What You Need to Know About GMOs

Medically Reviewed by Brunilda Nazario, MD on April 08, 2016
From the WebMD Archives

Genetically modified organisms -- plants and animals whose genes have been changed by scientists -- aren't just thought over, they're fought over. GMOs often make news related to the environment, world hunger, the economy, politics, and yes, even health.

Those against them say eating foods made from GMOs is bad for you. Those in favor argue that you're way better off from the benefits that GMOs and other science-based innovations bring to the farm, the store, and the table.

A 2015 survey by the Pew Research Center shows this divide. Nearly 9 out of 10 scientists from the American Association for the Advancement of Science say GMOs are "generally safe" to eat. Though if you're like more than half of U.S. adults from the general public in that same survey, you think you probably shouldn't eat them.

People disagree about when you should call something genetically modified. They argue about whether or not food made with GMOs should be labeled. They debate the long-term effects that producing and eating them will have on our planet and our bodies.

So what do you need to know to make good choices for your health?

Nature on Fast-Forward

Let's start with the basics. Changes to genes aren't necessarily a bad thing. They happen in nature. In fact, no matter what's on the menu, it isn't exactly the same as what grew hundreds or thousands of years ago.

Bits of DNA, called genes, are responsible for all sorts of characteristics and traits in every living thing, from height to how certain cells work. Useful traits help the plants and animals with them survive or thrive better than ones without them, so they get passed along and eventually become common.

Our ancestors sped up the process when they saved seeds of cream-of-the-crop plants to grow the next time, and the next, and the next. That's what turned small bunches of tiny kernels on tall grass 10,000 years ago into the big ears of juicy corn on the cob we have today. With animals, picks of the litter were paired to breed "new-and-improved" babies.

Faster still -- bypassing many, many generations and seasons -- are the ways that scientists create today's genetic changes, or modifications. They alter the DNA of seeds with radiation or chemicals, then choose which resulting plants to breed.

Or they can snip a gene (or several) from a plant, virus, or bacteria and plug it in to another to transfer a desired feature. These more precise and targeted adjustments, often referred to as genetic engineering, create what people typically think of when they hear "GMOs." Sometimes scientists move genes that come from the same kind of thing, like from one tomato plant to another. But they can mix different species, too, like a virus and a tomato plant.

Why Bother?

Mixing plant species is how we've gotten papayas free of viruses, corn plants that survive drought, soybeans that stand up to weed killer, potatoes that don't bruise, and crops that yield more and cost less. That's good news for our food supply and the business of farming.

Some GMOs are specially made to be packed with extra vitamins, minerals, and other health benefits. For example, Swiss researchers created a strain of "golden" rice with a lot of beta-carotene, an antioxidant good for your eyes and skin. Soybeans whose fats have been changed so they're more like olive oil can be turned into a heart-healthy replacement for oils with trans fats that's more heat-tolerant and better for cooking. And those bruise-free potatoes are supposed to cut down on cancer-causing chemicals created when spuds become french fries.

Some biotech companies are doing experiments to make meat better for us, such as boosting the amount of omega-3-fatty acids in it. These essential fats help prevent heart disease and stroke and may protect against cancer and other conditions. They may also help control lupus, eczema, and rheumatoid arthritis. But your body doesn't make them, so you have to get them from food.

As the population grows, it's going to get harder to feed everyone. The Food and Agriculture Organization of the United Nations (FAO) estimates food production will need to double in some parts of the world by 2050. GMOs are one way to make enough nutritious food available with limited land, water, and other resources.

But people worry about pollen and seeds from genetically engineered plants spreading beyond the fields where they were planted. Or what could happen if genetically modified animals mate with non-modified or wild ones.

Are They Safe?

Many critics think of the DNA in GMO-based foods as if it's toxic, a bad thing, says Alison Van Eenennaam, PhD, cooperative extension specialist in animal genomics and biotechnology at the University of California, Davis. As unappetizing as it may sound, "DNA has always been part of our diet, and it's digested in your stomach along with the rest of your food," she says. "There is not some evil trace of poison."

We got ruby red grapefruits through natural mutation, yet "few are questioning the safety of all the random genetic changes that went into their development," says Kevin Klatt, a PhD student in the molecular nutrition program at Cornell University. What seems to make people uncomfortable is when those changes happen deliberately in a lab.

A group of scientists did an extensive review of research on the safety of crops from GMOs over the past 10 years. They found no significant harm directly tied to genetic engineering.

And the American Medical Association thinks genetically modified foods are OK. Part of an official statement notes that in almost 20 years, no clear impacts on human health have been reported or confirmed in professional journals.

The World Health Organization agrees. They, along with the FAO, maintain a set of science-based standards, guidelines, and practices called the Codex Alimentarius to promote good, safe food for everyone. It includes biotechnology and genetic engineering, too. Many governments draw from the Codex to write their regulations and recommendations.

But there are still big differences of opinion, even among some scientists and doctors.

Stephen MacDonald, PhD, a biotechnology and business strategy consultant, agrees that all foods -- at the most basic level -- are made of the same stuff. Even so, he doesn't dish up GMO-based foods for dinner because he's not convinced they have the same exact nutritional value. "I don't think they are dangerous per se, but I don't trust the data that says they are entirely safe either," he says.

"But," Klatt says, "there is no evidence that exposing foods to chemicals or radiation is 'safer' than methods of genetic engineering." Over the last 60 years, these approaches to causing genetic changes in seeds has given us around 3,000 altered crops. Why isn't there as much fuss over them? "The public might be less familiar with traditional breeding techniques and therefore less concerned," he says.

The Role of the FDA

The FDA's job is to make sure all food -- genetically altered or not -- is safe to eat.

Through the Plant Biotechnology Consultation Program, the FDA raises safety concerns during the engineering process and helps developers identify the kinds of testing they should do.

A team of FDA scientists reviews information provided by the developer. They look at how a genetically engineered food compares to the original. Is it different nutritionally? Did the new genes introduce something that could be harmful? For example, a soybean enriched with a protein from a Brazil nut wasn't brought to market, even as animal feed, because tests showed that it might trigger a reaction for people with an allergy to those nuts.

You can't catch a disease or get a virus from a plant, but every now and then one makes its way from animals to humans, like swine flu and bird flu. Because animal viruses may be used in genetic engineering, some people worry they could infect humans or other animals that eat meat produced this way.

That's why the FDA takes a slightly different approach with genetically engineered animal products. They've issued guidance to help developers meet the high standards of the Codex Alimentarius and U.S. food safety regulations. The Center for Veterinary Medicine makes sure the animal is different in the way the developer says it is and that it's safe to eat. The FDA is also required by the National Environmental Policy Act to consider potential significant impacts of GMO animals on the environment, like how easily they could spread disease.

For a genetically engineered salmon that grows to full size in about half the time it normally takes, the FDA wanted to know how likely these fish would be to mix with ones whose genes haven't been tinkered with and how likely they would be to survive and reproduce if they did. To minimize the risks, the developer raises the salmon in secure facilities in Canada and Panama. The tanks aren't connected to any body of water, and they have barriers such as screens and nets to prevent fish and eggs from getting out as well as birds and other predators from getting in. The salmon grown for food are sterile.

A GMO food isn't allowed in stores in the U.S. until the FDA team is satisfied it's safe. Ultimately, the developer is legally responsible for the food's safety, like any other product we eat.

Can GMOs Change Your DNA?

Even though it's never happened before, some people fear that you could become genetically modified from eating GMO food. But genetic material doesn't get tacked on like pin the tail on the donkey. An "added" gene isn't going to fall off and get stuck to yours.

Bacteria-fighting enzymes and processes in your body are designed to prevent a genetic invasion. As a report from the American Medical Association's Council on Science and Public Health explains, if an outside germ somehow survived digestion and got into your gut bacteria, it would have to be enough like your own DNA, in just the right place at just the right time, to glom onto one of your genes and change it.

To put things in perspective: It's just as possible (or impossible) for non-GMO foods to change your genes. Anything you eat has DNA that's "foreign" to you.

Even so, scientists take great care not to use genes that have any hint that they might cause problems.

What's in Your Food?

Even though you may not realize it, you probably eat GMOs now. Up to 80% of processed foods in the U.S. have them.

Most of the sugar we eat comes from beets, and almost all of them are GMOs these days. Changing their genes has brought about bigger, better sugar beets that are stronger and last longer than those grown in the past.

And whatever the source, "It's just sugar or sucrose. No DNA, no protein," Van Eenennaam says. "There isn't something different or extra in sugar that comes from a bioengineered sugar beet." Nothing in the sugar can tell you where it came from. You can't avoid eating "genetically engineered sugar" because it doesn't exist, she explains.

Engineered corn is the source of a lot of cornstarch used to thicken soups and sauces as well as the corn syrup that sweetens foods and drinks. Cottonseed, canola, and soybean oils made from GMOs go into mayo, salad dressing, cereal, bread, and snacks galore.

But way more GMOs -- as much as 90% of what's grown -- are used as animal feed. Studies show there is no difference in the makeup of meat, milk, eggs, or other food that comes from animals who've been fed them.

And the animals themselves are just as healthy as those that eat non-GMO meals. The FDA looks out for them by testing the safety of animal feed, too.

Can You Avoid Them?

China, Australia, and the European Union require GMO foods to be labeled, but the U.S. doesn't. Many states are in the process of passing laws about the labeling and sale of genetically engineered food, but some federal lawmakers are trying to overrule them and prevent that.

The FDA favors voluntary labeling and has published recommendations for manufacturers. The agency also takes public comments about this guidance and is considering some citizen petitions.

The question of what could need a label is another sticky subject. Foods created by changing genes with radiation or chemicals don't fall under GMO regulations and wouldn't have to be labeled. The latest methods of genetic engineering aren't covered by older rules, so you won't see labels on those foods either. But the National Academy of Sciences says this inconsistency doesn't make sense: What matters is the fact that genes have been artificially changed, not the way it was done.

If you want to stay away from GMOs, eat only fresh, whole, unprocessed foods marked "certified organic" or "USDA organic." That's how MacDonald shops. But the makers of these foods tag them on the honor system, and they're not checked by the government. And it's OK for these claims to appear on foods developed from genes originally altered by chemicals or radiation.

Claims of "non-GMO" and "GMO free" can't be scientifically or legally supported by any testing methods. But the nonprofit Non-GMO Project has independently certified specific foods and products from more than 1,900 brands as made with best practices for avoiding GMOs: Look for the Non-GMO Project Verified seal.

In the produce section, only a few things might be GMOs:

  • Edamame
  • Papayas from Hawaii
  • Summer squash
  • Sweet corn
  • Zucchini

The faster-growing salmon, which the FDA cleared in November 2015 after several years of study, will probably be the first animal GMO in the supermarket, after guidelines are set for how to label it. Even if that happened today, it would be months or years before you could buy any.

Stores like Earth Fare, The Fresh Market, Sprouts Farmers Market, and Whole Foods want to make sure their customers know what they're buying and have choices. These grocers offer their own non-GMO products as well as stocking other brands without GMOs. When you're dining out, your best bet is a restaurant that uses organic ingredients.

The Great Plate Debate

The overwhelming science so far says that GMOs won't hurt us. But concerns like the chance -- however unlikely -- that GMOs may cause genetic changes, allergies, or other serious harm to your health leave room for further study. There could be consequences no one thought to look for, or traits scientists can't test for yet, or worst-case scenarios reviewers hadn't considered.

For his peace of mind, MacDonald would like to see more careful, well-designed studies done in unbiased academic settings, free from the influence of politicians and special interest groups.

WebMD Feature



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