If, like many Americans, you stock your pantry with processed foods, you may worry about how safe food additives really are.

Over the years, the safety of many food additives, from food dyes to trans fats, has come into question. A scare over a food additive may linger in our minds long after researchers find that there's actually no cause for alarm. It can take years, or even decades, to find out the truth, and sometimes the case is never really closed.

To help you figure out what s safe, WebMD took a look at the latest research on seven of the most controversial food additives. Here's what we found:

What Should I Eat?

Q. “I have heard that phenylalanine is very bad for you and that is why it has become part of the ingredients listed (on food products). I have never read anything about it. Could you please explain what it is?

And are artificial sweeteners bad for you? Is Splenda the only good sugar with no calories? Is the Wal-Mart generic brand of Splenda that I have been eating OK?"

A. "Straight Answers about Aspartame," an American Dietetic Association fact sheet from 2006, defines aspartame as "a low-calorie sweetening ingredient that provides the sweet taste without the calories."

When aspartame breaks down in our body, it forms the amino acids aspartic acid and phenylalanine and also a small amount of methanol. The same substances may also be found in milk, meat, fruit and vegetables - only in larger amounts. Your body digests these substances similarly whether from foods or aspartame.

“Non-nutritive sweeteners, including aspartame, are used in a variety of food and beverage products. Aspartame is approved for use in more than 400 countries, including the United States, Canada, countries in the European Union, Japan, Australia and New Zealand,” said Robert Brackett, chief science officer for GMA. “Few ingredients have been subject to the extent of research that has been conducted on aspartame and the overwhelming majority of the scientific evidence confirms its safety.”

This fact, confirmed by a team led by Mt. Sinai neuroscience researchers (Margolskee et al, Proceedings of the National Academy of Sciences 104(38):15075), is significant given the enthusiastic media coverage of a rat study earlier this year suggesting that rats fed diets with added saccharine gained more weight than those that did not. This coverage was quickly and almost gleefully extrapolated for its “implications” to virtually any human who may enjoy the taste of a diet soda.

Please click on the links below for copies of the following materials:

• Report conclusions
• University of Maryland press release
• Informa Healthcare/Critical Reviews in Toxicology press release
• Aspartame Resource Center press release
• Informa Healthcare/Critical Reviews in Toxicology Web site
• American Dietetic Association comment