Common lawn grass, while seemingly abundant, offers little to no nutritional benefit for humans. This article explores its components, why human digestion is unsuited for it, how herbivores extract nutrients, and safety considerations.
Nutritional Components in Grass
Common grass contains various biological and chemical components, similar to other plant matter. It is rich in cellulose, a primary structural component of plant cell walls, which provides fiber. Grass also contains chlorophyll, the green pigment essential for photosynthesis, along with some vitamins like K, A, C, and E. Minerals such as iron, calcium, magnesium, potassium, zinc, and manganese are also present. Despite these compounds, their accessibility and bioavailability to the human body are significantly limited, as they are bound within the plant structure.
Why Humans Cannot Digest Grass
The primary reason humans cannot derive nutrition from grass lies in its complex carbohydrate, cellulose. Cellulose consists of long chains of glucose molecules linked by beta-1,4-glycosidic bonds. The human digestive system lacks the specific enzyme called cellulase, necessary to break these unique bonds.
In contrast, human digestive enzymes break down alpha-glycosidic bonds found in starches. Since cellulase is absent, cellulose passes through the human digestive tract largely undigested. This undigested cellulose contributes to dietary fiber, beneficial for bowel function, but provides no caloric energy or absorbable nutrients. Additionally, grass contains lignin, a woody polymer that further contributes to its indigestibility for humans.
How Herbivores Process Grass
Unlike humans, herbivores like cows, sheep, and horses possess specialized digestive systems capable of breaking down cellulose. Ruminants, such as cows, have a multi-chambered stomach, including a large compartment called the rumen. This chamber houses a diverse population of symbiotic microorganisms, including bacteria, fungi, and protozoa, that produce the cellulase enzyme.
These microorganisms ferment the cellulose, breaking it down into simpler compounds like volatile fatty acids, which the animal then absorbs for energy. Hindgut fermenters, such as horses, process grass in an enlarged cecum and large intestine, where similar microbial fermentation occurs. These adaptations allow herbivores to efficiently extract significant nutritional value from a grass-based diet.
Safety and Specific Types of Grass
Consuming common lawn grass presents several safety concerns. Lawn grasses are often treated with pesticides, herbicides, and other chemicals that can be harmful if ingested. Additionally, common lawns may harbor animal waste, parasites, or other microorganisms that could cause illness. The silica content in grass can also be abrasive and potentially damaging to human teeth.
It is important to distinguish common lawn grass from specific “grasses” marketed for human consumption, such as wheatgrass and barley grass. These are typically harvested at an early growth stage and processed into juices, powders, or supplements. Wheatgrass and barley grass are valued for their concentrated nutrients, including chlorophyll, vitamins A, C, E, K, and various minerals and amino acids. These products bypass the need for direct cellulose digestion by humans and are cultivated under controlled conditions to minimize contaminants.