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Organic vs Conventional foods: Part 3 – Safer for you?

Posted on December 30th, 2012 by Stephen Hardy | Print

In the first part of this blog (3) we looked at the argument over the Stanford study (1) on whether organic foods are healthier or safer for you than their conventional alternatives. Four key claims were made:

  1. Organically produced foods are no more nutritious for you than those produced using conventional agricultural methods.
  2. Organically grown produce does have higher levels of certain nutrients than conventionally grown foods.
  3. Organic produce has less pesticide contamination than conventionally grown crops.
  4. Organic foods contain less antibiotic-resistant bacteria than do conventionally grown foods.

In the second part of this blog (6), we looked at the first of these categories: ‘Healthier for you’ – points 1. and 2. on this list – and discovered how difficult a question it was to answer. In this, the final part of this blog, we will look at the last claim made for the Stanford study: Organic food is safer for you. These are points 3. and 4. on the above list.

While it is very difficult to say organic food is healthier for you, we are on much firmer ground when asking whether it is safer for you. Here the evidence is much clearer and the interpretation much easier and cleaner.

Before going into the discussion however I need to give you a glimpse into a day in the life of a scientist.

As I have said before, we scientists are a curious and inquisitive lot who are always asking questions. We can’t help ourselves. It’s in our nature. But to get meaningful answers to the questions we ask, we have to ask the right questions and ask them in a particular way. Scientists do this by doing experiments and making observations. To get meaningful answers to their questions scientists carefully control all the conditions of an experiment, to remove all the potential variables. Under these controlled experimental conditions the scientist can then make a single change and measure the effect of that change. For example: I may be interested in finding out whether a particular chemical has an effect on the growth rate of bacteria. To find out I set up two identical test tubes of growth medium. In one tube I put the bacteria. In the other tube I put the same amount of bacteria and the chemical I want to test. I then put both tubes in a warm place and give the bacteria in the tubes time to grow. At the end of that time I measure how many bacteria have grown in each tube. If the chemical has had an effect on the growth rate of the bacteria, there will be a different number of bacteria in the two tubes. And because I have controlled the conditions of the experiment, I can conclude the chemical was responsible for the difference in the growth of the bacteria because it was the only thing that was different between the tubes. So by creating simple environments or systems they can understand and control, scientists can see what the effects are of making changes to that environment. This is why it is so difficult to answer the simple question of whether organic food is healthier for you. The conditions are just too complex and too variable to say with certainty any differences you do find are solely due to the food being grown organically or not. It could be due to other factors you hadn’t thought about or be influenced by factors you hadn’t taken into consideration or can’t allow for, or change with time.

So with this background in place, let’s look again at the last two points in the above list on the claims made for the Stanford study:

  1. Organic produce has less pesticide contamination than conventionally grown crops.
  2. Organic foods contain less antibiotic-resistant bacteria than do conventionally grown foods.

As organic farming does not use pesticides, it is hardly surprising foods produced organically contain less pesticide residues. So why don’t organic farms use pesticides? Before we can answer that question we need to know what a pesticide is and what it does.

The term “cide” added to the end of a word means a killer or a killing. So for example, ‘suicide’ is to kill yourself; ‘homicide’ is to murder someone else and ‘genocide’ is to murder a large number of people. A ‘pesticide’ is therefore something to kill an unwanted pest. A fungicide kills an unwanted fungus; an insecticide kills an unwanted insect; a herbicide kills an unwanted plant or weed and so on. Conventional agriculture is absolutely dependent on the widespread use of pesticides. It uses an awful lot of them. 2.3 billion kg (5.1 billion pounds) per year in the US alone as part of a global market of over $40 billion annually (12). Given how much pesticide we use it is hardly surprising our food, our bodies and our environment are contaminated with them (13).

Now we’ve covered what a pesticide is and how much we use them, we need to know why we use them and what the implications of using them are.

Pesticides are poisons used to kill an unwanted pest and in conventional agriculture they are used to stop something else eating or spoiling the food the farmer is trying to grow for you. If a pesticide is designed to kill something that wants to eat your food, why aren’t you affected when you eat the same food? There are two reasons:

  • Foods sprayed with a pesticide cannot be sold for human consumption until a certain number of days or weeks have passed after spraying. This is to ensure the amount of pesticide still in the food is below a level considered “safe” for you to eat. This delay between spraying and eating is called a “withholding period”.
  • The pesticide exploits something special about the biochemistry of the pest species: Some weakness or biological pathway present in the pest species that isn’t in you. So the pesticide poisons the pest and not you.

In theory, this is all well and good. But theory isn’t reality. There are a whole host of potential and practical problems in using and relying on pesticides. For example: The biochemical pathway or weakness you are exploiting in the pest may also be present in other species, species you don’t want harmed. So an insecticide to kill a particular caterpillar might also kill beneficial insects like the predatory ladybirds, or the honey bees and butterflies, responsible for pollinating our crops. Using a pesticide may therefore cause considerable collateral damage to the environment.  In many instances there is compelling evidence it does.

There is also the problem of whether the pesticide is “safe” or not. Because living systems are so complex and variable, it is impossible to come up with a pesticide that will kill 100 % of the pest species 100 % of the time at a dose that doesn’t have at least some harmful effect in species you do not want to be harmed, including you and me. So when you ask the question of whether or not a pesticide is “safe” the answer you almost invariably get is not “Yes” or “No” but “Depends”! And for many of the pesticides we rely on, we haven’t even asked the question! There are over 85,000 synthetic chemicals currently registered in the USA alone, with over 2,000 added each year. Of these chemicals only 7 % have complete toxicological information, while for over 40 % of them, we have no data at all! (7 and 8).

Synthetic chemicals are chemicals we invented, chemicals that do not exist in nature. We need to keep a healthy scepticism for chemicals nature does not use, because there may be a very good reason why.

There are a great many scientific studies, performed under rigidly controlled experimental conditions, showing synthetic pesticides previously thought “safe” do have profound health effects. Health effects you need to be concerned about. Health effects that may affect you and your family. We have repeatedly discussed a number of these studies and what “safe” means in previous Promoting Good Health blogs. Interested readers who want to explore the matter further are also directed towards Prof. Alf Poulos’s 2005 reference work “The Silent Threat”, available on this website or Amazon and the Apple iTunes Store

Organic agriculture doesn’t use pesticides. Organic farmers believe spraying poisonous chemicals on the food we eat is not good for us nor is it good for the environment. It’s a hard attitude to argue with. Supporters of conventional agriculture counter by saying it’s only a philosophical and not a practical objection however and the dangers have either been overstated and the cost-savings of using pesticides outweigh the risks. We have discussed this here and in many previous blogs. The Stanford study is just one of many showing organically produced foods contain less pesticide residues than foods grown conventionally. We also know that some of these pesticide residues may be harmful. By eating organic produce you are therefore not putting yourself and your family in harms way.

And now we come to the last point on the list:

  1. Organic foods contain less antibiotic-resistant bacteria than do conventionally grown foods.

There is a great deal I could write on this topic. Indeed, I already have. There is a three part blog on the use of antibiotics in agriculture and why it isn’t a good idea on the www.drstephenhardy.com website at the following link (11). The conclusion now is no different to when the blogs were written: Using antibiotics to produce your food is not a good idea and eating foods contaminated with antibiotic resistant microorganisms may be putting you and your family at risk.

Which brings us to the end of our story: What does the Stanford study really tell us? What are the take-home messages?

Firstly, we cannot say organic food is more nutritious or healthier for you because of what it contains. There are just too many factors involved to get a sensible answer to this question. We can however say organic food may be safer for you because of what it doesn’t contain. It does not contain traces of pesticides known to be harmful. How harmful, to whom and over what time period have been discussed before in previous blogs and in “The Silent Threat” (9) and will doubtless be the subject of many future blogs. But that some of the pesticides used in conventional agriculture are potentially harmful to you and your family is beyond dispute. And the only way to avoid those risks is to avoid exposure to these chemicals. Eating organically produced foods does that (10).

It’s the same for the presence of antibiotic resistant bacteria on conventionally grown produce. We know using antibiotics to produce your food is not a good idea. And we know why. And we’ve known for some time. Yet we still do it. Here again, eating organically produced foods reduces your risk.

And finally, in this series of blogs we have deliberately avoided discussing the relative environmental costs of organic and conventional agricultural methods and how the conventional agricultural methods in widespread use are ecologically unsustainable. It’s not because the question isn’t important. It’s very important. The reason it wasn’t discussed here is because it was not covered by the Stanford study, a point made quite clearly by the authors. That discussion we will leave for another time.

Until next time, stay happy and healthy.


(1) Smith-Spangler, C.; Brandeau, M. L.; Hunter, G. E.; Bavinger, J. C.; Pearson, M.; Eschbach, P. J.; Sundaram, V.; Liu, H.; Schirmer, P.; Stave, C.; Olkin, I. and Bravata, D. M.: Are organic foods safer or healthier than conventional alternatives?: A systematic review. Ann. Intern. Med., 157 (5), 348-366, 2012.
Abstract available online at: http://www.ncbi.nlm.nih.gov/pubmed/22944875
(2) Poulos A. and Hardy S.: Organic Food: A Guide for Consumers, Promoting Good Health, 2011
(3) Organic vs Conventional foods: Part 1 – Which is better?
(4) A measured difference between sample groups is said to be “statistically significant” if it passes a mathematical test for whether the observed difference is due to chance or not. A difference is usually said to be statistically significant when there is less than a 5% possibility the observed difference is due to chance.
(5) Brandt, K.; Leifert, C.; Sanderson, R.: and Seal, C. J.: Agroecosystem Management and Nutritional Quality of Plant Foods: The Case of Organic Fruits and Vegetables, Critical Reviews in Plant Sciences, 30 (1-2), 177-197, 2011
(6) Organic vs Conventional foods: Part 2 – Healthier for you?
(7) Bennett, M.; Davis, B. J.: The identification of mammary carcinogens in rodent bioassays; Environ. Mol. Mutagenesis, 39: 150-157, 2002.
(8) Preventable cancer in the USA. The Lancet, 375 (May 15): 1665, 2010.
(9) Poulos, A.: “The Silent Threat”. Promoting Good Health, 2005.
Available online at: https://www.promotinggoodhealth.com/shop/the-silent-threat
Available through Amazon at: http://www.amazon.com/The-Silent-Threat-Chemicals-ebook/dp/B0098ZRITO
(10) EWG’s 2012 Shopper’s Guide to Pesticide in Produce™ http://www.ewg.org/foodnews/summary/
(11) Hardy, S. J.: Antibiotics: Far too much of a good thing. CleanFood organic, No. 4, 166-175, 2007.
Hardy, S. J.: ‘Keeping the “Magic” in the “Magic Bullet” – Parts I to III’ Available online at: http://www.drstephenhardy.com/category/blog
(12) EPA: Pesticide Industry Sales and Usage 2006-2007 Market Estimates.
Available online at: http://www.epa.gov/opp00001/pestsales/07pestsales/market_estimates2007.pdf
(13) A Present for Life: Hazardous chemicals in umbilical cord blood. Greenpeace and World Wildlife Fund (WWF), 2005.
Available online at: http://www.greenpeace.org/eu-unit/en/Publications/2009-and-earlier/a-present-for-life