Nutrition Hotline

QUESTION: "I've been trying to save money by buying food at a store that sells products with expired 'sell by' dates. Is this safe?" N.E.C., MA

ANSWER: Interestingly, federal law does not require most food companies to include dates that indicate by when the food should be sold or eaten on the package. However, many companies do this so that the purchaser can be relatively certain that the food is fresh. Products that must display dates include some baby foods and infant formulas. These products should not be used after their expiration dates.

Some of the types of dates that may appear on foods include the following:

  • A 'best if used by' or 'use by' date. As you might guess, this means that the product should be fresh and will have the best flavor and texture if used by this date. Beyond this date, the product may begin to deteriorate, although it may still be edible. Perishable foods, like those in the refrigerated section, should not be purchased after the 'best if used by' or 'use by' date has passed. Foods that are unlikely to spoil (cereals, crackers, etc.) can usually be eaten after their 'best before' date, although they may have lost some of their flavor, freshness, and even nutritional value.
  • A 'sell by' date tells the store how long to display the product for sale. This is often used for refrigerated products. This date usually includes some leeway for home usage if the product is properly refrigerated. In other words, don't purchase products after the 'sell by' date, but if you notice something in your refrigerator that's a few days beyond the 'sell by' date, it's probably still good. Of course, if it looks or smells suspicious, discard it.
  • An 'expiration' date. If you haven't used the product by this date, toss it out.

Sometimes you'll come across a scratch-and-dent sale in a discount food store. Generally, canned products that have minor dents are safe to use. Major dents on cans or jars with rust, cracks, leaks, or bulges should be avoided, as should cans with dents at the seam or by the rim. Packages of food that have been torn or opened should not be purchased because the contents could be stale or have bugs.

QUESTION: "What is autolyzed yeast extract? Is it the same as MSG? Will it have the same effect as MSG?" M.E., via e-mail

ANSWER: Autolyzed yeast extract is added to foods as a flavor enhancer. It is produced by adding salt to live yeast. The salt makes the yeast cells undergo lysis, which means that the yeast cells disintegrate and are no longer able to function as yeast typically does. The result of this is autolyzed yeast, which is further processed to make autolyzed yeast extract. This product gives foods a savory flavor.

The savory flavor of autolyzed yeast extract is due to its glutamic acid content. Glutamic acid is an amino acid that produces a taste sensation called umami (ooh- MA-mee). Umami is commonly described as 'meaty.' The same taste sensation is produced by monosodium glutamate (MSG), a sodium salt of glutamic acid.

Glutamic acid is found in almost all foods, especially in foods that are high in protein.

Normally, glutamic acid is linked together with other amino acids to form proteins in foods. When it is connected to other amino acids, it is called bound glutamic acid, and it does not enhance flavor. When glutamic acid is separated from other amino acids, it is called free glutamic acid. Some foods, such as tomatoes, soy sauce, and Parmesan cheese, contain both bound glutamic acid and free glutamic acid. In the United States and Europe, on average, we eat 1 gram of free glutamic acid that occurs naturally in food per day and 0.3 to 1 gram from food additives per day.1

The FDA requires manufacturers to identify foods where MSG is added as a direct ingredient. 2 If the MSG occurs because free glutamic acid joins with sodium, as could occur when a food contains free glutamic acid, the list of ingredients is not required to include MSG.2

A condition called MSG symptom complex causes some people who are affected by MSG to experience symptoms such as a burning sensation in the back of the neck, forearms, and chest; dizziness; facial pressure or tightness; chest pain; headache; nausea; and a rapid heartbeat, particularly when they eat large amounts of MSG on an empty stomach.3 Of course, not everyone experiences symptoms when they consume MSG. Blood tests can't really show if a person is sensitive to MSG. If you experience symptoms when you eat foods that contain MSG, you may decide to also avoid foods containing autolyzed yeast extract because the free glutamic acid in this product can be easily converted into MSG.


1 Beyreuther K, Biesalski HK, Fernstrom JD, et al. 2007. Consensus meeting: monosodium glutamate- an update. Eur J Clin Nutr 61:304-13.

2 USDA Food Safety and Inspection Service. Common Questions.

3 Williams AN, Woessner KM. 2009. Monosodium glutamate 'allergy': menace or myth? Clin Exp Allergy 39(5):640-46.

QUESTION: "What is agave nectar? Is it better for me than sugar?" V.B., via e-mail

ANSWER: Agave nectar is a liquid sweetener produced from the juice of a succulent plant. It appears in vegan recipes as an alternative to honey. Some vegans use agave in place of granulated sugar because bone char can be used in the production of some granulated sugar. (See VJ, Issue 4, 2007, for more about sugar processing.)

Generally speaking, sweeteners-whether sugar, molasses, honey, maple syrup, high fructose corn syrup, or agave nectar-provide sugar and calories and not much else. Thus, agave nectar is really no healthier than other refined concentrated sweeteners. Too much sugar of any kind can take the place of more nutritious foods, increase the risk of gaining weight, heighten the risk of heart disease and diabetes, and cause tooth decay.

Agave is promoted as having a low glycemic index, which means that it is less likely to raise blood glucose levels excessively. This low glycemic index is due to the form of sugar found in agave-fructose. Fructose does not raise blood glucose levels as much as sucrose (table sugar) but has been associated with a number of health problems, including high triglycerides, gout, heart disease, and the metabolic syndrome.

The major issue with agave nectar and other sweeteners is the amount used. Americans, on average, eat the equivalent of as much as 30 teaspoons of sugar daily. That's close to 2/3 cup of sugar a day, approximately 480 empty calories. Recently, the American Heart Association recommended that a goal for most American men is no more than 150 calories of added sugars per day; a goal for American women is no more than 100 calories a day.1 Added sugars include those put into beverages and foods (in coffee, on oatmeal, etc.) and those added in food processing or preparation (breads, desserts, soft drinks, etc.). These limits are for all sugars, including agave, high-fructose corn syrup, molasses, maple syrup, brown sugar, and white sugar. So, if you prefer to use agave nectar as a sweetener, use it in moderation and recognize that it's just another source of added sugar.


1 Johnson RK, Appel LJ, Brands M, et al. 2009. Dietary sugars intake and cardiovascular health: A Scientific Statement from the American Heart Association. Circulation 120:1011-20.