Executive Summary
Spinach has a decent amount of iron. But less than two per cent of it can be absorbed by our bodies because compounds called oxalates in spinach prevent its absorption. Consuming spinach with vitamin C (citrus fruits, green vegetables) or fermented foods, soaking spinach in hot water for 10-15 minutes are some ways to increase its iron absorption.
Spinach is often recommended by doctors and dietitians as a great source of iron to counteract its deficiency. However, the science tells us that it is a wrong advice.
The Scam About Iron in Spinach
First, the scam. Most experts have been taken for a ride about the iron contents of spinach by a 150-year-old swindle.
In 1870, a German scientist, Dr Erich von Wolf, was studying the nutritional benefits of spinach. He noted down the amount of its iron content as ten times the actual amount—27 mg of iron instead of 2.7 mg in 100 g of spinach. Overnight, spinach became the best source of iron, even better than chicken liver, which contains humongous amount of iron at 11 mg/100 g.
Some charitable people think that it was a mistake. But most likely, it was a scam. How is it possible that no one questioned such an outlier value for decades? Most probably, some spinach producer or trader was behind it. But then, we digress.
Somehow, this swindle went on for another fifty years. Enter the 1920s. The World War I was over. The United States of America was going through its first national nutrition crisis: child malnutrition. The medical authorities in the U.S.A. were wondering how to address the lack of iron and resultant anemia. Then, they found an ideal candidate: Popeye.
Popeye and the Spinach Iron Myth
In the 1930s, the cartoonist Max Fleischer created Popeye, a fictitious character. Fleischer showed Popeye as a sailor who gained strength by eating spinach. The government medical authorities latched on to Popeye to promote the consumption of spinach. They spread the word that Popeye got his strength from the iron in spinach that he ate. Kids and their gullible parents took the bait. They started to eat bitter spinach dishes because their hero Popeye was eating it. Soon, spinach consumption spurted by thirty-three per cent.
In reality, the comic strip had claimed that Popeye’s strength came from vitamin A in spinach and not iron. But no one was ready to listen. Spinach and its iron were all the craze.
When something attracts such attention, vested interests dig deeper. Soon, scientists started studying the spinach contents once again. They found Dr Wolf’s error or fraud in 1937. But by then, it was too late. Everyone was already convinced that spinach was the best source of iron. It was a prime example of popular culture shaping scientific beliefs.
The misconception has stayed on for nearly a century. Even today, many doctors and dietitians believe that spinach is a fantastic source of iron. How ironic! (pun intended)
So what exactly does science say about this?
Is Spinach a Good Source of Iron?
This is a deceptive question. One should actually ask two separate questions:
- Does spinach have enough iron? Answer: Yes.
- Can you get enough iron from spinach? Answer: No.
Let us look at them one by one.
Does Spinach Have Enough Iron?
For starters, what is ‘enough’ iron? Nutritional science has rules to define that.
Labeling a Source of Iron
For any food to be called a ‘source of iron’, it needs to have at least fifteen per cent of the daily recommended allowance (RDA) of iron in hundred grams of the food. And for a food to be classified as ‘high in iron’, it needs thirty per cent of iron RDA in the same hundred grams.
The iron RDA for adults under the age of fifty years is 8 mg for men, 18 mg for women, and 27 mg in pregnancy.
Let us take 18 mg for calculation since spinach is commonly recommended for women to avoid deficiency of iron. So we will evaluate if spinach is a good source of iron for non-pregnant women.
15% x 18 mg = 2.7 mg
So hundred grams of any food needs to have 2.7 mg of iron for the food to be called a source of iron and 5.4 mg to be called high in iron (for non-pregnant women). Spinach with its 2.7 mg of iron in 100 g barely qualifies to be called a source of iron for such women.
There is another problem with spinach: it has non-heme iron.
Heme versus Non-Heme Iron in Foods
Iron in food is of two types:
- Heme iron, which is found only in animal products. Between fifteen and thirty per cent of it is absorbed in the body; and
- Non-heme iron, which is common in plant products. It is absorbed between two to twenty percent. This is the type of iron that spinach has.
Why is the absorption percentage lower for plant products or vegetarian sources? It is because the iron in them is bound strongly to plant compounds called phytates and tannins, which reduces its absorption.
Can You Get Enough Iron from Spinach?
Unfortunately, when authorities label a food as a ‘source of iron’, they do not take its absorption percentage into account. So two foods may have the same amount of iron but one of them may provide much less iron than the other. Spinach with its poor absorption of iron is the former kind. But wait; it gets worse for spinach.
Spinach has compounds called oxalates that bind very strongly to iron. As a result, the absorption of iron from spinach is even lower than its green leafy vegetable colleagues—as low as two per cent.
As it is jokingly said, you can get more iron from the small dirt particles clinging to the spinach plant rather than from the plant itself.
Increasing Absorption of Iron from Spinach
But there is some hope. There are nutrients that increase absorption of non-heme iron. For example, vitamin C (you can get it from citrus fruits and green leafy vegetables), fermented foods and even alcohol. If spinach is consumed along with them, more iron is absorbed. But don’t use that as an excuse to down a peg of your single malt when eating spinach.
Another option is to soak spinach in hot water for 15 to 20 minutes. That reduces its oxalates by fifty per cent, helping increase eventual absorption of iron.
Interestingly, soy protein increases the absorption of heme iron but reduces that of non-heme iron. Life is strange! So it is not good to consume soy protein with plant sources of iron.
Similarly, calcium and tannins (in tea) reduce the absorption of iron. Avoid consuming them with spinach. In that sense, the famous Indian dish, Palak Paneer, is a disaster. Spinach has iron and paneer, the Indian cottage cheese, has calcium.
Luckily, spinach is packed with many nutrients besides iron. So even though you get very little iron from it, consider consuming a cupful or about seventy-five grams of cooked spinach on a regular basis.
Maybe, Popeye knew that the only way to get iron from a can of spinach was to eat the can itself.
Hundreds of such health-related tips will be covered in my new book that will be published in August 2023 by Macmillan Publishers. The book will discuss twenty super-foods such as tomatoes, garlic and ginger, their nutrients, medicinal benefits, required amounts and who should avoid them.
To Read More
- On this website: Nutrients That Work Together
- On this website: Recommended Dietary Intakes of Various Nutrients
- On this website: Supplements for anemia
First published on: 1st January 2023
Image credit: Karolina Grabowska from Pixabay
Last updated on: 2nd January 2023