Symposium on Critical Thinking and Consumer Chemistry -
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Using Chemical Principles To Encourage Critical Thinking in Consumer Chemistry John W. Hill University of Wisconsin-River Falls, River Falls, WI 54022 We are constantly bombarded with advertisements urging us to buy a product or service. Students in consumer chemistry courses can be encouraged to use chemical principles to evaluate claims made in those advertisements. Weight-LOSSDiets At least one person in over half the households in the United States is on some kind of weight-loss diet. Hundreds of books, diet plans, and exercise programs are directed a t dieters. Most offer quick, painless remedies for removal of excess weight. ~ p p l i i a t i o nof the law of conservation of energy (I) and some simple calculations can aid in a critical evaluation of claims made by the proponents of the various plans. If we take in more food enerev than we use. the excess is stored. We can store about 2000kcal of energyin the form of the carbohvdrate elvcoaen. . - That amounts to about 500 g (or about 1 id) of glycogen. Our ability to store fat is n i t so limited. One pound of adipose tissue represents 3500 kcal of stored energy. In an advertisement, a man claims to have lost 87 lh in 90 days (without going hungry!). Is such a claim reasonable? Let us assume that he needs 2500 kcal to maintain his present weight. If he ate nothing(!), he would burn off 0.71 lblday (250013500) of adipose tissue. In 90 days of total fastine. he would eet rid of 64 lb of "fat". When vou recall that gsupposedl;did not even go hungry, you can see that his claim of a 87-lb loss is a bit far fetched. Most quick-weight-loss diets depend on glycogen depletion and dehvdration. Glvcoaen is depleted by fasting, a low carbohydrate diet, or exercise. ~ l y c o g e nis starch; i c many hydroxyl groups hydrogen bond to water. Associated with each pound of glycogen is about 3 1b of water. Glycogen is depleted in a day, giving a quick loss of about 41b (water plus glycogen). Many of these diet regimens also include a diuretic, such as caffeine, to increase the excretion of water in urine. Such losses are of no benefit: the weiebt is reeained as soon as carbohydrates are returned to the &et a n i t h e person reolaces the lost water. As far as weight loss isconcerned. quick = quack. Structure and Properties Another principle that can be used to evaluate advertising claims is the structure-property relationship of organii chemistry. Structural formulas are deduced from chemical data. Those structures are then used to repreand sent the chemical compounds and their properties. With practice, we can deduce properties from structures. Those properties are invariant; they do not depend on advertising claims or our wishes. Let us examine some advertising claims for over-thecounter drugs. Bayer aspirin is a best-selling product. Advertisements claim (or a t least imply) that Bayer is better than other brands of aspirin. Is Bayer better? Aspirin is acetylsalicylic acid. I t has a nice set of desirable properties; it is an antipyretic, analgesic, anti-inflammatory agent, and anticoagulant. Some of the properties may he undesirable.
Aspirin may cure your headache, but it also promotes bleeding and causes allergic reactions in some people. The desirable and undesirable properties are inseparable. Indeed, the anticoagulant action may be desirable-it may decrease the chance of a second stroke or heart attack. Or that property may be undesirable-promoting bleeding from a wound or aeeravatine " an ulcer. In more basic terms knowine that asoirin is aspirin can save the consumer a lot of money. It is not possible tbat the properties of acetylsalicylic acid vary with brand name. It is possible that one aspirin tablet can be different from another. For example, tahlets with different hinders (inert ingredients that hold the tahlets together) could dissolve at different rates. Clinical studies show little if any evidence of significant differences in brands (2). Many brands of aspirin and of combination drugs make the claim that their product contains the drug that "doctors recommend most". That claim simply reflects the fact that acetylsalicylic acid is the cheapest nonprescription analgesic and is as effective as any other. Tylenol is the best-selling of all nonprescription drugs. The advertisements say that Tylenol is the pain reliever hospitals use most. The only active ingredient in Tylenol is acetaminophen. Acetaminophen has a set of properties; for example. it is an analeesic and antiovretic. ." Its use in hosoitals is based on a property that it does not have. ~ s ~ i ; i n promotes bleeding; acetaminophen does not. Many patients in hospitals are there for treatment of wounds or for surgery, both of which make use of aspirin undesirable. Use of acetaminophen in hospitals is irrelevant except for consumers who want to avoid the anticoagulant properites of aspirin. Even then the consumer can choose another brand or a generic variety. Can generic acetaminophen have different properties from that in Tylenol? Most "nonaspirin pain relievers" contain acetaminophen. Reading the label often can save the consumer a lot of monev. Some products claim to he "extra strength" or "maximum strength". These products are simolv lareer dosaees of the sameactive ingredient, usually at much higher price. Extra-Strength Tylenol has 500 mg of acetaminophen per tahlet compared to 325 mg in regular Tylenol. Similarly, Maximum-Strength Bayer has 500 mg of acetylsalicylic acid per tablet compared to 325 mg in regular Bayer aspirin. Three regular tablets of either Bayer or Tylenol would provide 975 me of nain reliever. a dosaee not sienificantlv different from th; 1600mg provided b i t w o extra-strength tablets. The effective dose of either is about 500 mg (3).
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Reproducibility of Evldence Another important principle is that of the reproducibility of evidence, a cornerstone of experimental science. Anyone in the worldwide scientific communitv can demonstrate the properities of water or aspirin or vitamin C. What about Laetrile, the s u ~ u o s e danticancer drue? Ernst Krebs. Sr.. patented a substame with the molecula~formulac ~ ~ H ~ ; N o ; as Laetrile in 1958 (British patent no. 788,855). The claim was made tbat the substance selectively releases cyanide in Volume 65
Number 3
March 1988
209
cancer cells, killing the cancerous growth. Few, if any, of Krebs's claims are reproducible. No one has ever been able to make Laetrile by the method described in Krebs' patent. The stuff sold over the last several years has the molecular formula C20H27NOll and is properly called amygdalin. Further, it releases cyanide in the liver and not preferentially in cancer cells. Many cancer patients depending on Laetrile died who might have been saved by conventional treatment (4-6). Lack of reproducibility should serve as a warning signal of quackery to any chemist-even to an introductory chemistry student. Laetrile seems to be a dead issue today. Do we have to wait until many are dead before we denounce a quack as a quack? What is our responsibility as scientists
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Journal of Chemical Education
when quacks enrich themselves with "immune power diets", "cytotoxic" testing, and other irreproducihle claims? It is the duty of the chemist.. . to be diligent in exposing such errors and frauds as the chemist's special knowledge brings to light. -American Institute of Chemists, "Code of Ethics" Literature Hill,J, w.J, Chpm.Educ. 1981,58,896. 2. c ~ ~1982, ( ~~~ l ~ l .~3 ~ 7 - 3~~ ~ . ~ 3. Consumer Repons 1982, (Augustl, 395-389.
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4. Labisnce.D. A. J. Chem.Educ. 1919,56.788. ,,,iaon, B,H, L977,,Jul 21. 6. FDA Consumer December 1976dsnusry 1977.5.
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