免疫营养的科学基础

Substrates with immune-modulating actions have been identifiedamong both macro and micronutrients.Currently,the modes of action of individual immune-modulating substrates,and their effects on clinical outcomes,are being examined.At present,some enteral formulas are available for the clinical setting which are enriched with selected immune-modulating nutritnts.The purpose of the present paper is to review the scientific rationale of enteral immunonutrition.The major aspects considered are mucosal barrier structure and function,cellular defence function and local or systemic inflammatory response.It is notable that in critical illness the mucosal barrier and cellular defence are impaired and a reinforcement iwht enteral immunonutrition is desirable,while local or systemic inflammatory response should be down regulated by nutritional interventions.The results available from clinical trials are conflicting.Meta-analyses of recent trials show improvements such as reduced risk of infeciton,fewer days on a ventilator,and reduced length of intensive care unit and hospital stay.Thus,a grade A recommendation was proclaimed for the clinical use of enteral immune-modulationg diets.Improvemtnet in outcome was only seen when critical amounts of the immune-modulating formula were tolerated in patients classified as being malnourished.However,in other patients with severe sepsis,shock and organ failure,no benefit or even disadvantages form immunonutrition were reported.In such severe conditions we hypothesize that systemic inflammation might be undesirably intensified by arginine and unsaturated fatty acids,directly affecting cellular defence and inflammatory response.We therefore recommed that in patients suffering from systemic inflammatory response syndrome great caution should be exercised when immune-enhancing substrates are involuvd which may aggravate systemic inflammation.     

The scientific basis of immunonutrition

Substrates with immune-modulating actions have been identified among both macro- and micronutrients. Currently, the modes of action of individual immune-modulating substrates, and their effects on clinical outcomes, are being examined. At present, some enteral formulas are available for the clinical setting which are enriched with selected immune-modulating nutrients. The purpose of the present paper is to review the scientific rationale of enteral immunonutrition. The major aspects considered are mucosal barrier structure and function, cellular defence function and local or systemic inflammatory response. It is notable that in critical illness the mucosal barrier and cellular defence are impaired and a reinforcement with enteral immunonutrition is desirable, while local or systemic inflammatory response should be down regulated by nutritional interventions. The results available from clinical trials are conflicting. Meta-analyses of recent trials show improvements such as reduced risk of infection, fewer days on a ventilator, and reduced length of intensive care unit and hospital stay. Thus, a grade A recommendation was proclaimed for the clinical use of enteral immune-modulating diets. Improvement in outcome was only seen when critical amounts of the immune-modulating formula were tolerated in patients classified as being malnourished. However, in other patients with severe sepsis, shock and organ failure, no benefit or even disadvantages from immunonutrition were reported. In such severe conditions we hypothesize that systemic inflammation might be undesirably intensified by arginine and unsaturated fatty acids, directly affecting cellular defence and inflammatory response. We therefore recommend that in patients suffering from systemic inflammatory response syndrome great caution should be exercised when immune-enhancing substrates are involved which may aggravate systemic inflammation.     

The scientific basis of tobacco product regulation

This report presents the conclusions reached and recommendations made by the members of the WHO Study Group on Tobacco Product Regulation at its third meeting, during which it reviewed four background papers specially commissioned for the meeting and which dealt, respectively, with the following four themes. 1. The contents and design features of tobacco products: their relationship to dependence potential and consumer appeal. 2. Candy-flavoured tobacco products: research needs and regulatory recommendations. 3. Biomarkers of tobacco exposure and of tobacco smoke-induced health effects. 4. Setting maximum limits for toxic constituents in cigarette smoke. The Study Group's recommendations in relation to each theme are set out at the end of the section dealing with that theme; its overall recommendations are summarized in section 6.     

The scientific basis of a total asbestos ban

Worldwide, in the new millennium, standards for the protection of workers and the general population from as-bestos risks are not equally stringent in all countries. The present review analyzes some arguments which in recent years have been proposed as a rationale for the reconsideration of the scientific background of a total asbestos ban, such as that adopted in the European Union. The conclusion is that in order to ensure adequate protection, there is no alternative to a total ban. The evidence for carcinogenicity of chrysotile is as good as for the amphiboles, the carcinogenic potency of chrysotile is lower than that of the amphiboles, but risk estimates must also be based on extent of exposure (nowadays chrysotile represents 95% of asbestos used worldwide). The fact that induction of mesothelioma by asbestos results from the interaction of environmental exposure and genetic factors reflects a general phenomenon in carcinogenesis and does not warrant any re-consideration of the role of asbestos. The role of SV40 as yet is unclear: even assuming that current risk estimates are correct (which is debatable), this agent would interact with asbestos in only a faction of mesothelioma cases. The effectiveness of protocols suggested for "controlled use" has not been tested with a scientfiic approach: they seem hardly practicable, particularly in the countries which are currently the major consumers of asbestos.     

Codex recommendations on the scientific basis of health claims

Background

Within the framework of Codex Alimentarius, attempts are being made at international level to establish guidelines for use of nutrition and health claims. An important issue that has to be addressed is the process of scientific substantiating of claims on foods.

Objective

To provide an insight into the current step procedure of the proposed draft recommendations on the scientific basis of health claims. These Codex recommendations are intended to facilitate governments’ own evaluation of health claims made by the industry.

Methods

Review of comments of governments, observers and non-governmental organizations (NGOs) and relevant references to the proposed draft recommendations of the last sessions of the Codex Committee on Nutrition and Food for Special Dietary Uses (CCNFSDU). A literature search was performed using the PubMed database.

Results/Conclusions

Several proposed draft recommendations on the scientific substantiation of health claims have been considered and amended by the CCNFSDU in recent years but the work is not yet complete. The current work draws on the work of FUFOSE and PASSCLAIM and also on that of WHO and FDA. Given the important role of Codex in food safety, the draft recommendations emphasize circumstances where additional evaluation of safety or nutritional safety needs to be considered. High quality human intervention studies are the prime evidence needed to substantiate claims but there is recognition that, in some cases, only observational studies may be available. Animal and in vitro studies will also be evaluated as part of the totality of the evidence. It has been suggested that the recommendations should include re-evaluation of claims after a certain time period, or if new evidence calls into question the scientific validity underpinning the claims. Setting out a common approach for the substantiation of health claims is an important step in the use of health claims around the world. There is a need to reflect emerging as well as consensus science. The substantiating evidence should be proportionate to the claim. Further progress in the elaboration of this relevant Codex text is needed to reach consensus.

     

Invited commentary: The scientific basis for stopping polio immunization

This article summarizes the WHO-sponsored meeting of virologists, immunologists, and epidemiologists in March 1998 to address the final and controversial stage of the polio eradication initiative. The meeting commissioned Fine and Carneiro's literature review and mathematical model delineating the important gaps in the scientific knowledge and helped define the research agenda of the remaining few years of the initiative. Fine and Carneiro proposed that the possibility of continuing circulation of vaccine-derived polioviruses (VDPV) could not be excluded with absolute certainty. They also argued that VDPV may continue to circulate after use of oral polio vaccine stops and that immunodeficient persons may be a potential reservoir from which VDPV could be reintroduced into the general population. Their work further highlights that high-level enterovirus surveillance will be essential in the years after immunization has stopped.     

Percutaneous ethanol injection of parathyroid adenoma under US guidance

A patient with post-operative recurrent parathyroid adenoma was treated with percutaneous injection of absolute ethanol under ultrasonographic guidance. Serum calcium and PTH level were both successfully normalized, while recurrent nerve palsy was encountered as side effect. Six months later, she was suffered from hyperparathyroidism again, because of local tumor recurrence. Her recurrent nerve palsy was cured at that time. This technic could be a simple and non-invasive alternative for the conventional surgical procedure, but the indication for larger adenomas like this case should be carefully considered.     

Consumption of sugars and the regulation of short-term satiety and food intake

This review examines the relation between the consumption of sugars and their effects on short-term (ie, to 2 h) satiety and food intake in humans. Many factors need to be considered in the evaluation of reported studies and the conclusions derived from this body of literature. These factors include evaluation of the dose and form (solid or liquid) of the treatments, time of day administered, characteristics of the subjects, sample size, and approaches used to measure satiety and food intake. Mechanisms by which sugars may signal regulatory systems for food intake need to be considered when evaluating both study designs and conclusions. For this reason, the relation between the blood glucose response to sugar consumption and subsequent feeding behavior is also examined. It is concluded that sugars stimulate satiety mechanisms and reduce food intake in the short term and that the mechanisms by which this response occurs cannot be attributed solely to their effect on blood glucose.     

Relationship between energy from added sugars and frequency of added sugars intake in Irish children, teenagers and adults

A WHO report on diet, nutrition and the prevention of chronic diseases recommended that frequency of consumption of foods and/or drinks containing free sugars should be limited to a maximum of four times per d. In addition, they recommended a reduction in the intake of free sugars to a maximum of no more than 10 % of energy intake. These recommendations were developed with the aim of reducing the prevalence of dental caries. The aim of the present study was to establish if there is a quantitative relationship between energy from added sugars and frequency of added sugars intakes in Irish children, teenagers and adults. In addition, the intake of added and total sugars and main contributors to added sugar intakes were examined. Data for the present analysis were based on the North/South Ireland Food Consumption Survey (n 1379; aged 18-64 years), the National Children's Food Survey (n 594; aged 5-12 years) and the National Teen Food Survey (n 441; aged 13-17 years) which used 7 d food diaries to collect food and beverage intake data in representative samples of Irish adults, children and teenagers respectively. Results showed that in adults, frequency of intake of added sugar intake of four times per d corresponded to a mean added sugar intake of 9 %, which was similar to the WHO recommendation. In children and teenagers, a frequency of intake of four times per d corresponded to a mean added sugar intake of 14.6 and 12.4 % respectively and was therefore not in agreement with the WHO recommendation.     

An assessment of liking for sugars using the estimated daily intake scale

Sugar is often used in learning and conditioning studies as an unconditioned stimulus (US) to enhance liking for a flavor mixed with it. To use sugar as a US, participants are selected only if they like the taste of sugar based on their ratings of a sweetened water US during a preexposure trial prior to experimental procedures. This US-only trail introduces a potential sensory bias and can lead to participant attrition when such a trial is conducted the day prior to experimental procedures. The aim of the present study was to construct a brief scale, called the Estimated Daily Intake Scale for Sugar (EDIS-S), to measure a participant's exposure to sugar in their diet. It was hypothesized that exposure to sugar would be positively correlated with liking for sugar. As expected, an 11-item EDIS-S was reliable and significantly correlated with ratings of liking for a sweetened taste solution. Implications for the use of the EDIS-S as an assessment in many areas of research, and as a participant selection tool for conditioning studies are discussed.     

以科学发展观引领疾病预防控制人才队伍建设

党的十七大作出了在全党开展深入学习实践科学发展观的战略部署,其目的就是要用科学发展观统领我们的各项工作,推进各行各业持续发展、全面发展。“坚持以人为本,树立全面、协调、可持续的发展观,促进经济社会和人的全面发展”,既是全面建设小康社会的根本指针,也是各行各业建设发展的指导思想。疾病预防控制机构履行的是公共卫生职能,公共卫生事业事关广大人民的身体健康和生命安全,人民健康是社会和谐发展的前提和基础。疾病预防控制机构是一个知识密集型机构,要发展必须依靠人才队伍建设。在新的形势下,疾病预防控制机构贯彻落实科学发展观,加强人才队伍建设,是自身发展的现实需要。     

Memory for recent eating and its influence on subsequent food intake

The effect of being reminded of a recent eating episode on subsequent food intake was examined in unrestrained eaters. In Experiment 1, female participants were exposed to a "lunch cue" (in which they were asked to think about what they had eaten for lunch), or "no cue" (free thought condition), for 5 min prior to eating. Participants ate less following exposure to the "lunch cue" than the "no cue" condition. In Experiment 2, food intake was measured following exposure to either a "lunch today" cue, "lunch yesterday" cue or "no cue" condition. Intake in the "lunch today" condition was suppressed relative to both the "lunch yesterday" and "no cue" condition. Subjective ratings of hunger, fullness, and desire to eat did not vary as a function of cue type in either Experiment 1 or Experiment 2. These results are consistent with the suggestion that memory of recent eating is an important cognitive factor influencing food intake.     

The scientific basis for population screening for breast cancer in the Netherlands

A recent Cochrane review stated that there was a lack of evidence for a decrease in mortality as a result of population breast-cancer screening. The principal data were drawn from five Swedish randomized controlled trials and one Canadian trial. However, the studies cannot be so easily combined because there were important differences in the attendance rate, detection rate, technical quality, referral rate, clinical baseline situation and screening interval. For example, in one of the studies the women from the control arm underwent an annual clinical palpation carried out by a trained nurse or physician, which could have led to an underestimation of the screening effect. Further breast-cancer mortality might not be a good outcome measure because this was not reliably determined; only total mortality was to be observed. This is clinically and methodologically incorrect because breast-cancer mortality was meticulously studied, documented and validated. In the Cochrane review it is suggested that the randomisation was inadequate, but evidence for this was not supplied. The discussion about age differences as a marker for incorrect randomisation is out of date and has been revealed to be unjust. It seems likely that an important part of the decreasing trend in breast-cancer mortality in several countries (including the Netherlands) is due to screening programmes. However, the evaluation of breast-cancer mortality over the next five years is crucial, if greater certainty is to be gained about this.     

A review of recent evidence relating to sugars,insulin resistance and diabetes

The potential impact on health of diets rich in free sugars, and particularly fructose, is of major concern. The focus of this review is the impact of these sugars on insulin resistance and obesity, and the associated risk of developing type 2 diabetes. Much of the concern is focussed on specific metabolic effects of fructose, which are argued to lead to increased fat deposition in the liver and skeletal muscle with subsequent insulin resistance and increased risk of diabetes. However, much of the evidence underpinning these arguments is based on animal studies involving very large intakes of the free sugars. Recent human studies, in the past 5 years, provide a rather different picture, with a clear dose response link between fructose intake and metabolic changes. In particular, the most marked effects are observed when a high sugars intake is accompanied by an excess energy intake. This does not mean that a high intake of free sugars does not have any detrimental impact on health, but rather that such an effect seems more likely to be a result of the high sugars intake increasing the chances of an excessive energy intake rather than it leading to a direct detrimental effect on metabolism.