Food labels have been around for decades, and every day they get more and more complicated. Here’s the lowdown on some popular eco-friendly terms and what they mean, if anything.

Antibiotic-Free: No antibiotics were used on this animal during its lifetime to prevent or treat disease. According to the National Dairy Council, a sick cow can be treated with antibiotics, but the milk will not be used from that cow until tests show no antibiotics present.

Cage-Free: You’ll see this one on egg cartons especially. It means birds were raised without cages, but it doesn’t guarantee they were able to go outside. The term is lightly regulated, and companies get permission to use it on their packaging labels from the Food Safety Inspection Service of the Agriculture Department, which doesn’t actually inspect these operations. A New York Times article from 2007 has some interesting insights into which chefs and food companies are now using cage-free birds.

Free-Range: This indicates that birds — chicken, turkey, quail and other edible fowl — have free access to the outdoors. However, guidelines are loose on how long animal can be outdoors and the size of the area.

GMO-Free: This means a fruit, vegetable or grain has not been genetically modified — or a packaged food has no GMO foods included. Many companies label their foods GMO-free, and in most cases, organic foods and produce from your local farmer are GMO-free. Learn more from another post we did on the GMO controversy.

Grain-Fed: This label applies to beef products especially and means the cattle was raised on a grain diet (possibly with added supplements) instead of their natural grass diet. Studies have shown that meat from animals raised on grain-fed diets contains less vitamin E, vitamin C, beta-carotene and omega-3 fats. Often GMO grains and soy are included.

Grass-Fed or Pasture-Fed: These animals have grazed on the pasture and eaten grasses with no other supplements. A study published in the Journal of Animal Science concluded that grass-fed animals produce lower-fat and lower-calorie meat, a higher amount of omega-3 fats and higher levels of vitamin E (as much as 4 times that of grain-fed!). Check out this article going more in depth on the differences between grain and grass-fed animal products.

Natural: This one is a real toughie. The term “natural” is open to interpretation by food companies and doesn’t guarantee that the food is healthy or environmentally conscious at all. Usually it means foods that undergo minimal processing and don’t contain artificial colors, flavors and other synthetic ingredients. The term is so loosely used that a soda company labeled a drink with high-fructose corn syrup “natural”; after much controversy and debate, the FDA claimed products containing HFCS couldn’t be labeled “natural.” You’ll often see the word “natural” on personal care products, too — again, it doesn’t always mean it’s safer.

No Added Hormones and Hormone-Free: These animals were raised without receiving growth hormones. If beef is USDA-certified organic, it contains no hormones. Milk-producing cows may be given the growth hormone rBGH, which many worry may be transferred to us when we eat milk, cheese or other dairy products. You can find hormone- or rBGH-free milk on your market shelves.

Organic (or Certified Organic): These foods were grown without conventional pesticides, fertilizers, herbicides, hormones or antibiotics. It is expensive to certify a farm as organic; some local farms can’t or don’t want to spend the money to certify themselves but may be following organic practices. Talk to your local farmers to learn more. Organic foods have a higher price tag and organic doesn’t always mean “healthier.” Check out our tips on shopping for organic foods.