Association between more plant-based diets and 24-hour urinary creatinine excretion in 98,813 Dutch females and males: a cross-sectional study.

Abstract

Background: Despite potential health benefits and environmental gains of more plant-based diets, concerns remain about the quantity and quality of plant-based protein. Sufficient dietary protein is essential to prevent muscle loss and maintain muscle mass. However, evidence regarding the relation between plant-based diets and objectively measured muscle mass is scarce.

Objective: We investigated, cross-sectionally, the association between groups with different dietary identities and muscle mass, indicated by their 24-hour urinary creatinine excretion rate (CER, mg/24 h).

Methods: From the baseline assessment of the Dutch Lifelines Cohort 2007-2013, 59,719 females aged 42 ± 12 years and 39,094 males aged 43 ± 12 years were included in this study. Participants' CER was used to estimate total body muscle mass. Dietary identities were self-reported and categorized as vegetarian, flexitarian, other, and no dietary identity. Associations between dietary identities and CER in females and males, separately and adjusted for relevant covariates, were analyzed using linear regression modeling.

Results: Individuals with dietary identities (vegetarian, flexitarian, or other diet) had a lower protein intake than those without. Vegetarians had the lowest protein intake: vegetarian females and males consumed 0.88 ± 0.27 g/kg/day and 0.94 ± 0.29 g/kg/day whereas females and males without an explicit dietary identity consumed 1.00 ± 0.27 g/kg/day and 1.02 ± 0.29 g/kg/day. Compared with the group without an explicit dietary identity, groups with vegetarian or flexitarian dietary identities were associated with lower CER for both females (β [95%CI]: -84.9 [-97.1, -72.7] for vegetarian; -32.5 [-41.7, -23.3] for flexitarian) and males (β [95%CI]: -112.4 [-151.4, -73.4] for vegetarian; -26.7 [-50.5, -2.9] for flexitarian).

Conclusions: Individuals with identities favoring plant-based diets had a lower dietary protein intake and a lower CER, indicating lower total body muscle mass. When plant-based diets are being promoted, it is important to monitor and evaluate the potential public health impact on muscle mass.