The fact is that kidney stones are very common, and the most common kind of kidney stones are calcium oxalate stones. These form when oxalic acid and calcium bind together forming the salt, calcium oxalate. The chemical affinity of these two substances to come together is very strong.

So, it would seem to make sense to avoid oxalic acid as much as you can. However, it’s not easy to do because oxalic acid occurs widely. It’s in practically all fruits and vegetables, though in widely varying amounts. The foods with the highest content of it are spinach and chard. And of the two, you know how popular spinach is. Once they started selling it in plastic bags, pre-washed, it started flying off the shelves. It used to be that you could only buy spinach in bunches that were loaded with dirt and sand. You had to soak and rinse it 3x to get it clean. But, those days are gone, and I don’t miss them.

But, does spinach, because of its high oxalic acid content, cause kidney stones?  The answer is: not usually. I’m sure that if you took a poll of kidney stone patients in the hospital, you would find out that most kidney stone patients eat no more spinach than average and often less than average. There are people who get kidney stones who don’t eat any spinach at all.

So, how do they get them? The body generates oxalic acid as a product of its own metabolism. You might say that it's a waste product. And, the way the body breaks down Vitamin C is to convert it to oxalic acid. Think of all the people who take thousands of milligrams of Vitamin C every day. Yet, you almost never hear of them getting kidney stones.

What I’m saying is that even though there is an epidemic of kidney stones, spinach-eating has very little to do with it, and in many cases, nothing to do with it.

Then, what is going on? I think we need to look at the other side of the equation: the calcium. It takes two to tango. When people have high urinary calcium, they will tend to form calcium oxalate kidney stones. I’m saying that the thing driving it is the calcium.

Many people have high urinary calcium from eating a high protein diet, and particularly a lot of meat. It’s been known for decades that high-meat diets cause high urinary calcium.

It’s easy to test your urine for calcium. Anyone can do it. You get this reagent called Sulcowitch Reagent and add it to the urine. You shake it. Then, you see if the urine turns cloudy. If it does, it indicates high calcium. One of the components of it is oxalic acid.

So, people wind up with high urinary calcium from eating high protein diets. What about talking calcium supplements? Does that contribute to the problem? I don’t have a definitive answer, but I’ll tell you that I don’t take calcium supplements. Unless you are extremely frail with brittle bones, I don’t think it’s worth it to take them. And, the whole idea that I need 1200 or 1500 mgs. of calcium each day to keep my bone strong is nonsense. I suspect I get about 500 mgs a day from my diet, and that’s plenty. I don’t want any more. I'm too aware of how pervasive pathological calcinosis is. And my bones? Like my muscles, they’re strong.  I have no doubt that my  bones are getting all the calcium they need.

So, I really want to emphasize that with normal consumption of spinach and chard, there is nothing to worry about. I buy spinach regularly and eat it several times a week. Chard, I do not buy as often, but I buy it occasionally, and in the fall, I grow swiss chard. I eat it out of my garden from October to April. I find that it’s much easier to grow swiss chard than it is spinach, plus, it’s such a beautiful vegetable. It really brightens up the garden.

However, it would be remiss of me not to point out that there are exceptions. I heard about a woman who went on a green juice fast in which she was drinking copious amounts of spinach juice. She was also taking copious amounts of Vitamin C, and as I told you, it converts to oxalic acid. The result was that she formed so much calcium oxalate, it shut her kidneys down completely, and she had to go on dialysis.

So, at the extremes of spinach consumption, it could be dangerous. Therefore, don’t do it. Don’t make a whole salad out of spinach. Just add a few leaves. And if you include spinach in your vegetable juice cocktail, just use a little spinach.  

Note that when you steam spinach, 30 to 40% of the oxalic acid winds up in the pot liquor, which you should discard.  I eat spinach both cooked and raw. I always add cooked spinach to my pasta, and it’s delicious. It’s so delicious, they even make pasta with spinach infused in it.

So, the idea of avoiding spinach completely because of the oxalic acid, I do not find appealing at all. But, being cognizant of the potential danger, I know I need to be moderate in my spinach consumption, and I am. I have never had a kidney stone, and I have every expectation of getting through my whole life without ever having that problem.