A significant percentage of many food crops contain GMOs, or genetically modified organisms.

As much as 80 percent of conventional food contains GMOs, according to the Non-GMO Project, and that can make it challenging to avoid these controversial products.

The U.S. Department of Agriculture announced in early May 2015 that it would begin certifying foods that are GMO-free through the Process Verified Program, and those foods will be labeled, NPR said. The Non-GMO Project also has a verification seal that shoppers can look for on their foods.

More consumers are demanding labels that indicate whether or not foods contain GMOs.

“As this issue gains traction with consumers, lots of Americans are wary of GMO foods. And more are just flat out confused about what they are, where they are in the food supply and whether they're dangerous,” NPR wrote.

If you want to avoid ingesting GMOs, here are the top five food crops to drop from your diet:

1. Soy: “Up to 90 percent of soybeans in the market have been genetically modified to be naturally resistant to an herbicide called, Round Up,” according to Cornucopia.

2. Corn: About 85 percent of the corn acreage planted in 2013 was herbicide-tolerant corn, the Economic Research Council of the USDA reported.

3. Cotton: About 90 percent of the cotton crop planted in 2011 came from GMO seeds, the Non-GMO Project said.

4. Canola Oil: “Canola oil is derived from rapeseed oil. It is considered one of the most chemically altered oils sold in the U.S.,” Cornucopia said.

5. Sugar Beets: In June 2008, the Organic & Non-GMO Report said the sugar beet industry converted 100 percent to GMO sugar beets. The Non-GMO Project said about 95 percent of the sugar beets crop was GMO in 2011.

In addition to those five crops, Cornucopia reported that much of the milk on the market contains GMOs.

“One fifth of the dairy cows in the United States have been given growth hormones to help them grow faster and increase their yield,” the website said. “These hormones can be found in some of the milk produced by these cows. These growth hormones have been shown to act inside the human body.”

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