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August 2003

Xylitol candies in caries prevention: results of a field study in Estonian children.

All field studies have unequivocally reported significant reductions in dental caries occurrence associated with the use of chewing gum containing xylitol. No other xylitol products besides chewing gum have so far been tested in field trials. A five-year follow-up study with two- or three-year xylitol consumption periods began in Estonia in 1994 with 740 10-year-old children in 12 schools at baseline examinations. For the study, three clusters each including three to five schools were formed on the basis of baseline caries experience. The products were used under the supervision of the teachers three times per day during school days but not during weekends or during the three-month summer holiday. The daily dose of xylitol was 5 g in all groups. The children were examined every year in September by two experienced clinicians. Dental caries was recorded according to WHO criteria. After three years, all xylitol groups showed a highly significant 35% to 60% reduction in caries incident, compared with the corresponding control groups. The differences between candies, between candies and chewing gum, and between two- and three-year users in the xylitol groups were non-systematic, indicating no trends between the groups. The results suggest that not only xylitol chewing gum but also xylitol candies are effective in caries prevention, and that a school-based delivery system seems to offer a practical way to distribute and control the use of the xylitol products.

Community Dent Oral Epidemiol 2000 Jun;28(3):218-24


Branched-chain amino acid supplementation and the immune response of long-distance athletes.

OBJECTIVE: Intense long-duration exercise has been associated with immunosuppression, which affects natural killer cells, lymphokine-activated killer cells, and lymphocytes. The mechanisms involved, however, are not fully determined and seem to be multifactorial, including endocrine changes and alteration of plasma glutamine concentration. Therefore, we evaluated the effect of branched-chain amino acid supplementation on the immune response of triathletes and long-distance runners. METHODS: Peripheral blood was collected prior to and immediately after an Olympic Triathlon or a 30k run. Lymphocyte proliferation, cytokine production by cultured cells, and plasma glutamine were measured. RESULTS: After the exercise bout, athletes from the placebo group presented a decreased plasma glutamine concentration that was abolished by branched-chain amino acid supplementation and an increased proliferative response in their peripheral blood mononuclear cells. Those cells also produced, after exercise, less tumor necrosis factor, interleukins-1 and -4, and interferon and 48% more interleukin-2. Supplementation stimulated the production of interleukin-2 and interferon after exercise and a more pronounced decrease in the production of interleukin-4, indicating a diversion toward a Th1 type immune response. CONCLUSIONS: Our results indicate that branched-chain amino acid (BCAA) supplementation recovers the ability of peripheral blood mononuclear cells proliferate in response to mitogens after a long distance intense exercise, as well as plasma glutamine concentration. The amino acids also modify the pattern of cytokine production leading to a diversion of the immune response toward a Th1 type of immune response.

Nutrition 2002 May;18(5):376-9

Therapeutic considerations of L-glutamine: a review of the literature.

The most abundant amino acid in the bloodstream, L-glutamine fulfills a number of biochemical needs. It operates as a nitrogen shuttle, taking up excess ammonia and forming urea. It can contribute to the production of other amino acids, glucose, nucleotides, protein and glutathione. Glutamine is primarily formed and stored in skeletal muscle and lungs, and is the principal metabolic fuel for small intestine enterocytes, lymphocytes, macrophages and fibroblasts. Supplemental use of glutamine, either in oral, enteral or parenteral form, increases intestinal villous height, stimulates gut mucosal cellular proliferation and maintains mucosal integrity. It also prevents intestinal hyperpermeability and bacterial translocation, which may be involved in sepsis and the development of multiple organ failure. L-glutamine use has been found to be of great importance in the treatment of trauma and surgery patients, and has been shown to decrease the incidence of infection in these patients. Cancer patients often develop muscle glutamine depletion, due to uptake by tumors and chronic protein catabolism. Glutamine may be helpful in offsetting this depletion; however, it may also stimulate the growth of some tumors. The use of glutamine with cancer chemotherapy and radiotherapy seems to prevent gut and oral toxic side effects, and may even increase the effectiveness of some chemotherapy drugs.

Altern Med Rev 1999 Aug;4(4):239-48

Plasma-amino acid profiles in sepsis and stress.

Sepsis has been associated with specific plasma amino acid patterns. Sixty-five patients were prospectively investigated as to whether these patterns are indeed sepsis specific, or specific for metabolic stress without concomitant sepsis, or associated with the presence of organ failure. Virtually all aminoacid levels were decreased by 10% to 30% (p less than 0.05), whereas cystine and phenylalanine were significantly elevated. These changes were more pronounced in severe sepsis. Organ failure was not associated with significantly altered amino acid profiles. No differences were found between sepsis and stress without signs of sepsis. In addition, imminent death was not associated with aberrant amino acid profiles. We conclude that sepsis and metabolic stress are associated with changes in plasma amino acid profiles, but that such changes are aspecific and therefore poor indicators of disease severity.

Ann Surg 1989 Jan;209(1):57-62

Glutamine: clinical applications and mechanisms of action.

Supplementation of the conditionally essential amino acid glutamine may be beneficial for individuals who are highly stressed and have minimal energy and protein reserves. This includes elderly individuals, postoperative patients, individuals with cancer and very low birthweight infants. Individuals who are undergoing treatment with catabolic glucocorticoids may also benefit. Unfortunately, confusion exists as to situations in which glutamine may be beneficial because a clearly defined "glutamine deficiency syndrome" has not been described as for some other nutrients. In this review, we will discuss how glutamine affects protein metabolism under certain stressful conditions, how it affects intestinal mucosal integrity and how this might relate to sepsis and systemic inflammation. We will also discuss nutrients that are closely related to glutamine such as glutamate, nucleotides, arginine, glucosamines, and ornithine alpha-ketoglutarate and how and why they might be used as substitutes for glutamine.

Curr Opin Clin Nutr Metab Care 2002 Jan;5(1):69-75

Glutamine supplementation in bone marrow transplantation.

An increasing number of clinical investigations have focused on supplementation of specialized enteral and parenteral nutrition with the amino acid glutamine. This interest derives from strong evidence in animal models and emerging clinical data on the efficacy of glutamine administration following chemotherapy, trauma, sepsis and other catabolic conditions. Glutamine has protein-anabolic effects in stressed patients and, among many key metabolic functions, is used as a major fuel/substrate by cells of the gastrointestinal epithelium and the immune system. These effects may be particularly advantageous in patients undergoing bone marrow transplantation (BMT), who exhibit post-transplant body protein wasting, gut mucosal injury and immunodeficiency. Studies to date indicate that enteral and parenteral glutamine supplementation is well tolerated and potentially efficacious after high-dose chemotherapy or BMT for cancer treatment. Although not all studies demonstrate benefits, sufficient positive data have been published to suggest that this nutrient should be considered as adjunctive metabolic support of some individuals undergoing marrow transplant. However, BMT is a rapidly evolving clinical procedure with regard to the conditioning and supportive protocols utilized. Thus, additional randomized, double-blind, controlled clinical trials are indicated to define the efficacy of glutamine with current BMT regimens.

Br J Nutr 2002 Jan;87 Suppl 1:S9-15

Glutamine: essential for immune nutrition in the critically ill.

Critically ill patients on intensive care units are at an increased risk of sepsis, which is a major cause of mortality in these patients. Recent evidence suggests that impairment of the functioning of the immune system contributes to the development of sepsis in such patients. In particular, monocytes show reduced expression of HLA-DR antigen, associated with impaired antigen presenting capability and decreased phagocytic activity; lymphocytes show decreased proliferation in response to mitogens and T-helper cells show a shift in the Th1/Th2 ratio consistent with impaired immunity. The amino acid glutamine becomes conditionally essential in the critically ill, yet such patients frequently have a marked deficiency of glutamine; the reasons for this are still unclear. Glutamine is required by the cells of the immune system both as a primary fuel and as a carbon and nitrogen donor for nucleotide precursor synthesis. In vivo studies have demonstrated that glutamine is essential for optimal immune cell functioning for monocytes, lymphocytes and neutrophils. A number of trials of patients fed by the enteral or parenteral route have shown improved infectious morbidity when supplemented with glutamine. However, the exact mechanism of glutamine action in these patients remains to be determined.

Br J Nutr 2002 Jan;87 Suppl 1:S3-8

Can glutamine modify the apparent immunodepression observed after prolonged, exhaustive exercise?

Glutamine is an important fuel for some cells of the immune system. In situations of stress, such as clinical trauma, starvation, or prolonged, strenuous exercise, the concentration of glutamine in blood is decreased, often substantially. In endurance athletes this decrease occurs concomitantly with relatively transient immunodepression. Provision of glutamine or a glutamine precursor has been found to decrease the incidence of illness in endurance athletes. To date, it has not been established precisely which aspect of the immune system is affected by glutamine feeding during the transient immunodepression that occurs after prolonged, strenuous exercise. However, there is increasing evidence that neutrophils may be implicated.

Nutrition 2002 May;18(5):371-5


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