Can you really Think and Eat Yourself Smart?


Today I’m in Sydney, a vibrant, bustling city which centres on one of the most beautiful harbours in the world.  When I booked my flights in April, I was originally going to spend the day attending Dr Caroline Leaf’s Australian Think and Eat Yourself Smart workshop.  Dr Leaf and her minions revoked my ticket a few weeks later.  She also changed the workshop twitter hashtag from #thinkandeatsmart to just #eatsmart, so perhaps Dr Leaf doesn’t want free thinking at the workshop.

It’s such a shame really, because I was looking forward to being part of the history of Dr Leaf’s first workshop on Australian soil.  But no matter … why waste a perfectly good plane ticket when I can have a day to sightsee, take photos, and catch a few Pokemon here and there as well.

And as a special something for all the people who’re attending the workshop today with Dr Leaf, I thought I’d pen a blog in their honour … something for them to ponder as they listen to Dr Leaf’s presentation, and maybe even provide them with a nidus of a question to pose to her during the day.  So here goes …

As the name would suggest, the Think and Eat Yourself Smart workshop is based on Dr Leaf’s book, Think and Eat Yourself Smart.  Does the book (and the subsequent workshop) deliver what it promises?  That is, can you really think and eat yourself smart?  It’s all well and good for Dr Leaf to espouse her fringe opinions on the food industry and modern farming, and to recycle nutritional information that doctors and dieticians have been promoting for years, but if her book can’t deliver on its titular promise, then it’s just an unoriginal rehash.

To support her thesis that we can think and eat ourselves smart, Dr Leaf declares that what you think affects what you eat, and what you eat affects what you think.  It’s on these intertwined ideas that Dr Leaf’s book stands or falls.  Let’s look at those statements in more detail.

Statement number 1 – “What you think affects what you eat”

Dr Leaf has a broad approach with this premise.  She suggests that the mindset that you have will not only determine what you consume, but also how your body will process it.

For example, she said on page 84 of Think and Eat Yourself Smart, “Research shows that 75 – 98 percent of current mental, physical, emotional and behavioural illnesses and issues come from our thought life; only 2 – 25 percent come from a combination of genetics and what enters our bodies through food, medications, pollution, chemicals, and so on.  These statistics show that the mindset behind the meal – the thinking behind the meal – plays a dominant role in the process of human food related health issues, approximately 80 percent.  Hence the title of this book: you have to think and eat yourself smart, happy and healthy.”

She goes on to say, “If we do not have a healthy mind, then nothing else in our life will be healthy, including our eating habits.”

We can break down these statements to assess their validity.

First of all, this statement is predicated on her 98 percent myth, something which I’ve previously proven to be implausible, but which Dr Leaf continues to use despite the overwhelming evidence against it.  To arrive at this conclusion, Dr Leaf has over-extrapolated, paraphrased, and exaggerated a handful of sources that were either out-of-date, clearly biased, or irrelevant.  She even had the gall to ascribe a made-up figure to an article which, ironically, twice contradicted her.  If you want to know more, see Chapter 10 in my book (

This means that Dr Leaf’s statement, and indeed, her entire book, is built on gross misrepresentations of illegitimate resources.  Genetics and our external environment actually play a much greater role than she is willing to give credit for.  The mindset behind the meal is largely irrelevant – nowhere near 80 percent as Dr Leaf suggests.

But for the sake of argument, let’s take a couple of well-known medical conditions that are often associated with lifestyle and compare the research examining the difference that thinking and food make to them.  After all, if your mindset really is responsible for more than 80 percent of our health, then these two very common conditions should improve by more than 80 percent when thought patterns are changed.

Example 1: Hypertension.

Hypertension is also known as high blood pressure.  First, a brief explanation of what the numbers mean when talking about blood pressure so we’re on the same page: Blood pressure is measured in units of millimetres of mercury (or mmHg).  The old sphygmomanometers were hand pumps attached to a rubber bladder and a column of liquid metal mercury.  The blood pressure reading was however high the column of mercury rose at the two ends of the cardiac cycle.  There are always two numbers, expressed as ‘number 1 over number 2’ and written as N1/N2, like 120/80 or ‘one hundred and twenty over eighty’.  The top number is the maximum pressure in the arterial system when the heart pumps the blood into the arteries.  The bottom number is the pressure left over in the arterial system just before the heart beats again.  A blood pressure of 120/80 is the gold-standard physiological reference of normal blood pressure.  A blood pressure consistently above 140/90 is considered high.

Primary hypertension, which accounts for about 95 percent of all cases, has a strong genetic component.  According to eMedicine, “Epidemiological studies using twin data and data from Framingham Heart Study families reveal that BP has a substantial heritable component, ranging from 33-57%.” (  Environmental causes account for nearly all of the rest.  Secondary hypertension is related to a number of different diseases of the arteries, kidneys, hormone system and many others.  Diet is clearly part of those environmental causes.  Psychological stress is in there too, but the question is, how important is it?  If Dr Leaf is right, it should be 80 percent.

According to medical research, reducing alcohol intake to one standard drink per day or less reduces the systolic blood pressure (the top number) by between 2 and 4 mmHg.  Reducing salt to less than 6g a day decreases the systolic blood pressure by between 2 and 8 mmHg.   At best, that’s a 12mmHg reduction.  The DASH diet is as close to Dr Leaf’s macrobiotic tree-hugging anti-MAD diet as one could reasonably get, relying not just on cutting out salt, but also consuming low fat milk and lots of fruit and vegetables.  At best, the DASH diet could shave another 6mmHg from the standard low salt diet.  So that’s a grand total of 18mmHg with even the most optimistic of expectations.

Compared to diet, the best improvement in blood pressure from mind control is 5mmHg at best (and given the size and quality of the studies, that’s being generous) (Anderson et al, 2008; Barnes et al, 2008).

So for hypertension, changing your thinking has, at best, only about a quarter as powerful as changing your diet, not four times more powerful as Dr Leaf would have us believe.  One more nail in in the coffin for Dr Leaf’s theories.

Example 2: Dyslipidaemia.

Dyslipidaemia is medical jargon for cholesterol behaving badly.  Cholesterol is a waxy substance that’s found as a component of the fats in our diet.  To simplify a complex process, we need cholesterol to make our cell membranes, and cholesterol is also an essential building block for most of our hormones.  Cholesterol is usually carried around the body on protein transports called lipoproteins.  If there’s over-production of these lipoprotein particles or they’re not cleared by the liver properly, then the cholesterol they carry can get up to mischief.  The pathways and means of lipid metabolism in the human body reflect complex processes, and genetics, certain medical conditions, medications, and environmental factors can change how the lipoproteins behave.

So how much does thinking affect our cholesterol?  Well, there isn’t a lot of research looking at the subject, but a few studies have looked at cholesterol (specifically triglycerides, one of the lipids in the cholesterol ‘team’) and ‘mind-body practices’ (such as self-prayer, meditation, yoga, breathing exercises, or any other form of mind-body related relaxation technique or practice).  In a cross-sectional analysis of a cohort from the Rotterdam Study, Younge and colleagues examined the association between mind-body practices and the blood levels of triglyceride.  They found that mind-body practices were associated with a triglyceride level 0.00034 mmol/L less than those who did not perform mind-body practices (Younge et al, 2015).  That’s nearly imperceptible, possibly an artefact.  In fact, the average effect of placebos (the fake pills given as a control in therapeutic drug trials) are far greater – 0.1 mmol/L on average (Edwards and Moore, 2003).  Dietary interventions such as low carbohydrate diets decreased triglycerides by 0.26 mmol/L compared to low fat diets (Mansoor et al, 2016), and low fat diets up to 0.27 mmol/L lower than standard diets (Hooper, 2012).  Statins, the lipid-lowering medications, reduce triglycerides by between 0.2-0.4 mmol/L depending on the specific drug studied (Edwards and Moore, 2003).

The point of all this isn’t so much the specific numbers but the obvious difference between the (lack of) power of thought over an important lifestyle condition compared to the effectiveness of diet and medications.  If thinking was four times more important to the process of human food related health issues as Dr Leafs proposes, then thought-related ‘mind-body’ interventions should be at least four times more effective than any other intervention.  But the numbers don’t reflect that – ’Mind-body’ interventions are 1000 times weaker than dietary or drug interventions.

So Dr Leaf’s pronouncement that “the mindset behind the meal – the thinking behind the meal – plays a dominant role in the process of human food related health issues, approximately 80 percent” is complete bunkum.  There is no evidence to support the 98 percent myth which forms her statements underlying premise, and the examples of hypertension and dyslipidaemia, two common lifestyle conditions with proven genetic and dietary links, prove that thought based interventions are much, much weaker than dietary or drug interventions.

Therefore Dr Leaf’s claim that what you think affects what you eat is entirely baseless.

Statement number 2 – “What you eat affects what you think”

Dr Leaf writes, “Although your brain is only 2 percent of the weight of your body, it consumes 20 percent of the total energy (oxygen) and 65 percent of the glucose – what you eat will directly affect the brain’s ability to function on a significant scale.  Your brain has ‘first dibs’ on everything you eat.  I call this the ’20 percent factor’ or the eating behind the thinking, and it underscores the fact that how and what we eat affects our mind, brain and body.” (p84-5)

On face value, the statement seems to hold some weight.  Food does have an impact on how our brain works.  It certainly isn’t the only factor though – demands in the environment, our oxygen levels, our hormones, the function of our major organs, infections or injury, and our levels of sleep, all play a significant role on how our brain functions too.  But strictly speaking, what we eat does have an impact on how we think – if we haven’t eaten, or if we don’t consume enough calories, especially carbohydrates, our body slows some of our bodily functions down to preserve energy, including some of our cerebral functions.  So when you hear people complain that they can’t think because they have low blood sugar, that may in fact be true.  On the other hand, a pure glucose load can shift the balance of the amino acid tryptophan in our body, which enables the brain to produce more of the neurotransmitter serotonin, which can lift our mood.  Or ingesting food or drinks with stimulants like caffeine, such as my morning espresso, also improves how we think by making us more alert.

Unfortunately, Dr Leaf’s application of this premise goes several steps too far.  Later on page 85, Dr Leaf says, “if you eat while emotional, your body does not digest your food correctly.”

Well, that statement may contain an element of truth but only because it’s so hazy and indefinite that it’s applicable in the broadest sense.  Technically, we’re always emotional to one degree or another.  Even if I assume that Dr Leaf’s is meaning ‘angry’ when she says ‘emotional’ then it’s not so much that our body digests food incorrectly, but just differently.   When you’re highly aroused (physiologically, not sexually, just to clarify), your body goes into fight or flight mode.  The body diverts blood away from your intestines and towards your muscles, heart and lungs, so that you have the energy to handle the crisis.  The food in your stomach and guts isn’t going anywhere, and your body leaves it where it is to come back to it later when the crisis has been averted.  This is a normal physiological response.  The body still digests the food and absorbs it correctly, things are just delayed a little (Kiecolt-Glaser, 2010).

The biggest problem with Dr Leaf’s ‘eating behind the thinking’ argument is that it directly undermines her previous teaching.

Dr Leaf has made multiple social media posts claiming that the mind is separate from the brain and controls the brain.  She’s written much the same sentiment in her books.  Take a meme she posted to social media in May 2016.  It said, “As triune beings made in God’s image, we are spirit, mind (soul) and body – and our brain being part of the body does the bidding of the mind …”, and “God has designed the mind as separate from the brain. The brain simply stores the information from the mind and your mind controls your brain.”

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So the obvious question is, “If God designed our mind (our thinking) to be separate from the brain and to control the brain, then how can the food we eat make any difference to what we think? My diet affects my brain through the amount and timing of glucose I ingest, but can my diet can’t affect my thinking if the mind is separate to the brain and controls the brain?

Either the mind is separate to the brain, or it’s not.  It can’t be both.  If the mind is separate to the brain, then what you eat can’t affect what you think and the book becomes an emaciated shadow of rhetoric.  If the mind is dependent on the brain then the book and seminar maintain some semblance of validity, but the rest of Dr Leaf’s ministry crumbles like a well-made cheesecake crust, since the entirety of Dr Leaf’s ministry rests on her idea that the mind is separate from the brain and controls the brain, not the other way around (

At the very least, this must be embarrassing for Dr Leaf, and if she keeps shooting herself in the foot, people will eventually notice that she’s limping.

So other than the free-range, fair-trade, grass fed, organic agro-ecologically produced kale and spinach root muffins and the chia and dandelion broth, it appears that the attendees at Dr Leaf’s workshop today may not be getting what they signed up for.  What you think does not radically change your health, or influence what your food does to your body, and the food you eat does not significantly change how you think.  Our diet is important to our health, but we can’t think and eat ourselves smart.

To all the attendees at the workshop, I hope you got something valuable out of the workshop.  While you were all sitting in a small room, listening to Dr Leaf and snacking on lemon and quinoa stuffed free-range quail giblets, Sydney was outdoing itself.  Not that I’m rubbing it in or anything, but see for yourself …

Kirribilli View

Dr Mary Booth lookout

Milsons Point

Milsons Point


Milsons Park, Neutral Bay

Cremorne20160820 Web


Point Piper

Point Piper

Macquarie Lighthouse

Macquarie Lighthouse

Blues Point Reserve

Blues Point Reserve

Blues Point Reserve

Blues Point Reserve


Anderson JW, Liu C, Kryscio RJ. Blood pressure response to transcendental meditation: a meta-analysis. Am J Hypertens 2008 Mar;21(3):310-6

Barnes VA, Pendergrast RA, Harshfield GA, Treiber FA. Impact of breathing awareness meditation on ambulatory blood pressure and sodium handling in prehypertensive African American adolescents. Ethn Dis 2008 Winter;18(1):1-5

Edwards JE, Moore RA. Statins in hypercholesterolaemia: a dose-specific meta-analysis of lipid changes in randomised, double blind trials. BMC Family practice. 2003 Dec 1;4(1):1.

Hooper L, Abdelhamid A, Moore HJ, Douthwaite W, Skeaff CM, Summerbell CD. Effect of reducing total fat intake on body weight: systematic review and meta-analysis of randomised controlled trials and cohort studies. Bmj. 2012 Dec 6;345:e7666.

Kiecolt-Glaser JK. Stress, food, and inflammation: psychoneuroimmunology and nutrition at the cutting edge. Psychosomatic Medicine. 2010 May;72(4):365.

Mansoor N, Vinknes KJ, Veierød MB, Retterstøl K. Effects of low-carbohydrate diets v. low-fat diets on body weight and cardiovascular risk factors: a meta-analysis of randomised controlled trials. British Journal of Nutrition. 2016 Feb 14;115(03):466-79.

Younge JO, Leening MJ, Tiemeier H, Franco OH, Kiefte-de Jong J, Hofman A, Roos-Hesselink JW, Hunink MM. Association between mind-body practice and cardiometabolic risk factors: The Rotterdam Study. Psychosomatic medicine. 2015 Sep 1;77(7):775-83.

Olive Leaf Extract – A potential treatment, but not for what you think

Here in Australia, it’s winter. It’s currently warmer in the fridge than it is outside. We’ve just been blasted by a wall of frigid air straight from Antarctica, and much of the south-eastern corner of our continent has snow drifts over parts that not so long ago were baking under the hot Autumn sun. It’s not something we’re used to in Australia.

Of course, now that winter is firmly entrenched, more people are coming to see me with their viral upper respiratory tract infections, better known as ‘colds’. Yes, ’tis the season to be sneezin’!  Over my years of practice, I’ve seen enough people with a cold to last me a thousand winters.

What always fascinates me are the things that people try to use to cure their cold. I think I’ve heard everything over the last decade: garlic, ginger, peppermint, chicken soup, honey, tea, honey mixed with lemon mixed with tea, or honey mixed with lemon mixed cayenne pepper mixed with tea.   Some people rub Vicks on their feet. Other people douse their pillows in eucalyptus oil.

Another common recommendation that gets around the grape vine and social media is olive leaf extract, used in traditional ‘medicine’ for thousands of years, and those witch-doctors and shamans can’t all be wrong.

One published review described the ‘science’ of olive leaf extract: “Constituents of the olive tree, Olea europaea, have been studied and utilized in folk medicine for centuries. Olive leaf extract, derived from the leaves of the olive tree, contains phenolic compounds, specifically oleuropein, that have demonstrated potent antimicrobial, antioxidant, and anti-inflammatory activity. Oleuropein and derivatives such as elenolic acid have been shown to be effective in in vitro and animal studies against numerous microorganisms, including retroviruses, coxsackie viruses, influenza, and parainfluenza as well as some bacteria. Research suggests that olive leaf constituents interact with the protein of virus particles and reduce the infectivity and inhibit replication of viruses known to cause colds, influenza, and lower respiratory infection. Olive leaf extract has also been shown to stimulate phagocytosis, thereby enhancing the immune response to viral infection. Anecdotal reports indicate olive leaf extract taken at the onset of cold or flu symptoms prevents or shortens the duration of the disease. For viral sore throats, gargling with olive leaf tea may alleviate symptoms, possibly by decreasing inflammation and viral infectivity.” [1]

It’s always a concern when a supposedly peer reviewed journal allows an article to get through which seriously discusses anecdotal evidence as something worthy of attention. Anecdotal evidence is the weakest level of evidence possible. Anecdotal evidence is essentially just stories and opinion [2]. There’s anecdotal evidence for the Tooth Fairy. The other ‘evidence’ that this review describes is from in vitro studies, which are trials in test tubes not in people. In vitro evidence is only helpful in a general sense. Just because a reaction happens in a test tube or petri dish doesn’t mean that it will happen in a real life human being.

So then, do the claims for olive leaf extract stand up to the rigors of modern scientific enquiry or is it like every other cold and flu ‘remedy’ – just another individualised mythology?

Being sceptical, I wanted to find out. So I searched through the published medical literature for quality clinical trials that studied olive leaf extract in humans, and I found only six trials. Interestingly, all of the trials studying olive leaf extract weren’t looking at its effect on immune function but on cholesterol and blood sugar control, blood pressure, and oxidative stress.

In 2009, Kendall et al published a single-centre, randomized, single-blinded, prospective pilot comparison of the effect of dietary supplementation with olive leaf extract on the markers of oxidative stress in 45 healthy young adult volunteers. They found that olive leaf extract had no effect on oxidative stress compared to the control group [3].

Susalit et al (2011) published a double-blind, randomized, parallel and active-controlled clinical study looking at the tolerability, cholesterol-lowering and anti-hypertensive effect of Olive leaf extract in comparison with Captopril (a common blood pressure medication) in patients with early hypertension. After 8 weeks of treatment, there were similar reductions in blood pressure in both the olive leaf extract and the blood pressure pill groups. There was a significant drop in triglyceride levels in the olive leaf extract group, but not in Captopril group [4].

Wainstein et al (2012) performed a randomized controlled trial on 79 adults with non-insulin dependent diabetes, comparing a single 500mg dose of olive leaf extract with placebo over 14 weeks. They measured the HbA1c (a surrogate measurement of the average blood sugar over a three month period) and plasma insulin levels. They also did studies in rats to study the mechanism of action of the olive leaf extract. In the human trials, the subjects treated with olive leaf extract exhibited significantly lower HbA1c and fasting plasma insulin levels. This effect was thought to be reflected in the rat study which suggested that olive leaf extract reduced the digestion and absorption of starch from the intestines [5].

de Bock et al (2013) did a randomized, double-blinded, placebo-controlled, crossover trial on 46 patients in New Zealand, over a 30 week period. The participants were middle aged and overweight. The researchers were primarily studying insulin sensitivity but they also looked at glucose and insulin profiles, cytokines, lipid profile, body composition, 24-hour ambulatory blood pressure, and carotid intima-media thickness. The olive leaf extract group had a statistically significant improvement in insulin sensitivity and responsiveness of the pancreatic β-cell. Interestingly, the olive leaf extract supplementation improved some inflammatory markers, but not others, and made no difference to the patients lipid profile, blood pressure, body composition (their body fatness), carotid intima-media thickness (a risk predictor of cardiovascular disease), or liver function [6].

For completeness, de Bock lead another trial, also published in 2013, although this trial was more a study of the absorption of the compounds in olive leaf extract than a study of their effects [7]. There was a 1996 Belgian study which was written in French. I’m not very good with French, but according to the English abstract, there was no difference between the olive leaf extract and placebo in terms of blood pressure and blood sugar levels [8].

Reconciling the research on olive leaf extract makes for an interesting narrative. There are a couple of really strong, methodologically robust trials on olive leaf extract, and with positive results in favour of it. However, I can count them on one hand, and while the results are encouraging for proponents of olive leaf extract, there needs to be a lot more research before those claims can be made with certainty. And in contrast to its usual selling points, those positive effects for olive leaf extract were for blood sugar control, not the prevention or treatment of viral illnesses.

The bottom line – olive leaf extract may one day prove to be a useful herbal supplement, but there’s not enough clinical evidence to support it at the present moment. And there’s certainly no evidence that olive leaf extract will do anything for your viral upper respiratory tract infections.

So next time you get a cold, don’t bother spending money on olive leaf extract. Have a couple of paracetamol, a long hot shower and a good rest.

And if symptoms persist, don’t forget to see your GP.


[1]        Roxas M, Jurenka J. Colds and influenza: a review of diagnosis and conventional, botanical, and nutritional considerations. Alternative medicine review : a journal of clinical therapeutic 2007 Mar;12(1):25-48.
[2]        Fowler G. Evidence-based practice: Tools and techniques. Systems, settings, people: Workforce development challenges for the alcohol and other drugs field 2001:93-107.
[3]        Kendall M, Batterham M, Obied H, Prenzler PD, Ryan D, Robards K. Zero effect of multiple dosage of olive leaf supplements on urinary biomarkers of oxidative stress in healthy humans. Nutrition 2009 Mar;25(3):270-80.
[4]        Susalit E, Agus N, Effendi I, et al. Olive (Olea europaea) leaf extract effective in patients with stage-1 hypertension: comparison with Captopril. Phytomedicine : international journal of phytotherapy and phytopharmacology 2011 Feb 15;18(4):251-8.
[5]        Wainstein J, Ganz T, Boaz M, et al. Olive leaf extract as a hypoglycemic agent in both human diabetic subjects and in rats. Journal of medicinal food 2012 Jul;15(7):605-10.
[6]        de Bock M, Derraik JG, Brennan CM, et al. Olive (Olea europaea L.) leaf polyphenols improve insulin sensitivity in middle-aged overweight men: a randomized, placebo-controlled, crossover trial. PloS one 2013;8(3):e57622.
[7]        de Bock M, Thorstensen EB, Derraik JG, Henderson HV, Hofman PL, Cutfield WS. Human absorption and metabolism of oleuropein and hydroxytyrosol ingested as olive (Olea europaea L.) leaf extract. Molecular nutrition & food research 2013 Nov;57(11):2079-85.
[8]        Cherif S, Rahal N, Haouala M, et al. [A clinical trial of a titrated Olea extract in the treatment of essential arterial hypertension]. Journal de pharmacie de Belgique 1996 Mar-Apr;51(2):69-71.

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 ( 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
  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

Dr Caroline Leaf – Contradicted by the latest research

This is my most popular post by far.  I truly appreciate the support and interest in this post, but I’ve discovered and documented a lot more about Dr Leaf’s ministry in the last two years.  I welcome you to read this post, but if you’d like a more current review of the ministry of Dr Caroline Leaf, a new and improved version is here:
Dr Caroline Leaf – Still Contradicted by the Latest Evidence, Scripture & Herself

* * * * *

Mr Mac Leaf, the husband of Dr Caroline Leaf, kindly took the time to respond to my series of posts on the teachings of Dr Leaf at Kings Christian Centre, on the Gold Coast, Australia, earlier this month. As I had intended, and as Mr Leaf requested, I published his  reply, complete and unabridged (here).

This blog is my reply.  It is heavily researched and thoroughly referenced.  I think it’s fair to say that while Dr Leaf draws her conclusions from some scientific documents, there is more than enough research that contradicts her statements and opinions.  I have only listed a small fraction, and only on some of the points she raised.

In fairness, the fields of neurology and neuroscience are vast and rapidly expanding, and it is impossible for one person to cover all of the literature on every subject.  This applies to myself and Dr Leaf.  However, I believe that the information I have read, and referenced from the latest peer-reviewed scholarly works, do not support Dr Leaf’s fundamental premises.  If I am correct, then the strength and validity of Dr Leaf’s published works should be called into question.

As before, I welcome any reply or rebuttal that Dr Leaf wishes to make, which I will publish in full if she requests.  In the interests of healthy public debate, and encouraging people to make their own informed decisions on the teachings of Dr Leaf, any comments regarding the response of Mr Leaf, Dr Leaf or myself, are welcome provided they are constructive.

This is a bit of a lengthy read, but I hope it is worthwhile.

Dear Mr Leaf,

Thank you very much for taking the time out to reply to some of the points raised in my blog.  I am more than happy to publish your response, and to publish any response you wish to make public.


I published my blog posts to open up discussion on the statements made by Dr Leaf at the two meetings that I attended at Kings Christian Centre on the Gold Coast.  As you rightly point out, people should be able to make informed decisions.  A robust discussion provides the information required for people to make an informed choice.  Any contributions to this discussion from either yourself or Dr Leaf would be most welcome.

I apologise if you interpreted my blogs as judgemental, or if you believe there are any misunderstandings.  You may or may not have read my final two paragraphs from the third post, in which I acknowledged that I may have misunderstood where she was coming from, but that I would welcome her response.  If there were any misunderstandings, it is likely because Dr Leaf did not make any attempt to reference any of the statements she made on the day.  You may argue that she was speaking to a lay audience, and referencing is therefore not necessary.  However, I have been to many workshops for the lay public by university professors, who have extensively referenced their information during their presentations.  A lay audience does not preclude providing references.  Rather, it augments the speakers authority and demonstrates the depth of their knowledge on the subject at hand.


It’s interesting that you feel the need to resort to defence by association, and Ad Hominem dismissal as your primary counter to the points I raised.

Can you clarify how attending the same university as Dr Christaan Barnard, or a Nobel laureate, endorses her arguments or precludes her from criticism?  I attended the University of Queensland where Professor Ian Frazer was based.  He developed the Human Papilloma Virus vaccine and was the 2006 Australian of the Year.  Does that association enhance my argument?

Can you also clarify why a reference from a colleague was preferred to letting Dr Leaf’s statements and conclusions speak for themselves?  Dr Amua-Quarshie’s CV is certainly very impressive, no doubt about that, although he doesn’t list the papers he’s published.  (I’m assuming that to hold the title of Adjunct Professor, he’s published peer-reviewed articles.  Is he willing to list them, for the record?)

Whatever his credentials, his endorsement means very little, since both Dr Leaf and Dr Amua-Quarshie would know from their experience in research that expert opinion is one of the lowest forms of evidence, second worst only to testimonials [1].  Further, both he and Dr Leaf are obviously close friends which introduces possible bias.  His endorsement is noteworthy, but it can not validate every statement made by Dr Leaf.  Her statements should stand up on their own through the rigors of critical analysis.

On the subject of evidence, disparaging your critics is not a substitute for answering their criticism.  Your statement, “By your comments it is obvious that you have not kept up to date with the latest Scientific research” is an assumption that is somewhat arrogant, and ironic since Dr Leaf is content to use superseded references dating back to 1979 to justify her current hypotheses.


In the blog to which you referred, Dr Leaf makes a number of statements that are intended to support her case.  These include the following.

“A study by the American Medical Association found that stress is a factor in 75% of all illnesses and diseases that people suffer from today.”  She fails to reference this study.

“The association between stress and disease is a colossal 85% (Dr Brian Luke Seaward).”   But again, she fails to reference the quote.

“The International Agency for Research on Cancer and the World Health Organization has concluded that 80% of cancers are due to lifestyles and are not genetic, and they say this is a conservative number (Cancer statistics and views of causes Science News Vol.115, No 2 (Jan.13 1979), p.23).”  It’s good that she provides a reference to her statement.  However, referencing a journal on genetics from 1979 is the equivalent of attempting to use the land-speed record from 1979 to justify your current preference of car.  The technology has advanced significantly, and genetic discoveries are lightyears ahead of where they were more than three decades ago.

“According to Dr Bruce Lipton (The Biology of Belief, 2008), gene disorders like Huntington’s chorea, beta thalassemia, cystic fibrosis, to name just a few, affect less than 2% of the population. This means the vast majority of the worlds population come into this world with genes that should enable the to live a happy and healthy life. He says a staggering 98% of diseases are lifestyle choices and therefore, thinking.”  Even if it’s true that Huntingtons, CF etc account for 2% of all illnesses, they account for only a tiny fraction of genetic disease.  And concluding that the remaining 98% must therefore be lifestyle related is overly simplistic.  It ignores the genetic influence on all other diseases, other congenital, and environmental causes of disease.  I will fully outline this point soon.

Similarly, “According to W.C Willett (balancing lifestyle and genomics research for disease prevention Science (296) p 695-698, 2002) only 5% of cancer and cardiovascular patients can attribute their disease to hereditary factors.”  Science is clear that genes play a significant role in the development of cardiovascular disease and most cancers, certainly greater than 5%.  Again, I will discuss this further soon.

“According to the American Institute of health, it has been estimated that 75 – 90% of all visits to primary care physicians are for stress related problems ( Some of the latest stress statistics causing illness as a result of toxic thinking can be found at:”  These websites not peer-reviewed, and both suffer from a blatant pro-stress bias.

You’ll also have to forgive my confusion, but Dr Leaf also wrote, “Dr H.F. Nijhout (Metaphors and the Role of Genes and Development, 1990) genes control biology and not the other way around.”  So is she saying that genes DO control development?


Influence Of Thought On Health

Dr Leaf has categorically stated that “75 to 98% of all illnesses are the result of our thought life” on a number of occasions.  She repeated the same statement in her most recent book so it is something she is confident in.  However, in order to be true, this fact must be consistent across the whole of humanity.

And yet, in a recent peer-reviewed publication, Mara et al state, “At any given time close to half of the urban populations of Africa, Asia, and Latin America have a disease associated with poor sanitation, hygiene, and water.” [2]  Bartram and Cairncross write that “While rarely discussed alongside the ‘big three’ attention-seekers of the international public health community—HIV/AIDS, tuberculosis, and malaria—one disease alone kills more young children each year than all three combined. It is diarrhoea, and the key to its control is hygiene, sanitation, and water.” [3]  Hunter et al state that, “diarrhoeal disease is the second most common contributor to the disease burden in developing countries (as measured by disability-adjusted life years [DALYs]), and poor-quality drinking water is an important risk factor for diarrhoea.” [4]

Toilets and clean running water have nothing to do with stress or thought.  We live in a society that essentially prevents more than half of our illnesses because of internal plumbing, with additional benefits from vaccination and population screening.  If thoughts have any effect on our health, they are artificially magnified by our clean water and sewerage systems.  Remove those factors and any effects of thought on our health disappear from significance.  Dr Leaf’s assertion that 75 to 98% of human illness is thought-related is a clear exaggeration.

Let me be clear – I understand the significance of stress on health and the economy, but it is not the cause of 75-98% of all illnesses.  I’m not sure if there is a similar study in the US, but the latest Australian data suggests that all psychological illness only counts for 8% of visits to Australian primary care physicians [5].

In terms of cancer, I don’t have time to exhaustively list every cancer but of the top four listed in the review “Cancer Statistics 2013” [6] , here are the articles that list the gene x environment interactions:

  1. PROSTATE – There are only two risk factors for prostate cancer, familial aggregation and ethnic origin. No dietary or environmental cause has yet been identified [7].  It is most likely caused by multiple genes at various loci [8].
  2. BREAST – Genes make up 25% of the risk factors for breast cancer, and significantly interacted with parity (number of children born) [9].
  3. LUNG/BRONCHUS – Lung cancer is almost exclusively linked to smoking, but nicotine addiction has a strong hereditary link (50-75% genetic susceptibility) [10].
  4. COLORECTUM – Approximately one third of colorectal cancer is genetically linked [11].

So the most common cancer is not linked to any environmental factors at all, and the others have genetic influences of 25% to more than 50%.  This is far from being 2% or 5% as Dr Leaf’s sources state.

Also in terms of heart disease, the INTERHEART trial [12] lists the following as significant risk factors, and I have listed the available gene x environment interaction studies that have been done on these too:

  1. HIGH CHOLESTEROL – Genetic susceptibility accounts for 40-60% of the risk for high cholesterol [13].
  2. DIABETES – Genetic factors account for 88% of the risk for type 1 diabetes [14].  There is a strong genetic component of the risk of type 2 diabetes with 62-70% being attributable to genetics [15, 16].
  3. SMOKING – nicotine addiction has a strong hereditary link (50-75% genetic susceptibility) [10].
  4. HYPERTENSION – While part of a much greater mix of variables, genetics are still thought to contribute between 30% and 50% to the risk of developing high blood pressure [17].

So again, while genes are a part of a complex system, it is clear from the most recent evidence that genetics account for about 50% of the risk for cardiovascular disease, which again is a marked difference between the figures that Dr Leaf is using to base her assertions on.

Atrial Natriuretic Peptide

I am aware of research that’s studied the anxiolytic properties of Atrial Natriuretic Peptide.  For example, Wiedemann et al [18] did a trial using ANP to truncate panic attacks.  However, these experiments were done on only nine subjects, and the panic attacks were induced by cholecystokinin.  As such, the numbers are too small to have any real meaning.  And the settling is completely artificial.  Just as CCK excretion does not cause us all to have panic attacks every time we eat, ANP does not provide anxiolysis in normal day to day situations.  Besides, if ANP were really effective at reducing anxiety, then why do people suffering from congestive cardiac failure, who have supraphysiological levels of circulating ANP [19] , also suffer from a higher rate of anxiety and panic disorders than the general population? [20]

The Heart As A Mini-Brain

As for Heartmath, they advance the notion of the heart being a mini-brain to give themselves credibility.  It’s really no different to an article that I read the other day from a group of gut researchers [21] – “‘The gut is really your second brain,’ Greenblatt said. ‘There are more neurons in the GI tract than anywhere else except the brain.’”  The heart as a mini-brain and the gut as a mini-brain are both figurative expressions.  Neither are meant to be taken literally.  I welcome Dr Leaf to tender any further evidence in support of her claim.

Hard-Wired For Optimism

As for being wired for optimism, the brain is likely pre-wired with a template for all actions and emotions, which is the theory of protoconsciousness [22].  Indeed, neonatal reflexes often reflect common motor patterns.  If this is true, then the brain is pre-wired for both optimism and love, but also fear.  This explains the broad role of the amygdala in emotional learning [23] including fear learning.  It also means that a neonate needs to develop both love and fear.

A recent paper showed that the corticosterone response required to learn fear is suppressed in the neonate to facilitate attachment, but with enough stress, the corticosterone levels build to the point where amygdala fear learning can commence [24].  The fear circuits are already present, only their development is suppressed.  Analysis of the cohort of children in the Bucharest Early Intervention Project showed that negative affect was the same for both groups.  However positive affect and emotional reactivity was significantly reduced in the institutionalised children [25].  If the brain is truly wired for optimism and only fear is learned, then positive emotional reactivity should be the same in both groups and the negative affect should be enhanced in the institutionalised cohort.  That the result is reversed confirms that neonates and infants require adequate stimulation of both fear and love pathways to grow into an emotionally robust child, because the brain is pre-wired for both but requires further stimulation for adequate development.

The Mind-Brain Link

If the mind controls the brain and not the other way around as Dr Leaf suggests, why do anti-depressant medications correct depression or anxiety disorders?  There is high-level evidence to show this to be true [26-28].  The same can be said for recent research to show that medications which enhance NDMA receptors have been shown to improve the extinction of fear in anxiety disorders such as panic disorder, OCD, Social Anxiety Disorder, and PTSD [29].

If the mind controls the brain and not the other way around as Dr Leaf suggests, why do some people with acquired brain injuries or brain tumours develop acute personality changes or thought disorders?  Dr Leaf has done PhD research on patients with closed head injuries and treated them in clinical settings according to her CV.  She must be familiar with this effect.

One can only conclude that there is a bi-directional effect between the brain and the stream of thought, which is at odds with Dr Leaf’s statement that the mind controls the brain and not the other way around.


One further thing.  Can you clarify which of Dr Leaf’s peer-reviewed articles have definitively shown the academic improvement in the cohort of 100,000 students, as you and your referee have stated?  And can you provide a list of articles which have cited Dr Leaf’s Geodesic Information Processing Model?  Google Scholar did not display any articles that had cited it, which must be an error on Google’s part.  If her theory is widely used as you say, it must have been extensively cited.

I understand that you are both busy, but I believe that I have documented a number of observations, backed by recent peer-reviewed scientific literature, which directly contradict Dr Leaf’s teaching.  I have not had a chance to touch on many, many other points of disagreement.

For the benefit of Dr Leaf’s followers, and for the scientific and Christian community at large, I would appreciate your response.

I would be grateful if you could respond to the points raised and the literature which supports it, rather than an Ad Hominem dismissal or further defense by association.

Dr C. Edward Pitt


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2. Mara, D., et al., Sanitation and health. PLoS Med, 2010. 7(11): e1000363.

3. Bartram, J. and Cairncross, S., Hygiene, sanitation, and water: forgotten foundations of health. PLoS Med, 2010. 7(11): e1000367.

4. Hunter, P.R., et al., Water supply and health. PLoS Med, 2010. 7(11): e1000361.

5. FMRC. Public BEACH data. 2010  16JUL13]; Available from: <;.

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8. Alberti, C., Hereditary/familial versus sporadic prostate cancer: few indisputable genetic differences and many similar clinicopathological features. Eur Rev Med Pharmacol Sci, 2010. 14(1): 31-41.

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19. Ronco, C., Fluid overload : diagnosis and management. Contributions to nephrology,. 2010, Basel Switzerland ; New York: Karger. viii, 243 p.

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28. Kapczinski, F., et al., Antidepressants for generalized anxiety disorder. Cochrane Database Syst Rev, 2003(2): CD003592.

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