The inconvenient truths behind the 'Planetary Health' diet
The inconvenient truths behind the 'Planetary Health' diet
Can we eat our way not only to better health, but also to a better planet? That is the question addressed by the EAT-Lancet Commission on Healthy Diets from Sustainable Food Systems (PDF), which launched its global Planetary Health dietary recommendations at the United Nations.
The goal of the 19 commissioners, drawn from a range of environmental, agricultural and public health disciplines, was to establish a scientific consensus on how to provide a healthy diet to a growing global population, while safeguarding the environment.
The importance, complexity and scale of this task cannot be overstated. More than 800 million people on the planet do not have enough to eat. Meanwhile, the diets of many of the other 7 billion citizens are driving a pandemic of "western" diseases. Diet-driven chronic diseases have been rising at alarming rates for several decades.
Today, 60 percent of Americans have a chronic health condition; 40 percent have two or more. More than half of Americans take a prescription drug; the average person takes four. America is the sickest country in the developed world. Many nations are following the same trend lines. Why? Because of the food we eat.
Our diet is also the largest contributor to global environmental degradation. The production, processing, transport, storage and waste of our food account for a quarter of the human contribution to climate change. They also cause biodiversity and soil loss and increase air and water pollution.
So, has the EAT-Lancet Commission achieved its goal of devising a diet that can reduce chronic disease trends and environmental damage while allowing us to feed billions more people by 2050?
Sadly, the short answer is no. The commission’s Planetary Health Diet falls short, for three reasons. First, it is founded on outdated, weak nutrition science. Second, the commission failed to achieve an international scientific consensus for its dietary targets, in spite of its claims to have done so. Third, it has suffered from biased, or at least unrepresentative, leadership.
Nutrition science in upheaval
In 1980, the U.S. government triggered a radical change in the diet of Americans by turning a theory about dietary fat and heart disease into a low-fat/high-carbohydrate nutrition policy for all. Modest changes to America’s diet already were being driven by increased consumption of cheap, starchy "staples" (corn, wheat, rice), products of agricultural industrialization. Adoption of the low-fat/high-carb model as national nutrition policy dramatically accelerated this trend. Americans dutifully cut their consumption of natural fats found in red meats, butter, whole milk, eggs and other whole foods and replaced them with leaner meats, refined oils and even more carbohydrates.
Other countries followed suit, importing U.S. dietary policy and our "healthier" low-fat, low-nutrient, high-sugar, high-carbohydrate food supply. The quality of the evidence supporting such a radical change in America’s diet was questioned at the time, including by the head of the National Academies of Science urging caution given the potential for tragic unintended consequences. But policy makers were eager to "do something" about the rise of cardiovascular disease and didn’t see a downside. Obesity and diabetes levels, however, rose sharply.
Blaming the "weakness" of those most affected has become the norm in public health circles: The assumption is that people just are just not following the good advice they have been given. In fact, we have had bad policy, based on bad science. Recent investigations have uncovered the story of nutrition studies that were ignored, poorly designed or executed, subject to bias, or even manipulated to achieve the desired result. (A multi-country study which underpinned most nutrition policy for decades pointed to the health advantage of the diet of the people of Crete — but the food data was collected during the fasting period of Orthodox Lent). The result has been the evidence-free policy making which has been the hallmark of U.S. nutrition policy for nearly half a century.
A growing chorus of prominent scientists and doctors are demanding an evidence-based overhaul of America’s nutrition policy. Advances in epigenetics, microbiome research, neuroscience, endocrinology, psychiatry and other fields have shed new light on the powerful role our diets have on the development of specific chronic diseases. The low-fat/high-carb diet is implicated in many of the major metabolic and inflammatory diseases of our time: obesity; cardiovascular disease; diabetes; Alzheimer’s; fatty liver disease; autoimmune conditions; some cancers; depression; and ADHD.
But the forces acting to maintain the status quo are very powerful. This is true for any entrenched paradigm with many vested interests, in this case the food and beverage industry, pharma industry, influential NGOs and many pockets of academia.
The same tactics used to confuse the public and policy makers in order to stall progress on smoking regulations and action on climate change are being executed today in nutrition policy.
But political pressure is growing to challenge entrenched nutritional wisdom. Following a request from Congress in 2015, America’s senior scientific body, the National Academies of Science, Engineering and Medicine, released two reports (found here and here) raising sharp questions about the scientific rigor underpinning the government’s official Dietary Guidelines for Americans (DGAs). A 2015 investigation by the BMJ (formerly British Medical Journal) went further, revealing that the DGA Committee had failed to review, or chose to ignore, "much relevant scientific literature in its reviews of crucial topics and therefore risks giving a misleading picture. The omissions seem to suggest a reluctance by the committee behind the report to consider any evidence that contradicts the last 35 years of nutritional advice."
Scientific consensus claims are misleading
The EAT Lancet Commission report states that its macronutrient ("food group") targets were "reached through international scientific consensus, based on the latest available science, and are time-bound." The commission goes so far as to compare the international scientific consensus behind its dietary targets to the scientific consensus that underpins the climate targets set by United Nations Intergovernmental Panel on Climate Change (IPCC).
The EAT-Lancet Commission’s authority, mandate, process, timeline, resources and membership were in no way comparable to the IPCC’s. Implying comparability is misleading and unethical. This false impression may lead consumers and policy makers to act based on the belief that the EAT-Lancet recommendations are grounded in an evidence-based consensus. It is not, at least not in regard to its nutritional targets.
Nutrition science is undergoing a period of scientific enlightenment akin to what occurred in climate science 30 years ago. The old paradigm is falling away, and it is not yet clear what will replace it. In other words, a "scientific consensus" on what constitutes a healthy diet is simply not possible right now.
The only real consensus achieved by the 19 members and 16 co-authors of the EAT-Lancet report is among themselves.
Bias, transparency and unsettled science
No contemporary researcher is more strongly associated with the original low-fat/high-carb nutrition paradigm than Dr. Walter Willett, an epidemiologist from Harvard School of Public Health. Willett was selected as the commission’s lead author. If this decision was a coincidence, it was a convenient one. Willett’s selection, and several decisions that followed, raise questions about whether EAT, the commission, its funders or individual members were using "public & planetary health" as cover for a number of other agendas.
When it was introduced nationwide in 1980, the low-fat portion of the low-fat/high-carbohydrate diet model had three pillars: limits on dietary cholesterol; saturated fat; and total fat. These pillars were based on an unproven hypothesis about the causes of heart disease. Decades after America’s food supply was reformulated to reduce consumption of these "bad actors," the U.S. government retracted the limits on total fat and dietary cholesterol after finding no evidence to support them. Strict saturated fat limits remain official U.S. dietary policy, although this last pillar is wobbling.
Billions of dollars have been spent on saturated fat research, largely by NIH, generating decades of data from randomized control trials involving nearly 75,000 people. These studies show no benefits from reducing saturated fats in reducing coronary heart disease events or total cardiovascular disease, including stroke. The 2015 BMJ investigation revealed that the U.S. Dietary Commission had ignored, or never reviewed, this large body of research on saturated fat.
The EAT-Lancet Commission makes saturated fat limits foundational to its diet design, citing the U.S. government’s policy as justification for the dramatic limits it puts on foods such as red meat, eggs and dairy in its "healthy reference diet" — the diet for optimum health before any modifications for environmental considerations.
However, Willett has become a minority voice about the perils of saturated fat in top nutrition circles. At a June meeting of the world’s leading nutrition scientists the BMJ hosted in Switzerland, researchers agreed that the concern over saturated fat and heart disease was "history." The BMJ editor called for a public mea culpa by nutrition scientists. Willett was in attendance. He may not have agreed with his colleagues, but as lead author and scientist on the EAT-Lancet Commission, he had a responsibility to disclose in the EAT-Lancet report that his interpretations of the science on saturated fat are not in line with other experts in his field; and to ensure the EAT-Lancet Commission had representation of alternative viewpoints.
Willett's long-held views about saturated fat have made him a leading voice about the health dangers of red meat. Was this possibly a factor in his appointment as lead author of the report? At the EAT-Lancet launch in Oslo, he compared the health impacts of eating red meat to smoking cigarettes. Given the weak evidence base against unprocessed red meat — in fact, it has nutritional advantages over many other foods — the comparison suggests ideology is trumping his scientific objectivity.
The vilification of saturated fats, meat and dairy are just three elements in the commission’s plan that are being hotly contested in health and nutrition science. Others include the commission’s recommendations on "healthy" proportions of whole grains, overall carbohydrates and sugar in the diet. Their recommendations contradict recent high-quality nutritional studies on obesity and diabetes, including work from Willett's colleague at Harvard’s School of Public Health, David Ludwig. Given that 30 percent of the global population and most people in many western nations struggle with metabolic syndrome (increased blood pressure, high blood sugar, excess body fat around the waist, and abnormal cholesterol or triglyceride levels that increase risk of heart disease, stroke and diabetes), adoption of the EAT-Lancet Commission proposals, either through policy changes or shifts in consumer behavior, risks repeating, and possibly exacerbating, the mistakes we made 40 years ago.
The dangers of white hat bias
In public health, there is a term for "bias leading to the distortion of information in the service of what may be perceived to be righteous ends."It is called white hat bias. This is the trap the EAT-Lancet report falls into.
Nutrition is an arena where such bias could have profound consequences. It would not be the first time. Similar good intentions nearly a half century ago inadvertently made diet the leading cause of our global health and healthcare crises.
The scale of our health crisis is on par with the projected climate impacts of the future including premature deaths, large scale human suffering and economic impact.
For example, diet-related chronic diseases cost the U.S. economy nearly $3 trillion a year — that’s 16 percent of America’s GDP. By comparison, the U.S. Fourth National Climate Assessment estimates the economic impact of climate change on the U.S. economy around 10 percent of GDP by 2100.
None of this diminishes the urgent need for aggressive action to curb climate change, especially through policies such as a carbon tax and indeed, many recommendations on food production and waste in the EAT-Lancet report.
But the attempt to produce a scientifically credible dietary plan aligning nutrition science with environmental goals was doomed to fail from the start. The science on climate change is essentially settled. The science on nutrition is in flux. Prematurely forcing them together will, in the end, serve neither.