The dietary requirement for an essential trace element is an intake level which meets a specified criterion for adequacy and thereby minimizes risk of nutrient deficiency or excess. Disturbances in trace element homeostasis may result in the development of pathologic states and diseases. This article is an update of a review article “ Trace Elements in Human Nutrition-A Review” previously published in 2013. The previous review was updated to emphasis in detail the importance of known trace elements so far in humans’ physiology and nutrition and also to implement the detailed information for practical and effective management of trace elements’ status in clinical diagnosis and health care situations. Although various classifications for trace elements have been proposed and may be controversial, this review will use World Health Organization( WHO) classification as previously done. For this review a traditional integrated review format was chosen and many recent medical and scientific literatures for the new findings on bioavailability, functions, and state of excess/deficiency of trace elements were assessed. The results indicated that for the known essential elements, essentiality and toxicity are unrelated and toxicity is a matter of dose or exposure. Little is known about the essentiality of some of the probably essential elements. In regard to toxic heavy metals, a toxic element may nevertheless be essential. In addition, the early pathological manifestations of trace elements deficiency or excess are difficult to detect until more specific pathologically relevant indicators become available. Discoveries and many refinements in the development of new techniques and continual improvement in laboratory methods have enabled researchers to detect the early pathological consequences of deficiency or excess of trace elements. They all are promises to fulfill the gaps in the present and future research and clinical diagnosis of trace elements deficiencies or intoxications. However, further investigations are needed to complete the important gaps in our knowledge on trace elements, especially probably essential trace elements’ role in health and disease status.

Introduction: Nutrition Clinical Trials (NCTs) are pivotal in establishing causal links between nutritional interventions and chronic diseases. This review comprehensively examines prevalent clinical trial designs, emphasizing their strengths and limitations. The goal is to provide insights into the selection and optimization of these designs for dietary intervention studies. Methods: Various study designs in NCTs are explored, including quasi-experimental designs, double-blind randomized placebo-controlled trials for nutrient/functional foods supplementation, community-based lifestyle interventions, pragmatic nutrition interventions, and field trial projects. The characteristics, advantages, and challenges of each design are discussed. Real examples are presented to illustrate how these designs can be tailored and optimized for dietary intervention studies. Results: Parallel randomized clinical trials are acknowledged as the gold standard, despite requiring substantial sample sizes and having inherent limitations. Cross-over NCTs emerge as valuable for assessing temporary treatment effects while mitigating potential confounders and interpatient variability. However, they may not be suitable for acute diseases and progressive disorders, and attrition rates can be higher. Multi-arm randomized designs offer increased study power with a lower sample size but necessitate more intricate design, analysis, and result reporting. Conclusion: In conclusion, each study design in NCTs comes with its set of strengths and limitations. The selection of an appropriate design should consider determinants and common considerations to provide robust evidence for establishing cause-and-effect associations or assessing the safety and efficacy of food products in nutrition research. This comprehensive understanding aids researchers in making informed choices when planning and conducting nutrition clinical trials.

Proper nutrition of mother plant plays an important role in the production of seeds with high vigor. Therefore, a factorial experiment was done in a completely randomized design with 12 treatments and 3 replications to study the germination characteristics of cumin seeds which harvested from mother plants treated with different amounts of vermicompost and mycorrhiza fertilizers, in the Faculty of Agriculture, Yasouj University, Iran, in 2013. Vermicompost treatments consisted of three levels (0, 5 and 10 tons per hectare), and mycorrhiza fungi consisted of 4 levels (control, inoculation with Glomusmossae, inoculation with Glomusintraradices and inoculation with both species). For most of the germination traits, as well as seed nitrogen and phosphorus content, the effects of vermicompost and mycorrhiza were significant. Results showed that the highest radicle length (2. 57 cm), plumule length (1. 61 cm) and vigor index (3. 069) of the seeds was achieved by application of 10 ton vermicompost with G. mosseae, the highest seed nitrogen and phosphorus content observedin the application of 10 tons of vermicompost plus inoculation with two fungi, the largest seedling length was observed in application of 10 ton/ha vermicompost without mycorrhiza, the highest germination rate in the treatment of application 5 ton vermicompost without mycorrhiza and the highest germination percentage were obtainedin treatment of 5 tons vermicompost and G. mosseaeOverall, the results of this experiment showed that application of vermicompost and mycorrhiza especially combined treatment of 10 ton/ha verrmicompost plus G. mosseae and G. intraradices could increase uptake of nutritional elements such as nitrogen and phosphorous to seeds and therefore enhance germination performance in cumin seeds.