Even if you try to eat as healthy as possible, unless you do all of your shopping at a farmer's market and have a butcher and a dairy farmer you trust and rely on, chances are you're eating packaged foods to round out your meals. Unfortunately, there are a ton of ingredients in packaged foods to help make them look appealing, taste better, and withstand travel and shelf life. While the FDA has approved the foods on this list as "safe," some of them may make you think twice before you eat them again.

"Today, our foods and our ingredients come from thousands of miles from different countries already prepared for us," says Kantha Shelke, PhD, Chicago-based food scientist at Corvus Blue LLC, a food science and research firm specializing in industry competitive intelligence. "That is a very tall order for something that exists in nature because the minute it is harvested, it's on its way to decay and dying." Because consumers expect food to look unblemished and freshly picked or slaughtered, processing plants and manufacturers have to do more and more to make the food look like it was freshly made for you, and to help make it last longer, says Shelke.

Translation: Even foods that you think of as unprocessed have been manipulated in ways you might not expect. The best thing you can do is try to educate yourself about what you're eating, and, when in doubt, eat whole, natural foods whenever possible.

Here, the most surprising ingredients in the food you eat -- and how to avoid them.

Image via Harper's Bazaar

"When it comes to processing the meat itself, one thing that surprises people is extra water and salt to give the meat some characteristics and to 'plump things up,'" says Patty Lovera, Assistant Director, Food and Water Watch, in Washington, D.C. Chicken and pork are often injected with a saline solution to make it more tender, plump and flavorful. It also, claim some watchdog groups, makes the meat weigh -- and cost -- more. Pork is called "the other white meat," because they wanted to be an alternative to chicken with their advertising in the late 1980s. "That pushed pigs to have less fat," says Lovera. Fat adds a lot of the flavor in meat, so they had to do something else to improve the flavor -- hence adding salt.

Bottom line: If you're following a low-salt diet for your health or want to decrease sodium in your diet, check ingredient labels for words like "flavor-enhanced" or "added sodium."

Though you're not going to be swallowing splinters as part of your Italian meal, grated Parmesan cheese often contains the ingredient cellulose, a common anti-clumping agent made from wood pulp, which the FDA officially classifies it as "generally recognized as safe" (GRAS).

"Cellulose is a safe additive, and an acceptable level is 2 percent to 4 percent," Dean Sommer, a cheese technologist at the Center for Dairy Research in Madison, Wisconsin, told Bloomberg when the story first broke. The cheese companies who got in trouble with the FDA had too much cellulose in their products.

Still, says Lovera, consumers are likely to have legitimate concerns. "You worry about how no one makes human-grade sawdust. It didn't come from a supply chain designed for people to eat, [so] where would I get it?" she says. One might also wonder, "Why does my body need it?" says Lovera.

Bottom line: If you're concerned about cellulose in your cheese, buy a hunk of fresh cheese and grate it yourself.

Cellulose is an ingredient you can find in cereals, breads and foods with added fiber. It's oftentimes in "lighter" or "low-calorie" breads.

According to the FDA, "Cellulose derivatives ... are virtually unabsorbed, and little or no degradation of absorbable products occurs in the human digestive tract. ... Consumption of large amounts appears to have no effect other than providing dietary bulk, reducing the nutritive value of such foodstuffs and possibly exerting a laxative effect."

In other words, humans can't digest cellulose, says Shelke. "You're better off getting fiber that's naturally occurring in veggies, grains and different kinds of foods." The worst thing that added fiber by way of wood pulp can do is cause flatulence and bloating, explains Shelke.

Bottom line: If you're eating packaged food that touts high fiber, check the label to see if it has cellulose.

Anything that's ground up or made into a paste -- like hotdogs, sausage, chicken nuggets, ground beef or ground turkey -- is usually made from dozens of different animals, says Lovera. If you're eating a chicken nugget, for instance, that patty is often made up of ground-up chicken parts that the manufacturer couldn't use for any other purpose. On the plus side, "you could look at it as addressing a food waste issue -- you're using up the leftover pieces," says Lovera. However, if there's a food poisoning outbreak, it's virtually impossible to trace back to the supplier, she explains.

Bottom line: No one's saying we thought chicken patties were healthy, but keep in mind most foods that comes in a casing (like hotdogs and sausages) are probably from a few different animals. You might be better off researching a local butcher and talking to them about the farms their product comes from. The more transparency you can get and informed you are about where your food is coming up, the more you'll know about what's likely to be in your food.