Markers of a plant-based diet relate to memory and executive function in older adults

ABSTRACT

Background

Although it is known that plant-based foods are important for physical health, little is known about the relationship between plant-based foods and cognitive health. Emerging evidence suggests that some macronutrients may influence cognition, but it is unclear which domains of cognition are involved; more importantly, it is unknown how a plant-based diet relates to cognition.

Objective

To examine associations between a plant-based dietary pattern and cognitive functioning.

Methods

Participants were 3,039 older adults who participated in the 2011-2014 waves of the National Health and Nutrition Examination Survey (NHANES). The present cross-sectional study used data on macronutrient intake from 24-hour dietary interviews, as well as performance on tests of long-term memory and executive function (i.e., delayed word recall, digit symbol substitution test, and animal fluency). Principal component analysis was used to extract a dietary pattern consistent with a plant-based diet.

Results

Greater adherence to a dietary pattern consistent with a plant-based diet was related to better performance on all cognitive tasks. Secondary analyses indicated that the associations between a plant-based dietary pattern and executive function accounted for the association between a plant-based dietary pattern and memory. Furthermore, this same plant-based dietary pattern was associated with reduced baseline inflammation in a separate dataset.

Conclusions

Experimental manipulations are needed to determine the potential causal relations of these associations, but these results suggest that a plant-based diet relates to better cognition, especially through improved executive control. Future work should also attempt to extend these results by examining potential mechanisms underlying these associations, such as reduced inflammation.

KEYWORDS:

• Diet
• memory
• executive function
• nutrition
• vegan diet
• older adults
• NHANES
• plant-based diet

Data availability statement

The data that support the findings of this study are openly available in the National Health and Nutrition Examination Survey database from the Centers for Disease Control and Prevention at https://wwwn.cdc.gov/nchs/nhanes/Default.aspx

Acknowledgements

Author contributions: Conceptualization, Writing – Review & Editing, A.P.Y., G.S.S., M.M.R.; Formal Analysis, Investigation, G.S.S., M.M.R.; Writing – Original Draft, M.M.R. All authors read and approved the final manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Notes

1 Note that the results were equivalent regardless of whether or not analyses were restricted to participants with complete data.

2 The loadings for fiber, saturated fat, polyunsaturated fat, and protein, respectively, for PC1 were −.64, .64, .26, −.31; for PC3 they were −.08, .04, .63, .77; and for PC4 they were .71, .71, .03, .12. The principal components were not rotated with an oblique transformation, and as such were uncorrelated, |r|s < .001, ps > .999, entailing that our second component could be examined independently of the others. Although they were not relevant to our a priori hypotheses, in the interest of completeness, the associations between the other principal components and the cognitive tasks were as follows. PC1 (high fat, low fiber and protein) was unrelated to any cognitive task, ps > .294. Interestingly, according to prior work, the macronutrient profile of PC1 was consistent with a dietary spectrum ranging from highly processed to unprocessed foods [67]. PC3 (high polyunsaturated fat and protein, negligible fiber and saturated fat) was related to better performance on all cognitive tasks, βs > .07, ps < .001; and PC4 (high fiber and saturated fat, negligible loadings of polyunsaturated fat and protein) was weakly related to digit symbol and fluency performance, βs < .05, ps > .016, and unrelated to recall, β < .01, p = .609.

3 It should be noted, though, that our data cannot address the possibility that additional dietary choices may have resulted in consumption of this macronutrient profile.

4 Although education is sometimes used as a measure of socioeconomic status, for the sake of completeness, we also re-ran the analyses including income (i.e., ratio of family income to poverty level) as a covariate as well. All results held, ps<.023.

Additional information

Funding

This work was supported by the National Eye Institute grant R01EY025999 to Andrew P. Yonelinas, and a UC Davis Provost Dissertation Year Fellowship to Grant S. Shields.

Notes on contributors

Michelle M. Ramey

Michelle M. Ramey, M.A., Graduate Student Researcher, University of California, Davis. Her research aims to understand how attention and diet influence memory.

Grant S. Shields

Grant S. Shields, Ph.D., Postdoctoral Scholar, University of California, Davis. Dr. Shields' research focuses on understanding how stress and related factors influence cognition and health.

Andrew P. Yonelinas

Andrew P. Yonelinas, Professor of Psychology, Center for Neuroscience, University of California, Davis. Dr. Yonelinas' research focuses on understanding the functional and neural processes underlying human memory.