Consumption of vegetables and fruits reduces the risk of cognitive impairment,  as confirmed by studies conducted in the USA, China, Australia, and the Netherlands. The World Health Organization also recommends including 400 grams of fruits and vegetables in your daily diet.

Japanese scientists from the University of Kyushu evaluated the quantitative impact of only vegetables and only fruits on reducing the risk of dementia in Asians in old age. The researchers also found which nutrients in these foods help reduce the risk of dementia.

Research Results

The risk of developing Alzheimer’s disease was 31% lower in the participants consuming the most vegetables than in the group consuming the least vegetables. The best results were in people who consumed 350-400 grams of vegetables daily.

For fruits, there was no similar statistically significant relationship.

These results are presented in the figure below where:

  • histogram “A” – for vegetables;
  • histogram “B” – for fruits;
  • Columns – an equal number of groups of participants who have a similar share of vegetables/fruits in the diet in terms of 1000 kilocalories (the more to the right of the column, the higher the percentage);
  • vertical axis – the risk of Alzheimer’s disease, adjusted for age, gender, smoking and alcohol consumption status, physical activity, blood chemistry, and medical history.

Image source: https://bmcgeriatr.biomedcentral.com/articles/10.1186/s12877-022-02939-2

Based on the data obtained, the scientists quantified the dependence of the risk of Alzheimer’s disease on the absolute amount of fruits and vegetables consumed per day.

The charts are shown below where:

  • graphics “A” – for vegetables;
  • graphs “B” – for fruits;
  • horizontal axis – the number of grams of vegetables or fruits consumed per day;
  • vertical axis – the risk of developing dementia;
  • The solid graph is the risk, and the dotted chart is the 95% confidence interval for that risk.

Image source: https://bmcgeriatr.biomedcentral.com/articles/10.1186/s12877-022-02939-2

The researchers note that eating fruits and vegetables slightly reduces the risk of dementia, but without statistical significance.

What Nutrients Help Reduce The Risk of Dementia

Scientists assessed the contribution of individual nutrients found in vegetables and fruits to the development of dementia. The risk of general dementia was less with a high intake of vitamins A and C, riboflavin, magnesium, calcium, and potassium.

The risk of dementia of different subtypes differed depending on the type of nutrients:

  • Alzheimer’s disease is less susceptible to people who consume much riboflavin;
  • vascular dementia – consuming a lot of vitamins A and C, riboflavin, and calcium.

Researchers note that soluble and insoluble dietary fiber also reduces the risk of dementia. However, this trend does not reach statistical significance.

Study Design

The study was conducted for 24 years: from 1988 to 2012. The number of participants is 1071 people: 452 men and 619 women. All participants were over 60 years of age, and none had dementia at the start of the study.

Scientists have observed how often the elderly, depending on their diet, develop dementia and its subtypes: Alzheimer’s and vascular dementia.

All participants completed a questionnaire on the amount of fruit and vegetables consumed. To assess the contribution of nutrients, all vegetables were divided into two groups: green (cabbage, onion, cucumber, spinach) and yellow-red (tomatoes, peppers, carrots).

All participants underwent annual medical examinations, including MRI and computed tomography of the brain.

Four times during the entire study period, participants underwent comprehensive examinations of cognitive functions: neuropsychological tests, assessment of dementia according to the expanded Hasegawa scale, and review of mental state.

In addition, daily monitoring of events related to the brain was carried out – stroke, manifestations of cognitive impairment, and symptoms of dementia.

Psychiatrists and neurologists established the diagnosis of dementia and its subtype.

Conclusions

The risk of dementia in the elderly decreases with an increase in the daily intake of vegetables from 270 to 400 grams. However, there was no statistically significant benefit of fruit for preventing dementia. However, eating vegetables and fruits together was slightly more likely to reduce the risk of dementia than eating vegetables alone.

The most beneficial nutrients that reduce the risk of dementia are vitamins A and C, riboflavin, magnesium, calcium, and potassium. However, no similar statistically significant relationship was found for dietary fiber, soluble and insoluble dietary fiber.

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Reference

Long-term association of vegetable and fruit intake with risk of dementia in Japanese older adults: the Hisayama study

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