Common Student Misconceptions
"Organic" foods are better than "processed foods. Chemical compounds have the same formula wherever they are produced. Oyster shell calcium carbonate is the same as calcium carbonate precipitated in the laboratory.
- Cereal and additives Check the labels for additions to your cereal. Check on the form of iron; "reduced iron" almost always means elemental iron; iron (III) salts precipitate in the intestine (pH = 10) as Fe(OH)3; iron (II) salts are stabilized as complexes (heme iron).
- Orange juice with calcium Check on the form of calcium added. The acid in orange juice could dissolve any calcium carbonate, releasing CO2, but other additives might not dissolve in the stomach acid. Is orange juice with added calcium a good buy? [No; very expensive.]
- New Horizons bread This bread is advertised as having fewer calories and more fiber. It contains cellulose, which is not metabolized and, therefore, provides fewer calories. Cellulose is also not useful as fiber in humans. Some "light" breadstuffs, such as frozen pancakes, also have a large amount of cellulose.
- Eggs and cholesterol Egg yolks, but not the whites, contain cholesterol. Egg substitutes are often made from the whites.
- Analysis of nutrition in hamburger and french fries Although there is still a debate over the disadvantages of saturated fats and their relationship to hardening of the arteries and cholesterol, students should be aware of these studies. Current research indicates that mono-unsaturated fats may be better than polyunsaturated or saturated fats. We know that cholesterol is carried in the body by high density lipoproteins to the liver to be excreted and by low densition lipoproteins through the blood stream. This knowledge has led to the erroneous nomenclature, "good" cholesterol (HDL) and "bad" cholesterol (LDL). Cholesterol has different chemical formula and is a different compound from lipoproteins and triglycerides.
R, R', R" are fatty acid residues
See Transparency of McDonald food components and ChemMatters article (see References, Baugh, 1989).
(Lipoproteins are conjugates of lipid and protein)