By Dick Thomas Johnson from Tokyo, Japan – Independence Day: Resurgence Japan Premiere: Liam Hemsworth, CC BY 2.0, Link
It happens more often than you’d think that people pursue the healthiest diet possible, develop an acute health problem, then run to a diet fad in the opposite direction. The more radical your diet, the more carefully you must consider it, because you have a smaller sample size of people that way. Say what you will about the Standard American Diet (and there is plenty to be said), but we know what the health consequences of it are, and most of them aren’t acute. If there were large numbers of acute illness, we’d find out quickly and adjust. This isn’t to say we should always stay with the herd in our dietary decisions (veganism itself is widely considered radical), but it does mean that unusual dietary patterns need to be approached with caution.
Liam Hemsworth recently developed a kidney stone and discontinued his vegan diet, not because he was necessarily on a fringe diet, but he was eating large quantities of conventionally healthy foods. He was getting too much of a good thing. Here’s Hemsworth’s description of his diet:
“Every morning, I was having five handfuls of spinach and then almond milk, almond butter, and also some vegan protein in a smoothie,” he said. “And that was what I considered super healthy. So I had to completely rethink what I was putting in my body.”
The nutrient of concern here is oxalates, which are particularly rich in raw spinach and nuts. To compound this problem, it’s essentially the entire vegan diet that is high in oxalates—rhubarb, soy foods, potatoes, sweet potatoes, berries, tea, coffee and bran cereals. By contrast, animal foods have only trace amounts. If I was a naive vegan and I just had a painful kidney stone, looking at the list of high oxalate foods might sell me on the carnivore diet.
And this is largely how the story has been covered. But veganism isn’t the scapegoat it’s being made out to be. The development of kidney stones is not a straightforward consequence of an oxalate rich diet. A mass of research runs counter to this simplistic understanding.
Vegetarians (a category which includes vegans) had a 31% lower risk than meat eaters of being hospitalized for kidney stones according to a 2014 EPIC-Oxford study.
A study by the Harvard School of Public Health found that a DASH diet (Dietary Approaches to Stop Hypertension) actually was associated with lower risk of kidney stones. The Dash diet encourages high intake of fruits, nuts, vegetables, legumes and low-fat dairy, while limiting the intake of salt, sweet beverages and meat.
What about oxalate rich beverages like coffee, tea and beer? An 8 year study with over 194,000 participants again found the opposite. These beverages are associated with a decreased risk of kidney stone formation.
As is typical of complex systems like the body, different variables point in different directions. “Vegan diets are higher in some elements that increase the risk of stones, lower in some, and higher in some things that prevent stones,” explains Jack Norris.
The critical point is that kidney stones form due to higher levels of oxalate in urine, not in the diet. Keeping plenty hydrated, which dilutes oxalate levels in urine is an obvious counter-measure.
Additionally, there’s a lot that happens in the gut that renders dietary oxalate irrelevant. Certain nutrients bind to oxalate, including, calcium, citrate and potassium. These nutrients are rich in a plant-based diet. Potentially relevant for vegans (who aren’t consuming dairy as a calcium source) the lower risk was true even for those with a lower calcium intake.
(intended to be read with the understanding that I am not a doctor)
- Avoid high dose Vitamin C supplements, as oxalate is a byproduct of vitamin C absorption
- Drink plenty of fluids
- Boil or blanch greens and then discard oxalate rich cooking water
- If you are at higher risk of kidney stones, you may consider asking your doctor about calcium citrate or potassium citrate tablets
- Eat a balanced diet, that doesn’t rely on any given food very heavily
For a deep dive into this topic from a vegan perspective, see this guide by Jack Norris, RD.