© 2007 Thomson - Wadsworth Chapter 6 The Vitamins

© 2007 Thomson - Wadsworth

Chapter 6

The Vitamins


Ask Yourself1. The most important role that vitamins play is

providing energy.2. You can’t overdose on vitamins, because the

body excretes them in the urine.3. Several major public health associations

recommendthat all adults take antioxidant supplements.

4. Serving for serving, fruits and vegetables tend to be the richest sources of vitamins.

5. In general, nutrients are absorbed equally well from foods as from supplements.


Ask Yourself

6. Vitamin C supplements prevent colds.7. Oatmeal is an example of a functional

food.8. Fresh vegetables contain more

vitamins than frozen vegetables.9. Phytochemicals are beneficial

nonnutrient substances found in fruits, vegetables, and whole grains.

10. Large doses of niacin can cause flushing, rash, and fatigue.


Turning Back the Clock

• Scurvy: the vitamin C deficiency disease characterized by bleeding gums, tooth loss, and even death in severe cases.

• Rickets: a disease that occurs in children as a result of vitamin D deficiency and that is characterized by abnormal growth of bone, which in turn leads to bowed legs and an outward-bowed chest.

• Pellagra (pell-AY-gra): niacin deficiency characterized by diarrhea, inflammation of the skin, and, in severe cases, mental disorders and death.

Many vitamin deficiency diseases have been eliminated today with the discovery ofvitamins.


The Vitamins

• Vitamin: a potent, indispensable compound that performs various bodily functions that promote growth and reproduction and maintain health. Vitamins are organic, meaning that they contain or

are related to carbon compounds. Contrary to popular belief, vitamins do not supply

calories. They are essential to helping the body make use of

the calories consumed via foods.

• Organic: of, related to, or containing carbon compounds.


The Vitamins

• Recommended intakes and tolerable upper intake levels for vitamins can be found in the Dietary Reference Intakes (DRI) tables (see table inside front cover).

• Megadose a dose of ten or more times the amount normally recommended. An overdose is an amount high enough to

cause toxicity symptoms. Megadoses taken over a long period often

result in an overdose.


Two Classifications of Vitamins








Good Sources of Vitamins in the USDA MyPyramid


The Two Classifications of Vitamins

Coenzymes: enzyme helpers; small molecules thatinteract with enzymes and enable them to do their work. Many coenzymes are made from water-soluble vitamins.


Water-Soluble VitaminsThiamin• One of the B vitamins.• Acts primarily as a coenzyme in

reactions that release energy from carbohydrate.

• It also plays a crucial role in processes involving the nerves.

• Beriberi: the thiamin deficiency disease, characterized by irregular heartbeat, paralysis, and extreme wasting of muscle tissue.


Water-Soluble Vitamins


Water-Soluble VitaminsRiboflavin• Also one of the B vitamins.• Acts as a coenzyme in energy-

releasing reactions in the body. • Helps to prepare fatty acids

and amino acids for breakdown.

• Deficiencies of the vitamin, (rare) are characterized by severe skin problems, including painful cracks at the corners of the mouth; a red, swollen tongue; and teary or bloodshot eyes.




Water-Soluble VitaminsNiacin• Also one of the B vitamins.• Also part of a coenzyme vital

to obtaining energy. • Recall that pellagra is the

deficiency disease.• Can be made from the amino

acid tryptophan in the body. 60 milligrams of tryptophan yield

1 milligram of niacin. Thus, the DRI for niacin is

expressed in niacin equivalents (NE).




Water-Soluble VitaminsVitamin B6

• Functions as a coenzyme• Indispensable cog in the

body’s machinery• It is proportional to

protein intakes• Deficiency causes a

multitude of symptoms: weakness irritability insomnia




Water-Soluble VitaminsFolate (also called folic acid

or folacin)• Coenzyme with many functions

in the body.• Important in the synthesis of

DNA and the formation of red blood cells.

• A deficiency makes the red blood cells misshapen and unable to carry sufficient oxygen. Causing a certain kind of anemia.Anemia: any condition in which

the blood is unable to deliver oxygen to the cells of the body.



Folate• It plays a crucial role in a healthy

pregnancy.It reduces the risk of bearing a

baby with a type of birth defect called a neural tube defect.•Like spina bifida



The Food and Drug Administration has mandated that all enriched grain products be fortified with folic acid toimprove intakes in the United States population.



Water-Soluble VitaminsVitamin B12• Maintains the sheaths that

surround and protect nerve fibers.• Works closely with folate,

enabling it to manufacture red blood cells.

• Deficiencies are not likely to occur. Some groups are at risk: Strict vegetarians Those with a genetic defect

that leaves the body unable to make a compound known as intrinsic factor

And those elderly who may develop atrophic gastritis





Pantothenic acid and biotin

• Biotin is also required for cell growth, synthesis of DNA and maintenance of blood glucose levels.

• Both are needed for the synthesis of coenzymes that are active in a multitude of body systems.

• Both are widespread in foods, so people who eat a varied diet are not at risk for deficiencies.




Water-Soluble VitaminsVitamin C• Required for the production

and maintenance of collagen.• Boosts the body’s ability to

fight infections.• Potential role as a chronic-

disease fighter stems from its workings as an antioxidant.Antioxidant: a substance, such as a

vitamin, that is “anti-oxygen” – that is, it helps to prevent damage done to the body as a result of chemical reactions that involve the use of oxygen.



Vitamin C is widespread in the food supply. Deficiencies arise both in infants not given a source of vitamin C and in children and the elderly.


Fat-Soluble VitaminsVitamin A• One of the most versatile

vitamins; plays roles in several important body processes.

• Best known function is in vision.• Helps to maintain healthy

epithelial tissue.• Up to a year’s supply can be

stored in the body, 90% of it in the liver.

• Deficiency symptoms will not begin to appear until after your stores are depleted. Consequences include blindness and

reduced resistance to infection.


Fat-Soluble VitaminsVitamin A• The body uses both the preformed vitamin A

and the beta-carotene in foods to make retinol.Preformed vitamin A: active form of vitamin A.Beta-carotene: an orange pigment found in

plants that is converted into vitamin A inside the body. Beta-carotene is also an antioxidant.

Precursor: a compound that can be converted into another compound. For example, beta-carotene is a precursor of vitamin A.

• Pre = before• Cursor = runner, forerunner


Fat-Soluble Vitamins

Because the body uses both the preformed vitamin A andthe beta-carotene in foods to make retinol, the amount of vitamin A in foods is expressed in retinol activity equivalents(RAE)—a measure of the amount of retinol the body willderive from the food.


Figure 6-4 A The Antioxidants Versus Free RadicalsIn The Body- Free Radicals – unstable oxygen molecules

can be formed from sunlight, smoking, and pollution.


Figure 6-4 B (cont.) The Antioxidants Versus Free RadicalsIn The Body – Antioxidants prevent free-radicals from attackingcells and causing damage by neutralizing free radicals and converting them back into stable oxygen molecules.


Fat-Soluble VitaminsVitamin D• Is a member of a large bone-

making and maintenance team.• Assists in the absorption of

dietary calcium. • Helps to make calcium and

phosphorus available in the blood.

• The body can synthesize it with the help of sunlight.

• Deficiency diseases In children, rickets In adults, osteomalacia


This child has the bowed legs characteristic of rickets

The sunshine vitamin





Vitamin E• Known as a vitamin in search of

a disease.• Performs a key role as an

antioxidant in the body.• Widespread in the food supply,

and deficiencies of the nutrient are rare. People who run the risk of

deficiency:• Premature infants who are born

before vitamin E is transferred to them from their mothers.

• Those who cannot absorb fats as a result of diseases.

• Those with certain blood disorders.




Fat-Soluble VitaminsVitamin K• Key function: its role in the

blood-clotting system of the body.

• Works with vitamin D to help regulate the calcium levels in the blood.

• Is obtained both in the diet and via the intestinal bacteria, making deficiencies rare. Newborn babies are the one group

that is commonly susceptible to a vitamin K deficiency.

• A baby’s digestive tract is free of bacteria until birth.




Nonvitamins

• Choline A nonessential nutrient used by the body to

synthesize various compounds including: • the phospholipid lecithin

The body can make it from the amino acid methionine.

It can be found in milk, eggs, peanuts, and many other foods.

Deficiencies are rare.


Nonvitamins

• Other nonessential nutrients that may be added to dietary supplements:PABA or para-aminobenzoic acidBioflavenoids or “vitamin P” or hesperidinCoenzyme Q or ubiquinoneVitamin B15

Vitamin B17 or laetrile, a falsely touted cancer “cure”


• Plan• Shop• Store• Cook• Eat


Phytonutrients in Foods

• Phytochemicals (FIGH-toe-CHEM-icals): physiologically active compounds found in plants that are not essential nutrients but that appear to help promote health and reduce risk for cancer, heart disease, and other conditions.

• Also called phytonutrients. phyto = plant


Mechanisms of Actions of Phytochemicals

• Many foods contain numerous phytochemicals, each one acting on one or several mechanisms.Antioxidant properties - protect

against harmful cell damage.Anticancer properties - preventing

initiation and promotion of cancer.Antiestrogen properties - blocking

action of estrogen and lowering risk of some cancers.




A Daily Eating Plan for Phytochemicals

• Research indicates that whole foods containing phytochemicals are more effective than extracts of phytochemicals in supplements.

• Until more is known, it is best to follow the recommendations of the MyPyramid food guide and consume recommended amounts of fruits and vegetables each day along with a variety of whole grains, soyfoods, other legumes, nuts, and seeds.


• Functional food: a general term for foods that provide an additional physiological or psychological benefit beyond that of meeting basic nutritional needs. Also called medical foods.

• Designer foods: foods “fortified” with phytochemicals or plants bred to contain high levels of phytochemicals; also known as “future foods.” Genetic engineering of foods—also called

biotechnology—is discussed in your text, Chapter 12.



Functional Food Pyramid




Research is currently under way in the U.S. to test the safety and efficacy of a few of the most popular herbs on the market today.



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Laws & Dietary Supplements

• In 1994, Congress passed the Dietary Supplement Health Education Act (DSHEA), which severely restricted the FDA’s authority over dietary supplements so long as the product makes no claim to affect a disease.

• Supplements are presumed safe until the FDA receives well-documented reports of adverse reactions.

• Supplements are not obliged to meet any standards of effectiveness or safety.


Laws & Dietary Supplements

• Products cannot state on the label that they will “prevent,” “treat,” “diagnose,” ”mitigate,” or “cure” disease.

• Product must carry a disclaimer on the label - “This product has not been evaluated by the Food and Drug Administration.”

• FDA can require that supplements follow “good manufacturing practices.” This specifies sanitation standards, not efficacy or purity.


Consumers and Dietary Supplements

• Be informed:Seek unbiased, scientific sources (see

reference list in chapter 6).Inform your physician, especially if

taking prescribed medications.

• Do not exceed recommended doses, or use for prolonged periods.



Cancer initiation: Carcinogens cause cancerous alterationin previously healthy body cells.


Cancer Promotion: Cancer promoters enhance the growthOf abnormal cancerous cells.


Cellular Repair: Cancer antipromoters squelch free radicalDamage and enhance the body’s ability to repair damagedDNA strands.


Impact of Risk Factors on Cancer




Nutrition and Cancer Prevention

Cruciferous vegetables protect against cancer

The 5 a Day for Better Health program recommends 5 or more fruit & vegetable servings per day


Nutrition and Cancer Prevention

American Institute for Cancer Research released recommendations for cancer prevention:

1. Eat a variety of healthful foods, with an emphasis on plant sources.

2. Adopt a physically active lifestyle.3. Maintain a healthful weight throughout life.4. If you drink alcoholic beverages, limit

consumption.5. Prepare and store food safely.6. Do not use tobacco in any form.

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© 2007 Thomson - Wadsworth Chapter 6 The Vitamins