It’s time to blend some reality into your diet.
The green smoothie has become the go-to beverage for Americans wanting to boost their intake of nutrient-rich fruits and veggies, improve digestion, and maybe even shed a few pounds. Even Reese Witherspoon swears by having one every morning.
But before you reach for the kale, remember this: “Just because it’s green doesn’t mean it’s good for you,” biohacker Dave Asprey told The Post.
The problem is that the typical green smoothie is packed with leafy greens like spinach, kale, and Swiss chard — all of which are very healthy, but also loaded with high levels of oxalates.
Small amounts of these naturally occurring compounds aren’t typically harmful, but when consumed in large quantities, oxalates can bind to minerals like calcium, preventing them from being absorbed in your digestive system.
The real trouble starts when oxalates bind to calcium in your blood, forming tiny, sharp crystals that can be deposited anywhere in the body, causing muscle pain. If your body is low on urine volume and high on oxalates, these minerals can build up and lead to painful kidney stones.
“There’s this idea that the smoothie will clean you up, but it’s probably going to clog your kidneys,” Asprey said.
Oxalate crystals are behind a whopping 80% of kidney stone cases in the United States. And it’s not just the leafy greens — foods like raspberries, chocolate, almonds and even green tea are also packed with oxalates.
“Your body can only handle 200 milligrams [of oxalates] a day, and one green smoothie with almond milk and spinach can have five times more than what your body can take,” Asprey explained.
Like with most things, moderation is key. Doctors say oxalates are fine in small doses, but the worst cases typically happen when people dive into juice or smoothie cleanses.
In one case, a 65-year-old woman with a normal kidney was drinking a green smoothie loaded with oxalates as part of a cleanse, only to end up with acute kidney injury.
In another, a 68-year-old man went into kidney failure six months after starting a daily juice regimen high in spinach. His oxalate intake was 10 times higher than a normal diet.
“People think, ‘Oh, it’s a green smoothie, it’s got to be good,’ but it could actually be working against you,” Asprey said.
Even small amounts of oxalates can cause burning in the eyes, ears, mouth, and throat in sensitive people. Larger quantities might cause abdominal pain, muscle weakness, nausea and diarrhea.
But don’t rush to toss out all those greens just yet. If you’re prone to kidney stones or have kidney disease, your doctor might suggest a low-oxalate diet. For the rest of us, there are ways to prevent oxalate buildup.
One of the best ways to reduce your chances of forming calcium oxalate stones is by drinking plenty of water. Staying hydrated helps thin out your urine, making it harder for calcium and oxalates to build up and form those painful crystals.
You should also increase your calcium intake. By eating enough calcium, it binds with oxalates in your stomach and intestines before it ever reaches your kidneys. Adding magnesium and zinc to your diet can also help lower oxalate absorption.
Also, you may want to ease up on vitamin C supplements, which can increase oxalic acid production in your body. Boosting your gut health with fermented foods and probiotics can also help break down oxalates.
Still not ready to ditch the green smoothie? Try swapping out some of the high-oxalate ingredients. Arugula instead of spinach, sunflower seeds instead of almond butter, and blackberries instead of raspberries are all great alternatives to lower those levels.
