The Iron Lie We’ve Been Told Since Childhood

In the late 1800s, a German scientist analysing spinach’s iron content reportedly misplaced a decimal point, accidentally inflating spinach’s iron numbers. 

That tiny error became a giant nutrition myth. 

Then came Popeye, the sailor man that we all know. 

A can of spinach, and suddenly, a burst of strength that even made the love of his life admire him more. 

See, that psychology was so powerful. The lie was repeated, and playing on people’s primal instincts worked so well that it became the truth of the world: 

Spinach is NATURE’S IRON SUPPLEMENT. 

BUT HERE IS THE BREAKDOWN OF THE SCIENCE 

I would love to teach India two things: 

Absorption and Bioavailability. 

Most supplement brands, nutritionists, etc., use these as synonymous words as if one can be interchanged with the other. 

THEY ARE NOT. 

I can give you a whole PubMed explanation, but you probably wouldn’t understand it (honestly, I wouldn’t either). 

But here is a very simple breakdown: 

Absorption is when nutrients from food in the gut manage to surpass the gut wall and enter the bloodstream. 

Bioavailability is when the nutrient enters the bloodstream in an active form, ready to be used wherever the body needs it. 

Absorption is the first step, but the goal is bioavailability. 

Simplest explanation, but maybe next time I’ll write a blog about this because the science behind this is complex and fascinating on its own. 

But what you need to take away from this is: 

You need to see not which food is high in iron, but which foods are high in bioavailable iron. 

Also, No One Knows That Iron Has Two Personalities 

Iron doesn’t exist in one universal form. 

There are two types: 

1. Heme Iron: The Easy Passenger 

Heme iron is the form of iron found naturally in animal foods, where it is bound within haem, the iron-containing molecule that carries oxygen in haemoglobin and myoglobin. 

This makes it easier for the body to recognise and absorb. 

Found in: 

Around 15–35% can be absorbed. 

2. Non-Heme Iron: The Difficult Passenger 

Non-heme iron is the form of iron found in plants and fortified foods. 

Unlike heme iron, it is not bound to haem, the oxygen-carrying molecule found in animal tissues. 

Found in: 

Plant foods: 

Fortified foods: 

Typical absorption ranges from 2-20%, depending on several factors. 

The Hidden Iron Blockers Sitting On Your Plate 

BLOCKER 1: Phytates (Phytic Acid) 

Phytates are the storage form of phosphorus in plants. 

They are found mainly in: 

Did you know spinach is high in phytates? But how does it affect iron? 

Phytates have multiple negatively charged phosphate groups. 

Iron (especially Fe²⁺ and Fe³⁺) carries a positive charge. 

The opposite charges attract each other, allowing phytate to bind iron tightly, forming an insoluble complex. 

This complex cannot interact with the iron transporter (DMT1) on intestinal cells. 

BLOCKER 2: Oxalates (Oxalic Acid) 

Oxalates are naturally occurring organic acids produced by many plants. 

Foods high in oxalates include: 

Oxalates can bind minerals, including iron, but their effect on iron absorption is much weaker than phytates. 

Polyphenols 

Polyphenols are a large family of antioxidant compounds. 

Sounds great, but when it comes to iron absorption, polyphenols can chemically bind non-heme iron in the gut, forming complexes that remain poorly soluble. 

Sources include: 

Drinking black tea with a meal can reduce non-heme iron absorption by 60–90%, depending on the amount consumed. 

Good, if you have reached this far, that means you can officially understand iron as well as a nutritionist. 

And just in case you need it, here’s a cheat sheet of high-iron foods both heme and non-heme and their bioavailability.