Sarah the Healthy Home Economist online recently posted an article about how green smoothies can “DEVASTATE” your health. The content was so unsubstantiated that at first I refused to respond to it. But Amanda said, “She has a big audience and people are freaking out about it.”
Sarah cites the oxalates phenomenon, wherein a natural compound (oxalates) occasionally bind to calcium to cause kidney stones. (She infers, without citing evidence, that other more serious health consequences could also be possible.) Greens have oxalic acid in them. Sarah makes several logic leaps and concludes that no one should be drinking green smoothies.
I’m not going to promote her blog article by pointing to it here. She rates her content for how controversial it is. Controversy generates more readers, I guess. It also has the potential to do harm, if what you’re saying is (a) undocumented, (b) contrary to hundreds of studies about the benefits of greens, and (c) featuring a bizarre and untenable conclusion.
Just because someone posts stuff on the internet does not automatically endow that person with credibility. Her argument locks in on a detail — that greens are high in oxalic acid — and misses the larger picture.
Only one source is listed at the end of her article and none are quoted or referenced. The source is a PhD’s book on oxalates and autism and “chronic disorders,” but she never quotes the author or anyone or anything else, so I’m not sure how many of her claims came from this one guy, or what.
I don’t bet the farm on one book or one source. There are quite a few other sources that show that some of the anti-nutrients in our most nutrition-dense foods, actually work together synergistically for our health, rather than against it. I’ve done quite a few blog series on anti-nutrients such as oxalates, goitrogens, purines, and phytates, concluding that none of the anti-nutrients should generally cause people to avoid foods containing them.
Note that at the end of the article, Sarah says to eat greens, if you like them, but not very much. Always cook them, she says, and eat them with butter.
Let me quote Dr. Norman Walker in his book Fresh Vegetable and Fruit Juices: What’s Missing in Your Body?
“Spinach should never be eaten when cooked unless we are particularly anxious to accumulate oxalic acid crystals in our kidneys with the consequent pain and kidney trouble. When spinach is cooked or canned, the oxalic acid atoms become inorganic as a result of excessive heat and may form oxalic acid crystals in the kidneys.
“When the food is raw, whether whole or in the form of juice, every atom in such food is vital ORGANIC and is replete with enzymes. Therefore, the oxalic acid in our raw vegetables and their juices is organic, and as such is not only beneficial but essential for the physiological functions of the body.
“The oxalic acid in cooked and processed foods, however, is definitely dead, or INORGANIC, and as such is both pernicious and destructive. Oxalic acid readily combines with calcium. If these are both organic, the result is a beneficial constructive combination, as the former helps the digestive assimilation of the latter, at the same time stimulating the peristaltic functions in the body.
“When the oxalic acid has become INORGANIC by cooking or processing the foods that contain it, then this acid forms an interlocking compound with the calcium, even combining with the calcium in other foods eaten during the same meal, destroying the nourishing value of both. This results in such a serious deficiency of calcium that it has been known to cause decomposition of the bones.”
So according to Dr. Walker, what Sarah is telling her readers to do is really terrible advice.
One of my favorite sources is George Mateljan, because his staff, and his book The World’s Healthiest Foods, review and quote a tremendous amount of empirical data before making claims. Each section contains an extensive bibliography, and the conclusions are scientific and objective.
He says that a review of the peer-reviewed research reveals that the ability of oxalates to lower calcium absorption is small and does not outweigh the ability of those foods to contribute significant calcium to the diet, since spinach is rich in calcium.
So, one of the primary recommendations of most the sources I’ve read, to avoid stones forming in the body, is to get plenty of calcium from plant sources.
So, the high calcium content in spinach may actually inhibit the formation of stones, even though spinach is also high in oxalates. This is at least some logic or evidence, then, underpinning my theory that there are far more synergies than we currently know about in whole, raw plant foods leading to their clear, incontrovertible place (based on volumes of published research) as the necessary mainstay in our diet. We know that people the world over who eat mostly whole, raw foods simply don’t get sick. We don’t always know WHY.
So screaming that the sky is falling about one compound—in an entire class of our most nutritious foods—seems not only unwise, but even irresponsible, if you have an audience and give nutrition advice.
The jury is still out on so many of the issues Sarah the Healthy Home Economist takes strong, unilateral stands on. For instance, what really causes oxalic acid buildup. (She quotes ZERO evidence that greens do.) Whether greens are high in oxalates are only ONE issue related to whether they cause kidney stones. What if they also have dozens of other nutrient compounds, and fiber, that PREVENT stones from forming? A relevant example would be Mateljan’s review of the published, peer-reviewed literature on spinach, oxalates, and calcium as mentioned earlier.
After I investigated this issue, I wrote this in Chapter 1 of 12 Steps to Whole Foods:
“The research is not clear that restricting foods such as spinach helps prevent stones in those who have previously had them. Many researchers believe that dietary restriction cannot reduce risk of stone formation. In fact, some foods that were assumed to increase stone formation because of oxalate content (like black tea) have appeared in more recent research to have a preventative effect.
“Further, cooking has a small impact (about 10%) on the oxalate content of foods, with no statistically significant lowering of oxalates following blanching or boiling of greens. It appears that the nutritional advantages of eating raw greens continue to far outweigh any benefit of cooking them.”
And yet, with slim evidence, if any, Sarah says green smoothies can “devastate” your health and advises at the end of the article, “Skip the Green Smoothies!”
She undertakes no discussion of the true baddies that cause kidney stones:
Salty foods (or any refined salt)
Oxalates in spinach (also strawberries, soy, and many other foods) can be difficult to digest for a tiny percentage of the population who are suffering from a few very rare disorders (absorptive hypercalciuria type II, enteric hyperoxaluria, primary hyperoxaluria). But let’s not throw the baby out with the bath water here. If you don’t have these disorders, and 99+% of those reading this don’t, greens are not just good food—they are powerful good medicine!
Leafy greens are the most nutrient dense foods on the planet, and cooking them as Sarah instructs kills 100% of their enzymes, and most of their vitamins and minerals, too.
Sarah the Healthy Home Economist uses hyperbolic words to terrify people that eating nutrient dense foods could kill them, but she cites no research whatsoever. She implies that cases of painful sex are on the rise (where does that data come from? Is there any data?) and that oxalates are a “possible culprit.”
There are no references to check, and the bigger issue to me is, if people develop kidney stones, or crystalline deposits in other parts of the body, are greens the real culprit? How would you isolate that factor? Show me the study that did.
It’s terribly unlikely that greens are why we have lots of kidney stones, since almost nobody in America eats very much green food.
And in addition to thousands of testimonials we’ve received, my own research (175 subjects) shows massive health benefits to the green smoothie habit, as published in my bestselling book, The Green Smoothies Diet. In that research, not one person reported kidney stones as a side effect of starting the daily green-drink habit. And yes, we asked.
Nutritionally, crystalline deposits are likely caused by highly acidic foods, especially salt, and not drinking lots of water.
So let’s minimize or eliminate the baddies, listed above. Let’s eat more of the foods that have been linked by hundreds of studies world-wide, to ideal weight and minimized disease risk.
(Dr. Joel Fuhrman does this best, in Eat to Live, quoting literally hundreds of published studies showing the benefits of eating plant foods. This is highly recommended reading.)
Let’s don’t kill greens with cooking, and slather butter on them.
If you’re worried about oxalates, let’s not “throw the baby out with the bathwater,” because people who don’t metabolize that anti-nutrient well need the nutrition in the leafy greens as much as anyone, if not more. Instead:
Let’s rotate greens, use a wide variety in our green drinks—not just spinach. Amanda says a friend of hers had oxalate issues and one took a calcium-magnesium supplement and the pain went away. Several experts I have read suggest getting more calcium from plant sources.
And, eat some good fats with your green smoothie, like avocado or coconut oil or flax oil, to increase calcium absorption. One of my favorite lunches is a quart of green smoothie, with some homemade guacamole and “corn chips” (organic corn tortillas, quartered with a pizza cutter and broiled on both sides, no oil or salt needed).