Ginkgo, fish oil, brain-training apps: the list of products promising to keep your memory sharp is long, and the evidence behind most of them is thin. A team at King’s College London decided to test something far less glamorous. Not a pill with a fancy name, but a cheap plant fiber powder you can buy over the counter. After 12 weeks, the people who took it did better on a memory test used to detect the early signs of Alzheimer’s disease.
A study on twins over 60
The trial, published in Nature Communications in February 2024, followed 72 people over 60 from the TwinsUK registry, run by King’s College London, in other words 36 pairs of twins. In each pair, one twin took a daily fiber supplement and the other a placebo, for 12 weeks. Neither the participants nor the researchers knew who was taking what.
The supplement combined two prebiotic fibers, inulin and fructo-oligosaccharides (FOS). Both are inexpensive and widely available. All participants also did resistance exercises and took a protein supplement, since the study was originally designed to look at muscle strength. Testing was done remotely, using video calls, online questionnaires and cognitive tests.
What changed in 12 weeks
On muscle strength, the original question, the fiber made no significant difference. The surprise came from the brain tests. According to King’s College London, the fiber group performed better on the Paired Associates Learning test, a memory test considered an early marker of Alzheimer’s disease, as well as on tests of reaction time and processing speed.
Their gut microbiome changed too, with an increase in beneficial bacteria such as Bifidobacterium. Dr. Mary Ni Lochlainn, the study’s first author, said the findings “hold huge promise for enhancing brain health and memory in our ageing population.” Professor Claire Steves, the senior author, highlighted that the fibers are cheap, available over the counter, safe and acceptable, and said the next step is to see whether the effects last longer and hold in larger groups.
Why the gut may matter for the brain
The study adds to a growing field of research on the gut-brain axis, the idea that the bacteria in our digestive system communicate with the brain. Prebiotic fibers like inulin feed some of those beneficial bacteria. The researchers are careful, though: this was a small trial over a short period, and it does not show that fiber prevents dementia.
Before you buy a supplement
A few precautions are worth keeping in mind:
- Inulin and FOS can cause gas and bloating, especially at first, so starting with a small dose is usually recommended.
- Anyone with a digestive condition, or taking medication, should talk to their doctor before adding a supplement.
- The same fibers are naturally found in foods such as chicory root, onions, garlic, leeks, asparagus and bananas.
Brain health also depends on habits that have nothing to do with a powder: regular movement, like the daily walking distance cardiologists recommend after 50, and staying mentally active long before retirement, as a 26-year study suggests.
A small study with a big question
Seventy-two people and 12 weeks will not settle the debate on supplements and memory. But a cheap fiber outperforming a placebo on a test linked to early Alzheimer’s is exactly the kind of result researchers want to test on a larger scale. Until then, the safest bet may be the oldest advice of all: eat more plants.
