Could diet help prevent and even treat osteoarthritis?

By Dr Catriona Walsh

Image by Katherine Chase

We had always assumed that osteoarthritis is a “wear and tear” problem that happens as we get older, unlike autoimmune arthritises like rheumatoid and psoriatic, which are caused by the body attacking itself. However, recently some studies have linked inflammation and diet with osteoarthritis. This latest study suggests that the gut microbiome might play a role in its development. This is just a mechanistic study done on mice, so we need to exercise caution when interpreting it. Human studies will be necessary to confirm these findings. 

However, this study suggests that feeding obese mice a prebiotic supplement, called oligofructose, altered their gut microbiome in such a way that the amounts of beneficial Bifidobacteria in the gut were increased. The obese mice fed the prebiotics didn’t lose weight either, so their joints were under the same wear and tear type of strain as the obese mice not fed the prebiotics. Despite this the prebiotic group had less inflammation and cartilage destruction in their joints. The authors suggested that the presence of inflammatory gut microbes in obese mice was able to set up an inflammatory cascade, where systemic inflammation resulted in white cells, called macrophages, migrating to the joints and causing the osteoarthritis. The authors also hypothesise that it is not so much carrying excess weight, resulting in overloading of the joints, that causes osteoarthritis; rather both osteoarthritis and obesity are complications of inflammation mediated, at least in part, through an inflammatory microbiome, combined with the absence of sufficient protective microbes. The oligofructose supplement also partially reversed insulin resistance in the mice. The control group of obese mice were instead fed a type of insoluble fibre, called cellulose, which is ubiquitous in whole grains and other plant foods. The mice fed the cellulose did not see any improvements in their microbiomes, their inflammatory markers, or their arthritis.

You may be wondering where you can source oligofructose. It is a type of fibre found in inulin. Inulin refers to a group of fibres found in a wide variety of vegetables, including chicory root, psyllium, Jerusalem artichokes, leeks, onions, green bananas and plantain, dandelion root, asparagus, and sweet potatoes, as well as coconut flesh, pulses and whole grains. It can also be found in supplement form.

Other research suggests that some prebiotic fibres (not all of them) can directly stimulate the cells in the body to make more connective tissue, and that this can support healing. Some of these prebiotics, like pectin, glucomannan, psyllium and aloe vera, are being investigated and exploited due to their ability to directly improve wound healing by boosting connective tissue production and reducing inflammation when used in topical preparations. On the other hand, one of the prebiotic fibres found in whole wheat, wheat bran polysaccharide, has been found to INCREASE inflammation and stimulate white blood cells. This is being investigated as a potential immunomodulator which could be used to stimulate an underactive immune system, but it’s effects in inflammatory conditions may be counter to what you would like to achieve. 

There are lots of different plant foods which contain prebiotics, like nuts, seeds, legumes, whole grains, vegetables and fruits, and other epidemiological studies suggest that eating a wide variety of different foods encourages a more diverse microbiome, because different microbes prefer different sorts of fibre. There are even prebiotics to be found in some animal foods which are rich in connective tissue, particularly joints and skin. So gelatinous bone broths made from lots of small joints and skin can also support gut microbes, because they are a good source of prebiotic mucopolysaccharides. 

In fact a hunter gatherer group living in Africa, called the Hadza, have some of the most diverse (if not the most diverse) gut microbiomes ever investigated. They eat a much wider variety of plants and animals than people who rely on farming. Almost none of their fibre is derived from whole grains, although they do trade with neighbouring farmers for some maize. The Hadza (despite having no reliable clean water, healthcare, sanitation, obstetric care, and only minimal access to modern medicine and drugs) are a very vigorous and healthy group of people with little in the way of chronic disease and no obesity. They have many elders who survive into old age. 

On the other hand, randomised controlled trials, like the Women’s Health Initiative, failed to show any improvement in a number of health outcomes ranging from cancer to heart disease, when women were advised to focus on increasing their intake of fibre from whole grains and vegetables while on a low fat diet. There are also increasing numbers of large epidemiological studies from all over the world which link carbohydrates, particularly cereal grains, and especially wheat, to adverse health outcomes, including heart disease, like this enormous recent study of 158 countries.

So the story behind fibre and health is likely a very complex one which needs a lot more research. But one thing is for sure: research on the gut microbiome, health and well-being are only getting started, and it will be exciting to see what that research reveals.


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