When I started my raw food journey over 30 years ago, spinach was one of my favorite leafy greens. I'd loved spinach since childhood, so raw spinach quickly became my staple salad green next to lettuce. I'd heard that spinach contained notable amounts of important minerals like calcium and iron, so I thought I was getting a decent amount of these minerals.
I love to learn as much as I can, so I started researching the nutrient content of my diet. It was then that I came across up-to-date scientific studies regarding oxalate.
For those of you not familiar with this term, oxalate (also known as oxalic acid) is a substance found in certain foods that binds to minerals like calcium, iron, and zinc, making them less bioavailable. I learned that spinach is rich in oxalate. What this means is that much of the iron, zinc, and calcium found in raw spinach is bound to oxalate making these minerals less nutritionally usable by the human body.
Because of this, the conversation around oxalate in the raw food and plant-based community has generally centered around avoidance of oxalate-containing greens for the reasons mentioned earlier. However, recent research has indicated that some oxalate in one’s diet may actually be beneficial for microbiome diversity. This research centers around Oxalobacter Formigenes, a type of bacteria that inhabits our digestive tract and uses oxalate as its major energy source.
O. Formigenes is considered to be a probiotic, and has been found to survive well in the microbiome of people who consume foods containing some oxalate. Research has found that the prevalence of O. Formigenes in the microbiomes of people eating standard western diets is about half of populations that consume more plant foods. Additionally, there are other types of probiotics that consume oxalate, so as it turns out, having some oxalate in the diet may help increase microbiome diversity and the benefits associated with it.
Often, we hear about concern regarding kidney stone formation and the consumption of oxalate-containing foods. Results from a case-controlled study suggested that lack of O. formigenes colonization is a risk factor for recurrent oxalate stone formation (Kaufman et al., Ellis et al.). What this means is that recurrent oxalate stone formation is associated with lower amounts or the absence of O. formigenes in one's microbiome. Given that oxalate is a food source of O. formigenes , it looks like some oxalate in one's diet can actually be protective against recurrent oxalate stone formation. Of course, it is important to note that it's important to consult with one's healthcare provider who is well-researched on this topic when making dietary and healthcare decisions. This information is both fascinating and encouraging and we look forward to future research shedding light on this important topic!
The bottom line is that our stance on oxalate has not changed. We still think that it is preferable to focus on lower oxalate greens in our diet to help with mineral use in the body, but we do not think that eliminating these foods completely is essential (unless otherwise instructed by a healthcare provider) since oxalate can serve as a food source for O. Formigenes and other probiotics to assist in creating greater microbiome diversity and other potential benefits.
References and Research:
Ellis ML, Dowell AE, Li X, Knight J. Probiotic properties of Oxalobacter formigenes: an in vitro examination. Arch Microbiol. 2016;198(10):1019-1026.
Kaufman DW, Kelly JP, Curhan GC, et al. Oxalobacter formigenes may reduce the risk of calcium oxalate kidney stones. J Am Soc Nephrol. 2008;19(6):1197-1203.
Liebman M, Al-Wahsh IA. Probiotics and other key determinants of dietary oxalate absorption. Adv Nutr. 2011;2(3):254-260.
PeBenito A, Nazzal L, Wang C, Li H, Jay M, Noya-Alarcon O, Contreras M, Lander O, Leach J, Dominguez-Bello MG, Blaser MJ. Comparative prevalence of Oxalobacter formigenes in three human populations. Sci Rep. 2019 Jan 24;9(1):574.
Turroni S, Bendazzoli C, Dipalo SC, et al. Oxalate-degrading activity in Bifidobacterium animalis subsp. lactis: impact of acidic conditions on the transcriptional levels of the oxalyl coenzyme A (CoA) decarboxylase and formyl-CoA transferase genes. Appl Environ Microbiol. 2010;76(16):5609-5620.