The longitudinal study, based on the CHNS, demonstrated a gradual increase in the cumulative incidence of the four chronic diseases over the five survey periods. Furthermore, it revealed that the incidence of new chronic disease cases was consistently higher in men than in women. The mean intake of almost all plant foods demonstrated significant time-varying trends, yet the magnitude of change in intake of different plant foods differed between men and women. The findings indicated that a high intake of vegetables and whole grains, along with moderate amounts of fruits, fungi and algae, could reduce the simultaneous risk of these four chronic diseases. Additionally, men could benefit from moderate refined grain consumption, while women should increase their intake of nuts and seeds. Furthermore, additional covariates, including physical activity level, sleep duration, annual income, body mass index, energy intake, educational level, smoking and drinking status, demonstrated time-varying characteristics. Sun and colleagues conducted a systematic review of 94 cohort studies from the Western Pacific region and identified a shift towards healthier dietary intake patterns over the past three decades24. This suggests that dietary covariates associated with lifestyle behaviors are not fixed24. When both food intake and covariates are time-varying in nature, feedback between food exposure and covariates occurs, which is the current food intake is influenced by past covariates and also the level of covariates in the next cycle. For example, people who consumed more refined grains in the past tended to have higher BMI values or energy intake levels, but subjects with higher BMI values or energy intake levels may adjust grains later in the study to lower or maintain their own BMI levels or energy intake levels25,26. Another example is that lower fruit intake may be associated with lower levels of income or lower levels of education and that an increase in subjects’ income level or education level over time may in turn increase fruit intake27,28. Similar Feedback may also exist with vegetables and exercise levels29, nuts and seeds, and hours of sleep30. Such Feedback exists when Conventional approaches for controlling time-varying confounders such as stratification, regression correction, and propensity score matching have been proven ineffective in managing time-varying confounders. Therefore, we used the new method RBW capable of handling this Feedback in combination with RCS to estimate the mean dose-response relationship between plant-based foods and chronic disease risk.
Existing research has predominantly focused on comparing plant-based diets with other dietary patterns or categorizing them along a continuum of intake or dietary index to conclude that higher consumption of plant-based foods is more beneficial to health. For instance, a systematic review and meta-analysis of 20 clinical trials revealed that individuals at high cardiovascular risk experienced slight but significant improvements in cardiometabolic health indicators after adopting a vegan diet31. Similarly, several studies have demonstrated that vegetarian diets lead to more substantial improvements in blood pressure reduction, weight loss, and glycemic control compared to omnivorous diets32,33,34. Additionally, a study involving 11,825 Spanish participants found that adherence to the Healthy Plant-Based Diet Index was significantly associated with a reduced risk of CVDs mortality35. However, these studies often did not specifically quantify the intake of plant-based foods, potentially overlooking critical information. For example, our study found that to reduce the risk of hypertension in women, fruit intake should be within the range of 188–295 g/day, rather than excessively high. Furthermore, a prospective cohort analysis involving 135,335 individuals aged 35 to 70 years from seven regions and 18 countries demonstrated that a higher total intake of fruits, vegetables, and legumes (measured in servings) was significantly and inversely associated with major cardiovascular events and all-cause mortality36. While that study quantified intake by servings, our research provided more detailed information on the intake of specific plant-based foods, thereby enhancing the precision and quantitative depth of the findings.
Our study diverges from existing findings by revealing that the relationship between plant-based food intake and chronic disease risk is predominantly non-linear. This non-linear relationship varies across different food groups, diseases, and genders. Specifically, the average intake of whole grains and vegetables demonstrated curvilinear inverse relationships with the risk of developing four chronic diseases in both genders. Notably, high levels of whole grains intake exhibited protective effects against hypertension and stroke in men and myocardial infarction in women. However, for other diseases, no significant protective effect was observed, but exceeding a certain level of whole grains intake did not increase disease risk. These findings align with previous research indicating that increased whole grains consumption reduces the risk of CVDs and diabetes37,38. The potential mechanisms underlying these protective effects include the high dietary fiber content in whole grain foods, which promotes satiety, delays gastric emptying, prolongs nutrient absorption, and modulates postprandial insulin and glucose responses39. These factors contribute to weight loss and the long-term maintenance of a healthy body weight, thereby reducing disease risk. Additionally, the digestive and viscosity properties of dietary fiber, along with its components such as arabinoxylan, inulin, pectin, bran, and resistant starch, play a significant role in improving human health40.
When vegetable intake is maintained at a high level, significant protective effects are observed against hypertension in men and all four chronic diseases in girls, without increasing the risk of stroke, myocardial infarction, and diabetes in men. Established studies corroborate these findings. For instance, Aune et al. synthesized data from 95 studies, revealing a negative association between fruits and vegetables consumption of up to 800 g per day and CVDs41. Similarly, Zhan et al. reported a significant reduction in CVDs risk when comparing the highest to the lowest levels of vegetables intake42. The protective benefits of vegetables may be attributed to their rich content of dietary bioactives, particularly polyphenols and carotenoids43. While carotenoids are often regarded as simple biomarkers of vegetable intake, they possess significant anti-inflammatory and antioxidant properties43. Additionally, vegetables are abundant in dietary fiber, which is known for its cholesterol-lowering effects. These mechanisms collectively provide robust support for the role of high vegetable intake in reducing the risk of chronic diseases.
The average intake of fruits, fungi and algae, nuts and seeds also showed similar negative associations with the risk of the four chronic diseases. This finding aligns with existing studies, for instance, Lukas et al. found that a daily intake of 100 g of fruit significantly reduces the risk of hypertension37. Additionally, a meta-analysis of 123 studies demonstrated that the highest compared to the lowest intake of fruits significantly decreases the risk of stroke7. Similarly, myocardial infarction44 and diabetes45 also benefited. The potential biological mechanisms underlying these benefits include increased antioxidant capacity46, anti-inflammatory effects47, prevention of platelet aggregation, and reduction of vascular tone48. Fungi and algae, rich in key nutrients and various health-promoting compounds, also show significant benefits in chronic diseases49,50. These foods are an important source of phenolic compounds, flavonoids, and polysaccharides50, which exhibit antioxidant, antimicrobial, and anti-inflammatory properties by scavenging and neutralizing free radicals. Consequently, they may combat many common diseases, including atherosclerosis, diabetes, and CVDs51,52.
Similarly, studies have demonstrated that a daily intake of 28 grams of nuts and seeds is associated with a 21% reduction in the risk of CVDs compared to no intake of nuts and seeds53. Nuts and seeds are a valuable source of protein, and it has been established that vegetarians consume plant proteins as a substitute for animal proteins to help mitigate their risk of developing chronic diseases such as diabetes and heart disease54. However, our findings also indicated a parabolic relationship between the average intake of fungi and algae and the risk of developing hypertension in men, as well as a parabolic relationship between the intake of fruits and the prevention of hypertension in women. This suggests that a higher intake of fungi and algae in men and fruits in women is not necessarily more beneficial in terms of hypertension. The existing studies, which are based on linear assumptions, for example, those of Borgi55, Kim et al.56, can only conclude that a higher intake is beneficial. The mechanism may be that fruits are high in fructose and that excessive intake may lead to higher blood uric acid levels57. It has been demonstrated that elevated blood uric acid levels constitute a risk factor for hypertension58. Furthermore, although fruits are typically rich in potassium, excessive fruits intake without an equivalent increase in sodium intake and an imbalance in the potassium-sodium ratio may impact blood pressure regulation59. Furthermore, although mycorrhizal foods are rich in a variety of bioactive compounds, the parabolic pattern of mycorrhiza and the risk of hypertension in men indicates the necessity for greater attention to be paid to dietary intake. Consequently, further in-depth studies are required in the future to determine the optimal level of intake.
Existing studies have concluded that refined grains are unhealthy and that they should be replaced completely with whole grains as much as possible26. Our study confirms these findings, showing a positive association between refined grain consumption and chronic disease incidence. However, our research also reveals nuanced gender-specific effects. For men, a low intake of refined grains was associated with a reduced risk of chronic diseases, or at least a stabilization of risk levels. In women, while a low intake of refined grains reduced the risk of diabetes, it did not offer protection against other chronic diseases. Nonetheless, the risk did not increase below a certain consumption threshold. Therefore, our study suggests maintaining a low intake of refined grains rather than complete elimination. It is important to note that entirely replacing refined grains with whole grains, without considering fortified grain products, could result in nutritional deficiencies60. The consumption of fortified refined grain foods can help mitigate these deficiencies61.
Given that current conclusions often broadly suggest that increased consumption of plant-based foods leads to health benefits, this generalized perspective may fall short in effectively guiding populations towards healthy eating. Considering dietary diversity and the relatively constant nature of individual daily energy intake, providing specific intake recommendations is essential. Based on dose-response relationships, we have developed a plant-based dietary pyramid tailored for different genders concerning four chronic diseases, aiming to offer practical dietary guidance. Moreover, most existing studies focus on a single chronic disease, while we have considered four, which often co-occur. Therefore, offering plant-based dietary recommendations that simultaneously prevent these four common chronic diseases holds practical significance. We found that intake levels of vegetables, fruits, whole grains, fungi and algae that meet or exceed recommended levels help to prevent the onset of these diseases collectively. Additionally, we suggested that men limit refined grains intake, while women could benefit from higher intakes of nuts and seeds. Individuals may choose to meet or exceed threshold levels based on personal preference. The Dietary Guidelines for Chinese Residents, published in 2016, recommend a daily intake of 300–500 g of vegetables, 200–350 g of fruits, 50–150 g of whole grains, and 25–35 g of nuts and seeds for adults62. Based on our findings, the rounded suggested cutoff values for effective prevention of chronic diseases were ~400–700 g of vegetables, 90–200 g of fruits for men, 90–300 g for women, 80–140 g of whole grains for men, 80–120 g for women, and 10–30 g of nuts and seeds for women. Except for the recommended vegetable intake, which is higher than the guidelines, the suggested intake levels for other plant-based foods fall within the ranges specified by the Dietary Guidelines for Chinese Residents.
Moreover, the current study reveals that the average intake of tubers and legumes exhibits varied dose-response associations with different chronic disease risks. Specifically, the consumption of tubers is inversely related to the risk of hypertension and diabetes, yet shows a positive association with stroke. Legume intake is negatively associated with hypertension, although its relationship with stroke, heart attack, and diabetes varies by gender. The effect of tubers on chronic diseases remains contentious. For instance, tubers are high in potassium, which is generally linked to a reduced risk of hypertension and stroke63. However, Larsson et al. found no association between tuber intake (specifically potatoes) and CVDs64, and other studies suggest that higher tuber consumption may increase hypertension risk63. Similarly, the current study reports inconsistent findings regarding legume intake65,66. Particularly premenopausal women may derive more benefit from tuber consumption due to the protective effects of estrogen against CVDs67,68. Furthermore, different methods of tuber preparation are associated with varying disease risks69. The diverse effects of legumes could be attributed to differences in genetic background, metabolic profiles, or digestive capacity, which may affect how legumes impact cardiovascular health. For example, certain individuals might be sensitive to specific legume components, leading to adverse reactions70,71. Consequently, further research is necessary to elucidate these complex relationships.
Our study has several strengths. Firstly, it addresses the assumption that food intake remains constant during long-term follow-up14 and challenges the notion of a linear relationship between dietary consumption and disease risk17, which is prevalent in current cohort studies investigating the association between plant-based foods and chronic diseases. Our study suggests that plant-based food intake can change significantly over time and that the mechanisms affecting chronic disease risk are complex and do not always follow a linear pattern. To address these issues, we used more appropriate statistical methods, such as RBW and RCS, to draw reliable real-world conclusions. Secondly, we used dose-response curves to determine feasible dietary guidance. Numerous studies have used medians or quartiles to categorize continuous food intake, concluding that consuming more of certain plant-based foods is healthier. However, the appropriateness of median or interquartile cutoffs is controversial72. Thus, our application of dose-response curves allows us to identify the optimal intake levels for specific foods. Thirdly, we extended our analysis to four common chronic diseases and constructed a chronic disease-specific plant-based food pyramid, finding that a diet rich in vegetables, whole grains, fruits, and fungi and algae reduced the risk of all four chronic diseases simultaneously. This finding provides more practical and comprehensive dietary advice for the general population. Fourthly, gender-specific dietary influences were addressed based on the identified gender differences in dietary preferences18 and in the etiology and incidence of chronic disease19,20,21. The new insights revealed that men can moderately incorporate refined grains into their diets, whereas women should increase their intake of nuts and seeds to reduce chronic disease risk. Fifthly, our study provides a more accurate identification of the dose-response relationship between specific plant-based foods and chronic disease risk, thereby addressing the limitations inherent in subjective dietary scoring systems, such as the Healthy Eating Index and Alternative Healthy Eating Index73, which tend to oversimplify complex dietary patterns and may overlook subtle variations and individual habits. Finally, we conducted a sensitivity analysis on the dose-response relationship using a dataset without imputed missing values. The results showed strong consistency between the datasets with and without imputation, with both displaying similar cutoff values overall.
This study has several limitations that require attention. Firstly, reliance on participants’ self-reported dietary data introduces potential recall bias, as individuals may inaccurately report their intake due to memory errors or social desirability bias, compromising data accuracy. Secondly, long-term cohort studies inevitably encounter the issue of participant turnover, which may potentially affect the representativeness of the sample and the generalizability of the findings. Thirdly, while we adjusted for a range of potential confounders—including health behaviors—it was not feasible to eliminate all unmeasured confounders. Factors such as food preparation methods and environmental contamination were inadequately addressed in our study. These uncontrolled confounders could have influenced observed associations, thereby constraining the interpretability of our results.
In summary, this long-term cohort study reveals that a higher intake of vegetables and whole grains, along with appropriate consumption of fruits, fungi and algae for both genders, significantly contributes to the prevention of four chronic diseases. Furthermore, it is recommended that men consume refined grains in moderation, while women should prioritize increasing their intake of nuts and seeds. These findings underscore the importance of personalized dietary guidance in optimizing health benefits and effectively preventing and managing chronic conditions. Future research should continue to investigate the impacts of these diets on different genders and health conditions to provide more precise nutritional guidance.
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