1. Introduction
In the 21st century, cancer incidence and mortality has not reduced; moreover, it has even increased year by year. The total number of patients with colorectal cancer increased to 1.23 million globally in 2008; it is ranked third in cancer incidence and fourth in mortality [
1]. However, the incidence and mortality of colorectal cancer were ranked third and fifth, respectively [
2] in China. Many studies showed that the incidence of malnutrition in patients with a malignant tumor was as high as 31%–97% [
3,
4], especially for gastrointestinal cancer, so choosing a proper nutrition therapy for colorectal cancer patients with malnutrition is necessary. Early enteral nutrition support is promoted after gastrointestinal surgery, and there are many kinds of nutrient elements, such as probiotics, ω-3PUFA, Gln and fiber. We know that dietary fiber is a kind of nutrient, which is divided into soluble dietary fiber and insoluble dietary fiber and can protect the intestinal barrier, modulate immune function, induce inflammatory response and postoperative complications [
5,
6]. SCFA is the main source of energy for intestinal epithelial cells and plays a key role in maintaining colonic health and moderating cell growth and differentiation. This depends on the fermentation of dietary fiber. Soluble dietary fiber is fermented, but insoluble dietary fiber is difficult to ferment. The relationship between dietary fiber and colon cancer prevention was studied widely, but there is little study about the early postoperative application of soluble dietary fiber in colon cancer [
7,
8,
9]. Thus, we decide to add soluble dietary fiber to verify the feasibility and potential benefit of SDFEN for colon cancer for the postoperative course.
4. Discussion
Colon cancer is a common gastrointestinal malignancy, the incidence of which has increased year by year. Seventy percent of patients with GI cancer may be suffering from malnutrition and 39.3% of patients with colon cancer had different degrees of malnutrition [
11,
12]. Surgery is still the first choice for treatment, but surgical trauma and anesthesia can cause body metabolic disorder and aggravated malnutrition. Widespread attention has been given on how to further improve the postoperative nutritional status and the prognosis.
Early enteral nutrition began at 24 h after surgery in our study. ASPEN [
13] suggested that ideal enteral nutrition should begin within 24 to 48 h after surgery. Actually, intestine had recovered its absorption function and EMG activity within 4 to 8 h after surgery [
14]. The gastrointestinal tract can not only absorb nutrients, but also plays an important role in immunity because it is a central organ after surgical stress [
15] and it is also the motor of the MODS. Intestine mucosal atrophy and abnormal intestinal permeability can occur after not eating for several days. Early enteral nutrition is more close to the human physiological needs. The application of enteral nutrition can reverse the loss of gut mucosal integrity resulting from surgical trauma [
16], and early enteral nutrition support is associated with a decreased infection risk, a reduced hospital stay, and a clear trend of a reduction in anastomotic breakdown [
17,
18]. Therefore, it could be the first choice for patients who have had an operation.
Some studies proposed that early application of soluble dietary fiber enteral nutrition could increase nutritional indicators, make patients’ weight decline slowly and reduce the incidence of digestive tract complications [
19,
20]. However, there was no obvious difference in post-operative nutrition status and complication between the SDFEN group and EN group in our study. Fortunately, there was a trend of an increased post-operative nutrition status and declined incidence of complications. Dietary fiber are not a static collection of indigestible plant materials that pass through the human GI tract without any function; instead, they bind potential nutrients, result in new metabolites, and modulate nutrient absorption/metabolism, and they can promote the growth of the small intestinal villus to increase the absorption of nutrients to improve nutrition status. Dietary fiber is divided into soluble dietary fiber and insoluble dietary fiber. In general, soluble dietary fiber is fermented, but insoluble dietary fiber is difficult to ferment. Studies found that dietary fiber could be fermented into SCFAs in colon and unoxidized SCFA through the portal system into the liver. They can thus be converted to glutamine, and then glutamine enters into the circulation of blood to nourish the small intestine [
21]. Therefore, statistical differences in post-operative nutrition status and complication will exist between the SDFEN group and EN group, if observation time is enough.
A large amount of research has reported that soluble dietary fiber had health benefits with immunomodulatory and anti-inflammatory effects [
8,
22]. In our study, there were significant differences in the indicators of immune conditions including deviations in CD4+, IgA and IgG at seven days between the SDFEN group and EN group (35.90% ± 2.24% vs. 34.41% ± 2.64%, 2.25% ± 0.79 g/L vs. 1.88 ± 0.54 g/L, and 11.55 ± 1.44 g/L vs. 11.41 ± 1.32 g/L, respectively,
p < 0.05), and the levels of TNF-α and IL-6 in the SDFEN group was lower than those in the EN group (13.02 ± 2.85 pg/mL vs. 14.73 ± 4.07 pg/mL, and 58.75 ± 24.82 pg/mL vs. 70.83 ± 35.65 pg/mL, respectively,
p < 0.05). These health benefits can be attributed to the fermentation of soluble dietary fiber into SCFAs in the colon. The three major colonic SCFAs are acetate, propionate and butyrate, which is the main source of energy for intestinal epithelial cells and plays a key role in maintaining colonic health and moderating cell growth and differentiation [
23]. Acetate plays a role in the host immune system through interacting with the G protein-coupled receptor (GPCR43, 41) in immune cells [
24]. Butyrate exhibits strong anti-inflammatory properties, and this effect is likely mediated by inhibition of TNF-α production, NF-κB activation, and IL-8, IL-10, and IL-12 expression in immune and colonic epithelial cells [
25,
26]. Leukocytes are recruited and migrate from the bloodstream to the inflamed tissue through a multistep process that involves expression and activation of several proteins such as adhesion molecules and chemokines, and SCFAs modify this leukocyte recruitment [
27,
28] by modulating the amount or type of adhesion molecules and chemokines. SCFAs may alter the recruitment of leukocytes to reduce the chronic GI tract inflammatory response. Therefore, intakes of dietary fiber can reduce inflammatory reaction and improve the postoperative immune function.
Under the stimulation of mixed dietary fiber food, the gastrointestinal hormone is increased, such as gastrin and cholecystokinin, which can promote recovery of intestinal movement. Furthermore, SCFAs also have the same function; Kamath et al. [
29] found that the movement of the free small bowel was increased after being stimulated with SCFAs. In our study, patients in the SDFEN group had a significantly shorter first flatus time than the EN group (58.93 ± 6.5 h vs. 63.03 ± 4.8 h,
p < 0.05), so that SDFEN can promote recovery of intestinal movement.