TL;DR: The only evidence that plants are good for us are correlation studies confounded by the healthy user bias. Plants have several classes of compounds that cause inflammation and disease flavonoids, oxalates, lectins, isothiocyanates, salicylates, and tannins. Humans aren’t truly designed to eat a large amount of plants like herbivores are.
This article is part of our 6 part series on the carnivore diet. For previous sections, see the links below:
- An Intro to the Carnivore Diet
- Were Hunter-Gatherers Healthier Than Us?
- Do Plant-Based Foods Have a Dark Side?
- Are Animal Foods More Nutritious Than Plant Foods?
- Is Red Meat Actually Bad For You?
- What to Eat on a Carnivore Diet
Correlation vs. Causation
A big problem with science these days is that many studies are only able to show correlation, not causation, and then this correlation is taken as a fact rather than a guide to explore more.
This is the case in population studies, where a group of people fill out surveys and correlations are found between their behaviours and their outcomes. Saladino points out that the only studies that show benefits of fruits and vegetables are these and other types of correlation studies, which finds there is a correlation between eating plant foods and being healthy. Since almost everyone thinks eating fruits and vegetables is healthy, almost all healthy people do it, which strongly biases these studies. This is referred to as the healthy user bias. Interestingly, the book The Big Fat Surprise based on a 9 year research project, explains how only after the 1950s were meat and animal fat viewed as unhealthy. Before this, they were seen to make you strong and healthy. Many correlation studies also don’t show this correlation, so that puts the findings into question and more research should be done into the causation patterns happening.
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Interventional studies on the other hand show causation. In these studies, a group of people are split into two groups, and one is exposed to a new factor like a change in their diet and they are both monitored after this change to see the outcomes. One of the most common and rigorous of these types of studies is the Randomized Controlled Trial (RCT) where the participants are randomly assigned to each group. Double blind RCTs take it a step further and make sure not even the researchers know who is assigned to which group. Interventional studies like the RCT show causation.
Furthermore, if it were true that fruits and vegetables were healthy, we would be able to see it in controlled studies like interventional studies, but these have repeatedly shown no benefit as we will see later on.
Another interesting point is that correlation, or population, studies in the East show that red meat, poultry, and seafood is actually associated with less death from cardiovascular disease in men and less death from cancer in women, and high consumption of animal fat and cholesterol is associated with reduced risk of cerebral infarction (arteries clogged in the brain) death [6 Ch.4]. Other studies in the East show similar effects [7 Ch.4]. This is explored more later on as well.
How Free Radicals Work
Our body basically runs on electricity like computers do, but are vastly more complicated. We eat food to harness the energy inside of the bonds in the molecules. When we break these bonds, energy is released and we harvest it and transport it in the form of electrons to store in molecules like ATP. When electrons are taken from one molecule, it is called oxidation, and when it is given to another molecule to store this energy, it is called reduction. Balancing this perpetual reduction-oxidation (redox) reaction in our bodies is essential to the basic functioning of a living thing. Too much of one or the other creates imbalance at a fundamental level.
Fire is caused by the heat generated when wood is oxidized and the energy in the bonds is released which is why it needs so much oxygen – a strong oxidizer. Similarly, in cellular respiration, food we eat is broken apart, or burned, or oxidized also with oxygen but in a more controlled manner so the energy can be used. We need to burn fuel to live, but it also generates free radicals that our body needs to clean up with antioxidants after. Interestingly, a fat based metabolism creates much less free radicals than a carbohydrate based metabolism, so there is less work for our bodies to do after. Fats appear to burn more cleanly as the fuel in our bodies. This is only the beginning of the benefits of a fat based metabolism as we will see later.
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Free radicals, which we hear of as “bad” things in our bodies that cause damage and aging are molecules with an unpaired electron and are highly reactive (also called Reactive Oxygen Species). They are highly reactive because they are only missing one electron, so they have a strong affinity to getting this last one anywhere they can. They are highly oxidizing molecules and may shift the balance too much towards oxidation rather than reduction in our bodies. These are actually essential for cell signalling in our bodies, but when we have too many, they start to steal electrons from important structures like proteins, lipids, and nucleic acids causing cellular damage and aging. Interestingly, carbohydrate metabolisms release
Antioxidants are important because when this happens, they can be released by our bodies to neutralize the extra free radicals, hence the name anti-oxidants, the free radicals being the oxidants. If too many are neutralized, however, our cells can’t talk to each other properly so our body is careful not to over do it one way or another. This is actually why we don’t want too many antioxidants in our blood since it will skew the balance too far the other way in favour of reduction. Balance is the key here.
Saladino explains that our bodies carefully regulate this balance with our human made antioxidants and the best way to support this naturally is to consume nutrients like zinc, copper, selenium, and magnesium as well as the amino acid glycine (found in collagen) which we use to make a central antioxidant in our bodies called glutathione. The best sources of these nutrients that strengthen our immune system and control free radicals are animal foods, whereas plant foods are very poor sources relatively. The antioxidants in plants are from a completely different system and when we eat them, our body simply disposes of them and does not use them. In fact, they often cause damage by creating free radicals.
Different Operating Systems – Plants vs. Animals
Plants and animals operate on very different biochemical systems, and bringing in molecules like antioxidants from plants into our animal system doesn’t benefit it. It’s just a wrench in the system. This is a theme throughout the book. Another example is that plant nutrients like iron and vitamin A are in forms in plants that are much less bioavailable. Plant forms of nutrients are much harder to incorporate into our animal bodies. This is why herbivores like cows have four stomachs, they use large amounts of bacteria to ferment the plant foods down into usable nutrients.
Herbivore digestion example [i]
Carnivore digestion example [j]
Antioxidants
Molecules like antioxidants from plants are eliminated from the body usually quite quickly, and are not used for anything – an effect of being from different operating systems. Contrary to popular belief, plant antioxidants are actually pro-oxidants in that they create free radicals that our body has to clean up. Our body responds to this by activating a pathway called the NRF2 pathway, which turns on genes to release human antioxidants like glutathione to neutralize the free radicals. When our blood is analysed after, we may have higher amounts of antioxidants because our body released them to neutralize the free radicals created by the plant antioxidants! However, over the long term this appears to tax our system. It seems better to not tax our NRF2 pathway in the first place and save our antioxidants. Furthermore, we don’t even want too many antioxidants in our body in the first place because they will neutralize too many free radicals and then our cells can’t communicate properly – an imbalance in the redox reaction.
Hormesis: A Little of A Bad Thing Is a Good Thing
We all know that too much stress is bad for us, but what about too little? There is a concept xenohormesis, like with exercise where too much wears us out and too little makes us weak. Sometimes an argument is brought up that some amount of plant antioxidants are good for us because it stresses our bodies a little bit.
When you look at interventional studies comparing those who eat a lot of vegetables and fruits (up to 10 servings) vs. those with much less or no plant foods, there are no benefits found after several weeks [37,38,39 Ch.4]. Then, when we look directly at studies where people are given antioxidant supplements, their antioxidant status does not improve and often their outcomes are worse [5,6,7,8,9,10 Ch.3].
Interestingly, the NRF2 pathway is also activated by other pro-oxidants like smoking, heavy metals, high blood sugar, arsenic, alcohol, and other oxidative stress involving excessive free radicals. We would never say that more of these is a good thing.
Berlin Ice “Swimmers” [k]
There are also ways of activating the NRF2 pathway that don’t have side effects, and this would actually be categorized as xenohormesis. Environmental hexohormetics include cold water exposure, exercise, saunas or heat, and sunlight. Too much of any of these is bad, but some amount is good. For example, one study found that in Berlin winter swimmers, an hour in cold water reduced glutathione levels immediately after, but the next day their levels were higher than baseline [43 Ch.4].
Plant Defense Compounds
Now that we’ve reviewed some background, let’s get into what are called plant defense compounds.
From the outset here, it should be clarified that Saladino believes plant foods should be absolutely used for medicinal purposes when appropriate, just not as regular foods in the diet for optimal health. He also notes that a diet that is mostly carnivore is a big improvement over a diet with little or no meat in it.
Plants can’t run, hide, or fight, so they have evolved compounds that damage any predators who might eat them. These compounds are called plant defense compounds by Saladino. Often, these are the exact compounds that you hear are healthy, but Saladino says the studies and the mechanisms behind these compounds tell a different story which we’ve seen in the example of antioxidants above already.
Herbivores have ways of deactivating these compounds, for instance, moose have proteins in their saliva that deactivate a defense compound called tannins in leaves. Tannins disrupt digestive enzymes. Rabbits chew sage for a long time until all of the volatile plant toxins are evaporated. Herbivores also rotate which types of plants they eat so they don’t consume too much of one toxin. Mass deaths even occur if they are forced to eat only one type of plant. Carnivores, and humans lack these deactivating mechanisms and we have to cook, soak, dry, grind or prepare them in another way to deactivate them. This is why, for example, we soak beans and cook grains before eating them usually.
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Saladino references Bruce Ames’ research where he estimates that when we worry about pesticides added to our foods, we should also worry about plant defense compounds, which he calls natural pesticides. In fact, 99.9% of the pesticides we consume are from plants, and only 0.1% is from synthetic pesticides. He identified 42 natural pesticides in regular foods like cabbage, and many of these have been shown to damage DNA in humans and animals. Many are even identified as rodent carcinogens. Of course, synthetic pesticides are worse in some ways, which isn’t mentioned in the book.
There is still much to learn about plant defense compounds, but here is a list of some with the harms they pose.
Flavonoids
One group of plant antioxidants include a group of compounds called flavonoids found in the following:
- Berries (Anthocyanins, a pigment in the skin of berries)
- Soy (contains Isoflavones, and Genistein)
- Tea (contains Catechins)
- Cocoa (Contains Flavanols)
- Onions (Contains Quercetin)
Flavonoids mimics the action of estrogen by activating a receptor called the 17B estradiol receptor [18,19 Ch.5], and disrupts our hormone balance [20,21,22,23 Ch.5]. They also significantly decrease protein utilization from food [34,35 Ch.5]. Isoflavones in soy are well-known endocrine disruptors, perhaps famous for the term “soy boy”. In men, they increase infertility and worsen sperm quality [24 Ch.3]. Soy and its flavonoids are also known to worsen response to pathogens.
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A compound called genistein, also found in soy, as well as catechins in tea decrease enzymes needed to make thyroid hormones [26 Ch.5], and inadequate thyroid hormones cause fatigue, depression, weight gain, cold intolerance, brain fog and generally stop our body from getting into high gear. We often hear of antioxidants like catechins in green tea being healthy for us because they help clean up free radicals, but the idea Saladino presents, discussed a few paragraphs back, is that consuming plant antioxidants does not actually help us create human antioxidants since they are a part of a completely different system. Catechins in green tea have been shown to interfere with proper thyroid function [19,20 Ch.4]
Curcumin is well known to be high in antioxidants, however it only shows benefits at very high doses in studies, and at these doses they are known to cause DNA damage and chromosomal alterations in vitro and in vivo (in cell cultures, and in the living body). Although it is counter-intuitive, it creates a lot of reactive oxygen species (free radicals) that our body has to clean up after with our own antioxidants.
Besides, taking things like curcumin and other antioxidants to quell inflammation is like waiting for a house to catch on fire, then pouring water on it rather than preventing the fire in the first place. An ounce of prevention is worth a pound of cure. The root cause of the inflammation needs to be addressed, or the problem won’t go away. This includes stress, sleep, environmental toxins, but above all, food. When we eat the wrong foods, our immune system becomes overactive and also creates free radicals and stresses our body constantly and unnecessarily. As Hippocrates suggested, “all disease begins in the gut”.
Oxalates
Another group of plant defense compounds are called oxalates, which are organic acids made in plants and some is made in animals. In plants, oxalates are used to bind to minerals like calcium, magnesium, and zinc to control their concentration in cells, and also as a chemical defense mechanism against predators.
Oxalates are produced in small quantities (10 – 30 mg/day) as a waste product in human metabolism, and are excreted in urine, an immediate sign that our body does not want them to build up in our bodies. They occur in very large amounts in some plants like spinach. A green smoothie may have 200x (2,000 mg – 6,000 mg) what we produce in a day and deaths have even been reported with 5,000 mg of oxalates [4,5,6,7 Ch.6].
Green smoothies have a lot of oxalates [n]
Oxalates can actually be quite dangerous sometimes. There was one case of a 65 year old woman who had acute oxalate nephropathy resulting in permanent kidney damage requiring ongoing dialysis. She consumed an average of 1,300mg/day [8 Ch.6]. There have also been similar reports from peanuts, star fruit, almonds, rhubarb, iced tea, and chaga mushroom [12 Ch.6] and oxalate deaths have been reported for over 100 years in scientific literature.
In most people nowadays, oxalates are depositing in tissues, often in the kidneys forming kidney stones which are very painful, but also depositing in other places in microscopic amounts like the thymus, kidney, blood vessels, testicles, brain, eyes, thyroid, and breasts [14 Ch. 6]. According to one autopsy survey, 79% of the 103 thyroids examined had oxalate crystals.
There is actually a rare condition called hyperoxaluria where the body forms 100 – 600 mg of oxalates per day instead of the normal 10 – 30 mg and this causes frequent and severe calcium oxalate kidney stones often leading to permanent kidney damage or renal failure. Those with this condition also often develop an underactive thyroid – hypothyroidism. The thyroid is responsible for regulating energy levels, growth, and metabolism in the body. A study from 2011 also found that children with autism show 3x greater blood oxalate levels on average, and 2.5x the normal levels in urine. Oxalate crystals in breast tissue are also associated with precancerous lesions (LCIS) [17 Ch.6] and unhealthy breast tissue consistently shows higher oxalate levels. When oxalates are injected into mice breast fat pads, they induce the formation of tumors [18 Ch.6].
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Consuming chocolate or turmeric, high in oxalates, increases urinary oxalate levels similar to primary hyperoxaluria [21 Ch.6]. 50g of chocolate causes a 235% increase in urine oxalate levels, and 100g causes 289% increase. So, this indicates that eating enough foods with oxalates in them replicates having hyperoxaluria at least to some degree, which often causes permanent kidney damage.
The good piece of news is that tissues appear to remove oxalates over time.
Lectins
Lectins are proteins that bind to the surface of or within cells. They actually occur in all kingdoms of life, but are different in plants vs. animals. The lectins in plants appear much more likely to stimulate our immune system and cause damage to our gut. They are found in foods like seeds, grains, nuts, legumes, nightshade vegetables, the skin and seeds of squashes, and traditional dairy products [30 Ch.7], as well as the most famous lectin of all: gluten. One part of gluten called gliadin causes release of zonulin, cytoskeleton damage, DNA/RNA damage, increased oxidative stress, and these last two often cause programmed cell death – aka apoptosis [18 Ch.7]. Check out our article on how gluten free diets benefit you for more.
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Lectins do some other worrying things. For starters, soybeans, lentils, wheat germ, and kidney beans have many lectins that bind to white blood cells and release cytokines – immune system signallers [22 Ch.7]. One extreme example is that 5-20 castor beans have enough of a very strong lectin called risin to kill a person by stopping their ribosomes from working. It binds to a carbohydrate portion of the ribosome stopping it from protein formation [3 Ch.7]. You may have heard never to eat uncooked kidney beans. This is because they have a lectin called PHA which causes food poisoning, impairs growth and even reduces muscle mass by binding to gut cells causing them to reduce mucus production allowing certain bacteria to overproliferate [6 Ch.6].
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When the mucus membrane in our gut is reduced from lectins, bacteria can then also get through the mucus membrane and reach our gut cells directly, which sounds our immune system alarms and releases a molecule called zonulin [12 Ch.7], which is highly correlated with autoimmune diseases [13 Ch.7]. Autoimmune diseases are a root cause of many major diseases today including Type I diabetes. Zonulin is a molecule that opens the tight junctions between cells in the gut and is strongly correlated with a condition called leaky gut, where holes open up between cells in our gut and allow pathogens to enter our bloodstream triggering chronic inflammation and autoimmunity. In the book The Plant Paradox, one study is referenced where 80/102 patients were weaned off of their autoimmune medications simply by limiting lectins [29 Ch.7]. In general, lectins appear to damage microbial diversity [7,8 Ch.7] by increasing growth of bad microbes like E. Coli. Even in those without autoimmune problems, having a gut that allows pathogens through which irritates our immune system frequently is not good for us. Gluten in all people cases leaky gut at least temporarily.
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Now for something that sounds like science fiction: lectins can travel up a nerve called the vagus nerve, one of the main nerves in the body, and they tend to cluster around dopamine secreting neurons and this has even been suggested as a possible cause of Parkinsons’ disease [24 Ch.7]. Lectins from peas administered to rats caused symptoms of Parkinson’s.
At the end of the day, each person’s genetics determines if and how symptoms present due to inflammation from plant defense compounds like lectins. Some may notice no symptoms, others may develop arthritis, or heart disease, or type I diabetes, or lupus, or Parkinson’s over long periods of time, or quickly depending on the individual. Wherever the weak link is in the body that can’t take the inflammatory stress will buckle first. Those with strong constitutions may not show symptoms, but there can be damage accumulating behind the scenes accelerating the aging process.
Lectins also play a role in weight gain, for example, a wheat lectin that protects it from insects called wheat germ agglutinin can bind to the insulin receptor, stimulate growth of fat cells, and inhibit lipolysis (burning stored fat) [27 Ch.7]. Plant lectins in general seem to act similarly to insulin. Lectins negatively affect the signalling of leptin, a hormone we release to make us feel full, making people feel less full than they should be [28 Ch.7]
The good news is that lectins can be denatured by high temperatures and pressures, but to what degree isn’t covered in this book.
Isothiocyanates
These compounds interfere with proper thyroid function and damage DNA and are found in many plant foods.
One example is sulforaphane, found in broccoli and other vegetables, which is often touted as a cancer fighter or antioxidant hero, however when we eat it our bodies immediately detoxify it, which is a sign our bodies don’t want it. Sulforaphane is formed when a plant’s cell wall is destroyed allowing two chemicals to mix in an attempt to defend against predators. It is toxic to living broccoli and humans. What isn’t detoxified by our bodies then competes with iodine in our blood for absorption in the thyroid. Eating these vegetables combined with low iodine consumption can lead to an underactive thyroid (hypothyroidism) as well as goiters.
Isothiocyanates also interfere with proper thyroid functionality and damage DNA by inducing chromosomal breaks [1,2,3,4,5 Ch.4]. Feeding broccoli to mice and rats caused DNA damage in some studies, and in others showed the same effects in pigs and flies [7,8,9,10,11 Ch.4]. There are no studies of this on humans, but over-eating foods like broccoli induces under-active thyroid glands and goiters, especially in underdeveloped regions of the world [14,15,16,17 Ch.4]
Resveratrol
You may have heard this is a longevity molecule found in wine. It was originally purported to be beneficial because it shows in fruit flies, worms, and mice that it increases longevity and shows improvement in diabetes. It does this by activating genes called sirtuins. However, in human trials, there don’t appear to be any benefits [41 Ch.5], and it may worsen blood sugar control [40 Ch.5] and lower testosterone precursors [42 Ch.5]. It also activates the NRF2 pathway discussed earlier, and shows the ability to oxidize membrane lipids and damage DNA [43,44 Ch.5].
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Interestingly, ketosis activates the same sirtuin genes that cause the benefits of resveratrol indicating there are healthier ways to activate these longevity genes.
Salicylates
Salicylates are similar to polyphenols, found in asparagus, almonds, avocados, cherries, nectarines, dates, blackberries, coconuts and coconut oil, honey, tomatoes, potatoes, and eggplants. Symptoms of too much include headaches, asthma, rashes and ringing in the ears
Tannins
Tannins are another group of plant defense compounds under the category of polyphenols and are big digestion disruptors, inhibiting a number of digestive enzymes including trypsin, alpha-amylase, and lipase [32,33 Ch.5]. Many herbivores have compounds in their saliva that bind to tannins so they don’t deactivate their enzymes.
Takeaway
In all of these compounds there appears to be harm when they build up in our bodies, which is why our bodies try to get rid of them. If you notice any issues with your immune system or digestion including frequent sickness, joint pain, unusual tiredness, or frequent bad mood, try cutting out some plant foods mentioned above, and rotate the ones you eat so certain toxins don’t build up. It doesn’t appear necessary to cut out plants entirely, but moderating their consumption seems prudent. It might be worth it to have that glass, or bottle, of wine every once in a while, but don’t be downing green smoothies every morning.
