Is kale bad for you – or good for you?
We regularly read stories and “studies” about foods which either give glowing reports about their benefits or dire warnings about their dangers.
Kale has been called a “superfood” and, more recently, a “dangerous accumulator of toxins.”
Kale is a Superfood!
On the superfood side, consider this gushing article about kale from Weight Watchers:
“While no single food can make or break your health, kale is a standout pick to put on your plate. As part of an overall healthy pattern of eating, research has linked the cruciferous veggie and/or its nutrients to a number of potential health benefits:
Reduced disease risk: Kale is rich in antioxidants that help protect cells from oxidative stress and DNA damage, two processes that can increase one’s risk of developing heart disease and type 2 diabetes. Another potential benefit: High consumption of brassica vegetables—a family that includes broccoli and cauliflower alongside kale—was correlated with a decreased incidence of some cancers in a landmark research review published in Cancer Epidemiology, Biomarkers & Prevention.
Blood pressure regulation: Eating foods that contain potassium, calcium, and magnesium may improve blood pressure levels, studies have shown. While more investigation is needed to pinpoint the effects of kale specifically, many health experts advise eating a diet high in those minerals to help reduce the risk of hypertension.
Vision protection: Leafy greens such as kale are rich in lutein and zeaxanthin, two nutrients linked to a lower risk of age-related macular degeneration and cataracts, according to a 2013 review in Nutrients. The duo also helps protect ocular tissues from sun damage. And once consumed, kale’s motherlode of beta-carotene converts to vitamin A, which plays a key role in corneal health.
Better bone health: Kale is a potent source of bone-building vitamin K—2 cups of leafy goodness deliver 293% of your daily recommended intake of this underconsumed nutrient. One large-scale study of women found that adequate vitamin K intake was associated with a reduced risk of hip fracture. And not to be overlooked: 2 cups of kale also contain 6% of the recommended daily value of calcium, another nutrient needed for strong bones.”
Kale is Dangerous!
And now, on the other side of the coin, let’s hear about how dangerous kale is from a highly trusted (lol) media outlet:
“Seven out of eight US kale samples recently tested for toxic PFAS “forever chemicals” contained high levels of the compounds.
The testing looked at conventional and organic kale bought at grocery stores across the country, and comes after Food and Drug Administration analyses conducted between 2019 and 2021 found no PFAS contamination.
The findings “stunned” researchers who expected to find low levels of the chemicals, said Robert Verkerk, founder of the Alliance for Natural Health non-profit, which produced the paper.
‘Forever chemicals’ exposure can lead to low birth weight and obesity in later life
“It’s pretty scary and there’s no easy solution,” he said, adding that the findings highlight the need for the FDA to implement a more robust PFAS testing program for the nation’s food supply.
PFAS are a class of about 15,000 compounds typically used to make products across dozens of industries resistant to water, stains and heat. They are called “forever chemicals” because they do not naturally break down, and are linked to cancer, kidney disease, liver conditions, immune disorders, birth defects and other serious health problems.
The report comes amid growing calls for stronger action around PFAS-contaminated food, which is considered to be the most significant exposure route to the chemicals. In recent months, independent research has found PFAS in protein powders, juice drinks and other food products.
Studies have previously found PFAS in vegetables in fields where sewage sludge was laid as an alternative to fertilizer, and the FDA claimed it had “no indication” of a health threat in PFAS it found in vegetables grown in 2018 near a North Carolina PFAS manufacturing plant.
The new paper found levels as high as 250 parts per trillion (ppt), though no limits for PFAS in food exist in the US. However, the Environmental Protection Agency has found that virtually no amount of exposure to some PFAS compounds in drinking water is safe.
The kale was sent to an EPA-certified lab and tested with the same method used by the FDA. Bagged and loose kale was bought at Stop & Shop, Whole Foods, Weis and Publix food markets. Among the brands that showed PFAS contamination were Nature’s Promise Organic, GreenWise, By Nature and Palmetto Gardens. Only loose kale from Baker Farms did not contain the chemicals.
Organic kale had higher levels of PFAS, which Verkerk said was “a bit of a shock finding”. He added that the group tested kale because it “wanted to look at an archetypal healthy vegetable” that was high in protein, which PFAS compounds bind to. The source of the contamination is unclear, but Verkerk said he suspected tainted water was probably to blame, though it was also possible the kale was grown in fields where sludge was spread.”
Kale is High in Oxalates
Yet behind the potential for contamination with chemicals and heavy metals – which you could avoid if you grew kale yourself – there is a further risk to kale consumption:
“Oxalates are also found in a majority of plants, but they are the most abundant in leafy plants, such as spinach, chard, and kale. Oxalic acid is the component within oxalates that seems to have the most detrimental anti nutrient effects.
Oxalic acid has a strong affinity to bind to nutrients, such as sodium, potassium, and calcium making them difficult for the body to absorb and utilize. Oxalic acid bound to these minerals forms an oxalate salt which can often crystalize and build up within the kidneys, leading to the formation of kidney stones. Outside of the kidneys, the structure of oxalates is very thin and sharp. (24 )
Due to oxalates, and other plant chemicals, nutrients contained in plants are much less bioavailable. For example, 100 grams of raw spinach contains 15% or the RDI of iron, and 34% of the RDI of calcium. However, The absorption of iron in spinach is about 12%, and the absorption of calcium is about 5% (25, 26).
When oxalates do not bind to minerals, their concentration begins to build up in the bloodstream, and deposit in bodily tissues, most commonly the kidney. Over 80% of kidney stones are a result of calcium oxalate buildup in the kidney.
Oxalates also can deposit in the brain, eyes, muscles and joints. Due to the sharp needle-like structure of oxalates, oxalate crystals can physically damage tissue, and damage the composition of the cell (27).
Many of the oxalates you consume will bind to calcium within the digestive system. Those that don’t, however, travel to the kidneys, where they can contribute to the development of kidney stones. In fact, it’s estimated that at least 8 out of 10 kidney stones consist of oxalates (28).”
This is a real danger that is often overlooked. Kidney stones are appearing in the population at an absolutely epidemic level right now – do we really want to risk getting them?
We don’t eat spinach, rhubarb, or other high-oxalate foods if we can help it. I can often taste the oxalates on when I eat certain vegetables, and cease immediately. Raw beets, raw or cooked spinach, boiled Colocasia esculenta leaves (the raw ones will really tear you up, but even cooking isn’t enough for me), raw Malabar spinach, and raw amaranth all bother me, so I avoid them.
I quit growing kale some years ago, just because I don’t really like it – though I wouldn’t be above growing a patch to feed to the chickens.
Yet if you do grow it, there may be good ways to avoid the oxalates:
Okay, I laughed.
Final Thoughts on Kale
My two cents, for whatever it’s worth: Kale probably isn’t a demon or an angel. I trust studies about as much as I trust anything else coming from the mainstream media. If it’s been a human food for ages, it’s probably fine in moderation. The human body can run on plenty of different fuels. I just wouldn’t live on green smoothies, and if I dealt with kidney stones, I would eat a super-low oxalate diet. Also, one of the best uses for vegetables is to feed them to animals, and then eat the resulting milk, eggs or meat produced, as those are the best foods in the world.
So – what do you think about kale? Let me know in the comments.