• Vitamin D is a hormone precursor that is present in 2 forms. Ergocalciferol or vitamin D2, is present in plants and some fish. Cholecalciferol or vitamin D3, is synthesized in the skin by sunlight, at UVB wavelengths of 290-315 nm.
• Exposure of human skin to solar UVB radiation leads to the conversion of 7-dehydrocholesterol to previtamin D3 in the skin. Previtamin D3 is then rapidly converted to vitamin D3 by temperature- and membrane-dependent processes.

Objectives:
Arthritis patients often take fish oil supplements to alleviate symptoms, but limited evidence exists regarding their efficacy. Therefore, this meta-analysis (systematic review) has been conducted.

Do taking marine oil supplements alleviate pain in arthritis patients?

Study design:
This review article included 42 randomized trials; 30 trials reported complete data on pain.

• EPA and DHA are n-3 fatty acids or omega-3 fatty acids.
• In humans, EPA and DHA are synthesized from the n-3 essential fatty acid, alpha-linolenic acid (ALA, 18:3n-3). Therefore, they are not strictly essential for the human body.
  However, the human body converts only 10-15% of ALA to EPA and EPA to DHA. For this reason, EPA and DHA are also regarded as essential fatty acids.

Objectives:
Vitamin B12 deficiency in pregnancy is prevalent and has been associated with both lower birth weight (birth weight 2,500 g) and preterm birth (length of gestation 37 weeks). Nevertheless, current evidence is contradictory. Therefore, this meta-analysis (systematic review) has been conducted.

Is there an association between maternal serum or plasma vitamin B12 concentrations in pregnancy and offspring birth weight and length of gestation?

• Vitamin B12 (cobalamin, Cbl) is a water-soluble vitamin.

Objectives:
The associations between dietary zinc and iron intake and risk of depression remain controversial. Therefore, this meta-analysis (systematic review) has been conducted.

Do dietary zink and iron intake decrease risk of depression?

Study design:
This review article included a total of 9 studies for dietary zinc intake and 3 studies for dietary iron intake. 

• There are different types of scientific studies. In increasing scientific evidence are:

1. Cell culture at petri dishes or in a test tube, also called in vitro study. In vitro is Latin for glass.
2. Animal study  or in vivo study. In vivo is Latin for life.
3. Human study or clinical trial. These are studies in humans. There are several human studies.

• Zinc is an essential mineral.
• Lean red meat, wholegrain cereals and legumes provide the highest concentrations of zinc, generally in the range of 2.5-5.0 mg per 100 g raw weight.
• Wholegrain breads and cereals, rolled oats, brown rice, nuts, seeds, legumes, tofu, soy products and fortified breakfast cereals are important dietary sources of zinc for everyone.
• Zinc is an essential constituent of more than 300 metalloenzymes.

Objectives:
Different adiposity measures have been associated with increased risk of atrial fibrillation, however, results have previously only been summarized for BMI. Therefore, this review article (meta-analysis) has been conducted.

Is there an association between different adiposity measures and risk of atrial fibrillation?

Study design:
This review article included 25 prospective studies with 83,006 cases among 2,405,381 participants.

Objectives:
Creatine is the most widely used supplementation to increase performance in strength; however, the most recent meta-analysis focused specifically on supplementation responses in muscles of the lower limbs without regard to upper limbs. Therefore, this review article (meta-analysis) has been conducted.

Does creatine supplementation increase strength performance of upper limb for exercise with a duration of less than 3 minutes?