If you want to use Spinach for Iron, that’s probably not a good choice. In fact, it’s a downright bad choice. Despite most vegan and vegetarian websites touting its high iron content, spinach for iron is simply a complete myth that I’m busting right here and right now with the science and not a bias towards one way of eating or another, like many of the sites touting spinach for iron.
We’re Not Biased, We Just Want to Absorb Iron!
It’s true that spinach has a high iron content, but anyone writing a blog post about spinach for iron should at least have looked into whether that iron is available to the body for absorption. Sadly, almost none of the vegetarian-touting websites do this, even the ones written by people who are well-educated and should know better.
The blog post entitled Top 10 Foods Highest in Iron does state that heme iron is better absorbed, but then goes onto state, without a reference that “non-heme (plant) iron is better regulated causing less damage to the body”. Convenient that there is no reference for this wild claim biasing vegetarian foods over meats with some meaningless statement of being ‘better regulated’.
What does ‘better regulated’ even mean? She doesn’t explain. And she conveniently leaves out duck liver and black pudding, foods we’ll talk about later, in her ‘top 10’ highest iron foods list. Yet duck liver provides double the iron of the number 1 food on her list, even before we talk about absorption, as we’ll do later in the article.
Iron in the Vegan Diet
Another obviously biased article entitled Iron in the Vegan Diet irresponsibly touts spinach as not only a good source of iron, but one that is better than meat! A claim we will debunk with science instead of bias.
The author, Reed Mangels, whose education includes a PdH and Registered Dietitian after his name, quickly mentions the lowered bioavailability of spinach, and remarks that vegetarians and vegans might need as much as 1.8 times the amount of iron of non-vegetarians, but goes on to say that “Dried beans and dark green leafy vegetables are especially good sources of iron, even better on a per calorie basis than meat.”.
I don’t think we can take that any way other than meaning that beans and greens are unequivocally a better source of iron than meat! But he’s obviously not done his homework, and any small amount of research he might have bothered to do would have revealed his error. Since he’s a PhD, he should know better.
Spinach Does Have More Iron Than Meat…
Fact checking his statements is easy. We can just go to the Nutrition Data website of Self.com and compare ‘gram per gram’ the same nutrients in different foods. Here, for instance, are the comparisons for spinach and beef.
- Spinach 2.7 mg per 100 grams =23 calories
- Beef Brisket 1.9 mg /100 grams =127 calories
So, according to this, spinach definitely has more iron than beef on a per gram basis. So, how about on a per calorie basis. Here’s the math. I’ve made it per 100 calories just for ease of having larger round numbers
- Spinach has 11.7 mg/100 cal
- Beef Brisket 1.49 mg/100 cal
So far, he is right; gram per gram and calorie per calorie, spinach definitely has more iron than beef. In fact, it’s got several times more iron than beef… calorie per calorie. Score one for the vegetarians, right?
Not so fast, even those data may be very wrong. For instance, in the study Iron Deficiency it shows the following:
- Spinach 90 grams = 1.7 mg of iron that equals 1.8 mg/100 grams
- Ground beef 90 grams = 3 mg of iron that equals 3.3 mg/100 grams
- Calves liver 85 grams = 12 mg of iron that equals 14 mg/100 grams
So, the numbers for spinach for iron versus beef may not be correct for all beef products, and liver is known to be one of the richest sources of iron. Gram per gram in this study, beef liver has 9 times more iron than spinach. However, just to be fair, we’ll use the numbers that favor vegetables over meat. But first of all, we have to figure out how much 100 grams of spinach and meat is. Would someone actually eat these foods in those amounts? If not, the comparison is not fair.
No Beef with the Data on its Face
100 grams is about 3.5 ounces. That is about a typical serving of beef. In fact, a ‘quarter pounder’ is 4 ounces of meat. So, 100 grams is about the amount of a hamburger patty. But how much spinach is that? According to the same data, 100 grams of spinach is a bit over 3 cups of raw spinach. OK, so that is fairly equivalent. Most vegetarians would argue that they easily eat 3 cups of spinach in a salad. And if you cook it down, 3 cups comes out to a medium or large serving of spinach.
So, far, nothing is amiss. We will accept that spinach has more iron on both a gram for gram and calorie for calorie basis, and that 100 grams of spinach and 100 grams of beef are approximately a ‘serving size’. So far, we have no beef (pun intended) with the data of Dr. Mangels data… until we look at bioavailabilty.
Spinach for Iron is Difficult to Absorb
Bioavailability is what your body can actually absorb. It does no good to have a lot of a nutrient if your body can’t absorb it. There are two types of iron in nature:
- Heme iron that comes from animals
- Non-heme iron from plants
While iron is quite difficult to absorb anyway because of an elaborate feedback system, including a molecule produced by the liver called Hepcidin, it’s particularly difficult for the body to absorb iron from vegetables due to natural substances that decrease the absorption of non-heme iron, which is why diet is one of the top Causes of Iron Deficiency Anemia. Interestingly, these compounds do not affect the absorption of iron from meat, only plant-based iron. Two of these compounds present in spinach that decrease iron absorption from plants are:
- Oxalic Acid
Polyphenols are substances that we also know as ‘antioxidants’ found mostly in ‘colorful’ vegetables such as spinach, and are well-known to have many health benefits, including staving off cellular aging. While polyphenols are great for overall health, one thing they are NOT good for is iron absorption. Foods containing polyphenols are well-studied as inhibitors of iron absorption.
In fact, there are SO many foods that inhibit iron absorption that iron really should be taken on an empty stomach, unless you eat it with meat, which actually enhances iron absorption of non-heme iron 1. Not even coffee or tea should be taken with iron as the polyphenols they contain are potent inhibitors of iron absorption.
Spinach, unfortunately or fortunately, depending upon the reason you are eating it, has an extremely high polyphenol content 2. Oxalic acid is another substance in spinach that can decrease iron absorption 3 and lead to a variety of problems, such as kidney stones. Oxalic acid is what makes rhubarb leaves and some other plants deadly toxic to humans. Spinach obviously has a lesser amount of oxalic acid than rhubarb leaves, but the lower levels still can lead to harm to human health in larger amounts, including causing decreased absorption of nutrients like iron.
Fortunately, the oxalic acid in spinach can be diminished or even eliminated with proper cooking. Therefore, if you want to use spinach for iron, it should be cooked in water, and the water discarded in order to eliminate the oxalic acid 4. Unfortunately, cooking in water and discarding the water also reduces its Vitamin C content up to 90% 5, vitamin c increases the absorption of non-heme iron significantly!
Science Shows Major Absorption Problems with Spinach
The problem that we have with Dr. Mangels claims is not that he is incorrect about the iron content of spinach, but that he glosses over the reduced bioavailability of iron to the body from plants. In fact, you might need 10 times more ‘spinach iron’ as ‘meat iron’ because spinach for iron has one of the lowest rates of absorption in the vegetable kingdom. Only 1.4% of iron from spinach is absorbed, while 20% of iron from beef is absorbed.
“Although vegetables, particularly spinach, are regarded as impressive sources of iron, plant iron (non-heme iron) is relatively poorly absorbed. For instance, only 1.4% of the iron in spinach can be taken into the body. In contrast, 20% of iron from red meat (heme iron) can be absorbed”.
Iron Deficiency-scientific american
Is Spinach for Iron Really Better?
So, let’s do the math and see if spinach for iron is actually a better source of iron than meat, calorie per calorie, as the doctor claims. Again, here are the numbers for spinach and beef:
- Spinach has 11.7 mg/100 cal at 1.4% absorption= 0.16 mg/100 calories
- Beef Brisket 1.49 mg/100 cal at 20% absorption= 0.30 mg/100 calories
So, calorie per calorie, beef has about double the amount of absorbable iron, meaning that he’s just plain wrong. You just need to eat double the amount of spinach to get the same amount of iron, right? Nope. That is the problem with comparing spinach ‘calorie per calorie’. Remember the serving sizes we talked about above? Those were per 100 GRAMS, not 100 CALORIES. To get to 100 CALORIES, we have to quadruple the serving size of spinach that we talked about above.
As a result, to get half the amount of iron as beef, calorie per calorie, you are now eating 12 cups of spinach. To get the same amount of iron as in 100 grams of beef, you’d have to eat 24 cups of spinach! Now, I don’t know any vegetarians arguing that they eat 12 cups of spinach a day, let alone 24, and that will still only get you 0.3 mg of iron! This is beginning to be a problem. Now, lets go back to the 3 cup serving size. That has around 0.04 mg of absorbable iron per 100 grams, or per 3 cups. Be sure you pay attention to the decimal point there. That is 4/100ths of a gram of iron per serving. Spinach for iron is becoming a less attractive choice.
An additional reason that vulnerable populations such as vegetarians and vegans might have an even harder time absorbing iron is that it’s necessary to have sufficient vitamin D to keep hepcidin levels low and absorb iron properly (see the page on Why Doctors Keep African Americans Anemic). Since vegetarian diets are extremely low in vitamin D and vegan diets are virtually devoid of it entirely, these populations should consider getting regular vitamin D, iron, and ferritin levels to ensure that they are sufficient in these vital nutrients.
How Much Iron Do You Really Need?
So, how much iron do humans actually need each day? According to the US Government RDA, here are the daily needs of humans:
- Men and Postmenopausal women 8 mg
- Premenopausal women 18 mg
So, a man and a postmenopausal woman would need to eat 200, 3 cup servings, or 600 cups of spinach to meet their daily iron needs. A premenopausal women would need 450, 3 cup servings, or 1350 cups of spinach to meet her needs! Holy moly, no wonder vegetarians are often iron deficient. So, how good do you think vegetable sources of iron really are if vegetarians are touting spinach as a ‘rich’ source of iron, but you’d need 600 cups to meet your minimum daily requirements?
Can You Meet Your Needs Through Meat?
That doesn’t automatically mean that you can meet your iron needs through meat. To be fair, in order to meet the daily requirements in beef, you’d still need to eat either 26 servings, or 60 servings of beef to meet your needs, depending upon whether you are a male, or pre or post-menopausal female. Neither one of those sounds like a good option. One study noted this conundrum:
“Neither the meat diets nor the vegetarian diets fulfilled the
estimated daily requirements of absorbed iron in spite of a
meat intake of 180 g/d in the meat diets.”
Pork meat increases iron absorption when compared to a vegetarian diet
If you look at the stats up there again, I threw in calves liver as a comparison. Duck liver is an ever richer source of iron. Let’s look at those numbers on the Nutrition Data site again:
- Calves liver 6.5 mg/100 grams
at 20% absorption for heme iron, that is 1.3 mg per 100 grams. And who eats 100 grams of liver? Not many people, and certainly not every day. Although many of our ancestors, even one or two generations ago, had a weekly ‘liver and onions’ dinner, so may have got that much liver at least once a week. But a normal serving would probably be half of that, or about 0.65 mg or iron per serving. Not a great way to meet your iron needs either, it wouldn’t seem.
Fois Gras and Black Pudding? What the Heck?
But now, let’s take a look at duck liver. Maybe that will be better.
Duck liver 30.5 mg/100 grams
Hmm, now we might be onto something. But again, 100 grams of duck liver is probably not realistic. Half, or even less is more realistic for a serving. So, we’ll do the same math at 20% absorption for heme iron and we get: 6.1 mg of absorbable iron per 100 grams, or about 3 mg/ per 50 gram serving.
You would need 2 ½ servings of duck liver per day for a man or postmenopausal woman to meet her iron needs. Still probably not realistic either. Even the French, the world’s top consumers of duck and goose liver in the form of Fois Gras, only eat 300 grams of Fois Gras per YEAR per person.[cm_simple_footnote id=”1″] 6. Hardly enough to meet anyone’s daily needs.
Black pudding, another food not on Healthaliciousness’s list of high iron foods, has more than 18 mg of iron/100 grams, which also outstrips the number one food on their list, even before we account for bioavailability. Black pudding is also called blood pudding, and is a type of sausage made with meat and animal blood. It may sound exotic or crazy, but it is eaten commonly in Great Britain, Uruguay, Argentina and Brazil.
I personally LOVE blood sausage, and ate it regularly when I lived in Uruguay for 6 months. Blood sausage is not an uncommon meal at all, and it can still be easily found in the US if one goes to an Irish pub and orders an ‘Irish Breakfast’. In fact, just the other day, at a local butcher shop in what most would likely consider the ‘inner city’, I found several varieties of blood sausage and pork liver products. I even found it in gas station mini marts in the form of boudin in Louisiana.
Many other countries have similar foods, as using all of the parts of an animal, letting nothing go to waste, was a common practice throughout most of human history and still occurs in many cultures around the world. In fact, the Masai Tribesmen in Africa use cow’s blood mixed with milk as a dietary staple. Eating blood and organ meats is not an unusual practice in the world, and there was likely a good reason for it- getting sufficient iron.
When Being #1 is Not a Good Thing
The World Health Organization (WHO) classifies iron deficiency as the #1 nutritional deficiency worldwide, but it was almost certainly less so when the entire animal was eaten regularly. Even in the US, the numbers of premenopausal women with Iron Deficiency Anemia is estimated at between 10 and 20%.
Children, particularly from lower socioeconomic classes, are at particular risk of Symptoms of Iron Deficiency that include cognitive impairment and behavioral issues. The numbers of deficient run into the millions, just in the US alone, numbers which include vegetarians and vegans, who generally are not anemic, but that does not mean that they do not have Iron Poor Blood, a problem almost never diagnosed or treated.
In any case, in modern times, it seems that it’s difficult to meet one’s daily needs of iron, regardless of whether you eat meat or not. However, it’s obvious that spinach for iron, and most vegetables, are poor sources of this nutrient regardless of how this fact is spun in the vegetarian and vegan communities.
Even worse, vegan diets supply little Vitamin D, and Vitamin D helps to decrease Hepcidin and improve iron absorption. While it’s difficult for everyone to meet their iron needs, vegetarians and vegans put themselves at particular risk. Interestingly, you may have missed the study above that showed eating meat WITH vegetables actually increases the absorption of the non-heme iron in vegetables, making spinach for iron a better choice… when it’s eaten with meat.
Even worse, supplementation in the form of Iron Pills is not necessarily the answer, as the body’s feedback mechanism and many health issues common to western society, such as Increased Intestinal Permeability and infection with the H Pylori Bacteria, often prevent iron in supplements from being absorbed. Additionally, I’ve found one of the Best Iron Supplements, but most iron supplements are not absorbed well at all. It’s a conundrum without a good solution, regardless of your diet. Regardless of the conundrum, however, spinach for iron is going to shortchange your daily needs by a long shot.
- Pork meat increases iron absorption when compared to a vegetarian diet ↩
- Total antioxidant activity and phenolic content in selected vegetables ↩
- Total antioxidant activity and phenolic content in selected vegetables ↩
- Effects of cooking on the oxalate content of New Zealand Foods ↩
- Total antioxidant activity and phenolic content in selected vegetables ↩
- The market analysis of branded hungaricums ↩