Dr Caroline Leaf: All scare and no science?

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On her social media feed today, Dr Leaf posted a meme implying that conventionally farmed food was toxic.

Dr Caroline Leaf is a communication pathologist and self-titled cognitive neuroscientist. Anyone who’s been following Dr Leaf will know from her frequent food selfies that she is an organic convert.

Dr Leaf is welcome to eat whatever she chooses, though not content to simply push her personal belief in organic foods, Dr Leaf is now actively criticising conventional food, publishing memes on her social media posts which imply that conventional produce is poisonous.

As I’ve written before, despite Dr Leaf’s blinding passion and quasi-religious zeal for organic foods, there is no evidence that organic food is any more beneficial than conventional food (Dangour et al, 2009; Bradbury et al, 2014). Indeed, there’s no magic to a healthy food lifestyle. Eat more vegetables. Drink more water. Conventional veggies and conventional water do just fine. Sage advice, even if it doesn’t lend itself to food selfies.

While organic zealots believe they have the high ground on the topic of food safety, the published science cuts through the hype. As noted by Smith-Spangler et al (2012), there is some evidence that there may be less pesticide residue on organically grown foods, but there is no significant difference in the risk of each group exceeding the overcautious Maximum Residue Limit.

Two points on the Maximum Residue Limit that are particularly important:

  1. The Maximum Residue Limit is extremely cautious, and most food tested is well below this already overcautious limit. The Maximum Residue Limit is set to about 1% of the amount of the pesticide that has no effect on test animals.   According to a recent survey of grapes done by Choice Australia, the amount of residue was well below the Maximum Residue Limit (about 1% of the Maximum Residue Limit on average) (Choice Australia, 2014). So on the average bunch of grapes in Australia, the pesticide residue is about one ten thousandth of the level that is safe in animals, and this pattern is the same across all conventional produce. Thinking in more practical terms, “a 68 kg man would have to eat 3,000 heads of lettuce every day of his life to exceed the level of a residue that has been proven to have no effect on laboratory animals … an 18 kg boy would have to eat 534 apples every day of his life to exceed a residue level that is not dangerous to laboratory animals. And an 18 kg girl would have to eat 13,636 kg of carrots every day of her life to exceed such a level.” (ecpa.eu, 2014)

    2. Organic foods have pesticides too. Granted, this is at lower levels than their conventional counterparts, but it’s there all the same (Smith-Spangler et al, 2012). I once had a lively discussion with an organic food zealot about the pesticides in organic farming. Her argument was that organic pesticides are safe because they’re “natural” poisons. So are arsenic, cyanide, belladonna and digitalis (foxglove), but why let the truth get in the way of ones opinion. Poisons are poisons whether they’re “natural” or not. The Maximum Residue Limit applies to organic foods just the same as conventionally farmed produce for that reason.

Another interesting thing … in the Choice survey, the organic grapes had no detectable pesticides, but so did conventionally farmed grapes bought at a local green grocer. So organic food zealots can’t claim that they have a monopoly on low pesticides in their foods.

Not that having lower pesticide residues means that organic foods are necessarily safer. Organically farmed produce has a higher risk of contamination from E. coli and other potentially toxic bacteria, depending on the farming method used (Mukherjee et al, 2007; Sample, 2011).

So to bring it all together, conventional produce has levels of pesticide residues so low that it would take an extra-ordinary feat of vegetarian gluttony to exceed a level that was still found to be non-toxic in animals. The risk to human health from conventional farming with pesticides is nanoscopic. Organic foods may have less pesticide, but they have a higher risk from enterotoxigenic bacteria.

Since there is nothing to fear from conventional foods, it seems irresponsible for Dr Leaf to promote the unscientific idea that conventional foods are poisonous. One wonders why Dr Leaf would engage in a campaign of fear against healthy, nutritious foods? Personal bias perhaps, although that doesn’t bode well for her credibility as an objective scientist. Another plausible reason could be marketing. Fear sells things, that’s Marketing 101. Gardner (2008) wrote, “Fear sells. Fear makes money. The countless companies and consultants in the business of protecting the fearful from whatever they may fear know it only too well. The more fear, the better the sales.”

Posts like today’s make Dr Leaf seem like all scare and no science. Publishing images with the skull and cross bones and the word “POISON” is certainly not attempting to allay anyone’s anxiety, and that fact that it‘s directly tied to a reminder of her upcoming book on food only makes shameless promotion all the more likely. I’m sure that a Godly woman of Dr Leaf’s standing wouldn’t stoop so low as to use fear and mistruth just to make better sales, but posts like today’s open her up to legitimate questions from others regarding her credibility and her motivation.

For her sake, I hope that she tightens up her future posts, and reconsiders her stance on the science of organic and conventional foods.


Bradbury, K.E., et al., Organic food consumption and the incidence of cancer in a large prospective study of women in the United Kingdom. Br J Cancer, 2014. 110(9): 2321-6 doi: 10.1038/bjc.2014.148

Choice Australia, 2014. <http://www.choice.com.au/reviews-and-tests/food-and-health/food-and-drink/groceries/pesticide-residues-in-fruit-and-vegetables.aspx&gt;

Dangour, A. D., Dodhia, S. K., Hayter, A., Allen, E., Lock, K., & Uauy, R. (2009). Nutritional quality of organic foods: a systematic review. Am J Clin Nutr, 90(3), 680-685. doi: 10.3945/ajcn.2009.28041

European Crop Protection Agency, 2014, <http://www.ecpa.eu/faq/what-maximum-residue-level-mrl-and-how-are-they-set>

Gardner, D., The science of fear: Why we fear the things we shouldn’t – and put ourselves in greater danger; 2008, Dutton / The Penguin Group, New York

Mukherjee, A., et al., Association of farm management practices with risk of Escherichia coli contamination in pre-harvest produce grown in Minnesota and Wisconsin. Int J Food Microbiol, 2007. 120(3): 296-302 doi: 10.1016/j.ijfoodmicro.2007.09.007

Sample, I., E coli outbreak: German organic farm officially identified. The Guardian, London, UK, 11 June 2011 <http://www.theguardian.com/world/2011/jun/10/e-coli-bean-sprouts-blamed>

Smith-Spangler, C., Brandeau, M. L., Hunter, G. E., Bavinger, J. C., Pearson, M., Eschbach, P. J., . . . Stave, C. (2012). Are organic foods safer or healthier than conventional alternatives? A systematic review. Ann Intern Med, 157(5), 348-366.

Dr Caroline Leaf, behaviour and genetic destiny

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Today on her Facebook feed, Caroline Leaf posted a quote which said, “Your behavior can and does dictate your genetic destiny”. Dr Caroline Leaf is a communication pathologist and a self-titled cognitive neuroscientist. In isolation, it sounds like she has found confirmation of her view that our thoughts and behaviour control the physical properties of our DNA (Leaf, 2013, p35).

However, I wanted to look at the quote in a broader context, because in the broader context, the quote still doesn’t confirm Dr Leaf’s teaching.

The quote comes from an American doctor, Sharon Moalem. Dr Moalem is obviously a smart man. According to Wikipedia, “Dr. Moalem is an expert in the fields of rare diseases, neurogenetics, and biotechnology. He is the author of the New York Times bestselling book ‘Survival of the Sickest’ and ‘How Sex Works’. Moalem has cofounded two biotechnology companies and is the recipient of 19 patents for his inventions in biotechnology and human health.” (http://en.wikipedia.org/wiki/Sharon_Moalem)

It’s not that Dr Moalem’s quote is wrong. In the book from which the quote is taken, Dr Moalem discusses the expression of genes (Moalem, 2014). There is no doubt that our behaviour affects the expression of genes. For example, when the body encounters a high level of dietary iron (ie: we eat a big juicy steak), a series of steps activates a gene to promote the production of ferritin, a protein that helps to carry iron in the blood stream (Strachan and Read, 2011, p375-6). These changes in genetic expression are mostly protective (for example, ferritin is used to keep toxic elemental iron from damaging our tissues). There are some behaviours that will override the body’s protection, for example, excessive exposure to UV radiation will eventually lead to skin cancer. But overall, the changes in genetic expression that our behaviour causes are protective, and do not adversely affect our health.

Unlike Dr Leaf, Dr Moalem does not promote the notion that our behaviour changes the genes themselves. Neither does he promote that our behaviour, in isolation, is the only modifier of our genetic expression. The quote that Dr Leaf used came from the second chapter of Dr Moalem’s book, “Inheritance: How Our Genes Change Our Lives, and Our Lives Change Our Genes”. Really, the title says it all. Our behaviour influences our genetic destiny, but our genes influence our behaviour just as much, if not more.

For example, small variations in the genes that code for our smell sensors or the processing of smells can change our preferences for certain foods just as much as cultural exposure. Our appreciation for music is often changed subtly between individuals because of changes in the structure of our ears or the nerves that we use to process the sounds. The genetic structure of the melanin pigment in our skin changes our interaction with our environment because of the amount of exposure to the sun we can handle. Our genetic destiny is also largely influenced by our environment, most of which is also beyond our choice (Lobo and Shaw, 2008).

So your behaviour can and does influence your genetic destiny, but your genetic destiny is more influenced by our genes themselves, and the environment that is beyond our control.

Dr Leaf’s quote doesn’t look quite so supportive after all.


Leaf, C.M., (2013) Switch On Your Brain : The Key to Peak Happiness, Thinking, and Health, Baker Books, Grand Rapids, Michigan

Lobo, I. & Shaw, K. (2008) Phenotypic range of gene expression: Environmental influence. Nature Education 1(1):12

Moalem, S., (2014) Inheritance: How our genes change our lives and our lives change our genes, Grand Central Publishing, New York.

Strachan, T. and Read, A., (2011) Human Molecular Genetics. 4th ed. Garland Science, New York.

Dr Caroline Leaf: Avoid foods containing cellulose

This is an anonymised screen shot taken from Dr Leaf’s Facebook feed just now, showing the very sensible reply of a Canadian dietician to Dr Leaf’s ill-informed assertion.  It’s possible that Dr Leaf’s Facebook minders could delete the dietician’s comments or the post altogether, so I wanted to ensure it was saved for the public record.

In fairness to Dr Leaf, I will post her correction if she is willing to make one.

Caroline Leaf Toxic Ingredients 2

Going green – why envy is an adaptive process

The Bible says, in Job 5:2, “For wrath kills a foolish man, And envy slays a simple one.”

A German proverb goes, “Envy eats nothing, but its own heart.”

Dr Caroline Leaf, communication pathologist and self-titled cognitive neuroscientist, posted today on her social media feeds, “Jealousy and envy creates damage in the brain … but … celebrating others protects the brain!”

Yes, sometimes envy isn’t good for us. Emotions guide our thought process, and like all emotions that are out of balance, too much envy can cloud our better rational judgement and bias our perception of the world. Thankfully, envy doesn’t literally eat out our hearts or literally cause brain damage.

If anything, envy when experienced in a balanced way can actually improve our brain functioning. According to real cognitive neuroscientists, envy and regret are emotions that help us because they both fulfil the role of effectively evaluating our past actions, which improves our choices in the future. As Coricelli and Rustichini noted, “envy and regret, as well as their positive counterparts, share the common nature that is hypothesized in the functional role explanation: they are affective responses to the counterfactual evaluation of what we could have gotten had we made a different choice. Envy has, like regret, a functional explanation in adaptive learning.” [1]

When it comes to the human psyche, there is no black or white, good vs evil distinction between different feelings or emotions. B-grade life coaches and slick pseudoscience salespeople dumb down our emotions into a false dichotomy because it helps sell their message (and their books). Every emotion can be either helpful or unhelpful depending on their context in each individual.

As Skinner and Zimmer-Gembeck wrote, “Emotion is integral to all phases of the coping process, from vigilance, detection, and appraisals of threat to action readiness and coordinating responses during stressful encounters. However, adaptive coping does not rely exclusively on positive emotions nor on constant dampening of emotional reactions. In fact, emotions like anger have important adaptive functions, such as readying a person to sweep away an obstacle, as well communicating these intentions to others. Adaptive coping profits from flexible access to a range of genuine emotions as well as the ongoing cooperation of emotions with other components of the action system.” [2]

If you find your thoughts and feelings tinged by the greenish hue of envy, don’t worry, it’s not necessarily a bad thing. Your heart isn’t going to consume itself and you won’t sustain any brain damage. Use envy or regret as tools of learning, tools to help you evaluate your choices so that you make a better choice next time. Having balanced emotions is the key to learning and growing, coping with whatever obstacles life throws at us.


  1. Coricelli, G. and Rustichini, A., Counterfactual thinking and emotions: regret and envy learning. Philos Trans R Soc Lond B Biol Sci, 2010. 365(1538): 241-7 doi: 10.1098/rstb.2009.0159
  2. Skinner, E.A. and Zimmer-Gembeck, M.J., The development of coping. Annu Rev Psychol, 2007. 58: 119-44 doi: 10.1146/annurev.psych.58.110405.085705

Dr Caroline Leaf and the law of great power

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Tonight as I was flicking through Facebook one last time, a post caught my eye. It read,

“The thought you are thinking right now is impacting every single one of the 75-100 trillion cells in your brain and body at quantum speeds”

Dr Leafs social media gem gave me an eerie sense of deja vu. It was only the end of October when she posted the same factoid on social media. Today’s version has been tweaked slightly, although in all fairness, I can’t describe it as an upgrade.

Dr Caroline Leaf is a communication pathologist and self-titled cognitive neuroscientist. On the 23rd of October 2014, she posted this on her social media stream, “Every thought you think impacts every one of the 75-100 trillion cells in your body at quantum speeds!”

On comparing the pair, Dr Leaf has added “brain” into the number of cells under the influence, and then massaged the opening slightly. I already had significant concern about the scientific validity of the previous meme in October. That hasn’t changed. Rather than improving the accuracy of her meme, Dr Leaf’s changes have left it missing the mark.

The fundamental fallacy that thoughts are the main controlling influence on our brain is still there. Thought is simply a conscious projection of one part of the overall function of our brain. Our brains function perfectly well without thought. Thought, on the other hand, doesn’t exist without the brain. Our brain cells influence our thoughts, not the other way around.

The myth of “quantum speeds” is still there. Our neurones interact with each other via electrochemical mechanisms. Like all other macroscopic objects, our brains follow the laws of classical physics. It’s not that quantum physics doesn’t apply to our brains, because quantum mechanics applies to all particles, but if you think you can explain macroscopic behaviour using quantum physics, then you should also try and explain Schrodingers Cat (see also chapter 13 of my book [1] for a longer discussion on quantum physics). Dr Leaf is particularly brave to make such bold statements about quantum physics when even quantum physicists find it mysterious.

What made me slightly embarrassed for Dr Leaf is the new part of her statement. In my blog on Dr Leaf’s previous attempt at this meme, I pointed out that Dr Leaf’s estimate of the number of cells in our body was more than three times that of the estimate of scientists at the Smithsonian (http://www.smithsonianmag.com/smart-news/there-are-372-trillion-cells-in-your-body-4941473/?no-ist). The fact that Dr Leaf so badly estimated, when all she needed to do was a one line Google search, suggested that she just made the number up. Failing to cite her source eroded at her credibility as a scientist.

Today, Dr Leaf still claims that there are 75-100 trillion cells in the brain and the body. The Smithsonian still hasn’t changed its estimate. Dr Leaf still hasn’t cited her source, and has ignored a world-renowned scientific institution. Perhaps Dr Leaf believes she knows more than the scientists at the Smithsonian? Perhaps she has a better reference? We’ll never know unless she cites it.

Taken as a whole, her meme is no closer to the truth than it was six weeks ago. Some may ask if it really matters. “Who cares if we have 37.2 trillion cells or 100 trillion cells or even 100 billion trillion”. “So what if our thoughts influence us or not.” If this was just a matter of a pedantic argument between some scientists over a coffee one morning,then I’d agree, it wouldn’t be so important. But Dr Leaf claims to be an expert, and more than 100,000 people read her memes on Facebook and many more on Twitter, Instagram, and the various other forms of social media she is connected to. Nearly every one of those people take Dr Leaf at her word. Ultimately the issue is trust.

If Dr Leaf can misreport such a simple, easily sourced fact, and not just once but twice now, then what does that mean for her other factoids and memes that she regularly posts on social media? If Dr Leaf incorrectly says that every thought we think impacts every cell in our body, then hundreds of thousands of people are wasting their mental and physical energy on trying to control their thoughts when it makes no real difference, and if anything might make their mental health worse [2, 3].

This is more than just a pedantic discussion over a trivial fact.  These memes matter to people, and can potentially influence the health and wellbeing of many thousands of lives.

Peter Parker, quoting Voltaire, said, “With great power comes great responsibility.”  Just because Spiderman said it doesn’t diminish the profundity of that statement.  This law of great power applies to Dr Leaf as much as it does to Spiderman.  I hope and pray that she gives this law of great power the consideration it deserves.


  1. Pitt, C.E., Hold That Thought: Reappraising the work of Dr Caroline Leaf, 2014 Pitt Medical Trust, Brisbane, Australia, URL http://www.smashwords.com/books/view/466848
  2. Garland, E.L., et al., Thought suppression, impaired regulation of urges, and Addiction-Stroop predict affect-modulated cue-reactivity among alcohol dependent adults. Biol Psychol, 2012. 89(1): 87-93 doi: 10.1016/j.biopsycho.2011.09.010
  3. Kavanagh, D.J., et al., Tests of the elaborated intrusion theory of craving and desire: Features of alcohol craving during treatment for an alcohol disorder. Br J Clin Psychol, 2009. 48(Pt 3): 241-54 doi: 10.1348/014466508X387071

Dr Caroline Leaf and the cart before the horse, take two

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In between her sightseeing in the UK and ballet concerts in the Ukraine, Dr Leaf, communication pathologist and self-titled cognitive neuroscientist, took the time to post some more memorable memes.

Today, Dr Leaf posted, “A chaotic mind filled with thoughts of anxiety, worry, etc. sends out the wrong signal right down to the level of our DNA.”

Hmmm, that one looked familiar … actually, Dr Leaf posted the exact same phrase on the 5th of October this year.  I’m all for recycling, but of renewable resources, not tired ideas.

This meme has been soundly rebuffed before, and the idea that the mind controls our DNA has been thoroughly dismantled.  Reposting it won’t make it any truer.

This meme is better off being put into the trash than the recycling bin.

(For more information on the rebuttal of the mind over matter meme, see also “Hold that thought: Reappraising the work of Dr Caroline Leaf“, “Dr Caroline Leaf: Putting thought in the right place” Part 1 and Part 2, “Dr Caroline Leaf and the matter of mind over genes“, “Dr Caroline Leaf, Dualism, and the Triune Being Hypothesis”, “Dr Caroline Leaf and the Myth of the Blameless Brain” and “Dr Caroline Leaf and the Myth of Mind Domination” just to name a few references).

Dr Caroline Leaf and the organic foods fallacy

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Organic foods. They are amazingly popular. More than a million Australians buy organic foods regularly, and several million more buy it occasionally. The retail value of the organic market is estimated to be more than $1 billion annually. The assumption made by most people is that because it’s so popular, organic foods must be good for you, or at least have something going for them to make them worth all the hype.

Of course, just because something’s immensely popular and has a billion-dollar turnover doesn’t necessarily mean it’s beneficial (One Direction is a case-in-point).

In fact, despite organic foods being touted by their supporters as healthier, safer, and better for the environment than normal foods, actual scientific evidence fails to show any significant difference. I wrote about this earlier in the year (see: Borderline Narcissism and Organic Food). Since then, another large prospective trial deflated organic food’s bubble, with a British study showing no change in the incidence of cancer in women who always ate organic foods versus those who never ate organic foods [1].

The dearth of benefit from organic foods wouldn’t be so bad if they were just another guy in the line-up, something neutral and inert. Unfortunately, not only can organic produce be contaminated if farmed incorrectly [2, 3], but they come at an extraordinary premium, sometimes costing four times more than their conventional counterparts (Borderline Narcissism and Organic Food).

Dr Caroline Leaf is a communication pathologist and a self-titled cognitive neuroscientist. A couple of months ago, she let slip her intention to publish a book in 2015 about food. Who knows what she’ll actually say, but if today’s social media meme is anything to go by, it will likely follow the same pattern of her other teachings.

Today, she wrote, “Research shows that dark organic CHOCOLATE lowers blood pressure, improves circulation, increase HDL (“good”) cholesterol, reduce the risk of heart attack and stroke, and increases insulin … and … recent research has even suggest it may prevent weight gain!”

As I discussed recently, Dr Leaf does herself a disservice by not citing her sources. It’s very brave to write in a public forum that dark chocolate reduces the heart attack and stroke, since this could be interpreted as medical advice, which she is not qualified to give. As for the actual effects of dark chocolate, there is not a lot of quality evidence on dark chocolate on its own. A 2011 meta-analysis of general chocolate consumption on cardiovascular risk did indeed show a relative risk reduction of 37% [4]. But before you prescribe yourself two dark chocolate Lindt balls twice a day, consider that a relative risk reduction of 37% isn’t a big effect. Plus, the recommended 50 grams of 85% organic dark chocolate to attain the small benefit for your cardiovascular health contains just over 300 calories/1280 kJ (the average can of Coke contains 146 calories/ 600 kJ), and is 30% saturated fat (http://caloriecount.about.com/calories-green-blacks-organic-dark-chocolate-i110689). So any health benefit that may be associated with the poly-phenol content is likely nullified by the high saturated fat and calorie count.

What concerns me about Dr Leaf’s future foray into dietetics is that little word sitting quietly in her opening sentence: “organic”. Dr Leaf is an organic convert. But rather than act like a scientist that she claims to be, she preaches from her biases, ignoring the evidence that organic food is all hype and no substance, encouraging Christians everywhere to pay excessive amounts of money for something that’s of absolutely no benefit. Dr Leaf is welcome to eat whatever she chooses, but encouraging organic eating without clear benefit is more hindrance than help for most of her followers.


  1. Bradbury, K.E., et al., Organic food consumption and the incidence of cancer in a large prospective study of women in the United Kingdom. Br J Cancer, 2014. 110(9): 2321-6 doi: 10.1038/bjc.2014.148
  2. Mukherjee, A., et al., Association of farm management practices with risk of Escherichia coli contamination in pre-harvest produce grown in Minnesota and Wisconsin. Int J Food Microbiol, 2007. 120(3): 296-302 doi: 10.1016/j.ijfoodmicro.2007.09.007
  3. Sample, I., E coli outbreak: German organic farm officially identified. The Guardian, London, UK, 11 June 2011 http://www.theguardian.com/world/2011/jun/10/e-coli-bean-sprouts-blamed
  4. Buitrago-Lopez, A., et al., Chocolate consumption and cardiometabolic disorders: systematic review and meta-analysis. BMJ, 2011. 343: d4488 doi: 10.1136/bmj.d4488