Bones, Joints and Pain

Why Bones and Joints Are Affected by the Gut

Bone and joint problems look mechanical. Bones thin, cartilage wears, discs degenerate. What that description leaves out is that all three processes are run by immune cells, and immune cells are trained and regulated substantially in the gut. The cells that dissolve old bone come from the same lineage as the immune cells that drive inflammation. The pain in a worn joint tracks better with inflammation inside it than with how worn it looks on a scan. That is where the gut comes in.

Bone, joints and pain, three different routes

For bone, the route runs through inflammatory signalling. Osteoclasts, the cells that dissolve bone, develop from the same lineage as macrophages and respond to the same signals. In a randomised trial, women aged 75 to 80 with low bone density took either Lactobacillus reuteri 6475 or placebo for twelve months. Both groups lost bone, as expected at that age, but the probiotic group lost roughly half as much. Separately, in adolescents, 8 grams a day of a fermentable fibre raised calcium absorption and left them with measurably more bone a year later.

For inflammatory joint disease, the route runs through immune recognition. Sequencing 114 stool samples found Prevotella copri strongly overrepresented in people with newly diagnosed, untreated rheumatoid arthritis, often dominating the community. About half of patients mount a specific immune response against it.

For wear-related joint pain, the route runs through inflammation reaching the joint. Sequencing stool from 1,427 people found more Streptococcus associated with more knee pain, replicated in a second group of 867 and independent of body weight, with evidence the link ran through inflammation measured inside the knee itself.

Source: Lactobacillus reuteri reduces bone loss in older women with low bone mineral density: a randomized, placebo-controlled, double-blind, clinical trial

Source: Expansion of intestinal Prevotella copri correlates with enhanced susceptibility to arthritis

Source: Intestinal microbiome composition and its relation to joint pain and inflammation

What this means for you

Joint pain that limits walking, or a bone broken from a minor fall after 50, needs proper assessment. Exercise therapy, weight management and prescribed osteoporosis treatment carry the strongest evidence here. In addition, the research above found a probiotic strain halving bone loss over a year, a single bacterium dominating the guts of newly diagnosed rheumatoid arthritis patients, and gut bacteria tracking with knee pain across two separate populations independently of weight. A varied, plant-rich diet supports the same gut bacteria this research ties to calmer inflammatory signalling and better calcium absorption. That's the same idea behind GutLab, everyday gut health starts with regularly feeding the microbiome a broad range of plant-rich ingredients.

Explore bone, joint and pain topics on this page

The panels on this page cover three different kinds of problem, and the gut evidence differs for each.

Osteoporosis and low bone density concern how bone is built and dissolved, and both have randomised trial evidence, at opposite ends of life. Arthritis and osteoarthritis concern joints, one through immune recognition of a specific bacterium and the other through inflammation reaching the joint from elsewhere.

Chronic pain and back pain concern how pain signals are amplified rather than how tissue is damaged, which is why scans so often fail to match how much someone hurts.

Use the panels on this page to find the one relevant to you.