At one point in my life, I naively thought some beliefs were so obviously false that we’d never have to seriously respond to them. Fast forward 15 years and we find ourselves with a US Secretary of Health that thinks the measles vaccine routinely kills people, and a president that thinks you can replace income taxes with tariffs. It was probably a lot easier to keep insane ideas at bay before the internet, because back then if you wanted to share them, you had to grab a megaphone and yell at people going into Costa. Nowadays, with a little persistence, the algorithm will start to present your batshit thoughts to other batshit people, who in turn share it to all their batshit friends and family. Before long you’re rolling an enormous batshit snowball that’s picking up all the only-kind-of-batshit people along the way, and heading straight towards the rest of us. Now we can’t ignore it anymore because it’s crashed into the city centre, and some of the shit went into our kids’ eyes. That’s how we find ourselves gently explaining to a grown man that CO2 is not good for the environment because a YouTube video told him “it’s plant food” (a real conversation I’ve had).
One such idea is this sticky claim that vegetables aren’t good for you, which is the sort of fad that can only come about if the Illuminati was overthrown by a boardroom of shadowy five-year-olds (The next big thing will probably be that cooties are real, and bedtimes cause cancer). You usually see this claim made by the carnivore crowd, for example Paul Saladino, or Shawn Baker.
So what’s their problem with veggies? Well the general idea is that vegetables contain defence chemicals that aim to hurt the animals that eat them. This is allegedly an adaptation that protects plants from us (interestingly, Saladino cites seeds as a danger, even though them being eaten is adaptive for plants because they get spread by animal waste). Essentially these chemicals play the same role in spinach as claws play on a bear, or my innate Wu-Tang style plays in me.
Now, as to whether or not this story is actually true isn’t super important. I’m a little skeptical, but let’s just accept it for sake of argument. The real question is, are these plants actually harming us, or is this a story being told to make ordinary people buy goat testicle supplements?
Lectins
Lectins are a family of carbohydrate-binding proteins that’re found in many plants, particularly legumes such as beans, lentils, and whole grains. The worry is that lectins bind to the lining of your gut and damage it, which is why many health influencers claim that eating a diet high in lectins can give you “leaky gut”, a truly awful pairing of words I’d hoped to never read. There’s also a concern that it acts as an “anti-nutrient” that blocks the absorption of other important stuff your body needs.
This worry isn’t baseless. If you eat a bunch of raw beans you probably will shit your pants. However, we have a secret weapon at our disposal: cooking our beans. Revolutionary, I know! You can even remove lectins by soaking your beans, because they’re water soluble. Fortunately, just about every non-sociopath in the world has a good habit of cooking their legumes instead of scooping them out of the can like they’re skittles, so the fear that these foods will tear you up on the inside isn’t well backed up.
This is why “there is currently no strong evidence from human trials to support the claim that lectin-rich foods consistently cause inflammation, intestinal permeability, or nutrient absorption issues”. In fact, that meta analysis found that legumes and whole grains are associated with a decreased risk in inflammation.
This has been a recurring theme in the nutritional content I’ve written, and will continue to be one in this article - mechanistic data is not enough to go of off. The worry about lectins shares the same feature the worry around seed oils has. People see some mechanism that sounds bad, assume it obtains in the real world, and make their decisions based on that assumption. This is always going to fall short of looking at health outcomes, which shows you what actually happens when some food is eaten. Relying on mechanistic data is like trying to determine how fast a car goes based on its weight alone. You’d probably do better if you just drove it and watched the speedometer.
Extra Evidence on Legumes
“Higher intakes of legumes, compared with lower intakes, were associated with a reduced risk of mortality from all causes”.
Legume consumption and CVD risk: a systematic review and meta-analysis
“Compared with lower legume consumption, the highest category of exposure was associated with a decreased risk of 10 % in both Cardiovascular Disease and Coronary Heart Disease (relative risk=0·90; 95 % CI 0·84, 0·97) with no or little evidence of heterogeneity and no publication bias.”
Phytates
Phytates, such as Phytic Acid, are found in legumes, nuts, seeds, and whole wheat. It’s also cited as an “anti-nutrient” because it can bind to important minerals like iron, zinc, calcium, and magnesium, and prevent their absorption. This is a problem for me, because as a vegan, legumes, nuts, seeds, and whole wheat are precisely what I use to make my birthday cake every year (the icing is made from blended kale). If you eat a lot of these foods, the worry is that you’ll become anemic and your bones will crumble to dust.
“Yeah I’ve been eating a lot of lentils lately. Please don’t touch me, it hurts.”
So what does the data say? Well, what we have is limited. It has been found in isolated conditions that meals high in phytate can reduce mineral absorption. I stress ‘isolated conditions’ there, because in the real world the relationship isn’t so easily spotted. Most studies on vegetarians, who typically eat phytate rich diets, find they don’t have lower levels of iron. You may have seen some research observe an increased risk of iron deficiency in vegans/vegetarians, but it’s important to check if they’ve adjusted for obesity. When we do so, we see the relationship disappear.
“However, after the exclusion of individuals with inflammation (with overweight/obesity and elevated hs-CRP levels), the actual iron deficiency was assessed and was not higher among vegetarians, except in women with regular menstrual cycles.”
We see a similar relationship with other minerals. While it’s true that plant-rich diets tend to leave us with less zinc and selenium, it’s not as if they leave us totally devoid of them.
“Despite the apparent lower bioavailability of zinc, copper, manganese, and selenium in vegetarian diets because of the high contents of phytic acid and/or dietary fiber and the low content of flesh foods in the diet, the trace element status of most adult vegetarians appears to be adequate.”
As usual, we need to evaluate the health benefits of a food beyond it’s effect on a single mechanism. You can probably find a single negative health impact of any food, but many of them will have benefits that outweigh the harm. Phytates, for example, are anti-oxidant and bind to heme-iron, meaning they can protect you against cardiovascular disease. There’s also some preliminary evidence that they protect against cancer.
Extra Evidence on Phytates
“Phytates should not significantly impair mineral status when included as part of a diverse and balanced diet, especially if using traditional processing methods such as soaking, germinating, fermenting, and cooking.”
“Overall, by consuming a colorful, plant-based diet, the benefits of phytate containing foods to human health exceed the impacts on mineral absorption.”
“the effect of dietary phytate on zinc absorption when controlling for dietary zinc was very small and not statistically discernable”.
“Phytase treatment led to >90% reduction in IP6 and to an IP6:Fe molar ratio <1, but iron bioaccessibility was not improved”
Oxalates
Oxalates are organic acids found in foods like spinach, beets, some nuts, and legumes (legumes again? What don’t they have in them?!). Similar to Phytates, they bind to minerals, especially calcium, and prevent their absorption. That should be the last of your worries though, as calcium oxalate can also accrue in your kidney and form kidney stones. I’m told this isn’t fun, and will eventually feel like pissing out a Malteser if it had a bunch of jagged edges (here I was thinking we couldn’t get more horrifying than “leaky gut”, but I suppose there’s always a bigger fish).
The worry that oxalates cause kidney stones is not unreasonable. It is true there’s a relationship between higher oxalate intake and the development of kidney stones, however it’s nuanced. Whether or not a high oxalate diet will give you kidney stones seems to be massively influenced by how much calcium you eat.
“Participants in the highest quintile as compared to the lowest quintile of dietary oxalate, experienced a relative risk of 1.22 for men and 1.21 for older women. Even more significant, in men with lower calcium intake (<755 mg/day), the risk in the highest quintile of dietary oxalate jumped to 1.46. Conversely, in men with calcium intake at or above the median, the multivariate risk dropped to 0.83.”
Weirdly, you’d think a higher calcium intake is associated with a higher incidence of kidney stones, because there’s more opportunity for the oxalate to bind, however the opposite is true. This is because if you eat calcium and oxalates together, they bind in the gut, preventing them from entering the bloodstream. However, if the oxalate doesn’t bind and makes it to the bloodstream on it’s own, it could bind there and then end up in the kidney. Again, this is why it’s important to look at health outcomes instead of extrapolating from one mechanism.
“Overall, authors concluded that dietary oxalate is not a major risk factor for stone formation [66]. In a more recent NHS I and NHS II analysis, authors again concluded that dietary oxalate had little impact on kidney stone formation, while dietary calcium intake was inversely associated with kidney stone formation [67].”
So, it seems like oxalate on it’s own is not a risk factor so long as you eat enough calcium (and drink enough water, that’s handy too). Interestingly, there are other components of plant foods that decrease the risk of kidney stones, including our old friends phytates.
“Additionally, dietary potassium, magnesium, and phytate all decrease kidney stone formation through an array of mechanisms [68]. Despite significantly more dietary oxalates (254 mg/day) and oxalate-containing foods such as nuts, vegetables, and whole grains, participants with higher DASH scores have a 40–50% decreased risk of kidney stones [68].”
Extra Evidence on Oxalates
Dietary and lifestyle factors for primary prevention of nephrolithiasis: a systematic review and meta-analysis (Note: “nephrolithiasis” means kidney stones)
“Prominent risk factors for incident stones were body mass index (1.39,1.27–1.52), dietary sodium (1.38, 1.21–1.56), fructose, meat, animal protein, and soda. In contrast, protective factors included fluid intake (0.55, 0.51–0.60), a Dietary Approaches to Stop Hypertension (DASH) style diet (0.69, 0.64–0.75), alcohol (0.69, 0.56–0.85), water, coffee, tea, vegetables, fruits, dietary fiber, dietary calcium (0.83, 0.76–0.90), and potassium.”
Glucosinolates
Besides being named a word I can’t pronounce, Glucosinolates are sulfur containing compounds found in cruciferous vegetables such as broccoli, cabbage, and kale. The concern surrounding them is primarily that they can act as goitrogens - substances that interfere with iodine uptake in the thyroid gland. Essentially, the worry is if you eat a lot of cruciferous vegetables, you may get hypothyroidism or goiter. A fact I really could’ve used to stop my nan from giving me brussels sprouts at Christmas.
Fortunately, what evidence we have on dietary goitrogens and their effects on thyroid function are promising. This 3 year randomised control trial found no deleterious effect of goitrogen consumption on thyroid function for post menopausal women.
“These data suggest that genistein aglycone intake does not significantly increase the risk of clinical or subclinical hypothyroidism at the dose of 54 mg/d.”
A review on the impact of soy isoflavone (another gointrogen) on thyroid function also found no relationship
“Thus, collectively the findings provide little evidence that in euthyroid, iodine-replete individuals, soy foods, or isoflavones adversely affect thyroid function.”
However, there is some evidence that consuming gointrogenic foods is associated with goiter under certain conditions. This observational study on Ethiopian children did find a relationship, but it’s important to note almost 2/3 of them were iodine deficient. So, as long as you’re getting enough iodine, I wouldn’t worry too much about cabbage coming to get you.
Extra Evidence on Cruciferous Vegetables
“Intake of cruciferous vegetables can prevent cancers, with an odds ratio of 0.77 and risk ratio (RR) of 0.96.”
Conclusion
As with anything, plant foods need to be evaluated based on their total health impact, and not just on their effect on one mechanism (I’m starting to sound like a broken record now). When we look at the impact increased vegetable and whole grain intake has on health, they are both so clearly beneficial (Wow! This record is really broken!). Trying to exclude plant foods to avoid certain defence chemicals is like not exercising because of increased risk of injury. The real risks come from abstaining. They are consistently shown to reduce the risk of heart disease, cancer, and diabetes, which are clearly the most pressing health concerns in the modern world.
We also need to look at what we’d be replacing plant foods with. The plant-phobic influencers will suggest we eat mostly, or exclusively, meat instead. This is insane. Partially because you would never take a shit again, but also because the deleterious health effects of red meat consumption are well documented. We’d be drastically increasing our risk of heart disease and cancer because we’re worried uncooked beans will give us a tummy ache.
It would certainly be nice if vegetables were bad for us. Then we can feel good about omitting them for steak everyday. However, you should be skeptical of people telling you this, because they know it’s what you want to hear. It’s the same reason the biggest fitness influencers are the ones selling you six-minute-abs, or a chest workout that’ll bring your wife back. The real, boring truth is that long term health involves all the slightly uncomfortable stuff we know we should all do more of. That means going for a run once in a while, lifting some weights, and yes, even eating our vegetables (maybe not brussels though, they can truly fuck off).
*Not paid for by united front of plants
Objection: you didn't show that plants aren't _trying_ to kill us, just that they're not very good at it. I still don't trust those little sociopaths.