Why bones leach minerals
Bones are mineralised tissue — primarily calcium hydroxyapatite (calcium + phosphate). Simmering bones in water for 12–24 hours, often with vinegar to accelerate extraction, pulls calcium, phosphate, magnesium and sodium into the liquid. A standard 250 ml cup can deliver 200–400 mg phosphate — a renal-significant dose. Inorganic phosphate from broth is highly bioavailable.
Sodium load
Most recipes (and commercial broths) add 1–2 tsp salt per litre. Commercial UK bone broths range 0.4–0.9 g salt per 250 ml = 160–360 mg sodium. Combined with the broth used in soups, stews and risottos through the day, this stacks rapidly.
Food first. If you are choosing a daily multivitamin alongside a balanced diet, Kidney Vitality was developed by a UK Consultant Nephrologist using renal nutrition principles. See the formulation.
Purines and gout
Bone marrow and animal connective tissue are purine-rich. Long simmering concentrates purines in the broth. Hyperuricaemia is common in CKD and is associated with faster progression. People with gout or elevated uric acid should avoid bone broth entirely.
The collagen claim
Marketing suggests bone broth 'heals the gut' or 'rebuilds joints' through dietary collagen. Collagen is broken down to individual amino acids in digestion — it does not arrive intact at joints or kidneys. The Cochrane and BDA position is that there is no evidence collagen supplements or broth protect kidney function. The mineral load is real; the wellness benefit is not.
Renal-friendly stock alternatives
- Marigold Swiss vegetable bouillon, reduced-salt version.
- Homemade veg stock: 1 onion, 2 carrots, 1 leek, 2 sticks celery, herbs, 1 hr simmer.
- A splash of dry white wine + lemon for depth.
- Avoid: shop-bought bone broth, bone broth concentrates, 'bone broth protein powders'.
