Just How Broadly Can We Define Diet-Related Disease?

“Poor diet is the leading cause of mortality in the U.S. due to the direct relationship with diet-related chronic diseases.” Emily Matthews and Emma Kurnat-Thoma tell us this in a recent article for Frontiers in Public Health. Rationalizing this conclusion is easy enough. In Nutrients, Sareen Gropper defines diet-related disease to incorporate almost all of the leading causes of death. It is a broad category, loosely defined, “including obesity, cardiovascular disease, hypertension, stroke, type 2 diabetes, metabolic syndrome, some cancers, and perhaps some neurological diseases.”

In PLOS One, Ceria Halim and colleagues take it a bit further with a systematic review from which they conclude “high adherence to Mediterranean Diet is a protective factor against COVID-19.”

Quite a Leap from Associations

The trouble with these broad definitions is that they require quite a leap of faith. This is a leap from an association of health with self-reported dietary behaviors to a belief in effectiveness of these behaviors for producing objectively better health outcomes.

But if you look closely, some of these observations of associations are a bit shaky. Take the study of Mediterranean diet and COVID-19 for instance. In this systematic review, four studies found a correlation of adherence to a Mediterranean diet and COVID risk. One did not. One study found a correlation with risk for severe COVID symptoms. Two did not. This is a mixed picture and certainly not evidence for a causal relationship of diet to health outcomes.

Likewise, we find a false presumption – that the “root cause” of obesity is a poor diet – woven into much of the dialogue about diet-related disease. In fact, obesity is caused by much more than diet alone.

Nutrition Is Vital for Good Health

With all that said, we can still insist that nutrition is vital for good health. Medical nutrition therapy will not cure cancer, diabetes, heart disease, or obesity. But it is indeed a helpful tool for promoting good health in people living with these diseases.

For a long time, people presumed that we could wave a magic wand of nutrition support over obesity and make it go away. It didn’t work. Fortunately, no such presumption has been as dominant in other “diet-related” diseases like cancer and heart disease.

No, food is not medicine. It is much more than medicine. And good nutrition is essential for a healthy life. It is even more essential for a richly enjoyable life.

Click here for the Matthews paper, here for the Gropper paper, and here for the Halim review.

The Feast, painting by Paul Cezanne / WikiArt

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September 15, 2024