Effects of immune-enhancing diets on infectious morbidity and multiple organ failure

Perioperative Nutritional Support: A Review of Current Literature

Since the beginning of the practice of surgery, the reduction of postoperative complications and early recovery have been two of the fundamental pillars that have driven the improvement of surgical techniques and perioperative management. Despite great advances in these fields, the rationalization of antibiotic prophylaxis, and other important innovations, postoperative recovery (especially in elderly patients, oncological pathology or digestive or head and neck surgery) is tortuous. This can be explained by several reasons, among which, malnutrition has a major role. Perioperative nutritional support, included within the ERAS (Enhanced Recovery After Surgery) protocol, has proven to be a main element and a critical step to achieve better surgical results. Starting with the preoperative nutritional assessment and treatment in elective surgery, we can improve nutritional status using oral supplements and immunomodulatory formulas. If we add early nutritional support in the postoperative scenario, we are able to significantly reduce infectious complications, need for intensive care unit (ICU) and hospital stay, costs, and mortality. Throughout this review, we will review the latest developments and the available literature.

The role of NIGMS P50 sponsored team science in our understanding of multiple organ failure

The history of the National Institute of General Medical Sciences (NIGMS) Research Centers in Peri-operative Sciences (RCIPS) is the history of clinical, translational, and basic science research into the etiology and treatment of posttraumatic multiple organ failure (MOF). Born out of the activism of trauma and burn surgeons after the Viet Nam War, the P50 trauma research centers have been a nidus of research advances in the field and the training of future academic physician-scientists in the fields of trauma, burns, sepsis, and critical illness. For over 40 years, research conducted under the aegis of this funding program has led to numerous contributions at both the bedside and at the bench. In fact, it has been this requirement for team science with a clinician-scientist working closely with basic scientists from multiple disciplines that has led the RCIPS to its unrivaled success in the field. This review will briefly highlight some of the major accomplishments of the RCIPS program since its inception, how they have both led and evolved as the field moved steadily forward, and how they are responsible for much of our current understanding of the etiology and pathology of MOF. This review is not intended to be all encompassing nor a historical reference. Rather, it serves as recognition to the foresight and support of many past and present individuals at the NIGMS and at academic institutions who have understood the cost of critical illness and MOF to the individual and to society.

Nutrition Support for Critically Ill Patients With Cancer

Oncology patients often experience the classic signs of malnutrition-weight loss as well as fat and muscle wasting, which have been associated with poor tolerance to treatment and increased morbidity and mortality. Nutrition status may be an important factor in determining tolerance to treatment and outcomes associated with it. Thus, identification of those with preexisting malnutrition or who are at risk for developing malnutrition is crucial not only at time of cancer diagnosis but also throughout the treatment course so that nutrition interventions may be implemented to prevent development or worsening of malnutrition in this high-risk population. These patients often have extremely complicated hospital courses due to the aggressive nature of the disease and treatment, leading to intensive care unit admission and periods of critical illness. Critical illness is associated with catabolism, extreme stress on the body, and a state of systemic inflammation. During critical illness, it is important to provide adequate nutrition to prevent further break down of lean muscle mass and oxidative cellular injury and to regulate favorable immune responses. The purpose of this review is to discuss the importance of nutrition screening and assessment for the critically ill patient with cancer; to appropriately identify those at risk for, or who have developed, malnutrition; and to provide appropriate interventions to optimize nutrition status. This review also discusses the complications and difficulties associated with feeding this patient population and offers nutrition support recommendations.

Nutrition Support for Persistent Inflammation, Immunosuppression, and Catabolism Syndrome

Despite tremendous advances in critical care, multiple-organ failure continues to be a significant problem. However, in recent years, far fewer patients with multiple-organ failure die early, but many experience ongoing immune dysregulation and are developing persistent inflammation, immunosuppression, and catabolism syndrome (PICS). Most PICS patients are discharged to nonhome destinations, fail to rehabilitate, and succumb to indolent death. From a nutrition perspective, patients with PICS experience persistent inflammation-induced cachexia despite evidenced-based recommended intensive care unit nutrition support. Recent basic and translational research indicates that prolonged expansion of myeloid-derived suppressor cells plays a central role in the pathogenesis of PICS. Myeloid-derived suppressor cells express arginase 1, which depletes arginine, causing immunosuppression and impaired wound healing. This is the rationale for arginine supplementation in PICS. Other nutrition support recommendations for PICS are based on inferences made from other patient populations who experience similar persistent inflammation-induced cachexia. These include patients with established cancers, major burns, and sarcopenia. These patients experience anabolic resistance, but studies show that this can be overcome by providing higher levels of protein and certain specific amino acids. Nutrition support guidelines recommend provision of >1.5 g/kg/d of protein and indicate that higher levels may be needed. Protein composition is also important. There is good evidence that leucine can promote anabolism in patients with cancer and sarcopenia. Finally, anabolic interventions-including intensive insulin, oxandrolone, propranolol, and resistance exercise-have proven to be effective in patients with major burns and are likely relevant in combating PICS cachexia.

Nutrition Support in Adult Trauma Patients

Nutrition supplementation is paramount to the care of severely injured patients. Despite its widespread use in trauma patients, many areas of clinical practice remain controversial. The purpose of this paper is to critically review the literature studying the use of enteral vs parenteral nutrition (PN) and to provide the rationale for early enteral nutrition. Additional controversies confronting clinicians are reviewed, including the use of immune-enhancing agents and the optimal site for enteral nutrition delivery (gastric vs small intestinal). Evidence-based recommendations for clinical practice are presented when available.

Tablet PC-enabled application intervention for patients with gastric cancer undergoing gastrectomy

BACKGROUND

Gastric cancer is among the most common gastrointestinal cancers worldwide. Patients who have undergone surgery for gastric cancer may suffer from malnutrition and potential consequences such as gastrointestinal complications, surgical stress, and cancer cachexia. A tablet PC-based intervention via a mobile application might enhance the early recovery of postgastrectomy patients.

OBJECTIVE

The aim of this study was to develop and test a tablet personal computer (PC)-assisted intervention to hasten the recovery of postgastrectomy cancer patients with respect to nutritional status.

METHODS

This single-arm pilot study investigated a tablet PC application developed to serve the functions of nutritional monitoring, medical information management, drainage follow-up, and wound care. All services were delivered by medical professionals.

RESULTS

Twenty consecutive gastrectomy patients at the National Taiwan University Hospital received perioperative care via this application (App group). During the study period, we retrospectively collected an additional 20 demographically matched gastrectomy cases as a control group. The App group had a lower body weight loss percentage relative to the control group during a 6-month follow-up period (4.8±1.2% vs. 8.7±2.4%; p<0.01). However, the patients in the App group had more outpatient clinic (OPC) visits than did those in the control group (9.8±0.9 vs. 5.6±0.8; p<0.01).

CONCLUSIONS

This study supported the feasibility of a tablet PC-based application for the perioperative care of gastric cancer subjects to promote a lower body weight loss and the collection of comprehensive surgical records.

Malnutrition at the time of surgery affects negatively the clinical outcome of critically ill patients with gastrointestinal cancer

Introduction:

Malnutrition is a frequent concomitant of surgical illness, especially in gastrointestinal cancer surgery. The aim of the study was to assess the prevalence of malnutrition in the GI cancer patients and its relation with clinical outcome. We also examined associations between the energy balance and clinical outcomes in these patients.

Methods:

Prospective study on 694 surgical patients treated in the ICU of the UHC of Tirana. Patients were divided into well-nourished and malnourished groups according to their nutritional status. Multiple regression analysis was used to analyze the effect of malnutrition and cumulated energy balance on clinical outcome.

Results:

The prevalence of pre-operative malnutrition was 65.3% for all surgical patients and 84.9% for gastrointestinal cancer patients. Malnutrition, as analyzed by a multivariate logistic regression model, is an independent risk factor for higher complications, infections, and mortality, longer stay in the ventilator and ICU. Also this model showed that cumulated energy balance correlated with infections, and mortality and was independently associated with the length ventilator and ICU stay.

Conclusion:

This study shows that malnutrition is a significant problem in surgical patients, especially in patients with gastrointestinal cancer. Malnutrition and cumulated energy deficit in gastro-intestinal surgery patients with malignancy is an independent risk factor on increased post-operative morbidity and mortality.

Cost-effectiveness analysis of immune-modulating nutritional support for gastrointestinal cancer patients

BACKGROUND & AIM

Immune-modulating nutritional formula containing arginine, omega-3 fatty acids and nucleotides has been demonstrated to decrease complications and length of stay in surgical patients. This study aims at assessing the impact of immune-modulating formula on hospital costs in gastrointestinal cancer surgical patients in Switzerland.

METHOD

Based on a previously published meta-analysis, the relative risks of overall and infectious complications with immune-modulating versus standard nutrition formula were computed. Swiss hospital costs of patients undergoing gastrointestinal cancer surgery were retrieved. A method was developed to compute the patients' severity level, not taking into account the complications from the surgery. Incremental costs of complications were computed for both treatment groups, and sensitivity analyses were carried out.

RESULTS

Relative risk of complications with pre-, peri- and post-operative use of immune-modulating formula was 0.69 (95%CI 0.58-0.83), 0.62 (95%CI 0.53-0.73) and 0.73 (95%CI 0.35-0.96) respectively. The estimated average contribution of complications to the cost of stay was CHF 14,949 (€10,901) per patient (95%CI 10,712-19,186), independently of case's severity. Based on this cost, immune-modulating nutritional support decreased costs of hospital stay by CHF 1638 to CHF 2488 per patient (€1195-€1814). Net hospital savings were present for baseline complications rates as low as 5%.

CONCLUSION

Immune-modulating nutritional solution is a cost-saving intervention in gastrointestinal cancer patients. The additional cost of immune-modulating formula are more than offset by savings associated with decreased treatment of complications.

Risk factors of organ failure in patients with bacteremic cholangitis

BACKGROUND

Bacteremic cholangitis carries a high mortality rate of up to 10 % in relation to organ failure (OF), including septic shock.

AIM

The purpose of this study was to elucidate predictive factors for OF in bacteremic cholangitis.

METHODS

A retrospective review of all patients diagnosed with acute cholangitis and proven bacteremia from 2003 to 2011 was performed. Comprehensive clinical and laboratory data of 211 patients were analyzed.

RESULTS

There were 42 cases (19.9 %) of OF and 5 deaths (2.4 %). In the multivariate logistic regression analysis, significant predictive factors for OF were successful biliary decompression, presence of extended-spectrum beta-lactamase organism (ESBL), higher total bilirubin, and higher blood urea nitrogen (BUN) level at admission with odds ratios (ORs) of 0.129, 6.793, 1.148, and 1.089, respectively. Subgroup analysis of 165 patients who underwent biliary decompression before an event (with OF: 20, without OF: 145) was performed to elucidate the risk factors for organ failure even after successful biliary drainage. Variables significantly associated with OF included ESBL and BUN (OR = 4.123 and 1.177, respectively). We developed a scoring system with regression coefficient of each significant variable. The organ failure score was calculated using the following equation: (1.4 × ESBL) + (0.2 × BUN). This scoring system for predicting OF was highly sensitive (85.0 %) and specific (83.4 %).

CONCLUSIONS

Biliary decompression, ESBL, total bilirubin, and BUN are prognostic determinants in patients with bacteremic cholangitis. An organ failure scoring system may allow clinicians to identify groups with poor prognosis even after successful biliary decompression.

Surgery in esophageal and gastric cancer patients: what is the role for nutrition support in your daily practice?

Cancers of the esophagus and stomach have a major impact on patients' nutritional status by virtue of these organs' inherent digestive functions. Many patients with these cancers will require surgical intervention, which imposes further metabolic demands and compounds preexisting nutritional disorders. Patients with esophagogastric cancer are likely to have lost weight by the time the diagnosis is made. This fact alone is of clinical importance, because it is well known that patients who have lost weight will have higher operative mortality and morbidity rates than patients who maintain their weight. Initial assessment of patients with esophagogastric cancer should include a routine evaluation of nutritional status. This will allow the identification of patients who are at risk of complications, particularly in the postoperative setting. These patients should be targeted for specific nutritional support.

Molecular mechanisms of pharmaconutrients

Nutritional supplementation has become the standard of care for management of critically ill patients. Traditionally, nutritional support in this patient population was intended to replete substrate deficiencies secondary to stress-induced catabolism. Recognition of the influence of certain nutrients on the immune and inflammatory response of the critically ill has led to the evolution of more sophisticated nutritional strategies and concepts. Administration of immune-enhancing formulas supplemented with a combination of glutamine, arginine, omega-3 fatty acids (omega-3 FA), and nucleotides have been shown in most studies to reduce infectious outcomes. More recently, the separation of nutritional support from the provision of key nutrients has led to a further appreciation of the immunomodulatory and anti-inflammatory benefits of isolated nutrients, such as glutamine and antioxidants. The purpose of this article is to review the molecular mechanisms that are unique to each class of frequently utilized nutrients. A better understanding of the specific molecular targets of immunonutrients will facilitate application of more refined nutritional therapies in critically ill patients.

Enteral glutamine during active shock resuscitation is safe and enhances tolerance of enteral feeding

BACKGROUND

Feeding the hemodynamically unstable patient is increasingly practiced, yet few data exist on its safety. Because enteral glutamine is protective to the gut in experimental models of shock and improves clinical outcomes, it may benefit trauma patients undergoing shock resuscitation and improve tolerance if administered early. This pilot study aimed to evaluate gastrointestinal tolerance and safety of enteral feeding with glutamine, beginning during shock resuscitation in severely injured patients.

METHODS

In a prospective randomized trial, 20 patients were randomly assigned to either an enteral glutamine group (n = 10) or a control group (n = 10). Patients with severe trauma meeting standardized shock resuscitation criteria received enteral glutamine 0.5 g/kg/d during the first 24 hours of resuscitation and 10 days thereafter. Immune-enhancing diet began on postinjury day 1, with a target of 25 kcal/kg/d. Control patients received isonitrogenous whey powder plus immune-enhancing diet. Tolerance (vomiting, nasogastric output, diarrhea, and distention) was assessed throughout the study.

RESULTS

Glutamine was well tolerated and no adverse events occurred. Treated patients had significantly fewer instances of high nasogastric output (5 vs 23; p = .010), abdominal distention (3 vs 12; p = .021), and total instances of intolerance (8 vs 42; p = .011). Intensive care unit (ICU) and hospital length of stay were comparable. Control patients required supplemental parenteral nutrition (PN) to meet goals at day 7.

CONCLUSIONS

Enteral glutamine administered during active shock resuscitation and through the early postinjury period is safe and enhances gastrointestinal tolerance. A large clinical trial is warranted to determine if enteral glutamine administered to the hemodynamically unstable patient can reduce infectious morbidity and mortality.

Influence of adding fish oil to parenteral nutrition on gut-associated lymphoid tissue

BACKGROUND

Lack of enteral nutrition reduces gut-associated lymphoid tissue (GALT) mass and function, a mechanism underlying the increased morbidity of infectious complications in severely injured or critically ill patients. Strategies to restore parenteral nutrition (PN)-induced changes of GALT mass and function have been pursued. However, the influences of adding fish oil to PN on gut immunity remain to be clarified.

METHODS

Male Institute of Cancer Research (ICR) mice (n = 50) were randomized to 4 groups: ad libitum chow (chow), fat free PN (fat (-)-PN), PN + fish oil (FO-PN), and PN + safflower oil (SO-PN). The PN groups were given isocaloric and isonitrogenous PN solutions. The FO- and SO-PN groups received 20% of total calories from fat emulsions. After 5 days of feeding, lymphocytes from Peyer's patches (PPs), the intraepithelial space (IE), and the lamina propria (LP) of the entire small intestine were isolated. GALT lymphocyte numbers and phenotypes (CD4+, CD8+, alphabetaTCR+, gammadeltaTCR+, B220+ cells) were determined. Immunoglobulin A (IgA) levels of small intestinal washings were also measured by enzyme-linked immunosorbent assay. Another set of mice (n = 24) was used to determine plasma fatty acid compositions after feeding.

RESULTS

Lymphocyte numbers from PPs and the LP and intestinal IgA levels were significantly lower in the PN groups than in the chow group, with no significant differences between any 2 PN groups. The FO- and SO-PN groups showed moderate recovery of IE cell numbers compared with the fat (-)-PN group. Omega-3 and omega-6 fatty acid levels were increased with fish and safflower oil additions, respectively, compared with the fat (-)-PN group.

CONCLUSIONS

Adding fish oil to PN does not exacerbate PN-induced GALT changes but rather partially reverses these changes, with increased plasma omega-3 fatty acid levels.

Guidelines for nutritional support in intensive care unit patients: a critical analysis

PURPOSE OF REVIEW

Guidelines are supposed to be helpful in clinical practice. Guidelines are also supposed to rest upon the evidence that there is. In the field of clinical nutrition the problem is that many clinical trials are not conclusive because they are underpowered and sometimes have an inferior design.

RECENT FINDINGS

The publication of the Canadian guidelines one year ago initiated a lively debate. The Canadian guidelines used meta-analysis as a tool to review the literature. This resulted in both a sound evaluation of studies as well as some controversial recommendations. The Canadian guidelines are here put in a perspective in which the older type of guidelines are compared, and some of the points of recommendation are scrutinized.

SUMMARY

What all guidelines agree upon is the shortage of solid knowledge, the conviction that complications related to nutritional therapy in the intensive care unit are not acceptable, and that enteral nutrition is preferable if it can be given without risk. Beyond that, many controversies remain and the need for high quality prospective studies must be emphasized. In addition, such studies must address the clinically important questions that the guidelines try to answer.

Hypertonic saline prevents inflammation, injury, and impaired intestinal transit after gut ischemia/reperfusion by inducing heme oxygenase 1 enzyme

BACKGROUND

Hypertonic saline (HTS) has been shown to modulate the inflammatory response after shock. We have previously demonstrated that heme oygenase-1 (HO-1) induction is protective against gut dysfunction in models of shock-induced gut ischemia/reperfusion (I/R). We therefore hypothesized that HTS prevents gut inflammation, injury, and impaired transit by inducing HO-1 in a model of gut I/R.

METHODS

Rats underwent 60 minutes of superior mesenteric artery occlusion (SMAO) and then were resuscitated with 4 mL/kg of HTS, an equal volume of lactated Ringer's (LR) solution (4 mL/kg, low volume), or equal salt LR solution (32 mL/kg, high volume) and compared with SMAO alone or shams. A separate group was pretreated with the HO-1 blocker Sn protoporphyrin IX (SNP IX) before SMAO plus HTS. At 6 hours of reperfusion, transit was determined and ileum harvested for HO-1 (anti-inflammatory) and inducible nitric oxide synthase (proinflammatory) immunoreactivity, myeloperoxidase (MPO) activity, and histologic injury. Data are expressed as mean +/- SEM (analysis of variance).

RESULTS

Intestinal transit was severely impaired after SMAO (2.5 +/- 0.1), improved with low- and high-volume LR solution (3.2 +/- 0.2 and 3.1 +/- 0.1, not significant), but returned to sham (4.6 +/- 0.2) with HTS (4.8 +/- 0.2). Pretreatment with SNP abrogated this protective effect. Myeloperoxidase activity was significantly increased by SMAO (SMAO, 2.3 +/- 0.3; sham, 0.4 +/- 0.05), lessened by low- and high-volume LR solution (1.5 +/- 0.3 and 1.7 +/- 0.4), but returned to sham levels with HTS (1.0 +/- 0.01). Activity with SNP IX pretreatment was significantly increased (4.04 +/- 0.8). Mucosal injury followed a similar pattern. Inducible nitric oxide synthase was increased by SMAO and low- and high-volume LR solution (0.8 +/- 0.2, 0.8 +/- 0.03, and 0.8 +/- 0.02, respectively; sham, 0.5 +/- 0.02), but significantly reduced by HTS (0.7 +/- 0.02). HO-1 was induced by SMAO and low- and high-volume LR solution (0.33 +/- 0.02, 0.32 +/- 0.03, and 0.37 +/- 0.4, respectively; sham, 0.0 +/- 0.0), but was further increased with HTS (0.49 +/- 0.04).

CONCLUSION

HTS resuscitation protects against inflammation, injury, and impaired intestinal transit after gut I/R in part by inducing HO-1. This is a novel mechanism of HO-1 protection.

The puzzle of sepsis: fitting the pieces of the inflammatory response with treatment

Sepsis is a complex syndrome characterized by simultaneous activation of inflammation and coagulation in response to microbial insult. These events manifest as systemic inflammatory response syndrome (SIRS)/sepsis symptoms through release of proinflammatory cytokines, procoagulants, and adhesion molecules from immune cells and/or damaged endothelium.Conventional treatments have focused on source control, antimicrobials, vasopressors, and fluid resuscitation; however, a new treatment paradigm exists: that of treating the host response to infection with adjunct therapies including early goal directed therapy, drotrecogin alfa (activated), and immunonutrition. The multimechanistic drotrecogin alfa (activated) has been shown to reduce mortality in the severely septic patient when combined with traditional treatment. Therapies targeting improved oxygen and blood flow and reduction of apoptosis and free radicals are under investigation. Early sepsis diagnosis through detection of pro calcitonin, C reactive protein, sublingual CO2, and genetic factors may be beneficial. Ultimately, intervention timing may be the most important factor in reducing severe sepsis mortality.

Early enteral immunonutrition in patients with severe sepsis: results of an interim analysis of a randomized multicentre clinical trial

OBJECTIVE

To compare the mortality of critically ill patients given either enteral feeding with an immune-enhancing formula or parenteral nutrition (PN). We report the results of a planned interim analysis on patients with severe sepsis which was undertaken earlier than planned once a meta-analysis suggested excess mortality in patients with severe sepsis given enteral immunonutrition.

DESIGN

Randomised multicentre unblinded controlled clinical trial.

SETTING

Thirty-three General Intensive Care Units in Italy.

PATIENTS AND PARTICIPANTS

Among the 237 recruited patients, 39 had severe sepsis or septic shock; 21 of them received PN.

INTERVENTIONS

Eligible patients received either total PN or enteral nutrition, the latter containing extra L-arginine, omega-3 fatty acids, vitamin E, beta carotene, zinc, and selenium.

MEASUREMENTS AND RESULTS

The primary endpoint for the subgroup analysis on patients with severe sepsis was mortality on Intensive Care Unit (ICU). The ICU mortality of patients with severe sepsis given enteral nutrition (EN) was higher than for those given PN (44.4% vs 14.3%; p=0.039). More patients given EN than patients given PN still had severe sepsis when they died (38.9% vs 9.5%, p=0.055). Recruitment of patients with severe sepsis was subsequently stopped.

CONCLUSIONS

Our results show that enteral immunonutrition, compared to PN, may be associated with excess mortality in patients with severe sepsis.

Immune-enhancing diets for stressed patients with a special emphasis on arginine content: analysis of the analysis

PURPOSE OF REVIEW

After two decades of intensive research, whether arginine-enriched diets for oral/enteral administration are beneficial or harmful for stressed patients remains uncertain. An American consensus and a meta-analysis provide divergent conclusions. The main goal of the present review is to analyze these documents.

RECENT FINDINGS

The so-called immune-enhancing diets have been found to be beneficial to postoperative patients. Nothing proves, however, that arginine is responsible for these beneficial effects since immune-enhancing diets contain other pharmacologically active components (e.g. omega3 free fatty acids, RNAs, antioxidant vitamins). In fact, arginine-enriched diets may be harmful in hemodynamically unstable patients and those presenting with multiple organ failure.

SUMMARY

In light of the current doubts and until convincing data are produced, immune-enhancing diets should not be used in unstable critically ill patients.

Factors predisposing to bacterial invasion and infection

BACKGROUND

Bacterial infections remain important causes of morbidity and mortality in surgical patients. Our understanding of the effects of bacteria on the host, and also the defense mechanisms available to the host, is improving all the time. Modern tools in biochemistry, immunology, and molecular biology have provided powerful methods to further our understanding of the complex interactions that contribute to our host defense response. This review reflects current thinking regarding the factors that contribute to bacterial infection and host defense response.

DATA SOURCES

This review was compiled after an extensive review of the current and historical literature, and highlights a number of areas involved in the pathogenesis of bacterial infection.

CONCLUSIONS

Bacteria can have a wide-ranging and deleterious effect on the host. Many different therapeutic approaches have been attempted to modulate the host response and limit the deleterious effects of bacteria. As our understanding of the underlying processes improves, these therapies should improve accordingly.

Nutrition and gastrointestinal cancer

The present review addresses data from randomized clinical trials on perioperative nutrition in patients with gastrointestinal cancer. It is important to appreciate that different approaches can be used with regard to timing of administration of nutritional support (preoperative versus postoperative), route of administration (parenteral versus enteral) and composition of the admixtures given (standard versus immune-enriched diets). The rationale underlying these approaches may also vary, and may include correction of nutritional status, attenuation of the acute-phase response through better preservation of gut function, and potentiation of the immune response.