Conrad, Drewnowski, & Love, (2023)

An NHANES study of 8k Americans between 2008 and 2017 (1022 plant-based) found that a plant based diet was cheaper than all other popular diets examined (Low grain, low carb, low fat, and fasting).

This was even controlling for food waste, and demographics.

Plant based was defined as anyone whose meat consumption was reported to be below 1 oz in a 24 hour period.

Introduction

Few studies have evaluated the sustainability of popular diet patterns in the US, which limits policy action and impedes consumer efficacy to make sustainable dietary changes. This study filled this gap by evaluating the relationship between diet quality, greenhouse gas emissions (GHGE), and diet cost for plant-based, restricted carbohydrate, low grain, low fat, and time restricted diet patterns.

Methods

Dietary data were retrieved from the National Health and Nutrition Examination Survey (2011–2018, n = 8,146) and linked with data on GHGE and food prices from publicly available databases. Diet quality was measured using the Healthy Eating Index-2015. The present study (1) compared the mean diet quality, GHGE, and diet cost between diet patterns, (2) evaluated the association of diet quality to GHGE and diet cost for each diet pattern, and (3) estimated the contribution of food sources to GHGE and diet cost for each diet pattern.

Results

Higher diet quality was associated with lower GHGE for the general population and for most diet patterns (p < 0.01) except for the plant-based and time restricted diet patterns (p > 0.05). Higher diet quality was associated with higher cost for the general population and for all dietary patterns (p < 0.01) except the time restricted diet pattern (p > 0.05). Protein foods, mostly beef, accounted for the largest share of GHGE (29–40%) and diet cost (28–47%) for all diet patterns except plant-based.

The low fat diet pattern had the highest diet quality score (52.8, 95% CI: 52.0, 53.7) and the time restricted diet pattern had the lowest diet quality score (43.7, 95% CI: 41.8, 45.7; Figure 1A). The diet quality scores for the plant-based (48.0, 46.1, 49.9), low grain (48.4, 47.1, 49.8), and restricted carbohydrate (47.7, 46.9, 48.5) diet patterns were similar. The diet quality score for the general population was 49.0 (48.4, 49.5). The plant-based diet pattern had the lowest GHGE (4.3 kg CO2eq, 95% CI: 4.0, 4.6 kg CO2eq); the GHGE for the low grain (6.5 CO2eq, 6.2, 6.9 CO2eq), restricted carbohydrate (6.7 CO2eq, 6.5, 6.9 CO2eq), and time restricted (6.1 CO2eq, 5.6, 6.7 CO2eq) diet patterns were similar; and the GHGE for the time restricted diet pattern was similar to the low fat diet pattern (5.8 CO2eq, 5.6, 6.7 CO2eq; Figure 1B). The GHGE for the general population was 6.1 kg CO2eq (5.9–6.2 kg CO2eq). The plant-based diet pattern had among the lowest diet cost ($13.79, 95% CI: $13.10, $14.47) and was similar to the time restricted ($15.98, 95% CI: $14.62, $17.33) diet pattern (Figure 1C). The low grain diet pattern ($18.45, $17.04, $19.85) was similar to the time restricted, low fat ($18.74, $17.90, $19.58), and restricted carbohydrate ($20.79, $20.06, $21.52) diet patterns. The diet cost of the general population was $18.87 ($18.42–$19.32).

if diet cost for gen pop was $18.87 and PB was $13.79 then PB diet was

(18.87-13.79)/18.87

Discussion

Higher diet quality was associated with lower GHGE but was often accompanied by higher diet cost. These sustainability trade-offs can help inform major policy discussions in the US and shed light on further research needs in the area of food systems transformation.

Related

• Berners-Lee et al., 2012
• Willits-Smith et al., 2020