Should You Quit Drinking Green Smoothies?

Green smoothies don't sound particularly appealing. You've got to be extremely open-minded to dare to put spinach, kale, swiss chard, collard greens, celery, parsley, mint, broccoli and even lettuce in a drink, don't you? Sure, you can add oranges, apples, honey and other sweet things to make green smoothies more palatable, but that will never hide the fact that they're basically medicinal drinks that are more about health than taste. 

People try green smoothies for all kinds of reasons — to add juice to their workout regime (literally), because they're worried they're not eating healthily enough, in the hope to lose weight, or because they just can't say no to that crunchy, health-obsessed, friend. Once they have discovered the joys of green smoothies, they might just find it hard to stop. Getting used to the unorthodox taste isn't that hard, that energy boost and remarkably smooth skin, may soon turn them into "green smoothie converts" who start every day with that all-natural health infusion. 

Most health fads get some backlash, and green smoothies are no exception. Blog posts warning that the high oxalate levels in your green smoothies may be damaging your health have started to appear on the internet. If you've seen them, you may now be worried that the positive lifestyle change you've come to love is actually bad for you. 

What Are Oxalates?

Oxalates are organic acids naturally produced by plants, animals, and people. The human body makes its own oxalates and gets more from food. The body can also convert other substances, like vitamin C, into oxalates. You might be surprised how many different kinds of foods contain oxalates — you'll find them in nuts, seeds, vegetables, mushrooms, and fruits. 

To name some examples, tangerines, rhubarb, strawberries, almonds, soybeans, wheat bran, and black tea, all contain oxalates. Some foods have much more than others, however. Looking at a list of the highest-oxalate foods is a bit like looking at your shopping list if you're a green smoothie fan — the greens used for green smoothies are nearly all very high in oxalate. 

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Not only do they write about oxalate calcium kidney stones, they also caution that oxalate stones can form all over the body, including the heart, brain, thyroid, lungs, and skeletal muscle. Some even say that too much oxalate can lead to autism in children. Should you be worried about the oxalates in leafy greens, whether you're an avid green-smoothie consumer or a vegan who naturally eats a lot of foods that are very high in oxalates?

Are Green Smoothies Making You Ill?

Low-Oxalate Diets

A high-oxalate diet is certainly very dangerous for people with a few rare health conditions — primary hyperoxaluria, absorptive hypercalciuria type II, and enteric hyperoxaluria. These people need to be on very strict low-oxalate diets, limiting their daily intake to 50 mg. By contrast, look how many milligrams of oxalate are in 100-gram servings of the following popular green-smoothie ingredients:

• Spinach — 750 mg
• Beet greens — 610 mg
• Parsley — 100 mg
• Collard greens: 74 mg

Simply said, people with these conditions shouldn't go anywhere near a green smoothie. 

Kidney Stones

One in 10 people will have at least one kidney stone during their lifetime. Kidney stones come in a few different types, but 75 to 90 percent of all kidney stones are calcium oxalate stones. Limiting oxalate intake may be a good idea for people who have had this type of kidney stone before because kidney stones have a high risk of recurrence, but there is much more to preventing calcium oxalate kidney stones than quitting leafy greens. 

The National Kidney Foundation believes that cutting high-oxalate foods from your diet altogether isn't good for your overall health, and instead advises at-risk people to eat and drink calcium and oxalate-rich foods together in a single meal: this means "oxalate and calcium are more likely to bind to one another in the stomach and intestines before the kidneys begin processing, making it less likely that kidney stones will form". 

If you're at risk of developing kidney stones because you have had them before, you should make sure you drink ample fluids, especially if you've been sweating. Cut down on sodium, another source of oxalate, and stay away from sports drinks such as Gatorade. Animal protein is another major contributor. Perhaps most importantly, you should also take the advise your nephrologist and urinary specialist give you very seriously, and use any medication that you're prescribed. 

Not In A High-Risk Group?

The fact that there is no recommended upper oxalate limit for people who don't have primary hyperoxaluria, absorptive hypercalciuria type II, enteric hyperoxaluria, or a history of kidney stones should tell you a lot. In fact, most people can comfortably live their whole lives without knowing what oxalates even are, much less paying attention to how many oxalates are in their food.

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It's probably best to take a common-sense approach to this issue, and to neither make green smoothies your main source of nutrition nor shun leafy greens and go on a low-oxalate diet. Enjoy your green smoothies in moderation, along with many other types of food.