The Gut–Bone Connection: How Your Digestive Health Shapes Your Bone Health

Written By Andrea Robinson

‍Osteoporosis is very much preventable. Prevention itself is not complicated, but it ideally starts early and is multifaceted. For years, bone health was thought to be largely determined by calcium intake, vitamin D, and weight-bearing exercise. Whilst all these are important, there is more we can and should do. Today I just want to focus on one of the other powerful players influencing bone strength: your gut.

Your gut and your bones may seem like completely separate systems, but they communicate with each other constantly. This relationship between the gut and the skeleton is known as the gut–bone axis, and it’s reshaping the way we understand osteoporosis prevention. Your digestive system doesn’t just break down food — it regulates inflammation, nutrient absorption, hormones, and even the activity of bone-building and bone-breaking cells.

The gut-bone axis works through several interconnected pathways and I will explore these here.

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1. The Gut Controls Nutrient Absorption for Bone Building

Strong bones rely on consistent intake and absorption of key nutrients like:

  • Calcium

  • Magnesium

  • Vitamin D

  • Vitamin K2

  • Protein

  • Trace minerals (zinc, boron, manganese)

All of these depend on healthy digestive function. Low stomach acid, dysbiosis (microbial imbalance), conditions like IBS, Crohn’s or coeliac disease, or intestinal inflammation can reduce absorption, leaving bones under-nourished — even if your diet appears excellent.

For example:

  • Low stomach acid (common with age and PPI medications, e.g. Nexium) can significantly reduce calcium absorption.

  • Inflammation in the small intestine can impair the uptake of magnesium and vitamin D.

  • Disrupted fat digestion affects absorption of fat-soluble vitamins such as D and K2.

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2. The Microbiome Actively Influences Bone Formation

Your gut bacteria do more than help with digestion — they actually talk to your bones. Healthy microbes produce short-chain fatty acids (SCFAs) like butyrate, which help:

  • Reduce systemic inflammation

  • Improve mineral absorption

  • Stimulate osteoblasts (bone-building cells)

  • Support hormonal signalling involved in bone turnover

Low SCFA production is linked to poorer bone density and higher osteoporosis risk in several studies.

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3. Inflammation From the Gut Can Accelerate Bone Loss

A compromised gut lining — often referred to as increased intestinal permeability (“leaky gut”) — allows inflammatory molecules to enter the bloodstream.

This chronic, low-grade inflammation triggers immune signalling that:

  • Increases osteoclast activity (cells that break down bone)

  • Reduces osteoblast activity (cells that build bone)

Over time, this inflammation-driven imbalance can accelerate bone loss and contribute to osteopaenia or osteoporosis.

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4. Gut Health Influences Key Hormones Involved in Bone Metabolism

The gut plays an important role in regulating hormones and signalling molecules that affect bone density, including:

• Estrogen

Gut microbes influence how estrogen is metabolised and recycled. A disrupted microbiome may reduce circulating estrogen levels — particularly relevant during perimenopause, when bone loss accelerates (you can read more about this here).

• IGF-1

Gut health and dietary protein absorption influence insulin-like growth factor 1 (IGF-1), a hormone essential for bone building.

• GLP-1

GLP-1 is a hormone released from specialised cells in the intestine called L-cells after we eat. GLP-1 receptors are present in bone tissue, suggesting the hormone may play a role in skeletal regulation. There is evidence that GLP-1 stimulate osteoblast activity, suppress osteoclast formation and support overall bone formation. You can support GLP-1 secretion by eating a diverse diet with plenty of fibre and protein.

The GLP-1 hormone is different from the GLP-1 receptor agonist medication. GLP-1 receptor agonists are long-acting medications designed to mimic and amplify the hormone’s effects. Over time, the medication can lead to inadequate nutrition and low muscle mass, which can have a negative impact on bone health. Ensuring adequate protein, key bone-supporting nutrients, and regular resistance training can help maintain bone strength while using GLP-1 medications. You can read more about this topic here.

• PTH

The gut influences parathyroid hormone (PTH) activity, which regulates calcium balance.

The gut does not produce PTH, but it strongly influences how much PTH the body needs to maintain calcium balance. One of the main triggers for PTH release is low blood calcium levels. When gut function is compromised — through poor nutrient absorption, microbiome imbalance, or inflammation — the body may compensate by increasing PTH. Over time, this can promote bone breakdown and increase osteoporosis risk.

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5. Medications That Affect the Gut Can Also Affect Bone Density

Common medications that influence gut function may indirectly weaken bones. These include:

  • Proton pump inhibitors (PPIs) → Reduce stomach acid; impair calcium and magnesium absorption.

  • Antibiotics → Disrupt microbiome diversity; reduce SCFA production.

  • Steroids → Increase inflammation; accelerate bone loss.

This doesn’t mean these medications are “bad,” but their impact on bone health is worth considering. If you are taking any of these medications, please don’t stop doing so. Talk to your doctor about your concerns and ask them to do a DEXA scan to see where your bone health is at (if you are in Australia and are below 70 years of age, you will have to pay for this, but your bone health is worth it!).

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How to Support the Gut–Bone Axis

Here are simple, evidence-based ways to nourish both your gut and your bones:

✔ Eat a diverse, fibre-rich diet

Plant fibres feed beneficial bacteria that produce SCFAs.

✔ Include fermented foods

These help increase microbiome diversity. Examples: yoghurt, kefir, sauerkraut, kimchi, miso.

✔ Ensure adequate protein

Supports collagen formation and osteoblast activity. See my post here on protein sources

✔ Optimise stomach acid and digestion

Bitters like rocket, kale, radicchio or cruciferous vegetables, mindful eating, and adequate zinc can help.

✔ Reduce alcohol, smoking, and high-sugar intake

All can harm the microbiome.

✔ Limit ultra processed foods

Limiting these helps reduce dysbiosis and inflammation.

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The Takeaway

Your bones are far more than passive structures — they’re dynamic, metabolically active tissue that respond to hormones, nutrients, inflammation, and gut-derived signals. By supporting your digestive health, you support your skeletal health too.

Improving the gut–bone axis is a powerful and often overlooked opportunity for preventing osteopaenia and osteoporosis, especially for women entering perimenopause and menopause.

‍ Gut testing

In my clinic, I ask all my patients to do a gut microbiome test. This gives us great insight into how well their gut is functioning, whether there is inflammation, intestinal permeability or any suspected gut infections. Having this kind of insight helps me to tailor treatment plans specific to my clients’ needs. Improving their gut health means improving their bone health! If you want to chat about this further, you can book an appointment here.

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References

Cronin, O., Lanham-New, S. A., Corfe, B. M., Gregson, C. L., Darling, A. L., Ahmadi, K. R., Gibson, P. S., Tobias, J. H., Ward, K. A., Traka, M. H., Rossi, M., Williams, C., Harvey, N. C., Cooper, C., Whelan, K., Uitterlinden, A. G., O'Toole, P. W., Ohlsson, C., Compston, J. E., & Ralston, S. H. (2022). Role of the Microbiome in Regulating Bone Metabolism and Susceptibility to Osteoporosis. Calcified tissue international, 110(3), 273–284. https://doi.org/10.1007/s00223-021-00924-2

Lyu, Z., Hu, Y., Guo, Y., & Liu, D. (2023). Modulation of bone remodeling by the gut microbiota: a new therapy for osteoporosis. Bone research, 11(1), 31. https://doi.org/10.1038/s41413-023-00264-x

Xu, X., Jia, X., Mo, L., Liu, C., Zheng, L., Yuan, Q., & Zhou, X. (2017). Intestinal microbiota: a potential target for the treatment of postmenopausal osteoporosis. Bone research, 5, 17046. https://doi.org/10.1038/boneres.2017.46

Zaiss, M. M., Jones, R. M., Schett, G., & Pacifici, R. (2019). The gut-bone axis: how bacterial metabolites bridge the distance. The Journal of clinical investigation, 129(8), 3018–3028. https://doi.org/10.1172/JCI128521

Zhao, C., Liang, J., Yang, Y., Yu, M., & Qu, X. (2017). The Impact of Glucagon-Like Peptide-1 on Bone Metabolism and Its Possible Mechanisms. Frontiers in endocrinology, 8, 98. https://doi.org/10.3389/fendo.2017.00098

Andrea Robinson
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How to Eat Well Consistently