Is it unhealthy to eat grass? The risks and nutritional facts explained

December 22, 2025 •

4 min read

Over millions of years, human digestive systems evolved to process a wide variety of foods, but grass was never one of them. So, is it unhealthy to eat grass, and can humans even digest it for nutritional benefits?

Quick Summary

This article explores the health implications of eating grass, detailing the biological reasons humans cannot properly digest it. It covers the lack of nutritional value, potential digestive issues, and the serious risks posed by pesticides, herbicides, and other contaminants.

Key Points

Indigestible Cellulose: Humans lack the enzymes to break down cellulose in grass, making it largely indigestible and nutritionally useless.
Risk of Chemical Exposure: Lawn grass is often treated with dangerous pesticides and herbicides, which can cause both acute sickness and chronic health issues like cancer.
Dental Damage: The silica found in grass is abrasive and can wear down human tooth enamel over time.
Contamination from Parasites: Consuming grass from unsanitary areas exposes you to harmful bacteria and parasites from animal feces.
Severe Malnutrition: Relying on grass as a food source will inevitably lead to starvation because it provides virtually no absorbable calories or essential nutrients.
Distinction from Wheatgrass: Specialized health foods like wheatgrass are consumed as juice or powder, separating the nutritious contents from the indigestible fiber.
Survival Inadequacy: In a survival scenario, grass is not a viable food source; it may temporarily fill the stomach but offers no real energy and carries significant risks.
Seek Medical Help if Needed: If chemicals are suspected, contact poison control. For repetitive consumption of non-food items, consult a healthcare provider.

The Inability to Digest Cellulose

The fundamental reason humans cannot live on a diet of grass is our inability to digest cellulose. Cellulose is a complex carbohydrate that forms the tough, rigid cell walls of plants, providing them with structure. While it's a potential source of energy, humans lack the enzyme, cellulase, required to break down the beta-acetyl linkages in its molecular structure.

Unlike humans, ruminant animals such as cows, sheep, and goats have specialized digestive systems. Cows, for example, have a multi-chambered stomach system that houses symbiotic bacteria and protozoa, which produce cellulase. This allows them to ferment and break down cellulose effectively, extracting nutrients. Our single-chambered stomach and short intestinal tract are not suited for this process. For humans, grass is largely indigestible roughage, passing through the system with little to no nutritional absorption.

Comparing Digestive Systems


Feature	Human Digestive System	Ruminant Digestive System (e.g., Cow)
Stomach Type	Single-chambered	Multi-chambered (four parts: rumen, reticulum, omasum, abomasum)
Enzyme for Cellulose	None produced	Symbiotic bacteria produce cellulase
Digestion Process	Breakdown of proteins, fats, simple carbs	Fermentation of cellulose in rumen, repeated chewing (rumination)
Nutrient Extraction	Cannot extract nutrients from cellulose	Highly efficient at breaking down tough plant fibers
Diet	Omnivorous; varied diet required	Herbivorous; adapted for a low-nutrient, high-volume grass diet

Significant Health Risks Beyond Digestion

Eating grass presents several serious health risks, making it not only unbeneficial but potentially harmful.

1. Pesticides and Herbicides

Most lawns and public green spaces are treated with chemicals to control weeds, insects, and other pests. Ingesting these substances is extremely dangerous. Exposure to common lawn chemicals has been linked to numerous health issues, including:

Acute toxicity: Causing nausea, vomiting, and abdominal pain.
Chronic health problems: Repeated exposure is associated with an increased risk of cancer, kidney damage, and endocrine disruption.

2. Physical Abrasions from Silica

Grass blades contain silica, a naturally abrasive compound. While grazing animals have adapted teeth that continually grow to withstand this, human teeth are not equipped for it. Chewing grass regularly can cause significant wear and tear on tooth enamel, leading to dental problems over time.

3. Contaminants and Parasites

Grass is an open environment for various contaminants. It can be exposed to animal feces, which carry bacteria, viruses, and parasites like roundworms. Ingesting grass from an untreated or unsanitary area poses a clear risk of contracting infectious diseases or parasitic infections.

4. Digestive Distress and Malnutrition

Since the human body cannot process cellulose, consuming large quantities of grass will lead to digestive upset. This can result in symptoms such as stomach cramps, bloating, diarrhea, and vomiting. Furthermore, relying on grass as a food source would lead to severe malnutrition, as it provides virtually no usable calories, proteins, fats, or essential vitamins and minerals for humans. In a survival situation, while it might provide some temporary bulk to fill the stomach, it does not prevent starvation.

The Difference between Lawn Grass and Wheatgrass

It is important to differentiate between lawn grass and certain types of grass, like wheatgrass, which are prepared for human consumption. Wheatgrass is a potent health food, typically consumed in juiced or powdered form. The juicing process extracts the vitamins, minerals, and other nutrients from the plant, leaving behind the indigestible cellulose fiber.

How Wheatgrass is Safe to Consume

Processed for digestion: Juicing separates digestible nutrients from indigestible fiber.
High nutritional content: Rich in vitamins A, C, E, and K, as well as iron, calcium, and magnesium.
Grown in controlled environments: Cultivated specifically for human consumption, minimizing the risk of contaminants like pesticides and parasites.

A note on wild grasses

Even if a wild grass is not inherently toxic, it should not be consumed without expert knowledge. Many species exist, and some can be poisonous. Proper identification is crucial for safe foraging.

Conclusion: Stick to Edible Plants

While eating a small amount of untreated grass is unlikely to cause serious, immediate harm, it is unequivocally unhealthy and provides no meaningful nutritional benefit to humans. The combination of indigestible cellulose, potential for chemical contamination, physical dental damage, and risk of parasitic infection makes it an ill-advised choice. Instead, focus on a varied diet of fruits, vegetables, and other foods that our digestive system is designed to process effectively to get the nutrients your body needs to thrive.

What to Do If Someone Eats Grass

If a child or adult has eaten a small, untreated amount of grass, monitor for any signs of digestive distress like upset stomach, vomiting, or diarrhea. If the grass was treated with chemicals, seek immediate medical attention or contact a poison control center. If the person repeatedly eats non-food items, it may be a sign of an underlying condition like Pica, and they should be evaluated by a healthcare provider.

Frequently Asked Questions

No, humans cannot get meaningful nutrition from eating grass. Our bodies cannot break down the cellulose, which is the main component of grass blades. For humans, it provides little more than indigestible fiber.

No, it is highly unsafe to eat grass from your lawn. Most lawns are treated with pesticides, herbicides, and fertilizers that are toxic to humans and can cause serious health problems if ingested.

If a child eats a small amount of untreated grass, they might experience an upset stomach, but it is generally not a medical emergency. However, if the grass was treated with chemicals or if the child shows concerning symptoms like vomiting, you should seek immediate medical attention.

Ruminant animals like cows have specialized multi-chambered stomachs containing bacteria that produce the enzyme cellulase, which allows them to effectively break down and digest the cellulose in grass. Humans lack this enzyme and digestive system adaptation.

Yes, chewing grass can be damaging to your teeth over time. The silica within grass blades is abrasive and can cause significant wear on human tooth enamel, which does not regenerate like the teeth of grazing animals.

Lawn grass is inedible and often treated with chemicals. Wheatgrass, a specific young plant, is prepared for human consumption by juicing, which separates the digestible nutrients from the indigestible fiber, making it safe to consume.

Yes, it is possible to contract diseases or parasites from eating grass. Grass is often contaminated with animal feces, which can carry harmful bacteria, viruses, and parasitic organisms like roundworm eggs.

No. Eating grass is never recommended for human consumption. Even in survival scenarios, the minimal to non-existent nutritional value and significant health risks make it a poor and dangerous choice for sustenance.