If you have been researching paleo and animal-based nutrition, you have probably heard that some plant foods are healthier than others. If you want to know how to choose which plants to eat without memorizing or referencing a list, read on!
Plants have evolved to defend themselves in a variety of ways. Their defences are concentrated in areas needed for survival and reproduction. Some plants use animals to spread their seeds, which are inside tasty fruits. Animals can eat these fruits when ripe, and then spread the plant seeds in their poop. Therefore, it is usually much safer to eat the edible fruits, than the plant bodies (leaves, stems and roots) or plant babies (seeds).
Why can eating plants cause harm to your health?
Plants are alive. As living organisms, plants want to grow, develop, and reproduce, and each plant has unique strategies for doing so. This means that, of the estimated 500,000 species of plants, most are inedible for humans. This is in stark contrast to animal flesh, which is almost always safe for humans to eat. This meant that our ancestors had to be very careful to pass down the knowledge of which plants were safe to eat, as a mistake would be deadly.
Plants cannot defend themselves in the way animals can. Animals use fight or flight as a defence strategy; using teeth, claws, spines or pungent odours to fight off predators, or by running away with powerful legs and agile bodies. If a predator can overcome these defences, then that animal cannot reproduce. This means there was no evolutionary adaptation for postmortem defences, such as poison. Plants, however, are usually fixed to the ground by their root system, and therefore need different strategies. Therefore plants had to evolve to protect themselves with mechanisms such as spikes, stingers and poisons.
The majority of plant predators are insects and herbivorous animals. These creatures co-evolved with plants, and thus developed certain adaptations to combat the plant defences, allowing them to eat a specific diet of a few plants (such as grass). However, if an insect or herbivore strayed from their natural diet, and ate a different plant species, they would either stop consuming it and move on, or succumb to the plant’s defences.
Our ancestral diet
For millennia, our human ancestors knew what plants were safe to eat, in addition to the animals they hunted and scavenged. These plants and animals were wild, and grew in their natural form and habitat. We know from stable isotope analysis that humans were apex predators, with a diet even including other predators. We know this because nutrients concentrate up the food chain, and we can see that humans have a greater concentration in their bones than known predators such as wolves.
However, about 10,000 years ago, humans developed the ability to selectively grow plants. Agriculture allowed more permanent settlements to develop, as food was now available closer to the population. Over time, our ancestors learned how to save the seeds of the biggest, tastiest plants, and use them to plant next year. This was the beginning of selective breeding, which created the human developed plants we see in supermarkets today. The produce section looks lush with ripe colour, but nothing found there grows in the wild. Not only are these plants selectively developed for the human palate, they also need a lot of extra inputs, such as pesticides and fertilizers, to survive and grow. As a result, these modern edible plants tend to have higher water and fructose content, making them juicier and sweeter than their natural counterparts, while still containing their original defence mechanisms.
What are plant toxins?
As already stated, each plant species uses a different defence mechanism. As modern humans, we are most interested in the plants that make up the majority of our diets. This includes grains, legumes, nightshades, leafy greens, nuts and seeds. All of these common plant foods contain natural defences that can cause harm to the human body.
All kinds of seeds
Grains, legumes, nuts and seeds are all “plant babies”. They are little packages grown by the mother plants, with the potential to grow into a new plant. It is very important for the plant to protect these “babies”, because the survival of their species depends on it. Through evolution, proteins called ‘lectins’ developed. Plant seeds use these lectins to grow, but they also deter predators by harming them if eaten.
Every modern shopper has heard of gluten, an allergenic protein that is harmful to millions of people suffering from celiac disease or wheat sensitivity. Gluten is the most famous lectin, but there are many more found in plant seeds, such as the deadly ‘ricin’, which is fatal even in very small amounts. Lectins in raw kidney beans are a well-known hazard, so the beans must be soaked and well-cooked to make them safer. Peanuts are deadly to those with an allergy, and that reaction is caused by peanut lectin. Soy allergy is also due to lectin.
Your favorite veggies
Nightshades are a plant family which includes tomatoes, bell peppers, potatoes and eggplant. For most of history, it was well-known that nightshades should not be eaten, hence the name “deadly nightshade”. These plants contain the chemical ‘solanine’ (and ‘tomatine’ in tomatoes), which is found in varying concentrations in all nightshades and functions as an insecticide. These chemicals make it dangerous to eat raw or green potatoes, or the leaves of any nightshades. While most people can tolerate small amounts of solanine and tomatine in their diets, those with sensitivities find they must avoid exposure entirely.
Leafy greens such as spinach, rhubarb, kale, beets, and Swiss chard are common in the diet, but they contain a compound called oxalate, which is found bound to minerals, such as calcium, forming the compound calcium oxalate. This is what is referred to when spinach is described as ‘high in calcium’. However, this form of calcium has low bio-availability compared to dairy (5% calcium absorbed from spinach vs 32% from dairy). Oxalate also binds to calcium, preventing absorption, which is helpful if you want to consume high- oxalate foods. Calcium oxalate crystals can also cause fibromyalgia, vulvodynia, arthritis, intestinal damage, heart failure, and form kidney stones. It is common for those who begin eating large volumes of spinach as part of a misguided “health kick” to develop these painful stones quickly.
Fruits are safer but not without concern. Although fruit is a more suitable food from an evolutionary perspective, they should still be consumed with care and moderation, as they also contain varying levels of tannins, oxalates, salicylates and thaumatin-like proteins. For example, drinking fruit juice causes a sudden, large intake of fructose that will trigger an insulin spike, just like drinking a soda. Fruits may also cause allergies in different individuals, so approach each fruit with curiosity, and watch to see if any symptoms appear after consumption.
Want to know more about specific plant toxins and their effects on human biology? Click here!
Should you avoid eating plants completely?
You may now be wondering whether you should avoid eating plants completely. While this is a question that you must answer for yourself, what is certain is that humans have thrived on diets of nearly 100% animal fat and protein for millennia, with the Inuit being one of the most famous, due to their ability to survive in a frozen landscape. In contrast, there has never been a vegan population of humans until the last few decades, except for prehistoric P. Robustus, that split from our common ancestor. P. Robustus had a diet of nuts, seeds, and hard fruit, and became extinct when they hit an evolutionary dead end because their diet was too specialized to adapt to new food sources in Africa’s changing climate.
Eliminate to activate
If you are currently suffering with severe health problems, then you can consider an ‘elimination diet’. There are many protocols that have been developed for this purpose, but the concept is simple enough for you to implement your own. There are two approaches:
- Eliminate specific allergens one by one, or by group.
- Start with one safe food, and add back one by one.
The proponents of each will suggest that if you are very sick, then you should try their method. Option 1 is considered preferable by advocates because they believe that your body may be overwhelmed by withdrawals, or toxin dumping (such as oxalates and heavy metals stored in tissues). Option 2 is considered preferable by advocates because they believe that your body is sick due to being overwhelmed with the vast array of allergens, and that the body will be given the best chance of healing if it is only exposed to a minimal amount of foods. This option commonly uses chicken broth or beef as a starting food, although raw milk has many health benefits, and been used with success, even as a cure for many conditions in the early 1900s.
You will need to listen to your body to decide what is right for you. I have tried both elimination approaches, and I found that option 1 was confusing to figure out, due to the other allergens continuing to cause symptoms. I found option 2 was also challenging because my body had to experience withdrawal symptoms from everything that I was no longer consuming. However, once I stabilized, it was much easier to tell what foods caused a problem for me with option 2.
After trying an elimination diet, you may find that you can eat lots of plants without any effects, or you may find that you cannot consume any plants, as many people in the carnivore community have found. What works for you will be as unique as your genetic makeup.
You now get to begin an exciting journey of discovery, where you will learn about your body and your mind. You will discover how profoundly diet affects all aspects of your life and well-being, and emerge more aware, informed, and healthier. I wish you good luck and the best of health.