# Current Research on the Effects of Non-Digestible Carbohydrates on Metabolic Disease
## 5 NDCs and MDs
### Cvd  
Many clinical trials have found that a high intake of NDCs reduces the risk of CVD [20; 73; 74], which is the most common cause of mortality worldwide [4]. According to a systematic review and meta-analysis of 22 cohort studies, the association between CVD risk and NDC intake was dose-dependent (risk ratio 0.91 per 7 g/day). Moreover, [PERSON] et al. (2017) reviewed 31 meta-analyses and confirmed that NDC intake significantly reduced the relative risk (RR) of CVD mortality (RR = 0.77-0.83), the incidence of CVD (RR = 0.72-0.91), coronary heart disease (RR = 0.76-0.93), and stroke (RR = 0.83-0.93), which isparticularly noticeable with water-soluble, gel-forming NDCs, such as \(\beta\)-glucan and psyllium [20]. In particular, NDCs such as \(\beta\)-glucan and FOS have been shown to lower blood cholesterol because their viscous properties interfere with the absorption of cholesterol and bile acids in the intestine and reduce lipase activity [75]. Decreased reabsorption of bile acid leads to increased hepatic conversion of cholesterol into bile acid; as a result, more cholesterol stored in the body is used to produce bile acid [76]. NDCs also enhance digestive regularity by promoting rapid gastric emptying, decreasing intestinal transit time, and increasing fecal bulk [75]. Moreover, SCFAs suppress endotoxemia-induced inflammation by increasing tight junction gene expression, which reduces LPS translocation [77, 78].  
Rats fed a 32% FOS diet for 12 weeks showed significantly increased hypertrophy of cardiomyocytes through subcellular changes in cardiac metabolism and contractility, which could affect myocardial function and alter the risk of CVD [79]. In humans, intake of barley or oat \(\beta\)-glucan at 3-5 g/day for 3-5 weeks improves blood lipid profile and reduces CVD risk factors such as body mass index, waist circumference, blood pressure, LDL, and triglyceride levels [80, 81, 82]. Moreover, patients with non-diabetic CVD who consumed 12 g/day of FOS for 3 months had lower circulating levels of IL-6, a pro-inflammatory cytokine, and preserved endothelial function [83]. Non-dietary fiber NDCs, such as some types of resistant starch (RS), such as RS IV, have also been reported to have a preventive effect on CVD. Participants with several MD comorbidities who consumed a diet containing 30% RS4 for 4 weeks [84] and elderly patients with type 2 diabetes with a diet containing 53.7% fructose-free RS IV for 6 weeks [85] had improved dyslipidemia and cardiovascular risk biomarkers, including monocyte chemotactic protein-1 and soluble E-selectin.  
However, not all trials provide similar results. A cohort study of 31,036 women from the UK for 14.3 years reported that increased total NDC intake may not provide cardiovascular benefit in terms of mortality, but it may help to reduce the risk of fatal stroke in those without CVD risk factors such as hypertension and angina. A systematic review of 23 randomized controlled trials with 1513 participants also showed that there is no evidence of the effects of NDCs on CVD clinical events because the majority of studies were short-term, had a risk of bias, and insufficient information [86]. In addition, young healthy adults with an intake of extracted oat and barley \(\beta\)-glucans of 3.3 g/day for 3 weeks had no effect on cholesterol metabolism [87]. These results showed that the effects of NDC intake on the reduction of CVD risk are dependent on the type and source of fiber, doses, health condition, and sex of the participant, as well as the size and duration of the trial. To further understand the relationship between intake of NDCs and the reduction of CVD risk, studies focusing on the effect of NDCs on gut health and the biological networking of NDCS-related gut metabolites and other tissues are needed, although some studies have shown that gut microbiota profiles are affected by NDCs, and the metabolites they produce differ according to NDC type [39].