Week 11

Chapter 12 The Fat-Soluble Vitamins
(On the syllabus this is listed for Wk 12)

In A Nutshell:

	Vitamin A is needed for vision and for the growth and differentiation of cells. It affects epithelial tissue, reproduction, and immune function. It is found in the diet both preformed as retinoids and in precursor forms called carotenoids. Preformed vitamin A can be toxic and can increase the risk of birth defects. The major food sources of preformed vitamin A include liver, eggs, fish, and fortified dairy products. Carotenoids are found in fruits and vegetables such as mangoes and carrots. Beta-carotene is the most potent precursor. Vitamin A deficiency is a world health problem that causes blindness and death.
	Vitamin D is essential for maintaining proper levels of calcium and phosphorus in the body. It functions by promoting calcium and phosphorus absorption from the intestines and release from bone. Vitamin D can be made in the skin by exposure to sunlight, so dietary needs vary depending on the amount synthesized. In the diet, it is found in fish oils, and fortified milk. A deficiency in children results in a condition called rickets; in adults, vitamin D deficiency causes osteomalacia.
	Vitamin K is essential for blood clotting. Since vitamin K deficiency is a problem in newborns, they are routinely given vitamin K injections at birth. Dicumarol, a substance that inhibits vitamin K activity, is used medically as an anticoagulant. Vitamin K is found in plants and is synthesized by bacteria in the GI tract.
	Antioxidants are substances that help neutralize highly reactive forms of oxygen and nitrogen such as free radicals before they can do damage. Free radicals and other reactive molecules are generated inside the body from normal metabolic reactions and my also come from the environment. They cause oxidative damage by stealing electrons from DNA, proteins, CHOs, and unsaturated fatty acids. The body is equipped with a variety of antioxidant defenses, including vitamins and phytochemicals consumed in the diet and enzymes synthesized in the body, many of which rely on minerals for activity.
	Vitamin E functions primarily as a fat-soluble antioxidant. It is necessary for reproduction and protects cell membranes from oxidative damage. Good dietary sources include nuts, plant oils, green vegetables, and fortified cereals.
	Vitamin needs can be met by a carefully selected diet that follows the recommendations of the MyPyramid food guidance system. The diet can be balanced by choosing foods from all groups. From within each group a variety of nutrient dense foods should be selected. Food processing, storage, and preparation can cause vitamin losses. Food labels can be used to select packaged foods that are good sources of vitamins A and C, and others when voluntarily included on the label.
	Functional foods are foods that provide physiological benefits beyond that of simply meeting nutrient needs. Some foods are considered functional because they are good sources of phytochemicals. "Phytochemicals" is a term used to refer to the chemicals found in plants. Many of these have health-promoting properties and are associated with reductions in the risk of cancer and other degenerative, chronic diseases. Some act as antioxidants, some affect the activity of enzymes or hormones, and others work by other mechanisms. Dietary recommendations advise Americans to increase their consumption of fruits and vegetables because these foods are sources of phytochemicals.
	Over half the adult population in the USA takes some type of dietary supplement. Dietary supplements may contain vitamins; minerals; herbs, botanicals, or other plant-derived substances; amino acids; enzymes; concentrates or extracts.
	Vitamin supplements are recommended for some groups of individuals such as dieters, vegetarians, and nutritionally vulnerable groups.
	Many substances that are not nutrients are available as supplements. Some dietary supplements contain compounds that are already present in the body but are not essential in the diet. Others contain plant extracts and herbs. These products may have beneficial physiological actions, but they can also have dangerous side effects.

Vitamins are essential organic nutrients that are needed in small amounts in the diet to promote and regulate body processes needed for growth, reproduction, and tissue maintenance. Vitamins do not provide energy.

Vitamins are naturally present in foods, added to foods by fortification and enrichment, and contained in supplements. The amount of a vitamin that is available to the body is regulated by vitamin absorption, transport, activation, storage, and excretion.

Vitamin deficiencies remain a major health problem worldwide. In industrialized countries, marginal dietary deficiencies and toxicities from supplements are a growing concern.

Recommended intakes for vitamins are established by evaluating the results from many different kinds of research. The DRIs express recommended intakes as RDAs or AIs. See the back inside cover of your textbook.

FYI
In the United States, herbal and other dietary supplements are regulated by the U.S. Food and Drug Administration (FDA) as foods. This means that they do not have to meet the same standards as drugs and over-the-counter medications for proof of safety, effectiveness, and what the FDA calls Good Manufacturing Practices.

Study Guide

1. Define the term 'vitamin' and list 3 characteristics of vitamins as a group.
     Which vitamins are classified as water-soluble? Which are fat-soluble?

2. Classify the vitamins according to whether they are fat soluble or water soluble.
    How does the absorption of fat-soluble vitamins differ from that of water-soluble
    vitamins? Why are large doses of certain fat-soluble vitamins more likely to cause
    toxic effects than large intakes of water-soluble vitamins?

3. List 3 important food sources for each fat-soluble vitamin.
    What are 3 sources of provitamin A and 3 sources of preformed vitamin A?

4. Why is the carotenoid beta-carotene classified as a provitamin?

5. How does vitamin A affect vision?

6. What population groups are at highest risk of vitamin A deficiency?

7. What are the signs and symptoms of vitamin A toxicity?

8. Why is vitamin D often classified as a conditional vitamin, or pro-hormone?

9. What are the rich dietary sources of vitamin D?

10. What are 3 functions of vitamin D?

11. What are the consequences of vitamin D deficiency?

12. Why are those who live in northern latitudes at risk of vitamin D deficiency?

13. Why was an Upper Level of intake established for vitamin D?

14. How does vitamin E function as an antioxidant in the body?

15. What are 3 foods rich in vitamin E?

16. Why is excess supplementation of vitamin E of concern in individuals taking daily
      aspirin or anticoagulation medications?

17. What are 3 foods that are rich sources of vitamin K?

18. How does vitamin K help in the formation of blood clots?

19. Why should people on the drug Coumadin avoid taking vitamin K suplements?

20. What population groups are at increased risk of a vitamin K deficiency?

21.   Evaluate the use of vitamin and mineral supplements with respect to their potential
      benefits and risks to health.

Becky Alejandre, Professor - Nutrition	Instructor's contact information Email: alejanb@arc.losrios.edu Phone: (916) 484-8145 FAX: (916) 484-8030	ARC Homepage	ARC Library
Office Location: Room #762 Health & Education Division (located between the tennis courts and the gym)		Office Hours: Mon. 8:00-10:00 a.m. Tues. 10:30-11:30 a.m. Wed. 10:30-11:30 a.m. (online) Thurs.10:30-11:30 a.m. Fri. 7:00-8:00 a.m. (online)

Becky Alejandre, Professor - Nutrition

Becky Alejandre,
Professor - Nutrition