Sigma Nutrition Radio #589: Causal Inference in Nutrition Science – Daniel Ibsen, PhD
Dec 30, 2025
Daniel Ibsen, an epidemiologist and expert in causal inference and dietary assessment, dives into the complexities of nutrition science. He emphasizes the need for clear questions and methodical approaches to address conflicting research outcomes. Ibsen discusses the importance of food substitutions and relative dietary effects, along with the challenges of observational studies versus randomized trials. He also highlights the potential of biomarkers in understanding true dietary impacts. This conversation reveals how careful methodology can enhance the reliability of nutrition research.
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Always Ask: Compared To What?
- Nutrition exposures are inherently comparative: eating more of one food always implies eating less of something else when energy is fixed.
- Ask "compared to what?" to avoid misinterpreting associations as isolated effects.
Baseline Diets Change Effects
- A diet's effect depends on the population's baseline intake because the same change yields different absolute differences across contexts.
- Interpret studies by considering participants' starting diets before generalizing results.
Diet Is Multidimensional
- Dietary exposures are multidimensional: foods, nutrients, processing and matrix capture different aspects of intake.
- Choose the exposure level (food, nutrient, processing) that matches the causal question.