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Vitamin D and Immune Function

Many chronic pain disorders are being linked to autoimmunity or decreased immune function. Examples include, interstitial cystitis (IC), endometriosis, and celiac disease. At the same time, scientists are noticing a link between decreased immunity and low vitamin D levels. Whether low vitamin D is the cause or effect of autoimmune disorders is still to be determined, but we do know vitamin D acts as a moderator for the cycles of immunity and the inflammatory response. So when vitamin D levels are low, immune function is often suppressed and the inflammatory response runs unchecked. Many doctors are now seeing the importance of treating immune deficiencies with vitamin D. However there are a few things you need to know about vitamin D before you begin supplementation: Don’t just take vitamin D - get your levels checked first You can have too much of a good thing. It is important to be just as cautious with vitamin supplementation as you are with prescribed medications, because too much of a vitamin can cause severe health problems. Overdosing on vitamins is called vitamin toxicity or hypervitaminosis, and each vitamin has its own symptoms of toxicity. Hypervitaminosis D can cause excessive amounts of calcium to build up in your blood, which can lead to dehydration, kidney stones, and kidney or heart damage. If you have an autoimmune disorder you should definitely have your doctor or nutritionist check your vitamin D levels before beginning supplementation. Your doctor can then monitor your levels with regular check ups every 3-6 months. Living in the “Sunshine State” doesn’t guarantee you’re getting enough of the “Sunshine Vitamin” Recent studies have confirmed - just because you live in a state known for its sunshine does not mean you have adequate vitamin D levels. If you have an autoimmune disorder there’s a strong likelihood that getting sunshine exposure isn’t enough to raise your vitamin D levels adequately. I have lived in Southern California for 30 years and I still have extremely low vitamin D levels when I’m not taking supplementation. The only way to really know if you’re deficient is to get your levels checked by your doctor. Don’t take vitamin D on its own Vitamin D is better absorbed when taken with a meal, especially a fatty meal. (Remember, “fatty” doesn’t not have to equal “unhealthy.” There are good fats as well as bad.) So while you can take a vitamin D supplement on an empty stomach, it will absorb into your body much better when taken with food. Also, many forms of vitamin D are a vitamin D/Omega-3 fatty acid combo pill. This is because, again, vitamin D absorbs better when it has a fat it’s binding to, and Omega-3 and vitamin D help each other. A few other things about vitamins Vitamin D comes in two forms: vitamin D2 and vitamin D3. Vitamin D3 is thought to be the more active, and therefore more beneficial, form of of vitamin D, but talk to your doctor about which form you should take. When purchasing vitamins, look for ones that are stored in dark or opaque bottles. Light exposure tends to weaken the strength of the supplement, so vitamins stored in see-through bottles may be less effective. Heat may also reduce a supplement’s effectiveness, so some vitamins may need to be stored in the refrigerator. Make sure to read the label on your supplement or talk to your doctor about how best to store your vitamins.



Aranow, C. (2011). Vitamin D and the Immune System. Journal of Investigative Medicine, 59(6), 881-886. doi:10.231/JIM.0b013e31821b8755

National Library of Medicine National Institutes of Health. (2011). Hypervitaminosis D: MedlinePlus Medical Encyclopedia. Retrieved from

University of California, Davis. (2011, January 5). UC Davis study finds low vitamin-D levels in Northern Californians with metabolic syndrome. Retrieved July 7, 2014, from


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Holly Horikawa PT, DPT, CLT

Owner and Founder

Dr. Horikawa received her Doctorate in physical therapy from Duke University in 2005 and founded Lokahi Physical Therapy & Wellness in 2013.

R.A. Sovilla

Patient Advocate

R.A. Sovilla suffered with pelvic pain due to endometriosis for over a decade. She is currently living pain-free post surgery and co-leads the OC Chronic Pelvic Pain Support Group with Dr. Horikawa.

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