- Doctors and dietitians recommend spinach as a great source of iron. But, science tells us that it is the wrong advice.
- Spinach has a decent amount of iron, but our bodies absorb less than two per cent of it.
- To increase iron absorption:
• Consume spinach with vitamin C (citrus fruits, green leafy vegetables) or fermented foods, or
• Soak it in hot water for ten to fifteen minutes.
The Scam About Iron in Spinach
First, the scam. A 150-year-old swindle about the iron contents of spinach has taken most experts for a ride.
In 1870, a German scientist, Dr Erich von Wolf, studied the nutritional benefits of spinach. He noted down that hundred grams of spinach contain 27 mg of iron, instead of 2.7 mg. Overnight, spinach became the best source of iron. Compare it with chicken liver, which contains 11 mg per hundred grams—a humongous amount.
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? Perhaps, 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 a child malnutrition crisis. The medical authorities in the U.S.A. were wondering how to address the lack of iron and resultant anaemia. 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 spinach consumption. 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 almost 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 as a percentage of the Daily Value (DV) of a nutrient. DV is the recommended amount of a nutrient to consume each day. When a nutrient has a recommended dietary allowance (RDA) determine, its DV is equal to its RDA.
The iron RDA (and DV) for adults under the age of fifty years is 8 mg for men, 18 mg for women, and 27 mg during pregnancy.
What is a Poor or High Source of Iron?
Note the 5/20 rule. If a serving of a food item has less than 5% DV of a nutrient, the food is a poor source of that nutrient. If the serving has more than 20% of nutrient DV, the food has a high amount of that nutrient.
We will take 18 mg for calculation since spinach is recommended for women to avoid iron deficiency.
5% x 18 mg = 0.9 mg
So any food needs to have 0.9 mg of iron in its one serving for it to be an iron source and 3.6 mg to be high in iron.
A serving of spinach is 75 grams, which has 2 mg of iron. So it is a source of iron for such women.
Then, there is another problem with spinach: it has non-heme iron.
Heme Iron versus Non-Heme Iron
Iron in food is of two types:
- Heme iron, which is found only in animal products. The body absorbs between fifteen and thirty per cent of it; and
- Non-heme iron, which is common in plant products. The body absorbs between two to twenty per cent. Spinach has this type of iron.
Why is the absorption percentage lower for plant products or vegetarian sources? Non-heme iron is bound strongly to plant compounds called phytates and tannins, which reduces its absorption.
Can You Get Enough Iron from Spinach?
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 tightly to iron. So the iron absorption from spinach is even lower than its green leafy vegetable colleagues—as low as two per cent.
New research shows that iron absorption from spinach is poor because of its polyphenols and not oxalates. Either way, we get too little iron from spinach.
As it is said in jest, you can get more iron from the small dirt particles clinging to the spinach plant rather than from the plant itself.
How to Increase Iron Absorption from Spinach
But there is some hope. There are nutrients that increase the absorption of non-heme iron. For example, vitamin C (citrus fruits and green leafy vegetables), fermented foods and even alcohol. If you consume spinach along with them, more iron is absorbed. But don’t use that as an excuse to down a peg of single malt when eating spinach.
Another option is to soak spinach in hot water for fifteen to twenty minutes. That reduces its oxalates by fifty per cent, increasing iron absorption.
Calcium and tannins reduce iron absorption. Avoid consuming spinach with milk products and tea. The famous Indian dish, Palak Paneer, is a nutrition disaster. Spinach has iron and paneer–the Indian cottage cheese–has calcium.
Interestingly, soy protein increases heme iron absorption but reduces that of non-heme iron. Life is strange! So it is not good to consume soy protein with plant sources of iron.
Luckily, spinach is full of many nutrients besides iron. Consume 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.
Most of the information in this article is taken from my upcoming book to be published by Macmillan Publishers in Nov 2023. The book discusses a thousand such preventive health tidbits. It covers twenty superfoods, their nutrients, health benefits, recommended amounts and excess levels. It also explains how to select and store and who should avoid them. Some of the superfoods are tomatoes, coconut, capsicum (Shimla mirch), drumsticks, amla (Indian gooseberry), jamun (Java plum), turmeric, cinnamon, flax seeds, asafoetida (hing), and sabja (sweet basil seeds).
To Read More
- Compound Interest: The chemistry of spinach: the iron myth and ‘spinach teeth’
- 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: 21st July 2023