Association between dietary fiber intake and atherosclerotic cardiovascular disease risk in adults: a cross-sectional study of 14,947 population based on the National Health and Nutrition Examination Surveys

Cardiovascular diseases (CVD), the world’s leading cause of death, are a group of disorders of the heart and blood vessels, including coronary heart disease, cerebrovascular disease, rheumatic heart disease and other diseases, claiming an estimated 17.9 million lives each year [1, 2]. CVD presents a heavy burden for the world due to its high treatment cost and extensive preventive interventions [3, 4]. Evidence demonstrated that the occurrence of most CVD can be attributed to a series of factors, such as smoking, obesity, diabetes, dyslipidemia, hypertension, diet, excessive alcohol consumption, and mental state [5, 6]. Early prevention can effectively reduce the incidence of CVD, but CVD-related deaths still account for a large proportion of all-cause deaths.

Dietary fiber can affect the cardiometabolic pathways, improve lipid or lipoprotein metabolism, insulin homeostasis, and so on [7]. Epidemiologic studies have shown that dietary fiber intake is associated with the CVD risk in short and medium-term follow-up [8‐10]. Murai et al. indicated that seaweed intake was inversely associated with the risk of ischemic heart disease [8]. Song et al. found that total fruit and whole fruit intake were inversely related to cardiovascular risk factors such as obesity, metabolic syndrome and hypertension [9]. Wang et al. showed that higher fiber intake and fiber intake density may be associated with a lower risk of major adverse cardiovascular events [10]. An in-depth understanding of the role of dietary fiber intake in predicting the long-term CVD risk can help the public identify optimal dietary patterns and improve long-term survival. The atherosclerotic cardiovascular disease (ASCVD) score, recommended by the American College of Cardiology (ACC) and American Heart Association (AHA), is a commonly and widely used to evaluate the 10-year CVD [11]. In this study, we applied this score to identify people at high risk of CVD over the next ten years and assessed the association between dietary fiber intake and the CVD risk based on the National Health and Nutrition Examination Survey (NHANES) database.

In this study, we analyzed the association between dietary fiber density and total dietary fiber and long-term CVD risk in different ASCVD risk groups based on a large sample from the NHANES database. Our results found that both higher dietary fiber density and total dietary fiber were associated with a reduced long-term ASCVD risk in the intermediate-risk and high-risk groups. Subgroup analyses showed that higher dietary fiber density was still related to a reduced ASCVD risk in intermediate-risk and high-risk participants aged 20–39 and 40–59, as well as in high-risk male and female participants.

Dietary fiber has been shown to have multiple health benefits, but the average daily intake for most Americans is 15 g/day, which is below the recommended amount [12]. According to the results of epidemiological studies on the protective effect of dietary fiber intake, the recommended dietary reference intake of dietary fiber is 14 g/1000 kcal [13]. Our results showed that higher dietary fiber density and total dietary fiber intake were associated with a lower long-term CVD risk. Previous studies have focused on the association between dietary fiber intake and short-term and medium-term CVD risk [8‐10], while our results provided the relationship between dietary fiber density and total dietary fiber intake and long-term CVD risk. Numerous studies suggested that total dietary fiber was inversely related to the risk of weight gain [14], coronary heart disease [15], high blood pressure [16], and CVD death [17]. Several biological mechanisms may explain the association between higher dietary fiber intake and lower CVD risk. First, dietary fiber may reduce the CVD risk by reducing the coagulation activity of type 1 plasminogen activator inhibitor and coagulation factor VII [18, 19]. Second, higher dietary fiber intake may be related to lower inflammatory response. Several studies have reported that higher dietary fiber intake can reduce the levels of inflammatory markers such as C-reactive protein [20, 21]. Third, the protective effect of dietary fiber on CVD may be associated with metabolic diseases, that is, dietary fiber may regulate the intestinal microbiota, which plays an important role in the development of metabolic diseases such as atherosclerosis, obesity and type 2 diabetes [22‐24].

Our results found that higher dietary fiber density was significantly associated with a lower CVD risk in participants aged 20–39 and 40–59. The possible explanation was that the relationship between high dietary fiber intake and low CVD risk was related to the general health of the population, the absorption of fiber, and the incidence of obesity. Edwards et al. demonstrated that young people in many countries had insufficient intake of dietary fiber [25]. Yamada et al. indicated that adults aged 30–40 had a rapid increase in BMI [26]. These may be due to the fact that the consumption of a large number of refined carbohydrates, lipids, and low dietary fiber foods was conducive to weight gain [27‐29]. In addition, dietary fiber has been used for the prevention and treatment of obesity [30, 31]. Studies have shown that obesity is an important risk factor for CVD [32, 33]. The type and absorption of dietary fiber may also affect the CVD risk. McKeown et al. demonstrated that cereal fiber intake was associated with a reduction in the prevalence of metabolic syndrome, but not with total fiber and fruit fiber intake [34]. Mirmiran et al. found that the intake of different types of dietary fiber was related to a reduced CVD risk, especially soluble dietary fiber [35]. Our results may also indicate that the earlier intake of high dietary fiber, the better the protection against CVD.

Some strengths were presented in this study, we analyzed the impact of dietary fiber density and total dietary fiber on long-term CVD risk in different risk groups based on ASCVD. Dietary fiber density considered the factor of energy, which can better reflect the overall situation of individual dietary fiber in daily diet. Therefore, further analysis was performed to explore the relationship between dietary fiber density and ASCVD risk in age and gender subgroups. However, this study had some limitations. First, the effect of insoluble and soluble fiber intake on CVD risk could not be analyzed because of the lack of data. Second, we did not analyze the effect of different dietary fiber intake doses on CVD risk. Third, a dietary fiber intake of 14 g/1000 kcal had a better protective effect [12, 13], while the median dietary fiber intake of our study population was 7.81 g/1000 kcal, which may reduce the accuracy of our results. Fourth, some variables related to CVD, such as genetic factors could not be analyzed due to the database limitations. Fifth, mental state and sleep duration were associated with CVD risk [36, 37], but we did not analyze the effects of these variables, which may be potentially confounding.

Higher dietary fiber density and total dietary fiber were associated with a lower long-term CVD risk. Higher dietary fiber density was most significantly related to a lower ASCVD risk in people aged 20–39 and 40–59. Young people may benefit more from a high intake of dietary fiber to protect against CVD.