It may seem like a lifetime ago that we first started hearing whispers of a bat, a wet market and a rapidly spreading virus. During this time, one issue has remained top of mind for many in the chiropractic community – can chiropractic care boost immunity? In fact, methods for boosting immunity have come from all sorts of sources and varied extremely in their wisdom. So where do you start?
A recent paper published in the journal, Medicina, and authored by Haavik, Niazi, Holt and others has taken on the task of examining the potential mechanisms by which HVLA vertebral thrusts (which we will call adjustments for the rest of this blog article) might influence neuroimmune function . There are perhaps few people more qualified for the task, as Haavik and the New Zealand team have long been interested in uncovering the mechanisms underpinning the effectiveness of chiropractic care.
The team searched a collection of databases for articles published up until April 2021, which included keywords like ‘immune, endocrine, WBC, CD4, lymphocyte, chiropractic, spinal manipulation, osteopath, manual therapy, HVLA thrust, and spinal adjustment.’ This included systematic reviews, meta-analyses and peer reviewed (English language) journals.
They unearthed 23 papers that “explored the impact of HVLA controlled vertebral thrusts on neuroimmune markers of which 18 showed a significant effect. “These basic science studies…show that HVLA controlled vertebral thrusts can influence the levels of immune mediators in the body, including neuropeptides, inflammatory markers and endocrine markers.
So let’s break it down a little more:
Being that “basic science” for a neuroscientist is a little more comprehensive than basic science for the rest of us, lets examine what some of these mediators are. They include:
- Neuropeptides, which are compounds (short chain poly-peptides) that act as neurotransmitters. Essentially, they are signalling molecules in the brain. Significant neuropeptides in the review included neurotensin, oxytocin and substance P. It is interesting to note that “neurotensine, a neuropeptide that is abundant in the [Central Nervous System] and the [Gastrointestinal] tract is an important modulator of neuroendocrine function .”
- Inflammatory markers are usually detected via blood test and basically reveal increased inflammation in the body. Notable inflammatory markers noted in the study included Tumour necrosis factor, but others include C Reactive Protein, Erythrocyte sedimentation rate and plasma viscosity among others. Usually, inflammatory markers don’t offer much specificity in terms of what the inflammation is or where it is coming from. It simply tells us the body is fighting something.
- Endocrine markers, including notable hormones like cortisol and epinephrine, help us understand how the endocrine system is working as a whole. While “the endocrine system” is a wide spanning term as it includes all the hormones produced in the body, it does give us a profound insight into the stress load of the body.
There is an immense amount of information that has gone into this narrative review (see reference below for the full, comprehensive paper), but here are the key takeaways:
- There is moderate quality evidence that HVLA adjustments increase neurotensin and oxytocin. The changes were immediate and short term, but indicative of an immune effect nonetheless.
- Systemic review and meta-analysis data also showed moderate evidence for HVLA adjustments influencing neuropeptides and inflammatory biomarkers (that are important biochemicals associated with the function of the immune system).
- A randomised controlled trial showed higher neurotensin, oxytocin and orexin A levels in the group that received HVLA adjustments. Neurotensin specifically has been “shown to have an anti-inflammatory role that involves downregulating the activation of the pro-inflammatory cytokines, such as IL-6, tumour necrosis factor and IL-10.” Oxytocin, long known as the love hormone, also has an essential role in regulating hormone secretion from the pituitary gland in the brain. “Oxytocin secreting cells can integrate neural, endocrine, metabolic and immune information and play a pivotal role in the development and functions of the immune system .”
- There is low quality (but present) evidence for HVLA’s effect on Substance P in healthy individuals.
- A review of randomised and non-randomised controlled trials looking at the influence of HVLA on cortisol showed up mixed results, but this is perhaps to be expected given the varied factors that may influence cortisol production (i.e. whether the person under care is symptomatic or healthy, whether they have acute or chronic stress, and so on).
- Interleukins also present a complex narrative, as they can be either pro-inflammatory right up to strongly anti-inflammatory in their nature. However, studies have shown Spinal manipulative therapy to influence some interleukins.
While all 18 studies were referenced and discussed in the paper, it is noteworthy that basic science now accepts that the autonomic nervous system and the HPA axis “influence the immune response and stress response” but as the authors note, “these systems are impossible to separate as they are highly coordinated and physically interconnected.” More research is required to ascertain whether the HPA axis is influenced by SMT. What we do know is this: “As HVLA controlled vertebral thrusts have been shown to impact the CNS [Central nervous system] and the CNS is known to strongly influence immune function, this provides a plausible biological mechanism to explain how HVLA controlled vertebral thrusts could impact immunity.
While it would be impossible to adequately summarise the 301-reference narrative paper by some of the brightest minds in chiropractic neuroscience, it does give us a solid basis upon which to say – yes, it is possible that chiropractic care can boost immunity. Here’s how. (See the reference below for more information)
Haavik,H.;Niazi,I.K.; Kumari, N.; Amjad, I.; Duehr, J.; Holt, K. The Potential Mechanisms of High-Velocity, Low-Amplitude, Controlled Vertebral Thrusts on Neuroimmune Function: A Narrative Review. Medicina 2021, 57,536. https://doi.org10.3390/ medicina57060536