Serving Sizes and Other Food Label Secrets

Two months ago, I ran out of magnesium tablets, which keep my legs from jumping at night. I bought more, but my legs continued to jump. Why?

I had been taking 500 milligrams (mg), and the new brand said 400 mg, but they were more expensive, and I figured higher quality. I thought 400 mg would be OK.


What I didn’t notice was the nutrition label: “Serving size: 3 tablets.” Taking my usual 1 tablet a day, I was getting only about 133 mg. No wonder my legs didn’t respond!

Food labels have lots of good information, but you need to know how to read them, a skill I obviously had forgotten. I took a refresher course.

Reading food labels

An article by diabetes educators Laura Hieronymus and Belinda Carlisle explains that food labels put important information in different places. The Nutrition Facts panel should list the amounts of nutrients in the food or supplement. The serving size is usually the first thing listed. It should tell you two things: what the size is of one serving, and how many servings are in the container. This is really useful when it comes to figuring out how much to eat.

Hieronymus and Carlisle give these sample food labels for packaged pizzas. They both have about the same amount of carbohydrate per serving, but one package has one serving per container, while the other expects you to get four servings out of it. If you ate the whole pizza in the second case, like you did in the first, you would get four times more carbohydrates than you might have expected based on the number of carbohydrate grams listed on the label. Your blood sugar would probably spike for many hours, and possibly even days.

You might want to consider the “servings per container” as advice on how much to eat. If the label says six servings to a container, you might not want to eat the whole thing at once.

You might want also want to know other information about the food in question. The Nutrition Facts panel should tell you how many calories; grams of carbohydrate, protein, and fat; and what amounts of major vitamins or minerals are in the product. For each nutrient listed, it should also list what percentage of the amount you need each day you will get from one serving. This is called Percent Daily Value and is usually listed in a column headed %DV. Labels may or may not give amounts of other nutrients such as soluble and insoluble fiber and saturated and unsaturated fat.

Also useful is the ingredients list. Ingredients are listed in order — that is to say, the ingredient that makes up the greatest proportion of the food is listed first, and other ingredients are listed in descending order by amount. This list can tell you useful things, such as what chemicals have been added to the item.

The ingredients list can also deceive you. For instance, maybe you wouldn’t buy something that listed “sugar” as the first ingredient, but manufacturers may divide “sugar” up into terms like sucrose, fructose, beet sugar, high-fructose corn syrup, and others, so that each one ranks lower on the ingredient list. Healthier-sounding terms might rank higher, but the total amount of sugar is still the same.

Understanding label terms

Many terms you’ll see on other parts of the food label are less helpful. They’re marketing terms. In this article, “11 Tips for Food Shopping With Diabetes,” dietitian Regina Shirley gave the American Academy of Nutrition and Dietetics’ definitions for various terms (such as “low-fat” or “calorie free”) that you may see on labels or in advertising. They can be confusing.

Other terms, such as “healthy,” “natural,” diabetes-friendly” and many others provide little information. These do not have a standard definition from the U.S. Food and Drug Association (FDA) and are just used to get your attention.

There is so much more to know about food labels. Activists fought for these labels for decades to help us choose healthy food. Learn how to use them well by reading the articles referenced throughout this article, or others like this one from the FDA, the organization that designs food labels.

Want to learn more about understanding food labels? Read “Are You Label-Able?” and “Looking Beyond ‘Low-Carb’ Labels.”