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Real Medicine: Why you should be careful about eating almonds

I remember it quite clearly. When it hit me, it was as sharp and as sudden as a bullet from a gun. Just a day before I had noticed that my urine looked a bit amber and now I had this sudden, sharp pain in my flank.

“You fool,” I told myself, “you have a kidney stone.”

I was pretty sure that’s what it was, but to make sure, I had my wife drive me to the ER where a CAT scan clearly showed a rather large and calcified stone in my right kidney.

Renal stones (nephrolithiasis) are much more common than I would have guessed. In the United States in 2000, almost two million outpatient visits resulted in a primary diagnosis of kidney stones. While there are several types of stones, the majority of them, over 80%, are made up of calcium combined with oxalate.

After a week of waxing and waning pain — pain that many women who have had kidney stones have compared to their labor pains — and an $8,000 dollar visit to an ER (a future story), my urologist decided we should blast the thing out of my kidney by using focused sound beams.

And so a few more thousand dollars later, with the use of the technique known as lithotripsy, my stone was broken into several sharp sliver like pieces that would pass, like, I suppose, real slivers of glass would, from me over the course of about a week.

For the few moments I had no pain, I began to wonder why I got these stones and if there was a way to prevent them. This was something I wasn’t hoping to have again.

I wondered if there was some correlation, or association, between the foods I ate and why I formed this kidney stone. And so, when I had the strength to do so, I began searching through the medical literature.

I found out that most stones are made up of calcium and oxalate but that the dietary Oxalate intake was far more important in causing these calcium oxalate stones. I might be a physician but I hadn’t the foggiest notion that calcium kidney stones were actually a combination of calcium and oxalate, and then it hit me like a ton of bricks, or better still, that kidney stone: I ate tons of almonds. OK, I ate ounces of almonds almost every single day, often as many as three small bags of roasted non-salted almonds.

Could it be that I was loading myself up with oxalates when I was munching on almonds?

I ran to my computer, did the standard Google search, and came up with what I had expected; almonds are loaded with oxalates (just below rhubarb and spinach), and eating too much of them, like I did, was potentially the reason why I got that kidney stone. And not only were almonds loaded with oxalates but the oxalates in almonds appeared to be better absorbed, according to a one study published in the Journal of Urology, into our body when compared to other sources of dietary oxalate.

I had always thought that eating almonds, instead of the usual snacks, would be good for me. Almonds after all were loaded with fiber, might help lower your cholesterol, and had antioxidants. Even Dr. Oz seems to believe that almonds are good for you championing them as “The best snack of all.”

“Because nuts are high in fiber and protein, they’ll satiate you so you’ll never be hungry. Because of my Turkish culture, I grew up eating almonds that have been soaked in water first. I still do that. It makes them taste completely different — very sweet,” Dr. Oz says.

What could go wrong?

But as I read the Almond Board of California site (almost all the almonds grown in the states are grown in California), I wondered why they suggested everyone have a handful of almonds a day? Why not just say eat almonds and eat lots of them? Was this a carefully vetted statement?

Here is just one of several statements made on their site:

Of all the things to love about almonds, this one should really get your heart pumping. Just a handful of almonds a day may help you maintain healthy cholesterol levels. And that’s good news for just about everyone as cardiovascular disease holds its spot as the leading cause of death among men and women in the United States.

California almonds are cholesterol-free and low in saturated fat, making them a deliciously tempting option for smarter meals and snacks. And research is now showing they may also help maintain a healthy heart. In 2003, the U.S. Food and Drug Administration released a health claim recognizing that California almonds can help you maintain a healthy cholesterol level. And no, you’re not dreaming.

Why do they keep saying a handful and why do they limit it to that amount? Do the almond growers know that eating too many almonds could be dangerous to your health? Are they afraid that perhaps the FDA would mandate that warnings be placed on foods loaded with oxalates, like almonds, because these foods might have some relationship or might even be causing thousands of us to form kidney stones and perhaps even worse, kidney failure?

I researched the topic even further. Eager to learn more I decided to see if the prevalence of kidney stones, the amount of people who had kidney stones in a given time, had increased over the past several years. What I learned is that the prevalence, in the United States, as well as most other nations, had about doubled in less than 10 years — the incidence is about one in 11 people in the United States now.

Many experts, from what I read, seem to blame this epidemic of kidney stones with the increase in obesity and diabetes, which doctors say is associated with stones, while some even blame global warming; more sweating means more dehydration, higher concentration of calcium and oxalate in the urine and an increase chance for stones to form.

No one seemed to consider that an increase in almond consumption (or other foods high in oxalates) may be the culprit.

I dug in more and took a look to see if almond consumption was up in the United States. I found that the USDA calculates that almond consumption had doubled since 1994 and tripled since the 1970’s; with most people not eating almonds directly as I did, but in cereals, baked products and health bars. In other words many people are eating almonds and don’t even know they are.

While this was by no means a cause and effect relationship, things began to look quite suspicious. I came down with a calcium oxalate stone and the only risk I could find was that I ate a lot of almonds. Almonds contain the most important ingredient needed to form the most common type of kidney stone — oxalate. The prevalence of kidney stones has doubled since 1994 just as the consumption of almonds has doubled.

I then looked at how prevalent kidney stones might be in a country where, according to Dr. Oz, people grow up eating almonds. What I found was shocking!

According to a study published on kidney stone disease in Turkey (an updated epidemiological study. Eur Urol. 1991;20:200–203), the incidence of kidney stones in Turkey in 1989, was 11.8 %. This would suggest that the country which appears to embrace almond consumption from the earliest ages also has the highest rate of kidney stones.

So in conclusion, please consider that almonds are chock full of oxalates, the most important component of kidney stones. As the intake of almonds has increased in the United States, and several other countries, the prevalence of kidney stones has also increased. In Turkey, where it is customary for even young children to eat almonds, the prevalence of kidney stones may be the highest in the world.

Dr. Oz and others, who claim to be experts on health and diet, should be cautious when they suggest that their listeners, especially those who have a history of kidney stones, consume almonds as an ideal snack. Taking their advice might do more harm than good.

One has to wonder if the multi-billion dollar almond industry is aware that by hyping their product as a health conscious food, and without any warning of its potential risk, this huge and global industry could be contributing to thousands, perhaps millions, of their consumers developing renal stones.

My advice is to limit the quantity of almonds you eat and completely avoid them and other foods high in oxalates, if you have a history of calcium oxalate kidney stones. If the industry won’t add warnings voluntarily, I believe that it would be prudent for the FDA to require that a warning label be placed on packages of almonds noting that “increased consumption of almonds and other foods high in oxalates may significantly increase your risk of developing kidney stones.”

If you would like to find out more about which foods contain high levels of oxalates or how to reduce your risk of developing calcium oxalate kidney stones see the following links:

The Oxalate Content of Foods

National Kidney and Urologic Diseases Information Clearinghouse


Dr. Evan S. Levine is a cardiologist in New York and a clinical assistant professor of medicine at Montefiore Medical Center – Albert Einstein College of Medicine. He is also the author of the book What Your Doctor Won’t (or can’t) Tell You. He lives in Ridgefield with his wife and children.

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