Inexpensive daily supplement appears to improve brain function in older adults:

What's good for your aging gut may be good for your aging brain.

What's good for the aging gut is good for the aging brain.

A first-of-its-kind study of twins has found that taking a daily protein and prebiotic supplement improved memory in people over 60.

Published in 2024, the findings are food for thought, especially since the same memory and learning methods have been used to detect early signs of Alzheimer's disease.

A double-blind trial tested two low-fat dietary fiber supplements available over the counter in several countries.

Prebiotics are non-digestible foods that help stimulate our immune system.

One of the supplements is inulin, a fiber in the fructan class. Fructooligosaccharide (FOS) is a plant-derived fiber commonly used as a low-calorie natural sweetener.

Watch the video below for a summary of the research:

To see how these supplements affect the aging brain, researchers at King's College London recruited 36 pairs of twins, all of whom were at least 60 years old.

Each pair was randomized: one received daily antibiotics mixed with protein powder, while the other received a placebo powder.

Twins who did not receive insulin or FOS generally scored higher on cognitive tests three months later.

Furthermore, daily fiber supplementation was associated with modest changes in the gut microbiome between twins.

For example, the beneficial Bifidobacterium was more abundant in those taking inulin or FOS.

Studies on mice suggest that Bifidobacterium reduces cognitive deficits by regulating gut-brain connections.

"We are delighted to see these changes in just 12 weeks. This holds great promise for improving brain and memory health in our older people," said Mary Ni Lochlein, a geriatric medicine researcher at King's College London, when the findings were published.

"Unraveling the secrets of the gut-brain axis over time may offer new insights into a healthier life."

King's College is home to the UK's largest adult twin registry, and twin studies are invaluable when distinguishing between genetic and environmental influences on human health.

Previous research in rodents has shown that high-fibre supplements such as inulin and FOS can 'feed' the colon's microbiome, allowing 'good' bacteria to thrive.

Some of these bacterial players have also been linked to improved cognitive function in both mice and humans.

Evidence for a close connection between the gut and the brain has been mounting for years.Some experts are now so convinced of the results that they refer to the gut as the body's 'second brain'.

But how these two nervous systems work together remains a mystery.

The twin study at KCL suggests that eating certain "brain foods" may be a promising way to treat cognitive decline, adding to research that suggests key nutrients can slow its progression.

"These plant fibers are cheap and available over the counter and could benefit many people in this cash-strapped era. They are also safe and acceptable," geriatrician Claire Steves told KCL.

"Our next task is to see if these effects persist over time and in larger groups of people."

Although prebiotics appear to improve some aspects of cognitive function in the aging brain, such as memory and processing time, the study did not indicate significant physiological benefits.

Muscle loss was not improved among older twins who received a high-fiber diet, although inulin and FOS were important muscle-maintenance factors.

The genders participating in the current trial were mostly female, and although the researchers corrected for gender differences in their findings, they acknowledge that there may have been some selection bias in the KCL twin group.

However, women are more susceptible to Alzheimer's disease, and studies like this support the new idea that cognitive decline is not always a disease of the brain, but may also involve external factors.

The Lancet Dementia Committee recently estimated that 7% of the risk of Alzheimer's was linked to high levels of low-density lipoproteins in middle age. These low-density lipoproteins carry cholesterol and fatty acids throughout the body.

This risk factor may explain why women suffer from Alzheimer's disease at twice the rate of men, according to a 2025 study led by researchers at King's College London.

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And in 2025, researchers reported that in humans and mice, low ratios of Bifidobacterium and Akkermansia in the gut are linked to multiple sclerosis, and that this imbalance is linked to a more severe disease.

The gut has a finger in many 'pies' in the body, including the immune system and central nervous system.Feeding the microbiome a specific prebiotic and probiotic diet could open the door to the treatment of many diseases and ailments.

The study was published in Nature Communications.

An earlier version of this article was published in March 2024.