Could a lack of fibre be contributing to the rise in chronic disease?

The names of chronic diseases tell different stories.

Diabetes takes its name from an ancient Greek word meaning “to pass through”. Cancer means “crab,” a reference to the resemblance Hippocrates saw between a tumour and the animal. Heart disease, kidney disease and depression are named for the organs or symptoms involved; arthritis describes inflammation of the joints. Crohn’s disease and Alzheimer’s, by contrast, carry the names of the doctors who first documented them.

There is not a cause anywhere on that list. We organized medicine by organ, so we got a disease for every organ.

The missing input may be hiding in plain sight. Modern food has become extraordinarily good at delivering calories while stripping away much of the complex fibre that once fed the microbes in our gut. Those microbes turn that material into molecules that signal the body when to release glucose, when to stop eating and how hard to run the immune system.

However, we actually removed much of the input without realizing it was information.

For a century, nutrition treated fibre largely as what food contained after counting the useful parts. We now know it is more complicated than that. Fibre is not one thing but thousands of molecules, with different structures and different biological effects.

The question is no longer simply how much fibre we eat. It is which molecules are missing, what they normally tell the body to do and whether putting them back can change the diseases that appeared when they disappeared.

About 1 in 14 adults in the United States now meet the basic measures of metabolic health. In the heart, it shows up as cardiovascular disease, causing more than 19 million deaths a year.

In the gut, it is colorectal cancer, the leading cause of cancer death among people under 50 and part of a broader rise in early-onset cancers across 14 types. In the brain, it shows up in mood: more than a billion people now live with a mental health condition and migraine prevalence has risen 58% since 1990, to 1.16 billion people.

In the joints, osteoarthritis has more than doubled in prevalence. In the immune system, it is autoimmunity, whose most common marker – the prevalence of antinuclear antibodies – has climbed about 50% in a generation, fastest in teenagers, over a period in which the population’s genes did not change appreciably over that period.

Different organs, specialists and names but with a common physiological thread running through many of them. Deaths and diagnoses get recorded. Most of the cost is paid in energy, mood, joints, drugs, attention, childhoods and lost choices.

Nobody was wrong. The technology to see it didn't exist, so people interpreted the underlying process through whichever organ or symptom it affected. It looked like ageing, genetics or lifestyle and for decades the story was personal: eat less, move more, try harder. But willpower did not fail in every industrialized country in the same 50 years; the environment changed and food changed with it.

It is one word for thousands of different molecules. Until very recently, the structure of most of them was unknown and so was what each one does inside a person. Nutrition science filed the part of food it couldn't account for under a single label: "unavailable." Maybe it was unavailable, to us at least but it was also unread.

Those molecules feed a biological signalling layer. When they reach the large intestine, the bacteria there ferment them into short-chain fatty acids and other small molecules and the body uses those as instructions: how fast to release glucose, when to feel full, how hard the immune system should be running that day.

One natural trigger for GLP-1, the gut hormone that this decade's blockbuster drugs imitate, is these fermentation products. Those drugs, a $66 billion market in 2025 heading for $185 billion by 2033, pharmacologically engage a signalling pathway that food also activates. What we filed under regularity is a signalling system between food and the body.

Over the past century, industrial processing learned to keep the calories and drop the rest. The diversity, structure, and quantity of these molecules reaching the colon fell out of the food chain and the microbial lineages that depended on them thinned out, which can compound across generations.

People who still eat roughly the way humans did for most of our history take in 100 to 150 grams a day and are in excellent metabolic health. The average American manages about 17 grams and only around 5% of adults reach even the recommended floor.

Strip away that signalling layer and the body runs without instructions that it spent a few million years learning. Glucose handling drifts. It is hard to overeat when there is enough fibre in the diet, because fibre generates the feeling and signal of having had enough; take it out and people eat past full, because nothing told them to stop.

And the immune system, which reads the same metabolic signals, never gets the signal to stand down. Immunologists have a word for this, metaflammation: low-grade, systemic, chronic inflammation that comes from metabolic state rather than from any infection.

A 2019 review in Nature Medicine put chronic inflammatory diseases at the top of the list of what kills people worldwide. These processes are implicated across conditions including diabetes, cardiovascular disease, colorectal cancer, depression and autoimmune disease.

Scurvy had been common on ships for 300 years. Once doctors understood it as an absence, nobody built a scurvy management industry. The navy put lemons on ships and the disease went away. Common does not mean inevitable.

Scurvy had company. Beriberi, pellagra, rickets and goitre were all named for their symptoms, until the vitamins were told apart and each disease was renamed for what was missing, and the flour, the salt and the milk changed instead of how people lived.

We haven't done the same for fibre yet. Put enough of it in food and people won't eat the food. So when fibre is included, it's in small quantities, mostly inulin or a synthetic from wheat, corn or cassava and those are not the molecules that went missing.

For the last several years, One Bio has worked on the thousands that did: which structures do what in a body, and how to get them back into ordinary food without changing the taste.

In a two-week trial, 20 grams a day of a short-chain oat fibre reduced the time participants spent in unhealthy blood-sugar ranges by 67% and took the energy crashes out of the day, with an exploratory signal of improved mood and concentration in the people who began the study struggling.

The implication is striking: some of what was lost may not need to be invented, but restored.

The body isn't broken. We spent a century naming where the deficiency showed up and building blockbuster drugs to manage each one. The last time medicine learned to name disease by what was missing, it changed the food – and some of those diseases disappeared.