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Actress Gwyneth Paltrow was on Capitol Hill Wednesday to urge members of Congress not to block states from adopting labeling laws on foods made with genetically modified organisms (GMOs).

She is part of a larger group of GMO labeling advocates, such as the Environmental Working Group and Just Label It, who are pushing for consumers to have more information about their food --and she's joined by an army of celebrity heavyweights, including Paltrow's mother Blythe Danner, Daryl Hannah, Lena Dunham and Tom Colicchio who are demanding the “right to know.”

This comes amid a growing food fight in Congress over the labeling of GMO foods.  Last week, the House of Representatives passed a hotly contested bill that would block states from requiring labels identifying food made with genetically modified ingredients. The bill is named the Safe and Accurate Food Labeling Bill, but critics have dubbed it “Deny Americans the Right-to-Know” or the DARK act, and it comes as a growing number of states take up legislation requiring GMO labeling. Vermont, Maine, and Connecticut already have passed laws requiring GMO labeling. A similar bill is expected in the Senate.

Labeling advocates say that about 70 percent of processed food in the U.S. contains at least one GMO ingredient and cite studies linking GMO consumption to serious medical conditions such infertility, gastrointestinal disorders, immune problems and cancers.  This comes as a slew of food companies, including Chiptole, Whole Foods and Trader Joe's are vowing to cut GMO products.

Lobbyists representing big food companies like General Mills, Kraft, Monsanto and Coca-Cola have spent a reported $51 million to prevent GMO labeling.  These companies charge that the studies label advocates cite are flawed, and they point to their own research showing that GMO foods pose no proven health risks. In addition, they claim that a GMO label does not tell consumers what they really want to know, such as which pesticides or toxins your food has been exposed to, and only perpetuate the notion that GMOs are unsafe.

When it comes to GMOs, there is plenty of confusion among consumers.

And wherever you stand on the debate, the majority of Americans –57 percent --believe that GMO foods are “generally unsafe,” according to a Pew Research Center study.

Here are some of the facts surrounding the debate to help you break it down.

What is a genetically modified food?

The World Health Organization defines GMOS as “foods derived from organisms whose genetic material (DNA) has been modified in a way that does not occur naturally, e.g. through the introduction of a gene from a different organism.” Though most modifications occur from other plants, its conceivable that genetic material from animals could also be used. Over the years, GMOs have led to higher crop yields by ridding crops of certain diseases and increasing tolerance to pesticides.

In the U.S. there are currently only nine GMO crops available for commercial consumption: corn, soy, papaya, yellow squash, alfalfa, canola, cotton, sugar beets, and zucchini.

But the larger issue really pertains to foods-- especially those that have been processed-- that contain one or more of these ingredients. A quick glance at the ingredients on most cereals, snack foods or frozen dinners will likely list a derivative from corn or soy.

Are GMOs safe?

This answer varies wildly depending on whom you ask, and both sides are fast to cite research that helps argue their point.

While we won’t get into specific studies, it’s important to note that many health organizations and the U.S. Department of Agriculture consider GMOs safe for human consumption.  The WHO that “GM foods currently available on the international market have passed safety assessments and are not likely to present risks for human health. In addition, no effects on human health have been shown as a result of the consumption of such foods by the general population in the countries where they have been approved.”

Those who oppose GMOs cite research (see some here and here) that genetically modified food could cause allergies, antibiotic resistance, interfere with immune system and create the possibility of super weeds.  They also say that GMO crops have a lasting negative impact on the environment and labor practices.  And, in general, they urge for more testing to evaluate the long-term effects of consuming GMOs.

What do current labels tell us?

There are currently no federal laws requiring GMO food labeling.  Consumers looking to avoid GMO food can buy USDA Organic food, since under the law no genetically modified ingredients are allowed under the organic certification guidelines.

In addition, food companies may voluntarily label foods as GMO.  The most common way is by use of the "Non-GMO Project Verified" seal started by the Non-GMO Project, a private nonprofit of retailers that verify their products contain fewer than 1 percent GMO ingredients.

In 2014, Vermont became the first state to require mandatory GMO labeling but the law doesn’t go into effect until 2016.

The pros and cons of labeling GMOs

First the pros:  Supporters say they have a right to know what’s in their food and a GMO label gives them one more element to make an informed decision about what they buy.

“Producers already must label foods that are frozen, from concentrate, homogenized, or irradiated,” Jean Halloran, director of food-policy initiatives at Consumers Union, told Consumer Reports. “GMO labeling is one more piece of helpful information.”

Also, many anti-GMO advocates argue that the labeling goes beyond food safety and more transparency in the food supply.  These advocates tend to believe that pesticide reductions and higher yields can be obtained through more natural farming practices, such as organics-- not through genetic modification.

Now the cons:

Opponents say that labeling foods containing GMOs will not tell consumers what they really want to know, such as if pesticides or herbicides were used-- or if large agricultural companies produced the crop. Vocal opponents of GMO food, including major food producers which manufacture products with genetically modified ingredients, say labeling only confuses and frightens customers.

Should consumers care?

Yes. If you haven't heard much about GMO before now, get ready to be inundated with information from both sides. Why? GMO labeling is really about a much broader debate on the public’s health as well as the sustainability of the world’s food supply-- and the social, economic and political forces behind it.