LISTS – AND LISTS
I know you are all looking for THE list. Here is one from a reliable source. We have downloaded one version on their site to a separate document so it opens with one click a useful table of oxalate foods. Get yourself acquainted with it. It will tell you much of what you need to know. A lot of it will even surprise you. You are not as restricted as you think you are or as you have been told.
A more dramatic list is the 180 high oxalate foods distilled out of the big list. Here are culprits! Not on this list? Probably not very high in oxalate so far as we know – with perhaps a few exceptions. Note that quantity is critical. For example black pepper is high in oxalate but the amounts used are small enough that total oxalate intake from it is negligible.
The reliable source, as it turns out, needed some updating. Dr Ross Holmes, professor, School of Medicine, University of Alabama, was kind enough to review the work of Dr. Michael Liebman who is a professor of Human Nutrition and Food Option at University of Wyoming and determine which food entries on the Harvard list needed changing. We cannot change the original but we have updated our lists accordingly and annotated updates with *** marks. So the lists here are the most recently edited available at present.
I have created a graph for this article. Of the 180 high oxalate foods really only a fraction are really high, and it is these you need to worry about. So here they are: These are the foods that can add up. The graph shows mg of oxalate in a common portion. The details of the portion are in the list.
Note how about 45 or so mg/serving the bars become repetitive, and the real action is above that point. Focus on the really high foods – they are easy to spot on this graph. Serving sizes for most of these items are one cup – for cooked spinach 1/2 cup, for almonds one ounce. Some names are truncated, but it should be obvious what they are; if in doubt just check the list.
Medical research is endlessly argumentative, and food oxalate is no exception. A recent paper contrasts findings from 6 websites and 2 applications and finds some wide variations. Because the results are hard to get from PubMed I have uploaded a PDF for you. It will open as a Google Document. Of the sites, the Harvard site -used here as our reference, and the Wake Forest site – which is a legacy of an outstanding investigative group have most standing with me. Leaf through the comparisons between them in the 4 charts and in the large table at the very end. On the whole differences are modest. The hyperoxaluria and oxalosis list from the paper has been withdrawn from their site.
DO YOU NEED A LIST?
Many of you leave the doctor’s office thinking you will never be able to eat a fruit or vegetable again. If that wasn’t bad enough chocolate and nuts are gone, too. Some of this sadly is true, most of it is not. I am here to bring you good news: Almost everything, high oxalate or not, can be incorporated into your diet safely.
Do you need a low oxalate diet? You may if your stones contain calcium oxalate crystals and your urine oxalate is high enough to pose risk.
If you do need a low oxalate diet, what is your goal? Less than 100 mg of diet oxalate is good; less than 50 mg is ideal.
If you want to read some of the science about urine oxalate and risk of stones and about how we get to the diet oxalate goals, it is summarized at the end of this article.
Here we assume you do need to lower the oxalate in your diet.
Low calcium diets can raise urine oxalate, and the solution may be as simple as a proper calcium intake. There is every reason for stone formers to eat 1000 mg of calcium daily to protect their bones. The common hypercalciuria of calcium stone formers puts bones at special risk when diet calcium is low.
Before changing your whole life around, ask yourself if you are avoiding calcium foods. If so, add them back and ask your doctor to check your urine oxalate again. It may fall enough that a low oxalate diet is not necessary.
If low calcium intake is not your problem, and you need a low oxalate diet, here is my take on how to do it.
WHAT IS THE DIET OXALATE GOAL?
Typical diets contain upward of 200 – 300 mg of oxalate. For stone prevention, a reasonable goal is below 100 mg of oxalate daily. An ideal would be about 50 mg daily if that can be accomplished.
To get there, consider the oxalate contents in common serving portions of all of the foods, and make up a plan for yourself.
Everyone who comes to me is very unhappy thinking they can never have a berry again. This is Baloney. The only berry that is very high in oxalate is raspberries (look at the list). On the other hand, people do not realize avocado, oranges, dates, and even grapefruit and kiwi are very high and need caution.
This doesn’t mean you can never have these healthy treats. If you incorporate any of these high oxalate fruits into your morning yogurt you can reduce some of the effects of the oxalate content.
Also look at your portion sizes. You really cannot eat a lot at any one time. Dates are not a good bargain: One date is 24 mg!
CANNED OR DRIED
Canned pineapple is a problem.
Dried fruits have to be a worry because the water is taken out, so a ‘portion’ of dried fruit can be gigantic in oxalate content. Figs, pineapple and prunes are standouts. Just think: 1/2 cup of dried pineapple is 30 mg – not a lot of fruit for a lot of oxalate. If you want dried fruit, think about apples, apricots, and cranberry as lower oxalate options.
Spinach and rhubarb are standouts; stay away.
Other vegetables you need to be aware of are tomato sauce, turnips, okra, and yams (sweet potatoes) along with beans of different sorts.
I am not in the business of taking healthy foods away from people. But in the cases above you really must limit; there is just too much oxalate and these foods do not pair well with high calcium foods the way fruits can be mixed right into your yogurt or cereal and milk.
Many of you have been told to stay away from all green leafy vegetables. This is not true. Look at the list. There are plenty of salad options still available for you including kale. Even though tomato sauce is high in oxalate (see below) that is because of concentration. A whole medium tomato is only 7 mg and who eats more than one at a time?
Many of the salad vegetables are so low in oxalate they are freebies. Eat what you want.
These are Trouble! I put them into their own separate group even though they are vegetables.
From french fries to baked potatoes they are very high oxalate items. One ounce of potato chips has 21 mg of oxalate and who eats one ounce? Not I. Baked potatoes are terrible. One comes in at just under 100 mg of oxalate. Mixing sour cream into the potato will not help much; one tablespoon of sour cream contains only 14 mg of calcium. One ounce of cheddar cheese contains 200 mg of calcium, which could help, but it increases calories, salt and fat. But all in all, why struggle so hard? Potatoes are not ideal for stone formers.
They have no oxalate. They are your main source of calcium. Use them. They can add a lot of salt – cheeses – and can be caloric. But they reduce oxalate absorption and preserve your bones.
For a stone former who has to watch salt intake, increase calcium intake, and lower oxalate intake, here is how to do that. You cannot have as much cheese as you want because of the salt. So portion sizes are very important. Yogurt, milk, even ice cream are good bargains – modest sodium and high calcium. These are a great place to add in a wee bit of chocolate – high oxalate foods – for those of you who cannot live without these high oxalate treats.
BREADS AND GRAINS
Some of the basic ingredients to make these foods are very high. White flour and brown rice flour are high in oxalate so everything you make from them will be high.
Even so, as far as kidney stones go, breads are mainly alright because of portion size: not that much flour so one slice is 5-8 mg. French toast and New York style bagels top the list at 13 mg for two slices and 40 mg for one bagel – as much as anyone will eat of either food.
PASTA RICE AND GRAINS
Spaghetti, one cup cooked is 11 mg and most of us eat more than one cup.
Buckwheat groats, one cup cooked is 133 mg – I don’t see many of you saying ‘darn it’ or taking to your bed, but beware. Millet and bulger, wheat berries, rice bran, corn grits, and corn meal, these are widely used and are high. If you are using these, be thoughtful.
Here are some low oxalate options in this category: White rice, hummus, corn flour, corn bran, flax seed, and oat bran are popular and safe.
Since oxalate is only found in plant foods, all the meats are safe. Fish, too.
For our vegetarian friends, tofu and veggie burgers are very high.
NUTS AND SEEDS
These are just dangerous for two reasons.
Obviously they are very high in oxalate.
Secondly, I don’t know anybody who just has a few nuts at a time.
Just like chips no one eats one – the whole jar is more like it.
But, for one cup of pumpkin sunflower or flax seeds the highest is only 17 mg of oxalate and none for flax. For those of you who love foods in this category seeds are the better choice and they can be sprinkled on yogurt and ice cream.
I have good news for my chocolate lovers. I know most of you have been sent home with a list and chocolate is high on it. But if you look at the numbers nuts are a lot worse than chocolate. Chocolate can be mixed in with dairy products, too, so as to reduce oxalate absorption.
Even so I do want to point out that half a brownie is on the high side, and who eats one half?
You can still satisfy your sugar craving but pay attention to your portion size.
Keep in mind, however, that sugar loads increase urine calcium loss which increases stone risk, so there are two reasons why this food group can be a problem.
But even without chocolate, you eat a lot of flour when you eat a piece of cake, so cake can be a problem – about 15 mg per piece, like french toast. Pies are half the risk because of their fillings – unless they are chocolate pies!
CRACKERS AND CHIPS
The big enemy here is potato chips. A one ounce serving contains a whopping 21 mg of oxalate. I repeat: A one ounce serving.
Your best bet in this category if you’re looking for something crunchy is corn chips – one ounce is 7 mg, popcorn – one cup is 5 mg, and pretzels, one ounce is 5 mg.
Crackers are OK mainly because they are small and the amount of flour is not that much.
Hot chocolate is the clear loser at 65 mg per cup; carrot juice is the runner up at 27 mg per one cup. Lemonade, tea, tomato juices, rice dream and the like are better but still high. The are 15 – 18 mg per serving. Lemonade – frozen concentrate – is 16 mg per 8 ounces so be careful about this as a source of citrate.
Soy milk, for those of you who prefer it, is not a good option. It is very high at 20 mg per cup. We have no data from standard sources for rice milk, cashew milk, and coconut milk; almonds are high in oxalate so the almond milk product will certainly be high.
Tea is so commonly used, here are the details. If you brew your own tea it is high in oxalate. The longer you steep your tea, the more oxalate it will have in it. If you use a sweetened instant iced tea one cup has 0 mg of oxalate.
Here are some juices that are low in oxalate and better substitutes: Apple juice, apricot juice, orange juice, grapefruit juice, grape juice. For all the lemonade drinkers, diet lemonade is low in oxalate.
Here is something very important: Coffee is oxalate free – almost, 1 mg for a cup (2 mg/cup for decaf). We already told you that coffee drinkers have a reduced stone risk, so lets debunk the coffee myth here: Drink it as you wish.
Everything is good except chocolate milk. Even that is only 7 mg a cup for a sweet treat here and there.
What tops the list in this category is a can of beer: 4 mg of oxalate. All the rest are low and, frankly, the oxalate in a can of beer comes with a lot of fluid. This is not the problem area for stone formers.
If I didn’t say this to you I could not sleep well tonight. Water is the clear winner in this whole category. It is free of calories, sugar, and oxalate. Please use it as your main beverage and supplement with the items above.
SPREADS AND SAUCES
Chocolate, miso, peanut butter, and tahini are all high.
Miso soups is extremely high – 111 mg/cup. Lentil soup is high, and so is clam chowder – the potatoes.
This is a dangerous meal if you are a cereal lover. Many cereals are high in oxalate. I am afraid you need to look them up in the list by brand. Unfortunately the healthier cereals are highest in oxalate because they contain more plant based ingredients. Probably having milk in your cereal is wise, but we have no data to show.
HOW DO WE MANAGE ALL THIS?
The first thing you need to do is to learn and remember what are the highest oxalate foods and beverages. Without this in mind it is impossible to shop and cook intelligently. Here is a short list of the highest oxalate foods all in one place.
For those of you who love cereal because it is quick and easy check out the list and see if the one you love is high in oxalate. If it is, choose the next best one with lower oxalate. Put milk in the cereal.
Alternatives to cereal that are also quick and easy: Yogurt or cottage cheese and fruit. The only fruits to worry about are raspberries because no one puts oranges on their yogurt. Bananas, peaches, blueberries and strawberries are perfect toppings.
More trouble, but no oxalate, eggs any way at all. Boil a batch on Sunday and have them for the week for breakfast, and snacks, too.
Your breakfast coffee is free and so is your water. For juices use orange, apple, pineapple, grapefruit – all great. If you want tea, don’t steep more than a minute and consider adding milk to it. Green tea is better than black.
Typically you are grabbing a salad or a sandwich for lunch, so what now? Many clients tell me they no longer eat salads because their physicians told them to stop all green leafy vegetables.
I’m bringing salads back to you.
Arugula, iceberg, romaine lettuces, and kale, are fine as your base. Stay away from spinach. Here are good toppings. Cauliflower, corn, cucumber, mushrooms, onions, peas, scallions, squash and zucchini are all fine. Tomatoes are fine, too; it is only the sauce that is high. Broccoli and green pepper are moderately high so watch the portion size.
Sandwiches will cost you between 12 and 16 mg of oxalate depending on the bread you are using – 2 slices. This doesn’t mean you can never have a sandwich, it just means you have to keep track of how much. You can have 50 to 100 mg daily. What goes inside between the two slices of bread is usually cheeses and meats which are oxalate free. So sandwiches are not something to be afraid of.
Beef, chicken and fish are all fine, and those the main courses for most of us. You will run into problems if you are a pasta or potato eater. If you are you need to limit the amount of times you have these foods each week and also the quantity each time you use them. Substitutes are a problem: White rice is a nice substitute for potatoes but there are few others. It is more veggies that have to fill in – very healthy but not as much fun.
Here is a recipe for cauliflower – ‘mashed potatoes’ you will like and even think, sometimes, is the real thing. There are many versions on the web, choose the one that makes you happy but be careful about the ingredients.
There is also quinoa which is not on our lists, but may well be high. A recent scientific article on this plant does not give oxalate contents which suggests they are not reliably known.
I have recently put together a private FB page called THE Kidney Stone Diet. It is a group that helps educate you on your physician prescribed treatment plans. As you can imagine, oxalate comes up in many posts. I moderate it to keep it clinically sound. Come on over and join the discussion!
URINE OXALATE AND RISK OF KIDNEY STONES
I promised you some science – here it is for those interested. It concerns only highlights from the food – urine oxalate research recently performed and seemingly germane to the problem of how stone formers should control oxalate intake.
The most useful data about urine oxalate we have so far is from three cohorts studied by Dr. Gary Curhan. Two are cohorts of nurses one a cohort of physicians. These people have kept track of many aspects of diet and health for decades, and among their records are onset of kidney stones.
As he did for urine calcium, Curhan measured urine oxalate in properly selected subgroups from each cohort, including people who did and did not begin forming stones. From these samples he could calculate the relative risk of new onset of stones in relation to 24 hour urine oxalate excretion.
The two nurse cohorts are red, the physicians – all men – are blue. The dotted line at 1 is the risk threshold: Above that line, risk is present.
The top of each crosshatched bar shows the mean relative risk for each of the five urine oxalate ranges. Clearly the mean goes up as urine oxalate goes up.
But the mean relative risk has a range of uncertainty around it. The bottom of the solid portion of each bar is the lower 95th percentile for that range of uncertainty. When that bottom lies above 1, risk is very likely to be present.
For both the women and men groups, that point is reached between 25 and 30 mg of urine oxalate a day. Therefore one wants to try to get urine oxalate below 30 mg daily and even lower, below 25 mg daily if possible. The average urine oxalate excretion among the women in this study was close – 26 and 28 mg/day for those who did not form stones and just a bit higher for those who did – 28 and 30 mg per day. The men are a problem: 39 and 41 mg/day for those who did not and those who did form stones.
This is not diet oxalate, it is urine oxalate. Urine oxalate is how much the body makes and how much is absorbed from foods. Mostly, we can control only the second part – how much is in the food.
HOW MUCH DIET OXALATE DAILY
All dietary advice depends on having a reasonable goal in mind for oxalate intake. My goal of 50 – 100 mg of oxalate from food daily is not unreasonable given the research that has been done in normal people and stone formers.
Holmes and colleagues found a urine excretion of oxalate of about 10 mg/gm urine creatinine in normal people eating a synthetic oxalate free high calcium diet (graph at left). As diet oxalate increased, urine oxalate rose from 0 to 10 mg/2500 kcal/d, urine oxalate rose steeply from 10 to 14 mg/gm urine creatinine. It rose more slowly, from 14 to barely 15 mg/gm urine creatinine as diet oxalate was increased to 50 mg/2500 kcal/d, and more or less at the same slope thereafter so that an increase from 50 mg/2500 kcal/d up to 250 mg/2500 kcal/d increased urine oxalate only from 14 to 18. The closed symbols are whole food the open symbols synthetic diets.
From this work the percent oxalate absorption could be calculated as around 10 – 15% and the contribution of diet oxalate to urine oxalate excretion as around 25 – 40% when intake of oxalate was between 50 and 350 mg/2500 kcal. Therefore one can consider a whole food 1000 mg calcium 50 mg oxalate as a usable low oxalate diet, and a 150 – 250 mg oxalate diet as relatively high.
The balance between diet calcium and diet oxalate does not matter greatly if diet calcium is high. Among normal men and women eating 1000 mg/day of calcium and 750 mg/day of food oxalate, 24 hour urine calcium was about 110 mg/day and oxalate about 44 mg/day.
If the calcium oxalate balance is altered so calcium intake is 400 mg and 20 mg of oxalate at breakfast and lunch, and 200 mg of calcium and 710 mg of oxalate at dinner, as compared with simply 333 mg of calcium and 250 mg of oxalate in all 3 daily meals, urine oxalate is lower after the high calcium low oxalate meals, but only slightly higher after the high oxalate low calcium evening meal than when calcium and oxalate intakes were balanced. This means that when diet calcium is at least 1000 mg daily the balance of calcium to oxalate within any one meal is not likely to affect stone risk.
Seiner and colleagues make clear that stone formers are different from normal people. They divided male and female stone formers into 2 groups of 93 people each, one with urine oxalate above 0.5 mmol (~50 mg) of urine oxalate daily and the other with urine oxalate below 0.4 mmol (~40 mg) daily. They found virtually identical calcium and oxalate intakes: 845 vs. 812 calcium and 101 vs. 130 mg daily of oxalate respectively in the lower and higher urine oxalate groups. But the below 0.4 mmol group excreted only 27 mg of oxalate daily on average, whereas the high oxalate group excreted 64 mg daily. In other words diet was not responsible for the higher urine oxalate excretion, suggesting a difference of oxalate absorption. Those prone to high oxalate excretion seem, therefore, to most need diet modification.
Knight and colleagues found a wide range of oxalate absorption among 38 calcium oxalate stone formers eating a self choice diet. Urine oxalate excretion (vertical axis) varied with percent of diet oxalate absorbed (horizontal axis). The mean absorption centered around 5%; a few outliers absorbed over 15% up to 25%. This supports what Seiner found – some stone formers will have urine oxalate levels very responsive to diet oxalate and sans a research protocol we will not know. This is another good reason to keep diet oxalate low – 50 to 100 mg if possible.
PROTEIN AND GELATIN
Diet protein intake does not affect urine oxalate excretion. In 11 normal people fed a 1000 mg calcium, 51 mg oxalate, 3000 mg sodium fixed diet, varying protein intake from 0.6 to 1.6 gm/kg/day – a very wide range – did not alter urine oxalate appreciably (mean values were 23, 23, and 25 mg daily for the three protein intakes) even though oxalate precursors like glycolate rose markedly (25, 22, and 46, mg daily).
Jello is a source of hydroxyproline which converts to glycolate and oxalate, and oral loading with gelatin can raise urine oxalate. Ten normal people eating a 1000 mg calcium, 150 mg oxalate diet (typical normal level) were fed supplemental gelatin as one quarter of daily protein intake. Urine oxalate was 24 mg daily vs. 17 mg daily when the same diet was supplemented with whey protein – containing little hydroxyproline – as a control. So lots of jello is not an ideal plan for stone formers.
Where does this leave us about how much oxalate is alright for a day. If diet calcium is high, as it should be, at about 1000 mg, then one should try to limit diet oxalate below 100 and even to 50 mg daily. Perhaps this is most important in those patients whose baseline oxalate excretions are higher – in the range of above 40 mg daily.