Thursday, April 15, 2010

Copper in Food

Sources of Copper

It isn't hard to get enough copper-- unless you eat an industrial diet. I've compiled a chart showing the copper content of various refined and unrefined foods to illustrate the point. The left side shows industrial staple foods, while the right side shows whole foods. I've incorporated a few that would have been typical of Polynesian and Melanesian cultures apparently free of cardiovascular disease. The serving sizes are what one might reasonably eat at a meal: roughly 200 calories for grains, tubers and whole coconut; 1/4 pound for animal products; 1/2 teaspoon for salt; 1 cup for raw kale; 1 oz for sugar.

Note that beef liver is off the chart at 488 percent of the USDA recommended daily allowance. I don't know if you'd want to sit down and eat a quarter pound of beef liver, but you get the picture. Beef liver is nature's multivitamin: hands down the Most Nutritious Food in the World. That's because it acts as a storage depot for a number of important micronutrients, as well as being a biochemical factory that requires a large amount of B vitamins to function. You can see that muscle tissue isn't a great source of copper compared to other organs.

Beef liver is so full of micronutrients, it shouldn't be eaten every day. Think of it in terms of the composition of a cow's body. The edible carcass is mostly muscle, but a significant portion is liver. I think it makes sense to eat some form of liver about once per week.

Modern Agriculture Produces Micronutrient-poor Foods

The numbers in the graph above come from NutritionData, my main source of food nutrient composition. The problem with relying on this kind of information is it ignores the variability in micronutrient content due to plant strain, soil quality, et cetera.

The unfortunate fact is that micronutrient levels have declined substantially over the course of the 20th century, even in whole foods. Dr. Donald R. Davis has documented the substantial decline in copper and other micronutrients in American foods over the second half of the last century (1). An even more marked decrease has occurred in the UK (2), with similar trends worldwide. On average, the copper content of vegetables in the UK has declined 76 percent since 1940. Most of the decrease has taken place since 1978. Fruits are down 20 percent and meats are down 24 percent.

I find this extremely disturbing, as it will affect even people eating whole food diets. This is yet another reason to buy from artisanal producers, who are likely to use more traditional plant varieties and grow in richer soil. Grass-fed beef should be just as nutritious as it has always been. Some people may also wish to grow, hunt or fish their own food.


Scott Pierce said...

It would be interesting to see if CVD is relevant to copper concentration by region. Doesn't Argentina export a lot of copper? The assumption would be copper that can be mined also makes its way into the diet of those feeding in the region. It seems a given but you should never assume. Kind of like the previous post on the subject regarding copper in the blood.

Aaron Blaisdell said...

I wonder to what degree the copper in our modern plumbing enriches our drinking water?

John said...

"Some people may also wish to grow, hunt or fish their own food."

This may soon be the only option--unsettling...

Stephan Guyenet said...

Hi Rezzrov,

I agree it would be interesting. It's hard to get regional info on the copper content of foods though.

Hi Aaron,

Copper plumbing can be a problem actually, because it can put excessive copper in the water. Many nutrients have a U-shaped curve where too little is harmful and too much is also harmful, and copper is one of them.

Lutz said...

OTOH, our beef seems to contain sometimes too much copper. Reason enough for Mexican authorities to reject it.

Ruth Almon said...

Stephen, what about chicken liver? How does it measure up to beef liver, both in terms of copper and in general?

David said...

doesn't the liver also have a bunch of toxins?

Gabriella Kadar said...

Shhhhh, Stephan. You're going to create a run on beef liver! Prices will rise. Beef cattle have only one liver after all.

Chicken, pork, lamb, goat, turkey, duck.... all good livers. Excellent sources of nutrients.

Also kidneys are wonderful. Leopold Bloom ate a power breakfast when he prepared two fried lamb kidneys. He then ate a power lunch: liver with red wine.

Livers don't store waste. No parts of our bodies stores waste. For example kidneys smell like urine but that's not because they store the urine.


Doug Balch said...

Could I get an opinion about nutritional value of store bought conventional liverwurst spread. I don't find liver very tasty, but like liverwurst.

Unknown said...
This comment has been removed by the author.
Unknown said...

Just thought I'd share one of the least painful ways to get liver into your diet if, like me, you can't stand the taste and texture of it: Homemade paté.

Bacon, liver of various animals, chicken hearts and fried onions and mushrooms if you wish... cook/fry it all up, add whatever spicing you prefer (I like lots of pepper, but sage is yummy too), and purée.

I really loathe liver on its own. but like this, it is delicious.

Anna said...

I'll second the recommendation for paté. I'm still acquiring the taste for whole liver dishes, but I find a good liverwurst or paté quite enjoyable. And a little goes a long way. I haven't found any good liverwurst from supermarkets that I'd want to continually consume, but I hear US Wellness (grassfed meat online retailer) makes a good one (I plan to try it soon). I think a larger tube could be partially defrosted, cut into smaller amounts, then rewrapped and refrozen.

Some better food stores near me sell Marcel & Henry paté varieties (usually in the imported cheese section, not with the cold cuts). At holiday time, Trader Joe's stocks this brand paté, but at a much better price than the other stores. This year I bought a large supply for my spare freezer. About twice a month I get a package out to defrost - so far it is only my paté-loving husband and I eating it - can't tempt the 11 yo yet. I can't vouch for their pork source, but according to the website ( San Francisco-based Henri was French and his goal was to introduce and share good French charcuterie with Americans. He passed away just a few days ago, actually.

Cucumber slices, celery stalks, red pepper squares, sliced cheese, and rice crackers make great "transport" platforms for paté.

I've made rustic paté a few times and it isn't difficult (sort of like baking a cheesecake but without the crust), especially if you have a food processor. I especially like the River Cottage Meat cookbook recipe, though it makes far too much for our small family (but it freezes well).

zach said...

When I shoot a deer, I avoid the liver because the good old boys tell me that the deer get liver parasites from the swamps around here. Don't know if there's anything to it but it scares me.

Monica said...

Hi Stephan -- the second link to the UK study is broken.

Fascinating stuff.

The Pwnee said...

According to, sesame seeds have pretty high levels of copper as well.

It's also a good source of magnesium. I've had some success eating ground sesame to calm down my heart when I have bouts of tachycardia.

Sarah H. Wood said...

I don't know if this is exactly the right place to post this, but I have been trying to find any research/info on beef that has been grass-fed/pastured, but finished on grain at the end of its life. Everything I can find only compares 100% grass fed to feedlot 100% grain fed animals. Do you have any insights on the nutritional value of grain finished vs grass fed? (Of course there is a significant price difference and I am trying to figure out where I should spend my money.)
Thank you.

Monica said...

Wood, has a graph of some data about omega 3s and the decay rate in a feedlot. I believe it's under their "Health benefits" section.

As for other nutrients, I don't know.

Stephan Guyenet said...


Conventional beef typically spends the first half of its life on pasture and the second in a feedlot, so the comparisons between conventional and 100% grass-fed are the ones you want.

Monica said...


We have a local beef company that only finishes on grain for the last 3 weeks. But I live out west, where life is good. :) Most people don't have these options due to the shut-down of local slaughterhouses.

However, I still prefer grass-fed for the nutritional benefits and taste, so I source from a different local provider. Additionally, it's not any more expensive than the 3-week grain finished.


guyberliner said...

Several times over the years I've happened to stray onto the topic of liver, and how I found it completely unpalatable since childhood, and had someone reply knowingly, " had it OVERCOOKED."

Given my childhood aversion to it, I had never actually bought any and prepared it for myself. But I became intrigued by these comments, and also by all the suggestions I've seen that I was missing out on one of the most nutritious foods you can get.

So I decided a few months ago to test this theory. I bought elk liver at my farmer's market, and per recommendations, cooked it only until it was still a little pink inside, constantly checking.

As I had it cut into many pieces, I noticed that, as they reached doneness, some of the more cooked pieces of liver were starting to take on the classic unpalatable flavor and aroma of liver that I always detested as a child. I stopped right away and took the pan off the stove.

I discovered, happily, that those knowing comments were right! All these years, I had hated liver only because I'd never experienced it prepared PROPERLY. I was able to salvage most of the pan and enjoyed an excellent homemade dish of grilled liver and onions for the first time in my life.

Anonymous said...


I believe the data you posted on the copper content of various foods is based on a recommended daily intake (RDI) of copper of 2 mg/day which is based on the RDA from 1968. Similarly, the RDA for vitamin A is 3000 IU per day.

Newer RDIs have since been introduced in the Daily Reference Intake (DRI) system, but old RDIs are still used for nutritional labels. Under the newer DRI system, the recommended daily intake is 0.9 mg/day for copper and 900 IU/day for vitamin A.

I bring up vitamin A because liver is very high in vitamin A, among other things, and because of previous discussions related to vitamin D about the toxicity of vitamin A (according to the Vitamin D Council). Under the newer DRI system, what was once the recommended daily amount of vitamin A of 3000 IU/day has become the "upper limit" of daily intake, and the recommended daily intake has been reduced by 70% (from 3000 to 900 IU/day. Vitamin A has indeed dropped out of style.

Returning to the subject of liver, a website of the Department of Agriculture lists the copper content of beef liver as 14.3 mg per 100 grams which equates to 16.2 mg per 4 ounces, or 800% of daily copper requirements based on the old RDA of 2 mg/day, and 1800% of daily requirements based on the newer RDA of 0.9 mg/day.

There is a small restaurant in town, Julwin's, which serves lunch menu item with very generous portion of liver, probably at least 8 ounces. We generally don't eat it all in one sitting, but take the leftover liver home and finish it that evening, so we are getting between 1600% and 3600% of the recommended daily intake of copper in one sitting.

Liver is sold in one pound packages, so when we eat liver at home my wife and I usually finish the one pound package in a day, so that equates to about 8 ounces each.

And the vitamin A content!!! The data shows that beef liver has 36000 IU of vitamin A per 4 ounces, or 72,000 IU per 8 ounces, so, according to Dr. Cannell, we are getting 8000% of our daily requirement (900 IU/day) of vitamin A. If Dr. Cannell were right about the toxicity of vitamin A, I think my liver would have exploded by now. According to WAPF guidelines which recommend 10,000 IU per day (more than 3 times the current "upper limit"), an 8 ounce chunk of liver would be about right if eaten once a week.

To be honest I have questions about the USDA data on the copper content of beef liver, for it shows the copper content to be three times the zinc content, whereas in pork liver and chicken liver, zinc content is 6 to 8 times copper content. ??

Porcupine: Chicken liver copper content is shown as 0.5 mg/100 grams which equals 1.1 mg/8 ounces.

dextery said...

Liver was never my thing, but for nutrition sakes, I have been having beef liver twice a month pan fried in coconut oil and butter with a sprinkling of thyme and basil and garlic powder. I cook beef heart the same way....and both cook rare. Delicious.

I know most of us are paleo eaters here, but seeing buckwheat on the list of foods containing copper ,
lest anyone seeing your chart and would want to get their copper from eating or juicing buckwheat sprouts. DON'T

They are toxic and brings on the condition known as fagopyrism..."When ingested in sufficient quantity, fagopyrin is known to cause the skin of animals and people to become phototoxic, which is to say hypersensitive to sunlight." Bad rashes and burning sensation on the skin when exposed to sunlight.

Another reason not to be a "healthy" vegan.

Gabriella Kadar said...

Strangely enough, based on other people's comments around here, I've always loved liver all my life. I don't care if it's tough as leather, over cooked, undercooked or pink inside. I love the stuff.

Once per month I buy 1 kilogram hunks, peel and slice thinly. I'll sautee slices for breakfast, make them into a curry for lunch and stir fry with vegetables for supper. I consume half over three days and freeze the other half for the following week.

My kids love liver too.

There's nothing wrong with consuming foods that have strong flavours.

This 'bland tastebuds' business appears to be right across the board. North Americans prefer bottled water that is as close to distilled water as possible. Meanwhile the whole point of consuming special waters was because they contained high concentrations of various minerals like magnesium, potassium, and, yes, even sodium.

The appetite for flavour free is alarming. To say 'tasteless' is grammatically incorrect. Flavourless is more accurate.

Quite frankly, so long as most people dislike liver, kidneys and other 'offal', I'm very happy. I can make exceptionally nutritious and flavoursome meals for very little money.

Ruth Almon said...

Isn't RDA or RDI (or whatever other letters are used) a bit of a convenient fiction?

Common sense leads me to believe that the optimal amounts of any vitamin and mineral must vary greatly from person to person, depending on their sex, age, weight, genetics, activity level, the climate they live in, their health status, their current nutritional status, and so on.

Jack, back when people had to hunt or harvest their own food, they couldn't have had the variety on a daily basis that we have today. When something became available, they ate it, and then didn't have it again until next season, or next time they caught it. Therefore, (again, this is just my common sense, not based on research) I don't think the body expects to get an X amount of nutrient Y per day. I think the body must relate to the big picture of getting enough vitamins and minerals in general.


Jack, thanks for the liver info!

Ned Kock said...

Thanks for the post Stephan.

I would argue that the problem with eating beef liver too often (once a week sounds very reasonable) is not necessarily related to the high micronutrient content, but specifically to the high fat-soluble micronutrient content. Fat-soluble micronutrients (e.g., vitamin A) accumulate in fat tissue, to be point of becoming toxic over time.

JonathanC said...

Is there a test I can have done to accurately measure my copper levels? I have supplemented zinc almost my entire life and I'm a bit worried that that could have interfered with my copper levels. When I have a blood test my copper levels are usually within the normal range but because I have CF my c-reactive protein is usually high.

- Jono

Barkeater said...

According to this website, copper sufficiency needs to be considered with chromium and other minerals.

Based on blood test results viewed over the years (apparently, an intra-cellular assay of minerals), the problem is less one of copper deficiency than one of chromium or other deficiencies. I am not endorsing this view, but offer it up as an interesting contrast with the simpler view that our nutritional consumption of copper may be deficient.

I am very interested in the question of nutritional "holes" that are causing heart disease and other diseases of civilization, as I don't believe they have had the same degree of study as pharmaceutical "deficiencies." Besides, if corrections to nutrition are done right, they should have no adverse side effects, even if they turn out not to fix problems to the degree I hope.

Stephan Guyenet said...

Hi Jack,

You're right about the values I posted for copper-- thanks for pointing that out.

Hi Jonathan,

I believe the most accurate test
(without taking a liver biopsy) is 24 hour urine copper excretion. I don't think you can get it at the doctor's office though. I think most people are stuck with guesswork, because the blood test is essentially meaningless except in cases of gross deficiency. And yes, zinc intake can interfere with copper absorption.

Robert Martini said...


I had a question for you regarding omega 3 and omega 6 fatty acids. What's important to good diet and health, is it the RATIO of omega 3/omega 6 or is the ABSOLUTE amount of omega3 and omega 6 what matters?

JBG said...
This comment has been removed by the author.
JLL said...

I get a lot of copper from dark chocolate. In fact, I've been wondering if I get too much of it. I've yet to read the studies on copper to see what amount would be optimal.

What's your take on the importance of the copper/zinc ratio?


Anonymous said...

Jonathan C.

Regarding the question of zinc supplements interfering with copper absorption, it appears that no interference occurs at the "upper limit" zinc dose of 40 mg/day.

Zinc supplements of over 50 mg per day result in a decline of HDL-cholesterol and therefore adversely effect CHD risk. (See pubmend 16943449: free full text)

Low zinc intake also impairs copper absorption according to a study which found that copper absorption was 38% of intake when zinc intake was 5.5 mg/day compared to 48% when zinc intake was 15.5 mg/day. (See pubmed 2484367)

When copper intake is low, absorption efficiency increases and copper excretion decreases. When copper intake is high, absorption efficiency decreases and copper excretion increases, so the body can handle a range of copper intake. While the Upper Limit for copper intake is 10 mg/day, it has been found that when intake is continuously above 7 mg/day, body copper levels continue to increase, so the body can not handle continuous copper intake of 7 mg/day. (See pubmed 15817858: free full text.)

Paul Ericson said...

All this talk of liver is making me hungry!

As for the flavor of liver, it can be divided into two basic types:
1. Bitter
2. Sweet

Beef liver is sweet.

Bitter livers are from animals that lack a gall bladder and thus store bile in the liver instead.

Traditional hunters knew which livers were sweet and which bitter and only ate the bitter livers as a last resort.

David said...


Do you know if grass-fed bison liver is basically nutritionally equivalent to grass-fed beef liver? I can't imagine why they would be that different, but I wanted to be sure, and that info is hard to come by. I found a good local source of grass-fed bison and your post here got me thinking that I should get more liver into my diet again.


Anonymous said...

Hello Stephan, there is a problem eating an ounce of lamb liver every day? i eat 13x2 grams a day (frozen and vaporized, two meals) i need be sure that all my nutrients are above 200% of RDA but not more for more safe, i thing that if there is a safe limit in a week , i would like divide this quantity by 7 days, i think that for me this is better than eating 7 ounces of liver one day in a week, one reason is that i find his taste repulsive,and because i think that is more optimal give to the body all they need all days, (I know that fat soluble vitamins not need to be taken all days but that doesn´t mean that you can skip a day, that is, if you eat only 50% of retinol daily in a week, at least one day must be 400% of retinol, i know that we are adapted to tolerate infrequent micro an macronutrient ratios, but adapted doesn`t mean that this is the optimal thing to do, i never go above 300% of retinol daily, i think that this is better that take multivitamin suplement
Ned Kock i read the tolerable upper intake limit of all fat soluble vitamins, only vitamin A seems to be a problem, for the others there is a huge margin in general, except for synthetic versions
any way body is very very efficient treats with exceed of micronutrients, what i want to say is that is a problem of relatively small importance (in general) compared to all pollutants nowadays.
Stephan Thanks for your valuable information in your blog
I keep reading it