Potatoes for Breakfast, Dark Vegetables for Supper?

Should we be having potatoes for breakfast? An interesting new study this week adds to the evidence that when we eat different foods might matter for health outcomes as much as our choice of foods. Specifically, this research was an analysis of mortality in persons with diabetes based on NHANES data from 2003 to 2014. In a press release from the Endocrine Society, author Qingrao Song explained their findings:

“We observed that eating potatoes in the morning, whole grains in the afternoon, greens and milk in the evening and less processed meat in the evening was associated with better long-term survival in people with diabetes. Nutritional guidelines and intervention strategies for diabetes should integrate the optimal consumption times for foods in the future.”

Translating Observations into Interventions

This study made for some great headlines. The Endocrine Society zoomed right in on the processed meat observation for its press release. “People with diabetes who eat less processed food at night may live longer” was their headline.

So is this bad news for the traditional pub fare of bangers and mash? As Dr. Song suggests, should this research feed directly into nutritional guidelines and interventions for diabetes?

Not necessarily. This observational study is valuable for informing a real test of dietary guidance and interventions. But by itself, it only tells us about a correlation, not about the effects of having someone eat their potatoes in the morning and their dark leafy greens at night.

That’s because – as these researchers mention in passing – “unmeasured confounding factors are hard to control.” Many individual characteristics and health-related behaviors correlate with eating patterns.

Growing Evidence for Chrononutrition

Make no mistake. These are interesting findings that relate to a growing interest in chrononutrition. For example, this study found less than half the risk of cardiovascular mortality for people with the highest consumption of potatoes in the morning. In people consuming the most starchy vegetables in the morning, they found less than a third as much risk. But this research cannot tell us that having people with diabetes eat their potatoes in the morning will cut their risk of death in half.

Chrononutrition – relating nutrition to time patterns – is truly a promising concept. In a recent review, Christiani Jeyakumar Henry and colleagues tell us “time of day is indicative of having an influence on the postprandial glucose response to a meal, therefore having a major effect on type 2 diabetes.”

The guidance to “eat breakfast like a king and dinner like a pauper” is credible in light of experimental evidence that higher calorie meals earlier in the day can have favorable metabolic effects.

A Complex Puzzle

Nonetheless, chrononutrition is a complex puzzle with many pieces. Different people have different chronotypes, so one size will very likely not fit all. Timing and meal quality can interact in nearly infinite ways. It seems likely that some patterns will turn out to be better than others. We need more research to figure this out. But even with exhaustive research, we doubt the evidence will support one best pattern for the timing of meals.

Human biological diversity is too great to make that a reasonable expectation.

Click here for the new research in the Journal of Clinical Endocrinology and Metabolism. For more on chrononutrition, click here, here, here, and here.

Full English breakfast at the Three Broomsticks, photograph by Ruth Hartnup, licensed under CC BY 2.0

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March 17, 2022