The question of eating common grass, like the turf found in a lawn or field, involves complex biological and safety discussions. While grass is technically non-toxic, it offers no nutritional value for humans and is generally indigestible. The human digestive system is not equipped to process the plant’s tough structural components. Understanding why grass is unsuitable requires looking closely at our biology and the unseen hazards that often coat the blades.
The Immediate Biological Response
The primary reason humans cannot digest grass is the high concentration of a complex carbohydrate called cellulose, which forms the rigid cell walls of the plant. Cellulose is essentially a chain of glucose molecules linked together by beta-1,4 bonds, which our body cannot break apart. Unlike herbivores, such as cows, humans do not possess the necessary digestive enzyme, called cellulase, to cleave these specific chemical bonds.
We also lack the specialized digestive anatomy required for processing such tough plant material. Ruminants, like cattle, have a multi-chambered stomach system designed to house symbiotic microbes that produce cellulase and ferment the plant matter. Humans have a simple, single-chambered stomach and a relatively short intestinal tract, which is not suited for the extensive fermentation needed to break down cellulose-rich foods.
When grass is ingested, the cellulose passes through the human digestive tract largely intact, acting as insoluble fiber. This material can lead to physical discomfort, including abdominal bloating, gas, and stomach upset, as the body struggles to pass the tough, fibrous mass. Consuming a significant amount of grass could potentially lead to intestinal blockages, which are serious medical concerns, due to the material’s highly fibrous and poorly chewed nature.
Hidden Hazards and Contaminants
Beyond the issue of indigestibility, the greatest danger associated with eating common lawn or field grass comes from external factors. Most residential lawns and public fields are treated with chemical products intended to control pests and weeds. Ingesting grass that has been recently treated with pesticides, herbicides, or fungicides can lead to acute toxicity, even in small amounts.
Lawn chemicals, such as certain pyrethroids, are designed to be toxic and can cause severe health issues if consumed. Furthermore, grass blades are frequently exposed to animal waste from dogs, birds, and other wildlife.
This contamination introduces a high risk of ingesting human pathogenic bacteria, such as E. coli and Salmonella, or various parasites. Grass can also harbor mycotoxins produced by molds and fungi, especially when the plant material is damp or decaying, which can cause illness if consumed.
The physical environment of a lawn also means the grass may conceal small, non-biological debris, such as tiny pieces of glass, metal, or sharp pebbles, which pose a risk of causing injury to the mouth or digestive tract.
When Grass is Food
While common turf grass is inedible, certain forms of grass are specifically cultivated and consumed for health benefits, such as wheatgrass, barley grass, and oat grass. These products are derived from the young shoots of cereal grains and are typically harvested very early in their growth cycle, often by day ten. At this young stage, the plants have a higher concentration of simple sugars, vitamins, and minerals, and a lower concentration of the indigestible cellulose.
These grasses are usually consumed as a juice or a fine powder, which mechanically breaks down the rigid plant cell walls. Juicing bypasses the human body’s inability to digest cellulose by releasing the valuable nutrients before ingestion. The controlled cultivation of these grasses also eliminates the risk of contamination from pesticides and animal waste associated with common lawn grass.
The consumption of these specific grass juices is for nutrient absorption, unlike trying to eat a mature, cellulose-rich lawn for caloric energy. For instance, wheatgrass is valued for its high chlorophyll content and various amino acids, which may aid in digestion and detoxification. This preparation and source material difference distinguishes a health supplement from an indigestible lawn clipping.