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1 iron truth: lentils vs. beef
Ironclad arguments
Kos Zharoid
April 16, 2025
You’re not iron deficient because you don’t eat enough of it.
You’re iron deficient because your salad is gaslighting you.
It says it’s packed with iron, but it comes bundled with compounds that slap that iron into handcuffs before your body can even say “thank you.”
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Iron in foods.
We often hear bold statements like "lentils contain twice as much iron as beef." It's especially strange to hear this from nutritionists and doctors. Let's get the facts straight.
Remember, considering the average iron absorption rate, the recommended daily iron intake is 15-18 mg for women (with menstruation) and 10-12 mg for men.
First, 3.5 oz of dry lentils contains 7 mg of non-heme iron, and when cooked, it makes about an 8.8 oz portion.
Second, your body absorbs only 2% of iron from lentils. This means from an 8.8 oz portion, you get only 0.14 mg of iron! If we do the math, you must eat 7.7 pounds of cooked lentils to meet your daily requirement.
From leafy green vegetables (like spinach, which people often use as an example), you absorb 7-9% of iron, and from grains, about 4%. However, you absorb much more from animal products (heme iron) – up to 25-30%.
Third, vitamin C, phytates, oxalic acid, polyphenols, and other anti-nutrients don't affect heme iron absorption (70% of all iron in animal products). Even stomach acidity affects it much less, especially if you eat something like pâté or marinated meat. However, these factors significantly impact plant iron absorption, which is why smart vegans constantly soak foods and create specific combinations to increase absorption.
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Why such a difference in absorption?
Because the absorption pathways differ completely from start to finish.
Iron is a very reactive element and doesn't exist in food in its free state, but is bound to various compounds. Iron binds to heme in animal products as part of hemoglobin or myoglobin. This is divalent iron that doesn't need ionization or jumping through hoops. Look at the picture – these red envelopes are heme.
Heme enters the enterocyte (intestinal cell) intact through a specific protein or endocytosis (when the cell swallows it). Inside the cell, the enzyme heme oxygenase releases the iron, which then gets packaged into ferritin or used by the body. Nothing tries to grab it along the way. It essentially has a green light for absorption.
Non-heme iron from plants is trivalent and must first go through a long journey: it must break free from plant complexes in the acidic stomach environment. Here, many compounds try to capture it because trivalent iron is reactive and can form insoluble complexes with phytates, oxalic acid, polyphenols, and others.
That's why most iron from plant sources ends up in the toilet. What remains must be reduced to Fe2+ by stomach acid or vitamin C. Only then can it enter the intestinal cell with the help of the DMT1 transporter (a transporter for divalent metals). This is "public transportation," and other divalent elements want to ride it too, creating competition. From there, the iron meets the body's needs, and the excess gets stored.
Your diet should include different iron sources, both plant and animal. Considering the prevalence of anemia and iron deficiency in women and children in the US (10% of women have iron deficiency), becoming vegan or carnivorous isn't rational. People always need a balance.
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It's important to understand that iron is a heavy metal, and excess amounts are difficult to eliminate. Therefore, your body strictly regulates iron absorption based on your iron status. Absorption increases in the intestine when you lack dietary iron or have increased needs, and decreases when you have plenty of iron in your diet.
So don't assume absorption always remains the same. The activity of DMT1, which transports reduced non-heme iron through the enterocyte membrane, varies. With a normal diet, your body regulates how much iron to absorb.
Additionally, your body doesn't waste resources. Most of the iron you use comes from recycling iron from your own destroyed red blood cells, which lived for 180 days before breaking down. Still, you lose 1-2 mg daily, which you need to replenish.
So why does the dietary iron recommendation for women stand at 15-18 mg, not 1-2 mg?
The RDI calculations assume a mixed diet with an average absorption rate of about 15% across all animal and plant sources. For example, if non-heme iron absorbs at 4% and heme iron at 26%, the average is 15%. So, you need to consume about 15-18 mg of iron to absorb those 2 mg.
Remember! All numbers are approximate, and all norms are averages. Eliminating phytates completely is a bad idea because they act as powerful anti-cancer substances, especially when combined with propionate (a fatty acid produced by gut bacteria). Focusing only on heme iron is also a bad idea.
Don't eat liver every day. If your dietary iron intake is adequate but still has iron deficiency anemia, look for another cause. Also, remember that B6, zinc, and iron participate in heme synthesis. Copper, iron, and vitamin C help with absorption, while copper aids transport, and vitamins B2, B3, B9, and B12 support blood cell maturation. So iron isn't the only important nutrient.
Eating iron-rich foods and absorbing iron are two different things. Heme iron has better bioavailability – that's a fact – but non-heme iron isn't bad. Many factors and the composition of your meal affect its absorption.
You should know these differences because they make life easier and help you understand that the rules for non-heme iron absorption don't apply to heme iron. If you ignore these rules, you might develop dietary iron deficiency despite having an "ideal" food list.
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Warm regards,
Kos and Helen.
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