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THE ASSOCIATION BETWEEN PEANUT AND PEANUT BUTTER CONSUMPTION AND COGNITIVE FUNCTION AMONG COMMUNITY-DWELLING OLDER ADULTS

 

E.W. Katzman1, S.J. Nielsen2

 

1. Landmark Health, , USA; 2. Russell Sage College, USA

Corresponding Author: Elizabeth W. Katzman, Landmark Health, USA, ewkatzman@gmail.com

J Prev Alz Dis 2021;
Published online June 11, 2021, http://dx.doi.org/10.14283/jpad.2021.32

 


Abstract

Background: Many studies have focused on the association between diet and cognitive function. While a subset of these studies focused on a diet that includes tree nuts (TN), there is limited data on the association between peanut and peanut butter consumption (P/PB) and cognitive health.
Objective: This study investigated the association of P/PB consumption and cognitive function.
Design: This was a cross-sectional study using 2011-2014 NHANES data.
Participants/setting: Individuals 60-80 years old in 2011-2014 NHANES who had two 24-hour dietary recalls, cognitive function tests, and education level and with no history of stroke.
Measurements: P/PB and TN consumption was measured as well as participant performance on the CERAD Word Learning subtest (CERAD W-L), Animal Fluency test (AFT), and the Digit Symbol Substitution test (DSST). Scores from the three cognitive tests were dichotomized. Individuals were classified as either P/PB consumers or non-consumers and TN consumers or non-consumers. Logistic regression models examined associations between P/PB consumption, tree nut consumption, and cognitive function with adjusted models including age, sex, and education as covariates.
Results: A total of 2,454 adults, aged 60-80 years old (mean age=69.4) participated. Approximately half were male (48%), 18% were P/PB consumers, and 14% consumed TN. Participants who did not consume P/PB were more likely to do poorly on the CERAD W-L (adjusted OR=1.56, 95% CI 1.24-1.97; p<0.05), AFT (adjusted OR=1.29, 95% CI 1.03-1.61; p<0.05), and DSST (adjusted OR=1.43, 95% CI 1.12-1.82; p<0.05) when compared to those who did consume P/PB.
Conclusions: These findings suggest an association between P/PB consumption and cognitive function; however, this is a cross sectional study and a causal relationship cannot be established. More studies are needed to determine causality.

Key words: Peanuts, peanut butter, cognitive function, NHANES, diet.


 

Diets containing nuts have been associated with a reduced risk of cognitive decline (1-5). The Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) diet includes nuts and has been associated with slower cognitive decline (1) and better verbal memory (2). Consuming a Mediterranean diet supplemented with 30 grams of mixed nuts was found to improve performance on cognitive tests including the Rey Auditory Verbal Learning Test and the Color Trail Test compared to the control group (3). In a similar study, participants who consumed a Mediterranean diet supplemented with nuts also scored better on the Mini-Mental State Examination and Clock Drawing tests when compared to the control (4). A review of data from the Nurses’ Health Study associated long-term nut intake with improved overall cognitive function at baseline and highlighted a dose response between nut intake and cognitive function; however, unlike other studies, the cognitive benefit was not seen at follow-up (5).
Peanuts, though legumes, have a similar nutritional profile to tree nuts (TN). They are a common pantry item in many homes and are less expensive than TN. Although Valls-Pedret et al. demonstrated improved performance on cognitive tests with Mediterranean diets supplemented with extra virgin olive oil or mixed nuts compared to a baseline Mediterranean diet, the nut group consumed only walnuts, hazelnuts, and almonds (3). In a 2015 cross-sectional study, nut intake was associated with improved delayed memory and abstraction, while legumes may have benefited overall cognition (6). Similarly, Nooyens et al. noted higher nut intake was associated with better baseline cognitive function when compared to participants consuming less nuts, however, legumes demonstrated no significant change to cognition (7). In both studies, the authors do not indicate to which group peanuts were included thereby making it difficult to determine the association of peanuts and cognitive health.
Available research into peanut consumption and its association with cognitive function is limited. One study, examining P/PB intake and cognitive function did not find an association with Alzheimer’s Disease mortality (8). A randomized control trial noted increased cerebrovascular reactivity and a 5% improvement with short-term memory when participants consumed 56-84 grams of high-oleic peanuts six days per week for 24 weeks when compared to a nut free diet (9). This study does not compare outcomes with peanuts containing standard amounts of oleic acid. Given the limited data, the objective of this study is to investigate the association of peanut/peanut butter (P/PB) consumption with cognitive function.

 

Methods

NHANES Study Population

The National Health and Nutrition Examination Survey (NHANES) is a cross-sectional survey designed to monitor the health and nutrition of the US population (10). Cognitive testing was administered to participants 60+ years of age in the 2011-2014 NHANES study during a single interview in the Mobile Examination Center (11). Testing consisted of the Consortium to Establish a Registry for Alzheimer’s Disease Word Learning subtest (CERAD W-L), the Animal Fluency test (AFT), and the Digit Symbol Substitution test (DSST). The CERAD W-L has been used in many epidemiological studies to assess learning ability of verbal information (12). The AFT assesses categorical verbal fluency, a component of executive function and has been shown to differentiate between normal cognitive function, mild cognitive impairment, and more severe forms of cognitive impairment including Alzheimer’s disease (13-16). The DSST is part of the Wechsler Adult Intelligence Scale (WAIS III) and relies on working memory, processing speed, and sustained attention (17). Cognitive tests were administered by interviewers fluent in English and Spanish and were available in Korean, Vietnamese, and Chinese for participants (11).

Dietary Intake Assessment

For this study, two 24-hour dietary recalls from the 2011-2014 NHANES data were analyzed. The recalls were from non-consecutive days. The first 24-hour recall was collected in person in the Mobile Exam Center (MEC) and the next 24-hour recall was 3 to 10 days later by phone. The 24-hour recalls were collected on both weekdays and weekend days (18). Individuals were classified as either being a P/PB consumer or not having consumed P/PB based upon two 24-hour recalls. In addition, individuals were classified as being a TN consumer or not having consumed TN based upon the dietary recalls.

Cognitive Function Assessment and Covariates

Scores were calculated by dichotomizing the results. For the word scores: 0-10 were possible scores and three sets of word score tests were performed. The results were dichotomized into 0-18, 19-30. For the animal scores: possible scores were 0-40. The results were dichotomized 0-15, 16-40. The DSST had scores that ranged from 0-105. The variable was dichotomized into 0-45, 46-105. The other covariates that were analyzed were age (dichotomized: 60-69; 70-80), sex, and education. Education was classified as less than high school (HS), graduated from HS and some college or more.

Statistical Methods

The analytical sample included 2,454 individuals who had 2 days of dietary data, cognitive function data and education level and had no history of stroke. Logistic regression models were used to calculate odds ratios and 95% confidence intervals and examined the association between P/PB consumption, and cognitive function with TN consumption, age, sex, and education as covariates. Adjusted models examined P/PB consumption and cognitive function controlling for TN consumption. All statistical analyses were completed in SAS© version 9.4 created by SAS Institute Inc. Significance was established at p<0.05.

Ethical Considerations

Data collection protocols for NHANES 2011-2014 were approved by the CDC National Center for Health Statistics Research Ethics Review Board, an equivalent of an Institutional Review Board. All adult participants provided written and informed consent.

 

Results

Of the 2,454 participants that met criteria from the 2011-2014 NHANES data, 18% were peanut butter consumers (n=451) and 14% were TN consumers (n=347). There were no significant differences in sex and age between P/PB consumers and non-consumers (Table 1). However, there was a significant difference in education between P/PB consumers and non-consumers. Those who ate P/PB and TN consumed significantly greater amounts of total fat, monounsaturated fatty acids (MUFAs), and polyunsaturated fatty acids (PUFAs) in their diets than those who do not include P/PB and TN in their diets (p<0.01).

Table 1. Sociodemographic and dietary characteristics (n=2454)

*Statistically significant difference (p<0.05) between peanut/PB consumers and non-peanut/PB consumers; PB=Peanut Butter, HS=high school

Table 2. Comparison of fat intake of consumers and non-consumers of peanuts/peanut butter and tree nuts

*Statistically significantly different from one another at p<0.01; PB=Peanut Butter, MUFA=monounsaturated fatty acid, PUFA=polyunsaturated fatty acids

 

Tables 3-5 highlight the association between P/PB consumption, TN consumption, and the three cognitive performance tests. Those who did not consume P/PB were more likely to do poorly on the CERAD W-L (adjusted OR=1.56, 95% CI 1.24-1.97; p<0.05), AFT (adjusted OR=1.29, 95% CI 1.03-1.61; p<0.05), and DSST (adjusted OR=1.43, 95% CI 1.12-1.82; p<0.05) when compared to those who did consume P/PB. Individuals who did not consume TN were also more likely to do poorly on the CERAD W-L (adjusted OR=1.33, 95% CI 1.03-1.73; p<0.05), AFT (adjusted OR=1.37, 95% CI 1.06-1.75; p<0.05), and DSST (adjusted OR=2.09, 95% CI 1.58-2.78; p<0.05) when compared to individuals who did consume TN.

Table 3. Relationship between peanut/peanut butter consumption, tree nut consumption and performance on CERAD Word Learning subtest

*Statistically significant difference (p<0.05) between peanut/PB consumers and non-peanut/PB consumers; Adjusted model controlled for TN consumption, age, sex, education; PB=Peanut Butter, OR=Odds Ratio, CI=Confidence Interval

Table 4. Relationship between peanut/peanut butter consumption, tree nut consumption and performance on the Animal Fluency Test

*Statistically significant difference (p<0.05) between peanut/PB consumers and non-peanut/PB consumers; Adjusted model controlled for TN consumption, age, education; PB=Peanut Butter, OR=Odds Ratio, CI=Confidence Interval

Table 5. Relationship between peanut/peanut butter consumption, tree nut consumption and performance on the Digit Symbol Substitution Test

*Statistically significant difference (p<0.05) between peanut/PB consumers and non-peanut/PB consumers; Adjusted model controlled for TN consumption, age, sex, education; PB=Peanut Butter, OR=Odds Ratio, CI=Confidence Interval

 

Discussion

Using the NHANES data from 2011-2014, we observed an association between P/PB consumption and cognitive function. Participants who did not consume P/PB in the two 24-hour dietary recalls were more likely to do poorly on cognitive tests. A similar relationship was found with TN consumption. Further research is needed to confirm the association between P/PB and cognitive function.
As the prevalence of neurodegenerative diseases increases, comes an increased interest in neuroprotective foods (19-21). TN and peanuts contain neuroprotective, antioxidant and anti-inflammatory properties, as well as a large amount of MUFAs and PUFAs (19, 22). Indeed, participants consumed more MUFAs and PUFAs with P/PB and TN consumption than non-consumers; however, our study does not investigate the individual nutrients in P/PB or TN to determine the basis for this relationship. Growing evidence supports a potential link between cardiovascular disease and an increased risk for dementia and Alzheimer’s disease (23-27) and both TN and peanuts have been associated with reduced risk of cardiovascular and coronary heart disease (8, 28-30). Thereby making it possible that TN and peanuts may influence cognitive function based on cardiovascular disease risk.
To our knowledge, this investigation is the first to examine the association between P/PB consumption and cognitive function, and while studies have examined various TN or a combination of TN and peanuts, they have not focused solely on P/PB. Arab et al. observed significantly higher cognitive test scores and faster response times among walnut consumers after adjusting for age, sex, race, education, BMI, smoking, alcohol, and physical activity using NHANES data (31). Similarly, using data from the Nurses’ Health Study, O’Brien et al. demonstrated women who consumed walnuts one to three times monthly were more likely to perform better on cognitive tests when compared to women who consumed walnuts less than once monthly (5). In one five-year study, participants scored better on the Mini-Mental State Examination and Clock Drawing tests when consuming a Mediterranean diet supplemented with a combination of walnuts, hazelnuts, and almonds when compared to a nut-free, low fat group (4).
Experimental studies have also demonstrated potential benefits of TN consumption on cognitive health but have not shown a consistent effect. Verbal fluency and constructional praxis subtests scores improved over time when supplemented with Brazil nuts, although this was a pilot study consisting of 20 participants (32). The Walnuts and Healthy Aging (WAHA) study, a large dual center, single-blind clinical trial, failed to demonstrate a significant impact on cognition among healthy seniors (aged 63-79) with walnut supplementation; however, MRI scans in a subset of participants suggested walnuts may attenuate memory decline common to aging (33). Whereas young adults given banana bread with a half cup of ground walnuts did not demonstrate a significant improvement in memory, mood, or non-verbal reasoning skills, but a modest increase in inferential reasoning was observed (34). Differences in outcomes of these studies may be related to several factors including amount of nut consumed, the participant’s history of nut consumption, and the individual’s age.
The results observed in our study for TN and the three cognitive tests is consistent with the relationship between tree nuts and cognitive function in these studies and our results for P/PB showed a similar relationship. It is plausible that P/PB consumption would benefit cognitive health due to the nutritional similarities between TN and peanuts; however, we recommend further research to fully understand the association between P/PB consumption and cognitive health.
Since neurodegenerative diseases have increased and neuroprotective foods are becoming more popular (19-21), peanuts are an inexpensive and easy way for anyone to potentially help protect their cognitive function as they age. From our results, P/PB consumption is more prevalent than TN consumption, and in general, more individuals consume peanuts than tree nuts. Knowing that not only may tree nuts help delay cognitive decline but also P/PB may help delay cognitive decline is important.

Limitations

Our study is cross sectional therefore a causal relationship cannot be established. Data could not be adjusted for intrapersonal variability. More studies are needed to determine causality. Long term consumption of peanuts may have a different association with cognitive function when compared with recent consumption of peanuts. Additionally, cognitive function questionnaires were only administered to 60-80 year olds in 2011-2014. It would be helpful to compare cognitive function across a greater span of ages since we know that cognitive decline is associated with age.

 

Conclusion

These findings suggest an association between P/PB consumption and cognitive function; however, more information is needed to fully understand the relationship.

 

Disclaimer Statements: This study was funded by The Peanut Institute. E.K. and S.J.N. report no conflicts of interest.

Conflicts of Interest: E.K. and S.J.N. report no conflicts of interest.

Ethical Statement: This study complies with current laws of the country in which it was performed.

 

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