• Impaired growth

• Weakness

• Scorbutic rosary in infants.

B Vitamins:

• B vitamins include:

  • Thiamin (B₁)

  • Riboflavin (B₂)

  • Niacin (B₃)

  • Vitamin B₆

  • Folate (B₉)

  • Vitamin B₁₂

  • Pantothenic acid

  • Biotin

• A common function of all B vitamins:

  • Act as coenzymes or cofactors in energy metabolism to assist enzymes with energy release.

    • Without the coenzyme, the enzyme cannot function.

Thiamin (B₁)

• First individual B vitamin identified.

• Part of the coenzyme thiamin pyrophosphate (TPP), which:

  • Assists in the metabolism of carbohydrates and some amino acids.

  • Converts pyruvate to acetyl CoA.

    • Is used in the Kreb's cycle.

• Assists in the function of nerve and muscle cell activity.

RDA for Thiamin:

• 1.2 mg per day for males.

• 1.1 mg per day for females.

• No UL because no adverse effects have been observed with excess consumption.

Food Sources of Thiamin:

• Pork

• Whole grains

• Fortified breakfast cereals

• Enriched grains

• Peanuts

Thiamin Deficiency:

• Occurs in malnourished individuals and alcoholics.

• Beriberi is a thiamin deficiency seen in malnourished individuals.

  • Beriberi is a condition in which the heart becomes enlarged, fluid accumulates beneath the skin, and muscles weaken and atrophy.

• Wet beriberi primarily affects the cardiovascular system.

• Dry beriberi primarily affects the nervous system.

• Wernicke-Korsakoff syndrome is seen in alcoholics with severe thiamin deficiency.

Riboflavin (B₂)

• Part of the coenzymes:

  • Flavin mononucleotide (FMN)

  • Flavin adenine dinucleotide (FAD)

• Functions in energy release from macronutrients.

  • FAD acts as an "electron shuttle."

RDA for Riboflavin:

• 1.3 mg per day for males.

• 1.1 mg per day for females.

• No UL

  • Excess riboflavin from supplements is excreted in urine, giving it a bright yellow color.

Food sources of Riboflavin:

• Milk

• Enriched bread, cereals, and pasta.

• Riboflavin is destroyed by ultraviolet light and irradiation.

Riboflavin Deficiency:

• Frequently occurs in conjunction with other water-soluble vitamin deficiencies.

• Results in Inflammation of membranes:

  • Sore throat

  • Cracks in the corner of the mouth

  • Swollen, glossy tongue

  • Skin rashes

  • Hypersensitivity to light

Niacin (B₃)

• Found in two chemical forms:

  • Nicotinamide

  • Nicotinic acid

• Used to release energy from macronutrients

• Almost every metabolic pathway in the body uses one of the two niacin-containing coenzymes:

  • Nicotinamide adenine dinucleotide (NAD)

  • Nicotinamide adenine dinucleotide phosphate (NADP)

• Used in the synthesis of fatty acids.

RDA for Niacin:

• 16 mg per day for males.

• 14 mg per day for females.

UL for Niacin:

• 35 mg per day.

• Based on adverse effects of excess intake from supplements.

  • Flushing

    • redness of face, arms, and chest.

  • Tingling sensation.

Niacin Food Sources: (Also synthesized by the body from the essential amino acid tryptophan)

• Milk

• Eggs

• Meat

• Poultry

• Fish

• Whole-grain and enriched bread and cereals

Niacin Deficiency:

• This leads to a condition called pellagra.

  • Symptoms of pellagra are referred to as "the four Ds":

    • Diarrhea

    • Dermatitis

    • Dementia

    • Death

• A major problem in the southeastern US in the early 1900s through the 1930s due to a diet void of niacin

  • (fat back, grits, and molasses).

Niacin Toxicity:

• One of the few water-soluble vitamins with toxicity symptoms.

• Overconsumption of supplements or fortified foods can cause "niacin flush"

  • from consuming 3 to 4 times the RDA

  • causes redness of the face, arms, and chest

  • Niacin flush is a temporary condition.

    • High doses of nicotinic acid prescribed for cholesterol reduction result in niacin flush.

• Other toxicity concerns include liver injury.

Vitamin B₆

• Participates in diverse biochemical reactions.

• Key function:

  • synthesis of nonessential amino acids through transamination.

• Other functions:

  • Synthesis of glucose and some types of lipids.

  • Production of the neurotransmitter serotonin.

  • Hemoglobin synthesis.

  • Vitamin B₆ deficiency can lead to anemia.

RDA for Vitamin B₆:

• 1.3 mg per day for adults (19-50 years of age).

UL for Vitamin B₆:

• 100 mg per day.

Food Sources of Vitamin B₆:

• Beef liver

• Meats, poultry, and salmon

• Baked potatoes

• Bananas and watermelon

• Navy and pinto beans

Vitamin B₆ Deficiency:

• Occurs with a deficiency of other B vitamins.

• Deficiency symptoms are diverse:

  • Anemia

  • Depression

  • Dermatitis

  • Convulsions

  • Weakened immune response

• Toxicity symptoms

  • Numb feet

  • Loss of sensation in the hands

  • Nerve damage that progresses to the inability to walk.

  • Many of the symptoms are not reversible.

Folate (B₉)

• Consumed in two forms:

  • Folate: Naturally occurring form.

  • Folic acid: Synthetic form, which is easier to absorb in the GI tract.

• Important function of folate:

  • Cell division.

    • DNA replication requires folate during cell division.

• Affects:

  • red blood cell synthesis

  • central nervous system formation during fetal development.

DRIs for Folate:

• Folic acid is easier to absorb than folate

• The Dietary Folate Equivalent (DFE) is a unit of measure used to represent the conversion of folic acid to folate.

RDA for Folate:

• 400 µg DFE per day for adults (≥19 years of age).

• Increased requirements for:

  • Women planning on becoming pregnant.

  • Pregnant and lactating women.

UL for Folate:

• 1 mg folic acid per day.

Food Sources of Folate:

• Dietary sources of folate:

  • Orange juice

  • Green leafy vegetables

  • Legumes

• Dietary sources of folic acid:

  • Supplements

  • Enriched grains

Folate Deficiency:

• Inability to synthesize DNA during folate deficiency

• Results in large, immature red blood cells that are fewer in number

  • which is called macrocytic anemia.

• Deficiency during pregnancy can result in:

  • Spina bifida: Failure of the spinal cord to close completely.

  • Anencephaly: Lack of or incomplete development of brain and skull.

    • Together, spina bifida and anencephaly are known as neural tube defects.

    • The prevalence of neural tube defects has decreased since folate fortification.

Vitamin B₁₂

• Unique features of vitamin B₁₂:

  • Contains the mineral cobalt as part of its structure.

  • Synthesized by bacteria and other microorganisms.

  • Found naturally only in foods of animal origin within protein.

  • Stored in the body in significant amounts.

  • Requires intrinsic factor for absorption.

Functions of Vitamin B₁₂:

• Essential in converting folate into its active form.

• Maintains the insulating lining that covers nerve fibers known as the myelin sheath.

• Vitamin B₁₂ and folate are important for homocysteine metabolism.

  • High levels of homocysteine (an amino acid) in the blood increase the risk of cardiovascular disease.

RDA for Vitamin B₁₂:

• 2.4 µg per day for adults.

• No UL for Vitamin B₁₂.

Vitamin B₁₂ Food Sources:

• Sources of naturally occurring vitamin B₁₂:

  • Animal-based foods:

  • Milk

  • Cheese

  • Meat (especially organ meats)

  • Poultry

  • Seafood

• Foods fortified with vitamin B₁₂:

  • Ready-to-eat cereals

  • Soy products

  • Supplements

Vitamin B₁₂ Absorption:

• B₁₂ must be released from dietary protein before it can be absorbed.

  • This occurs in the stomach with the help of hydrochloric acid and pepsin.

• After release, vitamin B₁₂ is bound by intrinsic factor, a protein secreted in the stomach.

  • Intrinsic factor protects vitamin B₁₂ from degradation until absorption.

• Absorption occurs in the lower ileum.

Aging and Vitamin B₁₂ Absorption:

• Vitamin B₁₂ absorption decreases during aging because of:

  • Decreased intrinsic factor.

  • Decreased hydrochloric acid secretion, which decreases the ability to release vitamin B₁₂ from dietary protein.

• Adults >50 years of age are recommended to take a vitamin B₁₂ supplement.

Vitamin B₁₂ Deficiency:

• Can result in:

  • Macrocytic anemia

  • Pernicious anemia if due to a lack of intrinsic factor.

• Conditions in which reduced intrinsic factor occurs:

  • Genetic defect Aging

  • Portion of the stomach removed:

    • Roux-en-Y surgery

    • Stomach cancer

Biotin (B₇)

• Involved with fatty acid synthesis.

• Deficiency is rare.

RDA for Biotin:

• 30 µg per day for adults.

• No UL for Biotin.

Food Sources of Biotin:

• Liver

• Soybeans

• Fish

• Whole grains

Pantothenic Acid (B₅)

• Involved in the synthesis of lipids, steroid hormones, and neurotransmitters.

• Deficiency is rare.

RDA for Pantothenic Acid:

• 5 mg per day for adults.

• Food sources are found in most foods.