Replacing dietary low-quality carbohydrates with protein or fat from animal foods may reduce the risk of cognitive decline in older Chinese adults

Dementia is a common disease among the elderly, and by 2050, it is estimated that 139 million people worldwide will suffer from dementia. Since there are currently no clinical drugs to treat dementia, it is important to identify lifestyle or dietary factors that can delay or reverse cognitive decline. Carbohydrates, fats, and proteins are the three major macronutrients that provide energy to the human body. However, previous studies have not fully explored the relationship between dietary carbohydrates and cognitive function, especially the effects of dietary carbohydrates from different food sources (high quality and low quality) on cognitive function. In addition, the ketogenic diet pattern characterized by low carbohydrate and high fat intake is considered to be beneficial to the cognitive function of patients with dementia, but the effect of this dietary pattern on cognitive function in the general population is still unclear.

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In response to the above problems, the National Clinical Research Center for Kidney Diseases of Nanfang Hospital of Southern Medical University and the School of Public Health of Anhui Medical University jointly carried out relevant research work, and the results were recently published in the journal Clinical Nutrition. **The study found that the intake of low-quality carbohydrates, rather than high-quality carbohydrates, in the diet is associated with a rapid decline in cognitive function in the elderly; replacing low-quality dietary carbohydrates with protein or fat from animal food sources rather than plant food sources will reverse or delay this accelerated decline in cognitive function. **Professor Qin Xianhui of the National Clinical Research Center for Kidney Diseases of Nanfang Hospital of Southern Medical University is the corresponding author of the paper, and Liu Chengzhang of the School of Public Health of Anhui Medical University is the first author.

This study is a prospective cohort study based on the China Health and Nutrition Survey (CHNS) project. A total of 3106 participants aged 55 years and above who underwent at least two cognitive function assessments were included, with a median follow-up time of 5.9 years. The intake of various foods was assessed using a 3-day 24-hour dietary recall and household food inventory weighing method. High-quality carbohydrate food sources include whole grains, fruits, beans, and non-starchy vegetables, and low-quality carbohydrate food sources include refined grains, starchy vegetables, sugars, and juices. The Chinese Food Composition Table was used to calculate the intake of carbohydrates and various nutrients. The study outcomes were the 5-year decline rate of total cognitive scores and standardized cognitive scores.

First, this study found that the rate of decline in cognitive scores was positively correlated with low-quality dietary carbohydrate intake, but had no significant association with high-quality dietary carbohydrate intake (Figure 1).

Figure 1. Relationship between dietary total (A, D), low-quality (B, E), and high-quality (C, F) carbohydrates and the 5-year decline in total cognitive scores (AC) and standardized cognitive scores (DF)

Further energy replacement analysis revealed that replacing low-quality carbohydrates with equal-energy animal-based fats or proteins was negatively correlated with the rate of cognitive decline, while replacing low-quality carbohydrates with equal-energy plant-based fats or proteins was not significantly associated with the rate of cognitive decline (Figure 2).

Figure 2. Relationship between replacement of dietary low-quality carbohydrates with equal energy fat or protein and rate of cognitive decline

This study shows that low-quality carbohydrates, rather than high-quality carbohydrates, are associated with a more rapid decline in cognitive ability in the elderly. Replacing low-quality dietary carbohydrates with protein or fat from animal foods rather than plant foods will reverse or slow this accelerated decline in cognitive function. Therefore, the elderly should choose high-quality carbohydrate foods for their three meals a day and avoid consuming too much low-quality carbohydrates. At the same time, they should also ensure that they consume an appropriate amount of animal foods. In short, this study emphasizes the importance of paying attention to dietary quality and combining meat and vegetable diets to prevent cognitive decline.

The increasing burden of dementia is a major public health problem faced by the world. In daily life, changing or optimizing dietary behavior to control or delay cognitive decline may be a simple and easy health strategy to prevent cognitive decline.

Information Points

1. Classification of high-quality carbohydrate sources:

① Whole grains: wheat, barley, millet, millet flour, sorghum rice, corn, corn flour, black rice, etc.

② Fruits: Any fresh, canned, frozen or dried fruit, including whole, cut or juiced types.

③ Beans: tofu or other soy products.

④ Non-starchy vegetables: soybeans, peas, kale, spinach, cauliflower, cucumbers, peppers, onions, tomatoes, asparagus, carrots, sweet potatoes, pumpkins, winter melons, bamboo shoots, etc.

2. Classification of low-quality carbohydrate sources:

① Fine grains: refined white flour, refined rice, white steamed buns, white bread, white noodles, etc.

② Starchy vegetables: potatoes, cassava, raw corn, taro, yam, lotus root, water chestnuts, immature green beans, etc.

③ Added sugar: sugar, candy, sugary drinks, candied fruits, desserts, cakes, etc.

④ 100% juice: 100% orange juice, apple juice, mixed juice, or 100% other juice, etc.

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References:

Liu, C., Meng, Q., Zu, C., Wei, Y., Su, X., Zhang, Y., He, P., Zhou, C., Liu, M., Ye, Z., & Qin, X. (2023). Dietary low- and high-quality carbohydrate intake and cognitive decline: A prospective cohort study in older adults. Clinical nutrition, 42(8), 1322–1329.

Editor | Liu Chengzhang Wu Yiting

Audit | Qin Xianhui