Everyone wants to know how to improve their gut health and their brain health. But, what if a daily pill could have a positive effect on both? New research shows that something as simple as a fiber supplement could be used to improve brain function in older adults.Related video above: Even light exercise boosts your brain, study saysA study published in Nature Communications looked at how fiber might play a role in brain health. Researchers recruited 36 pairs of twins—72 individuals in total—over the age of 60. Each twin received either a placebo or a 7.5-gram fiber supplement (which the study specifies as a prebiotic, which is a type of fiber that feeds the good bacteria, a.k.a probiotics, in your gut) every day for 12 weeks. In addition, all participants performed resistance exercises and ate a protein supplement daily throughout the study. After 12 weeks, researchers found that the prebiotic supplement had led to significant changes in the participants’ gut microbiomes. In particular, participants taking the supplement saw a significant increase in the number of beneficial bacteria, called Bifidobacteria, in their gut. Within just 12 weeks, researchers also found that those taking fiber supplements were performing better in tests assessing brain function, including the Paired Associates learning test which is a key assessment for early Alzheimer’s, together with tests of reaction time and processing speed. So, how does gut bacteria impact cognitive performance? The brain and gut send messages to one another that can positively or negatively impact each other, says Melissa Prest, D.C.N., R.D.N., national media spokesperson for the Academy of Nutrition and Dietetics and member of the Prevention Medical Review Board. “When our gut microbiome is disrupted, it can lead to various neurological disorders,” such as dementia, she notes. This is because the brain functions best in an environment free from inflammation and free from toxins that are both produced and cleared by the body, explains Amit Sachdev, M.D., director of the Division of Neuromuscular Medicine at Michigan State University.Research has found that people who consume higher amounts of dietary fiber are less likely to develop dementia, says Prest. “While the direct link between fiber and dementia is still being investigated, some reasons why fiber may play a role in reducing the development of dementia include the reduction in blood pressure which protects against vascular dementia, and a healthier gut microbiome which lessens inflammation and protects the brain from developing dementia,” she explains.More specifically, research supports that a meal plan rich in fiber (such as Mediterranean, MIND, and DASH diets) may help prevent cognitive decline and dementia, says Keri Gans, M.S., R.D., registered dietitian and author of The Small Change Diet. Still, keep in mind that forestalling dementia requires using the brain throughout your life, maintaining a healthy body, and avoiding habits that harm the brain, notes Dr. Sachdev.The bottom lineSo, why does this study make a difference? Well, finding an improvement in cognition by fueling the gut microbiome with a prebiotic confirms what other studies have previously reported about the brain-gut axis, says Prest. “Building and maintaining a healthy gut microbiome may be the key to improving age-related changes in cognition.”Adding more fiber to your daily diet is an easy step in the right direction for better brain health later in life, says Gans. If you want to start loading up on fiber at mealtime, Prest recommends aiming for 25-30 grams of fiber a day. “You can do this by making half of your grain choices whole grains and choosing more fruits in vegetables during meals and snacks,” she suggests.Dietary supplements are products intended to supplement the diet. They are not medicines and are not intended to treat, diagnose, mitigate, prevent, or cure diseases. Be cautious about taking dietary supplements if you are pregnant or nursing. Also, be careful about giving supplements to a child, unless recommended by their healthcare provider.