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Myth busting – Part 7

Myth: Plants are healthy, they are ‘all good’ and we can eat as much as we like.


Truth: No! Many plants contain all sorts of chemical compounds that are extremely harmful to human health! You can’t eat poison ivy! What about deadly nightshade! Apple pips contain cyanide! What about gluten! There are highly poisonous mushrooms and numerous deadly herbs. The list is long! But among the common plants we do eat, there are plant foods containing compounds such as lectins, goitrogens, protease inhibitors, amylase inhibitors, phytate (or phytic acid), tannins, saponins and calcium oxalate, as well as some lesser compounds that are not very good for us.

The reality is that more than 90% of the biomass of plant life on Earth is completely unavailable to humans as food. We cannot eat grasses, we cannot eat trees, and most leaves are indigestible to us. We cannot eat grains unless we process them, and estimates suggest that around half the human population is intolerant to gluten to one degree or another. Raw potatoes will make you sick. Legumes are rich in lectins that upset digestive function. Phytates, or phytic acid, found in legumes, nuts and grains, have ‘anti-nutrient’ properties, leaching other valuable minerals from your body.

Many of these compounds are enzyme inhibitors of one type or another – that is, they stop various digestive enzymes from doing their job properly, meaning your body cannot absorb some of the minerals that you consume in your food.

And you thought plants were good for you!!!!

The truth is, a large proportion of plants are unsuitable for eating, and much of the vegetables and fruits we do eat were never naturally as abundant as they are today, before man engaged in agriculture. In short – before we started farming, there was never enough edible plant matter on Earth to support a large human population. The inconvenient truth is that we rose to become the dominant species on the planet by eating other animals – in fact the fossil record bears witness to the fact that between 100,000 years ago and 5,000 years, we pretty much wiped out shutterstock_159245855every other large beast (known as megafauna) on Earth. As anatomically modern man spread out and colonized every part of the globe, we killed and ate everything that got in our way. Then we learned to domesticate beasts, and started keeping them and ‘growing them’ for food.

Now, obviously I am not trying to demonise plants! I eat a lot of fresh vegetables, I’m the 17-a-day guy, Mr MND! Vegetables and fruits make up half of all the calories I eat, and plants are a wonderful source of vitamins and minerals, and beneficial dietary fibre. But this series of blog posts is about myth busting, and I am simply trying to shift these long held beliefs you may have around food and what constitutes ‘natural and healthy’. We like to think of plants as happy, benign little things, standing there defenceless in the sunshine, hoping it might rain at some point in the day.

But that’s just not true!

Teeth, claws and chemical weapons

Animals have many ways to defend themselves from predators – they can run, fly or swim away. They have claws, teeth and venom to defend themselves. Frogs can shoot poison darts, fish can raise spines, a lion can easily rip your head off! But plants have no such defences; they are rooted to the Earth and stand there, open to predation (this is why farmers spray them with pesticides!), so they have developed a whole different set of defences. Some have spikes, thorns or stings, and some grow high enough above the ground to be out of reach of grazing mammals, but in the overwhelming majority of cases plants use ‘chemical warfare’ as their principle form of defence.

We are aware of most of the really highly poisonous plants we must avoid. Humans, like other mammals, have evolved ways to detect these chemical ‘weapons’ – unpalatable bitter tastes, pungent smells, indigestibility, irritation on touch – these tend to be Nature’s way of telling us not to eat certain plants. However, some signs are more subtle than others. Many seemingly edible plants actually contain compounds that are ‘less than optimal’ to human health, and these compounds can cause varying degrees of problems in humans depending on the susceptibility of the individual.

This is where gluten, lectins, goitrogens, enzyme inhibitors, phytate, saponins and others come in to the human diet. Some folks are gluten tolerant, for others gluten will wind them up in hospital. Some folks can’t eat raw green vegetables because the goitrogens disrupt thyroid function. Some folks have to avoid beans and pulses because the phytate in legumes stop your gut from properly absorbing some of the calcium, iron, zinc and magnesium in your food. If you are prone to anaemia, or recovering from anaemia, this can be a real problem. Some people can eat peanuts all day, for others just touching a peanut to their lips can cause an emergency medical reaction.

This post is not the place to go into every compound in detail, because honestly the topic of ‘compounds in plants that may cause digestive problems’ could fill an entire book. Today, as part of this Myth busting mini-series, I just want you to understand that plants are not an ‘endless wonder food’ for all, they really are not that ‘dream superfood’ that gives life and health to all people. That’s just not true. The reality is that most plant life on planet Earth is biologically unavailable to humans as a food source, and of the few percent of plants that we can digest, many people suffer intolerance’s to compounds in those plants and are best off avoiding them completely.

Our green and pleasant land may be beautiful to gaze upon, but that doesn’t automatically mean we can run out there are eat it! As with most things health-related, there is no ‘one size fits all’ and usually some moderation is key. While I broadly teach consuming a ‘nutrient dense’ diet as a key to good healthy living and abundant energy, everyone is different, and if an individual has specific health challenges, then tailored dietary advice may be required. Someone suffering anaemia may need to avoid nuts and beans, someone with low thyroid function should probably avoid raw cruciferous vegetables, and so on.


And while ‘5-a-day’ may be inadequate in our modern world, and 10-a-day or 15-a-day is a much better target to aim for, that does not mean that 30-a-day or 40-a-day is some kind of nutritional nirvana. It is possible to ‘overdose’ on plant foods, so to speak. It is possible to eat too much of one mineral, at the expense of digesting others, and some compounds work best in your body in balanced quantities (certain minerals and fats), rather than just ‘more more more’ mentality.

In Myth busting – Part 8 (coming up next) we will look into this balance between plant foods and animal foods a little more closely. We will see how nutrients from animal foods are often more bio-available for human digestion, and don’t come with these anti-nutrient compounds to deal with.

For most people, the compounds mentioned above are of little practical concern, but for those choosing to follow a vegetarian diet high in grains, nuts, beans and seeds, or for those eating a raw food diet, these anti-nutrient compounds may become a problem, and can lead to nutritional deficiencies.


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