Chapter 7 Vitamins. Copyright 2010, John Wiley & Sons, Inc. Water-Soluble and Fat-Soluble Vitamins.

Chapter 7Vitamins

Copyright 2010, John Wiley & Sons, Inc.

Water-Soluble and Fat-Soluble Vitamins


Vitamins in MyPyramid


Vitamin Talk Vitamins are organic compounds essential in

the diet to promote growth and 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 many different substances. That is the reason for B1, B2,

B12, etc.


Fortified and Enriched Foods

Fortification: the process of adding nutrients to foods. The added nutrients are generally not naturally 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.


Keeping Vitamins in Your Food


Absorbing Vitamins


Bioavailability of Vitamins

Vitamins must be absorbed by the body in order to perform their functions.

Approx 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.


Vitamin Functions


Vitamins as Coenzymes


Free Radicals, Antioxidants and Vitamins


Vitamins on Food Labels


Water-Soluble Vitamins: Thiamin 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.


Thiamin


Riboflavin

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 assists the body with the absorption of other vitamins.


Riboflavin


Niacin 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.


Niacin

Symptoms of advanced pellagra include the 3 D’s: dermatitis, diarrhea and dementia.

Niacin toxicity from overuse of niacin supplements can result in elevated blood pressure, cardiac arrhythmias, nausea, vomiting, elevated blood sugar levels and impaired liver function.


Niacin


Vitamin B6

Also called pyridoxine, a group of compounds including pyridoxal, pyridoxine, and pyridoxamine.

All three forms can be converted into pyridoxal phosphate, required for many enzyme reactions in the body.

Deficiency may result in anemia, due to impaired hemoglobin synthesis and neurotransmitter issues.


Vitamin B6


Vitamin B6


Vitamin B6


Folic Acid (Folate)

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.


Folic Acid and Neural Tube Defects


Folate Deficiency and Anemia


Interaction of Folic Acid and Vitamin B12


Folic Acid in the Diet


Vitamin B12 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 readily-

absorbable forms of B12.

Atrophic gastritis may lead to B12 deficiencies.


Absorption of B12


B12 on the Menu


Vitamin C

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 through 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.


Vitamin C on the Menu


Summary of Water-Soluble Vitamins and Choline


Summary of Water-Soluble Vitamins and Choline


Fat-Soluble Vitamins Vitamins A, D, E and K are fat-soluble vitamins. Fat-soluble vitamins require bile and dietary fat

for absorption. Once absorbed, they are transported with fats

through the lymphatic system in chylomicrons before entering the blood.

Fat-soluble vitamins can be stored in body fat, meaning that intakes can vary without a risk of deficiency (as long as there are average intakes over time) and they are not easily excreted. This increases the risk of toxicity with high intakes.


Vitamin A Vitamin A is found preformed (from animal

products or supplements) or in precursor form (from plant foods) in the diet.

Vitamin A plays a key role in night vision, cell differentiation and growth regulation.

Preformed vitamin A compounds are known as retinoids.

Plants contain precursors to vitamin A known as carotenoids.

A derivative of retinoic acid is used topically to treat certain skin conditions.


Vitamin A on the Menu


Vitamin A and the Visual Cycle


Vitamin A Deficiency and Toxicity Vitamin A deficiency is a threat to the health,

sight and lives of millions of children around the world.

Vitamin A deficiency can be caused by insufficient intake of vitamin A, fat, protein or zinc.

Preformed vitamin A can be toxic if taken in high amounts.

Medications made from vitamin A, such as Retin A or Accutane, can cause serious side effects.


Vitamin D

Vitamin D is known as the “sunshine” vitamin because it can be produced in the skin by exposure to UV light.

Only a few foods are natural sources of Vitamin D, including liver, fatty fish, fish oils and egg yolks.

Vitamin D can be toxic at high levels, so there are strict limitations on the categories of foods that can be vitamin D-fortified.

Vitamin D is important for bone health, normal functioning of the parathyroid gland and regulation of the immune system.


Vitamin D Activation


Vitamin D Deficiency and Toxicity

When vitamin D is deficient, dietary calcium cannot be absorbed efficiently and there can be improper bone mineralization and abnormalities in bone structure.

In children, vitamin D deficiency can result in rickets; in adults, osteomalacia.

Oversupplementation of vitamin D can result in high blood and urine calcium concentrations, depositing of calcium in blood vessels and kidneys, cardivascular damage and possibly death.


Vitamin D on the Menu


Vitamin E

Vitamin E is also called tocopherol. Vitamin E has antioxidant properties. Alpha-tocopherol is the form of Vitamin E absorbed by

the human body. Vitamin E absorption depends on normal fat absorption. Once absorbed, Vitamin E is incorporated into

chylomicrons. Vitamin E deficiency in newborns might result in

hemolytic anemia.


Vitamin E as an Antioxidant


Vitamin E on the Menu


Vitamin K

Vitamin K was named for “koagulation,” the Danish word for coagulation.

Vitamin K is found in several forms, including phylloquinone and menaquinone.

Abnormal blood coagulation is the major symptom of vitamin K deficiency.

Vitamin K deficiency is very rare in the US.


Vitamin K on the Menu


Summary of Fat-Soluble Vitamins


Dietary Supplements Dietary supplements can be another source of vitamins

in the modern diet. Dietary supplements can 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.

Dietary supplements may be beneficial, with a physician’s guidance, for some older adults, people with restricted diets, people taking some medications, cigarette and alcohol users, some infants and children and people following a vegan diet.


Ingredients in Herbal Supplements


Ingredients in Herbal Supplements


What Should I Eat? VitaminsFocus on foliage for folate, vitamin A, and vitamin K Have a heaping helping of leafy greens. Snack on an orange—you’ll get your folate. Eat beans—such as lentils and kidneys—in soups and stews. Utilize a hidden source of beta-carotene by eating something dark green and leafy.

B (vitamin) sure Don’t forget the whole grains to get vitamin B6. Enrich your diet with some enriched grains. Have a bowl of fortified breakfast cereal for B12 insurance.

Get your antioxidants Go with nuts and seeds to increase your vitamin E. Think color when choosing your five fruits and veggies each day. Add carrot sticks to your lunch or snack to increase your vitamin A intake. Savor some strawberries and kiwis for dessert—they are loaded with vitamin C.

Soak up some D Get outside to stay fit and make some vitamin D. Have three servings of dairy per day to ensure that you get enough vitamin D.


End of Chapter 7

Copyright 2010 John Wiley & Sons, Inc.

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Chapter 7 Vitamins. Copyright 2010, John Wiley & Sons, Inc. Water-Soluble and Fat-Soluble Vitamins.

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