Age-associated changes in the gut microbiota include a decrease in microbial diversity, an increase in the abundance of potentially harmful bacteria, and a decrease in the abundance of beneficial bacteria. In particular, there is often an increase in the abundance of potentially pathogenic bacteria, such as Proteobacteria, and a decrease in the abundance of beneficial bacteria, such as Bifidobacteria. These changes can contribute to a variety of health issues that are more common in older adults, such as constipation, inflammation, and impaired immune function.