Adequate vitamin D levels are defined as having blood levels of vitamin D (25(OH)D) in the range of 50-125 nmol/L (12-20 ng/mL).[1] The only way to determine vitamin D status is through a blood test.
Where you live may influence your risk of Vitamin D deficiency. Vitamin D synthesis rates tend to vary with geographical location, which influences the amount of UVB exposure from the sun. People further away from the equator have lower rates of vitamin D synthesis,[2] and weather patterns associated with more cloud cover and darkness also can also reduce how much vitamin D is made through sun exposure.[3]
Breastfeeding[4] - see “Should vitamin D supplements be given to infants and children?” below.
Medical conditions that limit the absorption of dietary fats.[5] As a fat-soluble vitamin, the absorption of vitamin D is dependent on the ability of the gut to absorb fats from the diet.[6]
Dark skin pigmentation. Darker skin color reduces absorption of UVB, limiting production of vitamin D by the skin during sunlight exposure.[1]
Obesity. People with obesity (defined as a BMI of 30 or more) tend to have lower vitamin D levels compared to people without obesity, which is thought to be caused by an increased sequestration of vitamin D in subcutaneous fat stores.[1]
Gastric bypass surgery. During gastric bypass surgery, parts of the gastrointestinal tract that absorb vitamin D are bypassed, limiting absorption and potentially causing a deficiency.[7][8]
Aging. The ability to make vitamin D in the skin during sun exposure decreases with age, by an amount of 13% per decade, according to one study comparing vitamin D synthesis after a single incidence of sun exposure in younger and older adults.[9]
References
- ^ A. Catharine Ross, Christine L. Taylor, Ann L. Yaktine, and Heather B. Del Valle. The National Academies Press; Washington, D.C. Dietary Reference Intakes for Calcium and Vitamin D (2011). The National Academies Press; Washington, D.C..(2011)
- ^Kimlin MGGeographic location and vitamin D synthesis.Mol Aspects Med.(2008-Dec)
- ^Engelsen O, Brustad M, Aksnes L, Lund EDaily duration of vitamin D synthesis in human skin with relation to latitude, total ozone, altitude, ground cover, aerosols and cloud thickness.Photochem Photobiol.(2005)
- ^Wagner CL, Greer FR, ,Prevention of rickets and vitamin D deficiency in infants, children, and adolescents.Pediatrics.(2008-Nov)
- ^Pappa HM, Bern E, Kamin D, Grand RJVitamin D status in gastrointestinal and liver disease.Curr Opin Gastroenterol.(2008-Mar)
- ^Mariana Costa Silva, Tania Weber FurlanettoIntestinal absorption of vitamin D: a systematic reviewNutr Rev.(2018 Jan 1)
- ^Chakhtoura M, Rahme M, El-Hajj Fuleihan GVitamin D Metabolism in Bariatric Surgery.Endocrinol Metab Clin North Am.(2017-Dec)
- ^Peterson LA, Zeng X, Caufield-Noll CP, Schweitzer MA, Magnuson TH, Steele KEVitamin D status and supplementation before and after bariatric surgery: a comprehensive literature review.Surg Obes Relat Dis.(2016)
- ^Jenna R Chalcraft, Linda M Cardinal, Perry J Wechsler, Bruce W Hollis, Kenneth G Gerow, Brenda M Alexander, Jill F Keith, D Enette Larson-MeyerVitamin D Synthesis Following a Single Bout of Sun Exposure in Older and Younger Men and WomenNutrients.(2020 Jul 27)