NS 1150 Prelim 3

L14-L20, A2, A3

What are Vitamins

Organic molecules found in both plants & animal-derived foods required in small amounts to maintain body's basic functions

• 13 known Vitamins

• Serve as Coenzymes(not all)

What are the essential vitamins(micronutrients) for survival

Vitamin A - Vision

Vitamin C - Scurvy

Vitamin D - Bone Health

Vitamin K - Coagulation

What Vitamins can be Obtained without Food

Vitamin D - UV rays from sun to skin

Vitamin K - activity of intestinal bacteria

Vitamins Synthesized from Diet or Dietary Provitamins

Beta-carotene (provitamin A), naturally found in food, can be converted into active form of vitamin A called retinol

What are Provitamins

Vitamin precursors that can be converted to the active form of a Vitamin

Classification of (13) Vitamins

Water Soluble

• All Vitamin B

• Vitamin C

Lipid Soluble

• Vitamins A, D, E, K

What are 2 conditionally essential vitamins-like compounds that are water-soluble

Choline & Carnitine (endogenously synthesized & Doesn’t act as coenzymes) 

Water Soluble vs Lipid Soluble

(Supplies, Body Stores, Toxicity, Absorption, Stability in Food Processing)

Water Soluble = Short term supply available, little storage, low risk of toxicity, easily absorbed into the blood, less stable in food (breaks down easily)

Fat Soluble = Long term supply available, stored in adipose, higher risk of toxicity, absorbed into lymph like lipids (requires protein carriers to travel in blood), more stable in food

What is Bioavailability & What Influences It(5)

Proportion of a nutrient in food that is absorbed & used by the body

Influenced by:

• Substances in food

• Nutritional Status

• Age (producing less HCl as you age prevents you from accessing and separating B12 from the food matrix)

• Medication (lots of antacids lead to decreased HCl)

• illness (kidney disease alters needs for nutrients)

How are vitamins destroyed by Heat

Heating at extreme temperature for long period of time desotry most of the water soluble vitamins

• Recommendation: don’t overcook fruits & vegetabls

How are vitamins destroyed by Light

Light destroys several of B Vitamins like milk exposed to light leads to destruction of riboflavin

• Recommendation: don’t put milk in glass

How are vitamins destroyed in excess water

Water soluble vitamins can move out of foods when they are placed in water

• Recommendation: Don’t soak food or cooked veggies 

How are vitamins destroyed by alkaline conditions

High pH(low acidity) can desotry thiamin & vitamin c

• Recommendation: avoid adding baking soda to veggies to maintain their colors

How does oxidation destroy vitamins

Vitamin C & many B vitamins are destroyed by exposure to air(oxygen)

• Recommendation: Store vitamin-rich food in air-tight containers 

What are Coenzymes

Organic Molecules that attach to enzyme & activates/increase enzyme ability to catalyze metabolic reactions

What Vitamin is required for Collagen Synthesis

Vitamin C

• Enzyme prolyl- & lysyl hydroxylase use Vit C as a co-factor to add -OH groups to pro-collagen which increases the strength & connective tissue

What is the most common cause of vitamin supplementation

Vitamin Toxicity

Very Rare from Dietary Vitamins

What are minerals

Inorganic molecules, other than water, that are essential for human survival

• essential nutrient because body cannot make (animal based have more bioabailability than plant)

• Cofactors

• Cannot be created or destroyed(not by cooking or digestion)

How are minerals lost

Sweat

• Sodium, Chloride, Potassium, Calcium, Iron, & magnesium

Classification of minerals

Macrominerals - Needed in amounts >100mg/day

Microminerals(trace minerals) - needed in amounts less than or equal to 100 mg/day

What are some example mineral cofactors

Mg acts as cofactor for DNA synthesis

Iron & Sulfer combine into Fe-S clusters and is most common cofactor observed: ETC, TCA, DNA repair

Mineral Toxicity

Rare due to tight regulation of absorption, excretion, & storage

Body stores small amounts of certain minerals

Exception: genetic disorder or overconsumption of mineral-containing supplement

What is Micronutrient Fortification

adding nutrients to foods that were either not present or present in small amounts before processing

Reason to Fortify Foods (4)

Correct Dietary insufficiency in population

• Iodine salt for goiters & folic acid for NTDs

Restore nutrients to original levels after processing

• Thiamin is added to white rice which is lost with milling

Provide balance

• Breakfast cereals to make them more nutrient dense

Prevent nutritional inferiority in food that replace traditional food

• Adding calcium & vitamin D to milk products like soy or almond

What is Micronutrient Enrichment

A type of fortification involving addition of specified amounts of sets of certain nutrients to a limited list of foods

• Set by US FDA

• Only select foods are labeled as enriched(whole grains, grain products & flour)

• Must include: 4 B vitamins(thiamin, niacin, riboflavin, & folic acid), Mineral Iron, addition of calcium optional

Anatomy of a Grain Kernel

Bran - rich in antioxidants, B vitamin, fiber

Endosperm - essential nutrients to plants; rich in starchy CHO, small amount of proteins, vitamin, & minerals

Germ - Core of seed, rich in B vitamin, protein, mineral, PUFA

What are Refined Grain

Missing one or more of their anatomical parts(bran, germ, endosperm) which impairs nutritional value

Nutrient Deficiencies of Refined Grain Consumption

Beriberi - Vitamin B1(thiamin) deficient

Pellagra - Vitamin B3 (Niacin) deficient

Role of Thiamin(B1), Riboflavin(B2), & Niacian(B3) in energy production

Act as coenzymes and assist enzyme in the release of energy from CHO, Lipids, & Proteins

• without these coenzymes, their respective enzyme cannot function

Enzymes- Apoenzyme, Catalytic site, Cofactor, Coenzyme, Holo-enzyme

Apoenzyme - protein part of the enzyme

Catalytic Site - region where enzyme interact w/substrate

Cofactor - Inorganic ion (iron, copper, zinc)

Coenzyme - nonprotein, organic molecule bound or loosely associated with the enzyme (biotin, NAD, FAD)

Holo-enzyme - active form of the enzyme (comprised of the apoenzyme and the coenzyme and/or cofactor

Thiamin(B1) role in energy production

2 phosphate groups are added to thiamin to form coenzyme thiamin diphosphate(TDP), which is essential for energy metabolism

• conversion of pyruvate into acetyl-CoA, allowing CHO metabolism to proceed into TCA 

• In TCA, TDP aids in conversion of 5C compound into a 4C compound

Where else is Thiamine found in the body

Membranes of nerve cells, where it aids in muscle activity

Thiamin (B1) Deficiency Casues

Beriberi(2 types + 1 in baby)

• Dry - damage to nervous system; muscle weakness

• Wet - damage to cardiovascular system; dilates blood vessels(edema-swollen extremities)

• infantile - observed in infants

Thiamin(B1) Toxicity

Chronic alcohol consumption can lead to B1 deficiency, a condition called Wenicke-Korsakoff syndrome

• Alcohol impairs thiamin absorption & hasten thiamin excretion in the urine

Food Sources of Thiamin

Whole grain, pork, fish

RDA & UL of Thiamin

RDA

• Women: 1.1 mg/day

• Men: 1.2 mg/day

UL

None has been determined as no adverse effects have been associated with excess thiamin

Riboflavin(B2) role in energy production

Coenzyme form of Riboflavin are Flavin Mononucleotide(FMN) & Flavin adenine dinucleotide(FAD)

• FAD picks up high energy electron from TCA(FADH2) & delievers to ETC

• FADH2 is needed for breakdown or oxidation of fatty acids into acetly CoA

Riboflavin(B2) Deficiency

Rare and typically associated with broader nutrient deficiencies & malnutrition

• Causes arbioflavinosis: inflammation of membrane of the mouth, skin, eye, and GI tract

Food Sources of Riboflavin

Meat & Dairy Products

RDA & UL of Riboflavin

RDA

• Women: 1.1 mg/day

• Men: 1.3 mg/day

UL

• No UL has been established as excess riboflavin causes no harm

Niacin(B3) role in energy production

2 coenzyme forms: Nicotinamide adenine dinucleotide(NAD) and its phosphate form NADP

• NAD carries hydrogen+electron during metabolic reactions like glycolysis and path from TCA to ETC

• NAD protects against neurological degeneration

Niacin(B3) Deficiency

Pellagra(Angry skin), which has symptoms of diarrhea, dermatitis, dementia, and death(4Ds)

• Humans can synthesize niacin from tryptophan when protein requirements have been met

Niacin toxicity

Large doses of nicotinic acid from supplements is associated with nicotinic flush

• doses 3-4x higher than RDA

• Dilates capillaries causing tingling sensation/painful

• increases plasma glucose & damages liver

Food Sources of Niacin & Conversion

Meat & mushrooms

1 NE(niacin equivalent: including precursor and nician) = 1 mg of niacin =60 mg of trptophan

RDA & UL of Niacin

RDA

• Women = 14mg/day

• Men = 16 mg/day

UL

• No more than 35 mg/day

Micronutrients for Bone Health

Vitamin D, Calcium, Vitamin K

Vitamin D - The “Sunshine Vitamin”

Conditionally essential nutrient

• produced in the skin through sunlight exposure or obtained from the diet

Vitamin D - A Prohormone

Prohormones are compounds that the body convert into an active hormone

2 Forms of Vitamin D(found as dietary supplements)

Ergocalciferol(D2)

• Plant Foods

Cholecalciferol(D3)

• Animal Derived foods

• Produced in the skin

Food Sources Containing Vitamin D(D₂ & D₃)

Cholecalciferol

• Fatty fish(salmon)

• Liver Oil

• Egg Yolk

Ergocalciferol

• Mushrooms exposed to UV light

Both(Fortified Foods)

• Dairy Products

• Breakfast Cereals

RDA & UL of Vitamin D

RDA

• Women - 600 IU=international units (15micrograms/day)

• Men - 600 IU (15micrograms/day)

UL

• 4000 IU or 100 micrograms/day

  • Overconsumption can lead to harden blood vessels, forming stones(kidney stones)

How is Vitamin D absorbed in the S.I

Same Mechanism as dietary fat

(Lipolysis-Bile-esterification-lymphatic system- chylomicrons)

Bioavailability of Dietary Vitamin D

Vitamin D is Stable & Not easily destroyed during food preparation, processing, or storage

• Drugs(Barbiturates, anti convulsants,prednisone) desotry Vitamin D

Synthesis of Cholecalciferol (D3)

Exposure of skin to UV light converts 7-dehydrocholesterol converted to previtamin D3(precalciferol) which is then converted to vitamin D(cholecalciferol)

Factors affecting Endogenous Synthesis of Vitamin D

• Seasonality, Latitude, time of day

• Age, Skin pigmentation(Darker = less Vit D)

• Amount of skin exposed, sunscreen

What happens to cholecalciferol(D3) & ergocalciferol(D2)

Liver converts D2 & D3 to 25-hydroxyvitamin D (25(OH)D) which is released into circulation and goes to the kidney

Specific enzyme in kidney converts 25(OH)D to calcitriol (1,25(OH)₂D) the active form of vitamin D and a hormone

Importance of 1,25(OH)D or calcitriol

Calcium homeostasis

Regulates Gene expression

Regulates cell differentiation

Calcium Homeostasis (low calcium levels)

Parathyroid Gland secretes Parathyroid hormones(PTH) which stimulates the conversion of 25(OH)D to 1,25(OH)₂D thereby

• increasing dietary calcium absorption

• decrease calcium excretion

• increase calcium release from bones

Vitamin D deficiency (Relatively Common)

Rickets - inadeqaute bone mineralization in early life(children) leading to softened

Osteomalacia - softening of bones due to inadequate bone mineralization in later years(adults)

Osteoprosis - demineralization of previously healthy bone; weak brittle porous bone

Calcium

Most abundant mineral in the body

• 99% is in the skeletal system

• Considered a nutrient of public health concern(underconsumed)

Food Sources of Calcium

Plants & Animal Derived Foods

Dairy Products like fortified breakfast cereal

Calcium bioavailability

Influenced by presence of anti-nutrients(decreases absorption low as 5%)

• Oxalic Acid - spinach, rhubarb, swiss chard, & beet greens

• Phytic Acid - wheat bran, legumes, seeds, nuts, & soy isolates

Functions of Calcium(5)

• Skeletal system Bone formation

• Muscle contraction

• Cell signaling

• Blood Clot Formation

• Blood Pressure regulation

Structural function of Calcium for Bone Formation

As bone begin to form, calcium salts form hydroxyapatite crystals on protein collagen matrix which makes the crystals denser and stronger

Key players in Bone remodeling

Osteoblasts - bone building(formation) cells

Osteoclasts - bone breakdown or resorption cells

Osteocytes - mature bone cells (25 year half life)

In terms of bone remodeling what is osteoporosis

Bone resorption(breakdown) > bone formation

Risk factors for Osteoporosis(5)

Early menopause = low estrogen

Family hisotry of osteoporosis

Eating disorders

Early malnutrition

Vitamin D deficiency

RDA & UL of Calcium

RDA

• Men: 1000mg/day

• Women: 1000mg/day

UL

• 2500 mg/day

• Excessive results in constipation, increased risk of urinary stones, kidney dysfunction, interference with absorption of other minerals

3 type of Vitamin K(quinone family)

K1: phylloquinone (plant foods)

K2(or MK): menaquinone (animal product, fermented foods, or by intestinal bacteria)

K3: menadione (synthetic forms used in animal feeds; humans don’t use)

Function of Vitamin K

Bone mineralization (osteocalcin(bone protein) synthesis)

• improves osteoblast functions

• inhibitory effect on bone breakdown(resorption) by apoptosis of osteoclast

Blood Clotting

Food Sources of Vitamin K

Dark leafy greens

RDA & UL of Vitamin K

RDA

• Women - 90 micrograms/day

• Men - 120 micrograms/day

UL

• No UL

What might cause deficiency of Vitamin K(rare)

Antibiotics = killing gut micrbiome therby decreasing production

Fat malabsorption syndromes

Infants given vitamin K injejections at birth

How is Dietary Vitamin K absorbed in the S.I

Same Mechanism as dietary fat

(Lipolysis-Bile-esterification-lymphatic system- chylomicrons)

Bioavailability of Vitmin K

Antibioitcs & Coumadin(warfarin)

Micronutrients for Blood Health

Vitamin K, Vitamin B12 (cobalamin), Vitamin B9 (folate), Iron

Vitamin K in Blood Clotting

Vitamin K acts as a coenzyme that activates clotting factors which convert prothrombin to thrombin

Thrombin converts fibrinogen to firbin which is the insolble protein that forms clots

What is coagulation

The rapid blood clotting of an unjured blood vessel to stop the bleeding

Explain this cycle

• Vitamin K hydroquinone (active form) is used by γ-glutamylcarboxylase (GGCX) to activate vitamin K-dependent proteins (VKDPs) by converting Glu → Gla residues.

• This reaction produces vitamin K epoxide (inactive form).

• VKOR (vitamin K epoxide reductase) recycles vitamin K epoxide back to hydroquinone.

  • Quinone reductase converts dietary vitamin K quinone into hydroquinone.

  • Warfarin (Coumadin) inhibits VKOR, blocking recycling and reducing VKDP activation → anticoagulant effect.

What are Folate (Vitamin B₉, Folic Acid)

Folate - naturally occuring form of B9

Folic Acid - synthetic form of B9 found in supplements & fortified foods

• Folic acid is more bioavailable than folate

In the body, what happen to folate

Folate is converted to tetrahydrofolate(THF), a coenzyme form that accepts one carbon units at positions 5,10, or both

Food soucres of Folate

Cereal(Fortified) with more folic acid

Factors affecting Folate amount in food

Cooked foods have less folate than raw foods

Folate is senstive to heat, light, & oxygen

RDA & UL of Folate

RDA

• Women: 400 microgram/day DFE

• Men: 400 microgram/day DFE

DFE = unit of mreasure to describe the amount of bioavailable folate in food

UL = 1000 microgram/day

Role of Folate in one carbon transfer reactions(4)

Regeneration of THF

DNA syntehsis & repair

• synthesis of building blocks of DNA and RNA(purines & pyrimidines)

Neural Tube development

• methylation as key regulator of gene expression

Amino Acid metabolism

• Hcy to Met conversion(also involes B12)

Folate Deficiency(RARE) causes

Lead to Megaloblastic macrocytic anemia(lack of O₂)

• Fatigue, weakness, headaches, pallor, SOB

Folate & Neural Tube Defects

Folate is important in the formation of neural tube and w/o folate neural tube will have improper closing leading to

• spina bifida (most common)/birth defect

• Anencepahly/birth defect & fatal

Vitamin B12 (Cobalamin) production & absorption

Vitamin B₁₂ is only produced by microorganism & humans obtain it byconsuming animal based products

Absorption is assited by Haptocorin-B₁₂ which protects from stomach acid, Intrinsic factors(IF) made by parietal cells, and IF-B₁₂(S.I) absorbed as a complex

Food Sources of Vitamin B12

Seafood(Clams) & animal product

RDA & UL for Vitamin B12

RDA

• Men: 2.4 microgram/day

• Women: 2.4 microgram/day

UL

• None

What affects aborsption of vitamin B12

Mediciation for Ulcers/GERD - H2 blockers & proton pump inhibitor

Functions of Vitamin B12(3)

ATP Production

• TCA cycle, allows the body to use amino acid & FA for energy

Amino Acid Metaolism

• conversion of homocysteine(Hcy) to methionine(Met)

Methylation(Me-X)

• Met is used to create S-adenosylmethione(SAM), the bodys primary methyl donor

• Regulation of gene expression

Vitamin B12 Deficiency(More poor absorption than inadequate intake) causes

Megaloblastic macrocytic anemia(lack of O₂)

Pernicious anemia (autoimmume disease where antibodies destory intrinsic factors

Types of Iron found in Food

Heme-Bound(animal)

• 15-40% absorbed

Non-Heme Bound(plants)

• 5-12% absorbed

NOTE: IRON Is poorly absorbed

Absorption & Metabolism of Iron

Iron must be in Fe²⁺ state or bound to heme

• Once in enterocyte, iron can be stored as ferritin or transported to circulation via ferroportin(FPN, a transmembrane transportor)

Hormonal Regulator of Iron Metabolism Conc.

High Iron Levels:

Hepcidin is released into circulation, where it binds to ferroportin, resulting in internalization & degradation of the transporter

Low Iron Levels

When Hepcidin levels are low, iron(Fe²⁺) can be released from enterocytes, where it’s oxidized into Fe³⁺ for binding to its protein carrier transferrin

Dietary compounds that inhibit/enhance iron absorption

Enhancers

• Vitamin C

• Meat factor

Inhibitors

• Phytates(corn,whole grain, legumes)

• Polyphenols(tea and coffee)

• Oxalates(spinach, berries, chocolate)

Food Sources for Iron

Clams(Animal & Plant Product)

RDA & Ul for Iron

RDA

• Women: 18mg/day

• Men: 8mg/day

Ul

• 45 mg/day

  • Excessive lead to vomiting, diarrhea, constipation, and black stools

What is Hereditary Hemochromatosis

Genetic disorder that leads to greater iron absorption

Low levels of hepcidin