Associations of vegetable and fruit intake with cognitive function and its decline: Two longitudinal studies

Abstract

Objectives: Previous studies suggested protective associations of vegetables and fruits (VF) intake with cognitive function, but evidence on specific types of VF was insufficient.

Methods: The current study included 4066 participants from 1997 to 2006 in the China Health and Nutrition Survey (CHNS) and 6170 participants from 2013 to 2020 in the Health and Retirement Study (HRS). Dietary intake (using 3-day 24-h dietary recalls in CHNS and food frequency questionnaire in HRS) and cognitive function (using the Telephone Interview for Cognitive Status-Modified, TICS-m) were measured. Linear mixed-effects models were used to estimate the beta coefficients (β) and the 95% confidence intervals (CI) to evaluate the association of VF with cognitive function (z-score) and its decline.

Results: Highest intake of total VF was associated with better cognitive function and slower cognitive decline. Differences in cognitive function z-score between the highest and lowest tertiles of VF consumption were 0.039 (95% CI: 0.002, 0.076) for CHNS and 0.063 (95% CI: 0.026, 0.100) for HRS. The corresponding differences in annual cognitive decline were 0.011 (95% CI: 0.002, 0.021) and 0.012 (95% CI: 0.003, 0.020) units respectively. Vegetables and fruits showed independent associations with cognitive function and its decline. In specific VF subgroups, when comparing the highest to the lowest tertile intake, cruciferous vegetables (β = 0.058, 95% CI: 0.017, 0.100 in CHNS and β = 0.067, 95% CI: 0.032, 0.101 in HRS) and green leafy vegetables (β = 0.036, 95% CI: -0.001, 0.073 in CHNS and β = 0.082, 95% CI: 0.046, 0.117 in HRS) was associated with better cognitive function in both cohorts. Similarly, higher intake of dark-colored vegetables (β = 0.019, 95% CI: 0.008, 0.030 for red/yellow vegetables in CHNS and β = 0.004, 95% CI: 0.001, 0.007 for green leafy vegetables in HRS) were associated with slower cognitive decline in subsequent years. Moreover, rigorous sensitivity analyses confirmed the stability of the results.

Conclusions: Our findings support the potential beneficial roles of VF, especially cruciferous vegetables, green leafy vegetables, and red/yellow vegetables, in maintaining cognitive function and slowing cognitive decline in middle-aged and older adults.

Keywords: Cognitive decline; Cognitive function; Cohort study; Fruits; Vegetables.

Fig. 1

Multivariable-adjusted associations of total and specific vegetables intake with cognitive function and cognitive decline. Notes: Models were adjusted for age, age square, sex, education (illiteracy/primary school/middle school and above), residence (urban/rural), region (northern/southern), income (low/medium/high), smoking status (never/ever), drinking status (never/ever), BMI (normal/overweight/obesity), total intake of energy (continuous), physical activities (low/medium/high), tertiles of (low/medium/high) intake of fruits, legumes, red meat, poultry, fish and aquatic products, sweets, and mutually adjusted for tertiles of (low/medium/high) intake of green leafy vegetables, red/yellow vegetables, cruciferous vegetables, starchy vegetables, fresh beans, other vegetables in CHNS, and were adjusted for age, age square, sex, race (White or Caucasian/Black or African American), education (lower than high school/high school graduated/college and above), income (low/medium/high), smoking status (never/ever), drinking status (never/ever), BMI (normal/overweight/obesity), total intake of energy (continuous), physical activities (low/medium/high) and tertiles (low/medium/high) of intake of citrus fruits, berries, other fruits, legumes, red meat, poultry, fish and aquatic products, sweets in HRS. When the intake of vegetables was treated as a continuous variable, each 200 grams/day increase in vegetables intake in the CHNS, each 3 servings/day increment of intake of total vegetables, or each 3 servings/week increment of intake of specific vegetable subgroups in HRS were analysed.