By Marika Sboros
At the heart of the trial of scientist Prof Tim Noakes is the diet-heart hypothesis that saturated fat causes heart disease. US investigative journalist Nina Teicholz focused on the hypothesis in her testimony in Noakes’ favour. That was at the fourth session of the Health Professions Council of SA (HPCSA) hearing in Cape Town on October 25.
Teicholz showed how the creator of that hypothesis ignored evidence showing that sugar and others carbohydrate are far more likely causes of heart disease. Here, in Part 2 of a three-part series on her evidence, she shows why low-fat diets can be lethal. Teicholz also looks at the role of sugar in the rise of chronic diseases.
The HPCSA has charged Noakes with unprofessional conduct for giving unconventional advice to a breastfeeding mother on a social network (Twitter). That was for a single tweet. In it, he said good first foods for infant weaning are low-carb, high-fat (LCHF). In other words, he was suggesting meat, full-fat dairy and vegetables.
Teicholz is author of The Big Fat Surprise. It’s a groundbreaking book that experts internationally acknowledge as changing the face of nutrition science. She based her evidence in chief at the hearing on the 10 years of research it took to write the book.
She told the hearing how US physiologist Ancel Benjamin Keys came up with the diet-heart hypothesis in the 1950s. To support it, he needed research. Keys embarked on the Seven Countries Study. Though fatally flawed, it was an “extremely influential”, study that is still well-cited.
“If you read 10,000 nutrition papers, as I’ve done, they all telescope back to Keys’ Seven Countries Study,” Teicholz said. It became the “Big Bang of modern nutrition studies”.
Study results showed exactly what Keys hoped they would: that men who ate lots of saturated fats had higher rates of cardiovascular death. That was because Keys “cherry-picked” the countries that he included in the study, Teicholz said.
He avoided countries such as Switzerland, Germany and France where he knew that people ate lots of saturated fat yet had low rates of heart disease, Teicholz said. These countries “would have ruined his findings on saturated fats”.
Teicholz asked Keys’ right-hand man, Henry Blackburn, why Keys avoided those countries. Blackburn said Keys had “just a personal aversion to being in those countries”.
She presented other problems with the Seven Countries Study, which she has documented in detail in The Big Fat Surprise. These include data “inconsistencies” which Keys could not resolve.
One error is “emblematic”. The men Keys studied on the island of Crete became the foundation for the Mediterranean diet as we know it today. Those men seemed to eat very little saturated fat and had very low rates of heart disease.
Yet of the three study periods that Keys spent collecting data on Crete, one fell during the month of Lent. That was when the islanders would have religiously avoided all meat, dairy, eggs and even fish.
“The Greek orthodox fast is a strict one,” Teicholz said. Thus, Keys must have undercounted the amount of saturated fat the Cretans ate. Keys knew of this problem but dismissed it without explanation.
One of Keys’ fellow project leaders, Alessandro Menotti, headed up the Italian part of the Seven Countries Study. Much later, in 1999, Menotti went back to re-analyse the dietary data. He found that the food that best correlated with heart disease was not saturated fats, but “sweets”, Teicholz said.
She asked Menotti how that finding escaped Keys. He told her that the Seven Countries Study leaders “did not know how to treat (sugar). We reported the facts and had some difficulty explanation our findings.”
Keys clearly knew that the hypothesis that sugar causes heart disease competed with his own, she said. He also knew that only one could be right. Keys did what he always did when dealing with inconvenient hypotheses: he went on the attack.
He suggested that financial reasons motivated all those who promoted the idea that sugar caused heart disease. Or, he said, they were “just plain wrong”.
One of the most prominent proponents of the sugar hypothesis in the 1970s was John Yudkin, a professor at Imperial College, London. Yudkin is author of Pure, White and Deadly – How Sugar Is Killing Us And What We Can Do To Stop It.
Keys imperiously dismissed Yudkin’s theory as “a mountain of nonsense”.
And while the Seven Countries Study was large and seemingly persuasive, it was still only observational. A basic principle of science remains that observational studies can only show association but not causation, Teicholz said.
For causation, clinical trials are needed, preferably randomised controlled clinical trials that are “absolutely gold standard”.
Teicholz showed how governments around the world undertook randomised control clinical trials (RCTS) on the diet-heart hypothesis throughout the 1960s and 1970s. They used foods high in vegetable oils, such as margarine and soy-filled milk.
Teicholz did not go into those in detail since a previous expert witness for Noakes, British obesity researcher Dr Zoë Harcombe, reviewed much of those studies in her evidence. Teicholz referred briefly to research that included the Finnish Mental Health study that lasted for 12 years. She also included studies that the US National Institutes of Health (NIH) funded. Among these are the LA Veterans Study, the Minnesota Coronary Survey, and the MrFit Trial,.
The NIH alone spent billions of dollars on studies, trying – and failing – to prove Keys’ hypothesis, Teicholz said. These trials were “remarkably special” as they were highly controlled, in-patient environments where researchers served all meals to participants.
Additionally, almost all these studies had “hard endpoints.” This means they had “indisputable outcomes”, such as death, which “cannot be contested”. The diagnosis of a heart attack is another end point but “a little more disputable”, Teicholz said.
Many studies today use far less reliable “intermediary endpoints”. These include lipid markers such as LDL-C (low-density lipoprotein cholesterol) and HDL-C (high-density lipoprotein cholesterol). There is “quite a lot of dispute” over those, she said, in terms of which best predicts heart-attack risk.
Altogether, the trials on the diet-heart hypothesis included more than 75 000 subjects, mostly men but some women. They showed that restricting saturated fats reduced total cholesterol. However, there was no impact on the ultimate outcome – whether or not people died of a heart attack.
In recent years, researchers globally have looked at this data. There are now more than a dozen published meta-analyses and systematic reviews, Teicholz said. Nearly all concluded that saturated fat and dietary cholesterol do not cause death from heart disease.
The research consistently shows that low-fat diets lower HDL-C (so-called “good cholesterol”). That means they actually increase the risk of heart disease.
Some official bodies are taking notice, Teicholz said. The Canadian Heart and Stroke Foundation (CHSF) is the equivalent of the AHA in the US and the Heart and Stroke Foundation of South Africa. It has re-evaluated the data. In 2015, the CHSF lifted the cap (as a percentage of calories) on saturated fats.
Although few people are aware of it, the US Dietary Guidelines for Americans also no longer recommend a low-fat diet. That’s precisely because of compelling evidence that it causes heart disease, she said. But it’s also because clinical trials on more than 52,000 people show a low-fat diet to be “ineffective in fighting any other kind of chronic disease”.
Teicholz presented disturbing evidence to show that by 1981, nearly 12 sizeable studies on humans found a link between lowering cholesterol and cancer. That was principally for colon cancer. Other research linked vegetable oil diets with an increased risk of lung cancer.
Teicholz cited Noakes’ analysis of the US Women’s Health Initiative (WHI) study on nearly 49 000 women over seven years. He found that women with the least insulin resistance at the start of the trial actually had a greater risk of developing type 2 diabetes if they were eating the low-fat diet compared to the control diet.
The low-fat diet also worsened glucose control in women with diagnosed diabetes.
Both these markers imply that the low-fat diet increased the risk for diabetes, compared to the control group eating a higher-fat diet, she said. WHI authors concluded that health professionals should exercise caution in advising women with diabetes to reduce dietary fat “unless accompanied by additional recommendations to guide carbohydrate intake”. In other words, the advice was that “women should be careful about eating so many carbs because a low-fat diet was, by definition, a high-carb diet”.
Teicholz told the hearing: “Thus, it’s fair to say that many RCTs on the diet-heart hypothesis found no evidence of benefit and some evidence of harm.”
The diet-heart hypothesis has been “the most tested hypothesis in the history of nutrition and disease”, she said. “And the results were null.”
She presented the competing carbohydrate-insulin hypothesis of obesity. Evidence to support it includes;
- More than 74 randomised controlled trials, virtually all on Western populations
- At least 32 trials of low-carb diets have lasted six months or longer
- Three lasted two years (the gold standard) to see any adverse side effects.
These trials have established that low-carb diets are safe, she said. They have also established efficacy for fighting obesity, diabetes, and heart disease (improves nearly all CVD risk factors).