Objectives:
Manganese (Mn) is one of the most studied environmental heavy metals linked to Alzheimer’s disease (AD). However, it remains unclear whether serum manganese levels are associated with Alzheimer’s disease and mild cognition impairment (MCI, a prodromal stage of AD). Therefore, this meta-analysis (review article) has been conducted.

Does a lower serum manganese level increase risk of cognitive decline?

• Molybdenum is a trace mineral.
• Nuts, grains, cauliflower and leafy vegetables are good sources, whereas animal products and fruit are low in molybdenum.
• Molybdenum content of plant-based foods is dependent on the amount of molybdenum in the soil in which they are grown.
• Molybdenum is a cofactor for 4 important enzymes: xanthine oxidase/dehydrogenase, sulfite oxidase and aldehyde oxidase.

Objectives:
Although circumstantial evidence accumulated to support the hypothesis that Glucose-6-Phosphate Dehydrogenase (G6PD) deficiency is protective against severe fatal malaria; there have been several arguments for and against. Therefore, this meta-analysis (review article) has been conducted.

Is there an association between G6PD deficiency and uncomplicated P. falciparum malaria and malaria negative individuals?

Objectives:
Does diabetes increase risk of incident dementia and mild cognitive impairment?

Study design:
This review article included 19 prospective longitudinal studies including 6184 subjects with diabetes and 38530 subjects without diabetes. All subjects were without dementia or mild cognitive impairment at baseline (=at the beginning of the study).

There was no publication bias.

Objectives:
In view of the vital role of oxidative stress in the pathogenesis of Alzheimer's disease (AD), the potential of antioxidant supplements to prevent AD have gained much interest, while there are conflicting results on this topic in recent years. Therefore, this review article has been conducted.

Does dietary intake of vitamin C and E and β-carotene decrease risk of Alzheimer's disease?

Study design:
This review article included 7 articles (dietary intake, but no supplements).

Objectives:
The association between dietary vitamin K intake and the risk of fractures is controversial. Therefore, this meta-analysis (review article) has been conducted.

Does dietary vitamin K intake reduce risk of fractures?

Objectives:
There is an ongoing debate on the involvement of systemic copper (Cu) dysfunctions in Alzheimer's disease (AD) and clinical studies comparing Cu levels in serum, plasma and cerebrospinal fluid (CSF) of AD patients with those of healthy controls have delivered non-univocal and often conflicting results. Therefore, this review article has been conducted.

Does blood level of copper increase in Alzheimer’s disease?

Scientific studies (review articles) on the relationship between diet/nutrients and dementia prevention:
One swallow does not make a summer. A famous Dutch saying that could not be any more obvious. Just because one single scientific study about a certain topic makes certain claims, it does not necessarily mean it is true. On the other hand, a review article (a collection of scientific studies on a certain topic) of randomized, placebo-controlled double blind clinical trials (RCTs) will answer the following question:

Objectives:
Zinc sulfate may be a promising approach to treat neonatal jaundice. However, the results remain controversial. Therefore, this review article (meta-analysis) has been conducted.

Does zinc sulfate supplementation reduce neonatal jaundice?

Objectives:
Does physical activity reduce gastric cancer risk?

Study design:
This review article included 7 cohort studies (with mean reported follow-up ranging from 6 to 18.8 years) and 9 case control studies reporting 11,111 cases of gastric cancer among 1,606,760 patients.

There was no evidence of publication bias, both quantitatively [Begg and Mazumdar rank correlation test, p = 0.62] and qualitatively, on visual inspection of the funnel plot.