Do Plant Toxins Make Vegan Diets Risky?

It is common knowledge that fruits and vegetables must be included in our diet, to receive all the nutrients, our bodies need. But eating plants isn’t without a risk, they contain toxins, that can damage our health. Those, who adopt plant based / vegan diets are more at risk, since they consume plants in large quantities.

Liam Hemsworth, the Australian actor had to be rushed to the hospital for emergency kidney stone surgery in 2019, at the age of 28, after being on a vegan diet for 4 years.

Here are some of the most common Plant Toxins:


Lectins are naturally occurring proteins, that bind to carbohydrates, they are found in most plants. Foods that contain higher amounts of lectins include beans, peanuts, lentils, tomatoes, potatoes, eggplants and wheat.

Red kidney beans contain the highest amount, the FDA warns that eating as few as 4 raw, or undercooked kidney beans are enough to cause severe illness. The main symptoms of kidney bean poisoning are abdominal pain, vomiting and diarrhea. Mild reaction to lectins causes stomach pain and bloating.

Lectins are one of the “anti-nutrients”, they interfere with the absorption of minerals, especially calcium, iron, phosphorus and zinc.

Lectin is water soluble and is mainly located on the outer surface of vegetables. For this reason, contact with water, soaking beans overnight and cooking them on high heat inactivates them.

Phytic Acid

Phytic acid, or phytate is a unique natural substance, found in plant seeds. The function of phytic acid is to store phosphorus in the seed. When the seed sprouts, the phytate is broken down, the phosphorus is released and used by the young plant.

It is another anti-nutrient, that can cause mineral deficiencies, particularly for those on plant based diets. Plant-derived iron and zinc are poorly absorbed and highly affected by phytic acid, unlike those, from animal derived products.

Phytic acid is found in seeds, nuts, legumes and grains. Soaking, sprouting and fermentation reduces phytates content substantially.


Oxalates, or oxalic acid is a naturally occurring compound. Most plants contain oxalates, so it’s impossible to completely avoid them. Because oxalates bind to calcium as they leave the body, they contribute to the development of kidney stones. (as in the case of Hemworth) It is estimated that 8 out of 10 kidney stones consist of oxalates.

Since it binds to minerals, it can also cause mineral deficiencies. Most people take in 200-300 mg of oxalates per day. Low oxalate diets contain only 40-50 mg and a half cup of spinach has 755 milligrams!

Leafy greens, vegetables, fruits, cocoa, nuts and seeds are the highest oxalate sources.


Solanine is a glycoalkaloid, defined, as a neurotoxin enzyme inhibitor. In high quantities it can lead to convulsions and paralysis, in minor cases it causes malabsorption and diarrhea. Vegetables in the “nightshade” family of plants – potatoes, eggplant, tomatoes, peppers – are high in solanine / glycoalkaloids.

The FDA regulates how much can be present in potatoes, sold for consumption. Green potatoes (resulting from being exposed to sunlight) and sprouting stems are the highest in glycoalkaloids.


Sulforaphanes are found in cruciferous vegetables, kale, broccoli, brussel sprouts, cauliflower and others. When consumed in excess amounts, it can cause constipation, diarrhea. In addition, isothiocyanates, present in cruciferous vegetables, can contribute to iodine loss and hypothyroidism.

The awareness of the potential harm, these and other plant toxins can cause, may lead to a decision to eliminate them from one’s diet. But these fruits and vegetables are also some of the most nutrient dense foods available, providing high amounts of vitamins, proteins, minerals, fibers and healthy fats, giving them up completely isn’t a good idea.

The solution is: When we avoid excess, we can benefit from the nutrition these plant foods offer, without causing harm.

In an interview with Men’s Health in 2019, Liam Hemsworth said that his kidney stones were due to the huge amounts of of vegetables he consumed, as part of his vegan diet.

“Every morning, I was having five handfuls of spinach and then almond milk, almond butter, and also some vegan protein in a smoothie”

Spinach and almonds have the highest oxalate content. Five handfull of spinach is about 2.5 cups = 1888 mg of oxalic acid, that is 9 times what most people take in daily. And this was only a part of one of his meals.

(there are several factors involved in the development of kidney stones, they are actually more common among meat eaters, even though plants have the highest concentration of oxalates)

I’ll add a personal experience, I once heard a nutrition expert say that, the more green leafy vegetables people eat, the longer they live. That made sense to me, after all leafy greens are nutritional powerhouses. I started eating a large bowl of salad daily.

But my stomach wasn’t feeling good. Too many bathroom visits and loose stool indicated bowel contamination and inflammation. My body was probably reacting to excess toxins. Listening to our bodies is one of the ways we can tell how much is too much.

The plant toxins I listed, are also antioxidants, when consumed in moderate amounts, they protect our cells from free radicals. These substances can keep us young, or kill us, depending on the dose.

The scientific terms for this phenomenon is Hormesis. It is defined as: “a biphasic dose response to an environmental agent characterized by a low dose stimulation or beneficial effect and a high dose inhibitory or toxic effect.”

Exposure to a low dose chemical agent (a toxin), induces a beneficial adoptive response. The same biological process takes place, when we exercise, the body responds to it, by becoming stronger.

Related: Vegan Myths and Misconceptions | Raw vs. Cooked Vegan Diets – Which is Better?

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