Chapter Review

BRING IT HOME

CHAPTER 11 BRING IT HOME

Evaluating vitamin B and vitamin C dietary supplements

You may have considered purchasing and taking a dietary supplement after hearing or reading about its potential benefits to your health, physical performance, energy level, or appearance. Follow the steps below to explore some resources that can help you learn more about one of the B vitamins or vitamin C as a dietary supplement. This isn’t a comprehensive or conclusive review; no definite conclusion can be made from looking at a few studies, but you will learn what questions to consider when evaluating dietary supplements and which online resources have more extensive information to guide you.

Choose one of the B vitamins (thiamin, riboflavin, niacin, pantothenic acid, biotin, folic acid, vitamin B6, or vitamin B12) or choline or vitamin C to investigate. Ideally, you will have access to the vitamin supplement’s bottle or package. If you don’t have a supplement bottle, you can also find specific product information and label information by visiting supplement manufacturer websites.

Question 11.5

1. Which vitamin supplement did you chose to evaluate?

Question 11.6

2. Are there any warnings or precautions for use of this product listed on the bottle or package?

Question 11.7

3. Does the label include any health-related claims? Are these FDA-approved health claims or structure/function claims? Do you trust the claims? Why or why not?

Question 11.8

4. Does the label of your supplement include any designations or claims regarding its purity, safety, quality, or effectiveness? Does the label have a symbol that the product has been evaluated for quality assurance from an independent laboratory?

Question 11.9

5. Why do you think someone might choose to take this supplement or product? What benefit do you think people expect when they purchase and use this supplement?

Question 11.10

6. Visit www.pubmed.gov (U.S. National Library of Medicine, National Institutes of Health) for access to thousands of abstracts from peer-reviewed medical and scientific journals. Type your vitamin’s name in the search box. If you are looking for information on a specific claim, you might search the vitamin and the condition—for example “folate AND birth defects.” Read at least two medical abstracts regarding the vitamin you’ve chosen, taking special note of the “Results” and “Conclusions” sections in the abstract, if they exist. From your brief review, in your opinion, is there sufficient medical evidence to justify the supplement’s claims?

Question 11.11

7. Explore at least two of the websites listed below for additional information on your dietary supplement. List three things you learned about the vitamin supplement.

National Institutes of Health dietary-supplements.info.nih.gov

U.S. Office of Dietary Supplements ods.od.nih.gov/index.aspx

National Center for Complementary and Alternative Medicine www.nccam.nih.gov

Medline Plus www.nlm.nih.gov/medlineplus/druginformation.html

Dietary Supplement Information Bureau www.supplementinfo.org

Natural Medicines Comprehensive Database www.naturaldatabase.com

Question 11.12

Based on your review of the vitamin supplement label and readings/research above, what recommendations and/or reservations do you have regarding the use of this vitamin as a dietary supplement?

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KEY IDEAS

KEY IDEAS

  • The essential water-soluble vitamins disperse easily in water-based solutions and include the B vitamins, vitamin C, and the vitamin-like nutrient, choline.

  • Water-soluble vitamins are not stored in large quantities in the body and must be consistently consumed in adequate amounts to meet the body’s needs and prevent deficiencies.

  • Dietary deficiency diseases of the water-soluble vitamins result from inadequate intake or conditions that decrease absorption with subsequent low blood levels. Although deficiencies of many of the B vitamins may have similar signs and symptoms and often occur simultaneously, unique deficiency diseases have been identified for many of the B vitamins and vitamin C.

  • Although water-soluble vitamins rarely reach toxicity levels from food alone, excess intake through dietary supplements and/or fortified foods may exceed the established Tolerable Upper Intake Level (UL) for some vitamins.

  • The B vitamins include thiamin (B1), riboflavin (B2), niacin (B3), pantothenic acid (B5), pyridoxine (B6), biotin (B7), cobalamin (B12), and folate (B9).

  • The B vitamins function primarily as coenzymes, chemical compounds that bind enzymes and are required for their function or activity. As coenzymes, they participate in energy metabolism—transforming carbohydrate, protein, and fat into energy—as well as a myriad of other types of reactions.

  • Megaloblastic anemia—characterized by large, immature, and sometimes irregularly shaped red blood cells—results from folate deficiency, but is also seen with vitamin B12 deficiency.

  • Choline, the most recently identified essential nutrient, is a water-soluble compound frequently grouped with the B vitamins because of its intertwined role with folate and vitamin B12.

  • Vitamin C is a water-soluble vitamin that functions as a coenzyme in biological reactions, aids in hormone production, serves as an antioxidant, and is involved in the synthesis of collagen.

256

NEED TO KNOW

NEED TO KNOW

Review Questions

Question 11.13

1. Characteristics of water-soluble vitamins include all of the following, EXCEPT:

  1. they all function as coenzymes.

  2. they are stored in muscle and liver.

  3. most circulate freely in the blood.

  4. they dissolve or disperse in water.

  5. they are easily destroyed or removed during food preparation.

1. b

Question 11.14

2. The B vitamins include all of the following, EXCEPT:

  1. biotin.

  2. folate.

  3. niacin.

  4. pantothenic acid.

  5. tocopherol.

2. e

Question 11.15

3. Chemical compounds that bind enzymes and are required for their function are termed:

  1. catalysts.

  2. coenzymes.

  3. hormones.

  4. lipoproteins.

  5. precursors.

3. b

Question 11.16

4. The deficiency disease associated with the B vitamin thiamin is:

  1. beriberi.

  2. pernicious anemia.

  3. megaloblastic anemia.

  4. pellagra.

  5. rickets.

4. a

Question 11.17

5. The vitamin that is sometimes given as a prescription to help lower LDL cholesterol and raise HDL cholesterol is:

  1. riboflavin.

  2. niacin.

  3. pyridoxine.

  4. thiamin.

  5. vitamin E.

5. b

Question 11.18

6. The primary source of riboflavin in the U.S. diet is:

  1. citrus fruits.

  2. grains.

  3. milk.

  4. nuts.

  5. shellfish.

6. c

Question 11.19

7. A chemical name for vitamin B6 is:

  1. cobalamin.

  2. linolenic acid.

  3. pantothenic acid.

  4. pyridoxine.

  5. tocopherol.

7. d

Question 11.20

8. Absorption of vitamin B12 requires:

  1. the presence of vitamin C in the same meal.

  2. the presence of bile in the small intestine.

  3. binding to a protein in the stomach called intrinsic factor.

  4. incorporation into chylomicrons in the blood.

8. c

Question 11.21

9. When consumed in adequate amounts before conception and early in pregnancy, ________ has been shown to prevent as many as two-thirds of all cases of ____.

  1. vitamin A; immune-related disorders

  2. folate; neural tube defects in newborns

  3. vitamin D; premature bone loss

  4. vitamin B6; morning sickness in women

9. b

Question 11.22

10. Functions of vitamin C include all of the following, EXCEPT:

  1. it acts as a coenzyme.

  2. it aids in hormone production.

  3. it serves as an antioxidant.

  4. it is a structural component of cell membranes.

  5. it synthesizes collagen.

10. d

Question 11.23

11. The absorption of dietary iron is enhanced by the presence of:

  1. choline.

  2. fiber.

  3. pyridoxine.

  4. vitamin C.

  5. water.

11. d

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Dietary Analysis Using SuperTracker

Dietary Analysis Using SuperTracker

Analyzing intake of water-soluble vitamins

The water-soluble vitamins include the B vitamins and vitamin C (and the nutrient choline). Because these vitamins are generally not stored in the body, deficiency conditions of the water-soluble vitamins develop more quickly than for the fat-soluble vitamins. Using SuperTracker, identify the sources of water-soluble vitamins in your diet and compare the amount you get with the current dietary recommendations.

Question 11.24

1. Log on to the United States Department of Agriculture (USDA) website at www.supertracker.usda.gov. If you have not done so already, you will need to create a profile to get a personalized diet plan. This profile will allow you to save your information and diet intake for future reference. Do not use the general plan.

Question 11.25

2. Click the Track Food and Activity option.

Question 11.26

3. Record your food and beverage intake for one day that most reflects your typical eating patterns. Enter each food and beverage you consumed into the food tracker. Note that there may not always be an exact match to the food or beverage that you consumed, so select the best match available.

Question 11.27

4. Once you have entered all of your food and beverage choices into the food tracker, on the right side of the page under the bar graph, you will see Related Links: View by Meal and Nutrient Intake Report. Print these reports and use them to answer the following questions:

  1. Did you meet the targets for the water-soluble vitamins on the day you selected? If not, which vitamin intakes are below the target numbers?

  2. For each vitamin target that you missed, list two specific foods you could consume to increase your intake of that vitamin.

  3. Was your intake above the targets for any of the water-soluble vitamins? If so, which ones? Are there any issues with toxicity that are associated with those vitamins?

  4. Discuss how the enrichment of grains in the United States has helped eradicate certain water-soluble vitamin deficiencies. What deficiencies are rarely seen in the United States as a result of this policy?

  5. Many foods and beverages are fortified with water-soluble vitamins. Discuss the pros and cons of this practice.