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Warning: Almonds May Be Dangerous To Your Health!

June 21, 2012

Be Warned: Many Dangerous Foods Lack Warning Labels

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 2 million outpatient visits resulted in a primary diagnosis of kidney stones.   While there are several types of stones, the majority of them, over 80 percent, 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 U.S.

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 ten years: the incidence is about 1 in 11 people in the USA 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 US. 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 Connecticut with his wife and children.



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7 Responses to Warning: Almonds May Be Dangerous To Your Health!

  1. John Alkalizer on April 15, 2015 at 7:38 pm

    I am very passionate about this subject matter especially since I just passed a kidney stone a few months ago. Also I believe in eating more alkaline (greens) but haven’t been faithful to it because the oxalates scares me. But it is important to note that during a six month period leading up to my kidney stone I switched from coffee to tea drinking at least 2 16oz mugs every morning (gourmet loose-leaf black tea). I’m begining to believe that the TEA has been a major contributor to the stone. But I’ve also read that if you eat or drink calcium rich foods when consuming foods and drink with high oxalic acid content the oxalate ions and calcium ions will bind in the stomach first thus prevent the binding of the two substances in the kidneys therefore preventing risk of kidney stones. There are so many variables it makes my head spin. But at least stay away from TEA even Ice Tea and drink at least 10 cups of water a day if prone to kidney stones.
    Also to prevent iron deficiency oxalate rich foods should be eaten with foods that contain vitamin C http://www.popsugar.com/fitness/What-Causes-Spinach-Teeth-551249

  2. D Rancher on December 16, 2014 at 2:21 pm

    I started eating about an ounce of almonds daily for the health benefits. I gradually started grabbing a handful when hunger pangs arose. Several months later I was consuming 4 or 5 ounces daily. Then kidney stones started arising, 5 stones in a month, from both kidneys. My urologist said in 30 years I was the first case he had seen where both kidneys produced multiple stones within a month. The one and only change I made to my diet was to eliminate the almonds. A year later and I’ve had no reoccurrence. There’s not the slightest doubt in my mind that almonds caused my kidney stones.

  3. Rune Madsen on June 14, 2014 at 3:09 pm

    I see a smidgen of correlation, but really no causation at all. I see you referring to one study in Journal of Urology about almond-oxalate. Only one? Really? Not even two? No meta studies? Cross studies? Anything? No? As a physician, you should know that that is a very spurious platform to build your argument on.

    Your Turkey argument is also woefully overblown. You put the number of kidney stone sufferers in USA as 1/11 = 9.09%. Turkey you tell us is at 11.8%. Now, allow me to become a bit speculative, as I have done zero research before commenting. But for those two numbers to make any sense i regards to almonds, we need to know the average pr. capita intake of almonds is. We also need to adjust for the sickness profile for each country, where I will posit that, though your American healthcare system is woefully inferior to European style socialized medicine (just look at what this adventure cost you, it would have cost me nothing), the sickness profile will probably fall in the favour of USA*.

    You mention yourself that living in a warmer climate leads to higher susceptibility of producing kidney stones. How about adjusting for this in your comparison of the two raw numbers. Maybe a comparison of states within the US that has comparable climates would be much more relevant than a country wide statistic. Just a thought.

    Then there is a rather key piece of data you don’t even touch upon. What’s the average intake of almonds in Turkey and USA pr. capita?

    You should know all of this. You have had classes on statistics as part of your training. You scaremongering like this is unbecoming and unfitting of your profession.

    *Due to larger disparities between level of health´care from affluent urban to poor rural areas in Turkey.

    • heartdude on June 18, 2014 at 3:08 pm


      you make some points here, albeit with more animus than merit. Are you aware that numerous stuidies show that oxalate consumption should be avoided in patients with calcium stones? This is my observation, not my personal blinded study which I could not perform. I suspect that if we had labels on high oxalate foods that patients with risk of stone formation might avoid consumption and we could reduce the risk of this disease. Sorry you seem upset with my observation. I think there’s a lot more credible reasons to be upset about. Steve H got it right.

  4. SteveH on November 5, 2013 at 6:39 am

    You can pig out on pizza, chili dogs, or what have you, with maybe a little indigestion. But with almonds, you can end up in a hell of a lot of pain in the hospital. That’s the take away. It happened to one of my best friends.

  5. Meg VaVoom O'Malia on November 4, 2013 at 4:07 pm

    What I’m taking from this article: don’t eat 3 or more packages of almonds in one sitting. Like, duh. Limit your intake, as with ANY OTHER FOOD.

  6. jamesc on March 21, 2013 at 1:05 pm

    I thought it might be useful to know that oxalates increase iron absorption and magnesium elimination. So while having excess oxalates in the kidney is certainly bad and can cause stones, it’s important to note that an iron deficiency (often associated with tea drinkers) can cause excess free oxalate ions to build up in the kidney. The oxalates then bind to calcium forming stones. so it’s important to get plenty of iron with oxalates and not have an iron deficiency.

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