How inflammation contributes to bone loss
- Mar 19
- 5 min read
Updated: 3 days ago
Inflammation & Bone Health — Part 2 of 3
How inflammatory signalling can disrupt bone remodelling and contribute to bone loss
In Brief
Inflammatory cytokines may contribute to bone loss by increasing RANKL signalling. RANKL activates osteoclasts, the cells that break down bone.
Persistent inflammation can also reduce the activity of osteoblasts, the cells that build new bone. This can shift bone remodelling towards greater breakdown, where bone removal begins to outpace rebuilding.
This article explains
In Part 1, we explored how persistent inflammatory signalling can disrupt the balance of bone remodelling. Now let’s look more closely at the cellular mechanisms that explain how inflammation contributes to bone loss and the development of osteoporosis.
Inflammatory signalling molecules, known as cytokines, directly influence the balance between bone breakdown and bone formation.
The molecular messengers: How inflammatory cytokines affect bone health
Inflammation involves the release of signalling molecules known as pro-inflammatory cytokines, which play a key role in bone loss and osteoporosis.
Key inflammatory cytokines include:
Tumour Necrosis Factor-alpha (TNF-α)
Interleukin-1 (IL-1)
Interleukin-6 (IL-6)
These molecules are not simply inflammatory irritants, but precise biochemical messengers that influence cell behaviour throughout the body, including within bone tissue.
Through these signals, the immune system can influence the balance between bone breakdown and bone formation.
Much of this effect is mediated by the RANKL–OPG pathway. A 2023 systematic review and meta-analysis of OPG and RANKL in osteoporosis found that the balance between the two, expressed as the OPG to RANKL ratio, is associated with osteoporosis.
The RANKL pathway: Activating bone breakdown
Bone breakdown is carried out by osteoclasts. The development and activation of these cells is controlled by a signalling molecule called RANKL (Receptor Activator of Nuclear Factor Kappa-B Ligand).
Inflammatory cytokines increase the production of RANKL. More RANKL promotes:
More osteoclast (demolition crew) formation and activation.
Greater bone breakdown.
In practical terms, inflammatory signalling encourages the demolition crew to remove more material from the bone structure. This pathway is one of the key biological mechanisms linking inflammation and osteoporosis.
OPG: The body’s protective "brake"
The body does have a natural counterbalance, a molecule called osteoprotegerin (OPG). OPG binds to RANKL and prevents it from activating osteoclasts, effectively putting the brake on bone breakdown.
However, inflammatory cytokines can reduce OPG production. When this happens, the braking system becomes less effective, and osteoclast (demolition crew) activity can dominate.
Inflammation slows down bone-building cells
Inflammatory cytokines, including TNF-α and IL-6, also impair osteoblasts (the builders), reducing their efficiency. A 2023 review of cytokine effects on bone remodelling describes how sustained high cytokine levels suppress osteoblast function and bone formation.
As a result, bone formation slows whilst bone breakdown accelerates, a combined effect that favours bone loss over time.
What this mechanism means for bone health
Cytokine levels and RANKL activity cannot be seen directly without laboratory testing, but their effects on bone remodelling are well established.
Importantly, the level of inflammation in the body is not fixed; it can be influenced by lifestyle and metabolic factors.
Diet quality, gut health, metabolic health, sleep, and stress all influence inflammation and play a role in maintaining healthy bone density.
Understanding these mechanisms clarifies an important principle: Supporting bone health also means creating an internal environment where bone cells can carry out normal repair and renewal.
Addressing inflammation can form part of a structured approach to bone health, alongside nutrition, immune regulation, movement, sleep and medical care where needed.
Understanding these molecular pathways explains how inflammation can accelerate bone breakdown. But another question follows: what causes inflammatory signalling to remain elevated in the first place.
In Part 3 of this series, we’ll explore how everyday factors — including gut health, stress physiology and metabolic balance — shape the inflammatory environment that influences bone strength.
Frequently asked questions
What are inflammatory cytokines, and how do they affect bone density?
Inflammatory cytokines are specialised signalling molecules, such as TNF-α and IL-6, that carry messages between the immune system and your bone tissue.
While these molecules are necessary for a normal immune response, chronic elevation can disrupt the balance of bone remodelling. These signals may prompt the body to increase the activity of bone-clearing cells while simultaneously slowing down the cells that build new bone, which may contribute to lower bone density.
How does the RANKL signalling pathway contribute to bone loss?
The RANKL pathway is a key biological mechanism that regulates the activation of osteoclasts, the cells responsible for breaking down bone.
When systemic inflammation is present, the body may produce an excess of the RANKL molecule. This increase can overactivate the osteoclasts (bone-clearing cells), causing them to remove bone mineral more rapidly than it can be replaced. This pathway is one of the key molecular links between chronic inflammation and skeletal fragility.
How does the body naturally protect itself from bone loss?
The body uses a protective molecule called Osteoprotegerin (OPG) to counterbalance RANKL and act as a natural "braking mechanism" on the bone-clearing process.
OPG works by intercepting the RANKL signals before they can activate the bone-clearing cells (osteoclasts). However, persistent inflammation can lower the production of OPG. When this "braking system" is weakened, the balance often shifts in favour of bone resorption, which may contribute to osteoporosis risk.
Can managing inflammation help support bone health?
Yes, addressing the internal inflammatory environment through lifestyle changes may help support the natural cycle of bone renewal.
While these molecular pathways are complex, they are influenced by external factors. Addressing drivers of inflammation, such as gut health imbalances, poor sleep, and chronic stress, may help support a healthier bone environment. This approach aims to create a more stable environment for your "builder" cells to function effectively.
Structured guidance for bone health
Understanding the processes through which inflammation contributes to bone loss is an important step. The challenge is translating these mechanisms into clear, practical decisions — particularly when multiple pathways may be involved.
The Nutrition for Bone Health Guide brings these principles together into a structured, evidence-led approach, helping you apply them in a way that fits your health, lifestyle, and medical context.
Read the full inflammation and bone health series
This article is part of a three-part series on inflammation and bone health:
Part 2 (current): How inflammation contributes to bone loss
Part 3: How gut health, stress and metabolism affect bone density
Together, these articles provide a structured overview of how inflammation influences bone health and osteoporosis risk.
Disclaimer
The information in this article is for general educational purposes. It is not intended to diagnose, treat, or replace medical advice. Bone health is influenced by many factors, and individual circumstances vary.
If you have been diagnosed with osteopenia or osteoporosis, or are taking medication that affects bone health, continue to work with your GP, consultant, or specialist team. Nutritional therapy is intended to support, not replace, medical care.
For personalised guidance, consult a registered nutritional therapist or other qualified health professional who can assess your full clinical picture.
References
Deng, Z. et al. (2023) 'The effect of cytokines on osteoblasts and osteoclasts in bone remodeling in osteoporosis: a review', Frontiers in Immunology. Available at: https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2023.1222129/full
Zhang, Y. et al. (2023) 'The association of osteoprotegerin and RANKL with osteoporosis: a systematic review with meta-analysis', Journal of Orthopaedic Surgery and Research. Available at: https://link.springer.com/article/10.1186/s13018-023-04179-5
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