In wellness culture there is always a new food category causing fear. Seed oil. Lectins. Gluten (even if you’re among the 99% of people who don’t have celiac disease). Recently, spinach, almonds, and beets are being overlooked due to new awareness about oxalates: naturally occurring compounds often labeled as “anti-nutrients.” The name sounds ominous. But science? Not so much.
What are oxalates?
Oxalates are natural compounds found in many plants that make it onto your plate. They bind to minerals like calcium, magnesium, potassium and iron, and slightly reduce their absorption – that’s why they’re often called anti-nutrients, say. Maddie Pasquarillo, MS, RDNA dietitian based in Brooklyn. (“A little” is the key word here, as they don’t automatically cancel out the nutrients in your salad.)
Unless your diet consists entirely of chicken breasts and protein shakes, you’re probably eating your fair share of oxalates every day. Spinach has the highest concentration, say 40 times more, of oxalate than most other vegetables. Janelle Connell, RDNA dietitian and translational science nutritionist Viom. Other high oxalate foods include beet greens, Swiss chard and rhubarb. They also appear in many foods you might never think twice about, from almonds and raspberries to dark chocolate. That’s what makes things confusing: This list matches almost exactly the foods that get the green light from dietitians and health experts.
Are oxalates harmful?
Like many nutrition villains before them, oxalates have been taken out of context online, making them more feared than legitimately understood. “Many people believe that they will block or destroy the minerals in foods, which is not the case,” says Pasquariello. Although they may inhibit their absorption, it is not to a significant amount. And for most people, their gut microbes do a pretty good job of breaking down oxalates before they have a chance to cause problems.
“When certain microbes are present and thriving, less oxalate is absorbed into your blood and passed to your kidneys, leaving less raw material,” says Connell. From there, your kidneys filter the oxalates and pass them out through waste. There is just one important exception.
Some people need to be more cautious than others when consuming large amounts of them. In sensitive people, excess oxalate can combine with calcium in the urine, forming crystals that can eventually form kidney stones (which have a predictable effect). 11% adults in the United States). Calcium oxalate stones are the most common type of kidney stones, says Connell, making it worth limiting oxalate if you’re already sensitive to it. The risk increases if you have low calcium intake, don’t drink enough fluids daily, or have certain gut problems.
Connell says some people lack specific gut microbes to adequately process oxalate. These include Oxalobacter formigenes, “whose whole job is to break down oxalate before it can be absorbed,” as well as Lactobacillus and Bifidobacterium (both of which are common in probiotic supplements). Based on Viome’s internal data, about a quarter of their customers are at higher risk of oxalate buildup because they lack these microbes. Some people may notice bloating or GI discomfort after eating high oxalate foods, although symptoms are not always obvious.
Should you avoid oxalates?
“For most people with a balanced diet, oxalates aren’t a problem,” says Connell. “Your gut and kidneys are built to handle them, and you excrete the excess through stool and urine.” Pasquariello reiterated that oxalates are present in abundance in healthy plant foods that are highly beneficial to your health. In other words, you shouldn’t start second-guessing your Sweetgreen Slope bowl or dreading greens like a picky five-year-old.
