Dementia is a cluster of symptoms that impair memory, thinking, and social abilities in older adults. Alzheimer’s disease is the most common cause, but dementia can also result from other diseases, such as stroke. According to the World Health Organization, dementia is the seventh leading cause of death worldwide. Previous research has shown that diet, particularly one rich in produce, whole grains, and nuts and seeds, may play a role in reducing dementia risk. Most recently, the results of a Japanese study published in early February suggest that a diet high in fiber is associated with a reduced risk of developing dementia later in life. If consuming a high-fiber diet becomes a standard recommendation to help prevent dementia, GlobalData epidemiologists expect that total prevalent cases of dementia could decrease among older adults in Japan. 

The study, conducted by Yamagishi and colleagues and published in Nutritional Neuroscience, followed over 3,700 participants enrolled in the Circulatory Risk in Communities Study, an ongoing community cohort involving five communities in Japan. Healthy participants, then 40–64 years of age, underwent health checkups from 1985 to 1999 that included a 24-hour dietary recall survey. During the follow-up period from 1999 through 2020, 670 incident cases of disabling dementia were observed. The authors found that dietary fiber intake was associated with a reduction in dementia risk, a relationship that strengthened across groups of increasing dietary fiber intake. The link with reduced dementia risk was particularly strong for intake of soluble fibers, which are found in foods such as oats and legumes.

In Japan, GlobalData epidemiologists expect total prevalent cases (which includes diagnosed and undiagnosed cases) of dementia in men and women to increase over the next decade, approaching 12,000,000 by 2028 (as shown in Figure 1). However, if specific dietary recommendations, including increased fiber intake, to reduce dementia risk are established and widely adopted, total prevalent cases could fall below those currently forecast as new cases of dementia are prevented.

In many countries, including the US and Australia, people consume less fiber than nutritionists recommend. A diet high in fiber is important for maintaining a healthy digestive system and also reduces cholesterol. The results of the current study need to be confirmed by additional observational or intervention studies and in other populations, but reducing dementia risk may be yet another benefit of incorporating more fiber into one’s diet.