How plants defend themselves

When animals feel threatened, they posture, fight or flee.

Plants don’t have the same options—they are rooted to the spot.

However, plants are not defenseless—they have evolved many strategies for warding off hungry animals.

Like animals, plants do not want to be eaten.

And they’ve been refining their defensive capabilities for an extremely long time.

The 800-million year war

For approximately 800 million years, the animal and plant kingdoms have been engaged in an arms race of epic proportions.

Here’s the basic idea;

— Many animals eat plants as food.

— Many plants aren’t so keen on being eaten.

In order to survive and reproduce, plants have been forced to develop mechanisms for dealing with animal predation.

Animals have also innovated, to keep pace with plants.

How plants protect themselves

Where animals mostly use speed, agility, and physical weapons (horns, teeth etc.) to protect themselves, plants mostly rely on defence chemicals.

Plants thus exist on a toxicity spectrum.

Tens of thousands of these plant-made ‘pesticides’ have been discovered.

Here’s a short list of the most important ones in relation to human nutrition;

• Lectins

• Oxalates

• Cyanides

• Phytic acid

These defence chemicals can cause;

• A bad taste in the mouth

• Indigestion

• Lethargy

• Forgetfulness

• Poor nutrient absorption

• Severe gastrointestinal distress (acute and chronic), and

• Internal organ damage/dysfunction/failure

Herbivores, and other specialist plant-eaters have evolved counter-measures—specialised anatomy and enzyme systems—that efficiently detoxify plant chemicals and digest plant matter.

However, humans are omnivores, not herbivores.

Modern humans—driven by well-intentioned, but misguided notions surrounding nutrition, sustainability and ethics—consider plant foods as something we can eat without concern, ad libitum.

This is not true.

Humans haven’t evolved the necessary mechanisms for dealing with a high intake of plant matter and defence chemicals.

Humans can eat some plant foods, but we need to choose and prepare them carefully.

Ultimately, we are more specialised towards eating animal foods.

Our ancestors knew this.

This is why following in their dietary footsteps is so important.

The most protected, least edible parts of plants

Plants—just like animals—want their babies survive, and reproduce.

In order to reproduce successfully, life needs a few things;

1. Parents that are fertile (not usually a problem for plants, but a massive issue for modern humans)

2. A protective, safe environment, and

3. Access to nutrients

For humans, we physically protect, and feed, our young until they can take care of themselves.

Plants have similar goals, but leverage different methods.

Seeds, beans, legumes and grains are plant babies.

Plants, like animals, want to create the safest environment possible for their young, to further their plant lineage.

As you know, they can’t physically defend their young—they do it chemically.

Seeds are the most protected, least edible part of a plant.

Cross-section of a plant baby (seed)

Seeds, beans, legumes and grains have three layers;

1. An outer shell, providing physical and chemical protection.

2. An internal macronutrient layer (carbohydrate) providing just enough nutrients to germinate, so the seedling can put down roots (to access water and nutrients) and grow leaves (to capture sunlight).

3. Another deeper layer, containing essential macros, micros, and genetic information.

Seeds are kinda similar to eggs.

Eggs also have three layers—a hard shell to provide physical protection, an internal macronutrient layer (protein) that provides the building blocks of animal tissues, and the yolk—containing essential macros, micros and genetic information.

Here’s one major difference between seeds and eggs—eggs do not contain defence chemicals.

Animal foods do not contain defence chemicals

Sure, some animals, like snakes, have lethal poisons.

However, unlike plants, the edible tissues of most animals do not contain toxic substances (that give humans brittle bones, and gut issues).

Once we kill the animal (having successfully avoided being gored to death) the hard work is done, and we can usually eat it without concern.

By the way, if we know what we’re doing, we can still eat things like snakes too.

Whereas, when it comes to the plant kingdom, we need to be much more careful than that.

We need to ask a few questions;

— Which plants are most edible/nutritious for humans?

— Which plant foods require the least preparation?

— Which part of plants do the plants actually want animals to eat?

Most edible parts of plants that require the least preparation

This list is quite short.

• Fruit

Plants that produce fruits actually want animals to eat them.

Ideally, the animal eats the fruit, spits out the seeds (or swallows the seeds whole, and the next day, deposits them in a nice pile of fertiliser) in a new area. This mutually-beneficial relationship helps the plant expand its territory, and offers the animal a tasty reward for helping out.

Other parts of a plant that also contains defense chemicals

We’ve already covered the most highly-defended parts of plants;

Their babies—seeds, beans, legumes, and grains.

Here are some other parts of the plant we might not want to eat lots of either;

• Roots

• Stems

• Leaves

Yes indeed—spinach, kale, broccoli and such things may not be our best friends after all.

Tolerance to plant foods

Although humans are specialised towards consuming animal foods, we can (theoretically) tolerate a certain amount of plant-foods—defence chemicals and all.

In practicality, though, it’s not so simple.

We first need to be aware of which plant foods are most edible.

Then, we need the time, knowledge and skills to prepare them properly.

Even then, there’s another major consideration;

Our tolerance—of plant matter and defence chemicals—depends on our current state of health and function.

Gut health, in particular.

For modern humans, this is especially poignant.

Gut dysfunction, and gut-related diseases are extremely prevalent in the modern world.

If humans eat plant foods without considering the type, our current state of health, or how much additional stress these foods (like grains—bread—gluten) place upon our digestive and detoxification systems, we are going to run into trouble.

Gut issues and autoimmune diseases are not fun.

This consideration—of individual tolerance to plant foods—warrants careful attention from all of us.

Mandating the consumption of ‘vegetables’ is a problem.

Recap

— Plants are not stupid—they have their own ways of dealing with predation.

— Where animals typically defend themselves with physicality, plants defend themselves with chemicals.

— Animal foods do not contain defence chemicals—one of many reasons they are higher-quality foods for humans.

— If we want to eat plant foods, in order to avoid chronic health issues, like gut/autoimmune diseases, humans need to understand which plants, and parts of plants, are safest to eat.

— Especially for plant foods, like grains, we would be wise to educate ourselves on how to minimise the risk and maximise the reward. We can leverage traditional food preparation methods—like using fermentation to make sourdough bread—in order to achieve this—but be aware that these methods offer harm reduction, not complete harm elimination.

— Consider your individual tolerance, and current state of gut health and overall wellbeing when choosing to eat plant foods.

There’s no free lunch.

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References

Ames, BN, Profet, M & Gold, LS 1990, ‘Dietary pesticides (99.99% all natural).’, Proceedings of the National Academy of Sciences, vol. 87, no. 19, pp. 7777–7781.

Frost, CJ, Mescher, MC, Carlson, JE & De Moraes, CM 2008, ‘Plant Defense Priming against Herbivores: Getting Ready for a Different Battle’, Plant Physiology, vol. 146, no. 3, pp. 818–824.

Mortensen, B 2013, ‘Plant Resistance against Herbivory’, Nature Education Knowledge, p. 8.

War, AR, Paulraj, MG, Ahmad, T, Buhroo, AA, Hussain, B, Ignacimuthu, S & Sharma, HC 2012, ‘Mechanisms of plant defense against insect herbivores’, Plant Signaling & Behavior, vol. 7, no. 10, pp. 1306–1320.

Wöll, S, Kim, SH, Greten, HJ & Efferth, T 2013, ‘Animal plant warfare and secondary metabolite evolution’, Natural Products and Bioprospecting, vol. 3, no. 1, pp. 1–7.