Factors that may influence vitamin D nutritional status include latitude,season,age,sex,race,skin color,clothing,cultural practices,dietary nutrition,and living conditions.This article reviews the effects of these factors on vitamin D status and recommends that any high-risk people of vitamin D deficiency should take vitamin D supplementation.

2008,accordingly.

level and recommended nutrient intake)in China has been out-of-date.Therefore,it has became an urgent problem for Chinese Nutrition Society to re-evaluate the DRIs of vitamin D and make corresponding modifications.

Recent clinical studies have shown that collagen peptides may reduce joint pain and the dependence on analgesics,and enhance sport ability in athletes.Therefore,collagen peptides may be a safe nutrient supplement for prevention and mitigation of joint pain in athletes.

Large amounts of calcium are transferred from mother to fetus to meet the fetus's demand for calcium during its bone development.Pregnant women should increase the intake of calcium and vitamin D.However,the exact maternal vitamin D requirements and supplementation remain controversial.This article reviews the recent updates in this field with an attempt to provide evidences for nutritional decision-making.

Vitamin D deficiency is common among the elderly,which may be an important pathogenic factor in Alzheimer's disease(AD).Vitamin D has multiple functions including immune regulation,anti-oxidation,regulation of neurotrophic factors/acetylcholine neurotransmitters,and clearance of amyloid beta peptide; meanwhile,it may be helpful to avoid hyperparathyroidism.Vitamin D supplementation among the elderly may prevent the loss of neurons and slow down the AD-related cognitive decline,and therefore may play a role in the multi-targeted therapies for AD.

Many diseases are associated with vitamin D deficiency.Serum 25 (OH)D levels can serve as objective indicators of the nutritional status of vitamin D.Liquid chromatography-mass spectrometry (LC-MS) method may be applied for routine measurement of 25 ( OH ) D levels in clinical practice.This article reviewed the significance of detecting 25 (OH) D2 and 25 (OH) D3,compared the advantages and disadvantages of different 25 (OH) D measurement methods,and introduced the application of LC-MS method for routine detection of serum 25 (OH) D2 and 25 (OH) D3 levels following the standard by National Institute of Standards and Technology of America.

Objective To explore the relationship between serum 25 (OH)D level and cognitive function in patients with Alzheimer's disease (AD).Methods Totally 113 AD impatients were enrolled in this study.Their serum 25 (OH) D2,25 (OH) D3,and total 25 (OH) D levels were determined by liquid chromatography-tandem mass spectrometry (LC-MS/MS).Patients were divided into Vitamin D severe deficiency group [25 (OH)D level≤25 nmol/L],deficiency group [25 (OH)D levels:25-50 nmol/L],insufficiency group [25 (OH) D level:50-75 nmol/L],and sufficiency group [25 (OH) D level ≥ 75 nmol/L] according to the criteria proposed by US Institute of Medicine.The cognitive function was assessed by MMSE score.The association between serum 25 (OH) D level and cognitive function was systematically analyzed.Results The serum levels of 25 (OH) D,25 (OH) D2,and 25 (OH) D3 were (27.08 ± 15.33) nmol/L,(1.23 ± 0.93) nmol/L and (24.50 ± 13.04) nmol/L in AD patients.The proportions of severe deficiency,deficiency,insufficiency,and sufficiency were 60.18％ (68/113),30.97％ (35/113),7.97％ (9/113),and 0.88％ (1/113),respectively,among these AD patients.A positive correlation was found between serum 25 (OH) D concentration and MMSE score in AD patients.Conclusions Impatients with AD often have severe vitamin D deficiency and need vitamin D supplementation.Serum 25 (OH) D concentration is associated with cognitive function,and therefore vitamin D supplementation may improve cognitive function.