The Potato Digger

Nutritional Epidemiology: No Longer Good Enough?

The Nutrition Source at Harvard makes one thing clear enough. Potatoes are a problem. They can give you obesity, diabetes, and heart disease. Skip across town and you’ll get a very different story from Boston University. “Nutrient-rich potatoes can be part of a healthy diet in young girls.” This kind of whiplash tells us that, in nutritional epidemiology, good enough is no longer good enough.

No, we don’t need to discard the nutritional epidemiology that gives us these absurd generalizations. But we do need to reform it, says a group of experts on nutrition research and scientific rigor. Their report comes from a virtual workshop in July and August of last year.

Middle Ground in Reform

Andrew Brown and colleagues write that nutritional epidemiology too often relies on weak methods. The methods have low internal validity and they suffer from significant sources of bias. Yet claims of causality are common, despite those limitations. Hence the claim from Harvard that potatoes will wreck your metabolic health. Some scientists argue to “bury the corpse” of nutritional epidemiology and move on. Others reflexively defend that status quo. But Brown et al write that we need to pursue a middle ground with vigor:

“Neither abolition nor minor tweaks are appropriate. Nutritional epidemiology, in its present state, offers utility, yet also needs marked, reformational renovation. Changing the status quo will require ongoing, unflinching scrutiny of research questions, practices, and reporting – and a willingness to admit that ‘good enough’ is no longer good enough.”

The Path to Reform

So the reform to pursue is straightforward. More scientific rigor in study designs, measurement, execution, and analysis comes first.  But just as important is the need for careful reporting. Following guidelines for reporting – such as CONSORT and STROBE-nut – is essential. Better transparency can help. Finally, spin can have terrible effects on public understanding of nutrition research. So it is intolerable – either in research reports or press releases.

A recent study of systematic reviews and meta-analyses reminds us how far we have to go. Only 11 percent of the studies in this analysis used systematic methods to evaluate the certainty of evidence in nutrition research.

Change will not be easy, say Brown et al. Moving to higher standards will be hard. In fact, it might affect grants and publishing opportunities. But ultimately, everyone in the field will benefit from higher credibility, attracting more talent, and doing more to advance public health. We need it.

“Good enough” is, indeed, no longer good enough in nutrition and obesity research.

Click here for the report from Brown et al.

The Potato Digger, painting by Paul Henry / WikiArt

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October 30, 2021

2 Responses to “Nutritional Epidemiology: No Longer Good Enough?”

  1. October 30, 2021 at 8:38 am, David Brown said:

    In science, certainty is determined by experiment, not statistical analysis of correlations. Epidemiology is all about correlations. Biochemistry is all about experiment.

    For decades, saturated fat and cholesterol have been characterized as bad while omega-6-rich seed oils have been characterized as good – as if nutrients could possess virtue. Here is the scientific consensus regarding saturated fats. “High intake of dietary saturated fatty acids has been associated with obesity, cardiovascular disease and diabetes in humans. Some of the basis for this association has been attributed to the ability of saturated fatty acids to promote inflammation and insulin resistance, as well as to increase adipose accumulation and risk of obesity.”

    Biochemically speaking, saturated fats have no such ability because they are not bioactive lipids.

  2. October 30, 2021 at 12:14 pm, Christopher John Lynch said:

    Thanks for pointing out this paper and the perspective!