How Did We Learn Which Plants Are Safe to Eat? Food Scientists Explain

By Mani Naiker and Joel Johnson

Have you ever eaten a green potato, or a bunch of rhubarb leaves? Hopefully not, because these two plant parts can be toxic to humans. While they may seem edible, they contain chemicals that can make you seriously ill.

Over centuries, humans have learned which plants are safe to eat and which are not, often by combining ancient knowledge with modern science.

The power of plants

Without plants, we would struggle to get the nutrients we need.

Crops such as wheat and rice provide carbohydrates, the body's main source of energy. Fruits and vegetables contain a wide range of vitamins that help us stay healthy.

Plants are also chemical factories. To survive, they produce compounds that deter insects and animals that might eat them. They may also release chemicals that protect them from disease. One example is the tobacco plant, which produces nicotine, a natural alkaloid that helps protect the plant from insect attacks.

Globally, there are tens of thousands of plants that contain toxic compounds. In Australia, we have more than 1,000 native and introduced plant species that can be toxic to humans and animals, under certain conditions. However, humans only consume a small fraction of the world's edible plant species.

What makes a plant toxic?

A key principle of toxicology—the study of what makes something poisonous—is "it's the dose that makes the poison." This means certain toxic compounds are safe to consume, as long as you don't eat too much of them.

Table salt is one example. You likely eat it everyday, but this substance can be harmful in excessive amounts.