Elizabeth Weise

USA TODAY

SAN FRANCISCO — Genetically engineered crops are safe for humans and animals to eat and have not caused increases in cancer, obesity, gastrointestinal illnesses, kidney disease, autism or allergies, an exhaustive report from the National Academies of Science released Tuesday found.

Work on the 388-page report began two years ago and was conducted by a committee of more than 50 scientists, researchers and agricultural and industry experts convened by the National Academies of Sciences, Engineering, and Medicine. It reviewed more than 900 studies and data covering the 20 years since genetically modified crops were first introduced.

Overall, genetically engineered (GE) crops saved farmers in the United States money but didn’t appear to increase crop yields. They have lowered pest populations in some areas, especially in the Midwest but increased the number of herbicide-resistant weeds in others. There’s also no evidence that GE crops have affected the population of monarch butterflies, the report said.

The review was thorough and systemic, assessing many of the issues that have been raised about genetically engineered crops over the years, said Gregory Jaffe, director of biotechnology at the non-profit watchdog group the Center for Science in the Public Interest in Washington D.C. The group was not involved in the report's creation.

Questions and Answers on GMO crops

The genetic material of GE plants is artificially manipulated to give them characteristics they would not otherwise have. The two most common are pest resistance and the ability to withstand certain herbicides. That allows farmers to spray fields with herbicide, killing weeds while not harming the crops. Drought tolerant traits are newer and also becoming popular.

The report, "Genetically Engineered Crops: Experiences and Prospects," was meant to be an objective overview of current research into the safety and environmental and social effects of these increasingly popular crops and the foods made from them.

Safe for humans

To gauge whether foods made from genetically modified crops were safe for human consumption, the committee compared disease reports from the United States and Canada, where such crops have been consumed since the mid-1990s, and those in the United Kingdom and western Europe, where they are not widely eaten.

No long-term pattern of increase in specific health problems after the introduction of GE foods in the 1990s in the United States and Canada was found.

There was no correlation between obesity or Type II diabetes and the consumption of GE foods. Celiac disease, which makes humans intolerant of gluten, increased in both populations. Patterns in the increase in autism spectrum disorder in children were similar in both the United Kingdom and the United States, the committee reported.

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Overall the report concluded that there were no differences in terms of a higher risk to human health between foods made from GE crops and those made from conventionally-bred crops.

Critics: too much industry influence

Groups opposed to genetically engineered crops criticized the report for arriving at watered-down scientific conclusions due to agricultural industry influence.

Food & Water Watch, a government accountability group in Washington D.C., said the committee's ties to the biotech industry and other corporations create conflicts of interest and raise questions about the independence of its work.

“Critics have long been marginalized,” said Wenonah Hauter, the group’s executive director.

Economic and ecological effects

Overall, the report found that GE crops save farmers money in terms of time spent tilling and losses to weeds and insects, but can have both positive and negative effects on pests, farming practices and agricultural infrastructure.

Pest-resistant crops have resulted in lower pest populations overall in some areas of the midwest, especially European corn borer, the report found.

However the use of herbicides on GE crops in some areas has resulted in the evolution of herbicide-resistant weeds.

Despite claims by some proponents of GE crops, their adoption didn't appear to increase yields overall among U.S. farmers, the report found.

The report specifically addressed a commonly cited link between GE crops and falling populations of monarch butterflies.

As of March 2016, there was no evidence that the suppression of milkweed (the only food of the insect in its caterpillar state) by the use of herbicides caused declines in the monarch population, the committee found. In fact, the monarch population has seen a moderate increase in the past two years. Still, the report called for continued monitoring of the situation.

Mostly cotton, soy and corn

There are only 12 genetically modified (GM) crops grown commercially grown worldwide according to the report. The vast majority of GM acreage is concentrated in cotton, soybeans, corn, sugar beets and canola.

In the United States, the list of commercially grown GM crops includes cotton, soy beans, corn, sugar beets, canola, alfalfa and papaya, in addition to small amounts of zucchini and yellow summer squash, apples and potatoes.

However four of them are extremely popular with farmers. In 2015, 99% of sugar beets, 94% of soybeans, 94% of cotton and 92% of feed corn grown in the United States were genetically engineered to either be herbicide or pest resistant, or in some cases both, according to the International Service for the Acquisition of Agri-Biotech Applications.

Globally, 12% of all cropland is planted with genetically engineered plants, according to the report.

However there has been significant pushback against these crops, particularly in Europe.

GMO-free a selling point

A significant portion of American consumers are concerned about the safety or other effects of foods made with genetically modified crops, often called GMOs for genetically modified organisms.. A survey released last year by the NPD Group, a market research firm, found that 57% of Americans were concerned that genetically modified foods posed a health hazard.

The food industry has taken notice. In 2015, Progressive Grocer, a trade publication, reported that total U.S. sales of food and beverage products labeled “non-GMO” reached $10 billion during 2014.

Labeling foods as GMO-free has become a popular marketing and differentiation method for companies. The Non-GMO Project, a labeling program, has almost 35,000 verified products, according to its website.

Packaged Facts estimates that the global food and beverage market was worth more than $5 trillion in 2014 and that non-GMO products accounted for $550 billion of that. It projects that the global market for non-GMO foods and beverages will reach to $1 trillion by 2019.

The National Academies report will likely not sway these consumers, said Phil Lempert, a Los Angeles-based food industry analyst.

“It’s an emotional issue, it’s not a science issue,” he said.