Objectives:
Seventeen per cent of the world's population is estimated to be at risk of inadequate zinc intake, which could in part be addressed by zinc fortification of widely consumed foods. Therefore, this review article has been conducted.

Objectives:
The efficacy and safety of L‐arginine supplements and their effect on maximal oxygen uptake (VO2 max) remained unclear. Therefore, this review article has been conducted.

Does supplementation with arginine increase VO2 max in healthy people?

Objectives:
D-dimer elevations, suggesting a pro-thrombotic state and coagulopathy, predict adverse outcomes in coronavirus disease 2019 (COVID-19). However, the clinical significance of other coagulation markers, particularly the international normalized ratio (INR), is not well established. Therefore, this review article has been conducted.

Objectives:
Do vegetarians and vegans have a lower bone mineral density than omnivores?

Study design:
This review article included 17 cross-sectional studies with a total of 13,888 patients.

Objectives:
The numbers of confirmed cases of coronavirus disease 2019 (COVID-19) and COVID-19 related deaths are still increasing, so it is very important to determine the risk factors of COVID-19. Dyslipidemia is a common complication in patients with COVID-19, but the association of dyslipidemia with the severity and mortality of COVID-19 is still unclear. Therefore, this review article has been conducted.

Objectives:
What are the risk factors of leprosy in contacts?

Study design:
This review article included 23 cohort studies and 1 cross-sectional study.
Most of the studies had been conducted in Brazil and India.
The follow-up period ranged from 1 to 20 years and the publication covered the period from 1991 to 2019.
The sample ranged from 68 to 28,092 participants.
19 cohorts (79%) scored ≥ 7, indicating a low risk of bias.

Objectives:
Does calcium reduce the risk of incidence and recurrence of colorectal adenomas and advanced adenomas?

Study design:
This review article included 37 relevant clinical trials and observational studies involving over 10,964 cases.

Results and conclusions:
The investigators found that calcium consumption significantly reduced the risk of colorectal adenomas incidence by 8% [RR = 0.92, 95% CI = 0.89 to 0.96].

Objectives:
Do critically ill patients benefit of thiamine (vitamin B1) supplementation?

Study design:
This review article included 8 RCTs and 10 cohort studies.

Results and conclusions:
The investigators found in the analysis of RCTs, that thiamine supplementation showed a significantly 42% lower odds of developing ICU delirium [OR = 0.58, 95% CI = 0.34 to 0.98].

Objectives:
There appears to be a sex-specific association between obesity and colorectal neoplasia in patients with Lynch Syndrome (LS). Therefore, this review article has been conducted.

Objectives:
Clinical symptoms of adults and paediatric inpatients with COVID-19 disease are conflicting. Therefore, this review article has been conducted.

What is the effect of age on the severity in COVID-19 inpatients?

Study design:
This review article included 5 studies with 910 inpatients with COVID-19 disease at the baseline of the study. 773 of them were adult inpatients and 137 of them were paediatric inpatients (infants, children and adolescents).