在进化过程中,人类一直依靠照射阳光满足其维生素 D 的需要。这是为什么维生素D食物来源如此缺乏的可能原因。实际上不可能单独从食物来源(自然来源和维生素 D 强化食物)获取足够的维生素 D。因此,所有儿童和成人进行适量日照并进行充足维生素 D 补充,会预防在一般人群中的维生素 D 缺乏症/不足,最大限度地提高骨健康和降低维生素 D 缺乏症/不足症有关的多种慢性疾病的风险。但是,由于种种原因,甚至在全球阳光最充足的地方,包括中东、印度、哥伦比亚、墨西哥、巴西和澳大利亚,因日照不足而引起的维生素 D 缺乏症和不足症也很常见。[1]Hossein-Nezhad A, Holick MF. Vitamin D for health: a global perspective. Mayo Clin Proc. 2013;88:720-755.http://www.mayoclinicproceedings.org/article/S0025-6196(13)00404-7/fulltexthttp://www.ncbi.nlm.nih.gov/pubmed/23790560?tool=bestpractice.com所需的日照量取决于白天的时间、季节、纬度(维生素 D 不能在冬季合成,除非住在低于纬度 35° 左右的地区)和皮肤色素。[1]Hossein-Nezhad A, Holick MF. Vitamin D for health: a global perspective. Mayo Clin Proc. 2013;88:720-755.http://www.mayoclinicproceedings.org/article/S0025-6196(13)00404-7/fulltexthttp://www.ncbi.nlm.nih.gov/pubmed/23790560?tool=bestpractice.com[57]Webb AR, DeCosta BR, Holick MF. Sunlight regulates the cutaneous production of vitamin D3 by causing its photodegradation. J Clin Endocrinol Metab. 1989;68:882-887.http://www.ncbi.nlm.nih.gov/pubmed/2541158?tool=bestpractice.com[72]Rajakumar K, Fernstrom JD, Holick MF, et al. Vitamin D status and response to vitamin D(3) in obese vs. non-obese African American children. Obesity. 2008;16:90-95.http://onlinelibrary.wiley.com/doi/10.1038/oby.2007.23/fullhttp://www.ncbi.nlm.nih.gov/pubmed/18223618?tool=bestpractice.com
美国儿科学会推荐从出生到儿童期维生素 D 摄入量为 400 IU/天。[73]Wagner CL, Greer FR; American Academy of Pediatrics Section on Breastfeeding. Prevention of rickets and vitamin D deficiency in infants, children, and adolescents. Pediatrics. 2008;122:1142-1152. [Erratum in: Pediatrics. 2009;123:197.]http://pediatrics.aappublications.org/content/122/5/1142.longhttp://www.ncbi.nlm.nih.gov/pubmed/18977996?tool=bestpractice.com医学研究所(IOM)推荐 0-12 个月的婴儿服用维生素 D 400 IU/天,1 岁及以上的儿童和成人服用维生素 D 600 IU/天。[74]Institute of Medicine. Report brief - dietary reference intakes for calcium and vitamin D. November 2010. http://www.iom.nationalacademies.org/ (last accessed 14 November 2016).http://iom.nationalacademies.org/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D/Report-Brief.aspx此外,基于现有文献,IOM 推荐 0-6 个月的婴儿和 6-12 个月的婴儿每天维生素 D 的上限分别为 1000 和 1500 IU。对 1-3 岁儿童和 4-8 岁儿童每天维生素 D 的上限分别升高至 2500 IU 和 3000 IU。对于超过 8 岁的儿童和所有成人,每天维生素 D 的上限升至 4000 IU。[74]Institute of Medicine. Report brief - dietary reference intakes for calcium and vitamin D. November 2010. http://www.iom.nationalacademies.org/ (last accessed 14 November 2016).http://iom.nationalacademies.org/Reports/2010/Dietary-Reference-Intakes-for-Calcium-and-Vitamin-D/Report-Brief.aspx对于 1 岁以下的婴儿,大约 1000 IU 是安全的,对于 1 岁及 1 岁以上的儿童,2000 IU 是安全的。[1]Hossein-Nezhad A, Holick MF. Vitamin D for health: a global perspective. Mayo Clin Proc. 2013;88:720-755.http://www.mayoclinicproceedings.org/article/S0025-6196(13)00404-7/fulltexthttp://www.ncbi.nlm.nih.gov/pubmed/23790560?tool=bestpractice.com[12]Gordon CM, DePeter KC, Feldman HA, et al. Prevalence of vitamin D deficiency among healthy adolescents. Arch Pediatr Adolesc Med. 2004;158:531-537.http://archpedi.jamanetwork.com/article.aspx?articleid=485739http://www.ncbi.nlm.nih.gov/pubmed/15184215?tool=bestpractice.com[75]El-Hajj Fuleihan G, Nabulsi M, Tamim H, et al. Effect of vitamin D replacement on musculoskeletal parameters in school children: a randomized controlled trial. J Clin Endocrinol Metab. 2006;91:405-412.http://press.endocrine.org/doi/full/10.1210/jc.2005-1436http://www.ncbi.nlm.nih.gov/pubmed/16278262?tool=bestpractice.com正常体重的成人,每服下100 IU 维生素 D,血清 25-羟基维生素 D 水平大约升高1 ng/mL。[76]Holick MF, Biancuzzo RM, Chen TC, et al. Vitamin D2 is as effective as vitamin D3 in maintaining circulating concentrations of 25-hydroxyvitamin D. J Clin Endocrinol Metab. 2008;93:677-681.http://press.endocrine.org/doi/full/10.1210/jc.2007-2308http://www.ncbi.nlm.nih.gov/pubmed/18089691?tool=bestpractice.com因此,为让血清 25-羟基维生素 D 水平达到>75 nmol/L (>30 ng/mL),所需维生素 D 的量为2000-3000 IU/天。肥胖成人(BMI>30)需要正常每天推荐剂量的 2-3 倍来达到相同的水平。[1]Hossein-Nezhad A, Holick MF. Vitamin D for health: a global perspective. Mayo Clin Proc. 2013;88:720-755.http://www.mayoclinicproceedings.org/article/S0025-6196(13)00404-7/fulltexthttp://www.ncbi.nlm.nih.gov/pubmed/23790560?tool=bestpractice.com[4]Holick MF, Binkley NC, Bischoff-Ferrari HA, et al. Evaluation, treatment and prevention of vitamin D deficiency: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2011;96:1911-1930.http://press.endocrine.org/doi/10.1210/jc.2011-0385http://www.ncbi.nlm.nih.gov/pubmed/21646368?tool=bestpractice.com
[Figure caption and citation for the preceding image starts]: 维生素 D 来源作者:M.F.Holick,PhD,MD;经许可后使用 [Citation ends].