Can You Get Fiber from Grass? The Surprising Digestive Science Explained

An impressive 70-75% of grass hay is high-quality fiber, a statistic that might lead one to ask: can you get fiber from grass? However, for humans, the answer is a firm no, as our digestive systems are not equipped to break down the fibrous plant material effectively.

Quick Summary

Humans cannot obtain fiber from grass because our bodies lack the necessary enzymes to break down the tough cellulose found in its cell walls. Unlike ruminants, our digestive system is not designed for fermenting tough plant fibers.

Key Points

• No Human Digestion: Humans lack the necessary enzyme, cellulase, to break down the tough cellulose fiber found in grass.

• Digestive Differences: Unlike humans, herbivores like cows have multi-chambered stomachs and symbiotic bacteria to ferment and digest cellulose.

• Nutritional Barrier: Nutrients locked inside grass's cell walls are largely inaccessible to the human body.

• Grains are Different: The seeds of domesticated grasses, such as wheat and rice, are digestible and provide fiber, unlike the fibrous blades.

• Abrasive Silica: Grass contains abrasive silica that is not suitable for human teeth, which are not designed for continuous grinding.

• Focus on Digestible Fiber: To increase fiber intake, focus on fruits, vegetables, and whole grains, which contain fiber our bodies can utilize.

The Biological Barrier: Why Humans Can't Digest Grass

At the core of the issue is cellulose, a complex carbohydrate that forms the rigid cell walls of plants like grass. While cellulose is a type of fiber, the human digestive system lacks the enzyme, called cellulase, that is required to break it down into digestible sugars. For us, consuming grass results in the cellulose passing through our digestive tract largely unchanged, offering minimal nutritional benefit beyond indigestible bulk. In contrast, the valuable nutrients locked within the plant's cells, such as protein, fats, and vitamins, remain inaccessible to us when consumed this way. The harsh, fibrous nature of grass, which also contains abrasive silica, can also wear down human teeth not adapted for continuous grazing.

Comparing Digestive Systems: Human vs. Herbivore

The dramatic difference in how we process plant matter is best illustrated by comparing the human digestive system with that of herbivores, particularly ruminants like cows and goats. These animals have evolved highly specialized systems to extract maximum nutrition from fibrous plant foods.

Here’s a comparison of how different digestive systems handle grass and other fibrous plants:

Feature	Human Digestive System	Ruminant Digestive System
Stomach	Single-chambered.	Four-chambered (rumen, reticulum, omasum, abomasum).
Enzymes for Fiber	Lacks cellulase.	Relies on symbiotic bacteria and microbes in the rumen to produce cellulase.
Digestion Process	Primarily enzymatic breakdown in the stomach and small intestine.	Primarily fermentation in the rumen, followed by rumination ('chewing the cud') and enzymatic digestion.
Nutrient Absorption	Efficient absorption of proteins, fats, and simple carbs.	Absorbs nutrients released by microbial fermentation and the digestion of the microbes themselves.
Plant Cell Digestion	Ineffective at breaking down plant cell walls.	Highly effective, uses specialized bacteria to break down tough cellulose.

The Kinds of Fiber in Grass and How We Still Benefit from Grass Family Plants

While the tough cellulose in mature grass is indigestible for humans, it is important to distinguish between different types of fiber and how we can still benefit from plants in the grass family (Poaceae).

Types of Fiber:

• Cellulose: An insoluble fiber that constitutes a major structural component of grass. It passes through our system without being digested, but adds bulk to stool.
• Hemicellulose and Lignin: Other structural components of plant cell walls, also largely indigestible by humans.
• Wheatgrass and Barley Grass: When harvested young, these grasses contain sugars, vitamins, and minerals that are more accessible through juicing, as the fibrous pulp is discarded.
• Seeds from Grasses (Grains): Humans primarily consume the seeds of cultivated grasses, which we call grains (e.g., wheat, rice, corn). These seeds are rich in carbohydrates and fiber that are digestible and have been selectively bred for thousands of years to be a vital part of our diet.
• Sugar Cane: The sap of this grass family plant can be processed to create digestible sugar, with the indigestible fibrous material removed.

Safely Adding Fiber to Your Diet

Since eating grass is not a viable or healthy way for humans to get fiber, it's crucial to rely on digestible, nutritious sources. A balanced diet rich in various fruits, vegetables, grains, legumes, and nuts is the best approach to ensure adequate fiber intake. For example, the soluble fiber in foods like oats, apples, and beans can help lower cholesterol and regulate blood sugar, while insoluble fiber from whole grains and leafy greens helps maintain bowel regularity. The National Institute of Diabetes and Digestive and Kidney Diseases provides extensive information on how the human digestive system functions and absorbs nutrients.

Conclusion

In conclusion, while it is technically true that grass contains fiber, humans cannot get fiber from grass in a way that provides nutritional value due to our biological limitations. Our bodies lack the specialized digestive enzymes and anatomical structures present in herbivores like ruminants to process the cellulose. Fortunately, humans have evolved to cultivate and consume other, more digestible parts of grass-family plants, such as the nutrient-rich seeds we know as grains. For a healthy digestive system, it is far more effective and beneficial to consume fiber from traditional sources like fruits, vegetables, and whole grains, which our bodies are well-equipped to handle.

Frequently Asked Questions

Can humans eat grass at all?

Technically, a human can consume grass, as it is non-toxic. However, our bodies cannot digest the fiber within it, meaning it will pass through without providing any significant nutrients and could cause digestive discomfort.

What happens if a person eats grass?

If a person eats grass, it will mostly pass through the digestive system as indigestible fiber. Ingesting large amounts may lead to digestive upset, gas, bloating, and potential tooth wear due to abrasive silicates.

Why can cows digest grass but humans can't?

Cows are ruminants with a specialized four-chambered stomach. They house symbiotic bacteria that produce the enzyme cellulase, which breaks down cellulose. Humans lack this enzyme and the complex digestive tract needed for this process.

What is the difference between eating grass and eating grains?

Grains like wheat and rice are the seeds of grasses. Over centuries, these seeds have been cultivated to be digestible. The fiber and nutrients they contain are accessible to humans, unlike the tough cellulose in the blades of grass.

What is the primary indigestible component of grass for humans?

The primary indigestible component of grass for humans is cellulose, a complex carbohydrate that makes up the cell walls of the plant. Humans lack the enzyme cellulase to break down this molecule.

Do wheatgrass or barley grass juices provide fiber?

Wheatgrass and barley grass are harvested young, and their juices contain some vitamins and minerals. However, when juiced, the insoluble fiber is separated and discarded, so you don't get the fibrous bulk.

What are better sources of fiber for humans?

Better sources of fiber include fruits, vegetables, whole grains (like oats, brown rice, and whole wheat bread), legumes, and nuts. These foods contain fiber our digestive systems can process effectively.