7 Reasons You May Be Vitamin D Deficient
Vitamin D, known as the “sunshine vitamin,” is freely available to all through exposure to sun’s rays. Yet recent studies suggest that a lack of vitamin D is surprisingly common worldwide.(1,2,3) By some estimates, over 40% of the U.S. population may be low in vitamin D,(4) with serious potential health consequences.
How could this have happened? Well, two things have happened over the past few decades. First, certain cultural changes have reduced our exposure to vitamin D, including more time spent indoors, more use of sunscreen, and less consumption of milk and fish. At the same time, new research is evolving our understanding of just how important vitamin D is, and how much we need to stay healthy. Yet the official recommendations for daily vitamin D intake have not been revised in decades.
Vitamin D is best known for its important role in bone health, and the official recommendations for vitamin D intake (600-800IU) were originally based on the amount needed to avoid bone deformities.(5) But many health experts feel that this is too low a bar. Vitamin D does much more than support healthy bones: it’s also important for healthy immune function, nerve function, muscle function, and a balanced mood. Low vitamin D levels have been linked with serious heart health risks, autoimmune problems, and neurological problems, as well as bone problems.(2,3)
The old recommendations were also based on the assumption that we’d be getting most of our vitamin D from the sun. But the numbers clearly show that what most people are getting naturally is not sufficient. There are many factors that can interfere with our exposure to vitamin D or our ability to properly metabolize it (we’ll get to those in a minute). Most experts think that vitamin D recommendations should be adjusted upwards, though they are still debating just how much.
While there is still no consensus on exactly how much vitamin D we should take daily to maintain healthy blood levels, recent studies put the number between 1000-4000IU, or up to 5000IU if you have a deficiency.(6) The current data suggests that most Americans have suboptimal levels, many are deficient, and almost no one has levels that are too high.(5)
Think you might be low in vitamin D? There’s a good chance you’re right, especially if any of the following factors apply to you. Here are 7 common reasons you may be low in vitamin D:
1. You Spend Most of the Day Indoors
This is the most common reason for the spread of vitamin D deficiency. Over the last half century, our culture has increasingly moved indoors. More of the population is working, and we’re working longer hours. When we do get home, we have our social media feeds, our Netflix queues, and other digital distractions. We’re more likely to do our shopping, socializing, and recreation online than outdoors. All of this is limiting our daily exposure to sunlight, which we need to make vitamin D.
2. You Wear UV Protection
Over the last few decades, awareness about skin cancer risk has increased significantly. Where getting a good tan was once a common beauty benchmark, now high SPF sunscreens are included in most skin products, and even window glass is designed to filter harmful UV rays. All this is good for skin cancer prevention, but it comes with a downside: blocking UV rays also reduces the absorption of vitamin D, by up to 90%.(7) Since UV protection is still necessary, this is another good reason to take vitamin D supplements.
3. You Live in the North
In much of the northern U.S. and Canada, sunlight is significantly reduced during the winter months. The angle of the sun’s rays in winter aren’t strong enough to support sufficient vitamin D production in northern latitudes above 40 degrees.(7,8,9) And in some of these places, winter can go on for up to 6 months. It’s harder for everyone to get enough vitamin D from sunlight in the winter,(10) but it’s particularly hard in higher latitudes.
4. You Have Dark Skin
Darker skin is less sensitive to UV light -- the melanin pigment that makes skin darker acts like a natural sunscreen. This means that dark skin requires more sun exposure in order to produce vitamin D.(11) Because of this, vitamin D deficiency is especially common in non-white populations. One study found that over 62% of Hispanics and 82% of blacks in the U.S. were seriously low in vitamin D.(4)
5. You’re in Your Senior Years
As you age, changes in your skin make vitamin D absorption less efficient. Reduced kidney function can also make it harder to convert vitamin D into its active form. Seniors also tend to spend less time outdoors, especially if they are less physically able, or confined to nursing homes. For all these reasons, older adults are at higher risk for vitamin D deficiency. Lack of vitamin D leads to bone and muscle weakness that limits mobility and increases risk of injury.(12)
6. You Have a Spare Tire
Studies show that people who carry extra weight around the waist are at higher risk of vitamin D deficiency,(13) although researchers are still investigating why. We know that vitamin D gets stored in body fat, so it may be that when there is more fat tissue to store up the vitamin, less vitamin D is free to circulate in the blood. Recent research suggests that body fat may also interfere with vitamin D metabolism. In one study, after a group of overweight women shed 10% of their body fat, their vitamin D levels went up 27%.(14)
7. You’re Vegan, Vegetarian, or Dairy-Sensitive
The list of foods that contain vitamin D is short and almost entirely animal-based. Vitamin D can be found naturally in fish, egg yolks, and beef liver. It’s often added to cow’s milk and traditional dairy products, sometimes to orange juice. But if you don’t eat fish, eggs, or dairy, you’re unlikely to get much vitamin D from your food. This means you’re getting even less vitamin D than the average person. Until recently, most vitamin D3 supplements were also animal-based. Luckily, today you can get Vegan Vitamin D supplements in the active D3 form.
Considering how common it is to have low vitamin D levels, for all the reasons above, it’s clear that most of us need to be taking vitamin D supplements at least some of the time to stay healthy. Naturelo Vegan Vitamin D3 is available in a 2500IU dose for daily maintenance, as well as a 5000IU dose to help bring levels up for those who are deficient.
1. Mona S. Calvo, Susan J. Whiting, Curtis N. Barton. “Vitamin D Intake: A Global Perspective of Current Status.” The Journal of Nutrition, Volume 135, Issue 2, February 2005, Pages 310–316, https://doi.org/10.1093/jn/135.2.310
2. Holick MF, Chen TC. “Vitamin D deficiency: a worldwide problem with health consequences.” Am J Clin Nutr. 2008;87(4):1080S-6S. doi:10.1093/ajcn/87.4.1080S
3. Naeem, Zahid. “Vitamin d deficiency- an ignored epidemic.” International journal of health sciences vol. 4,1 (2010): V-VI.
4. Forrest KY, Stuhldreher WL. “Prevalence and correlates of vitamin D deficiency in US adults.” Nutr Res. 2011;31(1):48-54. doi:10.1016/j.nutres.2010.12.001
5. “Vitamin D Fact Sheet for Consumers.” National Institutes of Health, Office of Dietary Supplements.
6. Bjarnadottir, A. “How Much Vitamin D Should You Take for Optimal Health?” Healthline, Jun 2017.
7. Holick MF. Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease, and osteoporosis. Am J Clin Nutr. 2004; 79:362-71
8. Calvo MS, Whiting SJ. “Prevalence of vitamin D insufficiency in Canada and the United States: importance to health status and efficacy of current food fortification and dietary supplement use.” Nutr Rev. 2003;61(3):107-113. doi:10.1301/nr.2003.marr.107-113
9. Kevin D Cashman, Ellen GHM van den Heuvel, Ruud JW Schoemaker, Damien P Prévéraud, Helen M Macdonald, Jayashree Arcot. “25-Hydroxyvitamin D as a Biomarker of Vitamin D Status and Its Modeling to Inform Strategies for Prevention of Vitamin D Deficiency within the Population.” Advances in Nutrition, Volume 8, Issue 6, November 2017, Pages 947–957, https://doi.org/10.3945/an.117.015578
10. Kroll, Martin H et al. “Temporal relationship between vitamin D status and parathyroid hormone in the United States.” PloS one vol. 10,3 e0118108. 4 Mar. 2015, doi:10.1371/journal.pone.0118108
11. Holick MF. Vitamin D deficiency. N Engl J Med. 2007; 357:266-81.
12. Boucher, Barbara J. “The problems of vitamin d insufficiency in older people.” Aging and disease vol. 3,4 (2012): 313-29.
13. European Society of Endocrinology. "Larger waistlines are linked to higher risk of vitamin D deficiency: Higher levels of belly fat are associated with lower vitamin D levels in obese individuals, according to data presented in Barcelona at the European Society of Endocrinology annual meeting, ECE 2018." ScienceDaily. ScienceDaily, 21 May 2018.
14. Kuzma, Cindy. “The Real Reason Why You’re Vitamin D Deficient.” Prevention, May 2013.