The Ups & Downs of Consuming Soy-based Foods on the Cognitive Abilities of Elderly Adults

Soy Foods are the Latest Health Trend but Do They Stand Up to their Hype

A Well-balanced Diet is the Best Way to Stay Healthy & Save Your Memory

A large population of the world comprises of senior citizens and WHO statistics show that this proportion of elderly population is all set to increase from 12% to 27% by 2050. Age is just a number and we don’t have definite characteristics associated with different age groups but WHO sets the start of 65 years as old age, the period between 65 and 74 y is early elderly and 75+ is considered to be late elderly. We all love to age gracefully with good health and healthy ageing is possible when we abide by consumption of nutrient-rich foods, daily activity, regular exercising and a stress-reduced lifestyle. Now that life expectancy is on the rise all that we must strive hard is to improve quality of life in the elderly population. Ageing brings with it an increased risk of chronic diseases, cognitive decline and decreased functional ability. We are aware that chronic diseases such as diabetes, heart disease and hypertension are widely due to the mistaken food choices. We now have research showing that cognitive dysfunction (a common neurodegenerative disease in the elderly population) is greatly impacted by dietary choices.
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Cognitive Impairment & Dementia
Alzheimer’s and Parkinson’s are more common than before and every year almost 10-15% of the elderly population with mild cognitive impairment (MCI) succumb to the fate of dementia making MCI a serious risk factor for dementia. Its been predicted that dementia would be the numero uno cause of disability in the elderly population worldwide. Such health problems do affect the quality of life of the elderly population debilitating their independent survival making them a prisoner to their life.

Refraining from adapting a diverse choice of dietary foods affects MCI and quality of life of older people. Soy is a nutrient that has gained popularity in recent times, especially in the Asian countries. Soy-based foods are rich in soy isoflavones and studies on their positive impact on osteoporosis, cardiovascular disease and neurodegeneration shows that soy could have a definite impact on improving cognitive function in menopausal women (this group has been using soy-based supplements for health benefits since quite a long time).

Impact of Soy-based Foods on Cognitive Function in Taiwan Citizens (NAHSIT Study)
Citizens above the age of 65 were included in the study whose dietary assessment that included a 24-bour dietary recall and a food frequency questionnaire (SFFQ) was taken. The questionnaire included intake and portion size of six major food groups including cereals, legumes/eggs/fish, meat, milk, vegetables, fruits and oils). Cognitive health was measured and quality of life (physical and mental health-related questions were given) was assessed. The total number of participants included 1,105 of which almost 85.6% of them consumed soy-based foods.

Age, gender and educational level are strong determinants for cognitive dysfunction while diet is a strong factor for procrastinating cognitive impairment. The study showed that soy-based foods had different effects on cognitive risk on different age groups and these seemed to reduce cognitive impairment from 65 to 80 years of age who had low education levels. We also have supporting evidences from a Japanese study that showed that Mediterranean diet helped in improving cognitive ability in elderly Japanese citizens and one important point to note here is that dietary soy is one of the characteristics of a Mediterranean diet. The present study showed that soy isoflavones improve cognitive function (mostly visual memory and summary cognitive function) by binding to an estrogen receptor. A decade back we had researchers quoting that estrogen decreased the risk of cognitive disorders thereby increasing quality of life. Cognitive impairment is negatively associated with consumption of soy-based foods and now that we know it is possible to make dietary recommendations based on the same.

Japanese Study
We have numerous studies done on the Western population and also the Mediterranean diet that includes higher intake of fruits, veggies, whole grains and olive oil suitable for cognitive health has been tried and tested upon Western populations. Research on non-Western populations are negligible. A study was conducted in Japan- a country whose dietary habits including consumption of rice, soybean products, fish, seaweed and green tea-whose eating habits are in startling contrast to those followed in Western countries.

635 elderly Japanese individuals participated in the study whose dietary patterns were analyzed using a self-administered questionnaire that probed into the frequency of consumption of certain foods, cooking methods used and the dietary behavior involved. Cognitive and functional status was assessed focusing on nine important cognitive domains namely attention, concentration, executive functions, memory, language, visuoconstructional skills, conceptual thinking, calculations and orientation using a Japanese version of the Montreal Cognitive Assessment (MoCA-J). Scores were between 0 and 30 with lower scores indicating lower cognitive functionality and higher scores showing higher cognition.

Age, sex, education levels, smoking habits, medical history of chronic disease, frequency of going outdoors, diabetes and blood pressure measurements were taken. Three dietary patterns were identified and named according to the food group that was prominently present:

Factor 1 (Plant foods and fish group): green and dark yellow vegetables, other veggies, soy products, mushrooms, seaweeds, potatoes, fruits, salad vegetables, fish, green tea and pickled vegetables. These individuals were mostly women who were highly educated, living in Western-rural areas, frequently visit outdoor places, less likely to smoke, drink or suffer from hypertension. This group was positively correlated with intake of protein, fat, polyunsaturated fatty acids (PUFA) and minerals.

Factor 2 (Rice and miso group): High positive loading for rice and miso soup with high negative loading for bread, oils, fats and ice creams. Individuals in this group were men, current smokers, likelier to drink alcohol, live in Western-rural areas, have low education, less frequent travelers and mostly suffer from diabetes. This group was positively correlated with intake of carbohydrates but negatively correlated with intake of fats, saturated fatty acids (SA), monounsaturated fatty acids (MUFA), PUFA and vitamins A, E and C.

Factor 3 (Animal foods): High positive loadings for seasoning, shellfish, chicken, red meats, fish, seafoods and processed meats. Individuals in this group were likelier to drink alcohol, suffer from hypertension and have a higher BMI. This group was positively correlated with intake of protein, fat, MUFA, PUFA, vitamins A, E, B6, and B12 and minerals but negatively correlated with carbohydrates.

While the ‘plant foods and fish group’ was positively associated with the MoCA-J score the ‘Rice and miso group’ was associated with a lower MoCA-J score. There was no association between the ‘Animal foods grou[‘ and the MoCA-J score. These associations were cross checked by running dietary patterns for women and men separately and once again by excluding 186 subjects who reported varied changes in diet for some reason or the other-all of them reported the same with respect to the MoCA-J score as previously found. Results show that Factor 1 is better associated with improved cognitive function in older Japanese men and women due to better MoCA-J score and this dietary pattern has similarities with the Mediterranean diet. This study and evidence from other studies clearly shows that a dietary pattern associated with a greater intake of vegetables, soy products, seaweed, fruits and fish with lower intake of rice, soft drinks and alcoholic beverages has the potential to preserve cognitive function in elderly Japanese individuals.

Tofu Consumption Inversely Related to Cognitive Performance in Elderly People in China
While we do have studies supporting the positive effect of soy foods on cognition there ae also an equal number of them which reject soy consumption. One typical example is the study on tofu consumption among the elderly population in China. The study included 517 participants who were asked to fill a food frequency questionnaire which contained questions on their consumption of foods such as breads, rice, juice, green vegetable, red/orange vegetables, meat, tofu and tempeh and the frequency of consumption was calculated on a weekly basis. Cognitive tests were done on all participants who were put into three different groups depending on their results-no cognitive impairment (NCI), MCI and dementia. Cognitive performance was measured between volunteers who ate tofu and those who did not.

Hopkins Verbal Learning Test (HVLT) was used to score cognitive abilities and in this study, higher intake of tofu was negatively associated with learning ability and immediate memory performance on HLVT. Also, in those individuals above 68 years of age a higher increase in tofu consumption was a potential risk factor for dementia risk. Similar results were observed in the Indonesia study where higher tofu intake was related to decreased memory skills. Also, being a meat-eater decreased the risk of dementia by four-folds but we do have studies that show that meat eaters were at a double risk of suffering from dementia. This contradiction might be because of the fact that meat contains saturated fats that’s a risk factor for cardiovascular disease and risk factors for CVD are also risk factors for dementia. Also, meat contains cobalamin which helps in reducing homocysteine levels.
Such contradictory results show that a moderation of different food intake is recommended for elderly population-one that contains little protein, tofu and meats and aplenty of fruits, vegetables and whole grains for well-being and health.

References
Soy-based foods are negatively associated with cognitive decline in Taiwan’s elderly: https://www.jstage.jst.go.jp/article/jnsv/64/5/64_335/_pdf/-char/en

Association between dietary pattern and cognitive function: https://nutritionj.biomedcentral.com/articles/10.1186/s12937-017-0273-2

Tofu intake associated with poor cognitive performance among elderly in China: https://www.researchgate.net/publication/264712315_Tofu_Intake_is_Associated_with_Poor_Cognitive_Performance_among_Community-Dwelling_Elderly_in_China
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Mitigating nutrition and health deficiencies in older adults: https://onlinelibrary.wiley.com/doi/pdf/10.1111/1750-3841.13674

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