Written by Jessica Patella, ND. In this 13 week study of 256 racially diverse adults, adequate vitamin D levels were significantly associated with lower levels of arthritic knee pain regardless of obesity status. Also vitamin D levels were significantly decreased in obese individuals compared to those who were not obese.

Osteoarthritis is the most common form of arthritis and is characterized by pain, stiffness and limitations in physical functioning (1, 2). It is estimated that millions suffer from osteoarthritis worldwide and more than 50% of adults over 65 years of age have been diagnosed with osteoarthritis (1-3). This is a concern for older adults because osteoarthritis increases the risk for fall-related injuries, which are the leading cause of disability in this age group (1, 4). Obesity also plays a role in osteoarthritis and 69% of adults over 60 years of age are overweight or obese (1, 5). Recent research has found that low levels of vitamin D are more common in obese adults and lower levels of vitamin D are associated with chronic pain due to arthritis (1).

The research included 256 racially diverse men (n=95) and women (n=161) with symptomatic knee osteoarthritis from 45 to 85 years of age (average age 56.8, Black/African American 55%, non-hispanic whites 45%). Blood levels of vitamin D in all participants ranged from 2.90 to 48.01 ng/mL (avg: 23.11 +/- 9.12 ng/mL).

The clinical practice guidelines for vitamin D levels are:

Adequate30-60 ng/mL
Insufficient21-29 ng/mL
Deficient<20 ng/mL
Severe deficiency<10 ng/mL

The participants were studied comparing the obese and non-obese, determined by body mass index (BMI) numbers, with a BMI of 30 or greater indicating obesity. When comparing vitamin D blood levels in the obese and non-obese participants, obesity was significantly associated with vitamin D deficiency, as shown in the table below (p<0.001)(1). This indicates that obesity can possibly lead to vitamin D deficiency. Researchers postulated that the vitamin D may be getting “trapped” in the fat stores in obese participants, resulting in lower blood levels (1).

Vitamin D levelsObese (BMI > 30) (n=126)Non-obese (BMI<30) (n=130)
Adequate10%36%
Insufficient36%42%
Deficient54%22%

Participants with adequate blood levels of vitamin D also reported significantly lower levels of knee arthritis pain than participants with deficient levels (p<0.001) and insufficient levels (p=0.016), regardless of obesity status.  This was measured via the WOMAC* scale, which includes 24 scoring items and can be divided into sub-scales of pain, stiffness and physical function. The subscales were not given, but these results indicate that vitamin D levels are related to decreased arthritis pain in the body (1).

In conclusion, obesity was associated with vitamin D deficiency and insufficiency, while adequate vitamin D levels were associated with lower levels of arthritis pain. This indicates that obesity and low vitamin D levels are associated with inflammation in the body which can result in pain (1). Because of the strong association found between vitamin D levels and arthritis pain, the researchers recommended that vitamin D supplementation in patients with osteoarthritis may help reduce their pain (1). Although further research is needed to understand exactly how vitamin D plays a role in the reduction of pain (1).

*Western Ontario and McMaster Universities Index of Osteoarthritis (WOMAC)- a frequently used test in clinical and research settings to asses individuals’ osteoarthritis knee symptoms over the previous 48 hours.

Source:  Glover, Toni L., et al. “A cross-sectional examination of vitamin D, obesity, and measures of pain and function in middle-aged and older adults with knee osteoarthritis.” The Clinical journal of pain 31.12 (2015): 1060-1067.

© 2014 Wolters Kluwer Health, Inc. 

Posted May 4, 2015.

Jessica Patella, ND, is a naturopathic physician specializing in nutrition and homeopathic medicine and offers a holistic approach to health.  She earned her ND from Southwest College of Naturopathic Medicine in Tempe, AZ, and is a member of the North Carolina Association of Naturopathic Physicians.  Visit her website at  www.awarenesswellness.com.

References:

  1. Glover TL, et al.  A Cross-Sectional Examination of Vitamin D, Obesity and Measures of Pain and Function in Middle-Aged and Older Adults with Knee Osteoarthritis. 2015 Clin J of Pain. DOI:10.1097/AJP.0000000000000210
  2. Osteoarthritis.  Mayo Clinic.
  3. Helmick CG, et al.   Estimates of the prevalence of arthritis and other rheumatic conditions in the United States.  Part I.  Arthritis. Rheum. Jan 2008;58(1):15-25.
  4. Barbour KE, et al.  Falls and fall injuries among adults with arthritis—United States, 2012. MMWR Morb.  Mortal. Wkly. Rep. May 2 2014;63(17):379-383.
  5. Houston DK, et al.  Weighty concerns: The growing prevalence of obesity among older adults. J. Am. Diet. Assoc. Nov 2009;109(11):1886-1895.