Nutrition Mt 2 Water Soluble Vitamins

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Water Soluble Vitamins General Properties:

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Vitamin C and the B complex vitamins

cooking and washing with water causes the vitamins to leech out.

they are easily absorbed

excess excreted in the urine (no toxicity from food).. toxic levels can be reached from oversupplementation though

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B vitamins overview:

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-the B vitamins act as coenzymes: small molecules that combines with and activates enzymes.

-the B vitamins are all involved in the metabolism of carbs, lipids, and amino acids

-thiamin, riboflavin, niacin, panthothenic acid, and biotin are all necessary cofactors in energy metabolism (deficiencies show up in quickly growing tissues)

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B vitamins and the nervous system:

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since the nervous system uses a lot of energy, deficiency of the energy releasing vitamins commonly show up in nervous tissues:
1. depression
2. mental confusion
3. lack of motor coordination
4. malaise

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Role of Thiamin (B1)

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1. energy metabolism
2. nerve processes

*thiamin is essential in converting blood sugar into energy and is involved in metabolic activities in nerves, heart, and muscles, and in the production of red blood cells

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Thiamin deficiency

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thiamin deficiency is called Beriberi

symptoms: impairment of the cardiovascular system, nervous system, and gastrointestinal system

*beriberi can occur in alcoholics and severely malnourished people

Wet Beriberi: edema, acute cardiac symptoms

Dry Beriberi: Neurological disorders and muscle wasting (no edema)

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Wernicke-Korsakoff Syndrome

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alcohol abuse with severe thiamin deficiency (alcohol displaces food in the diet, impairs thiamin absorption, and promotes thiamin excretion in urine)

*most common neurological problem in alcoholics

-weakness of eye movement and mental disturbance

****Responds dramatically to thiamin administration

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Thiamin Sources:

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pork products, leafy green vegetables, whole grain cereals, legumes

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DRI for thiamin

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men: 1.2 mg/day
women: 1.1 mg/day (higher if pregnant or lactating)

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Role of Riboflavin (B2):

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energy metabolism of all cells

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Riboflavin deficiency

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usually occurs along with a deficiency of other B vitamins... since it usually occurs with a thiamin deficiency, it may go undetected (thiamin deficiency symptoms are more severe)

Ocular Symptoms: eye strain, sensitivity to light, etc.

Characteristic lesions of the lips, the most common of which is Cheilosis (cracks at the corners of the mouth)

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Dietary Sources of Riboflavin

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milk and milk products
leafy green vegetables
whole-grain breads
fortified cereals
some meats

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role of Niacin

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energy metabolism

Niacin, also known as nicotinic acid, helps break down blood sugar for energy and also acts as a vasodilator, widening blood vessels and increasing blood flow.

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Niacin Deficiency

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Pellagra

symptoms: dermatitis, diarrhea, depression, death (the 4 D's)

those at risk: poorly nourished people living in urban slums (particularly alcoholics)
-still common in parts of Africa and Asia

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Sources of Niacin:

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part of the niacin requirements is met by the synthesis of niacin from tryptophan (thus a person eating adequate protein will not become niacin deficient)

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Dietary sources of niacin:

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mackerel, swordfish, chicken, veal, fortified cereals, pork, salmon, and beef liver

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Niacin Toxicity

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large doses of niacin are associated may be part of a treatment to lower blood lipids associated with cardiovascular disease

large doses of niacin can injure the liver, cause peptic ulcers, and cause vision loss

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Niacin flush

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certain forms of niacin supplements in amounts 2-3X the recommendation can cause niacin flush: dilation of the capillaries of the skin with perceptible tingling that can be painful

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Role of Vitamin B6 (Pyridoxine)

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-100+ reactions in the tissues
-needed to convert one kind of amino acid into other non-essential amino acids
-aids in the conversion of tryptophan to niacin
-hemoglobin synthesis
-neurotransmitter synthesis (aids in the conversion of tryptophan into serotonin)
-assists in the release of stored glucose from glycogen (contributes to regulation of blood glucose)
-immune function
-steroid hormonal activity
-fetal brain and nervous system development (deficiency during this stage causes behavioral problems later)

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Three symptoms of Vitamin B6 deficiency

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1. central nervous system damage (due to insufficient neurotransmitter synthesis)
2. anemia
3. pellagra (causes low body synthesis of niacin from tryptophan)

*deficiency is very uncommon

Deficiency is associated with increased levels of the chemical homocysteine, which is turn has been associated with heart disease, birth defects, and possibly Alzheimer's disease and dementia.

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Vitamin B6 requirement:

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due to its role in protein metabolism, our need for B6 is proportional to our protein intake

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Dietary Sources of vitamin B6

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protein rich foods (meats, fish, poultry)
potatoes, leafy green vegetables, some fruits
legumes and peanut butter

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Vitamin B6 toxicity

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toxicity in humans has been described when taken at extremely high doses

symptoms: impaired gait, loss of nerve sensation in extremities

UL: 0.1g

women who took 2+ grams/day for 2 months in a mistaken attempt to cure PMS symptoms experienced:
-numb feet
-no sensation in hands
-eventually unable to walk
*they recovered after they stopped taking the supplements

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Role of Folate

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1. DNA synthesis
2. Metabolism of several amino acids
3. Used in the manufacture of neurotransmitters

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Folate Deficiency:

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Because red and white blood cells and cells of the GI tract divide rapidly, they are most vulnerable to a deficiency.

-Megaloblastic Anemia (related to anemia of vitamin B12 malabsorption)
-Diminished immunity
-Abnormal digestive function

Increased Risk for:
-cardiovascular risk
-colon cancer risk
-cervical cancer risk

Most common cause of folate deficiency: alcoholism and poor diet

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Folate and neural tube defects:

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neural tube defects include: damaged spinal cord, cleft palate, mental retardation, severely diminshed brain size, death shortly after birth...

Most women consume too few fruits and vegetables to supply even 50% of necessary folate to prevent such defects.

all women of child-bearing years should be taking folic acid (must be taken BEFORE a women becomes pregnant)

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is natural folate more readily absorbed than synthetic folate?

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no. actually, synthetic folic acid is most readily absorbed.

many foods are enriched with folic acid

the unit of measure for folate is DFE (dietary folate equivalent)

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Dietary sources of folate:

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-leafy green vegetables
-fresh, uncooked vegetables and fruits (the heat of cooking and oxidation that occurs during storage destroys much of the folate)
-eggs
-orange juice
-legumes
-milk may enhance folate absorption

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DRI for Folate:

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400ug/day

*women in childbearing years: 400ug of folic acid supplement in addition to the dietary folate that naturally occurs in food.

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Folate Toxicity

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UL is set at 1,000 ug

folate can mask vitamin B12 defiency

excess folate can be antagonistic to the actions of some anticancer drugs

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Folate and its interaction with other drugs:

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of all the vitamins, folate is most likely to interact with medications

antacids, aspirins (and its relatives), oral contraceptives, anticonvulsants, and smoking interfere with the body's use of folate
*occasional use of these drugs is okay, but frequent users need to pay attention to their folate intake.

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Role of Vitamin B12 (Cobalamine)

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1. essential for manufacturing DNA
2. vitamin B12 is activated by folate, folate is activated by vitamin B12
3. needed for production of blood cells
4. required for healthy functioning of the nervous system (maintenance of the sheaths that surround and protect the nerve fibers).

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How do we get vitamin B12 in a functioning form?

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B12 usually occurs bound to protein in food

to be utilized, B12 must first be removed from the protein (by acid in the stomach)

must combine with intrinsic factor (protein secreted by the stomach that carries B12 to the intestine to be absorbed)

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Vitamin B12 deficiency

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-Deficiency results in failure of folate to make red blood cells...
Therefore, a vitamin B12 deficiency causes an anemia (pernicious anemia) identical to that of folate

Large, immature red blood cells

Treatment: administration of folate... However, this allows the deficiency of B12 to continue undetected

Deficiency also leads to:
1. damaged nerve sheaths
2. creeping paralysis
3. general malfunctioning of nerves and muscles

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Absorption of vitamin B12 in old age.

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As people age, many people lose the ability to produce sufficient stomach acidity and intrinsic factor (leaving them vulnerable to chronic stomach infections and reduced ability to absorb vit. B12)

the elderly may require synthetic vit. B12 supplementation or injections

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who is at risk for B12 deficiency?

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vegetarians and the elderly
*esp. people who rely heavily on grain products (the folate enrichment of grains can mask B12 deficiency) and who consume little or no animal products.

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Folate and B12's function together:

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these two vitamins are important for the production of neurotransmitters

deficiencies in these vitamins have been observed in people with depression and dementia

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Sources of B12

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foods of animal origin
there is NONE in foods from plants

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Role of Panthothenic Acid

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**energy metabolism

plays a roll in the 100+ steps concerened with the synthesis of lipids , neurotransmitters, and hemoglobin

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deficiency of panthothenic acid?

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has not been observed
readily avaiable in most food

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Role of Biotin

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*energy metabolism

cofactor for several enzymes in the metabolism of carbs, fat, protein

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Sources of Biotin

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is present in most food

also synthesized by intestinal flora

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Symptoms of Biotin deficiency:

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-hair loss
-dermatitis
-muscle pain
-hypercholesteralemia
-heart abnormalities

*deficiency is rare (observed in people with long term antibiotics and people who consume large quantities of raw eggs.. raw eggs contain protein "Avidin" which binds biotin and prevents its absorption.. this protein is denatured in cooked eggs though)

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Biotin Toxicity

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There is no toxicity for biotin

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Functions of Vitamin C (Acsorbic Acid)

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1. antioxidant
2. required for the synthesis of stress hormones (epinephrine and norepinephrine)
3. in the intestines, prevents iron from oxidation (thus promoting its absorption)
4. protects vitamin A, vitamin E, and some B vitamins in the body from oxidation
5. cofactor in the production of carnitine (plays a role in transporting fatty acids within cells
6. in the blood, protect blood constituents form oxidation and protects and recycles vitamin E

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vitamin C and collagen:

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another role of vitamin C is the formation and maintenance of collagen (the primary connective tissue in the body)

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Dietary Sources of Vitamin C

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best sources are fruits and vegetables

although most animals can produce their own vitamin C, humans need to obtain their supply from food

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Symptoms of mild Vitamin C deficiency:

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1. large areas of bleeding into the skin
2. corkscrew hairs
3. small pinpoint hemorrhages in the skin

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Symptoms of severe vitamin C deficiency:

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= Scurvy
1. decreased wound healing
2. osteoporosis
3. bleeding into the skin
4. Anemia
5. bleeding gums (gingivitis)

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Those at risk for vitamin C deficiency:

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200+ years ago people on long sea journeys developed scurvey.. began to have lime juice to prevent it

today...
risk in N.A. is low
-some elderly with little fruit/vegetable intake and poor diet may be at risk
-those addicted to alcohol and drugs
-infant's fed cow milk (breast milk and formula provide sufficient vitamin C).

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Vitamin C and the common Cold

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misconception that vitamin C can prevent the common cold

there has been research however that has shown a reduction in duration and severity of cold symptoms.. this is possibly due to vitamin C's action against histamine (which causes runny nose, sneezing, headache).. in this sense, near vitamin C's UL (2g) it can act as a weak antihistamine.

also its antioxidant properties can support the immune function of the body

however.. the "placebo effect" occurred in these studied.. a group w/ placebo claimed they got fewer colds than the group w/ vitamin C who thought they had the placebo.

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Recommendations for vitamin C.

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DRI:
male: 90 mg
female: 75 mg

body's pool of vitamin C is full around 100mg

since smoking produces oxidants that deplete vitamin C smoker's recommendations are as follows:
male: 125 mg
female: 110g

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Excessive intake of vitamin C leads to...

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-Diarrhea
-abdominal cramps
-nausea
-interference with drug action and diagnostic tests (may interfere w/ blood clotting meds)
-conditional scurvy