Vitamin D Nutrient Summary

In this article, we’ll delve into the latest evidence on Vitamin D, outlining sources of vitamin D, deficiency implications and recommended intake guidelines. 

Vitamin D (calciferol) is a fat-soluble micronutrient that plays a role in bone health, muscle function, cognition, and immune health (1). 

Vitamin D has earned the nickname “the sunshine vitamin” due to its unique synthesis in the skin upon exposure to sunlight. There are very few naturally occurring food sources of vitamin D including fatty fish, fish liver oil, some mushrooms, as well as fortified foods (1,2).

A comprehensive list of food sources of vitamin D can be found in DSC’s Food Sources of Nutrients Compilation.

For a full vitamin D evidence summary join Dietitian Success Center’s membership. The membership includes access to comprehensive yet simplified reference guides for supplements, food sources lists, and client-facing handouts for many nutrients, including vitamin D. 

Vitamin D Deficiency

Individuals at greatest risk of vitamin D deficiency are typically those who do not receive adequate sun exposure for vitamin D synthesis in addition to inadequate synthesis of vitamin D once exposed. 

This may include (1,3):

• Individuals with low or no sun exposure.
• Individuals with dark skin
• Older adults (the ability to synthesize vitamin D from sunlight decreases with age and can also be due to less time spent outdoors).
• Individuals with fat malabsorption (IBD, unmanaged celiac disease). 
• Individuals classified as obese based on BMI ≥ 30 (high amounts of adipose tissue can sequester and trap vitamin D, reducing its availability for use in the bloodstream). 
• Exclusively breastfed infants (breastmilk may not contain sufficient vitamin D to meet infant’s requirements, supplementation is recommended in many countries).
• Persons taking medications that can limit vitamin D absorption and blood levels including: Orlistat (weight-loss drug), cholesterol-lowering statins, steroids, and thiazide diuretics (1). 

Recommending Vitamin D Supplements

Guidelines for vitamin D supplementation remain controversial. Multiple factors should be assessed before determining a supplementation regimen for each individual’s unique health concerns. 

Current evidence suggests the following general guidelines:

• Choose a vitamin D3 supplement over vitamin D2 whenever possible (4).
• Consider a dose of 400-2000 IU supplemental vitamin D3 daily.
• Consider higher doses (approximately 800-2000 IU daily) for older adults and individuals with limited sun exposure (5,6). 
• Consider higher doses for individuals in larger bodies: 1.47 times higher dose for BMI 25-29.9 and 2.6 times higher for BMI ≥30 (7).
• Infants consuming exclusively human milk (breast milk) are recommended, in many countries, to take a 400 IU vitamin D supplement drop daily. In some cases, lactating individuals may take a daily ≥4000 IU supplement level to provide adequate vitamin D to the breastfeeding infant, though the evidence is currently very uncertain (8). 
• Avoid supplemental doses >10,000 IU per day. Notably, toxicity is rare at doses of 10,000 IU per day and more common at doses of 50,000 IU per day (2). 
• Consider the client’s sun exposure levels, 25(OH)D levels and intake from food and other supplements to determine required amounts (3). 

Because the research is shifting rapidly, these guidelines may not be appropriate for all individuals.

Key Takeaways

• Vitamin D is important for bone, muscle, cognitive, and immune health.
• Often called the “sunshine vitamin”, vitamin D can be absorbed through sun exposure as well as a few dietary sources, including fatty fish, fish liver oil, some mushrooms, as well as fortified foods.
• Individuals with limited ability to absorb vitamin D from sunlight, or with medical considerations outlined above, may require supplementation to prevent deficiency.

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Disclaimer: the information provided in all written materials is for educational purposes only and is not to be used as medical advice or to diagnose or treat a medical disease. It is strictly for informational purposes and is general in nature. Dietitian Success Center Inc. is not responsible and cannot be held liable for any actions or inactions taken related to the information provided. Consult with your local medical provider before implementing any dietary changes. It is hereby understood that the information provided does not replace medical advice provided by your healthcare provider.

References

1. National Institutes of Health. “Vitamin D – Health Professional Fact Sheet”. NIH Office of Dietary Supplements. Available from https://ods.od.nih.gov/factsheets/VitaminD-HealthProfessional/ 
2. Institute of Medicine. 2011. Dietary Reference Intakes for Calcium and Vitamin D. Washington, DC: The National Academies Press. https://doi.org/10.17226/13050.
3. Holick MF. Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease. Am J Clin Nutr. 2004 Dec;80(6 Suppl):1678S-88S. doi: 10.1093/ajcn/80.6.1678S. PMID: 15585788.
4. Liu C , Kuang X , Li K , Guo X , Deng Q , Li D . Effects of combined calcium and vitamin D supplementation on osteoporosis in postmenopausal women: a systematic review and meta-analysis of randomized controlled trials. Food Funct. 2020 Dec 1;11(12):10817-10827. doi: 10.1039/d0fo00787k. Epub 2020 Nov 25. PMID: 33237064.
5. Weaver CM, Alexander DD, Boushey CJ, Dawson-Hughes B, Lappe JM, LeBoff MS, Liu S, Looker AC, Wallace TC, Wang DD. Calcium plus vitamin D supplementation and risk of fractures: an updated meta-analysis from the National Osteoporosis Foundation. Osteoporos Int. 2016 Jan;27(1):367-76. doi: 10.1007/s00198-015-3386-5. Epub 2015 Oct 28. 
6. International Osteoporosis Foundation. “Vitamin D” 2023. Available from https://www.osteoporosis.foundation/patients/prevention/vitamin-d
7. Ekwaru JP, Zwicker JD, Holick MF, Giovannucci E, Veugelers PJ. The importance of body weight for the dose response relationship of oral vitamin D supplementation and serum 25-hydroxyvitamin D in healthy volunteers. PLoS One. 2014 Nov 5;9(11):e111265. doi: 10.1371/journal.pone.0111265. PMID: 25372709; PMCID: PMC4220998.
8. Tan ML, Abrams SA, Osborn DA. Vitamin D supplementation for term breastfed infants to prevent vitamin D deficiency and improve bone health. Cochrane Database Syst Rev. 2020 Dec 11;12(12):CD013046. doi: 10.1002/14651858.CD013046.pub2. PMID: 33305822; PMCID: PMC8812278.