Last month (March 2012), a study from Harvard University caused hysteria among the world’s press by claiming that meat increased the risk of an early death by up to 20%. The findings of the study, which prospectively observed 120,000 people in the US, was widely reported as proof that meat will send us all to an early grave. Since its publication, however, a growing number of scientists, journalists and experts in the field have pointed out that it does not demonstrate anything of the sort.
One of these critics was American science writer Gary Taubes, who has a background in physics but turned his attention to dietary science in the late 1990s. “A couple of my friends in the physics world suggested that if I was interested in bad science, I should write about public health, because that science is terrible,” he says. He soon discovered that epidemiology — the study on which most public health advice is based — is hugely flawed. “Everything I ever learned about how to do science right was not considered relevant in epidemiology. To call it science is to do science a disservice. It is pseudo-science, it is quackery,” he says.
In epidemiological studies, such as the Harvard study, scientists follow a population over a long period of time, recording diet and lifestyle choices and linking them to disease patterns. Taubes says this kind of study was effectively used to demonstrate the damage that smoking does to our health, but only because it revealed a 20-fold increase in the risk of lung cancer, which was a rare disease at the time. “It is very hard to explain why you are 20 times as likely to get cancer if you smoke than if you don’t, other than smoking causes lung cancer.”
Dietary studies have never returned such conclusive results. The Harvard study, for example, claimed that people who eat a lot of processed and red meat every day had a 20% increased risk of death, which is just 1.2 times the risk of those who did not.
Not only is the risk tiny, but there are a multitude of other factors which could explain why people who eat more red meat have a higher rate of heart disease and cancer, not least the fact that the official government recommendation in the US since the 1970s has been to eat less red and processed meat.
“In America since the 1960s, if you were health-conscious, you didn’t eat a lot of red meat because the saturated fat was supposed to give you heart disease and the red meat was supposed to give you colon cancer. So then you ask yourself, ‘who does eat a lot of red meat during a period when red meat was considered unhealthy?’ And you find [it is] people who aren’t health-conscious,” Taubes explains.
A closer look at the study reveals that the people who ate the most meat also smoked more, drank more alcohol, did less physical exercise and ate fewer fruits and vegetables. “And then you have to ask yourself what else goes up. I bet that sugar consumption goes up, and white bread consumption goes up and sweets and sodas and things that they weren’t actually measuring in their studies go up with meat consumption,” says Taubes.
Epidemiological studies are known as ‘hypothesis generating’ studies. In other words, they allow scientists to develop a hypothesis, such as the idea that eating meat increases the risk of death, which the scientists then test, using controlled clinical trials. When it comes to dietary studies, however, the hypothesis is often presented as fact, without proof from trials. “Good scientists would be questioning their study, looking at how their cohort could have fooled them,” Taubes explains. “But these people don’t care about that, which is why I say this isn’t a science, it is like a religion.”
Taubes traces the almost religious belief that saturated fat and meat consumption is bad for our health back to the 1950s, when a scientist, Ancel Keys, first developed a hypothesis that dietary fat consumption caused heart disease.
Keys published several observational studies, which he claimed supported his hypothesis, the most famous of which was the Seven Countries Study in 1957, which is hailed as the 'landmark' study in the diet-heart debate. In this study, Keys prospectively compared the diets and heart disease rates of Italy, Yugoslavia, Greece, Finland, the Netherlands, Japan and the US. He claimed that his findings demonstrated that cholesterol levels predicted heart risk, that saturated fat in the diet predicted cholesterol levels and heart disease, and that monounsaturated fat protected against heart disease.
Critics pointed out that Keys had chosen countries he knew would prove his hypothesis and left out those which might not — a common problem in epidemiological study. France, for example, has a relatively high fat consumption and low rates of heart disease. Subsequent observational studies comparing heart disease rates and saturated fat consumption in other countries have shown the exact opposite of Keys’ findings.
Keys’ hypothesis split the medical community and, from the 1950s, scientists set out to prove that low-fat, low-cholesterol diets increase the risk of heart disease using clinical trials. The results were mixed, with some appearing to support Key’s hypothesis but just as many challenging it. Alarmingly, many of the trials examining the effects of low-cholesterol diets found that these diets actually increased the risk of mortality from cancer.
Despite conflicting evidence, the tides started to turn in the favour of Keys’ hypothesis in the 1960s, when an anti-meat movement developed in American counter-culture. “There were all these famines in Africa and Asia and this idea that we could feed an entire village with the grain that you feed to one cow,” explains Taubes. “This anti-meat movement fed into the idea that saturated fat increased the risk of heart disease.”
The support of the American Heart Association from 1961 also helped shape opinion and scientific bias. “Once there is an institution behind it, how do you even admit you are wrong? You literally cannot be wrong, you cannot put out that press release,” says Taubes.
When the US government included the advice to eat a low-fat diet in its Dietary Goals publication, there was no turning back.
The US National Institutes of Health spent several hundred million dollars trying to prove Keys’ hypothesis, but were unable to conclusively demonstrate a link between saturated fat, cholesterol and heart disease. It was in fact a drug trial, rather than a dietary trial, which provided the ‘proof’ that led American health officials to declare a consensus on the controversy surrounding low-cholesterol, low-fat diets.
This trial — known as The Lipid Research Clinics (LRC) Coronary Primary Prevention trial — looked at the effect of the cholesterol-lowering drug cholestyramine and found that the drugs lowered the risk of mortality by just 0.2%. The scientists decided this was adequate evidence to argue not only that cholesterol-lowering drugs can help reduce the risk of heart disease, but that cholesterol-lowering diets could do the same.
“This was a drug study, but the scientists said that if a drug that lowers cholesterol can make you live longer, then a diet that lowers cholesterol can make you live longer, which is a completely unacceptable extrapolation,” says Taubes.
With US officials convinced of the benefits of a low-fat diet, the UK followed suit, despite the fact that the 1984 report from the Committee on Medical Aspects of Food Policy — which forms the basis of almost all UK public health advice — admitted that the evidence supporting dietary change fell far short of proof.
“There has been no controlled clinical trial of the effect of decreasing dietary intake of saturated fatty acids on the incidence of coronary heart disease, nor is it likely that such a trial will be undertaken,” it said.
Critics argue that by basing their dietary recommendations on epidemiology and observation, rather than clinical evidence, the UK and US governments are conducting a dangerous experiment with public health.
“If the people who are saying that saturated fat is not the cause [of heart disease] are right, it is probably the biggest food health scandal that has ever existed,” says Richard Young, policy advisor at the Soil Association.
So far, it is not an experiment which is going well. Heart attack deaths have come down since the 1970s, but Young points out that this could be attributed to the reduction of smoking and the increase in better blood pressure medication, as well as the fact that there are now 80,000 coronary interventions in the UK a year.
The incidence of other diseases, such as diabetes, have increased exponentially since dietary advice was changed. Last year, a study by the Imperial College London and Harvard University revealed that the total number of people with diabetes worldwide has more than doubled since 1980, from 153m to 347m. In the UK there are now 2.9m people with diabetes, 90% of which have the diet-related type 2 diabetes.
Digestive disorders and food intolerances have also risen considerably over the last few decades. A recent American study revealed that, today, nearly five times as many people have coeliac disease as they did in the 1950s. Obesity rates have soared from around 3% in the 1970s to 25% in the UK today. In the US, around 70% of people are now overweight or obese.
Many scientists are convinced that this is all a direct result of our changing diet, and blame rising levels of obesity and diet-related disease on increased consumption of carbohydrates and processed vegetable oils.
Clinical trials have provided evidence to back up this conclusion. Taubes points to several studies which compared the high-fat, high-meat Atkins diet with the government-recommended diet, with low fat, with lots of fruit, vegetables and wholegrains.
“All five studies showed that not only did people lose more weight when they ate the Atkins diet than when they were following the conventional diet, but their heart disease risk factors improved,” says Taubes. “Every study that looks at this finds the same; when you cut out carbohydrates, heart disease risk factors improve and diabetes risk factors improve.”
Author John Nicholson is a living example of the impact that a low-fat, low-meat diet can have on health. For 26 years, Nicholson was a vegan, who followed a diet he describes as an “extreme version of the NHS Eat Well regime”.
Despite eating a diet rich in fruits, vegetables, soya and wholegrains, however, he found that his weight crept up to 14½ stone and he suffered from irritable bowel syndrome (IBS), tiredness and regular headaches. Doctors were at a loss to explain his ailments and he desperately tried elimination diets to see if an intolerance was to blame, but nothing improved his health.
In 2010, his partner Dawn, who was also suffering from unexplained illnesses, declared that they should try eating some meat. “She had done some research and come to the conclusion that it was something that we weren’t eating rather than what we were eating which was the problem,” explains Nicholson. “I did it just to support her, but I didn’t really think it would work, I was very cynical about it.”
Within 24 hours of eating his first steak, Nicholson’s IBS disappeared. “It was incredible, it was like taking a miracle tablet. I had got so used to it, that I thought I would always be like this to one degree or another, but it just went away and has never come back.”
As weeks and months passed, every aspect of his health continued to improve. He lost weight and his headaches went away, even his eyesight improved by around 50%. “I became how I was when I was 25, before I got ill from being a vegetarian. It just felt amazing to feel so much more alive. Both physically and mentally, the change has been profound,” he explains.
As Nicholson’s health improved, his anger at the National Health Service and its dietary guidelines increased. His recent book, The Meat Fix: How a Lifetime of Healthy Eating Nearly Killed Me, is part-memoir, part-rant about the “illusion, guesswork and marketing” that forms the basis of healthy eating advice today.
“We have had our minds altered by too much modern marketing around ‘healthy foods’ and the culture of meat has become slightly suspect. We have lost our connection to it and what it really means,” he says.
Grass vs grain
Nicholson, like Taubes, dismisses the Harvard study for its failure to look at what else people were eating, such as carbohydrates and vegetable oils. He also questions whether the type of meat that people were eating could have influenced the study’s findings. “This was intensively produced meat, fed on wheat and soya, which changes the nutritional composition of the meat,” he says.
His view is shared by Young, who explains that the vast majority of beef produced in the US is reared on feedlots and fed a grain-based diet, in contrast to British cattle, which are primarily reared on grass and grass-based products.
Young points to American research, published last year, which reviewed seven studies comparing the quality of beef from grass-fed animals with that from grain-fed animals. The studies all found that while there are similar amounts of Omega 6 in both grain- and grass-fed beef, there is far more Omega 3 — which helps protect against heart disease — in grass-fed beef than in grain-fed beef. It is widely acknowledged by the scientific community that a healthy diet requires Omega 6 and Omega 3 to be balanced.
“Meat is clearly only one ingredient in the diet that contributes to this, but people today eat an awful lot of grain-based products, so they already have a diet that has the wrong balance. If they are getting meat with the wrong balance too, that is one further step in the wrong direction,” says Young.
The studies also showed that grass-fed beef had much higher levels of conjugated linoleic acid (CLA), a substance almost exclusively found in red meat, which is known to have extremely high anti-cancer properties. A University of North Carolina study, published this month, found that CLA also helps fight Crohn’s disease — a long-term condition characterised by inflammation of the lining of the digestive system.
Grass-fed meat was also found to have a much higher level of cancer-fighting antioxidants, lower overall fat and a better balance of saturated fat.
Additionally, Young points out that, over the 25 years, the majority of US beef cattle have been given both hormone and antibiotic growth promoters. Both of these are banned in UK beef production and hormone growth promoters have long been linked to cancer risk.
Taubes agrees that grass-fed meat might be better for our health than grain-fed beef, but insists that the biggest difference to health comes when people give up carbohydrates. To this end he is currently in the process of setting up an NGO to raise money for controlled experiments, which will rigorously test the hypotheses that form the basis of our public health advice.
“For the past 10 years I have been saying, ‘pay attention to the experiments’,” he says. “That is what real science is all about, doing controlled experiments.”