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Why Can’t Humans Eat Grass? (With 4+ Surprising Edible Grass Types)

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The smell of freshly mowed grass is one of the most pleasant, mouth-watering scents. There are perfumes designed that try to recreate that scent. So why can’t humans eat grass, despite it smelling so heavenly?

You aren’t the first person who has had this question in mind. At some point in our life, in our childhood, everyone has had the question ‘why can’t humans eat grass’ in their mind. And upon inquiry, they found out that grass isn’t something we consume. But is that true? And if so, ‘why can’t humans eat grass?’.

We’re here to answer the question, ‘why can’t humans eat grass’, and tell you the exact science behind the answer. If you’re curious to find the answer, keep on reading!

Why Cant Humans Eat Grass
Two rhinoceros eating grass together… – via Flickr

Why Can’t Humans Eat Grass

Humans Can’t Digest Cellulose!

We know that grass is a plant, and we also know that plant cells have cellulose. Cellulose is one of the most common organic polymers on this planet. The cell wall of green plants and many forms of fungi and oomycetes is made of cellulose.

It’s a significant part of the plant’s cell structure because it helps cells hold their shape. It keeps the cell erect and sturdy.

Cellulose is the perfect polymer for the job because of its primary structure, which is long chains of glucose units attached. These chains can hydrogen-bond together, which gives cellulose immense strength and stability.

This strength and stability make cellulose the perfect component for grass. But it also makes grass inedible for humans. Why? Because humans don’t have the enzyme required to digest cellulose.

Enzymes are biological catalysts that speed up chemical reactions in the bodies of living organisms. They are significant in the human body. Enzymes are located in many parts of the body including the pancreas, stomach, intestines, and saliva. Without these protein catalysts, bodies might not be able to function.

In the human body, each enzyme has a specific function. Enzymes work in a lock-and-key manner, where each enzyme can only work with a particular substance.

For example, lipase breaks down fats into fatty acids, and carbohydrase breaks down carbohydrates into sugars. Only after breaking down into smaller components can these substances be digested by the human body.

Similarly, the enzyme needed to break down cellulose into its digestible form is called Cellulase. Cellulase breaks down cellulose into glucose molecules, which are easy to digest. However, the human body does not possess this enzyme.

Because humans can’t digest grass, there is no point in eating it. It has no nutritional benefits for humans. The human body discards grass without absorbing any nutrients because grass has a huge amount of cellulose.

So even if the grass in your lawn smells delicious, that doesn’t mean the grass is a viable diet option for humans. The grass is non-toxic but eating it is pointless because it serves no nutritional benefits.

Eating Grass Can Make You Sick!

Yes, that’s true. Even though the grass is non-toxic and has no poisonous elements, it can still be harmful to the human body.

Grass has silica in it. This silica can cause abrasion of tooth enamel when consumed by humans. Tooth abrasion can lead to increased tooth sensitivity to hot and cold.

It can make your teeth more open to problems like plague and bacteria and might end up causing severe gum infection, which might eventually lead to tooth extraction.

Eating grass can also cause extreme discomfort in your stomach. It might start from growls in your stomach and stomach aches, and will end in diarrhea. Diarrhea can further cause dehydration in the human body.

So yes, eating it as a snack or just for fun is unadvisable and unhealthy.

Can Other Mammals Consume Grass?

Yes, all herbivores like cows, goats, and sheep can eat grass. Unlike humans, cows have a stomach with four chambers and have cellulose enzymes, enabling them to break down the cellulose into smaller glucose molecules that are easier to digest and helping the cow to absorb any nutrients from grass.

There was even a time when humans were able to digest grass. Well, technically not humans, but an older, unevolved hominid version called Australopithecus Bahrelghazali. The grass used to be one of their favorite snacks, and they weren’t the only hominid to have a liking for raw grass. 

It is said that because in the old days there was no fire, unevolved humans were adapted to eat raw food like grass. But after the discovery of fire, and cooking, slowly humans started to lose that ability.

Edible Grasses

As discussed earlier, humans can’t just pick grass out of their lawn and start eating it, but some types of grass are consumed by people around the world and are digestible and healthy. The following are the names of some of them.

Wheat Grass

Raw wheatgrass isn’t harmful if it’s only consumed in small amounts. It is however more often turned into a juice.

Wheat Grass Why Cant Humans Eat Grass
Wheat Grass – via Wikimedia


Alfalfa is another example of grass that can be consumed raw. It is considered to be a source of calcium, potassium, phosphorus, vitamins, and iron.

Barley Grass

This grass can be eaten raw and is a great source of vitamins A and C. But it is popularly consumed as a juice in the morning.

Lambs Quarters

These are a great source of protein and iron and are usually referred to as weed.


These are some other edible grasses:

  • Bent
  • Brome
  • Slough
  • Crab
  • Switch
  • Canary
  • Timothy
  • Blue


This article gives you the answer to the question, ‘why can’t humans eat grass?‘. The cellulose in the grass makes it inedible for humans, who don’t have the enzymes to digest this substance, unlike many herbivore mammals and hominids in the old ages.

Eating grass can be harmful to the human body. It can cause tooth enamel abrasion, stomach pains, and diarrhea. So it’s better to consume grasses that are digestible like wheatgrass, alfalfa, barley grass, lambs, and many others.

We hope this helped you find the answer. If you have any questions, comment them down below.