'Natural' and other food labels that sound legitimate but may not be

Although the move is unprecedented for a nationwide restaurant, consumers are faced with deciding whether to choose GMO-free versions of common staples each time they go to the grocery store; everything from cereals to soups to sauces. Even foods that could never be genetically engineered to start with, such as salt, are being promoted as GMO-free.

And GMO-free is just one of the latest in a long list of food labels that includes gluten-free and organic items. Often they come at quite a markup, despite a shortage of health studies showing a clear benefit.

Just as concerning is that some of these labels can be slapped on packaging with little regulation by the U.S. Food and Drug Administration. For example, food and beverage companies can label their products "natural" without having to meet a clear definition by the FDA. In the absence of regulations, policy groups and consumer research often step in to tell us more about the safety and consistency of the latest wonder food (or label).

GMO or no

GMO-free labels are so pervasive at grocery stores that it would seem that genetic engineering is going the way of the GMO items at Chipotle. The reality is that the technology is widespread. Nearly all corn and soybeans grown in the United States are genetically modified.

The good news for consumers who are troubled by genetic engineering is that, at least from a human health perspective, they seem safe so far. "From the data that are available, there doesn't seem to be any concern with respect to human health and GMOs," said Alice Lichtenstein, the Stanley N. Gershoff professor of nutrition science and policy at Tufts University.

The FDA has reviewed 96 GMO-free plants, as of 2013, as part of the agency's process to ensure that new products, whether genetically modified or not, are safe. The FDA leaves it up to companies whether they want to feature a "GMO-free" or GMO-containing label. Requirements are, however, starting to happen at the state level. Vermont passed a law last month that will require all genetically modified foods to be labeled starting in July 2016; it will be policed by the state Attorney General's Office.

The U.S. Department of Agriculture announced on Thursday that it is working on a program that would allow food companies to apply to use a "USDA Process Verified" label. Companies would have to pay the department to verify that its product does not contain genetically engineered ingredients.

'Natural,' 'nutritious' and 'wholesome,' whatever they mean

Who doesn't want foods with these good-for-you-sounding labels? Just about everybody looks for these labels, which adorn cereal boxes, juice drink bottles and syrup jars. But almost nobody knows what they actually mean. A 2010 report by the Center for Science in the Public Interest described how consumers think foods with these labels are healthier when, in fact, they often are not.

Policy groups have urged the FDA to define what "natural" means and whether genetically modified foods would qualify. In the meantime, the agency said that it did not object to "natural" claims as long as products did not have added color, synthetic ingredients or artificial flavors. It has sent letters of complaint to many manufacturers, including to Nestle in 2009 because juice was not the main ingredient in its "Juicy Juice All Natural 100% Juice" product. Nestle did not respond to CNN's request for comments about this issue. Key Ingredient Market also received a letter in 2013 because its "All Natural" crab and artichoke spread contained imitation crab meat and artificial flavors, although the latter issue was resolved in 2014.

'Organic,' or at least mostly

Organic stickers and labels can be found up and down the meat, dairy and produce aisles at grocery stores, but not all labels are created equal. In general, organic foods have to come from animals that were raised with room to graze and without the use of hormones or antibiotics, which have created human health concerns, including the development of antibiotic resistance. Produce has to be grown without fertilizer or pesticides, the use of which may increase the risk of cancer and other diseases.

Beyond that, the specific categories of organic products require some decoding to understand. For a product to earn a "USDA organic" seal, it has to be 95% organic or more, and certified by the USDA that it is grown appropriately. However, processed foods can have a "made with organic (ingredients)" label if at least 70% of them are organically produced.

'Gluten-free'

The number of gluten-free products that line grocery store shelves would have you think that a high percentage of people could benefit from ridding their diets of these proteins found in wheat, rye and barley. There is not, and in fact, that percentage may be getting smaller.

It is estimated that 1% of people in the United States have celiac disease, an autoimmune condition that makes them very sick when they eat even a little gluten. Although an initial studysuggested that another 10% have a non-celiac form of gluten intolerance, more recent researchindicates that a different ingredient (a type of carbohydrate called FODMAP) was actually the cause of the pain, bloating and nausea associated with the condition.

Questions remain about whether a gluten-free diet can help people who do not have celiac disease or other, rarer gluten allergies. Many Americans still say that reducing or eliminating gluten helps them avoid headaches, stomach and joint pain, and other ailments. However aConsumer Reports survey of gluten-free products in January found that many of them have added sugar and fat. "It wasn't flattering to the gluten-free industry," said Lichtenstein, the nutrition science and policy professor.

Meanwhile, people who have celiac disease worry that the hype of being gluten-free has made the restaurant industry not take their medically necessary avoidance of gluten seriously. They should at least not have to worry about the food industry not taking gluten-free labels seriously. The FDA regulates this label to ensure that foods that are naturally or manufactured to be gluten-free actually are.

Modernizing 'ancient' and 'whole' grains

The promise of ancient grains, on bread bags and cereal boxes, may sound like music to the ears of processed-food-wary consumers. It is true that this group of foods, including quinoa, amaranth and spelt, has been changed little from the days that the Paleo Diet was how humans were said to have eaten. However, that does not necessarily mean that ancient grains are healthier than other grain-based foods. Eating ancient grains in their whole-grain form gives you more fiber and antioxidants, but then again, so does regular whole-grain wheat.

The problem is, trying to find which foods have high levels of whole grains is not always easy. Products that claim to be whole-grain might have only small amounts. Try to find those that list "whole grain," "whole oats" or "whole rye" as the first ingredient. Labels about the type or amount of grain in a product have to be accurate, according to the FDA.

And just because a product is "enriched" does not necessarily make it as healthy as if it contained whole grains. Although enriched flour has to contain a certain level of vitamin B, iron and folate, according to FDA regulation, it does not have the fiber and bran that are lost during refinement.

Also, as the National Foundation for Celiac Awareness points out, ancient grains are not necessarily safe for people with celiac disease. Spelt and Kamut contain gluten, and amaranth does not. So people who cannot tolerate gluten still need to take care when eating these grains.

Cracks in 'omega-3' egg claims

Eggs have joined the ranks of salmon and flaxseed as foods that are a good source of omega-3 fatty acids. Some eggs are high in this good-for-you fat, which has been shown to reduce inflammation and improve heart and brain health, because they come from hens whose diets are rich in flaxseed. However, eggs, whether high in omega-3 or not, have high levels of cholesterol, which could increase heart disease risk among sensitive groups, such as people with diabetes. One large egg has about 186 milligrams of cholesterol, more than half the recommended daily amount for a healthy person (300 milligrams) and almost the entire amount for a person with diabetes, heart disease or high cholesterol (200 milligrams).

A study by the Center for Science in the Public Interest in 2007 found that many omega-3 eggs do not contain these fats in the forms (DHA and EPA) that have been linked to reduced heart disease. For example, Land O'Lakes says its eggs are a good source of ALA omega-3, although it is unclear if this form is as beneficial as DHA and EPA. The company did not respond to CNN's request for comments about this product.

'Trans fat' taboo

Trans fats are considered the very worst for heart health. Although they are hard to avoid in foods such as meat and dairy, in which they naturally occur, you might be able to sidestep them in packaged foods. Some chips (Doritos, Cheetos) and cookies (Voortman) promise to contain zero grams of trans fat.

Products are required by the FDA to list the amount of trans fat they contain on the nutrition label; less than half a gram rounds down to 0 and the packaging can boast its lack of trans fat. In the fall, the FDA announced that it was removing partially hydrogenated oils, which are the major source of added trans fat, from its list of Generally Recognized as Safe (GRAS) products. Food manufacturers will have to reformulate foods that contain these oils or petition to the FDA that they are indeed safe.

Cutting out BPA-lined cans

BPA sneaks into our diet not through foods and drinks, but the packages they come in. Some of the main sources are plastic bottles and metal food cans, which are often lined with resin containing the chemical. Studies have shown that the chemical, which mimics estrogen, can impair fertility in men and women and also lead to developmental delays in children.

In 2012, the FDA banned the use of BPA in baby bottles and sippy cups. The levels of the chemical in products for adults, on the other hand, are low enough that the FDA does not consider them a health risk. Nevertheless, several companies, such as Eden Foods, Muir Glen and Amy's, have voluntarily started using BPA-free cans. And they don't miss the opportunity to put that on their labels. Companies such as Del Monte have also said they are testing BPA alternatives in can liners.

Chilling chicken safety

A peculiar label can be found on some packages of raw chicken: "air chilled." It means the animal was refrigerated, and sometimes misted, to cool it down after slaughter. It is an alternative to the more typical method of dipping the bird into a water bath with chlorine.

In terms of food safety, there does not appear to be much difference between air-chilling and the chlorine method. A 2012 Consumer Reports study suggested that air-chilled poultry had lower levels of two bacteria commonly found in chicken, salmonella and campylobacter, although the study was small. The bad news is, regardless of the cooling method, that study reported that two-thirds of broiler chickens had salmonella and campylobacter. Just a reminder to make sure you cook your chicken up to at least 165 degrees Fahrenheit.