Dear Dr. Blonz: Are arginine and L-arginine the same thing? What does the “L” stand for? I have also seen it on other amino acids, such as ornithine, but it is often missing in discussions. While I take natural vitamin E, I also noticed that synthetic vitamin E supplements also show “DL” together, but I am not sure what this means either, and I want an explanation. Thank you.

— V.E., Dover, Delaware

Dear V.E.: Arginine and L-Arginine probably refer to the same amino-acid substance. An upper or lowercase “L-” or “D-” before a chemical substance reveals something about the compound’s three-dimensional structure. The “L” and “D” forms have the same formula, but a subtle structural difference in their optical rotation can affect how the compound can be used in the body. “L” amino acids are more prevalent; our bodies’ proteins are made of them, and our diets rely on them. “D” amino acids cannot act as protein building blocks but may play other roles or be used for energy; they can be found in microbes and cultured foods, a product of the bacteria involved in fermentation.

As you indicate, the “L” might be left out in some writings. It is a bit less precise, but it saves the need for this complex explanation. On the “D” side of things, we have d-alpha tocopherol (vitamin E). In the case of this essential vitamin, the “D” is the active form. If both a “D” and an “L” are shown as the ingredient in a dietary supplement, as in “dl-alpha tocopherol,” this is a sign that this component was made synthetically. Nutrition Facts labels only show the amount of the active ingredient, so in that example, the amount of vitamin E would only be the amount of d-alpha tocopherol. The use of the “natural” description for vitamin E usually refers to the “D” form, but there is no FDA regulation requiring this, so it is always best to check the nutritional facts and ingredient lists when considering products.

Dear Dr. Blonz: I have a question about nuts in the bulk bins at the local produce store. Checking the nutrition facts labels on the bins shows that a serving of dry- and honey-roasted nuts are lower in calories and fat grams than the regular roasted or raw nuts. Please explain. Thank you.

— J.G., Sun City, Arizona

Dear J.G.: The roasting of peanuts, or any food for that matter, helps bring about flavor-enhancing chemical reactions. With nuts, this can be accomplished with or without oil. Dry roasting requires specially designed ovens and utilizes only hot air. If desired, the processor can then add salt, paprika or other flavorings. On average, half the weight of a raw nut and over 70% of its calories come from its fat. Dry-roasted nuts contain no added oils, but oil-roasted nuts will contain some residual oil from the roasting, which helps explain the additional calories per serving. You find fewer calories per serving with honey-roasted nuts as some weight is from the flavoring, which will have fewer calories per gram than roasting oil.

Kensington resident Ed Blonz has a PhD in nutrition from UC Davis. Email him at cctimes@blonz.com