VITAMINS

Vitamin A

- Dissolve in watery components of foods and the body - Excreted in urine, usually do not reach toxic levels

role in bone stability

- Vitamin D increases calcium absorption in the small intestine. Bone cells then pick up the calcium and phosphorus from the blood stream and build new bones. - Without vit. D bone cells cannot deposit enough calcium and phosphorus to produce strong bone tissue.

A drop in blood calcium

- Vitamin D works with parathyroid hormone (PTH) to signal bones to release calcium. - How so? • PTH stimulates the kidneys to increase vitamin D production and decrease the elimination of calcium in urine.

reasons for variable vitamin absorption

-Your body's physiological need for it. Mostly dictated by age and gender. - How the food was prepared: raw vs. cooked. - Synthetic vs. non-synthetic vs. processed foods. - The combination of the foods you ate

uses for Vitamin D

-bones stimulates epithelial cells of the small intestine to absorb more calcium and phosphorus from food. • When vitamin D is lacking, the intestine absorbs only 10% to 15% of the calcium in foods; • with the vitamin, absorption increases to 30% to 80%.

Vitamin D

-rickets Vitamin D is not widespread in food, therefore your body depends on sun exposure • The amount of sun depends on: geographic location, time of day and year, age and skin color

are there undiscovered vitamins?

1. Babies grow and thrive on infant formulas, 2. Very ill people who cannot eat solid food can be kept alive for years on liquid synthetic feedings. If a vitamin remained undiscovered, infants and people who are unable to consume solid foods would not be able to survive on formula diets.

water soluble (list)

1. Thiamin 2. riboflavin 3. niacin 4. B-6 5. B-12 Water-soluble vitamins 6. Folate 7. C, ascorbic acid 8. pantothenicacid 9. biotin

how the body makes Vitamin D (six steps)

1. When skin cells are exposed to the sun's ultraviolet (UV) radiation the radiation converts a substance that is derived from cholesterol into an inactive form of vitamin D called vitamin D3 2. Vitamin D3 is then released into your blood stream. 3. It finds its way eventually to the liver. 4. The liver converts it into another inactive form (25- OH vitamin D3) and releases it again into the bloodstream. 5. It finds its way eventually to the kidneys. 6. Eventually, the kidneys convert 25-OH vitamin D into the active form we call "vitamin D"

fat soluble (list)

10. A 11. D 12. E 13. K

Vitamin B-6

A coenzyme for >100 enzymes. In other words, it is VERY important! Needed for amino acid metabolism • **Without vitamin B-6, all amino acids become essential. ** • conversion of the amino acid tryptophan to niacin • Conversion of a toxic amino acid, homocysteine, tocysteine, a nonessential amino acid Required for synthesis of the heme in hemoglobin • Hemoglobin-the oxygen carrying protein in our blood. A few others 3. Water soluble vitamins An essential a.a • Conversion of toxic, homocysteine, to cysteine - If the body lacks vitamin B- 6, homocysteine can accumulate in blood -may contribute to CVD. - Folate and vitamin B-12 also participate in homocysteine metabolism. A nonessential a.a 62 3. Water soluble vitamins Vitamin B-6: Required for synthesis of heme in hemoglobin • During red blood cell (RBC) production, the B-6 coenzyme participates in the synthesis of heme. - Heme is a compound found on the hemoglobin. Without heme, hemoglobin cannot carry O2. - If vitamin B-6 is unavailable for heme synthesis, anemia develops. - (Note: this is the first case of anemia that I mention. Anything that compromises your red blood cells ability to carry the maximum load of oxygen will lead to anemia. Symptoms of anemia range from general weakness/fatigue to cardiac arrest) hemoglobin 63 • Given its importance in protein metabolism, it is suggested that dietary adequacy be based on protein intake. - Luckily, meat has plenty of B-6 • Unlike most B vitamins, megadoses of vitamin B-6 are toxic. 3. Water soluble vitamins 64

Thiamin (B1)

A coenzyme needed for macronutrient metabolism The body stores very little thiamin -deficiency symptoms can occur within a few days of a thiamin-deficient diet. • Thethiamin-deficiencydiseaseiscalledberiberi. • Symptoms: weakness, memory loss, weight loss. (beri-beri means "I cannot" • Thiamin deficiency can also occur from alcoholism - CalledWernicke-Korsakoff.Thishappensbecausealcoholinterfereswith thiamin absorption. Can lead to permanent brain damage.

definition of a vitamin

A complex organic compound, Vitamins generally meet the following criteria: 1. The body cannot synthesize it — or make enough to maintain good health 2. Naturally occurs in common foods 3. Deficiency condition occurs when the vitamin is missing from the diet 4. Good health is restored, if deficiency disorder is treated early by supplying the missing substance

Factors affecting vitamin D synthesis

Air pollution -film of particles block out sun rays • City living -tall building block sunlight • Geography -see next slide • Homebound • Clothing • Season • Sunscreen • Skin color (darker skin requires up 3 times more sun exposure) • Time of day

antioxidants and Vitamin E

Antioxidants protect cells by giving up electrons to radicals. - By sacrificing electrons, antioxidants protect molecules such as polyunsaturated fatty acids in the membrane or DNA in the nucleus from being oxidized. • Vitamin E is also added to food to prevent oxidation (ie prevent the food from going rancid). • Vitamin E protects LDLs from being oxidized thus lowering risk of CVD

coenzymes (B-vitamins)

activate inactive enzymes, Once the coenzyme binds, the enzyme changes shape and is now active. The activate enzyme can now catalyze a chemical reaction -e.g. break down carbohydrates to give energy Vitamins are not metabolized for energy... but they participate in the chemical reactions that produce energy • In short, the chemical reactions that involve the metabolism of carbohydrates, fats, and amino acids require B-vitamins. • TheseB-vitaminsworkascoenzymes. - (think of coenzymes as co-workers with enzymes)

uses of Vitamin A

gene expression, vision, maintenance of body lining and skin, reproduction, ... - Maintenance of body lining and skin: Vitamin A is crucial for production and maintenance of epithelial cells.

Vitamin D Toxicity

• Excess vitamin D can cause the small intestine to absorbs too much calcium from foods. - the mineral is deposited in soft tissues, including the kidneys, heart, and blood vessels. - Of course this can happen with taking vitamin D supplements.

Pantothenic Acid and Biotin

Both are coenzymes that are involved in energy metabolism. • Deficiencies are rare • Biotin... - Bacteria in the large intestine synthesize biotin. Some of our biotin needs are met by the work of our friendly microbes.

carotenoids

But plants contain hundreds of yellow-orange pigments called carotenoids. One such carotenoid is beta-carotene. Beta-carotene is a provitamin -a vitamin A precursors. The body can use beta-carotene to make retinol.

Vitamin C

Collagen Synthesis - Collagen is a fibrous protein that gives strength to connective tissue (bone, teeth, skin, tendons, blood vessels). • Symptoms of scurvy (vit. C deficiency): - Petechiae (pinpoint hemorrhages in skin), skin bruises easily, gums swell and become spongy, bleeding gums, teeth loosen and fall out, opening up of old scars ... infection. - Nearly half of the sailors whose tout on long voyages would die of infection that was cause by scurvy. 81 3. Water soluble vitamins Other functions of Vitamin C - Antioxidant power • vitamin C acts as an antioxidant by donating electrons to radicals. • It is the water-soluble antioxidant. • Vitamin C also may donate electrons to another antioxidant—vitamin E. Thus, vitamin C recycles vitamin E so that it can regain its antioxidant function.

Vitamin E

Eight forms of vitamin E. But alpha-tocopherol is the most active form. This is the form reflected in DRI tables. • Vitamin E easily destroyed by cooking. • Vitamin E is the major fat-soluble antioxidant found in cells. - It donates an electron to free radicals - The vitamin protects polyunsaturated fatty acids in cell membranes from being damaged by radicals.

fat soluble

Fat-soluble: A, D, E, K - chemically similar to lipids - bile enhances fat-soluble vitamin absorption - Packaged inside chylomicrons - Do not dissolve in water or urine and are stored in the body - May reach toxic levels

Folate

Folate is the name for a group of related compounds - Folic acid is the synthetic form found in supplements and added to fortify foods. - In the body, cells convert all forms of folate to folate- coenzymes . • Conezymesparticipatein: - DNA metabolism. • folate-containingcoenzymesareneededtosynthesizeDNA. - Amino acid metabolism - Conversion of homocysteine to methionine. 65 • Folate deficiency affects cells that rapidly divide, • And when to we have rampant DNA synthesis? - During embryonic development.

Vitamin K

Important for the synthesis of blood-clotting factors in the blood. Without vitamin K you could bleed to death from a minor cut. About 10% of our vitamin K is synthesised by the bacteria living in our large intestine. • The rest comes from the diet. (mostly dark leafy greens)

Digestion and absorption of water-soluble vitamins

In the stomach, vitamins are released from protein complexes in food. - (B-12 is quite different) • The vitamins are absorbed by the small intestine and delivered to the liver via the portal vein • Vitamins are then release into the general blood circulation - (Liver keeps/stores B-12) • Excess water-soluble vitamins are eliminated through the kidneys in the urine.

Riboflavin (B2)

Major Functions in the Body 3. Water soluble vitamins - A coenzyme needed for macronutrient metabolism • Exposure to light causes the vitamin to break down rapidly. • Riboflavin-rich foods, (e.g. milk) should not be packaged or stored in clear glass containers. • (30 minutes of UV light will destroy 30% of riboflavin) What happens if riboflavin is missing from the diet? - Fatigued easily. - Inflamed tongue, sores on the edges of the lips - But deficiency is very rare.

Vitamin Absorption

Most absorption occurs in small intestine - Absorption is not 100% efficient. - Absorption generally increases when more of the vitamin is needed. Example during: • Growth (e.g., during infancy and adolescence) • Pregnancy • Breast-feeding (milk production)

Mutagen Carcinogen Teratogen

Mutagen = an agent that causes a mutation in DNA Carcinogen = an agent that causes a mutation in DNA that leads to cancer Teratogen = an agent that causes a mutation in the DNA of a developing foetus causing mild to severe birth defects.

lutein, zeaxanthin and lycopene

Other carotenoids = lutein, zeaxanthin and lycopene • Green, leafy vegetables, (eg spinach and kale) have high concentrations of lutein and zeaxanthin. • Tomato juice/ tomato products, contain considerable amounts of lycopene. • the body does not convert them to vitamin A. - These plant pigments function as antioxidants in the human body. - Also, in reducing the probability of macular degeneration (deterioration of the retina as you age. Leading cause of blindness in elderly)

Vitamin B-12

Part of coenzymes that - Assist in DNA synthesis - homocysteine metabolism. - maintaining the myelin sheaths that insulate parts of certain nerve cells. • Without vitamin B-12, segments of myelin sheath gradually undergo destruction that can lead to paralysis.

Food Sources of Vitamin B-12

Plants do not make vitamin B-12; - We rely almost entirely on animal foods to supply B-12

preformed vitamins

Preformed vitamins are found in food that are usable my the body -without chemical transformation.

provitamins

Provitamins are vitamin precursors that do not function in the body until converted to active forms • Beta-carotene is precursor to vitamin A • Tryptophan (amino acid) is a precursor to niacin One way to remember: think of provitamins as vitamin prototypes.

RBCs and Folate megaloblasts megaloblastic anemia

Red blood cells (RBCs). • RBCs live for about four months. The bone marrow is constantly replacing old or worn-out RBCs. • Without folate, RBC precursor cells that reside in bone marrow enlarge, but they cannot divide normally, because they are unable to form new DNA. • The bone marrow releases abnormal RBCs called megaloblasts into the bloodstream • Megaloblastic anemia, is characterized by large, immature RBCs. Because they are abnormal in shape they do not carry the normal amounts of oxygen.

Vitamin D Deficiency

Rickets still a major concern in developing countries. • But note, breast milk contains insufficient amounts of vitamin D to prevent rickets. - Exposingbreast-fedinfantstosunlightreducestheirriskofthedisease, but medical experts do not know how much sun exposure is necessary. - In 2000,a medical research group published a disturbing report documenting a rise in the incidence of rickets, especially among dark- skinned, breastfed babies. • The adult form of rickets = osteomalacia. - Symptoms include diffuse bone pain and muscle weakness. Increased risk of bone fractures. - Inadequate vitamin D intake can also result in the demineralization of previously healthy bone, ultimately leading to osteoporosis .

absorption of B-12`

The natural vitamin B-12 in food is bound to proteins that prevent its absorption. - Hydrochloric acid and pepsin in the stomach release B-12 from the protein • (Synthetic vitamin B-12 in dietary supplements or fortified foods is not bound to proteins, so it does not need stomach acid and pepsin to release it from foods. Thus, synthetic vitamin B-12 is more readily absorbed than the natural form of the micronutrient). 72 3. Water soluble vitamins • Before entering the small intestine, - vitamin B-12 binds with intrinsic factor (IF), a compound produced by certain stomach cells. - Now the "vitamin B-12/intrinsic factor complex" reaches the ileum where the vitamin is absorbed. 73 • Once absorbed and transported to the liver via the portal vein, the liver removes about 50% of the vitamin for storage. - A healthy liver has enough vitamin B-12 reserves to last up to 5 years.

birth defects and use of folic acid in foods

The two neural tube defects are: 1. Spina bifida: tube fails to close properly. Infants born with protrusion of spinal cord outside the body. Defects range from very minor to extreme (paralysis). 2. Anencephaly: Infants born with have much of their brain malformed or missing, and they usually die shortly after birth. Because of the importance of folate for optimal embryonic development and growth, in Canada, - ALL wheat flour is fortified with folic acid. Thus, bread products in Canada are generally good sources of folic acid. • In 1996: 0.77 per 1,000 live births had neural tube malformations. • Since fortification became mandatory: decrease by 46%.

vitamin K and babies

Vitamin K deficiency occurs in some infants. • Newborn have a sterile large intestine. It takes weeks to build up bacteria capable of synthesizing vitamin K. Infants are at risk of bleeding to death/ • All newborns are given a single dose of vitamin K at birth.

Vitamins B/C

Water-soluble B-vitamins 1. Thiamin 2. Riboflavin 3. Niacin 4. B-6 5. Folate 6. B-12 7. Pantothenic 8. Biotin Other water-soluble vitamin C

water soluble

Water-soluble: B's and C - Dissolve in watery components of foods and the body - Excreted in urine, usually do not reach toxic levels

Vitamins

micronutrient, the body requires vitamins in milligram (mg) or microgram (mcg, mg) amounts,

sources of vitamins

natural sources Plants, animals, fungi, and bacteria • Synthetic - Made in laboratories by chemists. - Synthesized by microbes in laboratories and extracted for commercial use • Enrichment - addition of vitamins and minerals to food products to replace those lost during processing or refinement • Fortification - addition of supplementary nutrients to food

are vitamins a source of energy?

no, - cells do not metabolize vitamins for energy. participate in the chemical reactions that release energy from glucose, fatty acids, and protein.

Niacin (B3)

• Niacin is part of two coenzymes that participate in at least 200 reactions, including those involved in the release of energy from macronutrients! • We can produce some small amounts of niacin using one of the amino acids. - The amino acid is tryptophan. The ratio is 60mg:1mg. Thus niacin must be supplied by the diet. 58 • What happens if niacin is missing from the diet? - Pellagradisease 1. Dementia 2. Dermatitis 3. Diarrhea 4. Death Initially considered an infectious disease. Breakthrough came through the observation that prison inmates fed a low protein diet developed pellagra. Prison guards did not develop pellagra. Furthermore, prison inmates in other states, who were fed some milk did not develop pellagra. Discovery was made by Dr. Goldberger. 3. Water soluble vitamins 59 3. Water soluble vitamins Niacin is found in corn • Prison inmates ate corn. So why did they develop pellagra? • The niacin content in corn is high, but is tightly bound to a protein that resists digestion. - Thus, people who eat corn as their staple food are prone to develop pellagra. - But while pellagra raged in the 1900s throughout the US, Mexico was immune. • Why? In Mexico, corn kernels are soaked in lime water before making tortillas. Thus- the acid in lime helps free the niacin from the protein and enhancing its ability to be absorbed.

B-12 Deficiency

• Pernicious Anemia • Some people have a genetic defect that reduces their ability to produce intrinsic factor. • Eventually, develop pernicious ("deadly") anemia. - This condition is characterized by nerve damage and megaloblastic RBCs. Intrinsic factor and hydrochloric acid production decline with aging. - ≈ 15% of people >60 years of age are vitamin B-12 deficient.

Vitamin A Toxicity

• Vitamin A is stored in the liver • Excessive consumption of vitamin A = damaged the liver • Caused by excessive consumption of preformed vitamin A (ie from animal sources) • Most often the result of taking supplements. Pregnant women should not take vitamin A supplements. - Excess vitamin A is a teratogen, an agent that causes birth defects.

oxidizing agent or oxidant/free radical

• When many biochemical reactions take place, the compounds participating in the reactions lose or gain electrons. - When an atom or molecule gains one or more electrons, it has been reduced. (we say reduced because it became more negative) - When an atom or molecule loses one or more electrons, it has been oxidized. (we say oxidized because it became more positive) • An oxidizing agent or oxidant is a substance that removes electrons from atoms or molecules. • An oxidation reaction can form a free radical • A radical a substance with an unpaired electron. • Radicals are highly reactive. They remove electrons from more stable molecules, such as proteins, fatty acids, and DNA. - Therefore,radicalscandamageordestroythesemolecules. ***Many medical researchers suspect excess oxidation to be responsible for changes in cells that ultimately lead to heart attack, stroke, cancer, Alzheimer's disease, and even the aging process. ***