Why does my gut affect my joints?

The anatomy, simply

Roughly seventy percent of immune tissue sits along the gut. Gut bacteria ferment fibre into short chain fatty acids such as butyrate, which feed the gut lining and calm immune activity throughout the body.

Why it happens

It sounds like a stretch until you look at where your immune system actually lives.

What to try today

Aim for thirty different plant foods across a week and add one fermented food a day. Increase fibre slowly so your gut can keep up.

Your immune system lives next to your dinner

Most people picture the immune system in the blood. In fact the majority of it is lined up along the gut wall, because that is where the outside world comes closest to the inside of you.

So the state of your gut is not a separate department. It is where a large part of your inflammatory tone gets set.

What fibre actually does

You cannot digest fibre. Your bacteria can. They ferment it and produce short chain fatty acids, butyrate in particular.

Butyrate feeds the cells of your gut lining and has calming effects on immune signalling that reach well beyond the gut.

Feed the bacteria poorly and they produce less of it. The lining gets less well fed and more permeable, and inflammatory messengers get through more easily.

That is the link to your joints, in one paragraph.

Variety beats quantity

The single most useful finding from the big microbiome work is that diversity of plants matters more than sheer volume of fibre.

Thirty different plant foods a week is the number that gets quoted, and it is less daunting than it sounds. Herbs count. Spices count. Nuts, seeds, beans, and whole grains count.

One extra kind of bean is worth more than another bowl of the same cereal.

Fermented foods

A Stanford trial found fermented foods lowered inflammatory markers and increased microbiome diversity more than a high fibre diet did over ten weeks. That surprised a lot of people, including me.

Yoghurt with live cultures, kefir, sauerkraut, kimchi, miso. Small amounts daily beat a big amount occasionally.

And this is another place where tradition got there first by a couple of thousand years.

Go slowly

If your fibre is currently low, tripling it overnight will make you bloated and miserable and you will quit.

Add one new plant food every few days. Drink water alongside it. Your bacteria need a few weeks to adjust their population.

And if you have IBS or inflammatory bowel disease, this needs tailoring with a dietitian. Some high fibre foods make those conditions worse, and that is not a personal failing.