Beginning with a false premise, university researchers dredged computer simulation studies looking at associations (risk factors) and reported that one of the variables could be causal. This, it appears, now passes for science and support for public policies.
Research in support of politically correct foods are undergoing the same sorts of computer modeling machinations as research showing people cause global climate change. Reporting from the press release, MSN told the public:
Taxing soft drinks and foods high in saturated fats and providing subsidies for fruits and vegetables might encourage people to change their eating habits and possibly improve their health, according to a new study. Researchers in New Zealand analyzed 32 previous studies and concluded that there would be a 0.02 percent decline in consumption of fatty foods with each 1 percent price increase. They also determined that a 10 percent increase in the price of soft drinks would decrease consumption by between 1 percent and 24 percent….
This suggests that such food pricing strategies have the potential to reduce dietary inequalities, said Helen Eyles and colleagues from the University of Auckland and the University of Otago, in Wellington, in a journal news release. Diets high in sugar and saturated fats contribute to the development of chronic diseases, such as cardiovascular disease and diabetes.
Their article, A Systematic Review of Simulation Studies, was published in PLOS Medicine. The researchers began by explaining their premise, one also popular in public policies: junk foods, with high saturated fats and salt content, are “causative risk factors” for chronic diseases, including heart disease, strokes, diabetes, cancers and respiratory diseases. Reducing population diets of these foods, they noted, were identified as a priority action by the United Nations during its meeting on prevention and control of non-communicable diseases. “If these changes in population diet take place, the interventions will support the global goal of reducing non-communicable death rates and averting tens of millions of premature deaths within the next decade.”
So, they did a literature search for computer simulation studies published since 1990 that looked at the association between food pricing strategies, consumption and chronic diseases. They found “19 peer-reviewed papers and 13 other types of reports” to use in their analysis.
But, they admitted the majority of the included studies (27/32) were of low to moderate quality. According to the authors, there was also “substantial variability in model structures, data inputs and the types and magnitudes of food taxes and subsidies assessed.”
- They weren’t able to use meta-analysis techniques as are used with randomized controlled trials to estimate the effect of an intervention, they said, since they were combining findings from simulations and models using varying structures and mathematical techniques. So, a key aspect of their study, they said, came from synthesizing epidemiological models and estimates of price elasticity.
- They also admitted that none of the studies included in their review had attempted to validate the epidemiological model that had been used, even though “validation is important because underlying model structure and assumptions vary widely between models and are associated with uncertainty; without validation or comparison of findings with other models, it is difficult to determine whether findings are real, or in fact artefacts of the model itself.”
- Furthermore: “Most studies in this review (25/32; 78%) failed to estimate the uncertainty of model findings. Uncertainty arises from the model structure and variation in the model inputs, including food consumption data, food prices, relative risks, and PEs.”
Despite their findings that “suggests food pricing strategies have potential for changing population diets and long-term health and disease outcomes,” they wrote, “high-quality evidence is lacking, particularly with regard to the unintended effects of compensatory purchasing and the potential impacts on health equity, long-term health, and NCD mortality.”
In fact, they highlighted:
There was also some evidence that pricing strategies may result in unintended compensatory buying through cross-PEs; two moderately high quality studies estimated a potential increase in consumption of sodium in response to a saturated fat tax, and a potential increase in mortality from CVD in response to a tax on less healthy foods.
In this paper, the authors explained they did little more than pool estimates from simulated models:
A particular aim of this review was to collate and quantitatively summarise the best evidence from simulation modelling studies regarding the association between food pricing strategies, food consumption, health, and NCDs. Therefore, although the pooled estimates are based on lower quality studies, the estimates can be improved upon as more relevant, higher quality research becomes available…
Nevertheless, a correlation found in simulation models was suggested to have a causal effect:
Notwithstanding the low to moderate quality of the majority (27/32) of the included studies, the overall finding of this review is that pricing strategies have the potential to produce changes in population food consumption….
Based on modelling studies, taxes on carbonated drinks and saturated fat and subsidies on fruits and vegetables would be associated with beneficial dietary change, with the potential for improved health.
But they did admit the need for more research:
Robust evaluations built into the implementation of food pricing policies would help to answer some of these questions and engender confidence that such strategies will provide positive effects…
Of course, in the real world, fat taxes have done little to affect obesity rates or health outcomes. “While we should not expect large health benefits from fat or sugar taxes, the administrative costs are real and substantial,” Dr Eric Crampton, Senior Lecturer in Economics, University of Canterbury, told the New Zealand Science Media Centre.