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Thomas et al., 2025

Here we investigate the impacts of media advocating plant-based diets. Search volume for popular films explains the majority of variance in searches for plant-based food, but is not associated with consumption. For three documentaries, we estimated that a standard deviation increase in searches for each film increases searches for plant-based food by up to 43% in the following week. Our findings can inform approaches for raising awareness of sustainable diets.

Research question. Do popular media that advocate plant-based diets measurably shift public interest and food purchasing at the national scale? The authors study the six most popular releases they identified across media types: Forks Over Knives (2011), Cowspiracy (2015), What the Health (2017), Okja (2017), The Game Changers (2018) and You Are What You Eat (2024). Nature

Design and data.

  1. They ran a systematic search (269 candidates; 28 met criteria for discouraging animal-based foods) and selected the six most popular for primary analysis using a threshold of ≥10% of Okja’s peak Google Trends popularity. Films accounted for 75% of eligible media but 95.7% of peak search volume; health-framed content dominated popularity. Nature

  2. Outcomes combined national Google Trends time series (Jan 2004–May 2024) for “plant based,” “vegan,” and “vegetarian” (split into Informative vs Behaviour query categories) with US consumption/demand measures: milk and plant-based milk purchases (Nielsen, IRI) and meat demand (USDA-based indices). PubMed

  3. Analytically, they first show predictive associations and then estimate lagged causal effects using autoregressive distributed-lag models with time-varying confounder control, plus negative controls and sensitivity analyses; the study was preregistered and all code/data are public. OSF+1

Key findings.
• Films strongly predict search interest. Adding the six film time series to models of “plant based” searches raised explanatory power from adjusted R²≈0.14 (seasonality only) to 0.64 overall, and to 0.77 for Behaviour queries (e.g., recipes, restaurants). Results replicated worldwide (adjusted R²≈0.70 overall; 0.82 behaviour). Nature
• Causal, short-run effects on searches (1-week lag). A one-standard-deviation increase in searches for three health-focused documentaries increased US searches including “plant based” the following week by 24% for What the Health, 9% for The Game Changers, and 8% for You Are What You Eat. For Behaviour queries specifically, the estimated increases were 43%, 11%, and 11%, respectively. Parallel worldwide effects were 20%, 18%, and 6% overall, and 31%, 17%, and 7% for behaviour. PubMed
• No clear effects on consumption/demand. Despite clear lifts in search interest, the authors “generally do not detect” effects on nationwide purchases of milk/plant-based milk, plant-based meat market share, or on beef/pork/chicken demand in the short windows examined; one sensitivity analysis suggested a delayed decline in beef demand after You Are What You Eat, but this was not a primary, consistent result. PubMed

Interpretation. Documentary films can be powerful attention catalysts: they move people from awareness to intention-proximal behaviours (searching recipes, restaurants), but this did not translate into near-term shifts in measured purchases/demand at the national level in the study windows. The authors propose several reasons: national demand metrics reflect upstream supply-chain measures and may react more slowly; conversion from intent to purchase likely needs sustained exposure and enabling environments (price, availability, defaults). PubMed

Policy and advocacy implications. Because initial openness is a prerequisite for dietary change, campaigns might leverage health-framed narratives similar to What the Health, The Game Changers, and You Are What You Eat to spark interest, then pair media pushes with policy and institutional changes (e.g., defaults, procurement, availability) to convert interest into behaviour. The paper situates this alongside recent US municipal initiatives (NYC “Eat A Whole Lot More Plants,” LA County procurement motion). Nature

Methods and transparency notes.
• Weekly/monthly series; lagged models with confounder controls; robustness via negative controls and E-value-style sensitivity. OSF

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