Which has more iron, spinach or romaine lettuce? A Nutritional Comparison

December 20, 2025 •

4 min read

Raw spinach contains significantly more total iron than romaine lettuce per 100-gram serving. However, the answer to which has more iron, spinach or romaine lettuce? is more complex, as total iron content does not tell the whole story without considering absorption rates.

Quick Summary

Spinach holds more total iron per serving than romaine lettuce, but its absorption is inhibited by compounds like oxalates. Romaine has a lower total amount of iron, but its bioavailability is higher. How you prepare and consume these greens, especially with vitamin C, significantly impacts the amount of iron your body can utilize.

Key Points

Total Iron Content: Spinach contains significantly more total iron per 100 grams than romaine lettuce.
Iron Bioavailability: The iron in spinach (non-heme) is less readily absorbed by the body due to oxalates and polyphenols.
Romaine's Absorption Advantage: Romaine lettuce has fewer absorption inhibitors, meaning its smaller amount of iron is more readily available to the body.
Boost Absorption with Vitamin C: Pairing leafy greens with a source of vitamin C, like bell peppers or citrus, can dramatically increase iron absorption.
Cooked vs. Raw: Cooking spinach reduces its oxalate content and concentrates nutrients, increasing the iron available per cup compared to raw spinach.
Varied Diet is Best: The most effective strategy for iron intake is to incorporate a variety of plant-based and, if applicable, animal-based iron sources, rather than relying on one leafy green.
Beyond Iron: Both greens offer additional nutritional benefits; spinach is rich in Vitamin K and folate, while romaine provides ample Vitamin A and fiber.

Total Iron Content: The Initial Comparison

At first glance, the data from food composition databases shows a clear winner when it comes to total iron content. While the exact numbers can vary based on growing conditions and maturity, general figures indicate that spinach has a higher concentration of iron by weight compared to romaine lettuce. For instance, raw spinach typically contains 2.1 to 3.2 mg of iron per 100 grams, whereas raw romaine lettuce offers around 0.9 to 1.0 mg for the same weight. This difference is even more pronounced when the vegetables are cooked. As spinach wilts, its volume decreases significantly, concentrating the nutrients. A cup of cooked spinach can have more than six times the amount of iron as a cup of raw spinach.

The Crucial Factor: Bioavailability and Absorption

While total iron content is important, it is not the sole determinant of how much iron your body actually receives. This is where the concept of bioavailability comes in. Iron from plant sources (non-heme iron) is much less readily absorbed by the human body than iron from animal sources (heme iron).

Inhibitors of Iron Absorption in Spinach

Spinach contains high levels of compounds called oxalates and polyphenols, which are known to inhibit the absorption of non-heme iron.

Oxalates: These naturally occurring compounds bind to minerals like iron and calcium, forming insoluble compounds that the body cannot easily absorb. While cooking can reduce the oxalate content, it does not eliminate it entirely.
Polyphenols: Some studies also suggest that polyphenols present in spinach can bind to iron and further reduce its bioavailability.

The Romaine Advantage

Romaine lettuce, while lower in total iron, does not contain the same high levels of oxalates and polyphenols that hinder absorption in spinach. This means that a higher percentage of the iron in romaine lettuce may be absorbed by the body, even if the total amount is less. It's a key distinction that frames the nutritional debate beyond simple iron quantity.

Maximizing Iron Intake from Leafy Greens

To get the most iron out of your salad greens, consider these strategies:

Pair with Vitamin C-rich Foods

Adding a source of vitamin C, such as citrus fruits (oranges, lemon juice), strawberries, or bell peppers, to your salad can significantly enhance the absorption of non-heme iron from both spinach and romaine.

Incorporate Cooked Spinach

As previously mentioned, cooking spinach reduces its volume, allowing for a higher concentration of iron per serving. It also helps to reduce the oxalate content, improving absorption.

Avoid Calcium and Iron Together

Calcium can inhibit the absorption of both heme and non-heme iron. Try to avoid consuming high-calcium foods like milk or cheese at the same time as your iron-rich greens. For example, have your salad with a vitamin C-rich dressing, and enjoy your yogurt or dairy later in the day.

Beyond Iron: A Broader Nutritional View

While iron is the focus of this comparison, it is worth noting that both spinach and romaine lettuce are excellent sources of other nutrients. Mixing them in your diet is a great way to ensure a wide range of vitamins and minerals. Here is a broader nutritional look:

Spinach

Vitamins: Very high in Vitamin K, Folate, and Vitamin C.
Minerals: Good source of magnesium and potassium, in addition to iron.

Romaine Lettuce

Vitamins: Rich in Vitamin A and Vitamin K.
Other Benefits: High water content and good source of fiber, which supports digestion.

Spinach vs. Romaine Lettuce: A Comparison Table


Feature	Spinach (Raw per 100g)	Romaine Lettuce (Raw per 100g)
Total Iron Content	~2.7-3.2 mg	~0.9-1.0 mg
Bioavailability of Iron	Lower (inhibited by oxalates/polyphenols)	Higher (minimal absorption inhibitors)
Best with Vitamin C?	Yes, significantly enhances absorption	Yes, improves overall iron uptake
Concentrates When Cooked?	Yes, iron content increases by volume	No, less suitable for cooking down
Other Noteworthy Nutrients	Vitamin K, Folate, Vitamin C	Vitamin A, Vitamin K, Fiber

The Final Verdict: It’s More Than Just a Number

Ultimately, the question of which has more iron, spinach or romaine lettuce?, isn't just about total milligrams. Spinach contains more iron, but the crucial bioavailability factor and the inhibiting oxalates mean your body absorbs only a small portion of it. Romaine lettuce, while lower in total iron, provides a more accessible iron source without the same level of absorption hindrance.

For optimal nutrient intake, combining your greens or rotating between them is the best strategy. Enjoy a spinach salad with strawberries and a lemon vinaigrette to boost absorption, and on another day, opt for a crisp romaine salad. The true goal should be to include a variety of nutrient-rich foods in your diet to ensure your body gets all the benefits it needs. For more comprehensive information on iron and other essential nutrients, consult authoritative sources like the National Institutes of Health.

Conclusion: A Balanced Perspective on Leafy Green Iron

When choosing between spinach and romaine for your iron intake, remember that quantity isn't everything. While spinach boasts a higher overall iron count, romaine offers greater bioavailability. By understanding the roles of oxalates and vitamin C, you can strategically prepare and combine these foods to maximize your body's absorption. Both greens provide valuable nutrients, and the best approach is to enjoy them both as part of a varied and healthy diet, rather than relying solely on one over the other for your iron needs.

Frequently Asked Questions

No, the iron in spinach is not useless, but its absorption is significantly reduced due to oxalates and other compounds. Your body can still absorb some of it, and you can increase absorption by pairing spinach with vitamin C-rich foods.

No, cooking does not destroy the iron in spinach. In fact, by wilting the leaves, it concentrates the iron, meaning a cup of cooked spinach has significantly more iron than a cup of raw spinach.

To maximize iron absorption, add a vitamin C source like orange segments, strawberries, or a lemon juice vinaigrette to your spinach salad. You should also avoid eating it with high-calcium foods, which can hinder iron uptake.

Romaine lettuce is not considered a high source of iron, but it does contribute to your daily intake with better bioavailability than spinach. It is a good source of other nutrients, particularly Vitamins A and K.

Besides leafy greens, other excellent plant-based iron sources include lentils, beans, tofu, chickpeas, and fortified cereals.

Heme iron, found in animal products, is more easily absorbed by the body. Non-heme iron, found in plants, is less bioavailable. However, both are important for a balanced diet.

No, the Popeye myth is based on a debunked error from the early 20th century. The cartoon's creator actually emphasized spinach's high vitamin A content, not its iron.