Vitamin D and pain: the emerging connection

Feeling pain is a natural response of the body to protect further damage to tissues and reduce injury and to allow healing to occur. Pain is an alarm system designed for self-preservation. However, when pain becomes chronic or abnormal, this complex and potentially life-saving function can be disabling, stressful, and incapacitating. Pain can turn into nature’s curse, affecting sleep, work, education, social life, and everyday tasks.^1,2

Due to the complexity and prevalence of chronic pain, researchers are investigating causes and non-pharmacological treatments, with a pronounced scientific interest over the last decade on the effects of vitamin D deficiency and the use of supplementation.¹This article explores the emerging relationship between vitamin D and chronic pain.

The burden of chronic pain

Chronic pain is the leading cause of disability and disease burden globally.1 Abnormal or chronic pain can be specific to a body part or area, be widespread, or vague, and can be due to tissue injury, an underlying health condition, or have an unknown (idiopathic) cause. Regardless of the aetiology, when pain lasts beyond three months it is classified as chronic.³

Most cases are estimated to be idiopathic, with around 20% of chronic pain sufferers finding little to no benefit from currently available analgesics.^1,3

Recent emerging research shows that improving vitamin D status has analgesic effects and can reduce chronic pain.¹

Vitamin D deficiency and chronic pain link

Vitamin D deficiency is a global public health imperative. Even in sunny Australia, approximately 20% of adults (over 25 years), 32% of young adults (18-24 years) and 17% of adolescents (12-17 years) are deficient in vitamin D.⁵Deficiency may also increase by more than 50% in women during winter and spring and for those living in southern Australian areas.⁶

Many researchers suggest that a deficiency in this neuroactive steroidal vitamin may be the reason for non-specific chronic pain.^3,7Although research is conflicting, there are strong correlations between vitamin D levels and musculoskeletal pain, such as lower back pain, with a significant association in diabetic peripheral neuropathy. Additionally, research shows an association between improved vitamin D status and reductions in chronic pain for participants with insufficient or deficient 25(OH)D serum (vitamin D) levels.¹

Potential mechanisms of action

Pain is a highly complex process involving multiple systems of the body. The potential mechanisms by which vitamin D exerts an analgesic effect are not fully understood. However, it is known that its role extends beyond bone metabolism functions, with vitamin D receptors (VDRs) found in numerous cell types across the body including those involved in pain signalling:

skin (pain signal transduction)
neurons (signal conduction)
spinal cord (transmission/modulation)
brain (pain perception).¹

Potential mechanisms of action

skin (pain signal transduction)
neurons (signal conduction)
spinal cord (transmission/modulation)
brain (pain perception).1

Through its interaction with VDRs, vitamin D appears to mediate gene expression for pain-genes and encode for proteins involved in pain signalling, including nerve growth factor (NGF), glial-derived neurotrophic factor (GDNF), epidermal growth factor receptor (EGFR) and opioid receptors.1 By modulating inflammatory cytokines and prostaglandins, vitamin D may also influence pain sensitivity and provide analgesic effects during inflammation and after injury.1,12

Additionally, vitamin D may play a significant role in visceral pain. Short-chain fatty acids (SCFAs) and neurotransmitters produced by the gut microbiota are involved in pain signalling and inflammatory processes. Vitamin D may indirectly affect visceral pain through its action on gut microbiota modulation.1

Vitamin D clinical prescribing for pain management

Clinical research shows vitamin D status has a potential role in patient case analysis for many debilitating conditions. However, research for chronic pain amelioration features varying dosages, making it difficult to ascertain a prescriptive protocol. One guide is that most studies involved a vitamin D3 treatment duration of 12 weeks. As there is no standardised vitamin D dose or duration, and research has shown decreases in pain correspond to increases in vitamin D levels, it is reasonable to suggest that serum 25(OH)D levels can be used as a guide for individual pain management.^1,6,8

Living with chronic pain every day can be devastating to a person’s quality of life.^1,2Although the exact mechanisms are not fully understood, research supports the appropriateness of vitamin D testing, with adequate supplementation if serum levels are below optimal or in deficiency ranges.¹This simple strategy may be a life-changing adjunct treatment protocol for those with chronic pain.

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References

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