In Functional Medicine recommendations, sometimes one person’s superfood is another person’s poison. Such is the case with oxalates, which are found in high concentrations in many presumed health foods.
Oxalates are naturally occurring compounds in foods like spinach, kale, nuts, beans, and even chocolate that can interfere with the absorption of vitamins, minerals, and other nutrients. In susceptible individuals, foods that seem healthy can become toxic. They are considered “anti-nutrients” because they protect the plant against predators, from harmful bacteria to insects and animals. In additional to oxalates that originate in food, called exogenous oxalates, the human body also produces oxalates mainly in the liver from excess vitamin C, fructose, and yeast. (Other anti-nutrients include phytic acid and lectins). Unfortunately, oxalates form painful crystals in various places such as the kidneys, bladder, vulva, gut wall, and other mucosal membranes in susceptible people.
What Increases Your Risk of Oxalate Overload?
You have to be sensitive to them, because of your genetics, gut bacteria (dysbiosis, or missing the microbes that process oxalates), or nutritional deficiencies, like vitamin B6, magnesium, and thiamine. The gene involved in oxalate breakdown is called SLC26A1. The bacteria that break down oxalates are the Oxalobacter formigenes and Lactobacillus species. Eating too many oxalates, like more than 250 mg a day, also puts you at risk for problems.
You can get diagnosed in a simple urine test that measures oxalates, called the organic acid test. For best results, work with a functional medicine clinician. You can also test for the oxalate-degrading bacteria in your stool.
What Symptoms Are Caused by Oxalate Overload?
- Gut problems including bloating (oxalates can irritate the mucosal lining throughout the body)
- Chronic pain
- Kidney stones
- Interstitial cystitis (a syndrome of painful bladder)
- Vulvar pain and vulvodynia
- Joint pain
- Inflammation (muscle stiffness, bloating)
- Autoimmune conditions
- Mineral deficiency
How Can Oxalate Overload Be Prevented or Treated?
The best way to prevent or treat oxalate overload is to reduce the consumption of high oxalate food. It’s best to switch first to a moderate oxalate diet (if you go too low on oxalates too fast, you can form painful crystals). Then after 2-4 weeks, try low oxalate. Probiotics and oxalate-degrading supplements may help too. Aim for a healthy calcium-oxalate ratio in the body. A reasonable goal is to consume less than 100 mg of oxalate per day.
Limiting protein intake can also reduce the urinary excretion of oxalates. Finally, the intake of pyridoxine (vitamin B6) reduces the excretion of oxalate.
Summary: What Helps?
- Eat low-to-medium oxalate foods: Wild-caught fish, pastured poultry, cabbage, bok choy, broccoli, Brussel sprouts, celery, endive, cauliflower, cucumber, zucchini, lettuce, onions, and mushrooms.
- Avoid the high oxalate foods, which tend to be the dark leafy greens. One cup of raw spinach contains around 656 mg oxalate. This is a great resource listing oxalate count in various foods.
- Supplement with vitamin B6, calcium, and magnesium, which can reduce the effect of oxalates.
- Skip black tea and instant coffee, both very high in oxalates. Green and herbal tea are lower in oxalates.
- Probiotics can help. Oxalobacter formigenes and Lactobacillus species as mentioned previously help to degrade oxalates in the gut. Taking these as probiotics may help.
It may seem restrictive, but after one week on a low oxalate diet, many of my patients lost a lot of abdominal bloating and dropped a few kilos/pounds.