Chapter 8
The Water-Soluble
Vitamins
Vitamin Talk
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Vitamins are organic compounds essential in
the diet to promote growth and health
maintenance.
Water-soluble vitamins include the B
vitamins and vitamin C.
Fat-soluble vitamins include A, D, E and K.
B vitamins were originally thought to be one
chemical substance but are actually many
different substances. That is the reason for
B1, B2, B12, etc.
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The Vitamins
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Finding Vitamins in Foods
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Fortified and Enriched Foods
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Fortification: process of adding nutrients to
foods. The added nutrients are generally not
found in the food, such as fortifying orange
juice with calcium.
Enrichment: adding nutrients back to foods
that have lost nutrients due to processing.
An example is the addition of B vitamins to
white rice.
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Dietary Supplements
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Dietary supplements can be another source
of vitamins in the modern diet.
Dietary supplements contain some
combination of vitamins, minerals, herbs,
botanicals, amino acids, enzymes or
extracts.
Dietary supplements cannot replace the
benefits of a diet containing a wide variety of
foods.
Dietary supplement production is not
supervised by the FDA.
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Absorption
of Vitamins
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Bioavailability of Vitamins
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Vitamins must be absorbed by the body in order to
perform their functions.
Approximately 40-90% of vitamins are absorbed in
the small intestine.
Fat-soluble vitamins require fat in the diet to be
absorbed.
Water-soluble vitamins may require transport
molecules or specific molecules in the GI tract.
Some vitamins are absorbed in inactive provitamin
or vitamin precursor forms that must be converted
into active forms by the body.
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Thiamin
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Thiamin was the first B vitamin to be
identified and is also called B1.
Thiamin is widely available in foods,
especially in enriched grains, whole grains,
legumes, nuts and seeds.
Thiamin assists in energy production,
carbohydrate metabolism, the production of
ribose and the health of the nervous system.
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Thiamin
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Riboflavin
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Dairy products are a good source of riboflavin.
Plant sources of riboflavin include mushrooms, broccoli,
asparagus, whole grains and green, leafy vegetables.
Animal sources include red meat, poultry and fish.
Riboflavin is easily destroyed by heat and exposure to
light.
Riboflavin is an important component in the citric acid
cycle and for assisting the body with the absorption of
other vitamins.
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Riboflavin
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Niacin
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Niacin is added to enriched flours in North America.
A niacin deficiency disease is pellagra.
Niacin can be synthesized in the body from the
essential amino acid tryptophan if the diet is adequate
in tryptophan.
Niacin plays an important role in the production of
energy and in general metabolism.
Two forms of niacin are nicotinic acid and
nicotinamide.
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Niacin
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Niacin
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Advanced pellagra’s symptoms include the 3
D’s: dermatitis, diarrhea and dementia.
Niacin toxicity from overuse of niacin
supplements can result in elevated blood
pressure, cardiac arrhythmia, nausea,
vomiting, elevated blood sugar levels and
impaired liver function.
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Pantothenic Acid
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Vitamin B6
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Vitamin B6
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Vitamin B6 is also called pyridoxine and
comprises a group of compounds including
pyridoxal, pyridoxine, and pyridoxamine.
All three forms can be converted into
pyridoxal phosphate, which is required for
many enzyme reactions in the body.
Vitamin B6 deficiency may result in anemia
due to impaired hemoglobin synthesis and
neurotransmitter issues.
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Folate or Folic Acid
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Folate or Folic Acid
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Folate coenzymes are needed for DNA
synthesis and the metabolism of some
amino acids.
Low folate intake in early pregnancy is
associated with an increased risk of neural
tube defects.
Low folate intake has been associated with
an increased risk of heart disease related to
the metabolism of the amino acid
homocysteine.
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Folate Deficiency and Neural Tube
Defects
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Macrocytic Anemia and Folate
Deficiency
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Calculating Dietary Folate Amounts
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Vitamin B12
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Vitamin B12
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Pernicious anemia is a form of anemia that does not
respond to iron supplementation.
Vitamin B12 is necessary for the proper absorption of
iron in the body.
Excessive intake of folic acid can mask B12 deficiencies.
Vitamin B12 is most readily absorbed from animal
products.
Vegan diets need to be supplemented with readilyabsorbable forms of B12.
Atrophic gastritis may lead to B12 deficiencies.
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Absorption
of Vitamin
B12
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Vitamin C
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Vitamin C
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Vitamin C is also known as ascorbic acid or
ascorbate.
Vitamin C in foods can be destroyed by
oxygen, light and heat, as well as contact
with copper or iron cookware.
Vitamin C functions as an antioxidant in the
body, helps maintain the immune system, is
important in the production of collagen and
aids in iron absorption.
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How Antioxidants Work
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Summary of Water-Soluble Vitamins
and Choline
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Benefits and Risks of Water-Soluble
Vitamin Supplements
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Chapter 8
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