When we discuss the gut, we’re primarily talking about the small intestine, where 90% of food is absorbed. The quality of health in the gut is dependent on the microbiota (aka gut flora), which is made up of microscopic organisms (e.g., bacteria, viruses, and fungi) living in the intestines. Healthy gut flora—often called “good bacteria”—help with digestion, support immune function, and are even linked to cognitive function and mood.
For proper nutrient absorption, a healthy gut needs microbial diversity, a healthy intestinal lining (which, by the way, vitamin D plays a key role in supporting immune function of the gut mucosa), and the right conditions or buddy nutrients (e.g., some fat for fat-soluble nutrients like vitamin D!).