Seeing a bright yellow corn kernel appear virtually unchanged after passing through your entire digestive system is a common observation. This phenomenon frequently leads people to believe their body cannot digest corn at all. The truth is that this visible kernel is simply the structural remains of the corn’s protective outer layer, which our digestive system is not equipped to break down. This natural process is a normal biological mechanism and does not mean the body failed to extract any nutritional value from the grain. Understanding the structure of the corn kernel and the limitations of human enzymes explains this occurrence.
The Indigestible Barrier
The reason a corn kernel survives the digestive tract is its fibrous outer shell, known as the pericarp or hull. This layer functions as a natural defense mechanism for the seed, protecting the interior from damage and desiccation. The pericarp’s resilience comes from its composition, which is mainly a complex carbohydrate called cellulose.
Humans do not possess the necessary digestive enzyme, cellulase, to break down the specific chemical bonds found in cellulose. This enzyme is produced by some microorganisms and is found in the digestive systems of herbivores, but not in humans. Because the body cannot chemically dissolve this protective coating, the pericarp passes through the stomach and intestines largely intact.
What Parts Are Actually Digested
Despite the apparent lack of digestion, a significant portion of the corn kernel is successfully broken down and absorbed by the body. The indigestible pericarp makes up a relatively small percentage of the kernel’s total mass, estimated to be less than 10%. The majority of the kernel is the interior, called the endosperm, which contains available nutrients.
The endosperm consists primarily of starch, a complex carbohydrate that human enzymes like amylase easily break down into glucose for energy. This inner core also contains protein, small amounts of fats, and beneficial micronutrients. When the hull is compromised, the body gains access to vitamins such as Vitamin C and folate, along with minerals like potassium and magnesium. Corn is also a source of antioxidants, specifically carotenoids, which are absorbed once the protective barrier is breached.
Maximizing Absorption
Nutrient absorption from corn is directly proportional to how well the kernel’s outer barrier is ruptured before it reaches the stomach. The human digestive process cannot penetrate an unbroken pericarp, meaning starches and vitamins inside will pass through unutilized. The most straightforward way to ensure digestion is through mechanical action, specifically by thoroughly chewing each kernel.
Chewing acts as the first line of defense, physically tearing the cellulose wall and exposing the endosperm to digestive enzymes. Beyond chewing, various food processing techniques also serve this purpose. Grinding corn into flour for items like cornmeal or tortillas, or processes like nixtamalization, effectively pre-digests the kernel by removing or dissolving the pericarp. Breaking the kernel’s shell ensures the body can access the approximately 85% of the kernel that is nutritionally valuable.