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Vol.:(0123456789)
European Journal of Nutrition
https://doi.org/10.1007/s00394-024-03328-8
ORIGINAL CONTRIBUTION
Impact ofvegetarianism oncognition andneuropsychological status
amongurban community‑dwelling adults inTelangana, South India:
across‑sectional study
KeotshepilePreciousBojang1 · VaralakshmiManchana1
Received: 5 September 2023 / Accepted: 10 January 2024
© The Author(s), under exclusive licence to Springer-Verlag GmbH Germany 2024
Abstract
Purpose The potential benefits of vegetarian diets in reducing cognitive impairment have garnered attention due to existing
mixed results; hence, our study aims to examine the impact of vegetarianism on cognitive function and neuropsychological
status among urban community-dwelling adults from Telangana.
Methods The dietary patterns were self-reported and dietary data collected using a Food Frequency Questionnaire while
cognitive function was assessed using Mini-Mental State Examination (MMSE) and depression, anxiety, and stress (DASS-
21) questionnaire for psychological measures. Adults (N = 304) aged 40years and above, who followed either a vegetarian or
non-vegetarian diet for at least 6months prior to data collection, scored MMSE ≥ 19 indicating mild cognitive impairment,
and were recruited using convenience sampling.
Results Among the participants, vegetarians (n = 155) exhibited significantly better mood states compared to non-vegetarians
(n = 149), as indicated by lower scores on the DASS subscales for depression (10.0 ± 0.06 vs. 17.0 ± 0.07, p = < 0.001), anxi-
ety (4.0 ± 0.05 vs. 6.0 ± 0.07, p = 0.005), and stress (8.0 ± 0.02 vs. 10.0 ± 0.05, p = 0.007). Vegetarians also demonstrated
superior cognitive functioning compared to non-vegetarians, as indicated by higher MMSE scores (26.0 ± 0.04 vs. 24.0 ± 0.03,
p = < 0.001). MMSE scores were inversely correlated with depression, anxiety, and stress for vegetarians (ρ = −0.371,
p = 0.000; ρ = −0.027, p = 0.734; and ρ = −0.105, p = 0.914), respectively. Similar to the vegetarians group, MMSE scores
were negatively correlated with depression (ρ = −0.059), but the correlation is not significant.
Conclusion Vegetarianism exerted a positive influence on the cognitive and neuropsychological status of the investigated
population. Nevertheless, additional research is required to comprehend the underlying mechanisms that elucidate the long-
term effects of vegetarianism and plant-based nutritional interventions on brain health.
Keywords Vegetarianism· Cognition· Mental health· Nutrition· Plant-based diet
Introduction
The prevalence of cognitive decline, a condition closely
associated with the aging process, is becoming a rapidly
growing public health concern. Cognitive abilities tend to
change with age, and many cognitive functions show meas-
urable differences in individuals around middle age, over the
age of 40. These changes can include declines in processing
speed, working memory, and certain aspects of executive
function [1, 2]. Some studies have reported subtle cognitive
decline during the transition from early 40s into middle
adulthood [3–5]. Identifying cognitive changes and risk fac-
tors in individuals aged 40 and above is crucial for develop-
ing early interventions and preventive measures to maintain
cognitive health and potentially delay cognitive decline.
India in general is experiencing a demographic shift with
an increasing aging population [6], and as people grow older,
the risk of cognitive impairment, including neurodegenera-
tive conditions such as Alzheimer’s disease and dementia,
becomes higher. The National Mental Health Survey [7]
revealed that mental health disorders have impacted 10.6%
of the elderly population. Different factors contribute to the
rise of cognitive decline and mental health issues. Accord-
ing to a study by Shriraam etal. [8] and the Indian Council
* Varalakshmi Manchana
lakshmi@uohyd.ac.in
1 School ofMedical Sciences, University ofHyderabad,
Hyderabad, Telangana, India
European Journal of Nutrition
of Medical Research (ICMR), the prevalence of diabetes,
hypertension, and cardiovascular diseases in South India is
higher compared to other regions in the country, and these
diseases are risk factors for cognitive impairment as sup-
ported by Arshad etal. [9]. Rapid urbanization and lifestyle
changes in South Indian cities have also led to an increase in
risk factors for depression and cognitive impairment, includ-
ing unhealthy diets, sedentary lifestyles, and high-stress lev-
els [10, 11].
Diet, as a fundamental aspect of physical health, is now
being acknowledged as a potential influencer of cognitive
function and mental health. Nutrition plays a vital role in
physical and cognitive functioning in adults [12]. Malnutri-
tion and risk of malnutrition are found to have a significant
association with cognitive impairment in aging adults [13].
The brain, a vital organ responsible for complex cognitive
processes and emotional regulation, requires a diverse array
of nutrients for optimal functioning [14]. The implemen-
tation of dietary interventions and the provision of nutri-
tion education have the potential to effectively mitigate the
occurrence of cognitive impairment and premature chronic
illnesses in older individuals. Plant-based diets do not only
play a crucial role in mitigating age-related cognitive decline
and Alzheimer’s disease, but they also contribute signifi-
cantly to increasing life expectancy [15, 16].
Furthermore, numerous studies have investigated the
effects of diet on cognitive function and have provided valu-
able insights into the intricate relationship between nutri-
tion and brain health [17, 18]. The previous research further
discovered that dietary patterns with a high intake of fruits,
vegetables, whole grains, fish, and nuts were linked to a
decreased risk of cognitive decline and dementia [19–21].
Oxidative stress and inflammation are recognized as
underlying mechanisms contributing to cognitive decline
[22]; however, fruits and vegetables are abundant sources of
antioxidants and anti-inflammatory agents, which can help
counteract these processes due to polyphenols which appear
to be valuable potential agents for neuroprotection [23–25].
A vegetarian diet typically offers a reduced cholesterol
and saturated fat intake, while providing a higher intake of
dietary fiber and numerous phytochemicals which are ben-
eficial to human health. It is characterized by an increased
consumption of fruits, vegetables, whole grains, legumes,
nuts, and various soy products [26].
The relationship between vegetarianism and mental
health or mood has also been explored but the results are
mixed [27], some studies highlighting that vegetarian diets
are linked to more depressive symptoms and anxiety [28,
29] while some associate them with lower risk of mental
disorders [30–32]. This field has seen diverse findings in
different geographical regions, different study populations,
and variations in cultural factors; therefore, a clearer articu-
lation of our study’s contribution is essential, more so that it
features individuals with varied age groups from early 40s,
and it focuses on a region where vegetarian diets are not just
a dietary choice but deeply rooted in culture and tradition.
Beyond its ethical and environmental considerations,
vegetarianism has been linked to several health-related ben-
efits, including a decreased likelihood of developing chronic
diseases such as cardiovascular disease [33], type 2 diabe-
tes [34], obesity [35], and certain types of cancer [36, 37].
However, the specific effects on cognition and neuropsy-
chological status have received less attention thus warrant-
ing exploration and understanding; hence, our study aims to
fill this gap by examining the impact of a vegetarian-based
diet on the cognitive health and neuropsychological status
of healthy individuals in South India in order to promote
healthy aging, quality life, and mental health at population
level and also help to identify strategies for preventing the
onset of cognitive impairment at an earlier stage.
Methods
Study design andsetting
A population-based cross-sectional study comprising 304
participants. Figure1 aged 40years and above was con-
ducted in Ranga Reddy district, Telangana in India. Includ-
ing participants in their forties (40s) helps to establish a
baseline for cognitive function and track changes and poten-
tial risk factors as they age. Convenience sampling method
was employed, and participants were recruited verbally
through community outreach. Participants who followed
either the vegetarian or non-vegetarian diet, could speak
and understand English, and also have MMSE score of ≥ 19,
indicating mild cognitive impairment [38], were included.
Based on cultural variations in the Indian context, vegetar-
ians were identified as people who excluded meat and animal
foods as well as seafood from their diet, primarily focusing
on plant-based foods and consuming milk and milk prod-
ucts as well as eggs while non-vegetarians were those that
consumed animal based foods and/or products in addition
to plant-based and vegetable diet.
Adults meeting the study inclusive criteria were screened
and enrolled into participation and those with severe cogni-
tive impairment, prior chronic illnesses, current or past his-
tory of substance abuse, subjects with acute psychiatric or
neurological disease, and subjects taking cognitive function-
ing medication were excluded. At the baseline, after giving
informed consent, 155 vegetarians and 149 non-vegetarians
were enrolled and asked to provide their medical history,
they underwent a physical examination, and had vital signs
monitored and nutritional status evaluated. The survey
included three parts: a general basic demographic detail
questionnaire, a Food Frequency Questionnaire (FFQ) [39],
European Journal of Nutrition
and two cognition and psychometric tests, the Depression
Anxiety and Stress Scale (DASS-21) [40] and MMSE [38].
Survey
Participants were required to follow either the vegetarian or
non-vegetarian diet for at least 6months prior. Adherence
to vegetarianism was assessed using Food Frequency Ques-
tionnaire detailing food consumption for the past 6months.
To ensure the accuracy of participants’ reported diet types,
we employed a combination of self-reporting and structured
interviews during the recruitment process. Participants were
initially screened based on their self-reported dietary habits,
and those who identified as either vegetarian or non-vege-
tarian were further interviewed by trained nutritionist. The
FFQ was a 132-item quantitative FFQ that was developed
from 24-h recalls in South India and validated in a South
Indian population to estimate macro- and micronutrient
intakes [39]. To accommodate the cultural differences in
cuisine, we made slight modifications to the Food Frequency
Questionnaire (FFQ) by incorporating additional commonly
consumed food items in South India, reflecting the local
dietary preferences. The FFQ data were used to examine
the average intake of single nutrients, i.e., macro- and micro-
nutrients by participants with the help of the Indian Food
Composition table [41]. Participants are asked to report their
usual frequency of consumption of various food items over
the past 6months. The response options typically include
categories such as “never”, “rarely”, “once a month”, “2–4
times a month”, etc. The data collected through the FFQ
were then structured into different food groups or categories
such as fruits, vegetables, grains, dairy, meats, etc. Within
these categories, the vegetarian and non-vegetarian food
items were segregated. We then calculated the mean daily
energy and selected nutrient content of the reported diet for
each individual, with the help of the Indian Food Composi-
tion table to estimate the intake of specific nutrients such
as vitamins, minerals, and macronutrients. Use of nutrient
supplementation was not taken into consideration. Once the
data were quantified, comparisons were made between the
dietary habits of vegetarians and non-vegetarians.
The primary objective of the DASS-21 was to evaluate
three distinct negative emotional states in nonclinical popu-
lation. These states include depression (D), which exam-
ines feelings of sadness, hopelessness, devaluation of life,
self-criticism, lack of interest, loss of pleasure, and inertia.
Anxiety (A) assesses various aspects including physiologi-
cal arousal, muscular tension, situational anxiety, and the
subjective experience of anxious emotions. Lastly, the stress
(S) component measures difficulties in relaxation, nervous
arousal, and tendencies toward being easily agitated, irrita-
ble, overreactive, and impatient [40].
Consisting of a total of 21 questions, the questionnaire
comprises three scales, each containing seven items. These
items are further divided into subscales based on similar
content. Participants were provided with instructions to rate
the severity and frequency of their experiences regarding
each emotional state during the preceding week. They rated
on a 5-point scale, where higher scores indicated a higher
degree of disturbance or disruption in mood. Participants are
instructed to rate the severity and frequency of their experi-
ences of each emotional state over the past week, using a
Fig. 1 Participants recruitment
flow diagram
European Journal of Nutrition
5-point scale. Higher scores indicate a greater level of dis-
ruption in mood.
The Mini-Mental State Examination questionnaire [38]
was also validated by the help of a trained expert who eval-
uated the clarity, relevance, and cultural appropriateness
of the questionnaire for its reliable, validity, and suitabil-
ity for the intended population and purpose. Pilot testing
was also done in a small sample (n = 4), and the reliability
and validity of the translated questionnaire was also tested
using Cronbach’s alpha to examine the internal consistency
(α = 0.84). The cut-off score of 19 or below was used as a
potential indicator of cognitive impairment [42].
The reliability of the research instruments basic demo-
graphic detail questionnaire and DASS-21 was (α = 0.81)
and (α = 0.77: depression, α = 0.79: anxiety, and α = 0.84:
stress), respectively, confirmed by Cronbach’s alpha, and
the data collected were entered into Excel sheets, analyzed,
and interpreted using descriptive and inferential statistics
as per the objectives of the study by using SPSS (version
29.0). The internal consistency reliability of all scales was
deemed acceptable and found to be similar to the previous
research findings.
Statistical analysis
All outcome measures were subjected to descriptive statis-
tics, and the data were presented as mean ± standard error
(SE). The association between variables in the study were
evaluated using Spearman’s correlation coefficient. Analysis
of data was performed by Statistical Package for the Social
Sciences (SPSS, version 29.0.1 for macOS, 2022, Chicago
IL), and p values < 0.05 were considered significant.
Results
Sociodemographic details
The data reported below (Table1) for 304 included par-
ticipants from Ranga Reddy district, Telangana, India.
Participants were grouped as vegetarians (n = 155) or non-
vegetarians (n = 149). Percentage distribution of participants
was based on their demographic details such as gender, age,
education, occupation, family type, marital status, religion,
and dietary pattern. These variables provide insights into
the characteristics and diversity within the sample popula-
tion. The largest proportion of participants (37.2%) in the
study belonged to the 40–49 age group, followed by 23.7%
in the 50–59 age group, and the majority of participants are
females (54.6%). Nuclear families are the most prevalent
family type, and a significant proportion of respondents are
married. Education-wise, the majority have completed high
school, while a smaller proportion have attained university/
college education. The occupation distribution is varied,
with employment being the most common status. Hinduism
is the predominant religion among the respondents. Lastly,
the dietary pattern shows a roughly equal split between veg-
etarian and non-vegetarian preferences.
Nutritional composition comparison using food
frequency questionnaire
Table2 compares the micro- and macronutrient consump-
tion between vegetarians (VEG) and non-vegetarians (Non-
veg). Non-veg participants tend to have a higher calorie
intake in comparison with their vegetarian counterparts
(2499 vs. 64.10kcal vs. 2091 ± 44.71kcal, respectively,
p = < 0.001), and they consume significantly more carbo-
hydrates than vegetarians. However, vegetarians have a
slightly higher mean protein intake than non-vegetarians
(109.86g vs. 104.74g, p = 0.033). There is no significant
difference in the mean total fat consumption between the two
groups. Comparing the vitamins and minerals intake, veg-
etarians have a significantly higher intake of calcium, folic
acid (Vitamin B9), and Vitamin C while, on the other hand,
non-vegetarians have a significantly higher intake of iron,
riboflavin (Vitamin B2), and Vitamin B12. No significant
difference was observed between the two groups in terms
of sodium intake.
Dietary pattern andsociodemographics
Table3 displays the participants selected demographic char-
acteristics by dietary pattern. Vegetarians were younger than
non-vegetarians (42 ± 0.11years vs. 53 ± 0.09years, respec-
tively; p = < 0.001); moreover, vegetarian participants were
identified to be more educated than their non-vegetarians
counterparts (44% vs. 15.9%, respectively; p = < 0.001), and
most of them were employed.
Association betweendietary pattern, cognition,
andneuropsychological status
Table4 presents the mean DASS-21 scores and MMSE
scores by diet group. Mean DASS scores of the three sub-
scales for vegetarians were significantly lower than the
non-vegetarians (10.0 ± 0.06 vs. 17.0 ± 0.07, p = < 0.001;
4.0 ± 0.05 vs. 6.0 ± 0.07, p = 0.005; and 8.0 ± 0.02 vs.
10.0 ± 0.05, p = 0.007), respectively, for depression, anxi-
ety, and stress thus indicating that vegetarians were found
to have better mood, more cheerful, and content than non-
vegetarians. The MMSE scores of vegetarian participants
were also significantly higher than that of non-vegetarians
(26 ± 0.04 vs. 24 ± 0.03, p = < 0.001), depicting a better cog-
nitive health for individuals who followed a vegetarian diet.
European Journal of Nutrition
Group correlation analysis betweenmean MMSE
andDASS‑21 scores
Spearman’s correlation was done to find the association
between mental health and cognitive function among veg-
etarians and non-vegetarians (Table5). MMSE scores were
inversely correlated with depression, anxiety, and stress for
vegetarians (ρ = −0.371, p = 0.000; ρ = −0.027, p = 0.734;
and ρ = −0.105, p = 0.914), respectively. A positive correlation
between depression and anxiety (ρ = 0.147, p = 0.068) as well
as depression and stress (ρ = 0.003, p = 0.966) was observed.
Similar to the vegetarians group, MMSE score was negatively
correlated with depression (ρ = −0.059), but the correlation
is not significant (p-value = 0.478). A significant negative cor-
relation between MMSE scores and anxiety (ρ = −0.131) as
well as stress (ρ = −0.135) was also observed.
Discussion
The primary objective of this cross-sectional study was to
examine the potential impacts of vegetarianism on cognition
and neuropsychological status. Our findings revealed that
vegetarians exhibited better cognitive health and better mood
scores compared to non-vegetarians. These results suggest a
potential link between dietary choices and cognitive function-
ing, adding to the growing body of the literature examining
the impact of vegetarianism on mental health. According to
our survey results, individuals who identified as vegetarians
reported significantly lower scores in terms of depression,
anxiety, and stress compared to non-vegetarians as measured
by DASS-21, shown in Fig.2. The results from the assess-
ment of cognitive function by MMSE also complement the
DASS-21 scores, where vegetarians prove to have better cog-
nitive function as shown in Fig.3 measured in five domains,
i.e., orientation, registration, attention, recall, language, and
visual–spatial skills. In our study, a significant inverse cor-
relation was observed between cognitive function scores and
depression, indicating that as MMSE scores decline, there is
a significant increase in depression symptoms. This aligns
with existing research highlighting the association between
depression and cognitive function [43, 44]. Depression is rec-
ognized as a risk factor for the onset of cognitive decline and
dementia [45]; however, the temporal relationship between
depression and cognitive impairment remains uncertain and
necessitates further investigation. It is essential to note that
correlation does not imply causation, and the interpretation
of our results hinges on the study’s context and the specific
characteristics of the sample population.
Vegetarians in the study had more intake of protein, cal-
cium, folate, and Vitamin C but low intake of Vitamin B12,
compared to non-vegetarians. On the other hand, non-veg-
etarians consumed more carbohydrates, sodium, riboflavin,
iron, and Vitamin B12. Protein is essential for the synthesis
of neurotransmitters, which play a crucial role in mood regu-
lation and cognitive function. The higher intake of protein
among vegetarians suggests a potential positive impact on
mental health, as adequate protein is vital for overall brain
function [46]. Calcium is also essential for various neurologi-
cal functions, including neurotransmitter release and nerve
transmission [47]. One study on Chinese subjects has posi-
tively associated folic acid with improved cognitive function
by reducing the levels of peripheral inflammatory cytokines
[48]. Vitamin C as an antioxidant plays a major role in
improving mood and cognitive function, there is evidence
suggesting that Vitamin C deficiency is related to adverse
mood and cognitive effects [49, 50]. Despite the deficiency
of Vitamin B12, Indian vegetarian diets are deemed adequate
to meet recommended dietary allowances [51].
Cognition encompasses a range of mental processes,
including attention, memory, executive functions, and
information processing. Several studies have explored the
impact of vegetarianism on cognitive function, aiming to
determine whether a plant-based diet influences cognitive
abilities positively, negatively, or remains neutral [52, 53].
Some research suggests that plant-based diets, rich in anti-
oxidants, phytochemicals, and other beneficial compounds,
may have neuroprotective effects, potentially promoting cog-
nitive health [54–57]. However, other studies have reported
potential concerns related to nutrient deficiencies, particu-
larly those associated with Vitamin B12 and omega-3 fatty
acids, which are predominantly found in animal-based food
sources [58, 59]. Evaluating the available evidence and iden-
tifying potential mechanisms involved are crucial for under-
standing the relationship between vegetarianism and cogni-
tive function. Vegetarian diets are mostly reported to be low
in long-chain omega-3 fatty acids [60]; however, the results
from our study show that despite the above-mentioned nutri-
tional deficit, vegetarians prove to have better mental health
as compared to non-vegetarians in regard to stress, depres-
sion, and anxiety. Compared to non-vegetarians, vegetarians
often exhibit elevated levels of antioxidants in their blood-
stream and experience reduced oxidative stress; therefore,
these factors may contribute to the higher cognitive function
abilities observed among vegetarians [61, 62].
Our findings align with the previous studies that have
explored the cognitive benefits of a vegetarian diet. For
instance, one study investigated the impact on cognitive
function when comparing plant-based vegetarian and non-
vegetarian dietary patterns in healthy older individuals as
part of the Adventist Health Study-2 cohort. The findings
suggested that individuals adhering to a more consistent
dietary pattern, characteristic of vegetarians, exhibited bet-
ter memory and language abilities. In a study conducted by
Giem etal. [21], which explored the connection between
the consumption of animal products and the occurrence
European Journal of Nutrition
of dementia in two cohort sub-studies involving vegans,
vegetarians, and heavy meat eaters, findings revealed
that matched subjects who included meat in their diet
were more than twice as likely to develop dementia com-
pared to their vegetarian counterparts (relative risk 2.18,
p = 0.065). Additionally, in the Tzu Chi Vegetarian Study
Fig. 2 a–c Comparison a
depression, b anxiety, and c
stress scores between vegetar-
ians and non-vegetarians
European Journal of Nutrition
(TCVS) involving 5710 participants, individuals adher-
ing to a vegetarian diet exhibited a lower risk of dementia
compared to non-vegetarians, even after accounting for
various covariates [19]. Specifically, vegetarians demon-
strated a decreased risk of clinically evident dementia in
comparison with non-vegetarians, with an adjusted hazard
ratio of 0.671 (confidence interval 0.452–0.996, p < 0.05).
Similarly, a recent meta-analysis reported that plant-based
diets, including vegetarian and vegan diets, were associ-
ated with improved cognitive function across different age
groups [63]. These studies, along with our own, provide
converging evidence supporting the positive impact of
vegetarianism on cognitive abilities.
Several mechanisms could explain the observed rela-
tionship between vegetarianism and cognitive functioning.
First, vegetarian diets are generally abundant in nutrients
such as antioxidants, omega-3 fatty acids, and B vitamins.
These nutrients have been linked to enhanced cognitive
health and functioning, and they play crucial roles in neu-
ronal function and maintenance, synaptic plasticity, and
neuroprotection [64]. Therefore, the higher intake of these
nutrients in vegetarians may contribute to their enhanced
cognitive performance. Moreover, vegetarian diets are
often associated with lower levels of inflammatory mark-
ers [65]. Chronic inflammation has been implicated in the
pathogenesis of cognitive decline and neurodegenerative
diseases [66]. By reducing inflammation, vegetarian diets
may protect against cognitive impairment and support brain
health. Another likely mechanism of the vegetarian diets’
effect on cognitive outcomes could be linked to the role of
phytoestrogens, which are bioactive compounds abundant
in soy and appear to exert some neuroprotective effect [67].
Mental health refers to the state of an individual’s over-
all psychological, emotional, and social well-being which
influence their thoughts, emotions, and behaviors [68].
Emerging evidence suggests that dietary patterns may influ-
ence mental health outcomes, as specific diets have been
linked to an increased susceptibility to mental health disor-
ders such as depression, anxiety, and stress [69]. In the con-
text of vegetarianism, researchers have sought to investigate
whether this dietary choice has any impact on mental health
and emotional well-being; however, there are conflicting
findings and debates surrounding nutritional adequacy and
the potential risk of nutrient deficiencies within a vegetarian
diet [70, 71]. Hibbeln etal. [59] found a positive associa-
tion between depression and vegetarianism for South West
England men after adjustment for sociodemographic factors.
In this specific cohort, vegetarians exhibited higher average
depression scores compared to non-vegetarians, with a mean
difference of 0.96 points (95% confidence interval + 0.53
to + 1.40). The authors considered nutritional deficien-
cies as a potential contributing factor but also acknowl-
edged that the possibility of reverse causation could not be
entirely ruled out from their analysis. Likewise, Li etal. [72]
observed that a vegetarian diet might be linked to depressive
symptoms in older Chinese men. Following adjustments for
potential confounders, it was found that elderly men adher-
ing to a vegetable-based diet exhibited a higher prevalence
of depression compared to their male counterparts with a
meat-based diet. However, this association was not observed
among women.
Another study has suggested potential link between veg-
etarianism and improved mental health, hypothesizing that
the consumption of plant-based diets may provide an array
of nutrients and phytochemicals that positively influence
mood and emotional regulation [73]. Our study also found
that vegetarians had better mood scores compared to non-
vegetarians. This finding aligns with the previous research
Fig. 3 Comparison of cognitive
function scores per dietary pat-
tern as measured by MMSE
European Journal of Nutrition
demonstrating a link between vegetarianism and improved
mental well-being. Findings from a recently published
prospective cohort study [74] revealed that adhering to a
Taiwanese vegetarian diet might decrease the likelihood of
experiencing depression. The study included over 12,000
participants associated with the Taiwanese Buddhist Tzu Chi
Foundation since 2005. Within this specific cohort, individu-
als following a vegetarian diet exhibited a lower incidence
of depressive disorders (2.37 vs. 3.21 per 10,000 person-
years) compared to their non-vegetarian counterparts. Fur-
thermore, Jin etal. [75] reported a 43% lower likelihood
of depression among vegetarians (p = 0.023) in their study
involving South Asians in the US. However, they empha-
sized the need for longitudinal examinations to substantiate
and validate their findings. Another study consisting of a
nationally-representative sample of the US adults examined
whether adherence to a vegetarian diet was linked to depres-
sion [76]. The findings indicated that a vegetarian diet was
linked to decreased odds of depression, as defined by the
Patient Health Questionnaire-9 (PHQ-9) (odds ratio [OR]
0.49 [95% confidence interval {CI} 0.24–0.98], p = 0.047).
This association remained significant even after adjusting for
age, sex, income, ethnicity, and marital status.
The underlying mechanisms for this relationship are
not yet fully understood but could involve factors such as
increased consumption of fruits and vegetables, which are
rich in mood-enhancing nutrients such as folate and mag-
nesium [77]. Moreover, numerous amino acids, including
lysine, tyrosine, methionine, tryptophan, arginine, and
β-alanine, have demonstrated a protective effect against
depression and anxiety [78]. These amino acids play a cru-
cial role as precursors for neurotransmitters such as dopa-
mine and serotonin, which are essential for mood regulation
[79]. The absence of certain pro-inflammatory compounds
found in meat and fish, such as arachidonic acid, may also
contribute to the improved mood observed among vegetar-
ians [32].
India is a nation of great diversity, encompassing a vast
population of more than 1.3 billion individuals who hail
from various religious, caste, and ethnic backgrounds;
therefore, these kinds of comprehensive nutritional stud-
ies become particularly important due to its high number
of vegetarians [80] compared to most countries globally;
hence, the need to understand the unique dietary needs and
potential nutritional gaps among this population. Vegetarian
diets and their health effects are different among diverse eth-
nic groups and across various geographic areas. Our study
provides additional knowledge in nutritional psychiatry
that long-term vegetarian diets are associated with lower
incidents of depression in the South Indian population. The
unique cultural and regional context of this study, and its
potential to unveil insights into a less-explored area, are the
cornerstones of its contribution to the broader discourse on
vegetarianism and cognition. It was conducted in a region
and among a demographic that, despite the prevalence of
vegetarian diets, lacks substantial research attention con-
cerning its specific impact on cognitive function.
Although our study has notable strengths such as a sub-
stantial sample size and the utilization of reliable assess-
ment tools, there are some limitations to consider. First, the
observational design of our study, which is cross-sectional
in nature, hinders our ability to establish causal relation-
ships between vegetarianism and cognitive performance.
Secondly, the reliance of our study on self-reported dietary
information may be subjected to recall bias. While our
study also highlights the positive effects of vegetarianism
on cognition and mood, it is essential to consider potential
confounding factors such as education level, socioeconomic
status, physical activity, and overall dietary quality which
may influence cognitive function and mood independently
of dietary choices due to lack of a controlled study design
and choice of population sampling. In this regard, controlled
longitudinal studies which observe changes in cognition and
neuropsychological status within individuals over time will
be more appropriate in the future investigations.
Conclusion
This study provides valuable insights into the effects of
vegetarianism on cognition and neuropsychological sta-
tus where vegetarians exhibited improved cognitive func-
tion and better mood scores compared to non-vegetarians.
These findings suggest that adopting a vegetarian diet may
be a viable strategy for promoting cognitive health and emo-
tional well-being. The consumption of fruits, vegetables, and
whole grains, common components of vegetarian diets, may
be linked to a reduced likelihood of experiencing depres-
sion and anxiety. Ultimately, our findings contribute to the
growing body of evidence supporting the potential benefits
of plant-based diets for overall brain health.
We also recommend that future research could incor-
porate objective measures, such as biomarkers or dietary
records, to obtain more accurate data on participants’ dietary
habits. Additionally, interventions and dietary counseling
programs could be developed to promote the adoption of
vegetarian diets and evaluate their effects on cognitive func-
tion and mental well-being.
Appendix
See Tables1, 2, 3, 4 and 5 here.
European Journal of Nutrition
Table 1 Summary of the sociodemographic characteristics of study
participants (n = 304)
Variable Frequency (%) N = 304
Age (in years)
40–49 113 (37.2%)
50–59 72 (23.7%)
60–69 58 (19.1%)
70–79 36 (11.8%)
80–89 25 (8.2%)
Gender
Female 166 (54.6%)
Male 138 (45.4%)
Family type
Extended 53 (17.4%)
Nuclear 250 (82.2%)
Stays alone 1 (0.3%)
Marital status
Married 269 (88.5%)
Widowed 29 (9.5%)
Single 5 (1.6%)
Divorced 1 (0.3%)
Education
University/college 61 (20.1%)
High school 179 (59.9%)
Elementary 55 (18.1%)
No formal education 9 (3%)
Occupation
Employed 99 (32.6%)
Retired 75 (24.7%)
Housewife 90 (29.6%)
Self-employed 37 (12.2%)
Unemployed 3 (1%)
Religion
Hindu 267 (87.8%)
Islam 7 (2.3%)
Christianity 30 (9.9%)
Atheist 0
Dietary pattern
Vegetarian 155 (51%)
Non-vegetarian 149 (49%)
Table 2 Individual nutrient composition comparison between veg-
etarians and non-vegetarians
* < 0.05 is significant
Energy and nutrients Dietary pattern p-value
Veg Non-veg
Mean ± SE Mean ± SE
Energy (Kcal) 2091.17 ± 44.71 2499 ± 64.10 < 0.001
Protein (g) 109.86 ± 1.76 104.74 ± 1.62 0.033
Carbohydrates (g) 293.64 ± 4.21 308.86 ± 4.61 0.015
Total fats (g) 95.08 ± 0.94 96.47 ± 1.14 0.347
Calcium (mg) 757.89 ± 10.67 614.32 ± 8.98 0.002
Sodium (mg) 3170.44 ± 53.93 3216.98 ± 56.61 0.552
Iron (mg) 14.92 ± 0.61 21.24 ± 0.53 0.001
Riboflavin (mg) 3.02 ± 0.06 3.26 ± 0.06 0.006
Folic acid (µg) 205.34 ± 5.04 172.57 ± 3.50 < 0.001
Vitamin B12 (µg) 2.26 ± 0.57 3.97 ± 0.08 < 0.001
Vitamin C (mg) 233.39 ± 5.72 164.61 ± 3.76 < 0.001
Table 3 Characterization of selected basic demographic details by
diet group
n: Selected number out of the main sample, N: Total sample of either
group
* < 0.05 is significant
Vegetarians Non-vegetarians p-value*
Mean ± SE Mean ± SE
N = 155 N = 149
Age (years) 42 0.11 53 0.09 < 0.001
Gender (M/F, n/n) 75/80 63/86 0.287
Attended university/
college (%)
44.0 15.9 < 0.001
Employed (n/N) 41/155 58/149 0.771
European Journal of Nutrition
Acknowledgements The authors express their gratitude for the assis-
tance and support provided by Indian Council of Cultural Research
(ICCR) and University of Hyderabad, an Institution of Eminence (IoE)
for all the logistical assistance and infrastructure facility to carry out
the study, and we extend our since acknowledgements to Ranga Reddy
community for participation in data collection. The study is part of
the thesis conducted in School of Medical Sciences, University of
Hyderabad in India.
Author contributions BKP helped in conceptualization of the study,
development of the study design, data collection and analysis, and
original draft preparation. MVL helped in study conceptualization,
methodology design, revision of data analysis, manuscript editing and
reviewing, and supervision. All authors were responsible for manu-
script revision and also gave their approval for the final manuscript
as submitted and have agreed to take responsibility for all aspects of
the work.
Funding This research received no specific grant from any funding
agency, commercial, or not-for-profit sectors.
Data availability The data supporting the findings of this study are
available from the corresponding author upon reasonable request. The
data cannot be accessed publicly due to specific limitations that could
compromise the confidentiality and privacy of the participants.
Declarations
Conflict of interest The authors have no competing interests to declare.
Table 4 MMSE and DASS
scores summary by diet group
* < 0.05 is significant
1 The normative scores for DASS-21 are: 0–9, 0–7, and 0–14 for depression, anxiety, and stress level,
respectively
1 Mild scores: 10–13, 8–9, and 15–18 for depression, anxiety, and stress level, respectively
1 Moderate scores: 14–20, 10–14, and 19–25 for depression, anxiety, and stress level, respectively
1 Severe scores: 21–27, 15–19, and 26–33 for depression, anxiety, and stress level, respectively
1 Extremely severe: 28 + , 20 + , and 34 + for depression, anxiety, and stress level, respectively
2 The normative score for MMSE is 26–30, mild score (20–25), moderate score (19–10), and severe (0–9)
Vegetarians Non-vegetarians p-value*
Mean ± SE Mean ± SE
N = 155 N = 149
DASS-21 total 22 ± 0.04 33 ± 0.06 0.000
Depression level110 ± 0.06 17 ± 0.07 < 0.001
Anxiety level14 ± 0.05 6 ± 0.07 0.005
Stress level18 ± 0.02 10 ± 0.05 0.007
MMSE score226 ± 0.04 24 ± 0.03 < 0.001
Table 5 Group correlation
analysis between mean
MMSE and DASS-21 scores
(depression, anxiety, and stress)
using Spearman’s correlation
(ρ)
* < 0.05 is significant
Diet MMSE score Depression Anxiety Stress
Veg
MMSE score Correlation coefficient 1
Depression Correlation coefficient −0.371 1
p-value 0.000*
Anxiety Correlation coefficient −0.027 0.147 1
p-value 0.734 0.068
Stress Correlation coefficient −0.105 0.003* 0.358 1
p-value 0.914 0.966 0.000*
Non-veg
MMSE score Correlation coefficient 1
Depression Correlation coefficient −0.059 1
p-value 0.478
Anxiety Correlation coefficient −0.131 0.227 1
p-value 0.111 0.005*
Stress Correlation coefficient −0.135 0.239 0.381 1
p-value 0.102 0.003* 0.000*
European Journal of Nutrition
Ethical approval This study was conducted according to the guidelines
laid down in the Declaration of Helsinki, and all procedures involv-
ing research study participants were approved by the University of
Hyderabad Institutional Ethics Committee (UH/IEC/2022/390) dated
November 30, 2022. Written informed consent was obtained from all
participants after explaining the study purpose and ensuring privacy
and confidentiality.
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