Michael Mosley was back on our screens last week (15 October 2014). I do like MM. I like his bedside manner. I like his preparedness to self-experiment and he’s becoming more and more aligned with the real foodie way of thinking, as shown with his confession on exercise here and on fat here.
However, he and the other doctors on Trust me I’m a doctor (TMIAD), are being badly let down by whoever is advising them on nutrition. Doctors receive barely a few hours of training in nutrition, despite Hippocrates’ advice “Let food be thy medicine and medicine be thy food.”
The carb experiment
Dr Chris van Tulleken, one of the twins who did the Horizon fat vs. sugar experiment in January 2014, is one of the TMIAD presenters. He took part in a ‘ground-breaking’ experiment, in an Italian restaurant, with the positioning statement: “starchy foods, like potatoes and pasta, have lots of calories but can you make these goods better for you?”
The study lead was Dr Denise Robertson from the University of Surrey. The 10 participants were given 100g (cooked weight) of pasta (with a tomato based sauce), 3 days in succession. On day one the pasta was hot, just cooked; on day two the pasta was cold, having been chilled overnight; and on day three they had the chilled pasta re-heated. This is a good experiment design, as the same subjects are used for all three interventions thus minimising any impact of different people responding differently to the same circumstances. The participants took their own blood samples every 15 minutes for the 2 hours following the pasta consumption.
Robertson’s hypothesis was that cooking the pasta differently would “reduce its calories.”
Tulleken narrated: “starchy foods like this are very quickly broken down into sugars … high sugars, and the resulting insulin, are unhealthy and they may make you feel hungry soon after a meal. And that’s the problem with refined sweet sugars, but it’s also true for things like pasta, potatoes, white rice and white bread.”
A graph was shown of the rise in blood glucose levels after eating first the freshly cooked pasta.
The average fasting blood glucose level is 5.6 mmol/L, but the normal range is wide and most people fall into a fasting blood glucose range of 3.3-7.7 mmol/L. The starting average blood glucose level for the group of 10 was 4.6 mmol/L (reading from the graph on the TV as accurately as possible). The peak blood glucose level occurred after 30 minutes – 6.6 mmol/l. At 120 minutes, the mean blood glucose levels were 5.3 mmol/L.
The chilled pasta peaked at about 6.4 mmol/L and the peak was slightly later than the freshly cooked pasta. However, the graph shown on the programme put the fresh pasta and chilled pasta alongside each other. I don’t know about you, but I found the difference between the green and blue lines completely underwhelming.
Robertson explained what had happened as follows: “We know that when a starch, such as potato or pasta, is cooked in water and then it’s allowed to cool, you’re changing the structure of that starch. You’re changing it in such a way, it becomes resistant to the normal enzymes that we have within our bodies. And, because the enzymes don’t work on it, it releases less glucose and so you get a lower glucose response.”
Tulleken clarifies “So it’s good for you because you get a lower blood sugar.”
Robertson: “You do and it’s now called resistant starch. And resistant starch, because you’re not digesting it will move down your intestine; it will end up in your large bowel and it becomes part of your dietary fibre.”
It got a bit more interesting when the two-day-old chilled pasta was re-heated. The graph for this one led Tulleken to exclaim: “astonishingly, it reduces the rise in glucose by another 50% making it even healthier.” You can see the second graph below
The blood glucose peak for the re-heated pasta is 5.7 mmol/L. The 50% is a relative claim, using the 4.6 mmol/L starting blood glucose level and is highly misleading. The red line is more different from the green line than the blue line is, but it’s not ground-breaking and here is why…
The programme could have produced a flat line – none of the ‘bad’ rise in glucose, sugar peak and insulin production by either 1) giving the subjects meat or fish or 2) giving them the pasta packaging to eat!
What this experiment has done is to make food less digestible so that it doesn’t produce the physiological changes that occur when the body registers that we have eaten food. The ultimate indigestible substance would be the cardboard box from which the pasta came. “But that would be stupid – it has no nutrients“, I hear you cry and you would hit the nail on the head. This experiment seems to completely disregard the reason why we eat. We eat food because we need nutrients to survive: essential fats; complete proteins; vitamins and minerals. This experiment is celebrating indigestibility – the pointlessness of eating something.
White pasta has little enough nutrition to start with. When it has been boiled once, chilled in a fridge overnight, left for another day and then re-boiled – how many nutrients do you think survived? I don’t know. I can tell you what it had after it was first cooked. And then compare it to the meat or fish that the participants could have enjoyed in the same Italian restaurant:
|(All per 100g of cooked product)
|Calories per 100g
|TOTAL (Ash makes up remainder)
|A (3000 IU)
|B1 (1.2 mg)
|B2 (1.3 mg)
|B3 (16 mg)
|B5 (5 mg)
|B6 (1.7 mg)
|Folate (400 mcg)
|B12 (2.4 mcg)
|C (90 mg)
|D (600 IU)
|E (15 mg)
|K (120 mcg)
|Calcium (1000-1200 mg)
|Magnesium (420 mg)
|Phosphorus (700 mg)
|Potassium (4,700 mg)
|Sodium (1,500 mg)
|Copper (0.9 mg)
|Iron (18 mg)
|Manganese (2.3 mg)
|Selenium (55 mcg)
|Zinc (11 mg)
As you can see from the table, the pasta has no essential fats, no complete protein and is pretty pointless for vitamins and minerals – manganese being an unimpressive exception. And this was before it was chilled, left and re-heated – no doubt destroying more of these paltry nutrients. The essence of this part of the programme was that a researcher managed to reduce the nutritional content of pasta by making it less digestible and this was considered a good thing?!
The really interesting points from this experiment are:
1) It shows how deeply and completely ingrained the belief is that we should be basing our meals on starchy foods. At no point did a nutritional scientist (Robertson) or a doctor (Tulleken) – both very bright people no doubt – question the wisdom of eating starchy carbohydrates in the first place. Especially in the context of the discussion about blood glucose and insulin response being desirable to avoid.
2) It was a fun admission that a calorie is not a calorie. Those who think that there is only one law of thermodynamics (and even this one doesn’t say energy in = energy out) will be beyond distressed trying to work out where the missing calories have gone.
Those who know that the second law, entropy, must be taken into account will enjoy the example of what entropy is all about – calories being lost and calorie being used in making available energy.
Those who really understand thermodynamics will know that it says nothing whatsoever about weight anyway – it is entirely about the movement of heat – and therefore it says no more about 100g of pasta than it says about 100g on the bathroom scales.
3) It was a wonderful admission, from a doctor, that starch is sugar. The starch that our government tells us to eat is sugar.
And those were the real lessons from the experiment.
The fat investigation
Later on in the programme, Mosley addressed the nutritional issue that led to the advice that we should eat more carbohydrate – the demonisation of fat. Mosley explained that he grew up in the 1960s when “medics declared war on saturated fat.” He shared that this had led to an increase in consumption of margarine and then we realised that the trans fats in spreads “are fantastically bad for the heart and they are being phased out“. Mosley described this as an example of “a public health campaign which had an unfortunate consequence.” But – Mosley set out to ask – how bad was the original advice on saturated fat?
In the introduction to this part of the programme, Mosley made all the errors that can be made in relation to fat in just a few words: “Saturated fatty acids, as they are technically known, are found in animal fats… and also in some vegetable oils, like palm and coconut, while other oils such as olive and sunflower contain polyunsaturated fatty acids.”
1) Saturated fatty acids are found in every single food that contains fat – not just animal foods – there are no exceptions.
2) Saturated fatty acids are found in all vegetable oils – not just palm and coconut – there are no exceptions.
3) Oils, such as olive and sunflower, and palm and coconut, do contain polyunsaturated fatty acids. They also contain saturated fatty acids and monounsaturated fatty acids because all foods with fat contain all three fats – there are no exceptions.
Mosley then sets off to try to answer the question” Does saturated fat really increase the risk of heart disease, as is widely believed?” But what hope does he have when he doesn’t even know what saturated fat is?!
Mosley interviews Professor Kay-Tee Khaw, from the Department of Public Health at Cambridge University, who was part of the study group that did a systematic review of 49 observational studies and 27 Randomised Controlled Trials (RCTs) with the conclusion “Current evidence does not clearly support cardiovascular guidelines that encourage high consumption of polyunsaturated fatty acids and low consumption of total saturated fats.”
Professor Christian Drevon, from the Department of Nutrition at Oslo University, was the BBCs classic counter-balance interview. He still thinks that “saturated fat in the diet is one of the major risk factors for Coronary Heart Disease“. This is where Mosley’s ignorance didn’t help, as he wasn’t armed with the right questions to challenge Drevon, who should have been asked: What is saturated fat? How can we obtain the essential fats, complete protein, vitamins and minerals that we need to survive without eating saturated fat? (and quite a lot of it) Why do you tell people to favour vegetable fats over animal fats when a tablespoon of olive oil has nearly three times the total fat and twice thee saturated fat of a 100g pork chop? And so on…
From a lack of basic understanding, it was perhaps not surprising that Mosley’s announced that his personal conclusion on saturated fat is: “These days I do eat butter and drink milk, but it’s not an excuse to pour down double cream because, whatever it’s doing to your heart, fat is very rich in calories.” Where the heck did calories come in?!
Trust me I’m a doctor?
I did enjoy the programme. The evidence for acupuncture having a visible effect under MRI, but without the mechanism being known, was honest and interesting. The paralysed patient being able to stand and move his limbs again was utterly inspirational and hugely significant for spinal cord injuries. The vitamin D study was interesting – mostly for the fact that less than half of a group of office workers had adequate vitamin D levels – more so than the discovery that sun, vitamin supplements or oily fish would work equally well and quickly at restoring those levels. There was much of value in the programme. However, it sadly showed that, when it comes to nutritional science, you may not want to trust your doctor.