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Saturday, November 30, 2013

Pros and Cons of a Daily Spinach Diet Update: the Bad News and the Good News

Why Test Oxalic Acid Levels?

This post is a follow up to the "Pros and Cons of a Daily Spinach Diet." You may wish to read it first for background.
In "Pros and Cons of a Daily Spinach Diet" posted on March 6, 2012, I reported concerns expressed by some health experts that a daily spinach diet can cause health problems--specifically the formation of kidney  stones. However other nutrition experts dispute and/or qualify the level of risk.

Are oxalate levels in blood and urine really something that we fresh spinach fans should worry about? Spinach is such an easy to prepare and great tasting meal, it would be disappointing to learn that it is a health hazard. Compared to lettuce, it has more texture crunch and a sort of sweet/sour flavor that makes it a meal worthy of the Spinach Queen and Popeye the Sailor Man. I decided to find out. Although I credit spinach for curing my Type II Diabetes, I surely didn't want kidney stones. So, after three uninterrupted years of daily spinach dinners (~1,075 meals in a row), I decided to conduct tests on my oxalate levels in a quasi quantifiable fashion. with the gracious assistance of Dr. Linda Lou and her assistant John Suwinski at the Emeline Clinic in Santa Cruz, CA, I initiated a 4 month investigation in which I served as a test subject.


The following describes an extreme exercise and diet regimen and test that works for me personally.  However, it may not be right for you. Please consult your physician.

Basic Oxalic Acid Chemistry

The biochemical reactions of urinary oxylate metabolism and test evaluation are quite complex, but the basic concept is that there are two sources of oxalic acid:
  1. Metabolic
  2. Dietary (in this case, spinach and Vitamin C)
Dietary oxalic acid that does not combine with calcium and  precipitate in the intestines is transferred into the urine for elmination. If the urinary  oxalic levels are high, it may promote the formation of kidney stones.

See my earlier post for three viewpoints about oxalates. Here is the link to Wikipedia.

Pre-Test Preparation
(All tests were conducted by Quest Diagnostics)

The "random test" that I employed requires the elmination of dietary Vitamin C for 24 hours and the "24 hour test" for 48 hours prior to urine sample collection.

For most people this is not that big a deal, but if you are also a fruitarian, as am I, then this eliminates fruit and cereals with Vitamin C tablet supplements for a period of 72 hours (48 hours pre-test and 24 hours during sample collection).

The importance of strict compliance with the pre-urine test protocol is summarized below.
Avoid vitamin C supplements and vitamin C-rich foods (eg, citrus fruits like oranges, orange juice; vegetables like broccoli, tomatoes, peppers, potatoes) for 48 hours prior to collection...Patient should refrain from eating chocolate, nuts, rhubarb, spinach, tea and vitamin C for 48 hours prior to collection.Source
Additional factors (including body size and the intakes of calcium, magnesium, vitamin C, and vitamin B6) may influence urinary oxalate excretion by modulating endogenous oxalate production (5,6) or intestinal oxalate absorption (10), but the importance of these factors is also unclear.Source

Following the New-Humans Health and Fitness Diet (which includes the daily consumption of spinach) will not induce abnormal levels of oxalic acid in the urine due to the ameliorating effects of dietary calcium supplements along with vinegar, tomatoes and avocados 


The contents of two 16 ounce Organic brand produce were consumed each week  In addition, I maintained an intake of supplements lacking Vitamin C as listed in our Diet Essentails Store.

Baby Spinach

Spring Mix

Three conditions were tested:

Control Spring Mix no baby spinach (three weeks prior)
Combo* 0% Spring Mix and 50% Baby Spinach (two weeks)
MaxSpin 100% baby spinach (two weeks)

*Spring Mix actually lists baby spinach as a component in addition to mixed greens and a variety of kinds of lettuce. However spinach was uncommon in the Spring Mix used in the test.

The experimental design is summarized in the following table. Click to enlarge.

Results and Conclusions

Test 1 Random
Result 49 mg/g which exceeded the range limit of 30 mg/g.

Test 1 and 2 were random tests, i.e.a single sample at a single time. The results greatly exceeded the maximum of 30 mg/g; There are several contributing factors. First a single specimen analysis obviously does not give an overall, average measurement. I collected both samples at noon and that might be a factor. In both of these tests, I only avoided Vitamin C supplements, but also consumed, tea, walnuts, fruit and juices—which I later learned need to ba avoided. See the chart for details.

Test 2 Random
Result 66 mg/g which greatly exceeded the range limit of 30 mg/g
The results of Test 2 were out of range due to the consumption of extra creatine which I mistakingly did not connect with oxalate levels.

Tests 3-5 were based upon the collection of all urine for a 24 hour period. The upper limit for 24 hour tests is 38 mg/24 hours.**

**Note, the Quest lab upper range limit for 24 hour oxalic acid is 38.0 mg while other testing services have an upper limit of 40.0 mg. In this analysis, the relative results are the key indicator of spinach consumpstion impact. " Stone formation risk probably depends more on absolute total oxalate excretion and concentration than on arbitrary normal values."

Test 3. Control (only Spring Mix with no spinach consumption for prior three weeks.
Result 36.1 mg After three years of daily spinach consumption, the level was still under the maximum of 38 mg.

Test 4. Combo (50% spinach, 50% spring mix)
Result 26.8 mg This was way beneath the control results and very unexpected. Perhaps the calcium, magnesium, potassium supplement that I take with spinach was in fact precipitating the oxalic acid into an oxalate with carbon? 

Test 5. MaxSpin
Result 49.4 mg
This was surprisingly high and not understood. Again the calcium supplement might be a factor. In this case, perhaps there was too much oxalate and the 500 mg of calcium carbonate was insufficient to bond with? Or maybe all of these tests should be regarded as inconclusive because there are so many complex, interrelated variables.  Plus with a sample size of one and a replicate number of one, random factors could definitely skew the results.

The Bad News and the Good News

I have now shifted from spinach only to a combination of Spring Mix and Baby Spinach for my daily salad. I still eat spinach every day, but have reduced my intake to one lb per week from two. And I feel more comfortable that my test results seem to wave the green flag on the Combo Special. I really didn't expect these results and am disappointed that my spinach-only-salad-days are over, but am also elated that I still get to enjoy my spinach every day!


I wish to extend my sincere gratitude to Dr. Linda Lou and John Suwinski and the many great support and staff workers at Emeline Clinic, County of Santa Cruz. I also wish to acknowledge the healing provided by Dr. Andrew Wu,  Dr. Jon Nordgaard, and Dr. Kathleen Halat of the Palo Alto Medical Foundation and Dr. Catherine Forest of UC San Francisco Medical Center for helping me conquer my diabetes and become a New-Human!

Here is a new article that you may wish to read.

Spinach Diet vs. Diabetes

What do you think?

Feel free to share your experiences Comments and Suggestions are welcome. There is no requirement for you to register. However, if you would like to be notified of new articles, please enter your e-mail address is box in the top right column.

Don't forget to add exercise to your health regiment. I heartily recommend the New-Humans Exercise Stick. I use mine every day, just like I eat spinach every day.

I have also selected some interesting spinach-related products at the top floor of our Amazon Store. And for a complete list of essential supplements check out our Diet Essentials store.

In my next article, "Cataracts and Contacts," I explore a whole new world of vision offered by artificial lenses.

Ron S. Nolan, Ph.D.

© 2012-14  Ron S. Nolan, Ph.D.
All Rights Reserved.


  1. Hmmm Interesting Data. I eat 1 bag of spinach PER DAY. I may need to reconsider that practice. Thanks!

  2. I forgot to mention that I stay well hydrated but whether that will lower the risk for kidney stones is unknown so....