Objectives:
Can vitamin D-fortified products be a suitable solution for tackling vitamin D deficiency in adults?

Study design:
This review article included 23 studies.

Results and conclusions:
The investigators found pooled data comparing fortification with vitamin D +/- Ca with control showed statistically significant effect on total 25(OH)D concentrations [MD = 25.4 nmol/L, 95% CI = 19.5 to 31.3, n = 2,002 participants].

Objectives:
Females generally have higher antibody responses to viral vaccines. Therefore, this review article has been conducted.

Are there gender differences in the efficacy of the COVID-19 vaccines?

Study design:
This review article included 4 eligible trials with 643,127 participants. All studies were categorized as having a low risk of bias.

Results and conclusions:   
The investigators found COVID-19 vaccine was significantly effective in both males and females.

Objectives:
What is the association between red meat and poultry consumption and the risk of metabolic syndrome?

Study design:
This review article included 9 prospective cohort studies, which involved a total of 21,869 participants.
Among them, 8 studies were identified for red meat consumption.

No publication bias was observed according to the Begg's rank-correlation test and the Egger's test.  

Objectives:
It has been theorized that folic acid supplementation improves inflammation. However, its proven effects on inflammatory markers are unclear as clinical studies on this topic have produced inconsistent results. Therefore, this review article has been conducted.

Objectives:
What is the efficacy of vitamin D fortification and supplementation in children?

Study design:
This review article included 31 studies.

Results and conclusions:
The investigators found significant raises in circulating 25(OH)D concentrations were observed in both groups that took vitamin D supplement [MD = 28.7, 95% CI = 22.5 to 34.9] and vitamin D-fortified foods [MD = 20.29, 95% CI = 13.3 to 27.2].

Objectives:
Does vitamin D deficiency increase the risk of infection, severity and mortality of COVID-19?

Study design:
This review article included 23 eligible studies involving the relationship between vitamin D and Covid-19 infection/outcomes with a total of 206,861 participants.

Objectives:
Potential effects of inositol supplementation on blood pressure (BP) have been examined in several interventional studies. Nevertheless, findings in this context are controversial. Therefore, this review article has been conducted.

Do inositol supplements reduce blood pressure in humans?

Study design:
This review article included 7 eligible RCTs.

Objectives:
Does fruits and vegetables (FVs) consumption reduce risk of frailty?

Study design:
This review article included 10 cohort studies and 4 cross-sectional studies with 18,616 subjects with frailty and 101,969 controls (persons without frailty).

Based on the NutriGrade score, the quality of evidence for a protective effect of fruits and vegetables consumption on frailty was "moderate".

Objectives:
Do HPV vaccines reduce risk of HPV-related oropharyngeal cancer?

Study design:
This review article included 2 randomized controlled trials (RCTs) and 4 cross-sectional studies with a total of 15,240 participants.

Results and conclusions:
The investigators found in a meta-analysis that vaccinated individuals were 46% [risk ratio = 0.54, 95% CI = 0.32 to 0.91, p = 0.02] less likely to develop oral vaccine-type HPV infection compared to controls.  

Objectives:
Previous meta-analysis studies have indicated inverse associations between some carotenoids and risks of metabolic syndrome, cardiovascular disease, cancer and all-cause mortality. However, the results for associations between carotenoids and type 2 diabetes (T2D) remain inconsistent and no systematic assessment has been done on this topic. Therefore, this review article (meta-analysis) has been conducted.

Do higher dietary intakes and circulating concentrations of carotenoids reduce risk of type 2 diabetes?