European Journal of Cardiovascular Medicine

While food has traditionally been viewed as a source of energy and building blocks for the body, its role in disease prevention and protection is increasingly being recognized. Previous researches have provided strong evidence for the impact of dietary factors on specific molecular systems and mechanisms that support cognitive function [1].

Cognitive disorders affecting memory are becoming more prevalent worldwide[2]. Furthermore, diet-related pathological processes, such as atherosclerosis or inflammation, are increasingly affecting the brain and brainstem, leading to cognitive impairment [3].

Vegan and vegetarian diets promote cardiovascular health, leading to improved cerebral perfusion by optimizing lipid profiles, reducing blood pressure, and enhancing endothelial function, which is crucial for neurological well-being through sufficient oxygen and nutrient supply to the brain. A study correlate plant-based diets  with a 25% lower stroke risk, suggesting a link between the vascular benefits of vegan and vegetarian diets and cognitive health, particularly in reducing the risk of vascular cognitive impairment [4].

The Singapore Chinese Health Study found an inverse association between higher levels of the prevalent dietary inflammatory index (PDI), the plant‐based diet index (PDI), and the healthful plant‐based diet index (hPDI), and the risk of cognitive impairment. The highest levels of PDI and hPDI were associated with an 18% and 22% decrease in risk, respectively[5]. In a study involving 658 adults aged over 65 years, baseline assessments and a 2-year follow-up (n = 314) found no significant association between either healthful or unhealthful plant-based diet indices and cognitive function, nor were there any observed changes in cognitive function related to these diet indices[6]. Systematic reviews examining the relationship between vegan diets and depression yield inconsistent results, likely due to variations in the studies included, making it challenging to establish a causal link between the two[7]. A meta-analysis indicates a correlation between vegan diets and lower anxiety levels [8].  A 12-week intervention study on a raw vegan diet showed significant improvements in quality of life (11.5%), anxiety (18.6%), and perceived stress (16.4%)[9].

In a recent   Indian study Vegetarians displayed notably improved mood states in comparison to non-vegetarians, as evidenced by lower scores on the DASS subscales measuring depression, anxiety, and stress. Additionally, vegetarians showed enhanced cognitive performance relative to non-vegetarians, reflected in higher scores on the MMSE(Mini-mental state) [10].

Vegan and vegetarian diets, while beneficial, also present potential disadvantages that warrant consideration. A longitudinal study indicated that around 40% of vegans not taking B12 supplements showed early signs of neuropathy, highlighting the importance of supplementation [11]. Furthermore, the lower bioavailability of non-heme iron and zinc in vegan and vegetarian diets necessitates strategies like consuming vitamin C-rich foods to improve absorption[12].

While a few studies state that a balanced omnivorous diet, providing a wide array of nutrients, is typically linked to improved cognitive performance and enhanced brain health. Animal-sourced food supplementation, particularly meat and milk, has been shown to positively impact cognitive and behavioral development in children. Studies indicate improved exam scores, leadership skills, arithmetic performance, and overall behavior with meat supplementation, while milk supplementation also enhances exam scores. Furthermore, consumption of animal-sourced foods by infants and pregnant women is linked to enhanced language, motor, personal, and social skills in their children[13].

Early life malnutrition, especially during the first 1,000 days, can have irreversible negative effects, making this a crucial period for intervention. Research indicates that consuming animal-sourced foods during this time is linked to enhanced cognitive function and development later in life. Studies conducted in the UK, China, and Guatemala show that early meat consumption is associated with higher intelligence quotient scores, improved cognitive performance, and greater academic and economic success in adulthood. Moreover, the long-term cognitive benefits of animal-sourced foods in childhood may outweigh short-term effects, potentially leading to an underestimation of their impact in existing research[14].

Recent reports underscore the health risks tied to red meat consumption, associating it with cognitive decline. The studies highlight the negative impact of red meat on gut microbiome diversity and the generation of harmful metabolites, while advocating for plant-based diets as advantageous alternatives. Substituting red meat with healthier protein sources like nuts or legumes can reduce the risk of dementia and enhance overall health outcomes [15].

However, there are a number of contradictory results and the statistical power of some of these results is low due to the low number of participants, the short duration of the studies, and the diverse nutrient profiles [16,17]. Moreover limited studies are available defining the relationship of Indian dietary patterns with cognitive functions.

Furthermore, dietary habits have been linked to several cardiovascular and endocrine disorders [18]; however, the specific effects on cognition and neuropsychological status have received less attention, thus warranting further exploration and understanding. Hence, our study aims to fill this gap by identifying the impact of dietary habits on cognitive health and neuropsychological status of healthy young individuals under 40 years in India, to prevent the onset of cognitive impairment at an earlier stage, thereby promoting healthy aging, quality of life, and mental health at the population level.

Rapid urbanization and lifestyle changes, such as poor diets, sedentary lives, and high stress levels, have also raised the risk factors for depression and cognitive impairment in developing countries like India. Additionally, the current study focuses on a region where vegetarianism is deeply embedded in the local way of life and not just a dietary preference. Determining the relationship between Indian eating habits and cognitive function was the aim of the current investigation.

For the purpose of this study the independent variables are diet types over the past 6 months in 5 categories: Vegetarian, Non-Vegetarian, Vegetarian and Eggetarian, Omnivore. The dependent variable is Broadbent Cognitive Function (CFQ) [19].

This cross-sectional study was conducted in the Department of Physiology, of a premier institute of North India, from March 2023 to January 2024, the study commenced after obtaining approval from the Institutional Ethics Committee (Ref.No.SU/SMS&R/76-/2023/173)

The study is carried out as per international conference of Harmonization-Good Clinical

Practices Guidelines (ICH-GCP) or as per ICMR National Ethical Guidelines for Biomedical and Health Research Involving Human Participants. Men and women between the ages of 16 and 49 were included.  Participants who were diagnosed with dementia or any other condition that could affect cognitive function (e.g., stroke, traumatic head injury, neurological or psychiatric condition), or who were taking medication that could affect their cognitive function, were excluded from the study. Additionally, any events in the past 2 years that had a significant effect on dietary intake or cognitive function, such as a family member's death or illness, were also excluded [20].

For a statistically significant correlation between a product and a moment (Pearson product- moment) with a p-value of 0.05, a power of 0.80 and a mean effect size of study calculated was 120.

Measures:

Broadbent cognitive failures questionnaire (CFQ)

The primary measures used in the study is the Broadbent Cognitive Failures Questionnaire (CFQ) [19].

Broadbent Cognitive Failures Questionnaire (CFQ)

The Broadbent Cognitive Failures Questionnaire (CFQ), standard form, was used to measure memory performance. Participants were given questions related to minor mistakes in the past 6 months which everyone makes from time to time, but some of which happen more often than others.

A questionnaire to measure how often people experience cognitive errors, such as forgetting things, in their day-to-day lives -- slips and misfortunes in seeing, remembering, and using their motor skills. The easiest way to calculate the scale is to summarize the ratings of each of the 25 items, which results in a score of 0-100. Higher score indicate a better memory performance.

Questions related to diet

Participants were classified into a category if their eating habits did not change for a minimum of 6 months.

Respondents were classified as 'vegan' if they self-reported as such and said they did not consume meat, dairy or seafood. Participants in the 'vegetarian' category were those who said they were vegetarian and did not consume meat or seafood. Respondents in the 'non vegetarian' category reported they ate meat and fish. Participants in 'omnivore' included those who said they ate both vegetarian and eggetarian food as well as non-vegetarian food with dairy products[21].

Data collection

Once the participant had given their informed consent and

they had been instructed to focus to the best of their ability, the experimenter began the questionnaire booklet.

Statistical Analysis

The analysis was conducted using Microsoft Excel data analysis tool. The main hypothesis regarding the impact of dietary on memory was evaluated using an ANOVA and post hoc test with the dietary group as an independent variable and memory score as a dependent variable.

All participants aged between 16 and 49 years. A total of 121 individuals took part, comprising 47 males and 74 females. Individuals were assigned to one of the five diet groups illustrated in table 1 based on a dietary questionnaire.

Table 2 shows the mean cognitive /memory score for each diet group. The statistical analysis confirmed that there was no-significant effect of diet on the cognitive functions.

This exploratory study revealed no notable differences in cognitive functions between different diet groups. The reasons for the results may be due to the small sample size and the presence of confounders like genetic, environmental, and social factors that may have diminished the significance of the independent variables of different diet types, as well as the fact that subjects were divided into groups based on their dietary habits over the previous six months. As a result, it is advised to conduct research on a large population without confounders following long-term dietary pattern.

The research on vegans has been limited due to the fact that the vegan population is a minority among the population of India with an estimated 9% of the population following a vegan lifestyle[22]. Previous study findings[23,24] shows that vegetarians are at a low risk of cognitive function. Vegetarian and vegan diets help reduce inflammation because they avoid meat, which contains substances that can cause oxidative stress and increase inflammation [25].  Moreover, vegetarian diets are typically rich in vitamins C and E, which are powerful antioxidants that help neutralize free radicals in the body. A greater intake of dietary fiber, polyunsaturated fats, vitamin C, and bioactive molecules, along with a lower intake of saturated fats, acts directly or indirectly (through other diseases) to reduce inflammation in vegetarians compared to non-vegetarians[26].

Vegan diets, characterized by lower protein, total fat, and saturated fat intake but higher carbohydrate and fiber consumption compared to omnivorous diets, significantly impact the gut microbiota [27]. A potential mechanism for the mood-boosting effects of a vegan diet lies in quercetin, a plant-derived compound that inhibits monoamine oxidase (MAO), increasing levels of mood-regulating neurotransmitters like serotonin, dopamine, and norepinephrine. Beyond its antidepressant properties, quercetin exhibits neuroprotective effects, improving cognitive performance, inhibiting Aβ aggregation and tauopathy, reducing oxidative stress and inflammation, and stimulating neurogenesis through increased BNDF/TrkB signaling (Brain-derived neurotrophic factor (BDNF)/tropomyosin-related kinase receptor type B[28].

In contrast few studies report that vegetarian diet may deteriorate  cognitive functions as  secondary metabolites produced by plants , including tannins, alkaloids, glucosinolates, phytates, and lectins, vital for plant defense,  functions as antinutrients in the human diet by interfering with nutrient absorption, can  diminish the nutritional value of plant-based foods. Tannins reduce protein digestibility by binding to proteins and enzymes, while phytates limit the bioavailability [29] of essential minerals like iron, zinc, and calcium through chelation Oxalates are increasingly implicated in neurotoxicity due to their ability to form deposits in neural tissues and induce oxidative stress. These mechanisms can disrupt cellular structure, impair mitochondrial function, and ultimately contribute to neural damage [30].

According to studies the traditional domestic processing of meat i.e. cooking, frying, and baking requires higher temperatures and longer heating times in comparison to vegetables. As a result protein glycation products also called advanced glycation end products (AGE) are formed during the heat treatment of foods. Although kidney plays a key role in the disposal of AGEs. In general, about 10 % is consistently absorbed, while only 30 % of this is excreted in the urine. Due to their toxic effects, AGEs are considered as a new class of uremic toxins, but they are also of pathophysiological relevance in other diseases like neurological dysfunctions [31]. Processed meat, in particular, has heme iron and other compounds that promote harmful lipid oxidation and a proinflammatory environment[25]. Arachidonic acid, primarily found in animal products, increases inflammation and may contribute to feelings of anxiety, stress, and depression[32].

In conclusion, present study found that no significant difference in participants with plant based diets compared to participants with animal-based diets in terms of in cognitive performance. Further research is required to completely comprehend the precise effects of dietary habits on various cognitive domains and across various populations. Hence a more extensive study with a larger sample size would be beneficial in resolving the scientific uncertainties surrounding the relationship between diet and memory and other neurological mechanisms.

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