This article has been re-posted on The Winnower, so it now has a digital object identifier: DOI: 10.15200/winn.142935.50603
The latest news: eating red meat doesn’t do any harm. But why isn’t that said clearly? Alarmism makes better news, not only for journalists but for authors and university PR people too.
I’ve already written twice about red meat.
In May 2009 Diet and health. What can you believe: or does bacon kill you? based on the WCRF report (2007).
In March 2012 How big is the risk from eating red meat now? An update.
In the first of these I argued that the evidence produced by the World Cancer Research Fund (WCRF) for a causal relationship was very thin indeed. An update by WCRF in 2010 showed a slightly smaller risk, and weakened yet further the evidence for causality, though that wasn’t reflected in their press announcement.
The 2012 update added observations from two very large cohort studies. The result was that the estimates of risk were less than half as big as in 2009. The relative risk of dying from colorectal cancer was 1.21 (95% Confidence interval 1.04–1.42) with 50 g of red or processed meat per day, whereas in the new study the relative risk for cancer was only 1.10 (1.06-1.14) for a larger ‘dose’, 85 g of red meat. Again this good news was ignored and dire warnings were issued.
This reduction in size of the effect as samples get bigger is exactly what’s expected for spurious correlations, as described by Ioannidis and others. And it seems to have come true. The estimate of the harm done by red meat has vanished entirely in the latest study.
The EPIC study
This is the European Prospective Investigation into Cancer and Nutrition, another prospective cohort study, so it isn’t randomised [read the original paper]. And it was big, 448,568 people from ten different European countries. These people were followed for a median time of 12.7 years, and during follow-up 26,344 of them died.
The thing that was different about this paper was that red meat was found to pose no detectable risk, as judged by all-cause mortality. But this wasn’t even mentioned in the headline conclusions.
Conclusions: The results of our analysis support a moderate positive association between processed meat consumption and mortality, in particular due to cardiovascular diseases, but also to cancer.
To find the result you have to dig into Table 3.
So, by both methods of calculation, the relative risk from eating red meat is negligible (except possibly in the top group, eating more than 160 g (7 oz) per day).
There is still an association between intake of processed meat and all-cause mortality, as in previous studies, though the association of processed meat with all-cause mortality, 1.09, or 1.18 depending on assumptions, is, if anything, smaller than was observed in the 2012 study, in which the relative risk was 1.20 (Table 2).
Assumptions, confounders and corrections.
The lowest meat eaters had only 13% of current smokers, but for the biggest red meat eaters it was 40%, for males. The alcohol consumption was 8.2 g/day for the lowest meat eaters but 23.4 g/day for the highest-meat group (the correlations were a bit smaller for women and also for processed meat eaters).
These two observations necessitate huge corrections to remove the (much bigger) effects of smoking and drinking if we want find the association for meat-eating alone. The main method for doing the correction is to fit the Cox proportional hazards model. This model assumes that there are straight-line relationships between the logarithm of the risk and the amount of each of the risk factors, e.g smoking, drinking, meat-eating and other risk factors. It may also include interactions that are designed to detect whether, for example, the effect of smoking on risk is or isn’t the same for people who drink different amounts.
Usually the straight-line assumption isn’t tested, and the results will depend on which risk factors (and which interactions between them) are included in the calculations. Different assumptions will give different answers. It simply isn’t known how accurate the corrections are when trying to eliminate the big effect of smoking in order to isolate the small effect of meat-eating. And that is before we get to other sorts of correction. For example, the relative risk from processed meat in Table 3, above, was 9% or 18% (1.09, or 1.18) depending on the outcome of a calculation that was intended to increase the accuracy of food intake records ("calibration").
The Conclusions of the new study don’t even mention the new result with red meat. All they mention is the risk from processed meat.
In this population, reduction of processed meat consumption to less than 20 g/day would prevent more than 3% of all deaths. As processed meat consumption is a modifiable risk factor, health promotion activities should include specific advice on lowering processed meat consumption.
Well, you would save that number of lives if, and only if, the processed meat was the cause of death. Too many epidemiologists, the authors pay lip service to the problem of causality in the introduction, but then go on to assume it in the conclusions. In fact the problem of causality isn’t even metnioned anywhere in either the 2012 study, or the new 2013 EPIC trial.
So is the risk of processed meat still real? Of course I can’t answer that. All that can be said is that it’s quite small, and as sample sizes get bigger, estimates of the risk are getting smaller. It wouldn’t be surprising if the risk from processed meat were eventually found not to exist, just as has happened for red (unprocessed) meat
The Japanese study
Last year there was another cohort study, with 51,683 Japanese. The results were even more (non-) dramatic [Nagao et al, 2012] than in the EPIC trial. This is how they summarise the results for the relative risks (with 95% confidence intervals).
"…for the highest versus lowest quintiles of meat consumption (77.6 versus 10.4 g/day) among men were 0.66 (0.45 — 0.97) for ischemic heart disease, 1.10 (0.84 — 1.43) for stroke and 1.00 (0.84 — 1.20) for total cardiovascular disease. The corresponding HRs (59.9 versus 7.5 g/day) among women were 1.22 (0.81 — 1.83), 0.91 (0.70 — 1.19) and 1.07 (0.90 — 1.28). The associations were similar when the consumptions of red meat, poultry, processed meat and liver were examined separately.
CONCLUSION: Moderate meat consumption, up to about 100 g/day, was not associated with increased mortality from ischemic heart disease, stroke or total cardiovascular disease among either gender."
In this study, the more meat (red or processed) you eat, the lower your risk of ischaemic heart disease (with the possible exception of overweight women). The risk of dying from any cardiovascular disease was unrelated to the amount of meat eaten (relative risk 1.0) whether processed meat or not.
Of course it’s possible that things which risky for Japanese people differ from those that are risky for Europeans. It’s also possible that even processed meat isn’t bad for you.
The carnitine study
The latest meat study to hit the headlines didn’t actually look at the effects of meat at all, though you wouldn’t guess that from the pictures of sausages in the headlines (not just in newspapers, but also in NHS Choices). The paper [reprint] was about carnitine, a substance that occurs particularly in beef, with lower amounts in pork and bacon, and in many other foods. The paper showed that bacteria in the gut can convert carnitine to a potentially toxic substance, trimethylamine oxide (TMAO). That harms blood vessels (at least in mice). But to show an effect in human subjects they were given an amount of carnitine equivalent to over 1 lb of steak, hardly normal, even in the USA.
The summary of the paper says it is an attempt to explain "the well-established link between high levels of red meat consumption and CVD [cardiovascular disease] risk". As we have just seen, it seems likely that this risk is far from being “well-established”. There is little or no such risk to explain.
It would be useful to have a diagnostic marker for heart disease, but this paper doesn’t show that carnitine or TMAO) is useful for that. It might also be noted that the authors have a maze of financial interests.
Competing financial interests Z.W. and B.S.L. are named as co-inventors on pending patents held by the Cleveland Clinic relating to cardiovascular diagnostics and have the right to receive royalty payments for inventions or discoveries related to cardiovascular diagnostics from Liposciences. W.H.W.T. received research grant support from Abbott Laboratories and served as a consultant for Medtronic and St. Jude Medical. S.L.H. and J.D.S. are named as co-inventors on pending and issued patents held by the Cleveland Clinic relating to cardiovascular diagnostics and therapeutics patents. S.L.H. has been paid as a consultant or speaker by the following companies: Cleveland Heart Lab., Esperion, Liposciences, Merck & Co. and Pfizer. He has received research funds from Abbott, Cleveland Heart Lab., Esperion and Liposciences and has the right to receive royalty payments for inventions or discoveries related to cardiovascular diagnostics from Abbott Laboratories, Cleveland Heart Lab., Frantz Biomarkers, Liposciences and Siemens.
The practical significance of this work was summed up the dietitian par excellence, Catherine Collins, on the BBC’s Inside Health programme.
Listen to Catherine Collins on carnitine.
She points out that the paper didn’t mean that we should change what we already think is a sensible diet.
At most, it suggests that it’s not a good idea to eat 1 lb steaks very day.
And the paper does suggest that it’s not sensible to take the carnitine supplements that are pushed by every gym. According to NIH
"twenty years of research finds no consistent evidence that carnitine supplements can improve exercise or physical performance in healthy subjects".
Carnitine supplements are a scam. And they could be dangerous.
Another blog on this topic, one from Cancer Research UK also fails to discuss the problem of causality. Neither does it go into the nature (and fallibility) of the corrections for counfounders like smoking and alcohol,. Nevertheless that, and an earlier post on Food and cancer: why media reports are often misleading, are a good deal more realistic than most newspaper reports.
There is no topic more widely discussed than what one should eat in order to stay healthy. And there are few topics where there evidence is so lacking in quality. This post isn’t about quackery, but about something much more important. it is about the real science (if it merits that description) behind dietary advice. I’m not an expert in nutrition, but I do know a bit about the nature of evidence. I’m continually astonished by the weakness of the evidence for some things that have become received truths, and nowhere is that more true than in nutrition.
The BMJ used my review of Gary Taube’s book, The Diet Delusion, to start off their new Round Table feature [full text link to BMJ].
The published version had some big cuts so I publish the original version here. Taubes was kind enough to send me a copy of the book after I’d mentioned his wonderful New York Times piece in my previous excursion into the murky world of diet and health, Diet and health. What can you believe: or does bacon kill you?
The biggest omission in the BMJ version was Taubes’ own ten point summary of his conclusions (on page 454).
"“As I emerge from this research, though, certain conclusions seem inescapable to me, based on existing knowledge
- Dietary fat, whether saturated or not, is not a cause of obesity, heart disease, or any other chronic disease of civilization
- The problem is the carbohydrates in the diet, their effect on insulin secretion, and thus the hormonal regulation of homeostasis – the entire harmonic ensemble of the human body. The more easily digestible and refined the carbohydrates, the greater the effect on our health, weight, and well-being.
- Sugars – sucrose and high-fructose corn syrup specifically – are particularly harmful, probably because the combination of fructose and glucose simultaneously elevates insulin levels while overloading the liver with carbohydrates.
- Through their direct effect on insulin and blood sugar, refined carbohydrates, starches, and sugars are the dietary cause of coronary heart disease and diabetes. They are the most likely dietary causes of cancer, Alzheimer’s disease, and the other chronic diseases of civilization.
- Obesity is a disorder of excess fat accumulation, not overeating, and not sedentary behaviour.
- Consuming excess calories does not cause us to grow fatter, any more than it causes a child to grow taller. Expending more energy than we consume does not lead to long-term weight loss; it leads to hunger.
- Fattening and obesity are caused by an imbalance – a disequilibrium – in the hormonal regulation of adipose tissue and fat metabolism. Fat synthesis and storage exceed the mobilization of fat from the adipose tissue and its subsequent oxidation. We become leaner when the hormonal regulation of the fat tissue reverses this balance.
- Insulin is the primary regulator of fat storage. When insulin levels are elevated – either chronically or after a meal – we accumulate fat in our fat tissue. When insulin levels fall, we release fat from our fat tissue and use it for fuel.
- By stimulating insulin secretion, carbohydrates make us fat and ultimately cause obesity. The fewer carbohydrates we consume, the leaner we will be.
- By driving fat accumulation, carbohydrates also increase hunger and decrease the amount of energy we expend in metabolism and physical activity.”
It is on these bases that Taubes suggests that the increase in obesity is, in part, a consequence of the recommendation of a low fat, and hence high sugar diet.
The Diet Delusion [ pp 601]
(published in the USA as Good Calories, Bad Calories)
Gary Taubes 2008
There is no topic more widely discussed than what one should eat in order to stay healthy. And there are few topics where the evidence is so lacking in quality. It is also a topic that is besieged by gurus, cranks and supplement hucksters.
You need to beware of misleading titles. Dietitians are good. Nutritionists are sometimes good. But titles like ‘nutritional therapist’ and ‘nutritional medicine’ are usually warning signs of alternative therapists and/or pill salespeople.
Gary Taubes is a journalist, but he is quite an exceptional journalist. His account of the importance of randomisation for the establishment of causality is one of the best ever and it was published not in an academic journal, but in the New York Times . His book, The Diet Delusion, is in the same mould. It is more complete and more scholarly than most professional scientists could manage. Not only does it cover the literature right back to Samuel Johnson, but it is also particularly good at unravelling what one might call the politics of science. And by politics I don’t mean the vast lobbying industry that has built up with the aim of selling you unnecessary supplements, but the politics of academia.
Obesity sounds simple. If you are fat it is because you eat too much or exercise too little, right? Well no, it’s not as simple as that. For a start, it has been shown time and time again that low fat diets, and exercise, have small and temporary effects on weight. The problem with diet and health revolves round causality. The law of conservation of energy is an inevitable truth, but says nothing about causality. It could imply that you get fat because you eat too much, or equally the causal arrow could point the other way and “we eat more, move less and have less energy to expend because we are metabolically or hormonally driven to get fat”. The assumption that positive caloric balance is the cause of weight gain has predominated since the 1970s and “this simple misconception has led to a century of misguided obesity research”.
At the heart of the problem is the paucity of randomised trials, which are the only way to establish causality. Those that there are have usually shown that diet does not matter as much as we are told. Taubes concludes
I think it can certainly be argued that the problem of causality has been greatly underestimated. We are warned constantly of the dangers of processed meat, on the basis of very unconvincing evidence .
This is one reason why we still know so little about the causes of obesity, diabetes and heart disease. For Taubes, a major villain was the US nutritionist Ancel Keys (1904 – 2004). His
It is quite possible that there was rather more to be said for the Atkins diet than was apparent at the time. The fact that Atkins was not a university scientist, that his views were extreme and that he was so obviously out to make a lot of money from it, gave him all the appearance of being yet another profiteering diet guru. He was dismissed by the medical establishment as a quack. Taubes points out that conflict of interest cuts both ways. Atkins’ sternest critics at Harvard were funded by General Foods, Coca-Cola and the sugar industry. It adds up to a sorry story of a conflict of vested interests and scientific vanity.
Taubes’ final judgement is harsh. He quotes Robert Merton’s description  of what science is, or should be.
He then comments
It took Taubes five years to write this book, and he has nothing to sell apart from his ideas. No wonder it is so much better than a scientist can produce. Such is the corruption of science by the cult of managerialism that no university would allow you to spend five years on a book . I find all ten points in his summary convincing. But his most important conclusion is that you cannot have any certainty without randomised trials.
The business of nutrition is greatly at fault for not having put more effort into organising randomised trials. Until they are done, we’ll never really know, and we shouldn’t pretend that we do.
2. Colquhoun, D. (3 May 2009) Diet and health. What can you believe: or does bacon kill you?.
3. Greenberg, S.A.. 2009 How citation distortions create unfounded authority: analysis of a citation network. BMJ ;339:b2680 [pdf file].
If length had allowed, there should certainly have been a reference here to Robert Lustig of UCSF. He is an academic nutritionist who supports the main thesis of Taubes’ book. See, for example, his 2005 review, Childhood obesity: behavioral aberration or biochemical drive? Reinterpreting the First Law of Thermodynamics [full
text link]. Lustig’s slide show, The Trouble with Fructose is available in the NIH web site.
There are a couple of other articles by Taubes that are well worth reading. The Scientist and the Stairmaster Why most of us believe that exercise makes us thinner—and why we’re wrong. Gary Taubes, in New York Magazine, and We can’t work it out, in the Guardian.
You can see Taubes in action on YouTube, for example in “on Cholesterol and Science Practices“, and “on Carbohydrates and Degenerative Diseases“. There is also a video of Taubes on medical grand rounds at Dartmouth-Hitchcock Medical Center in June 2009. You can see Robert Lustig on YouTube too: “Sugar: The Bitter Truth“.
22 December.2009, Unlike the serious questions dealt with in the Diet Delusion, this concerns merely another bit of the ubiquitous nutribollocks that crops up in the media, While writing this I was listening to the excellent early evening news programme, PM, run by Eddie Mair, when a diet-related topic came up, it was nonsense about how a cocktail made with vodka, cointreau, acai juice and pomegranate juice would not give you a hangover. I suppose it was meant as christmas fun but whenever I hear the words ‘antioxidant‘ or ‘superfood; I feel an email coming on. It seems that Eddie Mair liked the fact that the email contained the words ‘quack’ and ‘codswallop’ because the next thing I knew I was asked to give an interview on next day’s programme. The mp3 is here.
This post has been translated into Belorussian..
In my view traditional Chinese medicine endangers people. The proposed ‘regulation’ would do nothing to protect the public. Quite on the contrary, it would add to the dangers, by giving an official stamp of approval while doing nothing for safety.
The government’s idea of improving safety is to make sure that practitioners are ‘properly trained’. But it is the qualifications that cause the danger in the first place. The courses teach ideas that are plain wrong and often really dangerous.
Why have government (and some universities) not noticed this? That’s easy to see. Governments, quangos and university validation committees simply don’t look. They tick boxes but never ask what actually goes on. Here’s some examples of what goes on for them to think about. They show clearly the sort of dangerous rubbish that is taught on some of these ‘degrees’.
These particular slides are from the University of Westminster, but similar courses exist in only too many other places. Watch this space for more details on courses at Edinburgh Napier University, Middlesex University and the University of East London
Just a lot of old myths. Sheer gobbledygook,
SO much for a couple of centuries of physiology,
It gets worse.
Curious indeed. The fantasy gobbledygook gets worse.
Now it is getting utterly silly. Teaching students that the brain is made of marrow is not just absurd, but desperately dangerous for anyone unlucky (or stupid) enough to go to such a person when they are ill.
Here’s another herbal lecture., and this time the topic is serious. Cancer.
Herbal approaches for patients with cancer.
I’ve removed the name of the teacher to spare her the acute embarrassment of having these dangerous fantasies revealed. The fact that she probably believes them is not a sufficient excuse for endangering the public. There is certainly no excuse for the university allowing this stuff to be taught as part of a BSc (Hons).
First get them scared with some bad statistics.
No fuss there about distinguishing incidence, age-standardisation and death rates. And no reference. Perhaps a reference to the simple explanation of statistics at Cancer Research UK might help? Perhaps this slide would have been better (from CDC). Seems there is some mistake in slide 2.
Straight on to a truly disgraceful statement in slide 3
The is outrageous and very possibly illegal under the Cancer Act (1939). It certainly poses a huge danger to patients. It is a direct incentive to make illegal, and untrue claims by using weasel words in an attempt to stay just on the right side of the law. But that, of course, is standard practice in alternative medicine,
Slide 11 is mostly meaningless. “Strengthen vitality” sounds good but means nothing. And “enhancing the immune system” is what alternative medicine folks always say when they can think of nothing else. Its meaning is ill-defined and there is no reason to think that any herbs do it.
The idea of a ‘tonic’ was actually quite common in real medicine in the 1950s. The term slowly vanished as it was realised that it was a figment of the imagination. In the fantasy world of alternative medicine, it lives on.
Detoxification, a marketing term not a medical one, has been extensively debunked quite recently. The use of the word by The Prince of Wales’ company, Duchy Originals recently fell foul of the Advertising Standards Authority, and his herbal ‘remedies’ were zapped by the MHRA (Medicines and Health Regulatory Authority).
And of course the antioxidant myth is a long-disproved hypothesis that has become a mere marketing term.
“Inhibits the recurrence of cancer”! That sounds terrific. But if it is so good why is it not even mentioned in the two main resources for information about herbs?
In the UK we have the National Library for Health Complementary and Alternative Medicine Specialist Library (NeLCAM), now a part of NHS Evidence. It was launched in 2006. The clinical lead was none other than Peter Fisher, clinical director of the Royal London Homeopathic Hospital, and the Queen’s homeopathic physician. The library was developed with the School of Integrated Health at the University of Westminster (where this particular slide was shown to undergraduates). Nobody could accuse these people of being hostile to magic medicine,
It seems odd, then, that NeLCAM does not seem to thnk to think that Centella asiatica, is even worth mentioning.
In the USA we have the National Center for Alternative and Complementary Medicine (NCCAM), an organisation that is so friendly to alternative medicine that it has spent a billion dollars on research in the area, though it has produced not a single good treatment for that vast expenditure. But NCCAM too does not even mention Centella asiatica in its herb list. It does get a mention in Cochrane reviews but only as a cosmetic cream and as an unproven treatment for poor venous circulation in the legs.
What on earth is a “lymph remedy”. Just another marketing term?
“especially valuable in the treatment of breast, throat and uterus cancer.“
That is a very dramatic claim. It as as though the hapless students were being tutored in doublespeak. What is meant by “especially valuable in the treatment of”? Clearly a desperate patient would interpret those words as meaning that there was at least a chance of a cure. That would be a wicked deception because there isn’t the slightest reason to think it works. Once again there this wondrous cure is not even mentioned in either NELCAM or NCCAM. Phytolacca is mentioned, as Pokeweed, in Wikipedia but no claims are mentioned even there. And it isn’t mentioned in Cochrane reviews either. The dramatic claims are utterly unfounded.
Ah the mistletoe story, again.
NHS Evidence (NeLCAM) lists three completed assessments. One concludes that more research is needed. Another concludes that “Rigorous trials of mistletoe extracts fail to demonstrate efficacy of this therapy”, and the third says “The evidence from RCTs to support the view that the application of mistletoe extracts has impact on survival or leads to an improved ability to fight cancer or to withstand anticancer treatments is weak”.
NCCAM says of mistletoe
- More than 30 human studies using mistletoe to treat cancer have been done since the early 1960s, but major weaknesses in many of these have raised doubts about their findings (see Question 6).
- Very few bad side effects have been reported from the use of mistletoe extract, though mistletoe plants and berries are poisonous to humans (see Question 7).
- The U.S. Food and Drug Administration (FDA) has not approved mistletoe as a treatment for cancer or any other medical condition (see Question 8).
- The FDA does not allow injectable mistletoe to be imported, sold, or used except for clinical research (see Question 8).
Cochrane reviews lists several reviews of mistletoe with similar conclusions. For example “The evidence from RCTs to support the view that the application of mistletoe extracts has impact on survival or leads to an improved ability to fight cancer or to withstand anticancer treatments is weak”.
Anthroposophy is one of the highest grades of fantasy you can find. A post on that topic is in the works.
“Indicated for cancers . . . colon/rectal, uterine, breast, lung“. A cure for lung cancer? That, of course, depends on how you interpret the weasel words “indicated for”. Even Wikipedia makes no mention of any claims that Thuja benefits cancer. NHS Evidence (NeLCAM) doesn’t mention Thuja for any indication. Neither does NCCAM. Nor Cochrane reviews. That is not the impression the hapless students of this BSc lecture were given. In my view suggestions that you can cure lung cancer with this tree are just plain wicked.
Pure snake oil, and not even spelled correctly, Harry Hoxsey’s treatment centres in the USA were closed by court order in the 1950s.
At least this time it is stated that there is no hard evidence to support this brand of snake oil.
More unfounded claims when it says “treated successfully many cancer patients”. No references and no data to support the claim. It is utterly unfounded and claims to the contrary endanger the public.
Gerson therapy is one of the most notorious and unpleasant of the quack cancer treatments. The Gerson Institute is on San Diego, but their clinics are in Mexico and Hungary. It is illegal in the USA. According to the American Cancer Society you get “a strict low-salt, low-fat, vegetarian diet and drinking juice from about twenty pounds of fresh fruits and vegetables each day. One glass of juice is consumed each hour, thirteen times a day. In addition, patients are given several coffee enemas each day. Various supplements, such as potassium, vitamin B12, pancreatic enzymes, thyroid hormone, and liver extracts, are used to stimulate organ function, particularly of the liver and thyroid.”. At one time you also got several glasses of raw calf liver every day but after infections killed several people] carrot juice was given instead.
Cancer Research UK says “there is no evidence to show that Gerson therapy works as a cure for cancer”, and “The Gerson diet can cause some very serious side effects.” Nobody (except perhaps the Price of Wales) has any belief in this unpleasant, toxic and expensive folk-lore.
Again patients are endangered by teaching this sort of stuff.
And finally, the usual swipe at vaccines. It’s nothing to do with herbalism. but just about every alternative medicine advocate seems to subscribe to the anti-vaccination lobby.. It is almost as though they have an active preference for things that are known to be wrong. They seem to believe that medicine and science are part of an enormous conspiracy to kill everyone.
Perhaps this dangerous propaganda might have been ameliorated if the students had been shown this slide (from a talk by Melinda Wharton).
Left to people like this, we would still have smallpox, diphtheria. tetanus and rabies, Take a look at Vaccine-preventable diseases.
This is the sort of ‘education’ which the Pittilo report wants to make compulsory.
Smallpox in Baltimore, USA, 1939. This man was not vaccinated.
This selection of slides shows that much of the stuff taught in degrees in herbal medicine poses a real danger to public safety and to public health.
Pittilo’s idea that imposing this sort of miseducation will help safety is obviously and dangerously wrong. The Department of Health must reject the Pittilo recommendations on those grounds.