GMOs: The Pros & Cons of Genetically Modified Food

Large GMO Apple Compared to Small Regular Apples
July 9, 2013 (Updated: September 18, 2017)
Leigh Erin Connealy, M.D.

More and more of my patients are asking for my opinion on GMOs, the acronym for genetically modified organisms. Are these foods harmful, and, if so, how bad are they?

Those are very good questions, so let’s take a look at the issue…

GMO foods have been on the market for nearly 20 years, since 1996. During those years, most of us have eaten GMOs in many foods, from soybeans, beef, dairy products, corn, beets, sugar, cottonseed, and rapeseed, which is used to make canola oil.

The USDA reports that about 94 percent of all soy and 75 percent of all corn grown in this country is genetically modified. Meanwhile, experts estimate that as much as 75 percent of the processed foods sold in this country contain GMO ingredients.

What Is a Genetically Modified Food?

The process of genetic modification involves inserting a gene from bacteria or a virus (or a gene that helps plants survive the application of highly toxic pesticides) into an organism where it would normally not be found. The purpose is to alter the genetic code in plants and animals to make them more productive or resistant to pests or farming techniques, like being doused with chemicals that would ordinarily kill them.

Soybeans that have been genetically modified, for example, can survive applications of herbicides that would destroy an organic soybean plant. Similarly, you might have read headlines recently about the controversy over genetically modified salmon. In this case, fish genes are tweaked with a growth hormone that causes the fish to double in size far more quickly than it usually would, so fish farmers can increase their profits. So far the GMO fish have not been approved for our food supply, but I cannot say with any confidence that it will never happen.

What’s the Problem?

Strengthening soybeans and fattening fish might not seem controversial on the surface, but there are some very real concerns here. Understand that the issue of GMOs is quite complicated. I’ve created the chart below to help clarify some of the pros and cons:

The Pros of GMOs:

Growing GMO plants is supposed to allow farmers to:

  • Spend less money producing more food.
  • Use fewer pesticides and herbicides.
  • Do less tilling to remove weeds, thereby protecting the soil.

The Cons of GMOs:

The downsides of farming with GMOs include:

  • Creating “super weeds” that have evolved a resistance to glyphosate, a common herbicide in GMO food production.
  • Plants that produce their own insecticide, a bacterial toxin Bacillus thuringiensis (BT), which has led to BT-resistant bugs.
  • A human population that is unwittingly consuming BT, too, since the insecticide is part of GMO plants.
  • Disappointing crop yields and doubt over the environmental benefits of reduced tilling.

Often, GMO advocates claim that, since many plants already have the ability to produce their own pest repellents, GMO plants, which can be engineered to produce their own pesticides, are no different. Wrong! Yes, Mother Nature did give plants an ability to defend themselves from natural enemies, but we’ve been eating these plants for a very long time, so our bodies recognize these substances and are accustomed to dealing with them.

The pesticides from GMO plants are new to humans, and, right now, we don’t know how our bodies will handle them. However, we definitely do know that pesticides (a term that includes herbicides, insecticides, and fungicides) are linked to cancer, neurological diseases, like Parkinson’s, and a number of other very serious health concerns. They have also been shown to cause cancer in children.

Another problem with GMO crops was discovered earlier this year, when an Oregon farmer found GMO wheat growing in fields where he had not planted it. Although that story is still developing, it appears that other GMO plants have also escaped into the nation’s farmland. If this cross-contamination continues, the consequences could affect the entire food supply, making us all unwilling guinea pigs in a massive and very dangerous experiment.

Common Foods Likely To Contain GMOs

When I buy any of these foods I shop for organic versions, or varieties bearing a “Non GMO” label.

  • Cereal
  • Non-organic dairy products
  • Soy in any form (oil, tofu, protein powder, meat substitutes, etc.)
  • Vegetable oil
  • Salad dressings
  • Granola bars
  • Chicken nuggets
  • Papayas
  • Zucchini
  • Yellow squash
  • Anything containing high fructose corn syrup
  • Bread and crackers
  • Rice
  • Potatoes
  • Tomatoes
  • Peas

Are GMO Foods Safe?

To put it bluntly, no one can really answer that question. Monsanto, the corporation that owns patents on many GMO seeds, assures us that these foods are harmless and points to studies – many of which the company has conducted itself – demonstrating that. These studies, however, have been widely criticized for their obvious bias, and I agree with those assessments. The Monsanto studies only prove that data can be manipulated, not that the products are safe. So, without high-quality, objective information, the debate quickly turns into a he said/she said standoff, leaving us with more questions than answers.

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Meanwhile, although these foods are being sold in the U.S., GMO foods are either banned or severely limited throughout much of Europe, including the United Kingdom, Spain, Italy, France, and Germany. And a long list of other countries are following suit, including Japan, China and Brazil. In fact, Monsanto has virtually stopped lobbying for GMO planting in Europe due to low demand by farmers and consumers.

Here is another concern: Monsanto has spent millions of dollars defeating legislation in states like California that would have required foods containing GMOs to be labeled. In addition, a recently passed Farm Assurance law, commonly referred to as the “Monsanto Protection Act”, essentially grandfathers farmers’ rights to utilize existing planting of GMO seeds and plants, even if we learn at a later date that these products have serious health consequences.

The company’s unwillingness to allow labeling and the fact that the Monsanto Protection Act has become law – in spite of a tremendous number of consumers who petitioned the government to veto the bill – certainly does not give me confidence that these foods are safe to consume. In fact, it suggests the company has something to hide. And Monsanto’s apparent “profits before people” attitude shows the reckless disregard the company has for consumers.

Meanwhile, the shocking outcome of a European study with lab animals has created even more questions. Rats in the study that were fed a popular GM corn developed horrifically oversized tumors and organ damage. That study has been widely criticized. But so have studies done by the industry showing that GMOs are safe.

The fact remains that there are no long-term studies demonstrating that GMO foods are healthy – or unhealthy. But given the results of studies I’ve seen, I avoid GMO products whenever possible for myself and my family, and I recommend that you do the same.

What Does the Latest Research Show?

Today, most people carry a heavy burden of toxins, ranging from plastics to heavy metals to compounds found in drugs and – nowadays – food and beverages. One of my major concerns about GMOs is that they could easily increase our toxic load, leading to even more cancer diagnoses.

And now, it turns out that even supposedly “safe” levels of one substance can cause cancer when combined with a “safe” level of another chemical. A new study from Texas Tech found that when low levels of estrogen are combined with small amounts of arsenic, lab animals were nearly twice as likely to develop prostate cancer as animals that were not exposed to estrogen and arsenic.

Unfortunately, we don’t have a choice about exposure to these substances. We are continually exposed to estrogen through the plastic products we use every day, as well as the lining of canned foods. Even small amounts of arsenic are very common in the environment.

New studies on the toxicity of various chemicals used to produce GMO products are not reassuring, either. One recent clinical trial, for example, found that glyphosate, a common herbicide ingredient used to grow GMO plants, caused human breast cancer cells to grow due to its estrogen-like qualities. This is significant because glyphosate was supposedly a safe ingredient with low toxicity.

No wonder so many people are confused and anxious about GMO foods. This is an extremely important issue that raises questions no one can answer with any surety right now.

But, since the answer affects the health of nearly everyone in the nation, here’s the advice I give my patients:

Eat organic produce, grass-fed beef, free-range poultry, and wild-caught fish whenever possible.

Yes, organic food, which has been grown without chemicals or growth hormones, does tend to cost a little more. But you can either pay a few cents more for organic produce, or you can pay a lot more for doctor visits, prescription medication, and hospital stays. Personally, I prefer to pay a bit extra for the peace of mind that comes with knowing my food is GMO free.

The debate over GMOs will likely continue for years. In the meantime, I hope we can develop national labeling standards that will make it easier to determine which foods have been modified and which have not, so at least we can all make informed choices.

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  • eric malouin

    Jeffrey smith and Dr Akiba Green share some very compelling arguments toward GMO foods. In 1989 37 deaths and 1500 permanently disabled caused by genetically modified tryptophan supplements. The manufacturer Showa Danko settled a lawsuit for $2 billion. In 1996 brazil nut genes were spliced with soya beans to add more protein but some consumers went into amphalatic shock due to nut allergies. Fortunately it was removed from the market before any deaths occurred. The late nineties witnessed the splicing of fish genes into tomatoes. In 2003 the University of Nebraska publshed articles in the journal of immunology identifying allergens with genetically modified corn and soy. Farmworkers working with BT pesticide spray experienced some allergic reactions. A decade long study of GM peas was abandoned when it was discovered that it was causing allergic lung damage in mice. The FDA has already improved salmon gene splicing in soy beans in order for the consumer to get omega 3 fatty acids, thus heightening the risk of an allergic reaction within people who have fish allergies. In 1993 the FDA approved Monsantos RBGH (RBST) a genetically altered growth hormone injected into cows to increase milk yield. This growth hormone is a protein hormone which simulates the pitutiary gland in the cow, however its use increases the growth hormone in Humans called IGF1 from 70% to 1000%. IGF1 is a naturally occurring hormone that stimulates growth in puberty but in excess has adverse effects in adult humans causing excessive cell growth that can turn cancerous, in particular the colon, breast and prostate. This was confirmed by Dr Epstein at the University of Chicago who specifically stated that excess IGF1 levels can induce a malignant transformation of human breast epidilea cells. Despite Monsantos claims that most of the hormone gets destroyed after pasteurization, monsantos own scientists were only able to destroy 19% after boiling the milk ( pasteurization) for 30 minutes but normal pasteurization milk is only boiled for only 15 seconds. Monsanto walked away from this business in 2008. Last month the WHO cancer institute announced that Glyphosate, Monsantos pesticide spray that is sprayed on all GM crops was found to be carcingenic. One of the most damming reports on GMO completed in 1998 by Arpad Pusztai and based on a 3 year study on GM potatoes fed to rats. As a result the rats developed large tumors, stunted their growth and compromised their immune systems. Once the report was published Pusztai position as lead scientist for 35 years was dissolved. In summary there are many controversial studies ‘out there’ and the the biggest human safety study is in process right now..did you volunteer ?

  • hi


  • Guest

    gurl aint nobody got time fo dat puhleez

  • IMtheEggman

    Not sure where or why you come to your conclusion’s but..c’est la vie. Why are you questioning my comment re business, we seem to agree. Your comment re ills by iatrogenic means is way off. Did you just learn the word? Being in a family of higher end health industry workers…the kind that require 6-8 years of university, I showed them your comment and they simply shook theirs heads. Your last paragraph is just plain wrong. you are on the anti-vaccine bandwagon. It is misguided. You choose to take that side which is your prerogative. Anyway, I’ve moved on from this old post. You should too.

  • Stefani Hoffman

    You cant wash off the chemicals, most of them are taken into the plant system in order to work. You might also want to research more, sorry to ruin that for you.

  • Kat

    Wow. Of course business is about money. But business is a trade of which I can make choices. If I want a hammer, there are two hardware stores in my town or I can go online and have other options. I can look up reviews to see which has the best features and meets my needs.

    What the grocers, chemical companies, and other agriculture corporations are working hard not just to make money, but to limit the choices of consumers.

    As for the idea that we are alive today because of pharmaceuticals, that is just ignorant. Most of the chronic ills caused today are iatrogenic. Properly prescribed medicines are among the top killers in this country.

    Contemporary folks seem to have a disdain for previous generations, but the fact is, if you were born 100 years ago and lived until your 5th birthday, the chance of living a long, HEALTHY, active life was better than today. It was the infant mortality rate (which has largely been addressed by better hygiene and water, and better living conditions; most childhood illnesses were not fatal and already greatly reduced BEFORE any vaccine was introduced).

  • Letty Colon

    Best comment. You hit it right on the nail!

  • IMtheEggman

    Really? name one business that isn’t about money. And don’t knock pharma. If it wasn’t for this organization most of writing these comments would have died at some point in our lives. Balance your opinion! It’s too easy to jump on the anti-GMO bandwagon.

  • IMtheEggman

    This is about the fifth site so far that I’ve read in the last hour that either claimed non-bias or noted about a half paragraph of “Pro” and multi-paragraphs or an essay to support “Con”. This is not balanced and clearly leans to the anti-GMO team.

  • ForrestByers

    I don’t know what conclusions to reach from reading this article, so I will try to play ” devil’s advocate”. The article states that the “science” that Monsanto used is biased by the supposed fact of its own self interest. Question, where is the ethical purity of “science”? If it is established by the commonality, that facts are facts, which are universally accepted to be true in all cases, which is supposed to be the backbone of all scientific methodology and inquirement, if this postulate is correct, then the Monsanto science in order for it to be science, must abide by the same rules and therefore is not an issue of political debate, unless of course, it can be shown that Monsanto, somehow through its scientific methodology established supposed facts, that are not “facts” at all, but if this is the case, then other scientists should clearly be able to demonstrate it is not science. I have heard no debate or argument based on demonstrable “facts”. Political posturing and bombast, yes there seemed to be plenty of that, speculation, emotional accusation, yes I acknowledge that, but where exactly is the demonstrable review establishing that Monsanto science is not valid by the establishment that the facts are not true? So far, if this is been “peer review”, the result has more to do with politics and fashion, then relevant facts, that make up the “science”.

  • frank the crank

    did not think that my very scientific link would be allowed to be posted.

  • frank the crank

    i actually wish people before they write articles do some in-depth research. I do not like gmo but it needs to be told truthfully not with lies and innuendos.

  • Adria

    So I went grocery shopping for gmo free and gmo additive free foods haha! 2 small grocery bags! It’s in about every thing. Now I will go back to my youth where we made our own food from scratch. No packaged foods, processed foods, junk foods ( I couldn’t even find a gum to chew without dextrose in it). I remember my mom telling me she was thinking while pregnant with me of taking thalidomide to ease her morning sickness but being so health conscious and against drugs decided against it. Years later wow! GMO OMG years later. Amazing what people will do for convenience as I found myself doing. But now I am starting to get sick so time for health care not sick care. Some don’t care, some don’t believe, some don’t know, but choice should be our right so Just Label It! Fluoride in our water? Take it out! Add it to your own water not every ones. We all have the right to know and choose what goes in our bodies and our children’s bodies. All these diseases increasing and new ones stronger ones coming, growing up was practically unheard of.

  • Adria

    i would like to correct my comment “I do know I would rather eat foods resistant to pests than foods heavily sprayed with insecticides to control the pests.” TO ” I do know I would rather eat foods “naturally” resistant to pests” not GMO altered to or sprayed foods as you can wash them off. Or eat the chemical free pest with my food.”

  • Adria

    GMO’s goal from all my research is MONEY. If we were meant to eat, drink and bathe in man made chemicals it would be no issue. However unless we fight back the pharmaceuticals will control our lives. I would rather eat foods sprayed at least you can wash them off. Even better I would rather eat the pest where no chemicals reside.

  • roundthings

    Very good article. Check the cancer rates from 1995, the year before GMOs were first approved (under Clinton by the way) and now. The increase is alarming.
    And anyone who thinks Democrats are any better than republicans on the issues of GMOs and food safety only need to look at both Clinton’s long involvement with Monsanto and Obama has practically put Monsanto in charge of his administration.
    In fact, Obama is the most anti consumer President in history

  • John

    I am not sure what to make of GMO foods. The article talks about potential allergies. I don’t now if it’s related. I used to be highly allergic to ragweed, making me miserable in August and September The last few years I have had little or no problem. Is it because I am eating GMO foods making me more resistant to ragweed? I don’t know, but it appears to me to be a possibility. I do know I would rather eat foods resistant to pests than foods heavily sprayed with insecticides to control the pests.

  • Barbara Sanders

    wow. you sound like a monsanto emloyee.
    i actually thought this was a well thought out, unbiased attempt to look at the facts of a situation with lots of unknowns, many of them deliberate. maybe you could be more specific about what you see as bias? and explain in what way a reasoned approach = scare tactics?

  • Jack


  • Jack


  • bob


  • Robin MacDonald

    Completely biased and full of scare tactics.

  • Anna

    wonderful article, I needed to hear this.


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