Vitamin D: Why You Need It & How to Get It

Did you know that getting just 10 minutes of sunshine (ultraviolet B, or UVB) per day helps the body create approximately 10,000 IU of vitamin D?1 This nutrient is necessary for the health of your bones, as well as overall health.2 However, during the months of November through February, and if you live north of Atlanta, there won’t be enough UVB rays to penetrate through the atmosphere and help your skin generate this vital nutrient. So is there something you can do?

Sometimes you just have to create your own sunshine. And considering that three-quarters of teens and adults in the United States are deficient in vitamin D,3 as well as 1 billion people worldwide,4 this is where supplemental vitamin D can really help. Natural dietary sources of vitamin D are few (e.g. fatty fish, eggs), and fortified dietary sources such as milk, orange juice and cereal provide minimal amounts of vitamin D. This is why vitamin D is one of the most common nutrient gaps and also one of the easiest to address via supplementation.

Why is vitamin D important?

Vitamin D is a fat-soluble vitamin that regulates bone growth and mineralization and plays an important role in ensuring the muscles, heart, lungs, and brain function properly.2  Vitamin D has also been shown to support immune function. Vitamin D is not only an essential vitamin but also acts as a hormone in the body. Vitamin D that you obtain from the sun, food, beverage, or supplements must be first activated by the liver which converts the vitamin D to 25-hydroxyvitamin D (25(OH)D), also known as calcidiol.2 It is then converted by the kidneys and target tissues in the body to the biologically active form 1,25-dihydroxyvitamin D (1,25(OH)2D), also known as calcitriol.2 Calcitriol is the active, hormone form, which supports a variety of physiological functions, including helping the body regulate levels of calcium and phosphorus, as well as mineralize bone.5

Vitamin D deficiency

What does it mean to be deficient in vitamin D? Measuring serum concentrations of 25(OH)D rather than 1,25(OH)2D is a better indicator of vitamin D status in the body due to its longer half life. Certain groups define vitamin D deficiency as 25(OH)D level less than 20 ng/mL (50 nmol/L).6

Vitamin D deficiency can be an issue for many people, including:7

  • Adults over 65
  • Vegetarians
  • Individuals with darker pigmentation
  • Overweight/obesity
  • Those with certain medical conditions
  • Those who take certain medications
  • Those who have limited sun exposure

Finding out if you need more vitamin D

Measuring your vitamin D levels via a blood test is the only way to definitively know if you’re getting enough of this nutrient. With a 25(OH)D blood test from your healthcare practitioner, you will know your vitamin D levels and whether you need to take a supplement. Optimal levels of vitamin D vary according to different scientific organizations. For example, for adults the Vitamin D Council recommends daily supplementation with 5,000 IU of vitamin D3 when you cannot get enough sun to achieve a status between 40-60 ng/ml; whereas, the Endocrine Society recommends 1500-2000 IU/day.7-8 Higher levels are recommended to address deficiency.8 It is also important to recheck vitamin D levels two months after beginning a supplement regimen, and adjust as needed based on your practitioner’s recommendations.

Which D is right for me?

It’s important to get the form of vitamin D that is most bioavailable to the body. There are two kinds of vitamin D—D2 and D3. Vitamin D2 (ergocalciferol), is found in plants such as lichens and mushrooms, which are often irradiated by growers to boost nutritional value. Some soy and almond milks are also fortified with vitamin D2.

Vitamin D3 (cholecalciferol) is the natural form of this nutrient that is created by the body with sun exposure, and research has shown that the D3 form increases the total circulating level of 25(OH)D significantly more effectively than D2.9-10 Vitamin D3 is found in small amounts in oily fish such as cod and salmon, egg yolks, as well as fortified cereals and milk, and some commercial mushrooms. Additionally, vitamin D3 has been shown to maintain adequate amounts of serum vitamin D levels during the winter months.11 There are also special sunlamps to help the skin generate vitamin D, but because of the risk for skin damage from ultraviolet rays, many healthcare practitioners don’t recommend using them.

Make D your favorite letter for better health

Whether you’re lucky enough to get the vitamin D you need from the sun all year around, or taking a vitamin D supplement, you’re wise to ensure you get enough of this vital nutrient. If you’re wondering whether you need more vitamin D, ask your healthcare practitioner.

References:

  1. Kotz D. Time in the Sun: How Much Is Needed for Vitamin D? Available at: https://health.usnews.com/health-news/family-health/heart/articles/2008/06/23/time-in-the-sun-how-much-is-needed-for-vitamin-d. Accessed May 16, 2018.
  2. What is vitamin D? Vitamin D Council. Available at: https://www.vitamindcouncil.org/about-vitamin-d/what-is-vitamin-d. Accessed April 30, 2018.
  3. Ginde AA et al. Demographic differences and trends of vitamin D insufficiency in the US population, 1988-2004. Arch Intern Med.2009;169(6):626-632.
  4. Naeem Z. Vitamin D deficiency—an ignored epidemic. Int J Health Sci (Qassim). 2010;4(1):V–VI.
  5. Vitamin D (Calcitriol). Vivo Pathophysiology. Available at: http://www.vivo.colostate.edu/hbooks/pathphys/endocrine/otherendo/vitamind.html. Accessed May 2, 2018.
  6. Drezner M. Patient education: Vitamin D deficiency (Beyond the Basics). Wolters Kluwer. Available at: https://www.uptodate.com/contents/vitamin-d-deficiency-beyond-the-basics/print. Accessed May 16, 2018.
  7. How do I get the vitamin D my body needs? Available at: https://www.vitamindcouncil.org/about-vitamin-d/how-do-i-get-the-vitamin-d-my-body-needs. Accessed May 16, 2018.
  8. Holick MF et al. Evaluation, treatment, and prevention of vitamin D deficiency: an Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2011;96(7):1911-1930.
  9. Lehmann U et al.Bioavailability of vitamin D(2) and D(3) in healthy volunteers, a randomized placebo-­controlled trial. J Clin Endocrinol Metab. 2013;98(11):4339-4345.
  10. Tripkovic L et al. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic reveiw and meta-analysis. Am J Clin Nutr. 2012;95(6):1357-1364.
  11. Logan VF et al.Long­-term vitamin D3 supplementation is more effective than vitamin D2 in maintaining serum 25-hydroxyvitamin D status over the winter months. Br J Nutr. 2013;109(6):1082­-1088.

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