Wheatgrass is the young shoot of the common wheat plant, Triticum aestivum, typically harvested 7 to 10 days after sprouting and consumed as a health supplement. The popular method of consumption is juicing, which reflects how the human body processes the plant material. Humans cannot fully break down wheatgrass due to a specific biological limitation. While the structural components pass through the digestive system whole, the concentrated internal nutrients become available only if the plant’s cell walls are physically broken before consumption.
The Core Challenge: Cellulose and Cellulase
The reason humans cannot fully digest wheatgrass lies in cellulose, the complex carbohydrate that forms the structural component of all plant cell walls. Wheatgrass cell walls are composed of long chains of glucose molecules linked by beta-1,4-glycosidic bonds. This arrangement makes cellulose tough and resistant to the standard digestive enzymes found in the human gastrointestinal tract.
Human digestive systems use enzymes like amylase to break down starches (alpha-bond glucose chains), but they lack the enzyme necessary to hydrolyze the beta-bonds of cellulose. This missing enzyme is called cellulase. Since the human body does not produce cellulase, the rigid cellular structure of wheatgrass remains intact as it travels through the stomach and intestines.
This contrasts sharply with true herbivores, such as ruminant animals like cows. These animals host specialized microbes and bacteria in their complex digestive systems. These symbiotic microorganisms produce the necessary cellulase, allowing the animal to break down cellulose and access the nutrients within the plant cells. For humans, the unbroken cellulose simply passes through, functioning only as indigestible fiber.
Juicing Versus Eating Whole Wheatgrass
The method of consuming wheatgrass determines whether the available nutrients can be absorbed. Chewing or eating whole wheatgrass is ineffective for nutrient assimilation, as human teeth and stomach acids cannot sufficiently rupture the tough, fibrous cell walls. The intracellular contents, which hold concentrated vitamins and minerals, remain trapped and are excreted from the body with the intact cellulose.
Juicing or blending the wheatgrass bypasses this natural digestive limitation by performing the mechanical breakdown externally. The process physically shears and pulverizes the plant material, rupturing the cellulose walls before consumption. This action releases the internal liquid contents, rich in nutrients, into a form the human digestive tract can readily absorb.
This liquid extract can enter the bloodstream quickly without requiring complex chemical digestion. The liquid form allows the body to absorb the released compounds directly through the intestinal lining. This mechanical liberation of the cellular contents is the most important factor that makes wheatgrass a viable nutritional supplement.
What Nutrients Are Absorbed
Once mechanical breakdown from juicing occurs, beneficial compounds locked inside the plant cells become available for human absorption. A notable constituent is chlorophyll, the green pigment responsible for photosynthesis, which is structurally similar to hemoglobin in human blood. Wheatgrass is also a source of vitamins, including A, C, E, and B-complex vitamins.
The liquid form delivers several minerals, such as iron, calcium, magnesium, potassium, and zinc, into the digestive system. Furthermore, wheatgrass provides a profile of amino acids, the building blocks of protein, many of which are essential. While these beneficial components are absorbed, the indigestible cellulose continues its path through the intestines, contributing roughage that aids in digestive regularity.